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Pure Cultures (pure + culture)
Selected AbstractsVIRULENCE RESPONSE OF A SALMONELLA TYPHIMURIUM HILA:LACZY FUSION STRAIN TO SPENT MEDIA FROM PURE CULTURES OF SELECTED BACTERIA AND POULTRY CECAL MIXED CULTUREJOURNAL OF FOOD SAFETY, Issue 3 2002J.D. NUTT ABSTRACT Virulence gene expression in Salmonella is triggered by a variety of environmental factors including changes in the gastrointestinal environment of birds during different dietary regimes. The objective of this study was to determine if growth of specific microorganisms alters the environmental conditions sufficiently to signal Salmonella Typhimurium virulence response. Spent media was obtained from a Salmonella Typhimurium hilA:lacZY fusion strain, a poultry Salmonella Typhimurium strain, Eschcrichia coli K12, and Lactobacillus caseii Spent media samples were collected after 2, 4, 8 and 24 h of growth in brain heart infusion broth (BHI) and M9 media, ,-galactosidase assays were performed on the samples to determine virulence expression. Virulence response to Salmonella, spent media was 2-fold greater than Lactobacillus spent media at 4, 8 and 24 h growth (P < 0.05). Virulence expression almost doubled when exposed to Salmonella Typhimurium (NONA) spent media compared to mixed culture spent media at 4 h, and Salmonella Typhimurium (NONA) was significantly higher than mixed culture spent media at 24 h (P < 0.05). Based on these results, it appears that growth of similar bacterial species may alter the composition of rich media sufficiently to influence virulence. [source] Effect of High-Pressure Processing on Vibrio parahaemolyticus Strains in Pure Culture and Pacific OystersJOURNAL OF FOOD SCIENCE, Issue 4 2002H. Calik ABSTRACT Different strains of Vibrio parahaemolyticus (Vp) in broth cultures and Vp-inoculated live Pacific oysters (Crassostrea gigas) were subjected to high-pressure processing (HPP) at 241, 276, 310, and 345 MPa. Results showed Vp numbers were reduced by HPP in both pure culture and whole oysters. Vp inactivation was dependent on time and pressure. Optimum conditions for reducing Vp in pure culture and oysters to nondetectable levels were achieved at 345 MPa for 30 and 90 s, respectively. Resistance variations were detected between Vp in pure culture and in oysters. HPP proved to be an efficient means of reducing Vp in oysters. [source] Inactivation of Vibrio parahaemolyticus in pure culture, whole live and half shell oysters (Crassostrea virginica) by X-rayLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2009B.S.M. Mahmoud Abstract Aims:, To study the inactivation effect of different doses of X-ray on Vibrio parahaemolyticus in pure culture, inoculated whole live and half shell oysters and to evaluate the efficacy of X-ray doses on reduction of inherent microflora on oysters. Methods and Results:, X-ray was produced using RS 2400 generator system (Rad Source Technologies Inc.). Pure culture of V. parahaemolyticus, inoculated half and whole shell oysters with V. parahaemolyticus were treated with 0·0, 0·1, 0·5, 0·75, 1·0, 1·5, 2·0, 3·0 and 5·0 kGy X-ray. Surviving bacteria in the pure culture and inoculated oysters, before and after treatment, were enumerated using overlay plating (in TSA then TCBS) and most probable number (MPN) methods. A greater than 6·0 log reduction of V. parahaemolyticus was observed with 0·75, 2·0 and 5·0 kGy X-ray for pure culture, half shell and whole shell oysters, respectively. Treatment with 0·75, 2·0 and 5·0 kGy X-ray reduced the MPN to <3 for pure culture, half and whole shell oysters, respectively. Treatment with 1·0 kGy X-ray significantly (P < 0·05) reduced the inherent micro-organisms on whole shell oysters from 4·7 ± 0·1 to less than the detectable limit (<1·0 log CFU g,1). Conclusions:, X-ray (1,5 kGy) significantly (P < 0·05) reduced V. parahaemolyticus and inherent microflora on oysters to less than detectable limit (<1·0 log CFU g,1). Significance and Impact of the Study:, Treatment with X-ray could control pathogenic bacteria and extend the shelf life of oysters. [source] Heterobasidion on Abies nordmanniana in north-eastern TurkeyFOREST PATHOLOGY, Issue 6 2007-Lehtijärvi, H. T. Do Summary Occurrence of Heterobasidion annosum s.l. was investigated in 15 coniferous stands in the Giresun and Pontic Mountains in north-eastern Turkey. Basidiocarps of the fungus were found in 11 stands. Fifty-two basidiocarp specimens of Heterobasidion were collected from stumps of Abies nordmanniana ssp. nordmanniana and two from stumps of Picea orientalis. Pure cultures were isolated from the basidiocarps and identified with the aid of mating tests. Forty-five (90%) of the specimens collected from A. nordmanniana were identified as H. abietinum and five (10%) as H. annosum s.s. The former species was also found twice on P. orientalis. This is the first report of H. annosum s.s. for Turkey and the first report of H. abietinum on P. orientalis. Heterobasidion abietinum seems to be mostly a saprotroph on A. nordmanniana. [source] Cytotoxic Bacillus spp. belonging to the B. cereus and B. subtilis groups in Norwegian surface watersJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004Ø. Østensvik Abstract Aims:, To investigate the presence and numbers of Bacillus spp. spores in surface waters and examine isolates belonging to the B. cereus and B. subtilis groups for cytotoxicity, and to discuss the presence of cytotoxic Bacillus spp. in surface water as hazard identification in a risk assessment approach in the food industry. Methods and Results:, Samples from eight different rivers with variable degree of faecal pollution, and two drinking water sources, were heat shocked and examined for the presence of Bacillus spp. spores using membrane filtration followed by cultivation on bovine blood agar plates. Bacillus spp. was present in all samples. The numbers varied from 15 to 1400 CFU 100 ml,1. Pure cultures of 86 Bacillus spp. isolates representing all sampling sites were characterized using colony morphology, atmospheric requirements, spore and sporangium morphology, and API 50 CHB and API 20E. Bacillus spp. representing the B. cereus and B. subtilis groups were isolated from all samples. Twenty-one isolates belonging to the B. cereus and B. subtilis groups, representing eight samples, were screened for cytotoxicity. Nine strains of B. cereus and five strains belonging to the B. subtilis group were cytotoxic. Conclusions:, The presence of cytotoxic Bacillus spp. in surface water represents a possible source for food contamination. Filtration and chlorination of surface water, the most common drinking water treatment in Norway, do not remove Bacillus spores efficiently. This was confirmed by isolation of spores from tap water samples. Significance and Impact of the Study:, Contamination of food with water containing low numbers of Bacillus spores implies a risk for bacterial growth in foods. Consequently, high numbers of Bacillus spp. may occur after growth in some products. High numbers of cytotoxic Bacillus spp. in foods may represent a risk for food poisoning. [source] Comparison of three enrichment media for the isolation of Campylobacter spp. from foodsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2000C.L. Baylis Aim: This study compared the performance of three Campylobacter enrichment broths: Bolton broth (BB), Campylobacter Enrichment broth (CEB) and Preston broth (PB). Methods and Results: Pure cultures of target and competitor organisms, and naturally-contaminated food samples, were used to establish the performance of these media. In pure culture the PB supported the growth of the greatest number of strains of Campylobacter spp. but failed to inhibit some competitor organisms. The CEB showed the opposite result, inhibiting all 15 competitor organisms used but failing to support the growth of five Campylobacter strains. By comparison, BB showed the best compromise between inhibition of competitors and growth of Campylobacter. Conclusions: Plates inoculated with BB and CEB food enrichments resulted in more Campylobacter growth than those inoculated with PB, which supported significantly less typical growth (P , 0·001). The most common competitor organism isolated from PB was Escherichia coli, and Pseudomonas spp. were frequently isolated from BB and CEB. Both BB and CEB were better than PB for the isolation of Campylobacter from naturally-contaminated foods, although BB yielded more confirmed Campylobacter growth than CEB. Significance and Impact of the Study: This study highlighted differences in performance of media used to isolate Campylobacter spp. from foods. [source] Dominant sugar utilizers in sediment of Lake Constance depend on syntrophic cooperation with methanogenic partner organismsENVIRONMENTAL MICROBIOLOGY, Issue 6 2008Nicolai Müller Summary Six strains of novel bacteria were isolated from profundal sediment of Lake Constance, a deep freshwater lake in Germany, by direct dilution of the sediment in mineral agar medium containing a background lawn of the hydrogen-scavenging Methanospirillum hungatei as a syntrophic partner. The numbers of colony-forming units obtained after incubation for more than 2 months were in the same range as those of total bacterial counts determined by DAPI staining (up to 108 cells per millilitre) suggesting that these organisms were dominant members of the community. Identical dilution series in the absence of methanogenic partners yielded numbers that were lower by two to three orders of magnitude. The dominant bacteria were isolated in defined co-culture with M. hungatei, and were further characterized. Growth was slow, with doubling times of 22,28 h at 28°C. Cells were small, 0.5 × 5 ,m in size, Gram-positive, and formed terminal oval spores. At 20°C, glucose was fermented by the co-culture strain BoGlc83 nearly stoichiometrically to 2 mol of acetate and 1 mol of methane plus CO2. At higher temperatures, also lactate and traces of succinate were formed. Anaerobic growth depended strictly on the presence of a hydrogen-scavenging partner organism and was inhibited by bromoethane sulfonate, which together indicate the need for a syntrophic partnership for this process. Strain BoGlc83 grew also aerobically in the absence of a partner organism. All enzymes involved in ATP formation via glycolysis and acetyl CoA were found, most of them at activities equivalent to the physiological substrate turnover rate. This new type of sugar-fermenting bacterium appears be the predominant sugar utilizer in this environment. The results show that syntrophic relationships can play an important role also for the utilization of substrates which otherwise can be degraded in pure culture. [source] Validation of a real-time PCR method for the detection of Phytophthora ramorum1EPPO BULLETIN, Issue 2 2006A. Chandelier To validate a real-time PCR method for the detection of Phytophthora ramorum, an intra-laboratory procedure was developed. The specificity of the TaqMan probe/primer sets was determined by carrying out real-time PCR on total DNA extracted from pure culture of several Phytophthora species. The limit of detection and the potential effects of plant substrates were evaluated by conducting the test on total DNA from healthy plant materials (Rhododendron spp., Viburnum spp. and Pieris spp.) spiked with known amounts of P. ramorum genomic DNA. The PCR efficiency was estimated through the linear regression of the dilution curve. Precision of the TaqMan assay was assessed on material from a single artificially infected plant (Rhododendron spp.). Two kinds of tissues were tested: a severely infected twig and an apparently healthy leaf. Intra-assay repeatability was evaluated on 10 replicates of the same DNA sample analysed in a single assay. Inter-assay reproducibility was evaluated on the same DNA sample amplified over five separate assays while the intersample reproducibility was evaluated on separate DNA extractions of four samples from both plant tissues amplified in a single assay. [source] Efficiency of acid phosphatases secreted from the ectomycorrhizal fungus Hebeloma cylindrosporum to hydrolyse organic phosphorus in podzolsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2010Julien Louche Abstract Ectomycorrhizal fungi may improve the phosphate nutrition of their host plants by secreting, into the soil solution, acid phosphatases (AcPases) able to release orthophosphate (Pi) from soil organic phosphorus (Po). Using cation-exchange chromatography, we separated four fractions with AcPase activity secreted by the ectomycorrhizal fungus Hebeloma cylindrosporum grown in a pure culture under P-starved conditions. Each AcPase active fraction displayed strong ability in vitro to hydrolyse a wide range of phosphate monoesters, but none of them efficiently hydrolysed phytate. Their efficiency to release Pi from soil NaHCO3 -extractable Po was studied in a sandy podzol used intact or autoclaved. Soils were collected in a 15-year-old Pinus pinaster stand, receiving regular fertilization or not. Autoclaving increased the NaHCO3 -extractable Po concentrations by 55% in unfertilized and by 32,43% in fertilized soils. The efficiency of each AcPase fraction was affected significantly by the soil fertilization regime and the soil treatment (intact vs. autoclaved). The proportion of labile Po enzyme ranged from 0% to 11% and 14% to 48% after 1 h of incubation in bicarbonate solutions extracted from intact and autoclaved soils, respectively. This work suggests that AcPases secreted from H. cylindrosporum could be efficient in recycling Po pools from soil microorganisms that may be delivered by soil autoclaving. [source] Lactate has the potential to promote hydrogen sulphide formation in the human colonFEMS MICROBIOLOGY LETTERS, Issue 2 2009Perrine Marquet Abstract High concentrations of sulphide are toxic for the gut epithelium and may contribute to bowel disease. Lactate is a favoured cosubstrate for the sulphate-reducing colonic bacterium Desulfovibrio piger, as shown here by the stimulation of sulphide formation by D. piger DSM749 by lactate in the presence of sulphate. Sulphide formation by D. piger was also stimulated in cocultures with the lactate-producing bacterium Bifidobacterium adolescentis L2-32. Other lactate-utilizing bacteria such as the butyrate-producing species Eubacterium hallii and Anaerostipes caccae are, however, expected to be in competition with the sulphate-reducing bacteria (SRB) for the lactate formed in the human colon. Strains of E. hallii and A. caccae produced 65% and 96% less butyrate from lactate, respectively, in a coculture with D. piger DSM749 than in a pure culture. In triculture experiments involving B. adolescentis L2-32, up to 50% inhibition of butyrate formation by E. hallii and A. caccae was observed in the presence of D. piger DSM749. On the other hand, sulphide formation by D. piger was unaffected by E. hallii or A. caccae in these cocultures and tricultures. These experiments strongly suggest that lactate can stimulate sulphide formation by SRB present in the colon, with possible consequences for conditions such as colitis. [source] High expression of a sucrose non-fermenting (SNF1)-related protein kinase from Colletotrichum gloeosporoides f. sp. malvae is associated with penetration of Malva pusilla,FEMS MICROBIOLOGY LETTERS, Issue 2 2002Paul H Goodwin Abstract A sucrose non-fermenting (SNF1)-related protein kinase homologue, cgsnf, from Colletotrichum gloeosporoides f. sp. malvae, a hemibiotrophic fungal pathogen of round-leaved mallow (Malva pusilla) was examined. During infection, cgsnf showed a large peak in expression relative to a constitutively expressed fungal actin gene when appressoria had formed during the penetration phase and then showed much lower expression levels during subsequent necrotrophic growth in the host. In pure culture with glucose or glycerol as sole carbon sources, expression levels were similar to that during necrotrophic growth. Expression was consistently higher in glycerol than in glucose cultures, which may reflect a lower cellular energy status in the fungus. These results are consistent with cgsnf having a role in transmitting nutritional signals, which may be involved with host penetration. [source] Targeted genomic detection of biosynthetic pathways: anaerobic production of hopanoid biomarkers by a common sedimentary microbeGEOBIOLOGY, Issue 1 2005W. W. FISCHER ABSTRACT The lipid biomarker principle requires that preservable molecules (molecular fossils) carry specific taxonomic, metabolic, or environmental information. Historically, an empirical approach was used to link specific taxa with the compounds they produce. The lipids extracted from numerous, but randomly cultured species provided the basis for the interpretation of biomarkers in both modern environments and in the geological record. Now, with the rapid sequencing of hundreds of microbial genomes, a more focused genomic approach can be taken to test phylogenetic patterns and hypotheses about the origins of biomarkers. Candidate organisms can be selected for study on the basis of genes that encode proteins fundamental to the synthesis of biomarker compounds. Hopanoids, a class of pentacyclic triterpenoid lipid biomarkers, provide an illustrative example. For many years, interpretations of biomarker data were made with the assumption that hopanoids are produced only by aerobic organisms. However, the recent discovery of 13C-depleted hopanoids in environments undergoing anaerobic methane oxidation and in enrichment cultures of anammox planctomycetes indicates that some hopanoids are produced anaerobically. To further examine the potential distribution of hopanoid biosynthesis by anaerobes, we searched publicly available genomic databases for the presence of squalene-hopene cyclase genes in known obligate or facultative anaerobes. Here we present evidence that Geobacter sulfurreducens, Geobacter metallireducens, and Magnetospirillum magnetotacticum, all bacteria common in anoxic environments, have the appropriate genes for hopanoid biosynthesis. We further show that these data accurately predict that G. sulfurreducens does produce a variety of complex hopanoids under strictly anaerobic conditions in pure culture. [source] An in-vitro investigation of the antibacterial effect of nisin in root canals and canal wall radicular dentineINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2004S. R. Turner Abstract Aim, To determine whether nisin, a bacteriocin, would be effective at killing Enterococcus faecalis and Streptococcus gordonii cells in solution and within the root canal system. Methodology, Bacterial isolates of E. faecalis and S. gordonii were grown from glycerol stocks in closed tubes containing BHY broth at 37 °C. The minimum bactericidal concentration (MBC) of nisin for both bacterial species was determined by a microdilution method. Extracted human teeth were decoronated to produce roots of equal length with a single canal and divided into six groups of 10 roots. The canals were prepared to a master apical size 30 file using 0.04 taper Ni-Ti rotary instruments. Bacterial samples of each species were inoculated into three groups of prepared roots and incubated in closed tubes at 37 °C for 21 days. The root canals in each group were then medicated with water (control), calcium hydroxide powder mixed with sterile water [Ca(OH)2], or nisin and incubated for a further 7 days. Rotary Ni-Ti files were used to take radicular dentine samples from the walls of each canal which were then incubated in BHY broth for 24 h. Optical density (OD600) readings were taken as a measure of bacterial growth. Results, The MBC of nisin for E. faecalis and S. gordonii was 70 and 20 mg mL,1 respectively. Calcium hydroxide and nisin medication eradicated infection within the root canal while cells remained viable in the control group. Mean optical density (OD600) readings from canal wall dentine shavings infected with E. faecalis were 1.32 ± 0.98, 0.73 ± 0.27 and 0.69 ± 0.38 for the control, Ca(OH)2 and nisin samples respectively. Corresponding mean readings for S. gordonii were 1.19 ± 0.18, 0.73 ± 0.15 and 0.60 ± 0.29. The Ca(OH)2 and nisin group readings were significantly (P < 0.01) lower than the control for each species as tested by Student's t -test and Mann,Whitney U statistical analysis. Values for Ca(OH)2 and nisin were not significantly (P > 0.01) different. Conclusion, Nisin was effective at eradicating E. faecalis and S. gordonii cells in pure culture and was comparable with Ca(OH)2 in the elimination of these species from within the root canal system. [source] Isolation of yeasts and enteric bacteria in root-filled teeth with chronic apical periodontitisINTERNATIONAL ENDODONTIC JOURNAL, Issue 6 2001V. Peciuliene Abstract Aims The aim of this study was to determine the occurrence and role of yeasts, enteric gram-negative rods and Enterococcus species in root-filled teeth with chronic apical periodontitis, and the antimicrobial effect of iodine potassium iodide (IKI) irrigation. Methodology Forty symptom-free root-filled teeth with chronic apical periodontitis were included in the study. The patients were divided into two groups. In group A the canals were filled with calcium hydroxide for 10,14 days after cleaning and shaping; in group B the canals were irrigated with IKI for 5 min after cleaning and shaping followed by a permanent root filling. Microbiological samples were taken from the canals before and after the chemomechanical preparation and after iodine irrigation (group B). Results Microbes were isolated from 33 of 40 teeth in the initial sampling. Yeasts were isolated from six teeth, three of them together with E. faecalis. Enteric rods (Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis) were present in three teeth and E. faecalis was isolated from 21 of the 33 culture positive teeth, 11 in pure culture. Growth was detected in 10 teeth of the second samples. Six of the 10 cases were E. faecalis, with five being a pure culture. All third samples (after IKI) except one were negative. The number of microbial cells per sample did not correlate with lesion size. Two flare-ups were recorded, both in teeth with a mixed infection. Conclusion The high prevalence of enteric bacteria and yeasts in root-filled teeth with chronic apical periodontitis was established. IKI improved the antimicrobial effect of the treatment. [source] Effects of thymol and diphenyliodonium chloride against Campylobacter spp. during pure and mixed culture in vitroJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2009R.C. Anderson Abstract Aims:, To determine if the purported deaminase inhibitors diphenyliodonium chloride (DIC) and thymol reduce the growth and survivability of Campylobacter. Methods and Results:, Growth rates of Campylobacter jejuni and Camp. coli were reduced compared to unsupplemented controls during culture in Muellar,Hinton broth supplemented with 0·25 ,mol DIC or thymol ml,1 but not with 0·01 ,mol monensin ml,1 or 1% ethanol. Recovery of Camp. jejuni and Camp. coli was reduced >5 log10 CFU from controls after 24 h pure culture in Bolton broth supplemented with 0·25 or 1·0 ,mol DIC ml,1 or with 1·0 ,mol thymol ml,1. Similarly, each test Campylobacter strain was reduced >3 log10 CFU from controls after 24 h mixed culture with porcine faecal microbes in Bolton broth supplemented with 0·25 or 1·0 ,mol DIC ml,1 or with 1·0 ,mol thymol ml,1. Treatments with 0·25 ,mol thymol ml,1, 0·01 ,mol monensin ml,1 or 1% ethanol were less effective. Ammonia production during culture or incubation of cell lysates was reduced by 0·25 or 1·0 ,mol DIC ml,1 but only intermittently reduced, if at all, by the other treatments. Conclusions:, Diphenyliodonium chloride and thymol reduced growth, survivability and ammonia production of Camp. jejuni and Camp. coli. Significance and Impact of the Study:, Results suggest a potential physiological characteristic that may be exploited to develop interventions. [source] Growth of pure cultures of Verocytotoxin-producing Escherichia coli in a range of enrichment mediaJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008C.L. Baylis Abstract Aims:, This study compared the growth of different strains of Verocytotoxin-producing Escherichia coli (VTEC) in a range of selective enrichment media. Methods and Results:, Turbidometric and impedance methods were used to determine the growth of VTEC in pure culture in different enrichment media. Ten strains failed to grow in buffered peptone water + vancomycin, cefsulodin, cefixime at 42°C and some failed to grow, or grew poorly in E. coli (EC) medium supplemented with 20 mg l,1 novobiocin and modified EC supplemented with 20 mg l,1 novobiocin at 37°C and 42°C. Individual VTEC strains were sensitive to the selective agents in some media. Statistical analysis of the conductance detection times of 10 strains showed no overall effect of temperature alone (P = 0·66) but there were significant (P < 0·001) effects as a result of the combination of medium and temperature and these two factors were influenced by strain. Conclusions:, Growth of VTEC during enrichment is dependent on different factors alone or in combination. These include medium type, presence of certain selective agents or antibiotics, incubation temperature and the initial population of VTEC. Sensitivity to these conditions can be strain related. Significance and Impact of the Study:, This study highlighted differences in the ability of some enrichment media to support the growth of VTEC, making them unsuitable for the isolation of VTEC, especially low numbers of non-O157 strains. [source] Physiological characterization of Mycobacterium sp. strain 1B isolated from a bacterial culture able to degrade high-molecular-weight polycyclic aromatic hydrocarbonsJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2004C.E. Dandie Abstract Aim:, The aim of this study was to further characterize a bacterial culture (VUN 10,010) capable of benzo[a]pyrene cometabolism. Methods and Results:, The bacterial culture, previously characterized as a pure culture of Stenotrophomonas maltophilia (VUN 10,010), was found to also contain another bacterial species (Mycobacterium sp. strain 1B), capable of degrading a similar range of PAH substrates. Analysis of its 16S rRNA gene sequence and growth characteristics revealed the strain to be a fast-growing Mycobacterium sp., closely related to other previously isolated PAH and xenobiotic-degrading mycobacterial strains. Comparison of the PAH-degrading characteristics of Mycobacterium sp. strain 1B with those of S. maltophilia indicated some similarities (ability to degrade phenanthrene and pyrene), but some differences were also noted (S. maltophilia able to degrade fluorene, but not fluoranthene, whereas Mycobacterium sp. strain 1B can degrade fluoranthene, but not fluorene). Unlike the S. maltophilia culture, there was no evidence of benzo[a]pyrene degradation by Mycobacterium sp. strain 1B, even in the presence of other PAHs (ie pyrene) as co-metabolic substrates. Growth of Mycobacterium sp. strain 1B on other organic carbon sources was also limited compared with the S. maltophilia culture. Conclusions:, This study isolated a Mycobacterium strain from a bacterial culture capable of benzo[a]pyrene cometabolism. The Mycobacterium strain displays different PAH-degrading characteristics to those described previously for the PAH-degrading bacterial culture. It is unclear what role the two bacterial strains play in benzo[a]pyrene cometabolism, as the Mycobacterium strain does not appear to have endogenous benzo[a]pyrene degrading ability. Significance and Impact of the Study:, This study describes the isolation and characterization of a novel PAH-degrading Mycobacterium strain from a PAH-degrading culture. Further studies utilizing this strain alone, and in combination with other members of the consortium, will provide insight into the diverse roles different bacteria may play in PAH degradation in mixed cultures and in the environment. [source] Comparison of three enrichment media for the isolation of Campylobacter spp. from foodsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2000C.L. Baylis Aim: This study compared the performance of three Campylobacter enrichment broths: Bolton broth (BB), Campylobacter Enrichment broth (CEB) and Preston broth (PB). Methods and Results: Pure cultures of target and competitor organisms, and naturally-contaminated food samples, were used to establish the performance of these media. In pure culture the PB supported the growth of the greatest number of strains of Campylobacter spp. but failed to inhibit some competitor organisms. The CEB showed the opposite result, inhibiting all 15 competitor organisms used but failing to support the growth of five Campylobacter strains. By comparison, BB showed the best compromise between inhibition of competitors and growth of Campylobacter. Conclusions: Plates inoculated with BB and CEB food enrichments resulted in more Campylobacter growth than those inoculated with PB, which supported significantly less typical growth (P , 0·001). The most common competitor organism isolated from PB was Escherichia coli, and Pseudomonas spp. were frequently isolated from BB and CEB. Both BB and CEB were better than PB for the isolation of Campylobacter from naturally-contaminated foods, although BB yielded more confirmed Campylobacter growth than CEB. Significance and Impact of the Study: This study highlighted differences in performance of media used to isolate Campylobacter spp. from foods. [source] Detection of toxigenic Vibrio cholerae from environmental water samples by an enrichment broth cultivation,pit-stop semi-nested PCR procedureJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2000J. Theron A pit-stop semi-nested PCR assay for the detection of toxigenic Vibrio cholerae in environmental water samples was developed and its performance evaluated. The PCR technique amplifies sequences within the cholera toxin operon specific for toxigenic V. cholerae. The PCR procedure coupled with an enrichment culture detected as few as four V. cholerae organisms in pure culture. Treated sewage, surface, ground and drinking water samples were seeded with V. cholerae and following enrichment, a detection limit of as few as 1 V. cholerae cfu ml,1 was obtained with amplification reactions from crude bacterial lysates. The proposed method, which includes a combination of enrichment, rapid sample preparation and a pit-stop semi-nested PCR, could be applicable in the rapid detection of toxigenic V. cholerae in environmental water samples. [source] Aerobic degradation by white-rot fungi of trichloroethylene (TCE) and mixtures of TCE and perchloroethylene (PCE)JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2008Ernest Marco-Urrea Abstract BACKGROUND: Trichloroethylene (TCE) and perchloroethylene (PCE) are considered among the most important groundwater pollutants around the world. These compounds are usually found together in polluted environments but little is known about the ability of microorganisms to simultaneously degrade TCE and PCE. RESULTS: Data showed that several species of white-rot fungi, including Trametes versicolor, Ganoderma lucidum, and Irpex lacteus, degrade substantial levels of TCE in pure culture. T. versicolor was chosen for further study since it degraded higher levels of TCE than the other organisms. Initial glucose concentration and reoxygenation of samples increased the amount of TCE dechlorination, but no significant difference in percentage TCE degradation was observed. T. versicolor was able to degrade 34.1 and 47.7% of PCE and TCE added as mixtures (containing 5 and 10 mg L,1, respectively). CONCLUSIONS: The degradation ability of TCE was extended to other species of white-rot fungi. Percentage degradation as well as chloride release from mixtures of TCE and PCE showed that T. versicolor degrades mixtures of TCE and PCE almost as well as its ability to degrade individually added TCE or PCE. The results suggest the potential promise of T. versicolor for bioremediation of TCE and PCE in the environment. Copyright © 2008 Society of Chemical Industry [source] Effect of High-Pressure Processing on Vibrio parahaemolyticus Strains in Pure Culture and Pacific OystersJOURNAL OF FOOD SCIENCE, Issue 4 2002H. Calik ABSTRACT Different strains of Vibrio parahaemolyticus (Vp) in broth cultures and Vp-inoculated live Pacific oysters (Crassostrea gigas) were subjected to high-pressure processing (HPP) at 241, 276, 310, and 345 MPa. Results showed Vp numbers were reduced by HPP in both pure culture and whole oysters. Vp inactivation was dependent on time and pressure. Optimum conditions for reducing Vp in pure culture and oysters to nondetectable levels were achieved at 345 MPa for 30 and 90 s, respectively. Resistance variations were detected between Vp in pure culture and in oysters. HPP proved to be an efficient means of reducing Vp in oysters. [source] Inactivation of Vibrio parahaemolyticus in pure culture, whole live and half shell oysters (Crassostrea virginica) by X-rayLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2009B.S.M. Mahmoud Abstract Aims:, To study the inactivation effect of different doses of X-ray on Vibrio parahaemolyticus in pure culture, inoculated whole live and half shell oysters and to evaluate the efficacy of X-ray doses on reduction of inherent microflora on oysters. Methods and Results:, X-ray was produced using RS 2400 generator system (Rad Source Technologies Inc.). Pure culture of V. parahaemolyticus, inoculated half and whole shell oysters with V. parahaemolyticus were treated with 0·0, 0·1, 0·5, 0·75, 1·0, 1·5, 2·0, 3·0 and 5·0 kGy X-ray. Surviving bacteria in the pure culture and inoculated oysters, before and after treatment, were enumerated using overlay plating (in TSA then TCBS) and most probable number (MPN) methods. A greater than 6·0 log reduction of V. parahaemolyticus was observed with 0·75, 2·0 and 5·0 kGy X-ray for pure culture, half shell and whole shell oysters, respectively. Treatment with 0·75, 2·0 and 5·0 kGy X-ray reduced the MPN to <3 for pure culture, half and whole shell oysters, respectively. Treatment with 1·0 kGy X-ray significantly (P < 0·05) reduced the inherent micro-organisms on whole shell oysters from 4·7 ± 0·1 to less than the detectable limit (<1·0 log CFU g,1). Conclusions:, X-ray (1,5 kGy) significantly (P < 0·05) reduced V. parahaemolyticus and inherent microflora on oysters to less than detectable limit (<1·0 log CFU g,1). Significance and Impact of the Study:, Treatment with X-ray could control pathogenic bacteria and extend the shelf life of oysters. [source] Selective growth of Staphylococcus aureus from flushed dairy manure wastewater using acriflavine-supplemented mannitol salt agarLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2006J.A. Davis Abstract Aims:, To investigate the use of mannitol salt agar (MSA) supplemented with acriflavine for selective growth and quantification of Staphylococcus aureus from flushed dairy manure wastewater (FDMW). Methods and Results:, Minimal inhibitory concentrations of acriflavine in MSA were determined by comparing the growth of S. aureus subsp. aureus (ATCC 33591) and Staphylococcus epidermidis (ATCC 155) in pure culture. Acriflavine concentrations of 1·3, 1·4 and 1·5 mg l,1 reduced CFU of S. epidermidis by 43%, 55% and 87%, respectively, while CFU of S. aureus subsp. aureus were only reduced by 15%, 20% and 26% at the respective concentrations of acriflavine. MSA supplemented with 1·5 mg l,1 acriflavine was tested for selective growth of indigenous S. aureus from three grab samples of FDMW. Acriflavine concentrations of 1·5 mg l,1 reduced background flora without significantly reducing (P < 0·05) indigenous S. aureus counts. Conclusions:, Acriflavine-supplemented MSA provides an effective media for selective growth and quantification of indigenous S. aureus from FDMW in the presence of high levels of background microflora. Significance and Impact of the Study:,S. aureus is implicated for mastitis infections in dairy cows. Therefore, a reliable means for monitoring and detecting the organism in FDMW provides a tool for measuring the effectiveness of treatment for reducing S. aureus levels and implementing flushwater recycling without affecting herd health. [source] Small genetic differences between ericoid mycorrhizal fungi affect nitrogen uptake by VacciniumNEW PHYTOLOGIST, Issue 3 2009Gwen-Aëlle Grelet Summary ,,Ericoid mycorrhizal fungi have been shown to differ in their pattern of nitrogen (N) use in pure culture. Here, we investigate whether this functional variation is maintained in symbiosis using three ascomycetes from a clade not previously shown to include ericoid mycorrhizal taxa. ,,Vaccinium macrocarpon and Vaccinium vitis-idaea were inoculated with three fungal strains known to form coils in Vaccinium roots, which differed in their patterns of N use in liquid culture. 15N was used to trace the uptake of -N, -N and glutamine-N into shoots. ,,15N transfer differed among the three fungal strains, including two that had identical internal transcribed spacer (ITS) sequences, and was quantitatively related to fungal growth in liquid culture at low carbon availability. ,,These results demonstrate that functional differences among closely related ericoid mycorrhizal fungi are maintained in symbiosis with their hosts, and suggest that N transfer to plant shoots in ericoid mycorrhizas is under fungal control. [source] Thermodynamic Analysis of Energy Transfer in Acidogenic CulturesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2008J.-R. Bastidas-Oyanedel Abstract A global thermodynamic analysis, normally used for pure cultures, has been performed for steady-state data sets from acidogenic mixed cultures. This analysis is a combination of two different thermodynamic approaches, based on tabulated standard Gibbs energy of formation, global stoichiometry and medium compositions. It takes into account the energy transfer efficiency, ,, together with the Gibbs free energy dissipation, ,Go, analysis of the different data. The objective is to describe these systems thermodynamically without any heat measurement. The results show that , is influenced by environmental conditions, where increasing hydraulic retention time increases its value all cases. The pH effect on , is related to metabolic shifts and osmoregulation. Within the environmental conditions analyzed, , ranges from 0.23 for a hydraulic retention time of 20,h and pH,4, to 0.42 for a hydraulic retention time of 8,h and a pH ranging from 7,8.5. The estimated values of ,Go are comparable to standard Gibbs energy of dissipation reported in the literature. For the data sets analyzed, ,Go ranges from ,1210,kJ/molx, corresponding to a stirring velocity of 300,rpm, pH,6 and a hydraulic retention time of 6,h, to ,20744,kJ/molx for pH,4 and a hydraulic retention time of 20,h. For average conclusions, the combined approach based on standard Gibbs energy of formation and global stoichiometry, used in this thermodynamic analysis, allows for the estimation of Gibbs energy dissipation values from the extracellular medium compositions in acidogenic mixed cultures. Such estimated values are comparable to the standard Gibbs energy dissipation values reported in the literature. It is demonstrated that , is affected by the environmental conditions, i.e., stirring velocity, hydraulic retention time and pH. However, a relationship that relates this parameter to environmental conditions was not found and will be the focus of further research. [source] In situ substrate conversion and assimilation by nitrifying bacteria in a model biofilmENVIRONMENTAL MICROBIOLOGY, Issue 9 2005Armin Gieseke Summary Local nitrification and carbon assimilation activities were studied in situ in a model biofilm to investigate carbon yields and contribution of distinct populations to these activities. Immobilized microcolonies (related to Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrospira sp., and to other Bacteria) were incubated with [14C]-bicarbonate under different experimental conditions. Nitrifying activity was measured concomitantly with microsensors (oxygen, ammonium, nitrite, nitrate). Biofilm thin sections were subjected to fluorescence in situ hybridization (FISH), microautoradiography (MAR), and local quantification of [14C]-bicarbonate uptake (beta microimaging). Nitrifying activity and tracer assimilation were restricted to a surface layer of different thickness in the various experiments (substrate or oxygen limitation). Excess oxygen uptake under all conditions revealed heterotrophic activity fuelled by decay or excretion products during active nitrification. Depth limits and intensity of tracer incorporation profiles were in agreement with ammonia-oxidation activity (measured with microsensors), and distribution of incorporated tracer (detected with MAR). Microautoradiography revealed a sharp individual response of distinct populations in terms of in-/activity depending on the (local) environmental conditions within the biofilm. Net in situ carbon yields on N, expressed as e, equivalent ratios, varied between 0.005 and 0.018, and, thus, were in the lower range of data reported for pure cultures of nitrifiers. [source] Fluorescence in situ hybridization of 16S rRNA gene clones (Clone-FISH) for probe validation and screening of clone librariesENVIRONMENTAL MICROBIOLOGY, Issue 11 2002Andreas Schramm Summary A method is presented for fluorescence in situ hybridization (FISH) of 16S rRNA gene clones targeting in vivo transcribed plasmid inserts (Clone-FISH). Several different cloning approaches and treatments to generate target-rRNA in the clones were compared. Highest signal intensities of Clone-FISH were obtained using plasmids with a T7 RNA polymerase promoter and host cells with an IPTG-inducible T7 RNA polymerase. Combined IPTG-induction and chloramphenicol treatment of those clones resulted in FISH signals up to 2.8-fold higher than signals of FISH with probe EUB338 to cells of Escherichia coli. Probe dissociation curves for three oligonucleotide probes were compared for reference cells containing native (FISH) or cloned (Clone-FISH) target sequences. Melting behaviour and calculated Td values were virtually identical for clones and cells, providing a format to use 16S rRNA gene clones instead of pure cultures for probe validation and optimization of hybridization conditions. The optimized Clone-FISH protocol was also used to screen an environmental clone library for insert sequences of interest. In this application format, 13 out of 82 clones examined were identified to contain sulphate-reducing bacterial rRNA genes. In summary, Clone-FISH is a simple and fast technique, compatible with a wide variety of cloning vectors and hosts, that should have general utility for probe validation and screening of clone libraries. [source] Design and application of oligonucleotide probes for fluorescent in situ identification of the filamentous bacterial morphotype Nostocoida limicola in activated sludgeENVIRONMENTAL MICROBIOLOGY, Issue 9 2001Jian Rong Liu 16S rRNA targeted probes, designed using sequence data from pure cultures of the three morphotypes of the filamentous bulking bacteria Nostocoida limicola I, II and III and their successful application to the in situ identification of these bacteria in activated sludge biomass samples are described here. Two probes were required to detect all the sequenced N. limicola II isolates. Results from fluorescent in situ hybridization suggest that the morphotypes N. limicola I and II contain at least two phylogenetically unrelated bacteria. The N. limicola II filaments that did not respond to the probes designed in this study fluoresced instead with the probes previously designed for the ,-Proteobacteria. The data also suggest that both N. limicola I and III can exist in activated sludge as single, paired or clumped cells and thus in a form not recognizable microscopically as this morphotype. Some N. limicola II filaments which responded to the probes designed here were much thinner than the filaments conventionally ,identified' as this morphotype and better fitted the descriptions often used in the literature for N. limicola I. [source] Growth of Frankia strains in leaf litter-amended soil and the rhizosphere of a nonactinorhizal plantFEMS MICROBIOLOGY ECOLOGY, Issue 1 2009Babur S. Mirza Abstract The ability of Frankia strains to grow in the rhizosphere of a nonactinorhizal plant, Betula pendula, in surrounding bulk soil and in soil amended with leaf litter was analyzed 6 weeks after inoculation of pure cultures by in situ hybridization. Growth responses were related to taxonomic position as determined by comparative sequence analysis of nifH gene fragments and of an actinomycetes-specific insertion in Domain III of the 23S rRNA gene. Phylogenetic analyses confirmed the basic classification of Frankia strains by host infection groups, and allowed a further differentiation of Frankia clusters within the Alnus host infection group. Except for Casuarina -infective Frankia strains, all other strains of the Alnus and the Elaeagnus host infection groups displayed growth in the rhizosphere of B. pendula, and none of them grew in the surrounding bulk soil that was characterized by a very low organic matter content. Only a small number of strains that all belonged to a distinct phylogenetic cluster within the Alnus host infection group grew in soil amended with ground leaf litter from B. pendula. These results demonstrate that saprotrophic growth of frankiae is a common trait for most members of the genus, and the supporting factors for growth (i.e. carbon utilization capabilities) varied with the host infection group and the phylogenetic affiliation of the strains. [source] Bovicin HC5 inhibits wasteful amino acid degradation by mixed ruminal bacteria in vitroFEMS MICROBIOLOGY LETTERS, Issue 1 2009Janaína R. Lima Abstract Streptococcus bovis HC5 produces a broad spectrum lantibiotic (bovicin HC5) that inhibits pure cultures of hyper ammonia-producing bacteria (HAB). Experiments were preformed to see if: (1) S. bovis HC5 cells could inhibit the deamination of amino acids by mixed ruminal bacteria taken directly from a cow, (2) semi-purified bovicin was as effective as S. bovis HC5 cells, and 3) semi-purified and the feed additive monensin were affecting the same types of ammonia-producing ruminal bacteria. Because purified and semi-purified bovicin HC5 was as effective as S. bovis HC5 cells, it appeared that bovicin HC5 was penetrating the cell membranes of HAB before it could be degraded by peptidases and proteinases. Mixed ruminal bacteria that were successively transferred and enriched nine times with trypticase did not become significantly more resistant to either bovicin HC5 (50 AU mL,1) or monensin (5 ,M), and amplified rDNA restriction analysis indicated that bovicin HC5 and monensin appeared to be selecting against the same types of bacteria. [source] | |||||||||||||||||||||||||||||||||||||