bluuebunny/crossref_metadata_2025 huggingface dataset:
A sandwich enzyme‐linked immunosorbent assay (ELISA) for detection of Pseudomcnas fluorescens and related psychrotrophic bacteria in refrigerated milk
Authors: González I. , Martín R. , García T. , Morales P. , Sanz B. , Hernández P.E.
Published: March 2008

I. GONZÁLEZ, R. MARTÍN, T. GARCÍA, P. MORALES, B. SANZ AND P.E. HERNÁNDEZ. 1993. A sandwich ELISA (enz***me‐linked immunosorbent assay) was developed for detection of Pseudomonas fluorescens and related psychrotrophic bacteria in refrigerated milk. Polyclonal antibodies were raised in rabbits against protein F from the cell envelope of Pseudomonas fluorescens AH‐70. The anti‐protein F antibodies (anti‐PF) bound to the wells of a microtitre plate were used to capture this protein from the micro‐organisms on milk samples. Further immunorecognition of the captured antigen was attained with the same anti‐PF antibodies conjugated to biotin. ExtrAvidin‐peroxidase was used to detect the biotinylated antibodies bound to their specific antigens. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying milk samples containing Ps. fluorescens strains of different origin as well as related psychrotrophic micro‐organisms.
Enumeration of Escherichia coli in cooked and raw meats by ion mobility spectrometry
Authors: Ogden I.D. , Strachan N.J.C.
Published: March 2008

I.D. OGDEN AND N.J.C. STRACHAN. 1993. A novel method for enumeratingEscherichia coliin foods is described. It is based on the production ofo‐nitrophenol (ONP) fromo‐nitrophenyl‐β‐D‐glucuronide as detected by an ion mobility spectrometer. The time taken for the detection of ONP in a food sample was inversely proportional to the logarithm of the initialE. colipopulation.Escherichia colicould be detected at a level of 10 g‐1within 9 h.
Uptake of metals by bacterial polysaccharides
Authors: Geddie Joanne L. , Sutherland I.W.
Published: March 2008

J.L. GEDDIE AND I.W. SUTHERLAND. 1993. The binding of cations by a range of bacterial polysaccharides was examined. Comparison of native and deacetylated polymers indicated the influence of polysaccharide acetylation on ion uptake and selectivity. The effects of temperature and pH on ion uptake were also examined. Metal ion uptake was carried out by dialysis and samples were analysed using ion chromatography. The native acetylated polymers showed a selectivity for Ca2+ > Mg2+ > monovalent cations, whereas samples lacking acetyl groups showed a selectivity for monovalent cations > Mg2+ > Ca2+. Increased temperatures reduced the capacity for several of the polymers to bind the cations; The Zoogloea ramigera polymer appeared least affected. The pH value also affected uptake.
Bactericidal activity of disinfectants on listeria
Authors: Van de Weyer A. , Devleeschouwer M.‐J. , Dony J.
Published: March 2008

A. VAN DE WEYER, M.‐J. DEVLEESCHOUWER AND J. DONY. 1993. The bactericidal activity on Listeria spp. of nine disinfectants used in the food industry was studied by previously published methods. The disinfectants were diluted to the test concentation in sterile standard hard water. Various types of chemical agents were evaluated, including phenolic compounds, alcohols, quaternary ammonium compounds, surface‐active agents, aldehydes and disochlorine tablets. The following strains isolated from cheese were studied: Listeria innocua, L. welshimeri, L. monocytogenes 1/2a, 1/2b, 1/2c and 4b. The results show that the listerias are not particularly resistant to disinfectants but the efficacy of some agents is affected by organic matter.
Genetic studies of lactococcal bacteriophages—taxonomic differentiations and DNA analysis: evidence for 3′ cohesive ends
Authors: Ermel Gwennola , Cavalier Annie , Thomas D. , Le Pennec J.P.
Published: March 2008

Twenty‐four bacteriophages of Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris were classified. Two groups of bacteriophages morphologically defined as prolate or isometric types by electron microscopy were examined for their genome sizes, protein patterns and DNA homologies. These criteria showed that prolate phages are quite homogeneous. In contrast, isometric phages exhibit more differences, particularly in particle sizes and protein compositions. Analysis of DNA hybridizations confirmed that prolate phages can be grouped together as can be isometric phages but for one exception, phage I52. These two families were clearly defined. The unique phage which does not fit in either group probably belongs to a third one which is much less represented. No obvious relationships between these criteria and the lytic spectra were detected. Evidence of the presence of cohesive ends in phage genomes is also presented in this study. A more detailed analysis performed on one member of the prolate group revealed 3′ protruding ends made up of around 13 nucleotides on complementary single strands.
A comparison of conventional SEM techniques, low temperature SEM and the electroscan wet scanning electron microscope to study the structure of a biofilm of Streptococcus crista CR3
Authors: Sutton Naomi A. , Hughes N. , Handley Pauline S.
Published: March 2008

Biofilms of Streptococcus crista CR3 were generated on hydroxyapatite (HA) discs for 20 h in a continuous flow system with brain heart infusion broth dripped over the disc at a rate of 6 ml h‐1. This study compares the conventional scanning electron microscope (SEM) preparation techniques, of critical point drying and freeze‐drying, with low temperature SEM (LTSEM) and Electroscan generated images of hydrated biofilms, which preserve the integrity of hydrated polymers.

Critical point drying and freeze‐drying caused almost complete disappearance of the matrix of extracellular polymeric substances (EPS). Critical point drying, however, showed evenly spaced single or paired cocci remaining on the HA disc whereas freeze‐drying caused the biofilm to detach from the HA leaving only patchy clumps of cells visible. By comparison LTSEM preserved the EPS better than critical point drying and freeze‐drying, but holes were seen in the top and side of the biofilm and the EPS did show some shrinkage artefacts. An untreated wet biofilm viewed in the Electroscan showed an intact, hydrated, smooth matrix of EPS with cell shapes only visible indistinctly in a canopy of moist EPS. No holes were visible and no shrinkage artefacts were evident. Therefore, Electroscan imaging of the biofilm was the only method that preserved the integrity of the matrix with no apparent shrinkage artefacts.
Sakacin B, a bacteriocin produced by Lactobacillus sake isolated from Greek dry fermented sausages
Authors: Samelis J. , Roller Sibel , Metaxopoulos J.
Published: March 2008

When Lactobacillus sake 251, a strain isolated from naturally fermented Greek dry sausage was grown in MRS broth it excreted an antimicrobial factor that differed from organic acids and hydrogen peroxide. The substance was proteinaceous, heat stable and inhibitory towards various lactic acid bacteria of meat origin. This suggested that a narrow spectrum bacteriocin, designated sakacin B, was present in the broth. Sakacin B displayed a bactericidal mode of action on sensitive cells without causing cell lysis. It was secreted during late logarithmic phase and was stable within a pH range 2 to 9. In vitro production of sakacin B by the producer strain in a mixed culture caused a strong biocidal effect on growing indicator cells. Sakacin B was partially purified and found not to contain unusual amino acids. That it was a hydrophobic peptide was confirmed by SDS‐PAGE electrophoresis. The molecular weight of sakacin B was estimated to be 6.3 kDa.
Interaction of iodine with Bacillus subtilis spores and spore forms
Authors: Bloomfield Sally F. , Megid R.
Published: March 2008

Buffered solutions of iodine (pH 7.0) were effective against Bacillus subtilis spores, but concentrations and contact times for effective sporicidal action were relatively high. Concentrations of 500 to 1000 ppm available iodine with a contact time of 30–45 min were required to produce a 3–5 log reduction. Treatment of spores with agents which caused progressive extraction of coat protein and cortex hexosamine was associated with increased sensitivity to iodine. Treatment of spores with iodine produced extraction of spore coat protein which was potentiated in the presence of NaOH, but there was no evidence of breakdown of cortex hexosamines or release of dipicolinic acid, either from intact spores or spore protoplasts. Sporicidal concentrations of iodine stimulated the uptake of (32P) phosphate over an initial period of 30–40 min, but phosphate then leaked from the cells; 1000 ppm available iodine produced total loss within 60 min. Results of this investigation are consistent with previous findings which suggest that the resistance of spores to biocides is related to the barrier properties of the spore outer layers and that the sporicidal action of halogen‐releasing agents is related to their ability to cause coat and cortex degradation, leading to rehydration of the spore protoplast and allowing diffusion to their site of action on the underlying protoplast.
Rapid identification using pyrolysis mass spectrometry and artificial neural networks of Propionibacterium acnes isolated from dogs
Authors: Goodacre R. , Neal M.J. , Kell D.B. , Greenham L.W. , Noble W.C. , Harvey R. G.
Published: March 2008

Curie‐point pyrolysis mass spectra were obtained from reference Propionibacterium strains and canine isolates. Artificial neural networks (ANNs) were trained by supervised learning (with the back‐propagation algorithm) to recognize these strains from their pyrolysis mass spectra; all the strains isolated from dogs were identified as human wild type P. acnes. This is an important nosological discovery, and demonstrates that the combination of pyrolysis mass spectrometry and ANNs provides an objective, rapid and accurate identification technique. Bacteria isolated from different biopsy specimens from the same dog were found to be separate strains of P. acnes, demonstrating a within‐animal variation in microflora. The classification of the canine isolates by Kohonen artificial neural networks (KANNs) was compared with the classical multivariate techniques of canonical variates analysis and hierarchical cluster analysis, and found to give similar results. This is the first demonstration, within microbiology, of KANNs as an unsupervised clustering technique which has the potential to group pyrolysis mass spectra both automatically and relatively objectively.
Isolation of Legionella from water samples using various culture methods
Authors: Kusnetsov Jaana M. , Jousimies‐Somer Hannele R. , Nevalainen Aino I. , Martikainen P. J.
Published: March 2008

The efficacy of a non‐selective medium and two selective media were compared for the isolation of legionellas from water samples. The effect of acid wash treatment for decontamination of the water samples on the isolation frequency of legionellas was also studied. The 236 samples were taken from cooling, humidifying and drinking water systems; 21% were legionella‐positive when inoculated directly on modified Wadowsky‐Yee (MWY) medium and 26% were positive when concentrated (x 200) before cultivation on MWY or CCVC media. Inoculation on MWY medium after concentration followed by decontamination by the acid‐wash technique gave the highest isolation frequency (31%). The lowest frequency (8%) was found with the non‐selective BCYEα medium. An isolation frequency of 28% was achieved with the BCYEα medium after concentration and acid‐wash treatment of the samples. Forty per cent of the samples were positive for legionellas when the results from all the culture methods were combined. Not all the legionella‐positive samples were identified by a single culture method. Ninety‐three of the 95 positive samples were detected with the two best combinations of three culture methods. The best culture method for detecting legionellas depended on the source of the water sample. Some water quality characteristics, like temperature and organic matter content, affected the isolation frequency of Legionella spp.
Purification and characterization of a thermostable glucoamylase from a Myrothecium isolate
Authors: Ali S. , Malek S. , Hossain Z.
Published: March 2008

Two glucoamylases, gluc I and gluc II, were purified to homogeneity from the culture filtrate of a Myrothecium strain M1 by chromatography on DEAE‐cellulose and concanavalin A‐sepharose. Molecular masses deduced by SDS‐PAGE were 72000 ± 2500 for gluc I and 96 000 ± 4000 for glue II. The temperature optima of the enzymes were both about 70°C and their pH optima were around 4.0. Both enzymes were glycoprotein and preferentially hydrolysed high molecular mass substrates. Hg2+ was a potent inhibitor of both glucoamylases. Glue II had higher debranching activity than gluc I.
Development of a diagnostic test for Yersinia pestis by the polymerase chain reaction
Authors: Norkina Olga V. , Kulichenko A.N. , Gintsburg A.L. , Tuchkov I.V. , Popov Yu.A. , Aksenov M.U. , Drosdov I.G.
Published: March 2008

A 501 bp caf1 gene fragment and a 443 bp of pla gene fragment carried by 100 kb (pFra) and 10 kb (pPst) species‐specific extrachromosomal replicons, respectively, were used as targets to study the conditions under which DNA amplification by polymerase chain reaction (PCR) may be applied to detect and identify Yersinia pestis DNA in cell lysates of pure cultures and biological samples. The sensitivity limit of PCR with the crude cell lysates of Y. pestis EV was estimated as 10–50 cfu in reaction mixture. When target Y. pestis EV cells were mixed with fresh blood of white mice, which contained 0.4% potassium citrate, the PCR detection level varied from 400 to 100 cfu ml‐1 of blood depending on the method used for preparing the sample. In our tests PCR was effective for the detection of yersinia in the blood of white laboratory mice experimentally infected with virulent Y. pestis KM638 strain. This method can be considered convenient for routine detection and identification of Y. pestis.
Numerical taxonomy and identification of lactic acid bacteria from spoiled, vacuum‐packaged vienna sausages
Authors: Dykes G.A. , Britz T.J. , von Holy A.
Published: March 2008

Sixty‐one lactic acid bacteria from spoiled vacuum‐packaged vienna sausages and 15 reference strains were tested for 72 phenotypic characteristics. An identification key and a computer data base, both specific for lactic acid bacteria from meat sources, were used for identification and the results were compared. There was a high correlation (86.9%) between the two procedures in the identification of strains to genus level. However, only a 54.8% correlation was obtained in identifying strains to the species level. With numerical taxonomy (Ssm matching coefficient with average linkage clustering) 60 strains were recovered in six clusters at the 89% similarity level. While most Leuconostoc strains clustered separately from the Lactobacillus strains, the identity of many leuconostocs was not clarified. The presence of a heterogeneous cluster containing typical and ‘atypical’ strains of the Lactobacillus saké/curvatus group and a separate homogeneous Lact. curvatus cluster was noted. Closer examination of the data suggested that the ‘atypical’ lactobacilli were all strains of Lact. saké.
Interactions between rumen bacterial strains during the degradation and utilization of the monosaccharides of barley straw cell‐walls
Authors: Miron J. , Duncan Sylvia H. , Stewart C.S.
Published: March 2008

Pure cultures and pair‐combinations of strains representative of the rumen cellulolytic species Ruminococcus flavefaciens, Fibrobacter succinogenes and Butyrivibrio fibrisovens were grown on cell‐wall materials from barley straw. Of the pure cultures, R. flavefaciens solubilized straw most rapidly. The presence of B. fibrisolvens, which was unable to degrade straw extensively in pure culture, increased the solubilization of dry matter by R. flavefaciens and the solubilization of cell‐wall carbohydrates by both R. flavefaciens and F. succinogenes. During fermentation, both R. flavefaciens and F. succinogenes released bound glucose and free and bound arabinose and xylose into solution. The accumulation of these sugars, especially arabinose and xylose, was greatly reduced in co‐cultures containing B. fibrisolvens, suggesting that significant interspecies cross feeding of the products of hemicellulose hydrolysis (particularly soluble bound xylose released by F. succinogenes) occurs during straw degradation by mixed cultures containing this species.
Survival of Salmonella senftenberg and Salmonella typhimurium in glassy and rubbery states of gelatin
Authors: Blissett Samantha J. , Bolton Katherine J. , Dodd Christine E.R. , Gould G.W. , Waites W.M.
Published: March 2008

Salmonella senftenberg and Salmonella typhimurium survived the production of gelatin sheets containing nutrient broth although there was some evidence of cell damage. Both strains survived but did not grow in glassy states with an aw of 0.45–0.28 and rubbery states with an aw of 0.93–0.96 for at least 28 d. Survival was less in intermediate states with an aw between 0.55 and 0.74. The results suggest that salmonellas should be excluded from glassy state products in order to prevent salmonellosis.
Characterization of bacteria contaminating tissue cultures of apple rootstock ‘YP’
Authors: Savela Mervi‐Leena , Uosukainen Marjatta
Published: March 2008

Meristem‐tip cultures of apple rootstock ‘YP’ were started at different times of the year over a period of 2 years and the contamination of the cultures was monitored during five subcultures. Bacterial contaminants were isolated to pure cultures, identified by the API test system and appropriate additional tests, and the sensitivity of the most common isolates to different antibiotics was determined. Of the 216 strains isolated from the initiation cultures, 78% were pseudomonads, coryneforms or enterobacteria. Only three bacterial contaminants were found at the multiplication stage. A greater part of the contaminants were likely to originate from the stock plant. Rifampicin (at 50–200 mg 1‐1) and cefotaxime (at 250–1500 mg 1‐1) were found to be bactericidal against many isolates, but differences between species and strains were found.
Heat resistance of different serovars of Listeria monocytogenes
Authors: Sörqvist S.
Published: March 2008

Twelve Listeria monocytogenes strains representing seven serovars were heat‐treated in physiological saline by a glass capillary tube method. Five strains were treated at 58°, 60° and 62°C, three at 60°, 62° and 64°C and four at 60°C. Heat‐treated bacteria were recovered on blood agar in two ways: (1) incubation at 37°C for 7 d; and (2) preincubation at 4°C for 5 d, followed by incubation at 37°C for 7 d. D and z values were determined. Better average recovery and higher D values were obtained when the preincubation procedure was used. The final evaluations of the heat resistance properties of the strains were therefore based on values for preincubated samples. D values recorded at 58°, 60°, 62° and 64°C for preincubated samples were 1.7–3.4, 0.72–3.1, 0.30–1.3 and 0.33–0.68 min, respectively. z values determined were 5.2–6.9°C. D values were compared statistically. Significant differences in heat resistance were noted both between serovars and between strains belonging to the same serovar.
Patterns of bacterial destruction in solutions by microwave irradiation
Authors: Fujikawa H. , Ohta K.
Published: March 2008

The patterns of destruction of several kinds of bacterial cells suspended in solutions by microwave irradiation were studied. The survival curves of Escherichia coli and Staphylococcus aureus were similar and approximated a set of three linear phases. The curves of Pseudomonas fluorescens and Bacillus cereus spores shifted to the shorter and longer irradiation periods, respectively. The rate constant and initial time of destruction for each linear phase of the survival curve were compared among these organisms. When irradiated E. coli cells were incubated in an agar with a high salt level, fewer cells were recovered. The curve of E. coli cells in the logarithmic phase of growth shifted to shorter exposure periods. There were no significant differences in the survival curves of E. coli cells grown at temperatures of 22–36°C, whereas the curve of cells grown at 44°C shifted to longer periods.
Polymerase chain reaction for detection of Clostridium botulinum types A, B and E in food, soil and infant faeces
Authors: Szabo E.A. , Pemberton J.M. , Gibson A.M. , Eyles M.J. , Desmarchelier P.M.
Published: March 2008

The application of the polymerase chain reaction (PCR) for detection of Clostridium botulinum types A, B and E in foods, environmental and clinical samples was evaluated and compared to the mouse bioassay. Samples inoculated with 10, 100 and 1000 spores of Cl. botulinum types A and B included pasteurized milk, UHT milk, infant formula, infant faeces, meat juice, canned tuna, mushrooms, blood sausage and soil. Clostridium botulinum type E spores were inoculated into fish eggs, canned tuna, picked herring, raw fish and soil at similar levels. Spores were added to 2.5 g of each sample with the exception of soil which was inoculated in 10 g samples. The presence of Cl. botulinum in sample enrichments was determined by both PCR and the bioassay. An overall correlation of 95.6% was observed between PCR results and the mouse bioassay. Of the total of 114 samples tested there was disparity between the mouse bioassay and the PCR in three samples of soil inoculated with 100 type A or E spores and 10 type B spores per 10 g, respectively, and two samples of infant faeces inoculated with 10 type A or B spores per 2.5 g. All of these samples gave negative animal results and positive PCR results.
Characteristics of micrococci from the surface of Roquefort cheese
Authors: Vivier D. , Ratomahenina R. , Galzy P.
Published: March 2008

Five different Micrococcus spp. were isolated from the surface of Roquefort cheese: M. roseus, M. sedentarius, M. lylae, M. luteus and M. varians. During culture on synthetic medium these bacteria produced acetic acid as the main volatile fatty acid and propanol as the main alcohol. On a complex medium these isolates synthesized additional volatile fatty acids. Studies were made of the effect of pH, of water activity adjusted with sodium chloride or sorbitol, and of temperature on growth rates. All five isolates were inhibited at a pH lower than 5.5 and grew at temperatures from 4° to 44°C; they were halotolerant and multiplied at NaCl concentrations up to 20%, corresponding to a water activity of 0.884.
Population dynamics of Erwinia carotovora subsp. atroseptica on the surface of intact and wounded seed potatoes during storage
Authors: van Vuurde J.W.L. , de Vries Ph.M.
Published: March 2008

Population dynamics of Erwinia carotovora subsp. atroseptica (Eca) on the tuber surface during storage (2–4°C) and pregermination, were studied by plating extracts of 6 mm2 point samples on crystal violet pectate medium. To investigate the effect of harvest damage on Eca survival, intact, skinned (epidermis removed), and peeled (complete peel removed) tubers from a dry (pF 3.4) and from a wet (pF 2.0) soil were inoculated either immediately after harvesting or after air drying for 4 h. Eca numbers on intact tuber surface decreased rapidly after inoculation, whereas at the skinned and peeled surface numbers were significantly increased 2 d after harvest. Tubers peeled and inoculated with Eca were rotted by 2 d after harvest while tubers peeled and dried before inoculation did not rot; however, populations were significantly increased 2 d after harvest. For all treatments Eca numbers per point sample decreased to below detection limits 180 d after harvest. Examination of 600 mm2 surface samples of the various treatments 222 d after harvest showed that Eca populations were still present. The number of tubers contaminated with colony‐forming units (cfu) of Eca was significantly lower for intact surface inoculated tubers from dry soil than for those of the other treatments. Drying for 4 h before inoculation resulted in a significant reduction of the number of Eca cfu positive tubers compared to all other treatments. The ELISA OD values of the 600 mm2 surface samples at day 222 were almost all positive and showed only a slight difference between the average of the tubers containing culturable Eca cells and those without culturable Eca cells.
Resistance of Pseudomonas aeruginosa to isothiazolone
Authors: Brözel V.S. , Cloete T.E.
Published: March 2008

This investigation was to determine whether Pseudomonas aeruginosa could acquire resistance to the bactericide isothiazolone, and what the nature of such a resistance mechanism would be. The Pseudomonas was cultured in nutrient‐limited broth in the presence of sub‐inhibitory concentrations of isothiazolone (a mixture of 1.15% 5‐chloro‐N‐methylisothiazolone (CMIT) and 0.35%N‐methylisothiazolone (MIT)). Three cultures tested in parallel adapted gradually during exposure for 15 d from an initial minimum inhibitory concentration (MIC) of 300 μl 1‐1 to 607 μl ‐1. The three parallel cultures adapted at similar rates, so the adaptation was not ascribed to mutation but to a specific mechanism. Resistant cells did not produce any extracellular isothiazolone‐quenching compounds nor undergo detectable alterations in their lipopolysaccharide layer. In wild cells, a 35 kDa outer membrane protein (protein T) was detectable, whereas resistant cells lacked this protein. Production of protein T was suppressed within 24 h of exposure to isothiazolone. It was still suppressed after 72 h of growth in isothiazolone‐free medium. It is proposed that Ps. aeruginosa acquires resistance to isothiazolone by a process of adaptation where the outer membrane protein T is suppressed.
Frequency and diversity of antibiotic production by putative Erwinia herbicola strains
Authors: Wodzinski R.S. , Paulin J.‐P.
Published: March 2008

The frequency and diversity of antibiotic production by putative Erwinia herbicola strains were investigated. Of 346 putative Erw. herbicola strains isolated from plants in various regions of France, 42% produced antibiotics on a glycerol‐ammonium medium that were inhibitory to Erw. amylovora, the fire‐blight pathogen. Of the 90 strains studied in detail that produced antibiotics, 84 produced types of antibiotics that were not toxic to Erw. amylovora (strain CFBP3051) in the presence of different amino acids. On the basis of the amino acids that inhibited the toxicity of the antibiotics to CFBP3051, the 90 strains could be divided into 13 different groups. It is suggested that the effectiveness of an antibiotic in inhibiting Erw. amylovora in vivo may depend on the free amino acid composition of the plant.
Characterization of lactic acid bacteria isolated from seafood
Authors: Mauguin Sylvie , Novel G.
Published: March 2008

Lactic acid bacteria were isolated from various samples of seafood: fresh pollock, brine shrimp, gravad fish, vacuum‐packed seafood (surimi, smoked tuna, salted cod), and fish stored under 100% CO2 at 5°C (smoked tuna, fresh and salted cod, salmon). Eighty‐six independent isolates were obtained and were grouped according to cell morphology, presence or absence of diaminopimelic acid in the cell wall, and lactate configuration. Fifty‐four isolates were identified as belonging to the genus Lactococcus and most of them exhibited DNA homologies with L. lactis subsp. lactis. Four strains were identified as Lactobacillus plantarum, eight strains as genus Leuconostoc and 16 belonged to the genus Carnobacterium. One facultative heterofermentative Lactobacillus and three other isolates were not identified. Of the strains 47% showed similar patterns of carbohydrate fermentations especially among strains belonging to the genera Lactococcus and Carnobacterium. Most of the strains (64%) grew at 5°C, in salted media and in fish extract medium without added sugar. Carnobacterium piscicola and Carn. divergens were the only reference strains able to grow in the same conditions as well as psychrotroph strains isolated from seafood. A numerical analysis could not be used because of the divergent properties of isolates of the same genus and strong similarities between different genera.
A study of the microbiological status of Irish farmhouse cheeses with emphasis on selected pathogenic and spoilage micro‐organisms
Authors: Coveney Helen M. , Fitzgerald G.F. , Daly C.
Published: March 2008

H.M. COVENEY, G.F. FITZGERALD AND C. DALY. 1994. Ninety‐six 25 g samples from 25 Irish farmhouse cheeses, two Irish non‐farmhouse cheeses and four foreign cheeses were evaluated for the presence of a variety of micro‐organisms, namely, coliforms, faecal streptococci, Staphylococcus aureus, yeasts, moulds, salmonellas and shigellas. Seventeen cheeses, i.e. the soft and semi‐soft types, were examined for Listeria monocytogenes. Most of the farmhouse cheeses are currently manufactured from raw milk, but some producers now use heat‐treated milk. The incidence of coliforms and faecal coliforms was higher in soft, semi‐soft and semi‐hard cheeses than in hard types. High levels of contamination by faecal streptococci and non‐pathogenic (coagulase‐negative) Staph. aureus prevailed in a high proportion of the cheeses. Pathogenic (coagulase‐positive) staphylococci, however, were also isolated from 50% of the cheeses, some of which were manufactured from pasteurized milk. Yeasts were found mainly in unpasteurized varieties, especially in the category of soft cheeses. Moulds were isolated from five non‐mould‐ripened cheeses, as well as from mould‐ripened varieties. Salmonellas, shigellas and Listeria monocytogenes were not detected after direct enrichment.
Bacteriological evaluation of groups of beef carcasses before the wash at six Alberta abattoirs
Authors: Jericho K.W.F. , Bradley J.A. , Kozub G.C.
Published: March 2008

K.W.F. JERICHO, J.A. BRADLEY AND G.C. KOZUB. 1994. A method has been developed for the bacteriological evaluation of groups of beef carcasses which can be used to measure the degree of control over hygiene during hide removal and carcass dressing in abattoirs. This method, which enumerates aerobic mesophilic bacteria automatically using a hydrophobic grid membrane filter, was applied at six abattoirs. Two hundred excision samples (5 × 5 × 0.5 cm) were taken at 10 sites on the external surface of a group of 20 carcasses (five carcasses were sampled on each of four consecutive daily visits) for group‐carcass evaluation at each abattoir. For each abattoir, the mean log10 Most Probable Number of Growth Units (MPNGU) and between‐carcass variance component were obtained for each site and the average over sites. Using the average within‐abattoir variance of this study and previously published studies involving 76 additional carcasses (Jericho et al. 1993), it was determined that 20 carcasses are more than adequate to estimate the mean log10 MPNGU per cm2 within 0.5 units at a site. The distribution of the log10 MPNGU per cm2 over the 10 sites was compared for the abattoirs, and sites were found to cluster into 2–4 homogenous groups. The means over sites of log10 MPNGU per cm2 for the abattoirs ranged from 1.52 to 2.64 and were unrelated to line speed
Cyclic growth of lactobacilli in beer
Authors: Fernandez Jacqueline L. , Simpson W.J.
Published: March 2008

J.L. FERNANDEZ AND W.J. SIMPSON 1994. Beer‐spoilage lactic acid bacteria displayed unusual growth characteristics in beer. Cycles of growth and death occurred, as assessed by the ability of the organisms to form colonies on a range of solid growth media, or grow in liquid media, including beer and modified de Man, Rogosa and Sharpe medium. During the death phase, the viable cell count fell by more than 99.9%. The cells were dead rather than nonculturable. Staining with acridine orange showed that they remained physically intact during the death phase. It seems that cycles of ‘cryptic growth’ occur in beer. Cells isolated from different stages of the growth cycle produced similar growth curves when re‐inoculated into beer, showing that selection of adapted cells does not occur.
Typing of Clostridium perfringens by in vitro amplification of toxin genes
Authors: Daube G. , China B. , Simon P. , Hvala K. , Mainil J.
Published: March 2008

G. DAUBE, B. CHINA, P. SIMON, K. HVALA AND J. MAINIL. 1994. The strains of Clostridium perfringens are classified according to major toxins produced. Classically, this determination involves the seroneutralization of their lethal effect in mice. However, this method requires specific antisera and a large number of mice. In this work, a new typing method was developed based on the amplification of toxin genes by polymerase chain reaction (PCR). By combination of several pairs of primers, the toxinotype of a Cl. perfringens strain was determined by looking at the pattern of bands on an agarose gel electrophoresis. This mixture contained primers amplifying simultaneously a part of α‐toxin, α‐toxin, β‐toxin and enterotoxin genes. In order to distinguish between toxinotype A and E, the ***l‐toxin gene fragment must be amplified in a separate PCR reaction. Moreover, with the primers combination, in most cases, a PCR product corresponding to the α‐toxin gene was obtained from direct enrichments of animal intestinal contents.
The construction, detection and use of bioluminescent Rhizobium leguminosarum biovar trifolii strains
Authors: Cresswell Ann , Skøt L. , Cookson A.R.
Published: March 2008

A. CRESSWELL, L. SKØT AND A.R. COOKSON. 1994. The gene encoding the firefly luciferase enzyme (luc) was introduced to Rhizobium leguminosarum biovar trifolii strains with a view to using the resulting bioluminescent strains to study the survival of genetically‐engineered rhizobia in soil microcosms. The genetically‐engineered micro‐organisms (GEMs) behaved similarly to their parent strains with respect to growth rate in laboratory media and in their symbiotic performance with their host plants. No gene transfer could be detected in laboratory mating experiments. When inoculated onto a non‐sterile soil the population of the GEM declined sharply from an initial cell density of 2 times 1077 g‐1 soil to approach a stable cell density of approximately 3 times 102 g‐1 after 150 d. Direct photography of bioluminescent rhizobia enabled the detection of colonies as small as 0.1 mm in diameter without the need for transferring colonies onto filter paper. When a Rhizobium strain carrying the luc marker on a plasmid was used as inoculant it was possible to visualize differences in colonization of the rhizosphere of white clover and ryegrass by contact print and colour transparency films. The photographic detection methods described here demonstrate the possibilities of using bioluminescent rhizobia for assessing their survival in soil, and for looking at rhizosphere populations which may be an important site for potential gene transfer.
Oxygen tolerance estimates in Campylobacter species depend on the testing medium
Authors: Hodge J.P. , Krieg N.R.
Published: March 2008

J.P. HODGE AND N.R. KRIEG. 1994. Oxygen tolerance of the microaerophile Campylobacter jejuni subsp. jejuni varied with different brands of complex media which were used for plating the dilute cell suspensions. The tryptone component was one factor. With some tryptones growth occurred at 21% oxygen whereas with others there was no growth at oxygen levels of 15% or higher. A chemically‐defined, agar‐solidified plating medium was used to estimate the oxygen tolerance of Camp. jejuni subsp. jejuni, Camp. coli and Camp. fetus subsp. fetus, and also to assess the effect of added scavengers of reactive oxygen intermediates on the oxygen tolerance. Some scavengers such as allopurinol, azelaic acid, caffeine, cimetidine, TEMPOL and pyruvate enhanced oxygen tolerance markedly whereas others such as carnosine, dimethyl thiourea, spermidine and superoxide dismutase had little effect.
Salvage synthesis of purine nucleotides by Helicobacter pylori
Authors: Mendz G.L. , Jimenez B.M. , Hazell S.L. , Gero A.M. , O'Sullivan W.J.
Published: March 2008

G.L. MENDZ, B.M. JIMENEZ, S.L. HAZELL, A.M. GERO AND W.J. O'SULLIVAN. 1994. The incorporation of purine nucleotide precursors into Helicobacter pylori and the activities of enzymes involved in nucleotide salvage biosynthetic pathways were investigated by radioactive tracer analysis and nuclear magnetic resonance spectroscopy. The organism took up the nucleobases adenine, guanine and hypoxanthine, and the nucleosides adenosine, guanosine and deoxyadenosine. Any incorporation of deoxyguanosine by the cells was below the detection limits of the methods employed. The activities of adenine‐, guanine‐ and hypoxanthine‐phosphoribosyl transferases were established. The bacterium showed high levels of adenosine and guanosine nucleosidase activities and lesser activity for deoxyadenosine; no hydrolysis of deoxyguanosine was detected. Phosphorylase activities were not observed with any of the nucleosides. Phosphotransferase activities with similar rates were demonstrated for adenosine, guanosine and deoxyadenosine; and a weaker activity was detected for deoxyguanosine. No nucleoside kinase activities were observed with any of the nucleosides. The presence of adenylate kinase was established, but no guanylate kinase activity was observed. The study provided evidence for the presence in H. pylori of salvage pathways for the biosynthesis of purine nucleotides.
De novo synthesis of pyrimidine nucleotides by Helicobacter pylori
Authors: Mendz G.L. , Jimenez B.M. , Hazell S.L. , Gero A.M. , O'Sullivan W.J.
Published: March 2008

The incorporation of pyrimidine nucleotide precursors into Helicobacter pylori and the activities of enzymes involved in their synthetic pathways were investigated by radioactive tracer analysis and 31P nuclear magnetic resonance spectroscopy. The bacterium was found to take up aspartate and bicarbonate and to incorporate carbon atoms from these precursors into its genomic DNA. Orotate, an intermediate of de novo pyrimidine biosynthesis, and uracil and uridine, precursors for pyrimidine pathways, were also incorporated by the micro‐organism. Radiolabelled substrates were used to assess the activities of aspartate transcarbamoylase, orotate phosphoribosyltransferase, orotidylate decarboxylase, CTP synthetase, uracil phosphoribosyltransferase, thymidine kinase and deoxycytidine kinase in bacterial lysates. The study provided evidence for the presence in H. pylori of an operational de novo pathway, and a less active salvage pathway for the biosynthesis of pyrimidine nucleotides.
A comparison of ELISA and RPLA for detection of Bacillus cereus diarrhoeal enterotoxin
Authors: Day T.L. , Tatani S.R. , Notermans S. , Bennett R.W.
Published: March 2008

Fourteen strains of Bacillus cereus isolated from different sources were examined for their ability to produce diarrhoeal enterotoxin by two commercial immunoassay kits (Oxoid BCET‐RPLA and Tecra ELISA) and the microslide immunodiffusion assay. One strain that was positive in monkey feedings, as well as a number of other strains isolated from diarrhoeal outbreaks, gave positive results in the ELISA and negative results in the RPLA test systems. When tested in the microslide assay, these strains produced only one antigen which formed a line of identity with the reference toxin. The results of the control toxins provided with the kits substantiated that the two commercial assays did not detect the same antigen. Cultures positive with both assay kits were shown to produce diarrhoeal enterotoxin (by a line of identity) and other antigens in the microslide immunodiffusion assay.
Proton‐ATPase activity in cells of lactobacilli grown in the presence of propionate
Authors: Chaia Adrians Pérez , Strasser de Saad Ana M. , de Ruiz Holgado Aída A. Pesce , Oliver G.
Published: March 2008

Lactobacillus helveticus ATCC 15009 and CRL 581, and Lact. casei LC3 were grown in a complex medium with and without 15 mmol 1‐1 of neutralized propionic acid and assayed for proton‐translocating ATPase activity. The enzyme activity was higher when the medium contained fatty acid than in its absence for all strains studied. Characteristics of this increased ATPase were identical to those of the enzyme located on the membrane of normal cells. The substrate consumption rate of resting cells was increased by propionate. This effect was reverted by the specific H+‐ATPase inhibitor N,N'‐dicyclohexylcarbodiimide indicating that the increment of fermentative activity was related to the H+‐ATPase activity. These results suggest that the amplification of H+‐ATPase activity could be involved in the inhibition of lactobacilli growth in cultures where propionic acid is unavoidably present, such as some mixed cultures with propionibacteria.
Fungicin M4: a narrow spectrum peptide antibiotic from Bacillus licheniformis M‐4
Authors: Lebbadi M. , Gálvez A. , Maqueda M. , Martínez‐Bueno M. , Valdivia E.
Published: March 2008

The strain Bacillus licheniformis M‐4 produces a 3.4 kDa hydrophilic peptide with antifungal activity, named fungicin M4. Analysis of the purified peptide shows that it contains the amino acids Glu (8), Arg (5), Pro (4), Tyr (8), Val (3), Met (2) and Orn (4). Its inhibitory spectrum is restricted to Microsporum canis CECT 2797, Mucor mucedo CECT 2653, Mucor plumbeus CCM F 443, Sporothrix schenckii CECT 2799, Bacillus megaterium and Corynebacterium glutamicum CECT 78. Fungicin M4 exerts biocidal activity on liquid cultures of Sporothrix schenckii CECT 2799.
Visible light damage to Escherichia coli in seawater: oxidative stress hypothesis
Authors: Gourmelon Michèle , Cillard J. , Pommepuy M.
Published: March 2008

The effect of visible light on Escherichia coli H10407 in seawater microcosms was investigated. Light damage was estimated by loss of colony‐forming ability. Illumination of E. coli suspended in oligotrophic seawater with visible light at an intensity of about 40 klux caused a drastic decrease of culturable bacteria which turned to a viable but non‐culturable state. In seawater E. coli exhibited weak metabolic activity as estimated by 3H methyl‐thymidine incorporation in the cell. Visible light did not significantly alter this metabolic activity and did not involve detectable oxidation of lipid membranes as evaluated by gas chromatography analysis of fatty acids. The involvement of oxygen and reactive oxygen species in phototoxicity was studied. A decrease of the toxic effect was observed when E. coli was exposed to visible light under anaerobic conditions. Scavengers of reactive oxygen species exhibited variable protective effects. β‐Carotene, a singlet oxygen scavenger, and superoxide dismutase were equally ineffective. On the other hand, catalase, which eliminates hydrogen peroxide and thiourea, a hydroxyl radical scavenger, showed a net protection. In addition desferrioxamine B, an iron chelator, was also effective in reducing phototoxicity, probably by preventing hydroxyl radical generation by decomposition of hydrogen peroxide in the presence of iron (Fenton reaction). Therefore, hydrogen peroxide and hydroxyl radical seem to be reactive intermediates of oxygen‐dependent (type II) photosensitized reactions.
Effect of relative humidity of hot air on the heat resistance of Bacillus cereus spores
Authors: Pfeifer J. , Kessler H.G.
Published: March 2008

The heat resistance to hot air of spores of Bacillus cereus (ATCC 14579) attached to carriers of stainless steel or silicone rubber was investigated in a range from 1% to 100% relative humidity (RH). Apart from an initial stage, linear survivor curves were obtained for all relative humidities. Neither the attachment itself nor the material of the carrier had an influence on the resistance. A distinct maximum of heat resistance was found at 40% RH. At 122°C the rate constants at 40% RH were five orders of magnitude smaller than at 100% RH and two orders of magnitude smaller than at 1% RH. At relative humidities of more than 40% the rate constants were strongly temperature dependent, whereas at lower relative humidities they were less temperature dependent. No significant influence of the relative humidity on the Arrhenius activation energy was found within each humidity range. The mean values were 295 kJ mol‐1 for relative humidities of 60% to 100% RH and 165 kJ mol‐1 for 1% to 20% RH. The occurrence of a maximum is ascribed to the existence of two inactivation mechanisms, the first is retarded and the second is accelerated by a reduction of relative humidity. It is assumed that the first mechanism is a protein denaturation. The second mechanism may be an oxidative process.
Inhibition of seed germination by Macrophomina phaseolina is related to phaseolinone production
Authors: Bhattacharya Dipanwita , Dhar T.K. , Siddiqui K.A.I. , Ali E.
Published: March 2008

The production of phaseolinone, a phytotoxic metabolite of Macrophomina phaseolina in infected Phaseolus mungo seeds grown on soil, was estimated by enzyme‐linked immunosorbent assay and HPLC. The degree of inhibition of seed germination correlated well with the amount of toxin produced; 50% inhibition was observed at a toxin level of 2.1 μg g‐1 of wet tissue. A comparison of the toxin‐producing ability of nine isolates of the fungus obtained from different hosts and localities showed that the strain MPK'83 produced a significantly larger amount of the toxin, both in liquid culture and in infected seeds. The virulence of the isolates was related to their ability to produce phaseolinone.
Influence of propionate on growth and fermentative activity of lactobacilli
Authors: Chaia A. Pérez , de Saad A.M.S. , de Ruiz Holgado A. Pesce , Oliver G.
Published: March 2008

Propionic acid was added to cultures of Lactobacillus helveticus and Lact. casei growing in a complex medium. The effect of different concentrations of this fatty acid on the growth kinetic, substrate consumption rate and coefficient and product formation rate was examined. Low concentrations of propionic acid produced a low increase or no modification of the growth rate of lactobacilli. By contrast, higher concentrations reduced the growth rate and substrate yields in all the strains. The fermentative activity of lactobacilli increased in all the cultures with propionate. When the concentration of glucose in the medium was low, the population density of all the strains at the stationary growth phase was lower in the presence of propionate than in control cultures. An increase in the concentration of glucose in the medium counteracted the inhibitory effect of propionate. The addition of lithium lactate to the medium gave greater inhibition even at low propionate concentrations. The inhibition results were explained by assuming that propionic acid could diffuse through cell membranes in the undissociated form, increasing the inward leak of H+ in the cells. The extrusion of H+ by the H+‐ATPase is possible by increasing the fermentative activity of the cells. When metabolism cannot supply the ATP required for proton extrusion, growth rate and biomass production decrease.
Thermostability of bacterial luciferase expressed in different microbes
Authors: Mackey B.M. , Cross D. , Park S.F.
Published: March 2008

Bacterial luciferase was used to investigate the relationship between the thermostability of a cytoplasmic reporter molecule and cellular heat resistance. The luciferase activity of Vibrio fischeri was expressed in strains of Escherichia coli, Salmonella typhimurium, Listeria monocytogenes and Brochothrix thermosphacta following transformation with plasmid pSP13 carrying the luxAB genes. The thermostability of intracellular luciferase varied depending on the organism in which it was expressed, but was not related to the cellular heat resistance of the different organisms. Addition of xylitol to the heating medium protected against loss of viability and inactivation of intracellular luciferase. Glycerol also protected against loss of viability but was less effective at preventing thermal denaturation of luciferase.