bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogenicity of live bacteria and extracellular products of motile Aeromonas isolated from eels
Authors: Esteve Consuelo , Amaro Carmen , Garay Esperanza , Santos Y. , Toranzo Alicia E.
Published: March 2008

The pathogenic activities in vitro and in vivo of live bacteria and extracellular products (ECP) of 24 motile Aeromonas strains were investigated. Most Aer. hydrophila and Aer. jandaei isolates were pathogenic for eels (LD50 105·4‐107·6 cfu fish‐1) but no Aer. sobria, Aer. caviae and Aer. allosaccharophila caused mortality in eels at doses of > 108·4 cfu fish‐1. Of these Aeromonas strains, Aer. hydrophila and Aer. jandaei in particular produced elastases and haemolysins against fish erythrocytes. ECP from Aer. hydrophila and Aer. jandaei caused degenerative changes in fish cell lines and were strongly toxic for eels (LD50 1·0–3·2 μg (g fish)‐1) reproducing the symptoms associated with natural disease. ECP from non‐pathogenic species were inactive on fish cell lines as well as being poorly lethal for eels (LD50 > 9·2 μg (g fish)‐1). All these biological activities of Aeromonas ECP were lost after heat treatment. These findings indicate differences between pathogenic and non‐pathogenic Aeromonas species with respect to the expression of virulence factors, and show that elastases, haemolysins and exotoxins play a leading role in the pathogenicity of motile Aeromonas for eels.
Bacteria in supragingival plaque samples can be killed by low‐power laser light in the presence of a photosensitizer
Authors: Wilson M. , Burns T. , Pratten J. , Pearson G.J.
Published: March 2008

The purpose of this study was to determine whether bacteria in supragingival plaque samples could be killed by low‐power laser light in the presence of a suitable photosensitizer. Plaque samples were obtained from 10 volunteers, treated with either toluidine blue O (TBO) or aluminium disulphonated phthalocyanine (AlPcS2), and then exposed to light from a helium/neon (HeNe) or gallium aluminium arsenide (GaAs) laser respectively. Following irradiation, substantial reductions were achieved in the total anaerobic count as well as in the number of viable streptococci and actinomyces present in the samples. In the absence of laser light, the sensitizers themselves had little effect on the viability of the bacteria in the plaque samples. The HeNe/TBO combination appeared to be more effective than the GaAs/AlPcS2 combination, achieving log10 reductions of 2·95, 5·40 and 3·34 in the total anaerobic count, streptococci and actinomyces respectively with a light energy dose of 1·31 J. If effective in vivo, lethal photosensitization may be useful as a means of eliminating plaque bacteria from a carious lesion prior to its restoration.
Application of an arbitrarily‐primed polymerase chain reaction to mycoplasma identification and typing within the Mycoplasma mycoides cluster
Authors: Rawadi G. , Lemercler B. , Roulland‐Dussoix D.
Published: March 2008

An arbitrarily‐primed polymerase chain reaction (AP‐PCR) was developed using a primer pair, Mlip1 and Mlip4, for members of the Mycoplasma mycoides cluster, a group containing important pathogens of small and large ruminants. Parameters that influence the reproducibility of this assay were optimized: magnesium, primer and template concentrations, and pH. AP‐PCR fingerprinting, carried out on a number of strains of each of the six species or subspecies belonging to the mycoides cluster, allowed the typing of strains within each group. The AP‐PCR assay showed that the cluster can be divided into two groups: (i) high and (ii) no genomic polymorphism variation. In addition, specific polymorphic bands for members of species or subspecies included in this cluster were amplified by this AP‐PCR method, thus allowing their identification.
Different inhibition of Lactobacillus delbrueckii subsp. bulgaricus by D‐ and L‐lactic acid: effects on lag phase, growth rate and cell yield
Authors: Benthin S. , Villadsen J.
Published: March 2008

Inhibition of Lactobacillus bulgaricus by lactic acids at constant pH is governed by two factors: the total concentration of lactic acids and the D/L ratio of lactic acid stereoisomers. L‐Lactic acid is more inhibitory than the D‐isomer, the latter being the only isomer produced by Lact. bulgaricus. The major inhibitory effect is an extremely prolonged lag phase (2–39 h for the range 0–25 g 1‐1 added lactic acids). Added lactic acids reduce the maximum cell concentration obtained in pH controlled fermentations, but have virtually no effect on maximum specific growth rate and on the yield of biomass on produced lactic acid. The added lactic acids have no effect on the growth‐related ATP consumption nor on the non‐growth related ATP consumption. The culture is heterogeneous since a part of the culture is unable to grow in the presence of L‐lactic acid. A different inhibitory effect of D‐ and L‐lactic acid has implications for yoghurt manufacture and potential for improved food preservation.
Fermentation of radiolabelled substrates by batch cultures of caecal microflora maintained in a continuous‐flow culture*
Authors: Hume M.E. , Nisbet D.J. , Scanlan C.M. , Corrier D.E. , DeLoach J.R.
Published: March 2008

Glucose‐ and lactose‐based media containing either 14C‐labelled glucose, galactose, lactose or lactic acid were inoculated with anaerobic cultures of chicken caecal bacteria maintained for 121 d in a continuous‐flow (CF) culture. The culture was previously shown to reduce Salmonella colonization in the caeca of chicks inoculated with the culture and the reduction was associated with increases in volatile fatty acids. The distributions of 14C were determined among the fermentation products, especially acetic, propionic and lactic acids. After 12 h of incubation and fermentation, variations were observed in the total amounts of 14C, from each 14C‐labelled substrate, detected as acetic and propionic acids in the glucose‐ and lactose‐based media, respectively: 92.9 and 89.4% of 14C‐glucose, 77.0 and 44.0% of 14C‐galactose, 0.0 and 76.9% of 14C‐lactose, and 76.5 and 93.2% of lactic acid in the two media, respectively. The results from this study indicate that carbohydrate metabolism by the CF culture was a major source of acetic and propionic acids and that lactic acid was an important metabolic intermediate for the synthesis of the volatile fatty acids.
Microbiological profile in Serra ewes' cheese during ripening
Authors: Macedo A.C. , Malcata F.X. , Hogg T.A.
Published: March 2008

The microflora of Serra cheese was monitored during a 35 d ripening period at three different periods within the ewe's lactation season. After 7 d ripening, the numbers of micro‐organisms reached their maximum, and lactic acid bacteria (LAB) and coliforms were the predominant groups. Pseudomonads were not detected after 1 week of ripening. At all stages of ripening, cheeses manufactured in spring exhibited the lowest numbers of LAB and yeasts, whereas cheeses manufactured in winter showed the lowest numbers of coliforms and staphylococci.

Leuconostoc lactis was the most abundant LAB found in Serra cheese whereas Enterococcus faecium and Lactococcus lactis spp. lactis exhibited the highest decrease in percentage composition. Numbers of both Leuc. mesenteroides and Lactobacillus paracasei tended to increase throughout ripening. The most abundant coliform was Hafnia alvei. Klebsiella oxytoca was found in curd but declined in number during ripening. Staphylococcal flora of curd was mainly composed of Staphylococcus xylosus, Staph. aureus and Staph. epidermidis. Staphylococcus xylosus was the major species found at the end of ripening. Pseudomonas fluorescens, was the only Pseudomonas species isolated from the curd. Although a broad spectrum of yeasts were found in Serra cheese, Sporobolomyces roseus was the most abundant yeast isolated.
Phenotypic and molecular characteristics of Aeromonas salmonicida subsp. salmonicida isolated in Southern and Northern Finland
Authors: Hänninen M.‐L. , Ridell J. , Hirvelä‐Koski V.
Published: March 2008

Aeromonas salmonicida subsp. salmonicida causes outbreaks of furunculosis in salmonid fish. Furunculosis was first detected in Finland in 1986 on fish farms located on the Finnish coast of the Bothnian Bay. Molecular methods, SDS‐PAGE, ribotyping, randomly amplified polymorphic DNA (RAPD) and plasmid profile analysis as well as phenotypic characteristics (biochemical characteristics, maximum growth temperature, pigment and elastase production) were used both for typing the strains and to study the possible routes of transmission of the organism to Finland and the spread of infection within Finland from 1986 to 1993. Ribopattern analysis of chromosomal DNA digested with SmaI, BglI, PstI and ClaI of 28 Finnish strains and eight foreign strains (Denmark, Sweden, Norway or Canada) showed that all Finnish strains and the Swedish strain originating from the Swedish coast of the Bothnian Bay had identical ribopatterns. All other foreign strains had distinct, unique ribotypes except for the second Swedish strain studied, the ribotype of which was identical with that of one Danish strain. RAPD typing, based on the results of two arbitrary primers, yielded 15 types for the Finnish strains. Except for both Danish strains, which had the RAPD type which was identical with that of one Finnish strain, the foreign strains had RAPD patterns differing from those of the Finnish strains. Plasmid profile typing and RAPD profile typing did not correlate. Ribotyping with four different enzymes proved to be the most sensitive method for studying genetically homogeneous Aer. salmonicida subsp. salmonicida. Ribopattern analysis showed that the infection which first started in 1984/1985 on the Swedish coast of the Bothnian Bay may have been transmitted to Finland where the first outbreaks occurred in 1986. The strains infecting Finnish fish farms were very homogeneous, with most differences seen, for example, in maximum growth temperature, plasmid profiles and the RAPD profiles of the strains.
Comparative study on cell envelope‐associated proteinases in natural isolates of mesophilic lactobacilli
Authors: Kojic M. , Fira D. , Bojovic B. , Banina A. , Topisirovic L.
Published: March 2008

Lactobacilli isolated from different natural sources were screened for the presence of cell envelope‐associated proteinases (Prt+ strains). Among them 17 of 75 tested isolates were Prt+. All Prt+ strains were producers of a serine‐type proteinase, since their proteolytic activity was inhibited by phenylmethylsulfonyl fluoride. Most of the natural isolates of mesophilic lactobacilli degraded only β‐casein such as Lactobacillus paracasei subsp. paracasei strains BGLI17 and BGLI18 and Lact. rhamnosus BGEN1. Only Lact. divergens BG742 cleaved all three, α‐, β‐ and κ‐caseins, even in the presence of Ca2+ ions. Total DNA isolated from Lact. paracasei subsp. paracasei strains BGLI17 and BGLI18 hybridized to the lactococcal proteinase gene probes originated from Lactococcus lactis subsp. cremoris Wg2. Hybridization could not be linked to the plasmid DNA, and pulse‐field gel electrophoresis analysis suggested that the proteinase genes of these two strains are most probably chromosomally located.
Rational development of a simple synthetic medium for the sustained growth of Lactococcus lactis
Authors: Cocaign‐Bousquet M. , Garrigues C. , Novak L. , Lindley N.D. , Loublere P.
Published: March 2008

The growth of two strains of Lactococcus lactis subsp. lactis from vegetable (NCDO 2118) and dairy origin (IL 1403) were compared on various culture media. Both strains grew more rapidly on a complex organic medium than on a defined synthetic medium. The best growth was obtained under nitrogen gas phase. The single omission technique was applied to each component of a non‐optimized synthetic medium in order to determine the true nutritional requirements. Requirements for macro‐elements, oligo‐elements, bases and vitamins were identical for the two strains. As expected, the dairy strain (IL 1403) was seen to be auxotrophic for some amino acids, whereas the vegetable strain (NCDO 2118) was seen to be prototrophic for all amino acids when using the single omission technique. Growth was then characterized on progressively simplified media and the composition of the absolute minimal media for the growth of both strains was defined. Sustained growth of the vegetable strain was only possible in minimal media supplemented with six amino acids (Glu, Met, Ile, Leu, Val, Ser), indicating that the definition of prototrophy/auxotrophy is partly dependent upon the medium composition. The dairy strain showed a requirement for Arg, His and Thr in addition to the six amino acids necessary for growth of the vegetable strain. The removal of ammonium salt from the medium did not affect the growth, illustrating that the amino acids may satisfy the totality of the nitrogen requirement for biomass synthesis.
The electrostatic nature of the spore of Pasteuria penetrans, the bacterial parasite of root‐knot nematodes
Authors: Afolabi P. , Davies K.G. , O'Shea P.S.
Published: March 2008

The response of spores of Pasteuria penetrans, the Gram‐positive obligate nematode hyperparasite, was studied in a direct current electric field and monitored using a microscope attached to a video recorder apparatus. Fluorescence measurements were performed on the spore's surface using HEXCO as a fluorescent probe. The mobilities of the spores and fluorescence measurements were performed in different salt concentrations and at different pH values. The results showed a significant electronegative potential at the spore surface which was dependent on the pH, salt concentration and valency of the cation present in the electrolyte medium. The results of the fluorescence experiments using HEXCO correlated well with the results obtained from the electrophoretic mobility experiments. A polyclonal antiserum raised to spores of P. penetrans affected the surface charge density and the data presented suggest that electrostatic interactions may be important in the binding of spores to the nematode cuticle. The binding of HEXCO to hydrophobic sites on the spores’ surfaces suggests the possibility of other attractive forces also being important in the binding process.
Significance of bile salt hydrolytic activities of lactobacilli
Authors: De Smet I. , Van Hoorde L. , Vande Woestyne M. , Christiaens H. , Verstraete W.
Published: March 2008

Bile salt hydrolase (BSH) activity was shown to be constitutive and substrate‐specific: the BSH isogenic Lactobacillus plantarum wild type (LP80 WT) and BSH overproducing LP80 (pCBH1) strains preferentially hydrolysed glycodeoxycholic acid (GDCA), whereas the hamster Lact. animalis isolates H362 and H364 showed a higher affinity for taurodeoxycholic acid (TDCA). In viability studies in the presence of nutrients, it was demonstrated that GDCA exerted a higher toxicity than TDCA in a pH‐dependent manner. This toxicity was inversely proportionate to the BSH activity level of the strains tested, indicating that BSH activity contributed towards bile salt resistance when appropriate nutrients were available. The high toxicity of GDCA relative to TDCA was suggested to be caused by their weak and strong acid properties respectively. It was therefore hypothesized that the protonated form of bile salts exhibited toxicity as it imported protons in the cell. This puts an energy‐burden on BSH− lactobacilli which undergo intracellular acidification. BSH+ cells primarily protect themselves through the formation of the weaker DCA compound, which can help negate the pH‐drop by recapturing and exporting the co‐transported proton. However, since DCA is more toxic than its conjugated counterparts, an additional energy‐dependent detoxification of DCA is suggested.
Efficiency of different enrichment and isolation procedures for the detection of Salmonella serotypes in edible offal
Authors: Arroyo G. , Arroyo J.A.
Published: March 2008

Rapid detection systems for Salmonella in foodstuffs are currently being developed. However, existing standards still call for application of traditional methods employing pre‐enrichment followed by selective enrichment and isolation. The efficacy of various methods was tested using 264 chicken and lamb organ meats. Pre‐enrichment was carried out in Tryptone Soy Broth (TSB) and enrichment in Tetrathionate Brilliant Green Broth (TTB) at 37°C, Selenite Broth with Brilliant Green and Sulphapyridine at 37°C and 43°C, and Rappaport‐Vassiliadis Broth (RV 10) at 42°C. The isolation media were Brilliant Green Agar (BGA), Deoxycholate Citrate Agar, Hektoen Enteric Agar (HEA) and Salmonella‐Shigella Agar.

Enrichment in RV/42°C followed by isolation on BGA as recommended by ISO standard no. 6579 and enrichment in TTB/37°C followed by isolation in HEA, no longer recommended by that standard, produced the best results. Low percentages of positive samples and difficulties in detecting Salmonella are the result of interference by competing organisms (Enterobacteriaceae) and the number of salmonellas present after enrichment.

A total of 528 samples (TSB, eggs, lamb liver and chicken liver) were inoculated with Salm. enteritidis, Salm. kapemba and Salm. virchow, and the preceding experiment was repeated. All the TSB and egg samples tested positive, but the percentage of positive samples from the lamb and chicken liver was only 81–92%. Recovery of the salmonellas did not depend upon the method employed or the serotype inoculated but instead on interference by competing flora and the numbers of Salmonella present in the samples.
Response of Saccharomyces cerevisiae strains to antineoplastic agents
Authors: Delitheos A. , Karavokyros I. , Tiligada E.
Published: March 2008

The effect of several antineoplastic agents on Saccharomyces cerevisiae strains has been investigated. Minimum inhibitory concentration (MIC), minimum cytotoxic concentration (MCC) and median effective concentration (EC50) were determined to identify strains with inherent sensitivity to the agents tested. Several strains proved to be sensitive to the antimetabolites 5‐fluorouracil and methotrexate as well as to doxorubicin and cis‐platine. On the contrary m‐amsacrine, procarbazine, vinca alcaloids, melphalan and hydroxyurea were inactive at concentrations up to 400 μg ml −1. The strain ATCC 2366, the most relatively sensitive to the agents tested, was used for studying the effect of treatment duration and of drug concentration on cell survival. Methotrexate and cis‐platine, which according to MIC and MCC tests seemed ineffective for this strain, reduced survival significantly after 6 h of treatment. A correlation of the shape of the survival curves with MIC and MCC values was attempted.
Biological indicators for low temperature steam and formaldehyde sterilization: the effect of defined media on sporulation, growth index and formaldehyde resistance of spores of Bacillus stearothermophilus strains
Authors: Wright A.M. , Hoxey E.V. , Soper C.J. , Davies D.J.G.
Published: March 2008

Preliminary screening was carried out on spores of 29 strains of Bacillus stearothermophilus to determine their potential as biological indicator organisms for low temperature steam and formaldehyde sterilization. Each strain was sporulated on four chemically defined media. Fourteen strains produced satisfactory sporulation on one or more of the media but there was considerable variation in the extent of sporulation. The growth index of the spores, which was dependent on both the strain of organism and the sporulation medium, ranged from 1% to 90%. The spores were appraised on the basis of their resistance to inactivation by 0.5% w/v formaldehyde in aqueous solution at 70°C. The survivor curves obtained could be characterized into five types on the basis of the shape of the curve. Only five strains of Bacillus stearothermophilus produced spores with the characteristics of high resistance, linear semi‐logarithmic survivor curve and high growth index that would be required of a potential biological indicator organism.
Evaluation of the MicroScan enzyme‐based system for the identification of foodborne yeasts
Authors: Deak T. , Beuchat L. R.
Published: March 2008

Eighty‐nine strains representing 36 species of foodborne yeasts isolated from fruit juice concentrates were identified using the Baxter MicroScan enzyme‐based kit, conventional tests according to a simplified identification method (SIM), and the API 20C kit. Of the 15 test species included in the MicroScan database, only 40% were correctly identified; 13% gave scores of unacceptably low probabilities, 20% were misidentified, and 27% could not be identified. Of the 21 test species not in the MicroScan database, 38% were misidentified and 62% produced biocodes with between‐species differences not larger than differences between strains within species. The reliability of the MicroScan enzyme‐based system is questioned, in that different results were sometimes obtained upon retesting the same strains. The MicroScan enzyme‐based system is rapid, providing results within 4 h. However, because of its restricted and specific database and unreliability, the system appears to be unsuited for the identification of foodborne yeasts.
Identification and characterization of Streptococcus thermophilus strains by pulsed‐field gel electrophoresis
Authors: Boutrou R. , Thuault D. , Bourgeois C.M.
Published: March 2008

The chromosomal DNA of a number of strains of the lactic acid bacterium Streptococcus thermophilus was analysed with the aim of rapidly differentiating and assessing the characteristics of each strain. Pulsed‐field gel electrophoresis was used to separate large DNA fragments formed by the restriction enzymes SmaI, SfiI or ApaI. Hybridization with a non‐radioactive DNA probe confirmed the identification of strains as Strep. thermophilus and analysis of the electrophoretic patterns differentiated some strains from others. A more extensive study of the pulsed‐field electrophoresis restriction patterns of new isolates of Strep. thermophilus may facilitate assessment of their technological properties by comparison of their restriction patterns with those of reference strains.
The antimicrobial activity of lactic acid bacteria from fermented maize (kenkey) and their interactions during fermentation
Authors: Olsen A. , Halm M. , Jakobsen M.
Published: March 2008

A total of 241 lactic acid bacteria belonging to Lactobacillus plantarum, Pediococcus pentosaceus, Lactobacillus fermentum/reuteri and Lactobacillus brevis from various processing stages of maize dough fermentation were investigated. Results indicated that each processing stage has its own microenvironment with strong antimicrobial activity. About half of the Lact. plantarum and practically all of the Lact. fermentum/reuteri investigated were shown to inhibit other Gram‐positive and Gram‐negative bacteria, explaining the elimination of these organisms during the initial processing stages. Further, widespread microbial interactions amounting to 85% to 18% of all combinations tested were demonstrated amongst lactic acid bacteria within the various processing stages, i.e. raw material, steeping, 0 h and 48 h of fermentation, explaining the microbial succession taking place amongst lactic acid bacteria during fermentation. The antimicrobial effect was explained by the combined effect of acids, compounds sensitive to proteolytic enzymes and other compounds with antimicrobial activity with the acid production being the most important factor.

The pattern of antimicrobial factors was not species‐specific and the safety and storage stability of fermented maize seem to depend on a mixed population of lactic acid bacteria with different types of antimicrobial characteristics. This means that introduction of pure cultures as starters may impose a risk to the product.
Relationship between colonial surface and density on agar plate
Authors: Chapuis C. , Rosso L. , Flandrois J. P.
Published: March 2008

The size of a colony on an agar plate is influenced by the number of colonies (N) on this plate. WhenNis small, colonies reach a larger size. The relationship between colonial surface and density of bacteria on agar plate was studied for nine bacterial and two yeast strains. A mathematical model describing the relationship between the logarithm base 10 of the number of colonies on the agar plate and the average colonial diameter was built. This model is shown to be adapted to most of the strains studied and could be a tool for media quality control.
Assessment of biological activity and fate of organic compounds in a reactor for the measurement of biodegradable organic carbon in water
Authors: Ribas F. , Frias J. , Ventura F. , Mohedano L. , Lucena F.
Published: March 2008

A new, rapid method for the determination of biodegradable dissolved organic carbon (BDOC), especially suited to water industry needs, was recently proposed by the authors. This dynamic method measured the BDOC of circulating water continuously pumped over a biofilm attached to a special support (sinterized porous glass) that fills a system of two glass columns. The BDOC value corresponds to the difference in dissolved organic carbon (DOC) between inflow and outflow water samples. The analytical results are not significantly different from those of other bioassays that use indigenous bacteria, and the total duration of the analysis is less than 3 h. However, a problem common to all the BDOC methods based on attached bacteria is the extent to which the decrease in DOC during the BDOC analysis is due to true biodegradation or to adsorption of organic matter to the reactor. In the present study, a reasonable support is provided for the hypothesis that this decrease, at least in the dynamic method, is predominantly due to microbiological activity. After comparing the support (sinterized porous glass) with a good physical adsorbent (granular activated carbon), the influence of temperature, residual chlorine and sodium azide on the reactor performance was tested, and a sensitivity only attributable to biological activity was observed. Another set of experiments were performed to assess the fate and specific elimination of different organic substances, explicable assuming that biodegradation processes were involved.
Dyes as fungal inhibitors: effect on colony enumeration
Authors: Bragulat M.R. , Abarca M.L. , Castellá G. , Cabañes F.J.
Published: March 2008

The effects of three dyes on the colony enumeration of nine fungal strains (including members of the Deuteromycetes and Zygomycetes) in pure and mixed cultures were investigated. Using malt extract agar as basal and control medium, the following dyes and concentrations were assayed: auramine (25 ppm), gentian violet (5 ppm) and malachite green (1 ppm). The chemicals commonly used in commercial media dichloran (2 ppm) and rose bengal (50 ppm) were included in the study as reference mould‐spreading inhibitors. Higher counts were usually obtained in the media containing dichloran, rose bengal or auramine, including the control medium in the absence of chemical when the mixed‐conidium inocula did not include a spreading mould. Nevertheless in most cases no significant differences were observed between them. Malachite green (1 ppm) performed mainly as a strong inhibitor of spreading moulds, only allowing adequate colony development and recoveries of both Fusarium and Aspergillus strains tested.
Specific antibody‐mediated detection of Brochothrix thermosphacta in situ in British fresh sausage
Authors: Stringer S.C. , Chaffey B.J. , Dodd C.E.R. , Morgan M.R.A. , Waites W.M.
Published: March 2008

S.C. STRINGER, B.J. CHAFFEY, C.E.R. DODD, M.R.A. MORGAN AND W.M. WAITES. 1995. A rabbit polyclonal antibody‐linked probe was developed which detected 76% of 800 food isolates of the spoilage bacterium Brochothrix thermosphacta when cells were bound to nitrocellulose. In slide cross‐reaction tests all six environmental isolates tested were stained but the type strain was not. The antibody did not cross‐react with Listeria grayi, L. monocytogenes, Lactobacillus plantarum, Lactococcus lactis, Streptococcus mutans, Bacillus cereus or B. subtilis.

The antibody‐linked probe detected Br. thermosphacta in thin sections of British fresh sausage when the viable count was greater than 106 g−1 Cells were detected mainly within 1 or 2 mm of the surface on the loose starchy material. They were not detected within muscle blocks or in the centre of the sausage. Such results suggest that growth of this organism occurs close to the surface of the sausage.
Locating nisin‐producing Lactococcus lactis in a fermented meat system
Authors: Stringer S.C. , Dodd C.E.R. , Morgan M.R.A. , Waltes W.M.
Published: March 2008

S.C. STRINGER, C.E.R. DODD, M.R.A. MORGAN AND W.M. WAITES. 1995. Antibody‐linked probes were used to locate nisin in a fermented meat system. Free nisin or nisin bound to susceptible cells or food components was not detected. Colonies of nisin‐producing Lactococcus lactis were stained at all times during growth. The position of nisin‐producing L. lactis colonies was noted and compared with the location of spoilage organisms or the distribution of areas with a fermented meat appearance. No relationship between the distribution of starter culture and the location of spoilage organisms or areas of fermentation was observed. In addition to the presence of L. lactis, a rapidly fermentable sugar was also required to obtain a fermented appearance and to reduce the levels of spoilage organisms.
Chitinase production by Streptomyces viridificans: its potential in fungal cell wall lysis
Authors: Gupta Rani , Saxena R.K. , Chaturvedi Priya , Virdi J.S.
Published: March 2008

R. GUPTA, R.K. SAXENA, P. CHATURVEDI AND J.S. VIRDI. 1995. Streptomyces viridificans was found to be a good chitinase producer among nine species of Streptomyces screened. Minimum levels of constitutive enzyme were observed with both simple and complex carbon substrate. Arabinose doubled the enzyme production amongst the various pentoses and hexoses used with chitin. However, with glucose end‐product inhibition and catabolite repression were observed. The enzyme tolerated a wide range of temperature (30–55°C) and pH (3–7˙5). Among various divalent cations Mn2+ and Hg2+ completely inhibited the purified enzyme while β‐mercaptoethanol stimulated its activity. Crude and purified enzyme had potential for cell wall lysis of many fungal pathogens tested.
Restriction fragment length polymorphism analysis of PCR‐amplified 16S ribosomal DNA of human Capnocytophaga
Authors: Wilson M.J. , Wade W.G. , Welghtman A.J.
Published: March 2008

M.J. WILSON, W.G. WADE AND A.J. WEIGHTMAN. 1995. The confusion in the taxonomic status of the genus Capnocytophaga has made identification of strains and studies on the role of this genus in infectious diseases equivocal. In this study 33 strains of Capnocytophaga including reference strains and various clinical isolates, were studied using RFLP analysis of 16S ribosomal RNA genes. The 16S ribosomal RNA (rRNA) gene sequences from whole cell suspensions and isolated genomic DNA samples were amplified by the polymerase chain reaction (PCR) using eubacterial specific primers. PCR products were purified and characterized by single digestions with 12 restriction endonucleases. Five of these, BanI, CfoI, HaeIII, HphI and RsaII were found to discriminate reproducibly between strains, and restriction patterns (ribotypes) produced by these were analysed to clarify the classification of Capnocytophaga strains. Dendrograms inferring similarities were derived from these data by the UPGMA method. This analysis produced three major clusters of strains, each of which was associated with a previously proposed species type strain: C. gingivalis, C. sputigena and C. ochracea. The results support the division of Capnocytophaga into three species and demonstrate that, despite the heterogeneity of this genus, the modified ribotyping method provides a simple, rapid and reproducible way to identify Capnocytophaga strains.
Influence of the incubation temperature on the autolytic activity of Lactobacillus acidophilus
Authors: Murga M.L. Fernändez , de Ruiz Holgado A. Pesce , de Valdez G.F.
Published: March 2008

M.L. FERNANDEZ MURGA, A. PESCE DE RUIZ HOLGADO AND G.F. DE VALDEZ, 1995. The effect of temperature and growth phase on the autolysis of Lactobacillus acidophilus CRL 640 was studied. The maximal rate of autolytic activity (ca 48% cell lysis) was found at 45°C. At this temperature, two peaks were detected: the first one at the early exponential phase of growth and the second lysis peak during the transition stage from the exponential to the stationary phase. The release of intracellular compounds absorbing at 260 and 280 nm was also detected at 45°C. The microscopic observations revealed morphological changes and the presence of ghost cells. At 37°C, the low autolytic activity obtained would be related to the normal cell cycle of growth.
The effect of a propionic acid bacterial inoculant applied at ensiling, with or without lactic acid bacteria, on the aerobic stability of pearl millet and maize silages
Authors: Weinberg Z.G. , Ashbell G. , Bolsen K.K. , Pahlow G. , Hen Yaira , Azriell A.
Published: March 2008

Z.G. WEINBERG, G. ASHBELL, K.K. BOLSEN, G. PAHLOW, Y. HEN AND A. AZRIELI. 1995. The effect of applying a new strain of Propionibacterium shermanii (PS), alone or with lactic acid bacteria inoculants (LAB) at ensiling, on the aerobic stability of pearl millet and maize silages was studied under laboratory conditions. The LAB inoculants comprised of Pediococcus pentosaceus (PP) in the experiments with millet, and PP +Lactobacillus plantarum (LP) in various combinations in the experiments with maize. The inoculants (made by Lallemand, France) were applied each at 0˙5 times 106 cfu g−1 Silages with no additives served as controls. The pearl millet used was either fresh, or wilted for 2 or 4 d (at 201, 268 and 448 g DM kg−1, respectively). There were two experiments with maize (at 401 and 353 g DM kg−1). After treatment, the chopped forages were ensiled in 15–1 anaerobic jars. Three jars per treatment were sampled on days 2, 5, 10 and 90. At the end of the experiments, the silages were subjected to an aerobic stability test lasting 6 d, in which CO2 production was measured along with chemical and microbiological parameters, to evaluate aerobic deteioration.

The PS inoculant resulted in improvement in the aerobic stability as compared with the control, only in the fresh and 2‐d wilted pearl millet silages. The amounts of CO2 (g kg‐1 DM) produced were 8˙5 ± 7˙7 and 6˙8 ± 1˙1 vs 18˙8 ± 22˙7 and 27˙0 ± 18˙5 in the PS treated and control of the fresh and 2‐d‐wilted pearl millet, respectively. All silages of the 4‐d‐wilted millet were stable upon aerobic exposure. In the first maize experiment the PS treatment and the control were more stable than the LAB inoculated silages. In the second experiment with maize, none of the silages were stable upon aerobic exposure; they showed increased pH values and CO2 production around 20 g kg‐1 DM.

The propionic acid bacteria inoculant had only a marginal effect on the aerobic stability of the pearl millet and maize silages, probably because it could not sustain under silage conditions.
M.T. Gorris1
Authors: Perombelon M.C.M. , Hyman L.J. , Wallace A. , Lopez M.M. , Cambra M. , Gorris M.T.
Published: March 2008

L.J. HYMAN, A. WALLACE, M.M. LOPEZ, M. CAMBRA, M.T. GORRIS AND M.C.M. PÉROMBELON. 1995. The characteristics of two monoclonal antibodies (Mabs), A23/1221.59.44.d.3 (1221) and A23/1239.36.64.e.2 (1239), against Erwinia carotovora subsp. atroseptica serogroup I produced in this study were compared with those of two other independently obtained Mabs, 4G4 in Spain and 4F6 in Canada, using different strains as immunogen and different screening procedures. The reaction pattern of Mabs 1221 and 1239 determined by indirect ELISA on over 200 bacterial strains including five E.c. atroseptica and 36 E.c. carotovora serogroups, seven Erw. chrysanthemi biovars, 23 other plant bacterial pathogens and 33 saprophytic bacteria from potato was similar to that of 4G4. Specificity for E.c. atroseptica serogroup I was improved, especially when skimmed milk (Marvel) was used instead of bovine serum albumin as blocking agent. Mabs 1221, 1239 and 4G4 reacted positively with all 22 E.c. atroseptica serogroup I, the dominant E.c. atroseptica sergroup on potato, strains tested and only with two out of five E.c. atroseptica serogroup XXII strains, one E.c. carotovora serogroup XXI strain and one strain of a saprophytic bacterium, Comamonas sp. Essentially similar results were obtained when examined by immunofluorescence. Characterization of the four Mabs showed that they were IgG3 and SDS‐PAGE/immunoblot results suggested that they were probably against the O‐side chain of bacterial cell wall lipopolysaccharides. In competition ELISA between biotin‐labelled and unlabelled Mabs, the competition pattern of the four Mabs was similar. Transformation of the data obtained by titrating the concentration of Mabs 1221, 1239 and 4G4 against a constant bacterial density using the direct linear plot method of Eisenthal and Cornish‐Bowden (1974), assuming an analogy between antibody‐antigen interaction and Michaelis‐Menten enzyme kinetics, indicated that Mab affinity (Km) and avidity (Vmax) were both highest for 4G4 and lowest for 1239.
Spray drying as a method for preparing concentrated cultures of Lactobacillus bulgaricus
Authors: Teixeira P. , Castro H. , Kirby R.
Published: March 2008

P. TEIXEIRA, H. CASTRO AND R. KIRBY. 1995. Spray drying and freeze drying as methods for concentration of Lactobacillus bulgaricus starter cultures were compared in terms of viability, lag phase until onset of pH decrease and total acid production. For the experimental conditions used, no significant differences were detected between the methods.

The effect of spray drying on the cell membrane of Lactobacillus bulgaricus was studied. Five separate methods were used to study the theory that spray drying causes cell membrane damage; three relating to leakage of intracellular components from the cell into the surrounding environment (260 and 280 nm absorbing materials, potassium ions and proteins); and two relating to increased cell permeability (increased sensitivity to NaCl and increased permeability to o‐nitrophenyl‐β‐D‐galactopyranoside (ONPG). Partial loss of some cytoplasmic material from the damaged cells was observed. The dried cells also became sensitive to NaCl and permeable to ONPG. Heat shock increased the survival of exponential cells as compared to controls but did not result in normal levels found with unshocked stationary phase cells. Heat shock had no effect on stationary phase cells. Different rehydration methods and media were investigated: slow rehydration increased survival.
Resistance of some wine spoilage yeasts to combinations of ethanol and acids present in wine
Authors: Kalathenos P. , Sutherland J.P. , Roberts T.A.
Published: March 2008

The most important factors affecting microbial growth in an alcoholic beverage are the ethanol content and the low pH. The effectiveness of different organic acids in conjunction with ethanol concentration in controlling growth of yeasts was determined for Saccharomyces cerevisiae, Schizosaccharomyces pombe, Brettanomyces lambicus, Pichia anomala, Zygosaccharomyces bailii, Saccharomycodes ludwigii and Kluyveromyces thermotolerans in malt extract broth (MEB). The results are summarized as undissociated concentrations of different acids required to inhibit growth of yeasts in MEB containing 10% (v/v) ethanol. About half the amount of undissociated malic or tartaric acid is necessary for inhibition of the yeasts, compared with acetic and lactic acid but the concentrations of acid necessary to inhibit growth were generally very high and unrealistic in wines for controlling growth of most of the yeasts tested. All the yeasts tested were able to grow in acidified non‐ or low alcoholic beverages but, at higher ethanol concentrations, Sacch. cerevisiae and Zygosacch. bailii have the greatest spoilage potential.
Comparative study of extracellular and intracellular β‐glucosidases of a new strain of Zygosaccharomyces bailii isolated from fermenting agave juice
Authors: Gueguen Y. , Chemardin P. , Arnaud A. , Galzy P.
Published: March 2008

A yeast strain isolated in the laboratory was studied and classified as a Zygosaccharomyces bailii. Both intracellular and extracellular β‐glucosidases of this yeast were purified by ion‐exchange chromatography, gel filtration and hydroxylapatite (only for the intracellular enzyme). The tetrameric structure of the two β‐glucosidases was determined following treatment of the purified enzyme with dodecyl sulphate. The intracellular β‐glucosidase exhibited optimum activity at 65°C and pH 5.5. The extracellular enzyme exhibited optimum catalytic activity at 55°C and pH 5. The molecular mass of purified intracellular and extracellular β‐glucosidases, estimated by gel filtration, was 440 and 360 kDa, respectively. Both enzymes are active against glycosides with (1 → 4)‐β, (1 → 6)‐β and (1 → 4)‐α linkage configuration. The intracellular enzyme possesses (1 → 6)‐α‐arabinofuranosidase activity and extracellular enzyme (1 → 6)‐α‐rhamno‐pyranosidase activity. The two β‐glucosidases are competitively inhibited by glucose and by D‐gluconic‐acid‐lactone and a slight glucosyl transferase activity is observed in the presence of ethanol. Since the glycosides present in wine and fruit juices represent a potential source of aromatic flavour, the possible use of the yeast β‐glucosidases for the liberation of the bound aroma is discussed.
Natural wine yeasts as biocontrol agents
Authors: Suzzi Giovanna , Romano Patrizia , Ponti I. , Montuschi Carla
Published: March 2008

A total of 586 natural wine yeasts, belonging to different genera, were tested for their antagonistic effect on fungal pathogens. A low percentage of yeast strains completely inhibited the pathogens and the biocontrol activity was found to be a strain characteristic and did not solely depend on species or genus. Among the antagonists, two strains of Saccharomyces cerevisiae and one of Zygosaccharomyces showed a broad spectrum of antagonistic activity against 10 fungal pathogens.
The ability of membrane potential dyes and calcafluor white to distinguish between viable and non‐viable bacteria
Authors: Mason D.J. , Lopéz‐Amorós R. , Allman R. , Stark J.M. , Lloyd D.
Published: March 2008

Various dyes were assessed for their ability to discriminate between viable and non‐viable bacteria. Two methods of killing were employed: by heat treatment or by gramicidin treatment. Staining was carried out in two ways; by staining directly in the medium or by washing cells prior to staining in buffer. Carbocyanine and rhodamine 123 dyes only exhibited small changes in fluorescence between viable and non‐viable populations of bacteria. Both oxonol dye (bis 1,3‐dibutylbarbituric acid trimethine oxonol) and calcafluor white proved much more useful.
Model experiments to establish behaviour of Yersinia enterocolitica O:9 strains in various types of fresh dry sausage
Authors: Kleemann J. , Bergann T.
Published: March 2008

In model experiments different kinds of raw sausages were inoculated with liquid cultures of virulent‐plasmid‐carrying clinical Yersinia (Y.) enterocolitica (e.) strains of the O:9 serotype, doses being between 104 and 105 cfu g‐1. The sausage samples were stored at 3–5° and 13–16°C. During the first 10 d of storage the Y.e. plate count was detected with Desoxycholate‐Citrate‐Lactose‐Sucrose Agar every day, later on in addition to it with phosphate buffer‐enrichment and with enrichment according to Schiemann (1982) in intervals of several days' duration. The pH and aw values, the contents of salt and water were detected. The multitude of complexly acting factors and substances prevents obviously the proliferation of Y.e. in fresh dry sausages. Decay dynamics of Y.e. were found to be considerably affected by storage temperature. Cold storage, basically, had a conservation effect and thus delayed the dying process of model strains. Yersinia enterocolitica‐contaminated fresh dry sausage may cause potential danger to consumers, because of relatively extended survival periods of the pathogen. Therefore, manufacturers are expected to observe most stringent hygienic rules of Good Manufacturing Practice.
Effect of a lactic starter culture on the growth and protease activity of Aeromonas hydrophila
Authors: Santos J. A. , López‐Díaz T. , García‐Fernández M.‐C. , García‐López M.‐L. , Otero A.
Published: March 2008

Lactococcus lactis subsp. lactis strain Lac 388 (isolated from goats' cheese made without starter) had inhibitory activity against three strains of Aeromonas hydrophila either by the plating method or by the associative culture approach (broth, skim milk and ewes' milk). Low pH was only partially responsible for the antagonism. Inhibition due to hydrogen peroxide and nutrient depletion was excluded. This inhibitory compound(s) was not destroyed by proteolytic enzymes. In mixed cultures the strains of Aer. hydrophila did not produce detectable amounts of protease.
Minimum inhibitory concentrations of intestinal Escherichia coli from broiler chickens after oral administration of apramycin
Authors: Kobe A. , Ebrecht A. , Fries R.
Published: March 2008

This study describes the influence of apramycin on minimum inhibitory concentrations (MIC) of intestinal Escherichia coli in young broiler chickens, after oral administration of the antibiotic at a dosage equivalent to a prophylactic course of treatment for 10 d. The bacteria were isolated from cloacal swabs and caecal contents. MICs were determined by agar dilution procedures. MIC of apramycin for the investigated strains ranged from 1 μg ml‐1 to 16 μg ml‐1. Strains obtained from undosed birds mainly had MIC values of 1 μg ml‐1. MIC values of 8 μg ml‐1 or more were recorded only among isolates obtained from chickens which had received apramycin. Administration of apramycin resulted in a slight but statistically significant increase in the average MIC. Statistically higher average MICs were recorded among isolates from cloacal swabs 10 d after withdrawal until the end of the experiment. For strains from caecal contents, this was demonstrated only on one sampling occasion, 15 d after withdrawal.
Continuous cultivation of Saccharomyces cerevisiae at different biotin concentrations in nutrient media
Authors: Pejin D. , Razmovski R.
Published: March 2008

An increase of biotin concentration in nutrient media increased the content of protein, phosphorus, total ribonucleic acids, activity of pyruvate carboxylase and isocitrate lyase in cells and decreased the content of trehalose, glycogen and respiratory quotient of yeast cells in the course of continuous cultivation of Saccharomyces cerevisiae.
Amino acid utilization by Lactococcus lactis subsp. cremoris FD1 during growth on yeast extract or casein peptone
Authors: Benthin S. , Villadsen J.
Published: March 2008

Quantitative analyses of the utilization of amino acids by Lactococcus lactis subsp. cremoris FD1 in yeast extract medium (YE) and in casein peptone medium (CP) have been performed. Both free and peptide‐bound amino acids were measured. In the CP most amino acids are peptide‐bound and some amino acids are virtually only present in peptides. Thirty‐six per cent of all peptide bonds in CP are hydrolysed during fermentation (6·3 mmol peptide bonds per gram biomass formed) and there is a transition of the growth rate related ATP consumption YxATP (mmol ATP g biomass‐1) from 25 mmol g‐1 to 71 mmol g‐1 coincident with a decrease of the peptide consumption. In YE most of the amino acids are on the free form and only 26% of the peptide bonds are hydrolysed during fermentation (1·5 mmol peptide bonds per gram biomass formed). A constant YxATP= 38 mmol g‐1 prevails throughout the fermentation in YE.