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Vegetative Cells (vegetative + cell)

Distribution by Scientific Domains

Life Sciences	90%
Chemistry	7%

Distribution within Life Sciences

Phycology	37%
Applied Microbiology	14%
Biotechnology (Life Sciences)	5%
Microbiology & Virology	3%

Selected Abstracts

GROWTH INHIBITION OF CLOSTRIDIUM PERFRINGENS VEGETATIVE CELLS AND SPORES USING CHICKEN IMMUNOGLOBULIN Y

JOURNAL OF FOOD SAFETY, Issue 4 2009
MIN S. SONG
ABSTRACT Egg yolk antibody (IgY) was isolated by the water dilution method from the egg yolk of chickens immunized with Clostridium perfringens vegetative cells and spores. Specific binding activity of IgY against C. perfringens vegetative cells and spores remained relatively high during the immunization period (up to 9 weeks). The titer of specific IgY against C. perfringens spores was 1.4-fold less than that of specific IgY against C. perfringens vegetable cells. The specific IgY powder (10 µg/mL) was found to inhibit the growth of C. perfringens vegetative cells or C. perfringens spores in a liquid medium. The difference of C. perfringens vegetative cell growth between the treatment and control groups was 8.9 × 106 colony forming units (cfu)/mL at 8 h of incubation and 9.95 × 107 cfu/mL at 24 h of incubation. Significant cfu reductions in C. perfringens spores were also observed with specific IgY powder at 24 h of incubation. PRACTICAL APPLICATIONS IgY antibody exerts an antimicrobial activity against pathogens by binding, immobilizing and consequently reducing or inhibiting the growth, replication or colony forming ability of pathogenic bacteria; thus, it is proved to be a viable alternative for antibiotics and preservatives. In this study, IgY against Clostridium perfringens can be used to replace chemical preservatives in food industries. Because IgY functions well at low temperature, it can be used to inhibit the growth of Clostridia which germinate in refrigerated storage conditions, thus preventing foodborne enterotoxicity caused by such bacteria. In practical applications, natural antimicrobial IgY antibody can be applied to meat products for the improvement of food safety. [source]

PSEUDULVELLA AMERICANA BELONGS TO THE ORDER CHAETOPELTIDALES (CLASS CHLOROPHYCEAE), EVIDENCE FROM ULTRASTRUCTURE AND SSU RDNA SEQUENCE DATA,

JOURNAL OF PHYCOLOGY, Issue 4 2006
M. Virginia Sanchez-Puerta
The genus Pseudulvella Wille 1909 includes epiphytic, freshwater, or marine disk-shaped green microalgae that form quadriflagellate zoospores. No ultrastructural or molecular studies have been conducted on the genus, and its evolutionary relationships remain unclear. The purpose of the present study is to describe the life history, ultrastructural features, and phylogenetic affiliations of Pseudulvella americana (Snow) Wille, the type species of the genus. Thalli of this microalga were prostrate and composed of radiating branched filaments that coalesced to form a disk. Vegetative cells had a pyrenoid encircled by starch plates and traversed by one or two convoluted cytoplasmic channels. They had well-defined cell walls without plasmodesmata. Asexual reproduction was by means of tetraflagellate zoospores formed in numbers of two to eight from central cells of the thallus. The flagellar apparatus of zoospores was cruciate, with four basal bodies and four microtubular roots. The paired basal bodies lay directly opposite (DO) one another. The microtubular root system had a 5-2-5-2 alternation pattern, where the "s" roots contained five microtubules in a four-over-one configuration. A tetralobate nonstriated distal fiber connected all four basal bodies. A wedge-shaped proximal sheath subtended each of the basal bodies. The ultrastructural features of the zoospores were those of members of the order Chaetopeltidales. Phylogenetic analyses based on SSU rDNA placed P. americana sister to Chaetopeltis orbicularis in a well-supported Chaetopeltidales clade. Such a combination of features confirmed that this alga is a member of the order Chaetopeltidales. [source]

PYRENOID FORMATION ASSOCIATED WITH THE CELL CYCLE IN THE BROWN ALGA, SCYTOSIPHON LOMENTARIA (SCYTOSIPHONALES, PHAEOPHYCEAE),

JOURNAL OF PHYCOLOGY, Issue 6 2003
Chikako Nagasato
Vegetative cells of the brown alga Scytosiphon lomentaria (Lyngbye) Link characteristically have only one chloroplast with a prominent protruding pyrenoid, whereas zygotes have both paternal and maternal chloroplasts. In zygotes, before cell and chloroplast division, each chloroplast has an old and a new pyrenoid. In this study, we raised a polyclonal antibody to RUBISCO and examined the distribution of RUBISCO by immunofluorescence microscopy, focusing on new pyrenoid formation in vegetative cells of gametophytes and zygotes in Scytosiphon. In interphase, only one old pyrenoid was positively indicated by anti-RUBISCO antibody in vegetative cells of gametophytes. From mid-S phase, small fluorescence aggregates reflecting RUBISCO localization started to appear at stroma positions other than adjacent to the old protruding pyrenoid. The fluorescent spots eventually coalesced into a protrusion into the adjacent cytoplasm. We also used inhibitors to clarify the relationship between the cell cycle and new pyrenoid formation, using zygotes after fertilization. When DNA replication was blocked by aphidicolin, new pyrenoid formation was also inhibited. Washing out aphidicolin permitted new pyrenoid formation with the progression of the cell cycle. When mitosis was prolonged by nocodazole, which disrupted the spindle microtubules, the fluorescent masses indicating RUBISCO localization continued to increase when compared with pyrenoid formation in untreated zygotes. During treatment with chloramphenicol, mitosis and cytokinesis were completed. However, there was no occurrence of new RUBISCO localization within the chloroplast stroma beyond the old pyrenoid. From these observations, it seems clear that new pyrenoid formation in the brown alga Scytosiphon depends on the cell cycle. [source]

SNOW ALGAE OF THE WINDMILL ISLANDS, CONTINENTAL ANTARCTICA: DESMOTETRA AUREOSPORA, SP.

JOURNAL OF PHYCOLOGY, Issue 1 2001

Two cryophilic Desmotetra species, D. aureospora, sp. nov., and D. antarctica (Fritsch) Ling appear to be unique to the southern hemisphere snow ecosystem, or at least to the Windmill Island region, Antarctica. They have not been encountered in previous extensive studies of the Arctic and northern alpine regions. Also unusual are the higher pH (6.8 and 7.8) and conductivities of 279 ,S·cm,1 and 426 ,S·cm,1 for habitat conditions of D. antarctica that can be attributed to the influence of penguin guano. Both species are characterized by cells enveloped in individual mucilage layers, 1,3 contractile vacuoles, and a cup-shaped chloroplast containing a diffuse pyrenoid. The cells divided in three planes to form cubical loosely aggregated green cell packages embedded in mucilage. Vegetative cells of the two species cannot be distinguished with certainty; however, their zygospores are very different. Desmotetra aureospora has spherical, smooth-walled, golden zygospores, whereas D. antarctica has pale, yellow green, aereolate zygospores. Mucilage stalk morphology of cells in stationary-phase cultures can also be used to separate the two species. Zygospores of D. antarctica have previously been identified as the snow alga Trochiscia antarctica Fritsch. Both species are currently maintained in culture at the Australian Antarctic Division. The cultures did not grow at temperatures above 15° C. The two species are compared with the soil alga D. stigmatica (Deason) Deason et Floyd, the only other species in the genus, and also with Chlorosarcina stigmatica Deason strain T105. Results show that the three Desmotetra species form a natural group and that the absence or presence of a wall on the zoospore is of dubious value in classifications of green algal taxa above the species level. [source]

Ultrastructure of Lobocharacium coloradoense, gen. et sp. nov. (Chlorophyta, Characiosiphonaceae), an unusual coenocyte from Colorado

JOURNAL OF PHYCOLOGY, Issue 2 2000
Paul Kugrens
Light and electron microscopic descriptions are provided for Lobocharacium coloradoense, gen. et sp. nov., a unicellular coenocytic green alga isolated from a power plant's retaining pond in north-central Colorado. Vegetative cells range from 120,230 ,m in length and 80,120 ,m in diameter in culture. The large vegetative cells are attached to substrates by small discoid attachment pads. The cells are multinucleate and consist of distinct cytoplasmic lobes, with each lobe containing a chloroplast and a basal nucleus. Chloroplasts are somewhat cone-shaped in profile and stellate or lobed when viewed from the surface, and each has a central, basal pyrenoid. Hundreds of these cytoplasmic lobes occur within a cell, and thin cytoplasmic bridges interconnect the lobes. When a vegetative cell matures, each of the cytoplasmic lobes cleaves to form numerous fusiform zoospores or spherical isogametes. The biflagellate isogametes range in size from 4,10 ,m, they lack a cell wall, they have a cup-shaped chloroplast with a pyrenoid and stigma, and they have a nucleus close to the basal bodies. Isogametes are incapable of forming vegetative cells. Zoospores are biflagellate and fusiform, measuring 8,12 ,m in length and 4,6 ,m in diameter. Each zoospore has a cell wall, a single parietal chloroplast with a prominent pyrenoid in the center of the chloroplast, and a long oval stigma. Gamete and zoospore release involves a dissolution of the entire vegetative wall. Released zoospores usually settle and cluster near the vegetative cell from which they were produced, attach to the substrate with their flagella, and, shortly after losing their flagella, extrude mucilage through the flagellar pores in the wall to form a small discoid attachment pad. The incipient vegetative cell is fusiform and uninucleate, but it becomes more rounded and multinucleate as enlargement occurs. Most vegetative cells in culture become dormant, and the chloroplast becomes orange in color. Some cells form single aplanospores that can withstand desiccation, but occasionally numerous aplanospores may also be formed later in the larger vegetative cells. [source]

16S rDNA targeted PCR for the detection of Paenibacillus macerans

LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2003
R.E. Vollú
Abstract Aims: To develop a PCR detection method, which could be used for the detection of Paenibacillus macerans in environmental samples or to help the identification of strains suspected to belong to this species. Methods and Results: Primers specific for P. macerans were developed based on the 16S rRNA gene sequence and were evaluated by PCR performed with genomic DNA from other Paenibacillus, other bacteria and DNA from soil as templates. The primers were shown to be specific for P. macerans strains and to amplify a 981-bp amplicon. Vegetative cells of P. macerans LMD 24.10T were tracked in Cerrado soil in 24-h experiments and PCR allowed the detection of 103 introduced cells per gram of dry soil. Conclusions: This PCR detection method was adequate to assess the presence of P. macerans in Cerrado soil. Significance and Impact of the Study: It can also be used after culturing to rapid confirm the identity of isolates suspected to belong to P. macerans. [source]

SEXUAL PROCESSES AND PHYLOGENETIC RELATIONSHIPS OF A HOMOTHALLIC STRAIN IN THE CLOSTERIUM PERACEROSUM,STRIGOSUM,LITTORALE COMPLEX (ZYGNEMATALES, CHAROPHYCEAE),

JOURNAL OF PHYCOLOGY, Issue 2 2010
Yuki Tsuchikane
Members of the Closterium peracerosum,strigosum,littorale (C. psl.) complex are unicellular charophycean algae in which there are two modes of zygospore formation, heterothallic and homothallic. A homothallic strain of Closterium (designation, kodama20) was isolated from a Japanese rice paddy field. Based on alignment of the 1506 group-I introns, which interrupt nuclear SSU rDNAs, homothallic kodama20 is most closely related to the heterothallic mating group II-B, which is partially sexually isolated from group II-A. Time-lapse photography of the conjugation process in kodama20 revealed that most of the observed zygospores originated from one vegetative cell. The sexual conjugation process consisted of five stages: (1) cell division resulting in the formation of two sister gametangial cells from one vegetative cell, (2) formation of a sexual pair between the two sister gametangial cells (or between gametangial cells of another adjoined individual), (3) formation of conjugation papillae, (4) release of gametic protoplasts from both members of a pair, and (5) formation of the zygospore by protoplast fusion. For conjugation to progress, the cell density and light condition in the culture was critical. We suggested the presence of a conjugation promotion factor. [source]

SYSTEMATICS OF THE HILDENBRANDIALES (RHODOPHYTA): GENE SEQUENCE AND MORPHOMETRIC ANALYSES OF GLOBAL COLLECTIONS,

JOURNAL OF PHYCOLOGY, Issue 2 2003
Alison R. Sherwood
Fifty-seven collections of marine and freshwater Hildenbrandia from North America, South America, Europe, and Africa were compared with 21 type and historically important specimens using multivariate morphometrics. Additionally, phylogenetic analyses of 48 specimens of Hildenbrandia and two specimens of Apophlaea were carried out based on sequences of the rbcL chloroplast gene and the nuclear 18S rRNA gene. Morphometric analyses based on vegetative cell and filament dimensions distinguished two groups of freshwater Hildenbrandia specimens, the first corresponding to those collections from North America and the Philippines and the second to those from Europe and the Canary Islands. The first group had smaller mean cell and filament dimensions (cells 4.0 × 4.4 ,m, filaments 46.5 ,m) and corresponded to H. angolensis, whereas the second group had larger mean dimensions (cells 5.8 × 6.6 ,m, filaments 55.3 ,m) and represented H. rivularis. Marine specimens were morphometrically distinguishable into two groups based on tetrasporangial division pattern as well as other thallus characters. However, measurements and character determinations of some type specimens differed greatly from the original descriptions, and thus further work to determine the stability of these characters is required. Phylogenetic reconstruction based on the 18S rRNA gene and rbcL gene sequence data generally demonstrated separation of the marine and freshwater forms of Hildenbrandia, with some marine taxa forming monophyletic groups (e.g. H. lecannellieri and H. occidentalis) and others forming paraphyletic groups (e.g. H. rubra). The two specimens of Apophlaea formed a monophyletic group within the paraphyletic genus Hildenbrandia. [source]

SEXUAL REPRODUCTION, MATING SYSTEM, AND PROTOPLAST DYNAMICS OF SEMINAVIS (BACILLARIOPHYCEAE)1

JOURNAL OF PHYCOLOGY, Issue 5 2002
Victor A. Chepurnov
Cell division, the mating system, and auxosporulation were studied in the marine epipelic diatom Seminavis cf. robusta Danielidis & D. G. Mann. The interphase protoplast contains two girdle-appressed chloroplasts, each with an elongate bar-like pyrenoid, and also a central nucleus, located in a bridge between two vacuoles. Before cell division, the chloroplasts divide transversely and translocate onto the valves. The nucleus relocates to the ventral side for mitosis. After cytokinesis and valve formation, the chloroplasts move back to the girdle, showing a constant clockwise movement relative to the epitheca of the daughter cell. Seminavis cf. robusta is dioecious, and sexual reproduction is possible once cells are less than 50 ,m. In crosses of compatible clones, gametangia pair laterally, without the formation of a copulation envelope, and produce two gametes apiece. The intensity of sexualization increases as cells reduce further in size below the 50-,m threshold. At plasmogamy, the gametangia dehisce fully and the gametes, which were morphologically and behaviorally isogamous, fuse in the space between the gametangial thecae. The auxospore forms a transverse and longitudinal perizonium. After expansion is complete, there is an unequal contraction of the protoplast within the perizonium, creating the asymmetrical shape of the vegetative cell. Apart from this last feature, almost all characteristics exhibited by the live cell and auxospores of Seminavis agree with what is found in Navicula sensu stricto, supporting the classification of both in the Naviculaceae. Haploid parthenogenesis and polyploid auxospores were found, lending support to the view that change in ploidy may be a significant mechanism in diatom evolution. [source]

Ultrastructure of Lobocharacium coloradoense, gen. et sp. nov. (Chlorophyta, Characiosiphonaceae), an unusual coenocyte from Colorado

Bacterial Inactivation by Solar Ultraviolet Radiation Compared with Sensitivity to 254 nm Radiation

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2009
Thomas P. Coohill
Our goal was to derive a quantitative factor that would allow us to predict the solar sensitivity of vegetative bacterial cells to natural solar radiation from the wealth of data collected for cells exposed to UVC (254 nm) radiation. We constructed a solar effectiveness spectrum for inactivation of vegetative bacterial cells by combining the available action spectra for vegetative cell killing in the solar range with the natural sunlight spectrum that reaches the ground. We then analyzed previous studies reporting the effects of solar radiation on vegetative bacterial cells and on bacterial spores. Although UVC-sensitive cells were also more sensitive to solar radiation, we found no absolute numerical correlation between the relative solar sensitivity of vegetative cells and their sensitivity to 254 nm radiation. The sensitivity of bacterial spores to solar exposure during both summer and winter correlated closely to their UVC sensitivity. The estimates presented here should make it possible to reasonably predict the time it would take for natural solar UV to kill bacterial spores or with a lesser degree of accuracy, vegetative bacterial cells after dispersion from an infected host or after an accidental or intentional release. [source]

A Procedure for High-Yield Spore Production by Bacillus s ubtilis

BIOTECHNOLOGY PROGRESS, Issue 4 2005
Sandra M. Monteiro
Bacillus subtilis spores have a number of potential applications, which include their use as probiotics and competitive exclusion agents to control zoonotic pathogens in animal production. The effect of cultivation conditions on Bacillus subtilis growth and sporulation was investigated in batch bioreactions performed at a 2-L scale. Studies of the cultivation conditions (pH, dissolved oxygen concentration, and media composition) led to an increase of the maximum concentration of vegetative cell from 2.6 × 109 to 2.2 × 1010 cells mL - 1 and the spore concentration from 4.2 × 108 to 5.6 × 109 spores mL - 1. A fed-batch bioprocess was developed with the addition of a nutrient feeding solution using an exponential feeding profile obtained from the mass balance equations. Using the developed feeding profile, starting at the middle of the exponential growth phase and finishing in the late exponential phase, an increase of the maximum vegetative cell concentration and spore concentration up to 3.6 × 1010 cells mL - 1 and 7.4 × 109 spores mL - 1, respectively, was obtained. Using the developed fed-batch bioreaction a 14-fold increase in the concentration of the vegetative cells was achieved. Moreover, the efficiency of sporulation under fed-batch bioreaction was 21%, which permitted a 19-fold increase in the final spore concentration, to a final value of 7.4 × 109 spores mL - 1. This represents a 3-fold increase relative to the highest reported value for Bacillus subtilis spore production. [source]

Early Bacillus anthracis,macrophage interactions: intracellular survival and escape

CELLULAR MICROBIOLOGY, Issue 6 2000
Terry C. Dixon
This study describes early intracellular events occurring during the establishment phase of Bacillus anthracis infections. Anthrax infections are initiated by dormant endospores gaining access to the mammalian host and becoming engulfed by regional macrophages (M,). During systemic anthrax, late stage events include vegetative growth in the blood to very high titres and the synthesis of the anthrax exotoxin complex, which causes disease symptoms and death. Experiments focus on the early events occurring during the first few hours of the B. anthracis infectious cycle, from endospore germination up to and including release of the vegetative cell from phagocytes. We found that newly vegetative bacilli escape from the phagocytic vesicles of cultured M, and replicate within the cytoplasm of these cells. Release from the M, occurs 4,6 h after endospore phagocytosis, timing that correlates with anthrax infection of test animals. Genetic analysis from this study indicates that the toxin plasmid pXO1 is required for release from the M,, whereas the capsule plasmid pXO2 is not. The transactivator atxA, located on pXO1, is also found to be essential for release, but the toxin genes themselves are not required. This suggests that M, release of anthrax bacilli is atxA regulated. The putative ,escape' genes may be located on the chromosome and/or on pXO1. [source]

THE ECOLOGY AND GENETICS OF FITNESS IN CHLAMYDOMONAS.

EVOLUTION, Issue 1 2002
VIII.
Abstract According to classical evolutionary theory, sexual recombination can generate the variation necessary to adapt to changing environments and thereby confer an evolutionary advantage of sexual over asexual reproduction. Using the green alga, Chlamydomonas reinhardtii, we investigated the effect of a single sexual episode on adaptation of heterotrophic growth on different carbon sources. In an initial mixture of isolates, sex was induced and the resulting offspring constituted the sexual populations, along with any unmated vegetative cells; the unmated mixture of isolates represented the asexual populations. Mean and variance in division rates (i.e., fitness) were measured four times during approximately 50 generations of vegetative growth in the dark on all possible combinations of four carbon sources. Consistent with effects of recombination of epistatic genes in linkage disequilibrium, sexual populations initially had a higher variance in fitness, but their mean fitness was lower than that of asexual populations, possibly due to recombinational load. Subsequently, fitness of sexual populations exceeded that of asexual ones, but finally they regained parity in both mean and variance of fitness. Although recombination was not more effective on more complex substrates, these results generally support the idea that sex can accelerate adaptation to novel environments. [source]

From soil to gut: Bacillus cereus and its food poisoning toxins

FEMS MICROBIOLOGY REVIEWS, Issue 4 2008
Lotte P. Stenfors Arnesen
Abstract Bacillus cereus is widespread in nature and frequently isolated from soil and growing plants, but it is also well adapted for growth in the intestinal tract of insects and mammals. From these habitats it is easily spread to foods, where it may cause an emetic or a diarrhoeal type of food-associated illness that is becoming increasingly important in the industrialized world. The emetic disease is a food intoxication caused by cereulide, a small ring-formed dodecadepsipeptide. Similar to the virulence determinants that distinguish Bacillus thuringiensis and Bacillus anthracis from B. cereus, the genetic determinants of cereulide are plasmid-borne. The diarrhoeal syndrome of B. cereus is an infection caused by vegetative cells, ingested as viable cells or spores, thought to produce protein enterotoxins in the small intestine. Three pore-forming cytotoxins have been associated with diarrhoeal disease: haemolysin BL (Hbl), nonhaemolytic enterotoxin (Nhe) and cytotoxin K. Hbl and Nhe are homologous three-component toxins, which appear to be related to the monooligomeric toxin cytolysin A found in Escherichia coli. This review will focus on the toxins associated with foodborne diseases frequently caused by B. cereus. The disease characteristics are described, and recent findings regarding the associated toxins are discussed, as well as the present knowledge on virulence regulation. [source]

Psychrophilic and psychrotrophic clostridia: sporulation and germination processes and their role in the spoilage of chilled, vacuum-packaged beef, lamb and venison

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2010
Katharine H. Adam
Summary Spoilage of beef, lamb and venison by psychrophilic and psychrotrophic clostridial species renders meat unacceptable resulting in financial losses and reduced consumer confidence. A number of clostridial strains, including Clostridium algidicarnis, Clostridium algidixylanolyticum, Clostridium estertheticum, Clostridium frigidicarnis and Clostridium gasigenes, have been implicated in red meat spoilage. Unlike other spoilers, these clostridia are able to grow in anaerobic conditions and at chilled temperatures (some at ,1.5 °C the optimal storage temperature for chilled red meat). The spoilage they cause is characterised by softening of the meat, production of large amounts of drip (exudates), offensive odours and in the case of C. estertheticum and C. gasigenes production of gas. Spoilage occurs following the introduction of clostridial spores into vacuum packages during processing. Germination of spores is necessary for the growth of vegetative cells, which cause spoilage. Current mitigation strategies focus on good management practice within meat processing plants. However, this is not always sufficient to prevent spoilage. This review summarises the issues associated with meat spoilage because of psychrotolerant clostridia and discusses areas that require further study. [source]

Effects of porcine bile on survival of Bacillus cereus vegetative cells and Haemolysin BL enterotoxin production in reconstituted human small intestine media

JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007
T. Clavel
Abstract Aims: To determine the effects of porcine bile (PB) on Bacillus cereus vegetative cells and Haemolysin BL (HBL) enterotoxin production in reconstituted small intestine media (IM). Methods and Results: The effects of PB on the growth of B. cereus vegetative cells in reconstituted IM at PB concentrations ranging between 0 and 3·0 g l,1 were examined. Four gastric media (GM) named GM-J broth (JB), GM-chicken, GM-milk and GM-pea were prepared by mixing equal volumes of a gastric electrolyte solution containing pepsin with JB, chicken, semi-skimmed milk and pea soup, respectively. Bacillus cereus was inoculated at approx. 2 × 104 CFU ml,1 into each GM at pH 5·0 for 30 min at 37°C, then mixed to the same volume of double-strength JB (IM) and PB to give concentrations of between 0 and 3·0 g of PB per litre at pH 6·5 and incubated at 37°C. The diarrhoeal B. cereus strain F4430/73 grew in IM-JB, IM-chicken and IM-milk at PB concentrations of up to 0·6, 1·5 and 1·2 g l,1, respectively. Growth was observed in IM-pea at all concentrations tested. The highest PB concentrations allowing a 3 log B. cereus increase in IM-JB, IM-chicken, IM-milk and IM-pea after a 7,10 h incubation period were 0·3, 0·9, 0·9 and 3·0 g l,1, respectively. The effect of PB on B. cereus cells was strongest in IM-JB, followed by IM-chicken, IM-milk and IM-pea. Haemolysin BL enterotoxin was detectable in IM-chicken, IM-whole milk, IM-semi-skimmed milk and IM-pea up to PB concentrations of only 0·6, 0·6, 0·3 and 0·9 g l,1, respectively. The diarrhoeal B. cereus strain F4433/73 behaved similarly to B. cereus strain F4430/73, whereas the food strain TZ415 was markedly more susceptible to bile. Conclusions: The tolerance of B. cereus cells to PB strongly depends on the type of food contained in the IM. Bile tolerance is also subject to strain variation. Significance and Impact of the Study: The probability that B. cereus cells will grow in the small intestine, produce toxins and cause diarrhoea is likely to depend on the food they are ingested with, on the bile tolerance of the B. cereus strain, and on bile concentration. [source]

Tolerance to challenges miming gastrointestinal transit by spores and vegetative cells of Bacillus clausii

JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2006
G. Cenci
Abstract Aims:, To study Bacillus clausii from a pharmaceutical product (Enterogermina O/C, N/R, SIN, T) and reference strains (B. clausii and Bacillus subtilis) for eco-physiological aspects regarding the gut environment. Methods and Results:, Spores and vegetative cells were challenged in vitro miming the injury of gastrointestinal transit: pH variations, exposure to conjugated and free bile salts, microaerophilic and anaerobic growth. No relevant differences were found studying the growth at pH 8 and 10, whereas at pH 7 the yields obtained for O/C and SIN were higher than those obtained for N/R and T strains. The spores were able to germinate and grow in the presence of conjugated bile salts (up to 1%, w/v) or free bile salts (0·2%) and also exhibited tolerance for the combined acid-bile challenge. As evidenced by lag-time, growth rate and cell yield the tolerance of Enterogermina isolates for conjugated salts was comparable with that of B. clausii type strain (DSM 8716T), and resulted higher than that observed for B. subtilis (ATCC 6051T). All the considered B. clausii strains demonstrated microaerophilic growth, but only some grew anaerobically in a nitrate medium. Conclusions:, The ability of B. clausii spores to germinate after an acid challenge and grow as vegetative cells both in the presence of bile and under limited oxygen availability is consistent with the beneficial health effects evidenced for spore-forming probiotics in recent clinical studies. Significance and Impact of the Study:, The experimental evidence from this study emphasizes some functional properties of B. clausii strains regarding their use as probiotics. [source]

GROWTH INHIBITION OF CLOSTRIDIUM PERFRINGENS VEGETATIVE CELLS AND SPORES USING CHICKEN IMMUNOGLOBULIN Y

TAXONOMIC STUDY OF TWO NEW GENERA OF FUSIFORM GREEN FLAGELLATES, TABRIS GEN.

JOURNAL OF PHYCOLOGY, Issue 2 2009

On the basis of LM, we isolated strains of two species of fusiform green flagellates that could be assigned to former Chlorogonium (Cg.) Ehrenb. One species, "Cg."heimii Bourr., lacked a pyrenoid in its vegetative cells and required organic compounds for growth. The other was similar to Cg. elongatum (P. A. Dang.) Francé and "Cg."acus Nayal, but with slightly smaller vegetative cells. Their molecular phylogeny was also studied based on combined 18S rRNA, RUBISCO LSU (rbcL), and P700 chl a -apoprotein A2 (psaB) gene sequences. Both species were separated from Chlorogonium emend., Gungnir Nakada and Rusalka Nakada, which were formerly assigned to Chlorogonium. They were accordingly assigned to new genera, Tabris Nakada gen. nov. and Hamakko (Hk.) Nakada gen. nov. as T. heimii (Bourr.) Nakada comb. nov. and Hk. caudatus Nakada sp. nov., respectively. Tabris is differentiated from other genera of fusiform green flagellates by its vegetative cells, which only have two apical contractile vacuoles and lack a pyrenoid in the chloroplast. Hamakko, on the other hand, is distinguishable by the fact that its pyrenoids in vegetative cells are penetrated by flattened thylakoid lamellae. [source]

HOMOTHALLIC AUXOSPORULATION IN PSEUDO-NITZSCHIA BRASILIANA (BACILLARIOPHYTA),

JOURNAL OF PHYCOLOGY, Issue 1 2009
Sonia Quijano-Scheggia
Most pennate diatoms are allogamous, and various types of mating systems have been described. In Pseudo-nitzschia, reproductive stages have been identified in some species, and it is generally accepted that the genus is mainly heterothallic. Here we report homothallic auxosporulation of Pseudo-nitzschia brasiliana Lundholm, Hasle et G. A. Fryxell. To our knowledge, this is the first verified description of homothallic sexual reproduction in the genus. Auxospore formation was observed in all 16 subclones derived from three initial clonal cultures of P. brasiliana. Pairing was followed by production of two gametes per gametangium, which fused to give two zygotes. Each zygote (early auxospore) was initially spherical and adhered to one girdle band of the parental frustule. The two auxospores tended to expand parallel to each other and perpendicular to the parental frustule. Elongation was synchronous, slightly asynchronous, or totally asynchronous. The entire process of sexual reproduction, from gamete formation to the appearance of the initial vegetative cells, took 2,4 d. The occurrence of sex in a homothallic species seems an advantageous life strategy for this species in that any encounter between cells of the right size class is potentially sexual. [source]

COMPARATIVE MORPHOLOGY AND MOLECULAR PHYLOGENETIC ANALYSIS OF THREE NEW SPECIES OF THE GENUS KARENIA (DINOPHYCEAE) FROM NEW ZEALAND,

JOURNAL OF PHYCOLOGY, Issue 1 2004
Allison J. Haywood
Three new dinoflagellate species, Karenia papilionacea sp. nov., Karenia selliformis sp. nov., and Karenia bidigitata sp. nov., were compared with the toxic species Karenia mikimotoi (Miyake & Kominami ex Oda) G. Hansen & Moestrup, Karenia brevis (Davis) G. Hansen & Moestrup, and Karenia brevisulcata (Chang) G. Hansen & Moestrup using the same fixative. Distinguishing morphological characters for the genus Karenia included a smooth theca and a linear apical groove. The new species can be distinguished on the basis of morphological characters of vegetative cells that include the location and shape of the nucleus; the relative excavation of the hypotheca; the characteristics of apical and sulcal groove extensions on the epitheca; the cellular shape, size, and symmetry; the degree of dorsoventral compression; and the presence of an apical protrusion or carina. Species with pronounced dorsoventral compression swim in a distinctive fluttering motion. An intercingular tubular structure traversing the proximal and distal ends of the cingulum is common to the species of Karenia, Karlodinium micrum (Leadbeater & Dodge) J. Larsen, Gymnodinium pulchellum J. Larsen, and Gyrodinium corsicum Paulmier. Molecular phylogenetic analyses of rDNA sequence alignments show that the new species are phylogenetically distinct but closely related to K. mikimotoi and K. brevis. [source]

PYRENOID FORMATION ASSOCIATED WITH THE CELL CYCLE IN THE BROWN ALGA, SCYTOSIPHON LOMENTARIA (SCYTOSIPHONALES, PHAEOPHYCEAE),

Ultrastructure of Lobocharacium coloradoense, gen. et sp. nov. (Chlorophyta, Characiosiphonaceae), an unusual coenocyte from Colorado

Oral vaccination with envelope protein VP28 against white spot syndrome virus in Procambarus clarkii using Bacillus subtilis as delivery vehicles

LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2008
L.L. Fu
Abstract Aims:, To achieve high-level expression and secretion of active VP28 directed by a processing-efficient signal peptide in Bacillus subtilis WB600 and exploit the possibility of obtaining an oral vaccine against white spot syndrome virus (WSSV) using vegetative cells or spores as delivery vehicles. Methods and Results:, The polymerase chain reaction (PCR)-amplified vp28 gene was inserted into a shuttle expression vector with a novel signal peptide sequence. After electro-transformation, time-courses for recombinant VP28 (rVP28) secretion level in B. subtilis WB600 were analysed. Crayfish were divided into three groups subsequently challenged by 7-h immersion at different time points after vaccination. Subgroups including 20 inter-moult crayfish with an average weight of 15 g in triplicate were vaccinated by feeding coated food pellets with vegetative cells or spores for 20 days. Vaccination trials showed that rVP28 by spore delivery induced a higher resistance than using vegetative cells. Challenged at 14 days postvaccination, the relative per cent survival (RPS) values of groups of rVP28-bv and rVP28-bs was 51·7% and 78·3%, respectively. Conclusions:, The recombinant B. subtilis strain with the ability of high-level secretion of rVP28 can evoke protection of crayfish against WSSV by oral delivery. Significance and Impact of the Study:, Oral vaccination by the B. subtilis vehicle containing VP28 opens a new way for designing practical vaccines to control WSSV. [source]

Decimal reduction times of Pyrodinium bahamense var. compressum and Escherichia coli in chlorine- and ultraviolet-treated seawater

LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2001
M.P.V. Azanza
Aims:,Decimal reduction times (D -values) of the vegetative cells of Pyrodinium bahamense var. compressum and Escherichia coli in ultraviolet- and chlorine-treated seawater were established. Methods and Results:,The cells of the test organisms were exposed to ultraviolet- and chlorine-treated seawater and maintained at 20,35 ppt salinity and 20 to 35°C. The dinoflagellate cells which cause Paralytic Shellfish Poisoning (PSP) were found to be more resilient than the bacterial cells. Ultraviolet treatment was found to be more effective than chlorine to both test organisms. Irreversible morphological changes in the treated dinoflagellate cells were noted, including protoplast discoloration, cellular membrane leakage and damage to the thecal armour. Conclusions:,The vegetative cells of both test organisms in seawater were more sensitive to ultraviolet treatment than to chlorine exposure. Generally, the dinoflagellate cells were less susceptible than bacterial cells to both disinfection treatments. Significance and Impact of the Study:,Results of this study may have significant implications in depuration procedures for molluscs and cleaning protocols for ballast waters of ships. [source]

A new player in the regulatory cascade controlling heterocyst differentiation in cyanobacteria

MOLECULAR MICROBIOLOGY, Issue 3 2010
Robert Haselkorn
Summary Heterocysts are terminally differentiated cells that fix nitrogen in filaments of the cyanobacterium Anabaena PCC 7120. They differentiate from vegetative cells at regular intervals along each filament. The developmental process is initiated by an increase in the ratio of reduced carbon to reduced nitrogen. This cue triggers protein NtcA to activate transcription of nrrA, which leads to transcription of the hetR gene. HetR is a master transcription factor required for expression of many heterocyst-specific genes. One such gene is hetP, shown by Higa and Callahan in this edition of Molecular Microbiology to be able to replace hetR for most of the downstream events required for a functional heterocyst. Ectopic production of HetP in a hetR mutant allows the differentiation of heterocysts. These heterocysts can fix nitrogen under anaerobic conditions but they are unable to provide wild-type protection of nitrogenase from oxygen, so they cannot bypass all of the duties of HetR. Additionally, the 5,-flanking region of the hetP gene provides the best-characterized binding site for the HetR protein so far, a seven-base pair inverted repeat. [source]

ABC-type amino acid uptake transporters Bgt and N-II of Anabaena sp. strain PCC 7120 share an ATPase subunit and are expressed in vegetative cells and heterocysts

MOLECULAR MICROBIOLOGY, Issue 5 2008
Rafael Pernil
Summary Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can fix N2 in differentiated cells called heterocysts. Anabaena open reading frames alr4167 and alr3187 encode, respectively, an ATPase subunit, BgtA, and a composite protein bearing periplasmic substrate-binding and transmembrane domains, BgtB, of an ABC-type high-affinity basic amino acid uptake transporter (Bgt). Open reading frame alr4167 is clustered with open reading frames alr4164, alr4165 and alr4166 that encode a periplasmic substrate-binding protein, NatF, and transmembrane proteins NatG and NatH respectively. The NatF, NatG, NatH and BgtA proteins constitute an ABC-type uptake transporter for acidic and neutral polar amino acids (N-II). The Bgt and N-II transport systems thus share the ATPase subunit, BgtA. These transporters together with the previously characterized ABC-type uptake transporter for proline and hydrophobic amino acids (N-I) account for more than 98% of the amino acid transport activity exhibited by Anabaena sp. strain PCC 7120. In contrast to N-I that is expressed only in vegetative cells, the Bgt and N-II systems are present in both vegetative cells and heterocysts. Whereas Bgt is dispensable for diazotrophic growth, N-II appears to contribute together with N-I to the diazotrophic physiology of this cyanobacterium. [source]

PrpJ, a PP2C-type protein phosphatase located on the plasma membrane, is involved in heterocyst maturation in the cyanobacterium Anabaena sp.

MOLECULAR MICROBIOLOGY, Issue 2 2007
PCC 7120
Summary Protein phosphatases play important roles in the regulation of cell growth, division and differentiation. The cyanobacterium Anabaena PCC 7120 is able to differentiate heterocysts specialized in nitrogen fixation. To protect the nitrogenase from inactivation by oxygen, heterocyst envelope possesses a layer of polysaccharide and a layer of glycolipids. In the present study, we characterized All1731 (PrpJ), a protein phosphatase from Anabaena PCC 7120. prpJ was constitutively expressed in both vegetative cells and heterocysts. Under diazotrophic conditions, the mutant ,prpJ (S20) did not grow, lacked only one of the two heterocyst glycolipids, and fragmented extensively at the junctions between developing cells and vegetative cells. No heterocyst glycolipid layer could be observed in the mutant by electron microscopy. The inactivation of prpJ affected the expression of hglEA and nifH, two genes necessary for the formation of the glycolipid layer of heterocysts and the nitrogenase respectively. PrpJ displayed a phosphatase activity characteristic of PP2C-type protein phosphatases, and was localized on the plasma membrane. The function of prpJ establishes a new control point for heterocyst maturation because it regulates the synthesis of only one of the two heterocyst glycolipids while all other genes so far analysed regulate the synthesis of both heterocyst glycolipids. [source]

Inactivation of patS and hetN causes lethal levels of heterocyst differentiation in the filamentous cyanobacterium Anabaena sp.

MOLECULAR MICROBIOLOGY, Issue 1 2005
PCC 7120
Summary In the filamentous cyanobacterium Anabaena sp. PCC 7120 patS and hetN suppress the differentiation of vegetative cells into nitrogen-fixing heterocysts to establish and maintain a pattern of single heterocysts separated by approximately 10 undifferentiated vegetative cells. Here we show that the patS - and hetN -dependent suppression pathways are the only major factors that prevent vegetative cells from differentiating into heterocysts when a source of ammonia is not present. The patS and hetN pathways are independent of each other, and inactivation of both patS and hetN leads to differentiation of almost all cells of a filament in the absence of a source of fixed nitrogen, compared with approximately 9% in the wild type. Complete differentiation of filaments also occurs when nitrate is supplied as a source of fixed nitrogen, conditions that do not induce differentiation of wild-type filaments. However, ammonia is still capable of suppressing differentiation. The percentage of cells that differentiate into heterocysts appears to be a function of time when a source of fixed nitrogen is absent or a function of growth phase when nitrate is supplied. Although differentiation proceeds unchecked in the absence of patS and hetN expression, differentiation is asynchronous and non-random. [source]