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Microbial Populations (microbial + population)
Kinds of Microbial Populations Terms modified by Microbial Populations Selected AbstractsQuality and Microbial Population of Cornish Game Hen Carcasses as Affected by Electron Beam IrradiationJOURNAL OF FOOD SCIENCE, Issue 7 2006C. Gomes ABSTRACT:, We evaluated the chemical and microbiological quality of Cornish game hen carcasses irradiated up to 7 kGy with a 10 MeV linear accelerator (dual beam configuration). Eighty frozen and vacuum packaged (approximately 0.45 kg) Cornish game hens (Gallus domesticus) were irradiated and stored in low-density polyethylene bags at 4 ± 1 °C for 21 d; nonirradiated chickens served as controls. Fat oxidation (in terms of malonaldehyde content) increased with storage time and dose for all chicken parts analyzed (breast, thigh, and skin). As expected, the skin had the highest level of fat oxidation while the breast samples had the lowest. Oxidation level in all samples exposed to 2 kGy reached a maximum on day 14. Sensory evaluation showed that irradiation caused significant textural toughening, and increased the redness of raw chicken meat. In terms of overall quality and aroma, lipid oxidation was not a major problem since it was not detected by the panelists. Irradiation significantly reduced the total viable microbial counts (TVC) in the breast and thigh samples. Exposure to 3-kGy dose decreased the TVC by 0.3-log cycles on the surface of the skin. In less than 14 d, the nonirradiated chicken carcasses had counts greater than 6 log CFU/50 cm2, while the 2 and 3 kGy irradiated samples reached these numbers only after 21 d of storage. Samples irradiated at 7 kGy had consistently the lowest counts (2.5 log CFU/50 cm2) throughout storage time. This study shows that irradiation up to 7 kGy and refrigerated storage (4 °C) inhibits microbial growth and extends shelf life of Cornish game hens without affecting consumers' acceptability. [source] The effect of gamma irradiation on the microbial load, mineral concentration and sensory characteristics of liquorice (Glycyrrhiza glabra L)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2003Mahfouz Al-Bachir Abstract Ground liquorice roots were exposed to various doses (0, 5, 10, 15 and 20,kGy) of gamma radiation from a 60Co source. Irradiated and non-irradiated samples were stored at room temperature. Microbial population, viscosity, concentrations of some minerals and the sensory properties of the extracts were evaluated after 0 and 12 months of storage. Tests carried out immediately after irradiation showed that the microbial count had been reduced and that the dose required to reduce the count by 1 log cycle (D10) was about 2,kGy. No effect was observed on the total dissolved solids in extracts of liquorice roots. Glycyrrhizinic acid concentration in the extracts and the viscosities of suspensions produced from irradiated roots were lower than those from non-irradiated ones. Sensory evaluation indicated that there were no significant differences (P,<,0.05) in colour, taste or flavour between extracts produced from irradiated and non-irradiated roots. However, after 12 months of storage, some mineral ion (Na+, Ca2+ and K+) concentrations in extracts produced from irradiated roots were lower than in those from non-irradiated ones; no significant differences (P,<,0.05) in viscosity were found between suspensions of irradiated and non-irradiated roots. © 2002 Society of Chemical Industry [source] Shelf Life of Leafy Vegetables Treated with Natural Essential OilsJOURNAL OF FOOD SCIENCE, Issue 2 2004A.G. Ponce ABSTRACT: Essential oils as natural sanitizing agents were sprayed on Swiss chard leaves produced by organic methods. Samples were stored at 0 and 5°C and 97% to 98% relative humidity. Microbial populations, peroxidase activity, and sensory attributes were monitored during storage. No significant differences were observed between treated and control samples stored at 0°C. However, samples treated with the essential oils of eucalyptus, tea tree, and clove and stored at 5°C presented microbial counts significantly lower than those of control samples. The essential oils of eucalyptus, tea tree, lemon, rosemary, and clove presented peroxidase activity inhibition that, in the case of eucalyptus, increased to 65% during storage. Although some of the essential oils did appear to reduce microbial counts and peroxidase activity compared with controls, they were not effective in extending the shelflife of the Swiss chard leaves from a sensory point of view. [source] Stationary phase mutagenesis: mechanisms that accelerate adaptation of microbial populations under environmental stressENVIRONMENTAL MICROBIOLOGY, Issue 10 2003Maia Kivisaar Summary Microorganisms are exposed to constantly changing environmental conditions. In a growth-restricting environment (e.g. during starvation), mutants arise that are able to take over the population by a process known as stationary phase mutation. Genetic adaptation of a microbial population under environmental stress involves mechanisms that lead to an elevated mutation rate. Under stressful conditions, DNA synthesis may become more erroneous because of the induction of error-prone DNA polymerases, resulting in a situation in which DNA repair systems are unable to cope with increasing amounts of DNA lesions. Transposition may also increase genetic variation. One may ask whether the rate of mutation under stressful conditions is elevated as a result of malfunctioning of systems responsible for accuracy or are there specific mechanisms that regulate the rate of mutations under stress. Evidence for the presence of mutagenic pathways that have probably been evolved to control the mutation rate in a cell will be discussed. [source] Effect of sorption and desorption resistance on aerobic trichloroethylene biodegradation in soilsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2002Sangjin Lee Abstract Biodegradation of trichloroethylene(TCE) by toluene-degrading bacteria was measured under aerobic conditions in aqueous and soil-slurry batch microcosms. For soil-phase experiments, a freshly contaminated soil and a soil containing only the desorption-resistant fraction of TCE were tested. In both cases, presence of soil resulted in biodegradation rates substantially lower than those determined in the absence of soil. In aqueous-phase experiments, an appreciable increase in the rate and extent of TCE biodegradation was observed in microcosms when toluene was added multiple times. The TCE degradation rates were clearly correlated with toluene dioxygenase (TOD) enzyme activity over time, thus providing an indication of the cometabolic pathway employed by the microbial population. In soil-slurry experiments containing freshly contaminated soil, a TCE degradation rate of approximately 150 ,g TCE/kg/h was observed during the first 39-h period, and then the TCE degradation rate slowed considerably to 0.59 and 0.84 ,g TCE/kg/h for microcosms receiving one and two additions of toluene, respectively. The TCE degradation rates in soil-slurry microcosms containing the desorption-resistant fraction of TCE-contaminated soil were approximately 0.27 and 0.32 ,g TCE/kg/h in microcosms receiving one and two additions of toluene, respectively. It is clear from these results that mass transfer into the aqueous phase limited bioavailability of TCE in the contaminated soil. [source] Contribution of ethylamine degrading bacteria to atrazine degradation in soilsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2006Daniel Smith Abstract Bacterial communities that cooperatively degrade atrazine commonly consist of diverse species in which the genes for atrazine dechlorination and dealkylation are variously distributed among different species. Normally, the first step in degradation of atrazine involves dechlorination mediated by atzA, followed by stepwise dealkylation to yield either N -ethylammelide or N -isopropylammelide. As the liberated alkylamine moieties are constituents of many organic molecules other than atrazine, it is possible that a large number of alkylamine-degrading bacteria other than those previously described might contribute to this key step in atrazine degradation. To examine this hypothesis, we isolated 82 bacterial strains from soil by plating soil water extracts on agar media with ethylamine as a sole carbon source. Among the relatively large number of isolates, only 3 were able to degrade N -ethylammelide, and in each case were shown to carry the atzB gene and atzC genes. The isolates, identified as Rhizobium leguminosarum, Flavobacterium sp., and Arthrobacter sp., were all readily substituted into an atrazine-degrading consortium to carry out N -ethylammelide degradation. The distribution of these genes among many different species in the soil microbial population suggests that these genes are highly mobile and over time may lead to generation of various atrazine-degrading consortia. [source] Field-scale 13C-labeling of phospholipid fatty acids (PLFA) and dissolved inorganic carbon: tracing acetate assimilation and mineralization in a petroleum hydrocarbon-contaminated aquiferFEMS MICROBIOLOGY ECOLOGY, Issue 3 2002Silvina A. Pombo Abstract This study was conducted to determine the feasibility of labeling phospholipid-derived fatty acids (PLFA) of an active microbial population with a 13C-labeled organic substrate in the denitrifying zone of a petroleum hydrocarbon-contaminated aquifer during a single-well push-pull test. Anoxic test solution was prepared from 500 l of groundwater with addition of 0.5 mM Br, as a conservative tracer, 0.5 mM NO3,, and 0.25 mM [2- 13C]acetate. At 4, 23 and 46 h after injection, 1000 l of test solution/groundwater mixture were sequentially extracted. During injection and extraction phases we measured Br,, NO3, and acetate concentrations, characterized the microbial community structure by PLFA and fluorescent in situ hybridization (FISH) analyses, and determined 13C/12C ratios in dissolved inorganic carbon (DIC) and PLFA. Computed first-order rate coefficients were 0.63±0.08 day,1 for NO3, and 0.70±0.05 day,1 for acetate consumption. Significant 13C incorporation in DIC and PLFA was detected as early as 4 h after injection. At 46 h we measured ,13C values of up to 5614, in certain PLFA (especially monounsaturated fatty acids), and up to 59.8, in extracted DIC. Profiles of enriched PLFA and FISH analysis suggested the presence of active denitrifiers. Our results demonstrate the applicability of 13C labeling of PLFA and DIC in combination with FISH to link microbial structure and activities at the field scale during a push-pull test. [source] Effects of CO2 absorbent and high-pressure treatment on the shelf-life of packaged Kimchi productsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2003Joo W. Lee Summary The effects on extending the shelf-life of commercial Kimchi products and preventing pouch inflation by absorbing CO2 with calcium hydroxide, were compared with a treatment using high-hydrostatic pressure. The changes in the quality factors of Kimchi, such as CO2 accumulation in the headspace of the pouch, pH, total acidity and the microbial population of both total viable cells and lactic acid bacteria were measured during storage for 24 days at 10 °C. Pressurization at 400 and 600 MPa for 5 min at 20 °C were both effective in preventing inflation of the Kimchi pouches during storage at 10 °C, as was CO2 absorption at the level of 0.5 g CO2 absorbent per 80 g Kimchi. [source] A review of modified atmosphere packaging of fish and fishery products , significance of microbial growth, activities and safetyINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2002Morten Sivertsvik Modified atmosphere packaging (MAP) extends shelf-life of most fishery products by inhibiting bacterial growth and oxidative reactions. The achievable extension of shelf-life depends on species, fat content, initial microbial population, gas mixture, the ratio of gas volume to product volume, and most importantly, storage temperature. The shelf-life of fishery products is usually limited by microbial activity, although for some fatty fishes or at superchilled storage, it can be limited by nonmicrobial activity. Packaging of fishery products under modified atmospheres (MA) increases shelf-life compared with those packaged under air, but confers little or no additional shelf-life increase compared with vacuum packaging. The specific spoilage organism (SSO) of MA packaged cod at 0 °C has been found to be Photobacterium phosphoreum. Whether or not this bacterium is the general SSO for all marine temperate fishes at different storage temperatures and under various CO2/N2/O2 mixtures needs to be resolved. Without proper control of storage temperature, the benefits of MAP may be lost. Higher temperatures inevitably lead to less dissolved CO2 in the product and consequently loss of inhibitory effect, which may result in higher microbial and enzymatic activity, and uncertainties concerning the microbial safety, as food-borne pathogens might be present in the product. [source] The model of fungal population dynamics affected by nystatinINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010Sergei I. Voychuk Abstract Fungal diseases are acute problems of the up-to-day medicine. Significant increase of resistance of microorganisms to the medically used antibiotics and a lack of new effective drugs follows in a growth of dosage of existing chemicals to solve the problem. Quite often such approach results in side effects on humans. Detailed study of fungi-antibiotic dynamics can identify new mechanisms and bring new ideas to overcome the microbial resistance with a lower dosage of antibiotics. In this study, the dynamics of the microbial population under antibiotic treatment was investigated. The effects of nystatin on the population of Saccharomyces cerevisiae yeasts were used as a model system. Nystatin effects were investigated both in liquid and solid media by viability tests. Dependence of nystatin action on osmotic gradient was evaluated in NaCl solutions. Influences of glucose and yeast extract were additionally analyzed. A "stepwise" pattern of the cell death caused by nystatin was the most intriguing. This pattern manifested in periodical changes of the stages of cell death against stages of resistance to the antibiotic. The mathematical model was proposed to describe cell-antibiotic interactions and nystatin viability effects in the liquid medium. The model implies that antibiotic ability to cause a cells death is significantly affected by the intracellular compounds, which came out of cells after their osmotic barriers were damaged © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Microbial population profiles of the microflora associated with pre- and postharvest tomatoes contaminated with Salmonella typhimurium or Salmonella montevideoJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009X Shi Abstract Aims:, To determine the microflora profiles of pre- and postharvest tomatoes contaminated with Salmonella montevideo or S. typhimurium DT104. Methods and Results:,Salmonella montevideo or S. typhimurium was inoculated onto the flowers of tomato plants with the microflora of the subsequent fruit examined using a combination of Source Carbon Utilization and 16S rDNA-PCR profiling. From 16S rDNA profiles it was evident that tomatoes derived from Salmonella inoculated plants harboured a different microbial population compared to nontreated controls. The same result was observed for tomatoes inoculated at postharvest and subsequently stored for 14 days at 15°C. From sequencing analysis it was found that tomatoes derived from Salmonella inoculated plants but testing negative for the enteric pathogen, frequently harboured Enterobacter and Bacillus spp. In contrast, both bacterial types were not found associated with tomatoes testing positive for Salmonella. Conclusions:,Salmonella introduced onto tomatoes at pre- or postharvest alters the composition of the microbial community. The presence of Enterobacter and Bacillus spp negatively affects the persistence of Salmonella on preharvest tomatoes. Significance and Impact of the Study:,Salmonella appears to modify rather than become integrated into the microbial communities associated with tomatoes. Yet, the presence of antagonistic bacteria appears to reduce the persistence of the enteric pathogen. [source] Hydrolysis and microbial community analyses in two-stage anaerobic digestion of energy cropsJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007D.G. Cirne Abstract Aims:, The roles of the diverse populations of micro-organisms responsible for biodegradation of organic matter to form methane and carbon dioxide are rudimentarily understood. To expand the knowledge on links between microbial communities and the rate limiting, hydrolytic stage of two-stage biogas production from energy crops, this study was performed. Methods and Results:, The process performance and microbial communities (as determined by fluorescence in situ hybridization) in two separate two-stage batch digestions of sugar beets and grass/clover were studied. The microbial populations developed in the hydrolytic stage of anaerobic digestion of beets and grass/clover showed very few similarities, despite that the hydrolysis dynamics were similar. In both substrates, the solubilization of organic material was rapid for the first 10 days and accompanied by a build-up of volatile fatty acids (VFAs) and lactate. Between days 10 and 15, VFA and lactate concentrations decreased, as did the solubilization rates. For both substrates, Archaea started to appear in the hydrolytic stage between days 10 and 15, and the fraction of Bacteria decreased. The major bacterial group detected in the leachate fraction for beets was Alphaproteobacteria, whereas for grass/clover it was Firmicutes. The number of cells that bound to probes specifically targeting bacteria with cellulolytic activity was higher in the digestion of grass than in the digestion of beet. Conclusions:, This study allowed the identification of the general bacterial groups involved, and the identification of a clear shift in the microbial population when hydrolysis rate became limiting for each of the substrates investigated. Significance and Impact of the Study:, The findings from this study could be considered as a first step towards the development of strategies to stimulate hydrolysis further and ultimately increasing the methane production rates and yields from reactor-based digestion of these substrates. [source] Low temperature bioremediation of oil-contaminated soil using biostimulation and bioaugmentation with a Pseudomonas sp. from maritime AntarcticaJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2005B. Stallwood Abstract Aims:, To identify native Antarctic bacteria capable of oil degradation at low temperatures. Methods and Results:, Oil contaminated and pristine soils from Signy Island (South Orkney Islands, Antarctica) were examined for bacteria capable of oil degradation at low temperatures. Of the 300 isolates cultured, Pseudomonas strain ST41 grew on the widest range of hydrocarbons at 4°C. ST41 was used in microcosm studies of low temperature bioremediation of oil-contaminated soils. Microcosm experiments showed that at 4°C the levels of oil degradation increased, relative to the controls, with (i) the addition of ST41 to the existing soil microbial population (bioaugmentation), (ii) the addition of nutrients (biostimulation) and to the greatest extent with (iii) a combination of both treatments (bioaugmentation and biostimulation). Addition of water to oil contaminated soil (hydration) also enhanced oil degradation, although less than the other treatments. Analysis of the dominant species in the microcosms after 12 weeks, using temporal temperature gradient gel electrophoresis, showed Pseudomonas species to be the dominant soil bacteria in both bioaugmented and biostimulated microcosms. Conclusions:, Addition of water and nutrients may enhance oil degradation through the biostimulation of indigenous oil-degrading microbial populations within the soil. However, bioaugmentation with Antarctic bacteria capable of efficient low temperature hydrocarbon degradation may enhance the rate of bioremediation if applied soon after the spill. Significance and Impact of the Study:, In the future, native soil bacteria could be of use in bioremediation technologies in Antarctica. [source] Genotypic and phenotypic heterogeneity among lactococci isolated from traditional Pecorino Sardo cheeseJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2000L. Mannu Twenty-nine Lactococcus lactis isolates from one traditional 24 h-old Pecorino Sardo cheese were characterized phenotypically, technologically and genotypically in order to assess the biodiversity within this wild microbial population. Two DNA-based techniques, plasmid profiling and PFGE, were used for the genetic typing of the isolates. All 29 isolates were characterized at strain level and eight different genotypes were recognized. In addition, by combining the results from plasmid profile analysis and PFGE, it was possible to identify closely related isolates probably belonging to the same clonal lineage. The dominant biotype was identified in the 24 h-old cheese, as were the strains believed to act as starters for the curd. Atypical lactococci, able to grow in 6·5% NaCl, were isolated. The results suggest that wild bacterial populations should be preserved in order to protect the traditional raw milk cheeses, and to select new starter strains for the dairy industry. [source] Evolution of a degradative bacterial consortium during the enrichment of naphtha solventJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2000L. Cavalca A microbial mixed culture able to degrade naphtha solvent, a model of hydrocarbon aromatic mixture, was isolated from a hydrocarbon-polluted soil. Composition of the population was monitored by phenotypic and molecular methods applied on soil DNA, on whole enrichment culture DNA, and on 85 isolated strains. Strains were characterized for their 16S rDNA restriction profiles and for their random amplified polymorphic DNA profiles. Catabolic capabilities were monitored by phenotypic traits and by PCR assays for the presence of the catabolic genes methyl mono-oxygenase ( xylA,M), catechol 2,3 dioxygenase (xylE) and toluene dioxygenase (todC1) of TOL and TOD pathways. Different haplotypes belonging to Pseudomonas putida, Ps. aureofaciens and Ps. aeruginosa were found to degrade aromatic compounds and naphtha solvent. The intrinsic catabolic activity of the microbial population of the polluted site was detected by PCR amplification of the xylE gene directly from soil DNA. [source] Storage of biodegradable polymers by an enriched microbial community in a sequencing batch reactor operated at high organic load rateJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2005Davide Dionisi Abstract The production of polyhydroxyalkanoates (PHAs) from organic acids by mixed bacterial cultures using a process based on aerobic enrichment of activated sludge, that selects for mixed microbial cultures able to store PHAs at high rates and yields, is described. Enrichment resulted from the selective pressure established by periodic feeding the carbon source in a sequencing batch reactor (SBR); a mixture of acetic, lactic and propionic acids was fed at high frequency (2 hourly), high dilution rate (1 d,1), and at high organic load rate (12.75 g chemical oxygen demand (COD) L,1 d,1). The performance of the SBR was assessed by microbial biomass and PHA production as well as the composition and polymer content of the biomass. A final batch stage was used to increase the polymer concentration of the excess sludge produced in the SBR and in which the behaviour of the biomass was investigated by determining PHA production rates and yields. The microbial biomass selected in the SBR produced PHAs at high rate [278 mg PHAs (as COD) g biomass (as COD),1 h,1, with a yield of 0.39 mg PHAs (as COD) mg removed substrates (as COD),1], reaching a polymer content higher than 50% (on a COD basis). The stored polymer was the copolymer poly(3-hydroxybutyrate/3-hydroxyvalerate) [P(HB/HV)], with an HV fraction of 18% mol mol,1. The microbial community selected in the SBR was analysed by DGGE (denaturing gradient gel electrophoresis). The operating conditions of the SBR were shown to select for a restricted microbial population which appeared quite different in terms of composition with respect to the initial microbial cenosis in the activated sludge used as inoculum. On the basis of the sequencing of the major bands in the DGGE profiles, four main genera were identified: a Methylobacteriaceae bacterium, Flavobacterium sp, Candidatus Meganema perideroedes, and Thauera sp. The effects of nitrogen depletion (ie absence of growth) and pH variation were also investigated in the batch stage and compared with the SBR operative mode. Absence of growth did not stimulate higher PHA production, so indicating that the periodic feed regime fully exploited the storage potential of the enriched culture. Polymer production rates remained high between pH 6.5 and 9.5, whereas the HV content in the stored polymer strongly increased as the pH value increased. This study shows that polymer composition in the final batch stage can readily be controlled independently from the feed composition in the SBR. Copyright © 2005 Society of Chemical Industry [source] Effect of a chemical synthesis-based pharmaceutical wastewater on performance, acetoclastic methanogenic activity and microbial population in an upflow anaerobic filterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2002B Kasapgil Ince Abstract The performance of an upflow anaerobic filter (UAF) treating a chemical synthesis-based pharmaceutical wastewater was evaluated under various operating conditions. During start-up, the UAF was initially fed by glucose till an organic loading rate (OLR) of approximately 7.5,kg COD m,3 day,1 with a hydraulic retention time of 2.3 days. A soluble COD removal efficiency of 98% was achieved before the addition of the wastewater. Initially, the filter inertia was acclimatized to the wastewater by sequential feeding of 10% (w/v), 30% (w/v) and 70% (w/v) of the pre-aerated wastewater mixed with glucose followed by a 100% (w/v) pre-aerated wastewater. During the operation, the COD removal efficiency and methane yield decreased to 75% and 0.30,m3 CH4,kg,1 CODremoved respectively. As the UAF became accustomed to the pre-aerated wastewater, raw wastewater was fed in increasing ratios of 20% (w/v), 60% (w/v) and 80% (w/v) with the pre-aerated wastewater as the remaining part. During this stage of the operation, a COD removal efficiency in a range of 77,86% was achieved and the methane yield decreased to 0.24,m3 CH4,kg,1 CODremoved. Finally, 100% (w/v) raw wastewater was fed and a COD removal efficiency of 65% was achieved with a methane yield of 0.20,m3 CH4,kg,1 CODremoved. At the end of the operation, acetoclastic methanogenic activity was only measured in the bottom section of the UAF, this showed a 90% reduction in comparison with activity of inoculation sludge. Microscopic examinations revealed that rod-shaped methanogens remained as the dominant species whereas Methanosarcina -like species and filaments were present only in insignificant numbers along the UAF. © 2002 Society of Chemical Industry [source] Effect of Hot Water Surface Pasteurization of Whole Fruit on Shelf Life and Quality of Fresh-Cut CantaloupeJOURNAL OF FOOD SCIENCE, Issue 3 2008X. Fan ABSTRACT:, Cantaloupes are associated with recent outbreaks of foodborne illnesses and recalls. Therefore, new approaches are needed for sanitization of whole and cut fruit. In the present study, whole cantaloupes were submerged into water in the following 3 conditions: 10 °C water for 20 min (control), 20 ppm chlorine at 10 °C for 20 min, and 76 °C water for 3 min. Populations of microflora were measured on the rinds of the whole cantaloupes. Quality and microbial populations of fresh-cut cantaloupes prepared from whole fruit were analyzed after 1, 6, 8, 10, 13, 16, and 20 d of storage at 4 °C. The hot water significantly reduced both total plate count (TPC) and yeast and mold count on rind of whole fruits while chlorine or cold water wash did not result in a significant reduction of microbial population. Fresh-cut pieces prepared from hot water-treated cantaloupes had lower TPC than the other 2 treatments in the later storage periods (days 13 to 20) in 2 of 3 trials. The hot water treatment of whole fruits was inconsistent in reducing yeast and mold count of fresh-cut pieces. Soluble solids content, ascorbic acid content, fluid loss, and aroma and appearance scores were not consistently affected by either hot water or chlorine treatment. Our results suggested that hot water pasteurization of whole cantaloupes frequently resulted in lower TPCs of fresh-cut fruit during storage and did not negatively affect quality of fresh-cut cantaloupes. [source] Antimicrobial resistance in livestockJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2003B. Catry Antimicrobial resistance may become a major problem in veterinary medicine as a consequence of the intensive use and misuse of antimicrobial drugs. Related problems are now arising in human medicine, such as the appearance of multi-resistant food-borne pathogens. Product characteristics, dose, treatment interval and duration of treatment influence the selection pressure for antimicrobial drug resistance. There are theoretical, experimental and clinical indications that the emergence of de novo resistance in a pathogenic population can be prevented by minimizing the time that suboptimal drug levels are present in the infected tissue compartment. Until recently, attention has been focused on target pathogens. However, it should be kept in mind that when antimicrobial drugs are used in an individual, resistance selection mainly affects the normal body flora. In the long term, this is at least equally important as resistance selection in the target pathogens, as the horizontal transfer of resistance genes converts almost all pathogenic bacteria into potential recipients for antimicrobial resistance. Other factors contributing to the epidemiology of antimicrobial resistance are the localization and size of the microbial population, and the age, immunity and contact intensity of the host. In livestock, dynamic herd-related resistance patterns have been observed in different animal species. [source] The digestive tract and life history of small mammalsMAMMAL REVIEW, Issue 2 2002PETER LANGER ABSTRACT The type of food, differentiation of the large intestine and stomach, and methane production, as well as life history data, are considered in Insectivora, Rodentia and Lagomorpha. When food containing plant cell wall material is eaten, there is either a differentiation of the stomach or the large intestine. In animals with low body mass and little differentiation of the gastrointestinal tract, methane production is low, but structures essential for microbial digestion of plant cell wall material, such as haustration of the colon or formation of a caecum, can be found in many methane-producers. Animals with a body mass < 500 g and a weaning time < 20 days are non-producers of methane. Establishment of a balanced microbial population in the gastrointestinal tract requires some time. Many non-producers of methane wean their young in < 10 days, but many producers need > 50 days for the weaning process. Caviomorpha, Thryonomyidae and Hystricidae seem to have ,opened the door' to the use of low quality food by microbial fermentation, but some of them have to ,pay' for this extension of the food range by an extended weaning period, which also means an extended dependency on the mother. [source] Structural alterations in a type IV pilus subunit protein result in concurrent defects in multicellular behaviour and adherence to host tissueMOLECULAR MICROBIOLOGY, Issue 2 2001Hae-Sun Moon Park The ability of bacteria to establish complex communities on surfaces is believed to require both bacterial,substratum and bacterial,bacterial interactions, and type IV pili appear to play a critical but incompletely defined role in both these processes. Using the human pathogen Neisseria gonorrhoeae, spontaneous mutants defective in bacterial self-aggregative behaviour but quantitatively unaltered in pilus fibre expression were isolated by a unique selective scheme. The mutants, carrying single amino acid substitutions within the conserved amino-terminal domain of the pilus fibre subunit, were reduced in the ability to adhere to a human epithelial cell line. Co-expression of the altered alleles in the context of a wild-type pilE gene confirmed that they were dominant negative with respect to aggregation and human cell adherence. Strains expressing two copies of the altered alleles produced twice as much purifiable pili but retained the aggregative and adherence defects. Finally, the defects in aggregative behaviour and adherence of each of the mutants were suppressed by a loss-of-function mutation in the twitching motility gene pilT. The correlations between self-aggregation and the net capacity of the microbial population to adhere efficiently demonstrates the potential significance of bacterial cell,cell interactions to colonization. [source] Effect of chitosan coating and vacuum packaging on the quality of refrigerated grilled porkPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2006Songchai Yingyuad Abstract The effects of chitosan coating and vacuum packaging on the quality and shelf-life of retail packaged grilled pork in a PVDC/nylon pouch during refrigerated storage at 2 ± 1°C were investigated. Grilled pork without chitosan coating and packaged in 100% air was used as the control sample. Firmness, pH, colour, peroxide values, microbial population and shelf-life (as determined by sensory characteristics) of the samples were determined during the storage. The results showed that colour, peroxide values and microbial population coincided with sensory characteristics. The delayed growth of microbes in vacuum packaging can be attributed to inhibition by low levels of O2. Chitosan coating was shown to minimize oxidation, as reflected by the peroxide values, colour changes and microbial counts of the samples. Vacuum-packaged chitosan-coated grilled pork showed negligible microbial growth and was found to be organoleptically acceptable throughout the storage period. Chitosan coating along with vacuum packaging provided a type of active packaging to maintain quality and extend the shelf-life of grilled pork. Copyright © 2006 John Wiley & Sons, Ltd. [source] Agronomic and environmental implications of enhanced s -triazine degradationPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2010L Jason Krutz Abstract Novel catabolic pathways enabling rapid detoxification of s -triazine herbicides have been elucidated and detected at a growing number of locations. The genes responsible for s -triazine mineralization, i.e. atzABCDEF and trzNDF, occur in at least four bacterial phyla and are implicated in the development of enhanced degradation in agricultural soils from all continents except Antarctica. Enhanced degradation occurs in at least nine crops and six crop rotation systems that rely on s -triazine herbicides for weed control, and, with the exception of acidic soil conditions and s -triazine application frequency, adaptation of the microbial population is independent of soil physiochemical properties and cultural management practices. From an agronomic perspective, residual weed control could be reduced tenfold in s -triazine-adapted relative to non-adapted soils. From an environmental standpoint, the off-site loss of total s -triazine residues could be overestimated 13-fold in adapted soils if altered persistence estimates and metabolic pathways are not reflected in fate and transport models. Empirical models requiring soil pH and s -triazine use history as input parameters predict atrazine persistence more accurately than historical estimates, thereby allowing practitioners to adjust weed control strategies and model input values when warranted. Published in 2010 by John Wiley & Sons, Ltd. [source] The effect of incorporating straw or manure into the soil on the natural microflora of winter wheatPLANT PATHOLOGY, Issue 5 2001B. S. Rodgers-Gray Over 3 years, five crops of winter wheat with different fertilization or pesticide treatments were grown in replicated plots in which straw, cattle manure or nothing was incorporated into the soil. It was previously shown that severities of several foliar diseases were reduced by the treatment with straw. Treatments with straw slightly increased leaf microbial numbers at growth stage (GS) 10, and significantly but slightly decreased numbers at GS 60 and 70, when averaged over all crops. There was no evidence of differences in potential for biological control between plots, because no differences were demonstrated between treatments in the proportion of phylloplane residents able to produce chitinase, siderophores or antibiotics. There was no link between soil and leaf nitrogen and microbial populations or soil amendment. The two youngest leaves of straw-treated plants remained green longer than leaves from untreated or manure-treated plants. Microbial numbers differed between crops, but within crops were more stable on leaves and ears than in soil. Soil populations were larger before the crops were sown. Bacteria predominated over fungi in all habitats throughout the growing season. The ratio of Gram-negative to Gram-positive bacteria recovered was similar on leaves and in soil, but not on ears. Soil and leaf microbes utilized similar carbon sources. More leaf epiphytes than soil microbes produced siderophores. The majority of identified organisms belonged to only a few species. Chromogenic organisms were more abundant on aerial surfaces. A fungicide, chlorothalonil, was applied in one crop; it reduced the microbial population but did not alter its composition (without affecting the reduction in disease due to straw). It is postulated that straw acts in the field by altering plant physiology and thus altering both microbial colonization and disease. [source] Baboon vaginal microbiota: an overlooked aspect of primate physiologyAMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2010Angel J. Rivera Abstract The bacterial population of the primate vaginal canal is an infant primate's first exposure to the microbial population inhabiting the outside world. Yet, little is known about this population and the effect it might have on the development and survival of the infant primate. As a first step toward characterizing the vaginal microbiota of a nonhuman primate, we used denaturing gradient gel electrophoresis to evaluate variations in the vaginal microbiota of a group of 35 baboons (Papio hamadryas), which were housed in a facility where they shared the same diet and the same environmental conditions. We found that, despite the uniform environment, there were appreciable differences in the composition of the microbiota from one individual to another. Our results also indicate that a simple swab test is sufficient for sampling the vaginal microbiota in the field, a finding that should help make more detailed characterization of the microbiota of wild primates feasible in the future. Am. J. Primatol. 72:467,474, 2010. © 2010 Wiley-Liss, Inc. [source] Associative effects of supplementing rice straw-based diet with cornstarch on intake, digestion, rumen microbes and growth performance of Huzhou lambsANIMAL SCIENCE JOURNAL, Issue 2 2010Xian-Dong ZHANG ABSTRACT Thirty-six male Hu lambs consuming a rice straw-based diet were used in a 60-day trial to study the associative effects of cornstarch supplementation on intake, digestion, ruminal microbial population and growth performance. All animals were fed rice straw ad libitum together with 160 g/day of rapeseed meal and supplemented with cornstarch at levels of 0 (control), 60, 120 or 180 g/day, respectively. Increment of supplementary cornstarch showed little influence on rice straw intake. Optimal growth performance and highest apparent digestibility of organic matter was achieved in the 120 g/day cornstarch group (P < 0.05), while the digestibilities of neutral detergent fiber and crude protein were significantly decreased by 180 g/day cornstarch (P < 0.05). Similar results were observed for carboxymethyl cellulose activity and relative populations of cellulolytic bacteria (Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogene). Blood urea nitrogen was reduced by supplementary cornstarch, indicating enhanced protein utilization efficiency. Carcass traits were all significantly improved by supplementary cornstarch. These results suggested that proper amounts of starch supplementation (within 0.5% BW) has little adverse effect on forage utilization, but could effectively improve growth performance. High levels of cornstarch, however, would decrease cellulase activity and populations of cellulolytic bacteria, and hence the digestibility of forage. [source] Effect of administration of acid- and bile-tolerant lactobacilli on pigs intestinal microbial populationANIMAL SCIENCE JOURNAL, Issue 6 2002Makoto OTSUKA ABSTRACT The effects of the administration of four Lactobacillus strains as probiotics on the constitution of microbial populations in the intestine of pigs were investigated by using a litter of pigs. The experimental group was fed a diet blended with the freeze-dried powder containing lactobacilli at a concentration of 0.2% (W/W). After 4 weeks of probiotics administration, the total viable count of anaerobes in the feces was not significantly different between the pigs fed a diet supplemented with probiotics and the pigs given the non-supplemented diet. However, viable counts of eubacteria were significantly higher (P < 0.01) in the feces of pigs fed a diet supplemented with probiotics than in the pigs given the non-supplemented diet. Conversely, viable counts of clostridia were significantly lower (P < 0.01) in the feces of pigs fed a diet supplemented with probiotics than the pigs given the non-supplemented diet. The total volatile fatty acid concentrations in the feces of pigs that were given a diet supplemented with probiotics were significantly lower (P < 0.05) than those given the non-supplemented diet. Further, the molar proportion of n-butyric acids in the feces of pigs that were given a diet supplemented with probiotics, was significantly lower (P < 0.05) than those given the non-supplemented diet. [source] Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) I. Effects on growth performance, feed utilization, intestinal microbiota and related health criteriaAQUACULTURE NUTRITION, Issue 5 2010D.L. MERRIFIELD Abstract The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) used singularly and synergistically on the growth performance, intestinal microbiota and health status of rainbow trout (Oncorhynchus mykiss Walbaum) were assessed after 10 weeks feeding on supplemented diets. No significant improvements of weight gain or specific growth rate were observed in the probiotic fed groups. However, a significant improvement of feed conversion ratio was observed in the group fed E. faecium. High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta-associated populations and potentially resident mucosal populations. Bacillus subtilis and B. licheniformis levels accounted for 36% of the total culturable microbial population adhered to the mucosa and 62% in the digesta. E. faecium levels accounted for 45% of the mucosal population and 89% of the population in the digesta. An increase of serum lysozyme activity was observed in the fish fed diets containing the Bacillus probionts and elevated leukocyte levels were observed in fish fed diets containing Bacillus + E. faecium synergistically. The results of the current study demonstrate potential for B. subtilis, B. licheniformis and E. faecium to improve feed utilization, modulate intestinal microbiota and the health status of rainbow trout. [source] Growth, digestive capacity and intestinal microflora of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary inositolAQUACULTURE RESEARCH, Issue 8 2009Wei-Dan Jiang Abstract A 60-day feeding trial was carried out with juvenile Jian carp (Cyprinus carpio var. Jian) to study the effects of myo -inositol (MI) on the growth, digestive enzyme and intestinal microbial population. Diets with seven levels of inositol (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg MI kg,1 diet) were fed to Jian carp (initial weight 22.28±0.07 g). Per cent weight gain (PWG) was improved with increasing inositol levels up to 535.8 mg MI kg,1 diet (P<0.05), and plateaued (P>0.05). The protein production value, lipid production value and ash production value were increased with increasing dietary inositol levels up to 384.2, 838.8 and 838.8 mg MI kg,1 diet respectively (P<0.05). Although intestinal protein content and trypsin activity were not affected by inositol levels (P>0.05), chymotrypsin, lipase and amylase activities in intestine were the lowest for fish fed the MI-unsupplemented diet (P<0.05). Alkaline phosphatase, Na+, K+ -ATPase, ,-glutamyl transpeptidase and creatinkinase activities in the intestine were increased with an increase in the inositol levels up to 384.2,687.3 mg MI kg,1 diet (P<0.05). Intestinal Aeromonas hydrophila and Escherichia coli decreased with an increase in the levels of dietary inositol up to 232.7 and 687.3 mg MI kg,1 diet respectively (P<0.05), while Lactobacillus in the intestine increased with an increase in inositol levels up to 990.3 mg MI kg,1 diet (P<0.05). In conclusion, inositol improved growth, digestive capacity and intestinal microbial population of juvenile Jian carp, and the dietary inositol requirement for PWG of juvenile Jian carp is 518.0 mg MI kg,1 diet. [source] Calculation of the Specific Rate of Catabolic Activity (Ac) from the Heat Flow Rate of Soil Microbial Reactions Measured by Calorimetry: Significance and ApplicationsCHEMISTRY & BIODIVERSITY, Issue 10 2004Nieves Barros The calculation of parameters involved in the kinetics of the microbial soil reactions linked to the carbon cycle is strongly limited by the methodologies employed. Hence, a mathematical model is proposed to quantify easily the specific rate of catabolic activity Ac by microcalorimetry based on Belaich's model. It permits to quantify Ac from the plots of the heat flow rate vs. time recorded from soil samples amended with glucose. It was applied for several soil samples collected in the Amazon. The results obtained were compared, and statistical and graphical analyses were used to provide the biophysical significance of Ac in soils. Results suggest that Ac could be used as an empirical measure of stress. It correlates positively with the heat yield, YQ/X, of the soil microbial growth reactions, indicating that higher specific rates of catabolic activity cause higher dissipation of energy per unit of cell, yielding less-efficient metabolic reactions, which could affect negatively the soil quality. It is strongly affected by the initial microbial population and by the percentage of nitrogen in the samples. The statistical analysis also demonstrated that Ac is more sensitive to changing environmental conditions than YQ/X, yielding more-accurate information about the soil metabolic processes. [source] | ||||||||||||||||||||||||||||||||||||||||