Distribution by Scientific Domains
Distribution within Life Sciences

Terms modified by Motile

  • motile cell
  • motile cilium
  • motile sperm
  • motile spermatozoa

  • Selected Abstracts

    Changes in faecal bacteria associated with concentrate and forage-only diets fed to horses in training

    Summary Reasons for performing study: Diets rich in readily fermentable carbohydrates, fed traditionally to meet the increased energy requirements of the performance horse, are associated with a number of gastrointestinal disorders that involve disturbances in the intestinal microbiota, however, these changes are poorly understood. Objectives: With the long-term objective of improving intestinal health and to increase understanding of the relationship between diet and microbiota, the effect of feeding Standardbred horses a high-energy forage-only (F) diet was studied compared to a more traditional forage-concentrate (C) diet on faecal microbiota. Methods: Diets were fed in a cross-over design to 6 mature geldings on a scheduled training regime, both periods consisting of 29 days. DNA was extracted from faecal samples collected at 4 time points from each period, bacterial 16S rRNA genes were amplified and community composition assessed by terminal-restriction fragment length polymorphism, cloning and sequencing. Faecal pH and cultivable lactic acid bacteria (LAB) and enterobacteria were also assessed on the final collection day of each period. Results: Diet F resulted in a microbial composition that was more stable between sampling periods and had lower counts (P<0.05) of cultivable LAB and specifically members of the Streptococcus bovis/equinus complex. Motile and swarming Lactobacillus ruminis was present in all horses on diet C and not in horses on diet F. Diet C also resulted in the increase (P<0.05) in members of Clostridiaceae cluster III and a concomitant reduction (P<0.05) in an unknown group of Bacteroidales. Conclusions and potential relevance: The greater microbial stability and reduction in LAB and members of the Streptococcus bovis/equinus complex on diet F indicate an opportunity to develop feeding strategies that support equine health and welfare. Novel changes identified in the faecal microbiota that resulted from carbohydrate inclusion merit further investigation. [source]

    Another diet of worms: the applicability of polychaete feeding guilds as a useful conceptual framework and biological variable

    MARINE ECOLOGY, Issue 3-4 2005
    Paulo Roberto Pagliosa
    Abstract A fundamental question in guild studies is how to separate species into guilds. In a seminal manuscript, Fauchald & Jumars [Oceanography and Marine Biology Annual Review17 (1979) 193] summarized polychaete feeding biology and proposed a conceptual framework to test hypotheses on the sympatric occurrence of congeners with limited morphological differentiation. Twenty-six years after this publication, few studies have tested the validity and practical functioning of this scheme of polychaete feeding guilds and then only using part of the classification. The objective of the present study was to analyze the applicability of polychaete feeding guilds to ecological and environment assessments. Two data sets from Santa Catarina Island Bay, southern Brazil, were used. The first data set deals with spatial distribution of natural polychaete assemblages along the bay. The second data set treats fauna in urbanized versus relatively pristine mangroves. Multivariate analysis showed similar patterns in sample groups formed using guilds or densities and composition data. The role of feeding guilds in benthic systems was assessed through comparison with environmental variables. The polychaete assemblage from the Bay was related to sediment type. Motile and discretely motile carnivores and herbivores with jawed probosces matched coarse sands; surface deposit feeders and filter feeders were found in fine sands; and surface and subsurface deposit feeders and carnivores, all with soft probosces matched silt and clay sediments. The data analyses in mangroves showed surface deposit feeders and filter feeders in undisturbed sites and omnivorous species in disturbed ones. The polychaete feeding guilds appear relevant to assembly rules based on resource availability, to resource partitioning and to interspecific competition. [source]

    Effects of hydrostatic pressure, agitation and CO2 stress on Phytophthora nicotianae zoospore survival

    Monday O Ahonsi
    Abstract BACKGROUND:Phytophthora nicotianae Breda de Haan is a common pathogen of ornamental plants in recycled irrigation systems. In a previous study, annual vinca (Catharanthus roseus Don) inoculated with zoospore suspensions using a CO2 -pressurized sprayer had less foliage blight than plants inoculated using a hand sprayer. Here, the impact of hydrostatic pressure, agitation and aeration with CO2 on the survival of P. nicotianae zoospores was examined. RESULTS: Exposure of zoospores to 840 kPa hydrostatic pressure for 8 min or agitation at a mixing intensity (G) of 6483 s,1 for 4 min at 22,23 C did not kill zoospores, but resulted in viable cysts. Motile and forcefully encysted zoospores of P. nicotianae were equally infectious on vinca or lupine (Lupinus polyphylus Lindl.). Bubbling CO2 into zoospore-infested water at 110.4 mL (0.2 g) min,1 for 5 min caused 81% reduction in the number of germinated zoospores. Pressure at 630 kPa (16.3 g CO2) or 70 kPa (3.85 g CO2) facilitated CO2 injection and shortened the zoospore inactivation time to 30 s. When air was bubbled through the suspension, germination was similar to the control. CONCLUSIONS: Exposure to CO2 killed P. nicotianae zoospores in water. Neither pressure nor agitation had an effect on zoospore viability or infectivity. Based on results of this study, the authors designed a recycling CO2 water treatment system that is currently under evaluation. Copyright 2010 Society of Chemical Industry [source]

    Molecular characterization of the effects of Y-27632

    CYTOSKELETON, Issue 2 2007
    Hassina Darenfed
    Abstract Many key cellular functions, such as cell motility and cellular differentiation are mediated by Rho-associated protein kinases (ROCKs). Numerous studies have been conducted to examine the ROCK signal transduction pathways involved in these motile and contractile events with the aid of pharmacological inhibitors such as Y-27632. However the molecular mechanism of action of Y-27632 has not been fully defined. To assess the relative contribution of these Rho effectors to the effects of Y-27632, we compared the cytoskeletal phenotype, wound healing and neurite outgrowth in cells treated with Y-27632 or subjected to knockdown with ROCK-I, ROCK-II or PRK-2- specific siRNAs. Reduction of ROCK-I enhances the formation of thin actin-rich membrane extensions, a phenotype that closely resembles the effect of Y-27632. Knockdown of ROCK II or PRK-2, leads to the formation of disc-like extenstions and thick actin bundles, respectively. The effect of ROCK-I knockdown also mimicked the effect of Y-27632 on wound closer rates. ROCK-I knockdown and Y-27632 enhanced wound closure rates, while ROCK-II and PRK-2 were not appreciably different from control cells. In neurite outgrowth assays, knockdown of ROCK-I, ROCK-II or PRK-2 enhances neurite lengths, however no individual knockdown stimulated neurite outgrowth as robustly as Y-27632. We conclude that several kinases contribute to the global effect of Y-27632 on cellular responses. Cell Motil. Cytoskeleton 2006. 2006 Wiley-Liss, Inc. [source]

    Cryopreservable neutrophil surrogates: Granule-poor, motile cytoplasts from polymorphonuclear leukocytes home to inflammatory lesions in vivo

    CYTOSKELETON, Issue 5 2006
    Stephen E. Malawista
    Abstract Cytokineplasts (CKP) are anucleate, motile, granule-poor fragments induced from polymorphonuclear leukocytes on surfaces by the brief application of heat. Derived from the peripheral cytoplasm and membranes of PMN, they retain the sensing, transducing, and effector mechanisms necessary for chemotaxis and phagocytosis, and appear to represent a functional, self-purification of the motile apparatus. Unlike their parent PMN, CKP are cryopreservable. We have shown that they can adhere to endothelial cell monolayers, open interendothelial cell junctions, and migrate to the abluminal side when stimulated by a chemoattractant. Employing an animal model, we now show that, given intravenously, they can home to an inflammatory target lesion in vivo. Cell Motil. Cytoskeleton 2006. 2006 Wiley-Liss, Inc. [source]

    Further studies on knockout mice lacking a functional dynein heavy chain (MDHC7).

    CYTOSKELETON, Issue 2 2005

    Abstract Male mice had been previously generated in which the inner dynein arm heavy chain 7 gene (MDHC7) was disrupted. MDHC7,/, animals show asthenozoospermia and are sterile. Very few of their spermatozoa can achieve forward progression, but for those that can, we add here the information (1) that the three-dimensional aspects of their movement are normal; (2) that their maximum velocity is less than that of wild-type controls; and (3) that they are entirely unable to penetrate media of raised viscosity (25,4,000 cP). However, the large majority of the spermatozoa can achieve only a low amplitude vibration. In these sperm we find, using electron microscopy, that the outer dense fibres retain attachments to the inner surface of the mitochondria. Such attachments are present in normal epididymal mouse spermatozoa but are broken down as soon as the sperm become motile on release from the epididymis. The attachments are presumed to be essential during midpiece development and, afterwards, to require a threshold level of force to loosen them and so permit the sliding displacements necessary for normal bending. We presume that the disruption of the inner dynein arm heavy chain gene, MDHC7, means that there is insufficient force to overcome the attachments, for all but a few spermatozoa. Cell Motil. Cytoskeleton 61:74,82, 2005. 2005 Wiley-Liss, Inc. [source]

    Analysis of human muscle stem cells reveals a differentiation-resistant progenitor cell population expressing Pax7 capable of self-renewal

    Bradley Pawlikowski
    Abstract Studies using mouse models have established a critical role for resident satellite stem cells in skeletal muscle development and regeneration, but little is known about this paradigm in human muscle. Here, using human muscle stem cells, we address their lineage progression, differentiation, migration, and self-renewal. Isolated human satellite cells expressed ,7-integrin and other definitive muscle markers, were highly motile on laminin substrates and could undergo efficient myotube differentiation and myofibrillogenesis. However, only a subpopulation of the myoblasts expressed Pax7 and displayed a variable lineage progression as measured by desmin and MyoD expression. Analysis identified a differentiation-resistant progenitor cell population that was Pax7+/desmin, and capable of self-renewal. This study extends our understanding of the role of Pax7 in regulating human satellite stem cell differentiation and self-renewal. Developmental Dynamics 238:138,149, 2009. 2008 Wiley-Liss, Inc. [source]

    Mechanical computation in neurons

    Jummi Laishram
    Abstract Growth cones are the main motile structures located at the tip of neurites and are composed of a lamellipodium from which thin filopodia emerge. In this article, we analyzed the kinetics and dynamics of growth cones with the aim to understand two major issues: first, the strategy used by filopodia and lamellipodia during their exploration and navigation; second, what kind of mechanical problems neurons need to solve during their operation. In the developing nervous system and in the adult brain, neurons constantly need to solve mechanical problems. Growth cones must decide how to explore the environment and in which direction to grow; they also need to establish the appropriate contacts, to avoid obstacles and to determine how much force to exert. Here, we show that in sparse cultures, filopodia grow and retract following statistical patterns, nearly optimal for an efficient exploration of the environment. In a dense culture, filopodia exploration is still present although significantly reduced. Analysis on 1271, 6432, and 185 pairs of filopodia of DRG, PC12 and Hippocampal neurons respectively showed that the correlation coefficient |,| of the growth of more than 50% of filopodia pairs was >0.15. From a computational point of view, filopodia and lamellipodia motion can be described by a random process in which errors are corrected by efficient feedback loops. This article argues that neurons not only process sensory signals, but also solve mechanical problems throughout their entire lifespan, from the early stages of embryogenesis to adulthood. 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source]

    Pregnancy rates in mares after a single fixed time hysteroscopic insemination of low numbers of frozen-thawed spermatozoa onto the uterotubal junction

    L. H. A. MORRIS
    Summary Reasons for performing study: To compensate for the wide variation in the freezability of stallion spermatozoa, it has become common veterinary practice to carry out repeated ultrasonography of the ovaries of oestrous mares in order to be able to inseminate them within 6,12 h of ovulation with a minimum of 300,500 106 frozen-thawed spermatozoa. Furthermore, in order to achieve satisfactory fertility, this requirement for relatively high numbers of spermatozoa currently limits our ability to exploit recently available artificial breeding technologies, such as sex-sorted semen, for which only 5,20 106 spermatozoa are available for insemination. Objectives: This study was designed to evaluate and compare the efficacy of hysteroscopic vs. conventional insemination when low numbers of spermatozoa are used at a single fixed time after administration of an ovulation-inducing agent. Methods: In the present study, pregnancy rates were compared in 86 mares inseminated once only with low numbers of frozen-thawed spermatozoa (3,14 106) at 32 h after treatment with human chorionic gonadotrophin (hCG), either conventionally into the body of the uterus or hysteroscopically by depositing a small volume of the inseminate directly onto the uterotubal papilla ipsilateral to the ovary containing the pre-ovulatory follicle. Results: Pregnancy rates were similarly high in mares inseminated conventionally or hysteroscopically with 14 106 motile frozen-thawed spermatozoa (67% vs. 64%). However, when the insemination dose was reduced to 3 106 spermatozoa, the pregnancy rate was significantly higher in the mares inseminated hysteroscopically onto the uterotubal junction compared to those inseminated into the uterine body (47 vs. 15%, P<0.05). Conclusions: When inseminating mares with <10 106 frozen-thawed stallion spermatozoa, hysteroscopic uterotubal junction deposition of the inseminate is the preferred method. Potential clinical relevance: Satisfactory pregnancy rates are achievable after insemination of mares with frozen-thawed semen from fertile stallions 32 h after administration of human chorionic gonadotrophin (Chorulon)1. Furthermore, these results were obtained when mares were inseminated with 14 106 progressively motile frozen-thawed spermatozoa from 2 stallions of proven fertility. [source]

    Isolation and characterization of a novel Bacillus sp., strain YAS1, capable of transforming tyrosol under hypersaline conditions

    Slim Abdelkafi
    Abstract A moderately halotolerant, Gram-positive, aerobic, motile, spore-forming bacterium, designated as strain YAS1, was isolated from an olive-brine fermentation rich in aromatic compounds, after enrichment on tyrosol. Strain YAS1 grew between 25 and 45 C and optimally at 37 C. It grew in the presence of 0,15% (v/w) NaCl, with an optimum of 3,6% (v/w) NaCl. The DNA G + C content was found to be 49.9 mol%. Phylogenetic analysis of the 16S rRNA gene revealed that this isolate was a member of the genus Bacillus. The newly isolated strain YAS1 represents the first moderately halotolerant bacterium transforming tyrosol to p -hydroxyphenylacetic acid (PHPA) in the presence of yeast extract. [source]

    Undirected motility of filamentous cyanobacteria produces reticulate mats

    GEOBIOLOGY, Issue 3 2010
    The roles of biology in the morphogenesis of microbial mats and stromatolites remain enigmatic due to the vast array of physical and chemical influences on morphology. However, certain microbial behaviors produce complex morphological features that can be directly attributed to motility patterns. Specifically, laboratory experiments with a strain of the cyanobacteria Pseudanabaena demonstrate that distinctive morphologies arise from the undirected gliding and colliding of filaments. When filamentous cells collide, they align and clump, producing intersecting ridges surrounding areas with low cell density, i.e. reticulate structures. Cell motility is essential for the development of reticulates and associated structures: filaments organize into reticulates faster than cell division and growth, and conditions that inhibit motility also inhibit reticulate formation. Cell density of the inoculum affects the frequency of cell,cell collisions, and thus the time required for biofilm organization into reticulate structures. This also affects the specific geometry of the reticulates. These patterns are propagated into larger structures as cyanobacterial cell numbers increase and cells remain motile. Thus, cell motility is important for templating and maintaining the morphology of these microbial communities, demonstrating a direct link between a microbial behavior and a community morphology. Reticulate geometries have been identified in natural microbial mats as well as in the fossil record, and these structures can be attributed to the motility of filamentous bacteria. [source]

    Helicobacter pylori HP1034 (ylxH) is required for motility

    HELICOBACTER, Issue 5 2004
    Karin Van Amsterdam
    ABSTRACT Background.,Helicobacter pylori motility is essential for the colonization and persistence in the human gastric mucosa. So far, more than 50 genes have been described to play a role in flagellar biosynthesis. H. pylori YlxH (HP1034) is annotated as an ATP-binding protein. However, H. pylori YlxH shows similarity to proteins involved in the flagellar biosynthesis of other bacterial species. Moreover, H. pylori ylxH is found adjacent to genes involved in flagellar biosynthesis in the sequenced genomes of H. pylori 26695 and J99. We therefore aimed to determine the role of YlxH in H. pylori motility. Materials and methods., Motility, flagellar biosynthesis and transcriptional regulation of genes encoding flagellar proteins was compared between H. pylori 11A and a knockout of ylxH in H. pylori 11A. Results., The ylxH knockout in H. pylori 11A was nonmotile on soft agar plates, whereas H. pylori 11A was motile. Furthermore, the H. pylori 11A ylxH knockout lacked flagella, while H. pylori 11A possessed two to three flagella. Transcription of H. pylori flaG (HP0751), fliM (HP1031) and fliA (HP1032) was reduced in the H. pylori 11A ylxH knockout, whereas transcription of flaA (HP0601) was not altered. However, Western blot analysis showed substantially reduced amounts of the major flagellin subunit FlaA in the H. pylori 11A ylxH knockout compared to H. pylori 11A. Conclusions.,H. pylori YlxH is essential for the assembly of flagella and hence for the motility of H. pylori. [source]

    Semen quality in fertile US men in relation to geographical area and pesticide exposure

    Shanna H. Swan
    Summary We conducted the first US study to compare semen quality among study centres using standardized methods and strict quality control. We present data on semen quality in partners of 493 pregnant women recruited through prenatal clinics in four US cities during 1999,2001. Sperm concentration, semen volume and motility were determined at the centres and morphology was assessed at a central laboratory. While between-centre differences in sperm morphology and sample volume were small, sperm concentration and motility were significantly reduced in Columbia, MO (MO) relative to men in New York, NY, Minneapolis, MN and Los Angeles, CA; total number of motile sperm was 113 106 in MO and 162, 201 and 196 106 in CA, MN and NY respectively. Differences among centres remained significant in multivariate models that controlled for abstinence time, semen analysis time, age, race, smoking, history of sexually transmitted disease and recent fever (all p -values <0.01). We hypothesized that poorer sperm concentration and motility in MO men relative to other centres might be related to agricultural pesticides that are commonly used in the mid-west. We investigated this hypothesis by conducting a nested case,control study within the MO cohort. We selected 25 men in this cohort for whom all semen parameters (concentration, % normal morphology and % motile) were low as cases and an equal number of men for whom all semen parameters were within normal limits as controls. We measured metabolites of eight non-persistent, current-use pesticides in urine samples the men had provided at the time of semen collection. Pesticide metabolite levels were elevated in cases compared with controls for the herbicides alachlor and atrazine, and for the insecticide diazinon (2-isopropoxy-4-methyl-pyrimidinol) (p -values for Wilcoxon rank test = 0.0007, 0.012, and 0.0004 for alachlor, atrazine and diazinon respectively). Men with higher levels of alachlor or diazinon were significantly more likely to be cases than men with low levels [odds ratios (OR) = 30.0, 16.7 for alachlor and diazinon respectively], as were men with atrazine over the limit of detection (OR = 11.3). These associations between current-use pesticides and reduced semen quality suggest that agricultural chemicals may have contributed to the reduced semen quality seen in fertile men from mid-Missouri. [source]

    Sperm function tests and fertility

    R. J. Aitken
    Summary Traditionally, the diagnosis of male infertility has depended upon a descriptive evaluation of human semen with emphasis on the number of spermatozoa that are present in the ejaculate, their motility and their morphology. The fundamental tenet underlying this approach is that male fertility can be defined by reference to a threshold concentration of motile, morphologically normal spermatozoa that must be exceeded in order to achieve conception. Many independent studies have demonstrated that this fundamental concept is flawed and, in reality, it is not so much the absolute number of spermatozoa that determines fertility, but their functional competence. In the light of this conclusion, a range of in vitro tests have been developed to monitor various aspects of sperm function including their potential for movement, cervical mucus penetration, capacitation, zona recognition, the acrosome reaction and sperm,oocyte fusion. Such functional assays have been found to predict the fertilizing capacity of human spermatozoa in vitro and in vivo with some accuracy. Recent developments in this field include the introduction of tests to assess the degree to which human spermatozoa have suffered oxidative stress as well as the integrity of their nuclear and mitochondrial DNA. Such assessments not only yield information on the fertilizing capacity of human spermatozoa but also their ability to support normal embryonic development. [source]

    The structure of the bursa copulatrix in virgin and mated snails, Helisoma duryi (Mollusca): role of acid phosphatase in reproduction

    Eric Clelland
    Abstract. The fine structure of the bursa copulatrix of the virgin snails has been compared with that of mated snails. One of the noticeable changes after mating is an increase in the number of the Golgi and the secretory vesicles. Since some of the vesicles react positively for acid phosphatase it is suggested that this enzyme activity increases following mating. The bursa lumen of the virgin snail contains gel-like materials devoid of spermatozoa, however, following mating, the lumen is full of semen containing live spermatozoa and bacteria. The source of bacteria in the lumen is not known. Acid phosphatase activity is significantly higher in the luminal content of mated snails than in the virgin snails. The activity is higher in the lumen than in the epithelial cells, suggesting that the enzyme is secreted into the lumen where it is utilized for extracellular degradation of spermatozoa. Following mating, the spermatozoa are motile in the lumen of the bursa for ,3,7 d, but become immobile and finally undergo extracellular digestion so that intact spermatozoa are not recognizable by day 10. The use of castrated snails in mating experiments suggest that individuals of Helisoma duryi reproduce by cross fertilization and that the bursa may act as the holding organ from where the spermatozoa are periodically transported to the carrefour over ,7 d. At day 10 following mating, however, autosperms appear in the hermaphroditic duct awaiting the next mating. [source]

    Influence of temperature on biofilm formation by Listeria monocytogenes on various food-contact surfaces: relationship with motility and cell surface hydrophobicity

    G. Di Bonaventura
    Abstract Aims:, To assess the ability of Listeria monocytogenes to form biofilm on different food-contact surfaces with regard to different temperatures, cellular hydrophobicity and motility. Methods and Results:, Forty-four L. monocytogenes strains from food and food environment were tested for biofilm formation by crystal violet staining. Biofilm levels were significantly higher on glass at 4, 12 and 22C, as compared with polystyrene and stainless steel. At 37C, L. monocytogenes produced biofilm at significantly higher levels on glass and stainless steel, as compared with polystyrene. Hydrophobicity was significantly (P < 005) higher at 37C than at 4, 12 and 22C. Thirty (682%) of 44 strains tested showed swimming at 22C and 4 (91%) of those were also motile at 12C. No correlation was observed between swimming and biofilm production. Conclusions:,L. monocytogenes can adhere to and form biofilms on food-processing surfaces. Biofilm formation is significantly influenced by temperature, probably modifying cell surface hydrophobicity. Significance and Impacts of the Study:, Biofilm formation creates major problems in the food industry because it may represent an important source of food contamination. Our results are therefore important in finding ways to prevent contamination because they contribute to a better understanding on how L. monocytogenes can establish biofilms in food industry and therefore survive in the processing environment. [source]

    Identification of Bacillus spp. from Bikalga, fermented seeds of Hibiscus sabdariffa: phenotypic and genotypic characterization

    L.I.I. Ouoba
    Abstract Aims:, To identify Bacillus spp. responsible of the fermentation of Hibiscus sabdariffa for production of Bikalga, an alkaline fermented food used as a condiment in Burkina Faso. Methods and Results:, Seventy bacteria were isolated from Bikalga produced in different regions of Burkina Faso and identified by phenotyping and genotyping using PCR amplification of the 16S-23S rDNA intergenic transcribed spacer (ITS-PCR), repetitive sequence-based PCR (rep-PCR) and DNA sequencing. The isolates were characterized as motile, rod-shaped, endospore forming, catalase positive, Gram-positive bacteria. ITS-PCR allowed typing mainly at species level. Rep-PCR was more discriminative and allowed a typing at ssp. level. The DNA sequencing combined with the Blast search program and fermentation profiles using API 50CHB system allowed an identification of the bacteria as Bacillus subtilis, B. licheniformis, B. cereus, B. pumilus, B. badius, Brevibacillus bortelensis, B. sphaericus and B. fusiformis. B. subtilis were the predominant bacterium (42) followed by B. licheniformis (16). Conclusions:, Various species and ssp. of Bacillus are involved in fermentation of H. sabdariffa for production of Bikalga. Significance and Impact of the study:, Selection of starter cultures of Bacillus for controlled production of Bikalga, selection of probiotic bacteria. [source]

    Characterization of Pantoea dispersa UQ68J: producer of a highly efficient sucrose isomerase for isomaltulose biosynthesis

    L. Wu
    Abstract Aims:, Isolation, identification and characterization of a highly efficient isomaltulose producer. Methods and Results:, After an enrichment procedure for bacteria likely to metabolize isomaltulose in sucrose-rich environments, 578 isolates were screened for efficient isomaltulose biosynthesis using an aniline/diphenylamine assay and capillary electrophoresis. An isolate designated UQ68J was exceptionally efficient in sucrose isomerase activity. Conversion of sucrose into isomaltulose by UQ68J (enzyme activity of 90,100 U mg,1 DW) was much faster than the current industrial strain Protaminobacter rubrum CBS574.77 (41,66 U mg,1 DW) or a reference strain of Erwinia rhapontici (03,09 U mg,1 DW). Maximum yield of isomaltulose at 78,80% of supplied sucrose was achieved in less than half the reaction time needed by CBS574.77, and the amount of contaminating trehalulose (4%) was the lowest recorded from an isomaltulose-producing microbe. UQ68J is a Gram negative, facultatively anaerobic, motile, noncapsulate, straight rod-shaped bacterium producing acid but no gas from glucose. Based on 16S rDNA analysis UQ68J is closest to Klebsiella oxytoca, but it differs from Klebsiella in defining characteristics and most closely resembles Pantoea dispersa in phenotype. Significance and Impact of Study:, This organism is likely to have substantial advantage over previously characterized sucrose isomerase producers for the industrial production of isomaltulose. [source]

    Effect of salinity on denitrification under limited single carbon source by Marinobacter sp. isolated from marine sediment

    Miyo Nakano
    Abstract Marinobacter comprises Gram-negative, aerobic, motile, and rod-shaped bacteria within the ,-subclass of the Proteobacteria and is known to be halophilic or halotolerant, heterotrophic neutrophile. Two strains classified as belonging to Marinobacter, named PAD-2 and SeT-1, were isolated from marine sediment. The most closely related species of PAD-2 and SeT-1 are M. alkaliphilus and M. guinea, respectively. The strain PAD-2 exhibited remarkably higher denitrification at concentrations of 0.5 to 1 M NaCl (3,6% w/w) than at other salinities (2 and 3 M NaCl, 12,18% w/w), and optimal denitrification was observed in media with 0.5 M NaCl. The effect of pH on denitrification by strain PAD-2 was also examined, and the optimum denitrification occurred at neutral pH rather than under alkaline conditions. Overall, strain PAD-2 appears to be a novel halotolerant species belonging to the genus Marinobacter that shares many characteristics, such as substrate utilization profile and optimum NaCl concentration for growth with M. alkaliphilus. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Relationship between sperm density, spermatocrit, sperm motility and spawning date in wild and cultured haddock

    R. M. Rideout
    Semen was collected repeatedly from captive haddock Melanogrammus aeglefinus and the effect of seasonality on various sperm parameters was investigated. No differences in sperm traits were observed for wild and cultured haddock. A highly significant positive relationship existed between spermatocrit and spermatozoa density. A significant increase in mean spermatocrit occurred throughout the spawning season but the amount of variability explained by collection date was low (351%) due to variability between males. Each of 10 males sampled repeatedly throughout the spawning season demonstrated an increase in spermatocrit. No relationship existed between spermatocrit and proportion of motile spermatozoa when spermatocrit was ,70%. Motility was reduced in semen samples with spermatocrits >70%. The proportion of spermatozoa that were motile decreased with time since activation. Some motility was still observed after 60 min in sea water (01,152%) for sperm collected at all times within the spawning season. Of those spermatozoa that were motile, the proportion that exhibited forward swimming motion decreased and the proportion that had only vibratory movement increased with time post-activation. The speed of forward swimming spermatozoa showed no significant relationship with spermatocrit at any time between 0 and 60 min after activation. Swimming speed was negatively related to time since activation, decreasing from 174,240 ,m s,1 at 0 min to 80,128 ,m s,1 at 60 min after activation. [source]

    Respiration of steelhead trout sperm: sensitivity to pH and carbon dioxide

    R. L. Ingermann
    Steelhead trout Oncorhynchus mykiss sperm held in seminal plasma or sperm-immobilizing buffer (pH 86) at 10 C consumed O2 at the rate of c. 2 nmol O2 min,1 10,9 sperm; the rate of O2 consumption was not different in sperm held for 4 or 24 h. Decreasing the extracellular pH from 85 to 75 either by diluting semen with buffer titrated with HCl or by increasing the partial pressure of CO2 in the incubation atmosphere resulted in c. a 40% decrease in the rate of sperm respiration. The data did not, however, support the hypothesis that the precipitous reduction in the capacity for sperm motility that occurs as external pH is reduced is a result of a decrease in cellular metabolism. The rate of O2 consumption of freshly collected semen from different males was not correlated to cellular ATP content or to the proportion of sperm that were motile upon activation; the initial ATP content and sperm motility were positively correlated. The rate of O2 consumption was not significantly increased following sperm activation or by the addition of an uncoupler of oxidative phosphorylation, carbonyl cyanide p -trifluoromethoxyphenylhydrazone, suggesting that these sperm have little, if any, capacity for increased oxidative metabolism. [source]


    JOURNAL OF FOOD SAFETY, Issue 3 2005
    E.N. AMADI
    ABSTRACT Fresh, different meat types and offal were examined for the occurrence of Aeromonas species by the direct-plating and enrichment methods. The enrichment method (coefficient of variation = 15.1%) enhanced the recovery of Aeromonas species. The major Aeromonas species identified were A. sobria (67.3%) and A. hydrophila (21.2%). Other species occurred in minor proportions and were A. caviae, A. proteolytica and A. salmonicida. Out of the 52 isolates, 50 were motile species except two which were not motile and identified as the species A. proteolytica. Sixteen motile species occurred in cow, 18 in goat and 16 in lamb. The motile species and the two nonmotile species were hemolytic. They were all sensitive to chloramphenicol (30 mg) and resistant to ampicillin (10 mg). The nonmotile A. proteolytica were all resistant to tetracycline. Aeromonas caviae, A. salmonicida, A. hydrophila and A. sobria were killed after exposure to 50C (decimal reduction time, D10 = 30 s). Aeromonads are unlikely to pose a public health problem in Nigeria where meat undergoes prolonged cooking. Meat is a possible factor in the epidemiology of Aeromonas -associated gastroenteritis in man. [source]

    Investigation of hatching and early post-embryonic life of freshwater crayfish by in vitro culture, behavioral analysis, and light and electron microscopy

    Gnter Vogt
    Abstract The late embryonic and early post-embryonic life period of freshwater crayfish, which is the main time period of organogenesis, is poorly investigated because of the protective brooding behavior of crayfish mothers. A combination of in vitro culture, behavioral observations, and microscopic investigations of organs involved in hatching, attachment, exploration of the environment, and searching and processing of food yielded deeper insights in this important period of life. Experiments were performed with the robust parthenogenetic marbled crayfish. The following results were obtained: (1) Marbled crayfish can be raised in simple in vitro systems from 80% embryonic development to juvenile Stage 4 with up to 100% survival; (2) Hatching is prepared by chemical weakening of the egg shell and completed by levering actions of the hatchling's appendages; (3) The telson thread, a safety line that keeps the hatchling secured to the mother, is formed by secretions from the telson and the detaching inner layer of the egg case; (4) Molting Stage-1 juveniles are secured by an anal thread that results from delayed molting of the hindgut; (5) Active attachment of the hatchlings to the maternal pleopods with their 1st pereiopods is achieved by an innate fixed action pattern; (6) In vitro, juveniles are motile from Stage 2 despite incomplete development of their balance controlling statocysts. Movement pattern and social behavior vary greatly among individuals; and (7) Feeding starts in Stage 3, when the mouthparts and the gastric mill are fully developed. Onset of feeding is innate and does not require maternal contributions. In vitro culture of the isogenic marbled crayfish is recommended for broader use in research because it enables not only time and stage-specific sampling but also precisely timed experimental manipulations. J. Morphol., 2008. 2008 Wiley-Liss, Inc. [source]

    The Effects of Osmolality, Cryoprotectant and Equilibration Time on Striped Bass Morone saxatilis Sperm Motility

    Shuyang He
    Four experiments were designed to evaluate the effects of osmolality, cryoprotectant, and equilibration time on striped bass sperm motility. In the first experiment, solutions of NaCI or KCI with osmolalities ranging from 0 to 700 mmol/kg were tested on sperm activation. Over 60% of the sperm were activated by isotonic NaCI and KCI solutions with a treatment osmolality of 350 mmol/kg. Sperm remained motile until osmolality increased to 600 mmol/ kg. In the second and third experiments, Extenders 1, 2 and 3 with osmolalities of 350, 500, and 600 mmol/kg, respectively, were tested. Sperm samples stored in Extender 2 showed significantly higher (P 0.01) sperm motility after 10 min of exposure as well as greater (P < 0.01) post-thaw motility when compared to samples stored in Extenders 1 and 3. In the fourth experiment, two trials were carried out to evaluate the effects of cryoprotectant and equilibration time. In the first trial, methanol with a concentration of 5% and 10% yielded the highest (P < 0.05) sperm motility prior to freezing at all equilibration times examined. However, 5% DMSO yielded the highest (P < 0.01) post-thaw motility (38 3.6%). DMSO with concentrations of 10% and 15% resulted in 17 2.3% and 6 1.0% post-thaw motility, respectively. Both methanol and DMA, at all concentrations tested, resulted in less than 10% post-thaw motility. In the second trial, four DMSO concentrations with three different equilibration times were examined. We observed a significant (P < 0.001) interaction effect between DMSO concentration and equilibration time. Post-thaw motility was significantly greater (P < 0.01) with a concentration of 5% DMSO at all equilibration times examined, compared to 1.25, 2.5, and 10% DMSO. An average post-thaw motility of 40 2.9% was achieved after 10 min equilibration using 5% DMSO. [source]

    Lack of O -polysaccharide enhances biofilm formation by Bradyrhizobium japonicum

    Y.-W. Lee
    Abstract Aims:, To reveal the effects of the O -polysaccharide antigen of Bradyrhizobium japonicum LPS on biofilm formation and motility. Methods and Results:, Wild type and O-antigen-deficient mutant strains of B. japonicum were tested for biofilm formation on polyvinyl chloride (PVC) surfaces and motility on semi-solid (03%) agar media. After 7 days of incubation, the amount of biofilms formed by the mutant was c. 35-fold greater than that of the wild type. Unlike biofilm formation, the motility assay revealed that the mutant strain was less motile than the wild type. Conclusions:, This study shows enhanced biofilm formation and decreased motility by the O-antigen-deficient mutant, suggesting that the lack of the O -polysaccharide of the rhizobial LPS is associated with biofilm-forming ability and movement. Significance and Impact of the Study:, LPS plays an important role in both pathogenic and beneficial bacteria. It has also been reported that LPS deficiency negatively affects biofilm formation. However, our results demonstrate that the O-antigen-deficient mutant enhances biofilm formation, presumably through a significant increase in hydrophobicity. It is notable that the hydrophobicity of cell walls might be a key regulator in controlling biofilm development in B. japonicum. [source]

    Disruption of a Plasmodium falciparum cyclic nucleotide phosphodiesterase gene causes aberrant gametogenesis

    Cathy J. Taylor
    Summary Phosphodiesterase (PDE) and guanylyl cyclase (GC) enzymes are key components of the cGMP signalling pathway and are encoded in the genome of Plasmodium falciparum. Here we investigate the role of specific GC and PDE isoforms in gamete formation , a process that is essential for malaria transmission and occurs in the Anopheles mosquito midgut following feeding on an infected individual. Details of the intracellular signalling events controlling development of the male and female gametes from their precursors (gametocytes) remain sparse in P. falciparum. Previous work involving the addition of pharmacological agents to gametocytes implicated cGMP in exflagellation , the emergence of highly motile, flagellated male gametes from the host red blood cell. In this study we show that decreased GC activity in parasites having undergone disruption of the PfGC, gene had no significant effect on gametogenesis. By contrast, decreased cGMP-PDE activity during gametocyte development owing to disruption of the PfPDE, gene, led to a severely reduced ability to undergo gametogenesis. This suggests that the concentration of cGMP must be maintained below a threshold in the developing gametocyte to allow subsequent differentiation to proceed normally. The data indicate that PfPDE, plays a crucial role in regulating cGMP levels during sexual development. [source]

    A che -like signal transduction cascade involved in controlling flagella biosynthesis in Rhodospirillum centenum

    James E. Berleman
    Summary Rhodospirillum centenum is a photosynthetic bacterium capable of undergoing swim cell to swarm cell differentiation that allows this species to be motile on both liquid and solid media. Previous experiments have demonstrated that the che1 operon is required for the control of chemotactic and phototactic behaviour of both swim and swarm cells. In this report, we analyse the function of a second che -like gene cluster in R. centenum, the che2 gene cluster. In-frame deletion mutants of cheW2, cheB2, cheR2, cheY2, and of the entire che2 operon, exhibit defects in swim and swarm cell motility. Analysis of these strains demonstrates that they are non-motile, and that the non-motile phenotype is resulting from reduced polar and lateral flagella synthesis. Additionally, mutations in mcp2, ORF204, cheA2 and ORF74 remain chemotacticly and phototacticly competent at both high and low growth temperatures. Mutations in these che2 genes result in elevated levels of flagellin proteins giving rise to a hyperflagellate phenotype. We propose a model in which R. centenum utilizes a che -like signal transduction pathway (che2) for regulating flagellum synthesis in order to optimize swim cell-swarm cell differentiation in response to changing environmental conditions. [source]

    Pantoea ananatis: an unconventional plant pathogen

    SUMMARY Pantoea ananatis causes disease symptoms in a wide range of economically important agricultural crops and forest tree species worldwide. It is regarded as an emerging pathogen based on the increasing number of reports of diseases occurring on previously unrecorded hosts in different parts of the world. Its unconventional nature lies in the fact that, unlike the majority of plant pathogenic microbes, P. ananatis is capable of infecting humans and occurs in diverse ecological niches, such as part of a bacterial community contaminating aviation jet fuel tanks and contributing to growth promotion in potato and pepper. Taxonomy: Bacteria; Gammaproteobacteria; family Enterobacteriaceae; genus Pantoea. Microbiological properties: Gram-negative; facultatively anaerobic; most strains are motile and produce a yellow pigment in culture; indole positive. Biology:Pantoea ananatis is a common epiphyte; it also occurs endophytically in hosts where it has been reported to cause disease symptoms and in hosts where no such symptoms have been described. Some strains are ice-nucleating, a feature which has been used as a biological control mechanism against some insect pests of agricultural crops and by the food industry. Disease symptoms:Pantoea ananatis infects both monocotyledonous and dicotyledonous plants. The symptoms are diverse depending on the host infected, and include leaf blotches and spots, die-back, and stalk, fruit and bulb rot. Biological control agent:Pantoea ananatis has both antifungal and antibacterial properties. These characteristics have the potential of being exploited by biological control specialists. [source]

    Xanthomonas axonopodis pv. citri: factors affecting successful eradication of citrus canker

    James H. Graham
    SUMMARY Taxonomic status:, Bacteria, Proteobacteria, gamma subdivision, Xanthomodales, Xanthomonas group, axonopodis DNA homology group, X. axonopodis pv. citri (Hasse) Vauterin et al. Microbiological properties:, Gram negative, slender, rod-shaped, aerobic, motile by a single polar flagellum, produces slow growing, non-mucoid colonies in culture, ecologically obligate plant parasite. Host range:, Causal agent of Asiatic citrus canker on most Citrus spp. and close relatives of Citrus in the family Rutaceae. Disease symptoms:, Distinctively raised, necrotic lesions on fruits, stems and leaves. Epidemiology:, Bacteria exude from lesions during wet weather and are disseminated by splash dispersal at short range, windblown rain at medium to long range and human assisted movement at all ranges. Crop loss:, Severe infections cause defoliation, blemished fruit, premature fruit drop, die-back of twigs and general debilitation of the tree. Distribution:, Citrus canker is not present in all subtropical to tropical regions of citriculture in the world, so considerable regulatory efforts are expended to prevent the introduction and spread of X. axonopodis pv. citri into areas in the Americas, Australia and elsewhere, with climates conducive to the disease. Importance:, Limited strategies exist for suppression of citrus canker on more susceptible cultivars. Blemished fruit are unmarketable and exposed fruit are restricted in market access. The economic impact of loss of markets is much greater than that from yield and quality reductions of the crop. Useful websites:, , , , , , , . [source]

    Xanthomonas citri: breaking the surface

    Asha M. Brunings
    SUMMARY Taxonomy: Bacteria; Proteobacteria, Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae, Xanthomonas. Microbiological properties: Gram-negative, obligately aerobic, straight rods, motile by a single polar flagellum, yellow pigment. Related species:X. campestris , X. axonopodis , X. oryzae , X. albilineans . Host range: Affects Rutaceous plants, primarily Citrus spp., Fortunella spp., and Poncirus spp., world-wide. Quarantined pathogen in many countries. Economically important hosts are cultivated orange, grapefruit, lime, lemon, pomelo and citrus rootstock. Disease symptoms: On leaves, first appearance is as oily looking, 2,10 mm, similarly sized, circular spots, usually on the abaxial surface. On leaves, stems, thorns and fruit, circular lesions become raised and blister-like, growing into white or yellow spongy pustules. These pustules then darken and thicken into a light tan to brown corky canker, which is rough to the touch. On stems, pustules may coalesce to split the epidermis along the stem length, and occasionally girdling of young stems may occur. Older lesions on leaves and fruit tend to have more elevated margins and are at times surrounded by a yellow chlorotic halo (that may disappear) and a sunken centre. Sunken craters are especially noticeable on fruit, but the lesions do not penetrate far into the rind. Defoliation and premature abscission of affected fruit occurs on heavily infected trees. Useful websites: ; [source]