bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of proteolytic rumen bacteria isolated from New Zealand cattle
Authors: Attwood G.T. , Reilly K.
Published: March 2008

The protease activities of 212 strains of rumen bacteria isolated from New Zealand cattle grazing pasture were measured. Thirty‐seven per cent of strains had activity greater than or equal to the proteolytic rumen bacterium Prevotella ruminicola and 43 of these isolates were identified by morphology, carbon source utilization, Gram stain, biochemical tests and fermentation end‐product analysis. Hierarchical Cluster Analysis showed that the strains formed four clusters: cluster A contained 26 strains and clustered with a reference strain of Streptococcus bovis; cluster C contained three strains and clustered with a reference strain of Butyrivibrio fibrisolvens, while clusters B (10 strains) and D (three strains) did not cluster with any of the remaining rumen bacterial type strains. Further tests identified strains of cluster B as Eubacterium budayi, while cluster D strains most closely resembled B. fibrisolvens and were described as B. fibrisolvens‐like. An unclustered strain, C21a, was identified as P. ruminicola. The significance of these proteolytic bacterial populations is discussed in relation to protein breakdown in New Zealand ruminants.
Genome analysis of five soil bacterial isolates named formerly Enterobacter agglomerans
Authors: Evguenieva‐Hackenberg E. , Selenska‐Pobell S.
Published: March 2008

The genomes of five nitrogen‐fixing strains isolated from the vicinity of Bayreuth and named formerly Enterobacter agglomerans were studied and compared with the genomes of several Rahnella aquatilis strains as well as with one Pantoea agglomerans and one Ent. agglomerans reference strains, obtained from different world collections; they all were previously assumed to be related to this group of natural isolates.

By using the infrequently cutting restriction endonuclease XbaI, highly chracteristic fingerprints were obtained for each of the studied strains except two Ent. agglomerans isolates which had identical fingerprints. By hybridization of the resulting individual PFGE‐fingerprints with a rDNA probe, containing the rrnB ribosomal RNA operon of Escherichia coli, the relationship between the analysed strains was studied. It was shown that the natural isolates are very closely related to the type strain of R. aquatilis—ATCC 33071. The genome sizes of all studied strains were estimated to be between 4.4 and 5.8 Mb on the basis of the lengths of their XbaI fragments. By a modification of the PFGE technique it was shown that the analysed strains harbour one to three large and extra large plasmids with sizes in the range 90 to 608 kb.
The differentiation of Staphylococcus aureus from other Micrococcaceae isolated from bovine mammary glands
Authors: Lam T.J.G.M. , Pengov A. , Schukken Y.H. , Smit J.A.H. , Brand A.
Published: March 2008

Haemolysin production, the slide coagulase test and the tube coagulase test were assessed for their capability to differentiate Staphylococcus aureus among other Micrococcaceae in 199 isolates from udders of cows in herds with a low bulk milk somatic cell count. The API‐Staph test was used as a reference.

Haemolysin production was less effective in identifying Staph. aureus among Micrococcaceae than a combination of other tests. Differences were found in the predictive values of results from diagnostic protocols in which the slide coagulase test was performed on all Micrococcaceae, or on β‐haemolysin‐negative Micrococcaceae only. Diagnostic protocols in which haemolysin production was combined with the results of the other tests resulted in excellent diagnostic performance and a reduction in diagnostic procedures. Recommendations for routine Staph. aureus identification in bovine mastitis bacteriology are given.
The role of Bacillus species in the fermentation of cassava
Authors: Amoa‐Awua W.K.A. , Jakobsen M.
Published: March 2008

Cassava dough inoculum is added to grated cassava in order to achieve a modification of texture during fermentation into the fermented cassava meal, agbelima. The microflora of two different types of inocula and subsequently inoculated cassava mash at 0, 24 and 48 h of fermentation were examined in order to determine the mechanism responsible for the breakdown of cassava tissue. Bacillus spp. occurred in high numbers, 107–108 cfu g‐1, in both types of inocula and persisted throughout the cassava dough fermentation. Bacillus spp. found were B. subtilis, B. mycoides, B. pumilus, B. cereus, B. amyloliquefaciens and B. licheniformis, with B. subtilis accounting for more than half of Bacillus isolates. All Bacillus isolates produced a wide spectrum of enzymes and showed similar enzymatic activities but only B. pumilus, B. licheniformis and B. amyloliquefaciens produced linamarase. Some isolates produced the tissue degrading enzymes polygalacturonase and pectin esterase and nearly all isolates hydrolysed starch. All isolates showed cellulase activity and were able to disintegrate cassava tissue. When cassava pieces were incubated in amylase, cellulase, pectin esterase and polygalacturonase solutions, only pieces in cellulase solution were dissolved revealing that the breakdown of cassava dough texture during fermentation with the inocula examined is brought about by Bacillus spp. through cellulase activity.
Multiplex polymerase chain reaction to detect toxigenic Vibrio cholerae and to biotype Vibrio cholerae O1
Authors: Shangkuan Y.H. , Show Y.S. , Wang T.M.
Published: March 2008

A multiplex polymerase chain reaction (PCR) was developed to identify cholera toxin‐producing Vibrio cholerae and to biotype V. cholerae O1. Enterotoxin‐producing V. cholerae strains were identified with a primer pair that amplified a fragment of the ctxA2‐B gene. Vibrio cholerae O1 strains were simultaneously differentiated into biotypes with three primers specified for the hlyA gene in the same reaction. The hlyA amplicon in the multiplex PCR serves as an internal control when testing toxin‐producing strains, as hlyA gene sequences exist in all tested V. cholerae strains. Enrichment of V. cholerae present on oysters for 6 h in alkaline peptone water before detection by a nested PCR with internal primers for ctxA2‐B gene yielded a detection limit lower than 3 colony‐forming units (cfu) per gram of food.
The effect of osmotic shock and subsequent adaptation on the thermotolerance and cell morphology of Listeria monocytogenes
Authors: Jørgensen F. , Stephens P.J. , Knøchel S.
Published: March 2008

The relationship between the time of exposure to different levels of NaCl and the corresponding changes in thermotolerance and cell morphology of Listeria monocytogenes was investigated. The kinetics of the increase in thermotolerance, after an osmotic upshift, showed a very rapid initial response (<2 min) followed by a more gradual increase whereby cells, after 4 h exposure at 30°C, became nearly as heat resistant as those grown for 48 h under the same conditions. Cells grown in media with 0.09 mol l−1 NaCl subjected to a short osmotic up‐shock in media containing 0.5, 1.0 or 1.5 mol l−1 NaCl showed a 1.3, 2.5 and 8‐fold increase in thermotolerance, respectively. Osmotic adaptation, signified by growth at the higher NaCl concentration, however, resulted in a 2‐ to 3‐fold additional increase in thermotolerance. An osmotic down‐shock caused a very rapid loss of thermotolerance (<5 min). Osmotic shock and adaptation experiments were also performed in minced beef where similar changes in thermotolerance were observed. Cell morphology was markedly affected by the osmolarity of the growth medium. Cells grown in media containing 1.5 mol l−1 NaCl became up to 50 times longer than cells grown in media with 0.09 mol l−1 NaCl, but no direct link to thermotolerance could be made.
The effect of cryptolepine on the morphology and survival of Escherichia coli, Candida albicans and Saccharomyces cerevisiae
Authors: Sawer I.K. , Berry M.I. , Brown M.W. , Ford J.L.
Published: March 2008

The antimicrobial activity of the indoloquinoline alkaloid, cryptolepine, isolated from Cryptolepis sanguinolenta (Fam. Periplocaceae) was determined against selected micro‐organisms. The minimum inhibitory concentration (MIC) ranges obtained, expressed as μg ml−1, were: 5–10 for Saccharomyces cerevisiae NCPF 3139; 10–20 for S. cerevisiae NCPF 3178; 20–40 for Escherichia coli NCTC 10418; 40–80 for E. coli NCTC 11560, Candida albicans ATCC 10231 and C. tropicalis NCPF; and 80–160 for C. albicans NCPF 3242 and NCPF 3262.

Biocidal effects were noted at concentrations 2–4 times those of the MIC of the alkaloid following challenge with 106 cfu ml−1 of micro‐organisms. Time‐kill studies showed a reduction in viable count from 106 to < 10 cfu ml−1 in 4 h in C. albicans ATCC 10231 exposed to 320 μg ml−1 of the agent; 3 log cycle reductions were recorded for the 6 h counts of E. coli NCTC 10418 and S. cerevisiae NCPF 3139 exposed to 40μg ml−1 and 160 μg ml−1 of the alkaloid respectively.

These results were consistent with findings using scanning electron microscopy. Exposure of cells to biocidal concentrations of cryptolepine produced filamentation prior to lysis in E. coli NCTC 10418 and extreme disturbance of surface structure, including partial and total collapse, followed by lysis in C. albicans ATCC 10231 and S. cerevisiae NCPF 3139.
Inhibition of Listeria in dry fermented sausages by the bacteriocinogenic Lactobacillus sake CTC494
Authors: Hugas M. , Garriga M. , Aymerich M.T. , Monfort J.M.
Published: March 2008

Lactobacillus sake CTC494 isolated from a naturally fermented sausage, produced an antibacterial agent active against selected strains of Listeria monocytogenes and L. innocua. The agent was bacteriolytic against L. monocytogenes and sensitive to proteolytic enzymes; it was identified as a bacteriocin and was designated as sakacin K. The ability of Lact. sake CTC494 to inhibit the growth of listeria, compared to a bacteriocinogenic negative control strain, was examined in a model sausage system and in dry fermented sausages. In dry fermented sausages Lact. sake CTC494 was able not only to suppress the growth of listeria but to diminish their number by 1.25 log compared to the non‐bacteriocinogenic control strain. Thus, Lact. sake CTC494 has proved to be a good starter culture providing good organoleptical and sensorial qualities to the product and can be employed as a bioprotective starter culture in fermented meat products.
Expression of a cloned cellulase/xylanase gene from Prevotella ruminicola in Bacteroides vulgatus, Bacteroides uniformis and Prevotella ruminicola
Authors: Daniel A.S. , Martin J. , Vanat I. , Whitehead T.R. , Flint H.J.
Published: March 2008

A new shuttle vector, pRH3 (8.7 kb), was constructed for use in Prevotella/Bacteroides host strains. This vector combines the pRR12 replicon from P. ruminicola, pBluescript sequences and a tetQ marker gene for selection in Prevotella/Bacteroides hosts. Following insertion of a fragment carrying an endoglucanase/xylanase gene from P. ruminicola 23 into the multiple cloning site, the resulting construct, pRH3X, was introduced into B. vulgatus 1447, B, uniformis 1100 and P. ruminicola 2202. This resulted in increases of between 4 and 50‐fold in CM‐cellulase and xylanase activities in cells grown with glucose. In contrast activities were barely detectable for the same construct in E. coli DH5α. Most of the total xylanase activity produced was found within the cell in P. ruminicola 2202 and B. vulgatus 1447 transformed with pRH3X, and in P. ruminicola 23. An osmotic shock experiment indicated that a significant proportion of the xylanase activity in B. vulgatus 1447 cells carrying pRH3X was periplasmic.
Development of resistance to biocides during sporulation of Bacillus subtilis
Authors: Knott A. G. , Russell A. D. , Dancer B. N.
Published: March 2008

From synchronized sporulation and spore mutant studies, the order of development of resistance to biocides during sporulation of Bacillus subtilis strain 168 was toluene, formaldehyde, sodium lauryl sulphate, phenol, phenylmercuric nitrate, m‐cresol, chlorocresol, chlorhexidine gluconate, cetylpyridinium chloride, moist heat, sodium dichlorisocyanurate, sodium hypochlorite, lysozyme and glutaraldehyde. These resistances could be assigned to different stages in spore development.
Survival of the phytopathogen Erwinia carotovora subsp. carotovora in sterile and non‐sterile soil, sand and their admixture
Authors: Armon R. , Dosoretz C. , Yoirish A. , Shelef G. , Neeman I.
Published: March 2008

Survival of phytopathogens in irrigation water and irrigated soil is of major concern to the agricultural community. In the present study, an Erwinia carotovora subsp. carotovora strain was tested for survival capability in three non‐sterile and heat‐sterilized soil matrices (soil, sand and soil + sand) over 35 d. In all non‐sterile soil matrices, Erw. carotovora subsp. carotovora numbers declined below the detection limit over 35 d, the main variance being the decline rate related to nutrients available in the different matrices (soil, soil + sand and sand respectively). In heat‐sterilized soil and soil + sand matrices Erw. carotovora subsp. carotovora revealed a regrowth, while in sterile sand matrix its decline was lower over the same time period. In previous published reports, when soil was sterilized by irradiation, such a regrowth was not observed. Application of an initial single load of sodium nitrate solution (70 mg l−1) was found to extend bacteria survival rate in non‐sterile and sterile soil columns. In sterile soil columns supplemented with sodium nitrate, Erw. carotovora subsp. carotovora did survive well for up to 60 d, with a major regrowth over the first 12 d and decline up to day 60, reaching initial loading numbers. The information on the potential survival of Erw. carotovora subsp. carotovora in soil for up to 35 d and regrowth in sterile soil should be of concern, especially when irrigation is performed with poor quality water.
Stimulation or inhibition of growth of the unicellular alga Pavlova lutheri by bacteria isolated from larval turbot culture systems
Authors: Munro P. D. , McLean H. A. , Barbour A. , Birkbeck T. H.
Published: March 2008

During growth of larval turbot in aquaculture the first food supplied is usually the rotifer, Brachionus plicatilis and algae are commonly included in the system as food for the rotifers, thereby maintaining their nutrient quality. As bacteria are known to influence markedly the survival of larval turbot, the effect of bacteria, isolated from larval turbot, on growth of Pavlova lutheri was measured over a 3‐d period. Of 41 bacteria tested, 23 inhibited growth to various degrees, eight had no effect and 10 were weak growth stimulants. Four bacteria, identified as a Flavobacterium, Vibrio fluvialis, Vibrio natrigens and a Vibrio sp., were strongly inhibitory and the Flavobacterium inhibited growth of Pavlova lutheri from an inoculum of 103 colony‐forming units per ml. Inhibition was due to a heat‐labile factor released by the Flavobacterium into the culture medium. The Flavobacterium also produced bacteriocin(s) which inhibited the growth of a range of vibrios. Bacteria antagonistic towards algae would be undesirable in larval rearing and if bacteria are to be selected which are beneficial (probiotics) in larval rearing systems their possible interaction with algae must be considered.
Polymerase chain reaction for verification of fluorescent colonies of Erwinia chrysanthemi and Pseudomonas putida WCS358 in immunofluorescence colony staining
Authors: van der Wolf J.M. , van Beckhoven J.R.C.M. , de Vries Ph.M. , Raaijmakers J.M. , Bakker P.A.H.M. , Bertheau Y. , van Vuurde J.W.L.
Published: March 2008

The potential of polymerase chain reaction (PCR) for verifying the identity of colonies stained by the immunofluorescence colony‐staining (IFC) procedure was investigated. Using primers directed against conserved sequences of the pectate lyase‐genes coding for isozymes PLa, PLd and PLe of Erwinia chrysanthemi, the authors confirmed the identity of 96% of 20 fluorescent target colonies, punched from IFC‐stained samples with pure cultures. In pour plates with mixtures of Erw. chrysanthemi and non‐target colonies from potato peel extracts, the identity of 90% of 113 target colonies was confirmed.

Using primers directed against sequences of the ferric‐pseudobactin receptor gene pupA of Pseudomonas putida WCS358, the identity of 96% of 22 target colonies was confirmed in IFC‐stained samples with pure cultures. In pour plates with mixtures of Ps. putida WCS358 and non‐target bacteria from compost extracts, the identity of 59% of 108 fluorescent colonies was confirmed by PCR. It was shown that components from non‐target bacteria lowered the threshold level of PCR for Ps. putida WCS358
Enhancement of inulinase production by Aspergillus niger van Teighem
Authors: Viswanathan P. , Kulkarni P.R.
Published: March 2008

P. VISWANATHAN AND P.R. KULKARNI. 1995. Aspergillus niger van Teighem, a soil isolate, was mutagenized by u.v. light. A mutant strain with 3 times increased productivity was generated on exposure of the parent strain to u.v. for 15 min. This mutant on further exposure to u.v. yielded second generation mutants with only marginal increase in inulinase productivity with respect to the parent mutant, but the best yield of 377 U ml−1 was considered promising for industrial use.
Salmonella typhimurium DT 193: differentiation of an epidemic phage type by antibiogram, plasmid profile, plasmid fingerprint and salmonella plasmid virulence (spv) gene probe
Authors: Hampton M.D. , Threlfall E.J. , Frost J.A. , Ward L.R. , Rowe B.
Published: March 2008

M.D. HAMPTON, E.J. THRELFALL, J.A. FROST, L.R. WARD AND B. ROWE. 1995. Of over 2000 isolates of Salmonella typhimurium DT 193 from humans examined in the 2 year period 1991–92, 93% were antibiotic‐resistant with the most common R‐types being ASSuT (38%) and T (29%). Fourteen plasmid profiles were identified in DT 193 R‐type ASSuT with the majority of isolates being characterized by a single plasmid of 80 MDa (pDEP 34) which in addition to coding for ASSuT, also hybridized with a spv gene probe prepared from the 50 MDa Salm. dublin serovar‐specific plasmid. On the basis of restriction fragment length polymorphisms, two variant lines of pDEP 34‐like plasmids were identified and a third line which had lost the genes coding for resistance to ampicillin, streptomycin and sulphonamides, was recognized. Although 18 plasmid profile types were identified in DT 193 R‐type T, all isolates carried a high mol. wt plasmid which coded for tetracycline resistance only. Further discrimination was achieved on the basis of hybridization of tetracycline resistance plasmids with the spv gene probe and restriction enzyme fingerprinting. These results demonstrate that Salm. typhimurium DT 193 can be rapidly subdivided by antibiogram and that further subdivision can be achieved on the basis of plasmid profile, plasmid fingerprint and hybridization with a spv gene probe.
Diversity of Aeromonas sp. in Flemish drinking water production plants as determined by gas‐liquid chromatographic analysis of cellular fatty acid methyl esters (FAMEs)
Authors: Huys G. , Kersters Llse , Vancanneyt M. , Coopman Renata , Janssen P. , Kersters K.
Published: March 2008

G. HUYS, I. KERSTERS, M. VANCANNEYT, R. COOPMAN, P. JANSSEN AND K. KERSTERS. 1995. Gas‐liquid chromatography of cellular fatty acid methyl esters (FAMEs) was used to determine the phenotypic and genotypic diversity among 489 presumptive Aeromonas strains isolated from five Flemish drinking water production plants. FAME profiles were compared with the predetermined library profiles of a representative database, AER48C, which contains the mean FAME data of all 14 currently established hybridization groups (HGs) or genospecies within Aeromonas. Using AER48C, more than 93% (457 strains) of all presumptive aeromonads isolated on ampicillin‐dextrin agar were unequivocally identified as belonging to this genus. Moreover, 85.5% and 73.5% of these strains could be assigned to a particular phenospecies or HG, respectively. Raw and treated surface water samples were dominated by members of the Aer. hydrophila complex (38.8%, comprising HGs 1–3), followed by the Aer. caviae complex (22.7%, comprising HGs 4–6) and the Aer. sobria complex (16.7%, comprising HGs 7–9). HGs 3, 5A/B and 8 were the most prominent genospecies in this type of water. On the other hand, it was found that raw and treated phreatic groundwater samples displayed a much more limited species diversity since these were almost entirely dominated (95.8%) by strains belonging to HGs 2 and 3 of the Aer. hydrophila complex. In general, flocculation‐decantation and sand filtration were not shown to influence the overall species distribution in any of the plants examined.
Activity of p‐aminobenzoic acid compared with other organic acids against selected bacteria
Authors: Richards R.M.E. , Xing D.K.L. , King T.P.
Published: March 2008

The antibacterial activity of p‐aminobenzoic acid against Listeria monocytogenes, Salmonella enteritidis and Escherichia coli was compared with the activity of commonly used acidulants: formic, propionic, acetic, lactic and citric acids. Viable count evaluations and MIC determinations indicated that p‐aminobenzoic acid caused greater inhibitory effects than the other organic acids. The activity of p‐aminobenzoic acid on the growth of the test organisms at selected pH values indicated that p‐aminobenzoic acid was more active at low pH than at high pH. Uptake studies showed that the uptake of p‐aminobenzoic acid by E. coli was markedly decreased as the pH values increased. Electron micrographs of E. coli cells grown in the presence of p‐aminobenzoic acid indicate that p‐aminobenzoic acid caused marked damage to the cell envelope. It is suggested that p‐aminobenzoic acid has at least two mechanisms of action: one mechanism in common with other organic acids and the other mechanism by interfering with the synthesis of the peptidoglycan layer by an action on the dihydrofolate reductase enzyme.
Degradation of triglycerides by a pseudomonad isolated from milk: the roles of lipase and esterase studied using recombinant strains over‐producing, or specifically deficient in these enzymes
Authors: McKay D.B. , Dieckelmann Manuela , Beacham I.R.
Published: March 2008

The roles of lipase and esterase in causing hydrolytic spoilage of milk by a highly lipolytic psychrotrophic strain of Pseudomonas fluorescens, LS107d2, has been studied. Strains of LS107d2 have been constructed that over‐produce, or are specifically deficient in, a lipase (encoded by lip A) and an esterase (encoded by est A). Southern blot analysis reveals that LS107d2 contains only one esterase and one lipase (encoded by est A and lip A) and this was confirmed by the phenotypes of mutants on triolein and tributyrin‐containing agar. Analysis of broth cultures showed that the lipase is secreted into the culture medium; in contrast, the esterase is not secreted. Free fatty acid (FFA) levels in whole milk cultures of wild‐type, over‐producing and the mutant strains of LS107d2 have been examined. From these studies it is concluded that esterase is not involved in the accumulation of FFA by hydrolysing short chain fatty acid esters; that the highly lipolytic phenotype of LS107d2 is due solely to a single secreted lipase; and that the main FFA accumulated in milk cultures of LS107d2 are C4, C16, C18 and C18: 1. Evidence is also presented demonstrating that FFA degradation, as well as production, determines the level of FFA in milk contaminated with lipolytic organisms.
Numerical characterization study of Micrococcaceae associated with lamb spoilage
Authors: Prieto M. , García‐Armesto María Rosario , González C. , Otero A. , López María Luisa García
Published: March 2008

A computer‐assisted characterization of 296 Micrococcaceae isolates obtained from aerobically chill‐stored lamb carcasses was carried out using a probability matrix and Bayesian identification theorems, complemented with cluster analysis. Preliminary identification was done with an original probability matrix comprising 37 previously described taxa and 32 tests. Although its statistical quality was adequate, the percentage of identification of field strains to species level was only 70% (96.6% identified with genera). To achieve an improved characterization, cluster analysis was subsequently performed on this group and an additional 26% could be associated with defined species, with five more taxa defined. The combined use of both approaches was judged positive as new identifications and better discrimination could be achieved. The majority of our isolates belonged to the Staphylococcus species group. Many species and groups of staphylococci increased as the spoilage progressed.
Serum survival and plasmid possession by strains of Salmonella enteritidis, Salm. typhimurium and Salm. virchow
Authors: Chart H. , Threlfall E.J. , Powell N.G. , Rowe B.
Published: March 2008

Strains of Salmonella enteritidis, Salm. typhimurium and Salm. virchow, carrying different numbers of plasmids, were examined for the ability to multiply in sera. Viable counts were performed to monitor the kinetics of growth of bacteria when in human, chicken and turkey sera. The presence of plasmids in Salm. enteritidis, Salm. typhimurium and Salm. virchow reduced considerably the ability of strains of these serotypes to multiply in serum. SDS‐PAGE was used to show that growth of Salm. enteritidis in serum did not involve changes in outer membrane proteins or lipopolysaccharide. It was concluded that the carriage of plasmids may be disadvantageous for the survival in serum of certain common salmonella serotypes.
Characterization of the heterologous invertase produced by Schizosaccharomyces pombe from the SUC2 gene of Saccharomyces cerevisiae
Authors: Zárata V. , Belda F.
Published: March 2008

In order to gain information on the ability of Schizosaccharomyces pombe to process heterologous glycoproteins, the heterologous invertase, obtained from the expression in Schiz. pombe of the SUC2 gene of Saccharomyces cerevisiae, was characterized. In Schiz. pombe the heterologous invertase is secreted into the cell wall and seems to be firmly bound to this structure. After the isolation of the heterologous invertase the study of its enzymatic characteristics revealed that it is more similar to the Sacch. cerevisiae external invertase than to the Schiz. pombe invertase. However, it is glycosylated like the Schiz. pombe invertase since it reacts with the lectin from Bandeiraea simplicifolia seeds conjugated to fluorescein isothiocyanate, which indicates the presence of terminal galactose residues in the enzyme. Moreover, the presence of galactose in the heterologous invertase has been confirmed after analysis of the sugars present in its carbohydrate moiety by gas liquid chromatography.
Enhanced degradation of petrol (Slovene diesel) in an aqueous system by immobilized Pseudomonas fluorescens
Authors: Wilson N. G. , Bradley G.
Published: March 2008

The rate of degradation of n‐alkanes C12‐C18, in petrol (Slovene diesel) in an aqueous system, by free and immobilized Pseudomonas fluorescens in shaking flasks was investigated. Cells were immobilized to a biosupport, Biofix, and a biosorbant, Drizit. Analysis of cellular growth of the free and immobilized bacteria over 8 d of incubation with diesel as the sole carbon source, showed a reduction in the lag phase in the immobilized cultures in comparison to the free system. The free system degraded 52·3% of C12 and 11·6% of C13, but C14‐C18 were not degraded. In comparison to the free system and diesel which had not been exposed to experimental conditions (unexposed), the immobilized systems degraded significantly more of C13‐C18. Biofix‐immobilized cells degraded 14·8% of C12 and an average of 53·5% of C13‐C18. Drizit‐immobilized cells degraded 24·5% of C12, 52·4% of C13 and an average of 91·2% of C14‐C18. This study shows the successful use of immobilized bacteria technology to enhance the degradation of diesel in an aqueous system.
Comparison of extracellular proteases produced by Aeromonas salmonicida strains, isolated from various fish species
Authors: Gudmundsdóttir B.K.
Published: March 2008

Extracellular products (ECPs) of five typical and 25 atypicalAeromonas salmonicidaisolates from various fish species and geographical locations were analysed by substrate specificity, inhibition of proteolytic activity and substrate SDS‐PAGE. The type strains ofAer. salmonicidasubsp.salmonicidaandAer. salmonicidasubsp.achromogeneswere included for comparison. The results indicated that the strains formed six protease groups. The proteases produced by the two type strains were of a different nature. All the typical strains belonged to one group and showed proteolytic activities comparable to P1 and P2 proteases. Three atypical (oxidase‐negative) strains secreted a protease comparable to P1. With the exception of these three, all strains produced metallo‐gelatinases. A metallo‐caseinase (AsaP1) was detected in the ECP of subsp.achromogenestype strain and 10 of the atypical strains. A number of proteolytic components with different apparent molecular weights (AMWs) were identified. These include caseinases with AMWs of > 100, 80, 60 and 30 kDa and gelatinolytic components with different AMWs, including some with AMW higher than P1 and lower than P2. The protease production of the isolates was not found to be host specific.
Variations in R‐plasmid DNA concentrations of Escherichia coli during starvation in sewage and brackish waters
Authors: Arturo‐Schaan M. , Tamanai‐Shacoori Z. , Thomas D. , Cormier M.
Published: March 2008

Cell culturability and plasmid stability in Escherichia coli containing plasmids RP1, R388 and pUB824 were studied in raw and treated wastewater, and in brackish water. The E. coli strain survived well in the three samples of water employed. Moreover, the three plasmids were maintained under all conditions studied. Interestingly, plasmid DNA concentration of individual plasmids followed the same evolution as the culturable bacteria in the corresponding selective medium when the bacteria grew in raw or treated wastewater. In contrast, in brackish water, the stress due to the oligotrophic and salinity conditions of the medium produced an initial paradoxical increase in plasmid DNA concentration, followed by a decrease in the number of culturable bacteria in the corresponding selective medium. Maintenance of RP1 (56 kbp) and R388 (33 kbp) was markedly influenced by nutritive conditions, which caused a segregation of the plasmids from cells. The results of the present study suggest that variations in plasmid DNA concentrations in an aquatic environment depend on the quality of the water and also on the molecular weight of the plasmid considered.
Choosing probability distributions for modelling generation time variability
Authors: Ratkowsky D. A. , Ross T. , Macario N. , Dommett T. W. , Kamperman L.
Published: March 2008

This paper explores the variation in generation time of bacterial systems growing at suboptimal temperatures. Generation time generally has a distribution with a long right‐hand tail, suggesting a model with variance proportional to the second or third power of its mean. Suitable non‐normal probability distributions include the ‘gamma’ and ‘inverse Gaussian’, with the modelling being carried out by ‘generalized linear regression’. The procedure is illustrated with replicated data on Pseudomonas fluorescens obtained using a gradient temperature incubator with nutrient broth as the growth medium. The results show that the ‘gamma’ distribution is a suitable stochastic assumption when modelling generation time. This enables one to predict, for example, a mean generation time of 615 min at 2·4°C, and that 0·1% of the observed values will fall below 471 min and one in a million below 405 min. Use of an unreplicated set of data gave less conclusive results but favoured the ‘inverse Gaussian’ distribution as the stochastic model.
Changes in microbial population during fermentation of tropical freshwater fish viscera
Authors: Ahmed J. , Ramesh B.S. , Mahendrakar N.S.
Published: March 2008

Freshwater fish viscera (FV) was homogenized, mixed with 10% (w/w of FV) molasses and 0, 2 or 4% salt and allowed to ferment at ambient temperature (26·2°C) under microaerophilic conditions. The results revealed a reduction in total viable count and the number of spores, coliforms, Escherichia coli, staphylococci and enterococci and an increase in yeasts and moulds and lactic acid bacteria during fermentation. Coliforms and E. coli were found to be absent after 6 d and enterococci on 8th day. The presence of salt resulted in a marginally lower number of all organisms except yeasts, moulds and lactic acid bacteria. Inclusion of either 0·5% propionic acid, 0·3% calcium propionate or 0·1% sorbic acid suppressed growth of yeasts and moulds with propionic acid being the most effective. The study indicated that a microbiologically stable product could be prepared by ensiling fish viscera with 10% molasses and 0·5% propionic acid.
Ribotypes and AP‐PCR fingerprints of thermophilic campylobacters from marine recreational waters
Authors: Hernández J. , Fayos A. , Alonso J.L. , Owen R.J.
Published: March 2008

Thirty‐two strains of thermophilic campylobacters isolated from marine recreational waters and seven reference strains were biotyped and analysed by chromosomal DNA Hae III ribopatterns and AP‐PCR profiles based on a random 10‐mer primer (5′‐CAA TCG CCG T‐3′). The majority of seawater isolates (90%) were Campylobacter coli, and three strains were Camp. jejuni. Southern blot hybridization analysis showed differences between the strains, and in a numerical analysis three main clusters were formed at the 45% similarity level, that corresponded to Camp. jejuni subsp. jejuni, Camp. coli, and a combination of Camp. coli and Camp. jejuni subsp. doylei. AP‐PCR profiles also differentiated between the species but were less discriminatory than ribotyping because six strains (17%) could not be typed by this method. Numerical analysis gave four main clusters at the 45% similarity level, corresponding to Camp. jejuni subsp. jejuni, Camp. coli (two clusters) and Camp. lari. The study shows that strains within each species are diverse genomically. Both molecular methods were highly discriminatory, although some strains with identical ribotypes could be distinguished by AP‐PCR, and they are valuable new alternatives to traditional typing in epidemiological studies of environmental campylobacters.
Differentiation of Listeria isolates by PCR amplicon profiling and sequence analysis of 16S‐23S rRNA internal transcribed spacer loci
Authors: Drebót M. , Neal S. , Schlech W. , Rozee K.
Published: March 2008

The 16S‐23S rRNA internal transcribed spacer region (ITS) in genomic DNA from Listeria species was amplified and sequenced so as to find sequence differences that would allow rapid species and strain differentiation. Agarose gel profiles of amplicons generated with primers designed to amplify ITS loci indicated that Listeria DNA can contain at least two distinct ITS regions. The direct sequencing of the smaller of these ITS amplicons (330 bp) was found useful for the rapid and accurate differentiation of various Listeria species. On the other hand analysis of ITS amplicons generated from a total of 27 L. monocytogenes strains indicated that 4/27 of these strains could be distinguished on the basis of their ITS profile (the presence of a unique 350 bp amplicon). The lack of sequence heterogeneity in the small 333 bp amplicon did not permit rapid strain differentiation.
Adhesion of Clostridium cellulolyticum spores to filter paper
Authors: Gehin A. , Gelhaye E. , Petitdemange H.
Published: March 2008

The adhesion of Clostridium cellulolyticum spores and cells to Whatman No. 1 filter paper was studied. A suspension of vegetative cells in exponential phase from a culture on cellobiose adhered at 60% whereas spores at the same initial concentration were bound to the Whatman filter paper at 90%. Adhesion of vegetative cellulolytic cells occurs on specific cellulosic sites and reveals a sigmoid type II curve. Non‐cellulolytic vegetative cells from Clostridium butyricum do not adhere to the cellulose. Spore adhesion is a non‐specific process since non‐cellulolytic spores from Clostridium butyricum adhered almost in the same range to filter paper than cellulolytic spores.
Fermentation of native and processed starches by the porcine caecal anaerobe Clostridium butyricum (NCIMB 7423)
Authors: Reid C.‐A. , Hillman K. , Henderson C. , Glass H.
Published: March 2008

Starch fermentation by the porcine caecal anaerobe Clostridium butyricum was examined using gas and volatile fatty acid production as determinants of activity. Potato starch and amylopectin were studied in their native form as well as after retrogradation, which should render them resistant to pancreatic α‐amylase digestion. Fermentation of both substrates was enhanced by pancreatin digestion of the native material, possibly due to the removal or disruption of part of the structure of the starch by the pancreatic enzymes. However, pancreatic digestion of retrograded potato starch apparently reduced the amount available for bacterial fermentation, whereas no significant effect was observed with amylopectin. The data suggests that starches which are high in amylopectin would be more likely to influence fermentation in the large intestine in monogastric animals, and that the presence of residual pancreatic enzymes in the lower gut could potentially enhance starch fermentation by this micro‐organism.
Interactions among thermophilic lactobacilli during growth in cheese whey
Authors: Giraffa G. , Mucchetti G. , Neviani E.
Published: March 2008

The starters used in the Parmesan cheese technology are whey‐cultured, mixed strain cultures of thermophilic rod lactic acid bacteria. In mixed strain cultures, interactions among different strains can result in both stimulatory or inhibitory effects on microbial growth rate and metabolic activity. These effects, studied by the use of conductance, were observed for individual strains of thermophilic lactobacilli, which were grown in whey and in the presence of cell‐free supernatant fluids from whey cultures of other strains. The importance of whey as a growth medium on the microbial composition of the whey cultures is discussed.
Effect of pre‐ and post‐heat shock temperature on the persistence of thermotolerance and heat shock‐induced proteins in Listeria monocytogenes
Authors: Jørgensen F. , Panaretou B. , Stephens P.J. , Knøchel S.
Published: March 2008

The effect of incubation temperature, before and after a heat shock, on thermotolerance of Listeria monocytogenes at 58°C was investigated. Exposing cells grown at 10°C and 30°C to a heat shock resulted in similar rises in thermotolerance while the increase was significantly higher when cells were grown at 4°C prior to the heat shock. Cells held at 4°C and 10°C after heat shock maintained heat shock‐induced thermotolerance for longer than cells held at 30°C. The growth temperature prior to inactivation had negligible effect on the persistence of heat shock‐induced thermotolerance. Concurrent with measurements of thermotolerance were measurements of the levels of heat shock‐induced proteins. Major proteins showing increased synthesis upon the heat shock had approximate molecular weights of 84, 74, 63, 25 and 19 kDa. There was little correlation between the loss of thermotolerance after the heat shock and the levels of these proteins. Thermotolerance of heat shocked and non‐heat shocked cells was described by traditional log‐linear kinetics and a model describing a sigmoidal death curve (logistic model). Employing log‐linear kinetics resulted in a poor fit to a major part of the data whereas a good fit was achieved by the use of a logistic model.
Survival potential of Aeromonas hydrophila in freshwaters and nutrient‐poor waters in comparison with other bacteria
Authors: Kersters I. , Huys G. , Van Duffel H. , Vancanneyt M. , Kersters K. , Verstraete W.
Published: March 2008

The survival of a genetically‐marked Aeromonas hydrophila strain was studied in water microcosms using viable counts. Aeromonas hydrophila AWWX1 was shown to survive without decline in viable counts for at least 10 d in three of four filtered‐autoclaved freshwaters (surface water and groundwater) and in all examined filtered‐autoclaved nutrient‐poor waters (bottled spring water, Milli‐Q and tap water). However, in the unfiltered waters, a rapid decrease in viable counts of Aer. hydrophila AWWX1 was observed after 1–5 d. The survival of Aer. hydrophila AWWX1 in nutrient‐poor waters was compared with that of Pseudomonas fluorescens P17 and Spirillum strain NOX. Survival characteristics were organism‐ and water‐dependent. In the filtered‐autoclaved waters, viable counts of Spirillum strain NOX were ca 1 log‐unit higher than for Aer. hydrophila AWWX1 and Ps. fluorescens P17. The tested strains Aer. hydrophila AWWX1 and Ps. fluorescens P17 survived 3 to 20, respectively 2 to 4 times better in the filtered‐autoclaved waters compared to the unfiltered waters. Apparently, any inherent capability of these micro‐organisms to adapt to low‐nutrient environments was undone by the presence of the autochthonous microbiota. The present findings that Aer. hydrophila survives very poorly in several drinking waters is of utmost importance towards public health and arises questions about the mechanisms involved.
Effect of chemical agents on swarming of Bacillus species
Authors: Thampuran N. , Surendran P.K.
Published: March 2008

The effect of 58 chemical compounds belonging to different categories, viz. antibiotics, detergents, surfactants, nutrients and salts of organic and inorganic acids, were tested on swarming of Bacillus species comprising B. coagulans, B. circulans, B. alvei and B. subtilis by spot inoculation method. Carbohydrates, vitamins, amino acids and other nutrient compounds such as peptone, with the exception of vitamin‐free casamino acids induced considerable swarming. An inhibition of swarming was noticed by antiseptics, detergents and surfactants; but the extent of swarming differed among the chemicals tested, their concentration and the bacterial strains. Most of the compounds that inhibited swarming were those which acted on flagellar mechanism and motility. The results support the theory that formation of lateral flagella is a prerequisite for inhibition of swarming.
Studies on the effect of mercury and organomercurial on the growth and nitrogen fixation by mercury‐resistant Azotobacter strains
Authors: Ghosh S. , Sadhukhan P.C. , Ghosh D.K. , Mandal A.K. , Chaudhuri J. , Mandal A.
Published: March 2008

Five nitrogen‐fixing Azotobacter strains isolated from agricultural farms in West Bengal, India, were resistant to mercuric ion and organomercurials. Resistance of Hg‐resistant bacteria to mercury compounds is mediated by the activities of mercuric reductase and organomercurial lyase in the presence of NADPH and GSH as cofactors. These bacteria showed an extended lag phase in the presence of 10–50 μmol 1‐1 HgCl2. Nitrogen‐fixing ability of these isolates was slightly inhibited when the mercuryresistant bacterial cells were preincubated with 10 μmol 1‐1 HgCl2. Acetylene reduction by these bacteria was significantly inhibited (91‐97%) by 50 μmol 1‐1 HgCl2. However, when GSH and NADPH were added to the acetylene reduction assay mixture containing 50 μmol 1‐1 HgCl2, only 42–50% inhibition of nitrogenase activity was observed. NADPH and GSH might have a role in suppressing the inhibition of N2‐fixation in the presence of Hg compounds either by assisting Hg‐detoxifying enzymes to lower Hg concentration in the assay mixture or by formation of adduct comprising Hg and GSH which is unable to inhibit nitrogen fixation.
Characterization of a proteinaceous antimicrobial produced by Lactobacillus helveticus CNRZ450
Authors: Thompson J.K. , Collins M.A. , Mercer W.D.
Published: March 2008

An antimicrobial substance which resembles a bacteriocin was identified in culture supernatant fluids of Lactobacillus helveticus strain CNRZ450. The bacteriocin was active against a narrow range of strains from closely rested species of homofermentative lactobacilli. Its mode of action appeared to be bacteriostatic. Partial purification of the bacteriocin suggested that it was a complex protein with a mol. wt of between 30 and 50 kDa, although there is some evidence that the polypeptide monomer has a mol. wt of around 17 kDa. There was no evidence indicating an extrachromosomal location for its genetic determinant. PCR generated an amplicon from total DNA from strain CNRZ450 using primers based on the helJ gene sequence. A fragment showing homology to this amplicon was located in an Eco RI digest of total DNA from strain CNRZ450. The pattern obtained was different from that obtained with the helveticin J producer strain NCFB481. It is possible, therefore, that the antimicrobial from strain CNRZ450 is related to helveticin J at the DNA sequence level although the physical properties of the two antimicrobials reveal several differences.
Antibacterial activity of anacardic acid and totarol, alone and in combination with methicillin, against methicillinresistant Staphylococcus aureus
Authors: Muroi H. , Kubo I.
Published: March 2008

The inhibitory and bactericidal activities of anacardic acid and totarol, alone and in combination with methicillin, were investigated against methicillin‐resistant Staphylococcus aureus (MRSA). The growth of two MRSA strains was inhibited by 6·25 μg ml‐1 of anacardic acid and 0·78 μg ml‐1 of totarol. The time‐kill curve study showed that these two compounds were bactericidal against MRSA. Anacardic acid killed MRSA cells more rapidly than totarol, and no viable cells were detected after being exposed to 6·25 μg ml‐1 of anacardic acid for 6 h. Anacardic acid showed bactericidal activity against MRSA at any stage of growth, and also even when cell division was inhibited by chloramphenicol. In the combination studies, the minimal inhibitory concentration (MIC) of methicillin was lowered from 800 to 1·56 μg ml‐1 for MRSA ATCC 33591, and from 800 to 6·25 μg ml‐1 for MRSA ATCC 33592, by combining with 1/2 X MIC of anacardic acid. The time‐kill curves demonstrated synergistic bactericidal activities for these combinations.
Differentiation of Aeromonas genomospecies using random amplified polymorphic DNA polymerase chain reaction (RAPD‐PCR)
Authors: Oakey H.J. , Ellis J.T. , Gibson L.F.
Published: March 2008

Random amplified polymorphic DNA polymerase chain reaction (RAPD‐PCR) was used to investigate the differentiation of the genus Aeromonas at the genomospecies level. Of 20 primers evaluated, six produced profiles which contained multiple bands capable of differentiating the genomospecies. These six primers were also used in RAPD‐PCR analyses of clinical and environmental isolates of the different genomospecies. In most cases. each strain gave a unique fingerprint, illustrating genetic heterogeneity at the genomospecies level. However, some homogeneity in fragment sizes was seen among strains within a genomospecies which was not apparent in strains from different genomospecies. This study therefore complements and supports the current classification of Aeromonas into genomospecies. These results also show that RAPD‐PCR has the potential to differentiate between the genomospecies of Aeromonas.