Showing papers in "Journal of Applied Microbiology in 1969"

The nitrogen nutrition of soil and herbage coryneform bacteria.

Abstract: Summary The nitrogen nutrition of 93 strains of soil and herbage coryneform bacteria and 16 named strains of Arthrobacter and Cellulomonas was examined. In testing for the ability of coryneform bacteria to utilize inorganic nitrogen as sole nitrogen source it was found necessary to use a medium containing a balanced mineral base and a suitable metal chelating agent in order to obtain reproducible results. A suitable medium is described. When provided with essential vitamins, 90% of soil isolates utilized inorganic nitrogen as sole nitrogen source while only 30% of herbage isolates did so. Sixty per cent of herbage isolates utilized inorganic nitrogen as major nitrogen source when provided with l-methionine in addition to vitamins, whereas no soil isolate showed a requirement for methionine. For a small residue of strains from each habitat the substrate nitrogen requirements were not determined. Of the named strains examined A. terregens utilized inorganic nitrogen as major nitrogen source when provided with methionine and vitamins while the remainder utilized inorganic nitrogen as sole nitrogen source. For 4 Arthrobacter spp. the nitrogen requirements described differ from those previously reported.

Action of Biguanides, Phenols and Detergents on Escherichia coli and its Spheroplasts

Abstract: Summary The bactericidal potency of groups of biguanides, phenols and detergents has been compared with that of the bis-biguanide, chlorhexidine, and related to measurable effects of the compounds on bacteria. Biguanides, like chlorhexidine, precipitated bacterial cytoplasm and also lysed spheroplasts over a limited concentration range: higher concentrations prevented lysis. Certain phenols and detergents which lysed spheroplasts did not precipitate cytoplasm. All the compounds released radioactivity from isotopically labelled bacteria; at suitable concentrations, biguanides released more radioactivity than chlorhexidine, but at higher concentrations the amount of radioactivity released was reduced. Bactericidal activity correlated with both the ability to lyse spheroplasts and to precipitate cytoplasm from solution. The findings support the hypothesis that damage to the cell wall alone does not kill bacteria but an increase in permeability allows entry of the bactericide. Action of compounds on the cell wall is discussed in relation to a model of its ultrastructure.

Effects of Food Intake on Numbers of Salmonellae and Escherichia coli in Rumen and Faeces of Sheep

Abstract: When 107–108Salmonella anatum or Salm. typhimurium were inoculated into the rumen of sheep consuming 1·3 kg of lucerne chaff daily, salmonellae were eliminated from the rumen in 2 days, and could not be detected in the faeces after c. 1 week. During starvation, both Escherichia coli and salmonellae grew in the rumen. Resumption of feeding after starvation for 3 days caused further multiplication of E. coli and salmonellae in the rumen. The organisms were subsequently eliminated with further feeding. Inoculation with as few as 400 salmonellae cells into a starved sheep led to large numbers of salmonellae appearing in the faeces and being excreted in varying numbers for at least 5 weeks after resumption of feeding.

Identification of Legume Nodule Bacteroids by the Fluorescent Antibody Reaction

Abstract: Summary A fluorescent antibody technique which permits rapid identification of legume nodule bacteroids and which permits the separation of bacteroid material and laboratory grown cultures of close serological affinity is described. Specificity of fluorescein isothiocyanate γ-globulin conjugates was increased with dilution. The ability of a medium sized clover nodule to produce sufficient bacteroid material for 20 fluorescent antibody stains allows increased accuracy and scope of the method. A single operator in 1 day may test > 400 nodules for one or more symbionts.

Fine Structure of Methane-utilizing Bacteria

Abstract: Summary. Thin sections of methane-utilizing bacteria have been examined in the electron microscope and the fine structure of the cells is described for the first time. The outstanding feature of all the isolates studied is the existence of intracellular membrane structures resembling those seen in nitrifying and photosynthetic bacteria. The possible significance of these membranes is discussed.

Lysis of Bacterial Spores with Hydrogen Peroxide

Abstract: Summary Spores of Bacillus cereus were made sensitive to lysis with H2O2 by treatment with reagents which break disulphide bonds (e.g. thioglycollic acid), by incubation with reagents which break hydrogen bonds (e.g. urea and lithium bromide) or by incubation at high temperatures. However, treated spores lost viability in the presence of H2O2 at the same rate as did untreated spores. Lysis was optimal at high pH values and in the presence of metal ions, e.g. Cu2+, suggesting that lysis was caused by free radicals formed by metal catalysed decomposition of the peroxide. Isolated spore coats, in contrast to whole spores, were lysed by H2O2 even when not pretreated. and the immediate products of spore coat lysis were soluble proteins; on continued incubation with H2O2 these proteins were degraded to low MW peptides and amino acids. It appeared that whole spores resisted lysis because peroxide sensitive bonds were masked by compact tertiary molecular structures, and that the sensitizing agents were able to loosen these structures sufficiently to expose bonds sensitive to H2O2.

Factors Affecting Production of Staphylococcal Lipase

Abstract: Summary Lipase production by the cells of Staphylococcus aureus is affected by aeration, agitation, age and pH value of the cultures during growth. At 37° the maximum production of both cells and lipase occurred within the pH range 6.5–9.0, with the optimum for cell production at pH 7.5–8.0 and the optimum for lipase production at pH 7.5–9.0. The presence of air was essential for lipase production, and the maximum lipase activity was produced in a culture incubated 5 days with agitation.

The Effect of Sodium Chloride on Heat Resistance and Recovery of Heated Spores of Bacillus stearothermophilus

Abstract: Increasing concentrations (2, 4 and 8% w/v) of sodium chloride in the heating medium progressively reduced the heat resistance of spores of Bacillus stearothermophilus Storage at 4° in water or in sodium chloride solutions had little effect on viable counts of unheated spores, but with the increase in sodium chloride concentration there was a reduction in the heat activation effect and a small decrease in heat resistance of the spores Increasing the severity of heat treatment rendered spores increasingly sensitive to sodium chloride in the plating medium

Growth and sporulation of Clostridium welchii in breast and leg muscle of poultry.

Abstract: Growth of a heat resistant, food poisoning strain of Clostridium welchii was followed in raw, minced breast and leg muscle of the chicken. Within the range 22–50° growth was slightly more rapid in the leg (pH 6·5–6·7) than in the breast (pH 5·6–5·7) and was fastest in leg muscle at 50°. No growth occurred at 15 or 52°. In a comparison between chicken and turkey, inoculated breast and leg muscle were cooked for 1 h at 85° and held at 37°. Multiplication of surviving organisms was initiated much more rapidly in chicken than in turkey meat, though the growth rates were comparable in each case. Sporulation of several strains of CI. welchii, including other heat resistant, food poisoning types, was generally 10–100 times greater in leg than in breast muscle of the chicken. Differences in sporulation could be attributed both to differences in pH and type of meat.

Serological Response Produced in Chickens by Three Strains of Mycoplasma gallisepticum

Abstract: Summary Three strains of Mycoplasma gallisepticum, S6, F and WS7, were used to infect 3 groups of broiler chickens. Serum antibody response was investigated using the stained antigen plate agglutination (SA) test and the haemagglutination inhibition (HI) test. The HI test was more strain specific and was associated with low molecular weight (IgG) antibodies. Chickens infected with one strain did not always give an HI reaction with the heterotypic antigen. The SA test was associated with high molecular weight (IgM) antibodies. Chickens infected with the three strains always reacted serologically with the homotypic and heterotypic SA antigens. In chickens infected with the S6 and WS7 strains, the IgM and IgG antibody titres remained consistently high during the period of the experiment; in chickens infected with the F strain, the IgG antibodies had disappeared by 7 weeks after infection although the IgM antibodies persisted.

The Use of Serratia indica and Bacillus subtilis var. niger Spores for Tracing Sewage Dispersion in the Sea

Abstract: Summary Experiments were conducted at 2 coastal sites to evaluate the suitability of Serratia indica and spores of Bacillus subtilis var. niger for tracing offshore and longshore dispersion of sewage released from submarine outfalls. Neither organism was found in the sea or the rivers studied prior to an experimental release and, whereas tracer spores persisted in the sea and the littoral zone for some days after release, S. indica disappeared within a few days. Where S. indica was released continuously from an outfall, it dispersed similarly to coli-aerogenes bacteria. Both tracers were killed rapidly in seawater exposed to sunlight, but their mortality kinetics differed. Tracer spores did not die or germinate in the dark when suspended in sewage during 24 h or in seawater during 9 days, but death occured after 3 days in seawater exposed to sunlight. Spores dispersed offshore similarly to K82Br and to S. indica; because of this and their stability, it was thought that they could be used for measuring physical dilution independently of mortality. The continuous release of S. indica into the sea is suitable for measuring the pollution field around a discharge; adding single doses of either tracer yields information on dispersion processes and transit times to the shore.

Aniline Utilization by a Soil Pseudomonad

Abstract: Summary A Pseudomonas sp., isolated from soil, grew with aniline as its sole carbon source. Washed cells oxidized aniline by an induced enzyme system and liberated ammonia. Washed, aniline-grown organisms oxidized without lag aniline, catechol, p-aminophenol and o- and m-toluidine.

Physiological and Morphological Characteristics of Kurthia zopfii Isolated from Meat Products

Abstract: Summary Kurthia zopfii was frequently isolated from meats, especially comminuted meats. Its proportion of the aerobic flora in such products at the point of production did not generally exceed 10%. It is not known to cause spoilage of refrigerated meats, but there is some evidence to suggest that its presence in the flora is indicative of high temperatures during the production, distribution, etc., of the product. Morphological and physiological characteristics of K. zopfii were examined, and it was found that the species could be divided into two distinct groups. There was no association between the group and the product from which it was isolated.

Influence of the Maillard reaction products on some bacteria of the intestinal flora.

Abstract: Summary Effects of the Maillard reaction products, which are obtained by heating glycine and dextrose solutions, on the cellular metabolism of some bacteria which constitute the intestinal flora were studied. Depending on the amounts present the growth rates and lag phases of the lactobacilli were increased, but growths of strains of Escherichia coli were unaffected, although their lag phases were extended.

Media Selective for Listeria monocytogenes

Abstract: Summary Of a number of substances tested for inclusion in media selective for Listeria monocytogenes, thallous acetate and nalidixic acid gave encouraging results at 30° and pH 7.0. Using these selective media, L. monocytogenes was recovered from artificially infected manure, soil, silage and grass.

Peat Culture of Rhizobium trifolii: an Examination by Electron Microscopy

Abstract: Peat cultures of Rhizobium trifolii strain TA1 were examined by electron microscopy of thin sections of aldehyde‐OsO fixed Araldite embedded particles, and scanning reflection electron microscopy of the peat particle surfaces. The Badenoch peat used showed plant cell wall fragments; membranes with dense‐light‐dense appearance in vesicular or linear form; tubular structures; other unidentified wall‐like fragments, all usually surrounded by a matrix of varying electron density and granularity. The general level of electron density was high, even in plant wall fragments, although some electron‐transparent spaces were present in the matrix. Remains of bacteria and actinomycetes were often found within the peat particles. Particle shape varied a great deal; the surface was irregular with many crevices. Rhizobium cells were found on the surfaces, and sometimes in crevices of the particles. Rarely > 10 cells were found together and the cells were usually several μm apart. The rhizobia were structurally similar to broth cultured log phase cells, but often the region between cell wall membrane and plasma membrane was very electron dense. The rhizobia were usually enmeshed in a fibrillar matrix connecting them to the peat particles; this was probably the film seen to cover the bacteria in scanning surface pictures.

Thermally Induced Changes in the Physical Properties of Staphylococcus aureus

Abstract: When suspensions of Staphylococcus aureus were stored at different temperatures in water or m sucrose, an increase or decrease (depending on the temperature of storage and the nature of the environment) in o.d. and light scattering properties occurred. Such changes were related to changes in cell size, leakage of intracellular constituents from the cells and precipitation of cytoplasmic material. Electron micrographs of ultrathin sections of cells illustrated some of these changes. The results demonstrated that caution was necessary in the interpretation of changes in o.d. and light scattering properties of this organism.

Some Effects of Preservatives on the Development of Bacterial Spores

Abstract: Summary The effects of preservatives on the development of spores of Bacillus subtilis have been examined using 2 indices of development sensitive to preservatives, namely, the swelling of spores prior to vegetative cell emergence and o.d. changes of spore suspensions during germination and outgrowth. The preservatives used fall into two categories: (1) inhibitors of germination (chlorocresol and mixed esters of p-hydroxybenzoic acid), and (2) inhibitors of postgerminative development (cetrimide, aminacrine and phenylmercuric nitrate). None of the preservatives prevented the initial phase of spore swelling and it is suggested that this is attributable to a nonmetabolic (inanimate) hydration. The inhibition of germination by a category 1 preservative (chlorocresol) is readily reversible by washing and to prevent germination the preservative must be added early in the process. The inhibition of postgerminative development by a category 2 preservative (aminacrine) cannot be reversed by washing treated spores.

Salmonellae in meat and poultry, poultry plant cooling waters and effluents, and animal feedingstuffs.

Abstract: Summary Although a low incidence of salmonellae had been found in 735 broiler chicks in 1961, none were found in 803 carcasses from 4 processing plants in 1966. Small numbers, mainly S. typhimurium, were found in the drains of 2 of these plants when swabs were left for several days. No isolations were made from the waters used to cool broilers or turkeys, or from 84 turkey carcasses. However, 39 of 444 (9%) of duck carcasses harboured S. typhimurium, and 9 of 22 (41%) of duck cooling waters were positive. Two isolations of S. typhimurium were made from 38 samples of pork sausages, and one of S. dublin from 125 samples of frozen boned-out beef. Three of 29 samples of cooked poultry meat were positive for S. typhimurium. In animal feedingstuffs 8 of 112 (7%) of samples of meat and bone meal had 7 different serotypes present, and salmonellae were also found in feather meal, blood meal and pig compound meal. S. typhimurium phage type 23 has been isolated from ducks, poultry meat, pork sausages and meat and bone meal, suggesting a chain of infection. The significance of the isolations of salmonellae from the various sources is discussed, and some methods of control suggested.

(Symposium on Myxobacteria and Flavobacteria: Paper X). Properties of Some Pectolytic, Yellow pigmented, Gram Negative Bacteria Isolated from Fresh Cauliflowers

Abstract: Pectolytic, yellow-pigmented, Gram negative bacteria formed 3·3% of the organisms isolated at 23° from fresh cauliflowers, and may contribute to deterioration of this vegetable in storage. The bacteria attacked glucose oxidatively in the Hugh & Leifson (1953) test, were nonmotile and oxidase-positive, conforming to definitions of the genus Flavobacterium. These strains showed differences in morphological and physiological properties from F. pectinovorum NCIB 9059, which has properties resembling those of Cytophaga spp.

(Symposium on Myxobacteria and Flavobacteria: Paper IX). Observations on the Taxonomy of Chromogenic Bacteria Isolated from Cannery Environments

Abstract: The yellow-orange chromogenic bacteria, commonplace in cannery environments, are capable of producing spoilage in a variety of presterilized milk-based canned products. A wide range of cultures of these arbitrarily defined flavobacteria, including the particular food spoilage types, were subjected to taxonomic studies. A possible scheme permitting the grouping of spoilage from nonspoilage types is presented.

The antagonism of enterococci on other bacteria in canned hams.

Abstract: Summary Enterococci can act antagonistically on selected species of Clostridium, Bacillus and Lactobacillus in a canned ham environment This phenomenon is a common feature of Streptococcus faecium, Strep, durans and Strep, faecalis The antibacterial agent elaborated by these enterococci is probably a metabolite that diffuses into the medium or meat and may play a role in the preservation of commercial products

Methods of Assessing the Psychrotrophic Bacterial Content of Milk

Abstract: Summary The various methods used for the determination of the psychrotrophic bacterial content of refrigerated milk are reviewed and assessed. A standard reference method, involving incubation of poured plates at 7° for 10 days, is recommended for the determination of psychrotrophic colony counts for investigational purposes. Many ingenious techniques, based on media selective for Gram negative bacteria, with incubation at higher temperatures and shorter times are described and appraised. A simple procedure which would provide a more rapid assessment of the number of active milk spoilage types of psychrotrophs is needed for routine purposes, and it is suggested that the enumeration of microcolonies by the drop plate or membrane filter methods with incubation at 7° for 72 h would provide a suitable technique for this purpose. Incubation of plates at 25° for 5 days is recommended as a standard reference method for determining the total colony count of bacteria in refrigerated milk, but for routine purposes where large numbers of milk samples are being examined incubation at 28–30° for 3–4 days would provide a sound enough estimate.

The ecology of serotype 4B of Bacillus thuringiensis.

Abstract: Summary Twentyfive separate isolates of serotype 4B of the aerobic sporeforming insect pathogen, Bacillus thuringiensis, have been obtained over the period 1961–68 Most of the isolates of this particular serotype were obtained from storage products insects infesting such places as grain stores, flour mills or ships carrying grain materials In one instance the organism was isolated from insects infesting Guinea corn growing in the field In comparison with the other serotypes of this bacillus the association with stored products environments is striking and, on several occasions, it has been possible to trace the distribution of the bacteria by movements of infested materials from one part of the world to another

Combined Effect of Salt Concentration and Redox Potential of the Medium on the Initiation of Vegetative Growth by Clostridium welchii

Abstract: Summary Four strains of Clostridium welchii grew in a medium containing 6% (w/v) of NaCl within 14 days at 37°. In one instance growth was obtained with 7% of NaCl from a large, but not a small, inoculum. Three of the strains grew from a large inoculum in the presence of 0.5 % of NaCl at Eh values of + 194 to + 238 mv. In a medium containing 5% of NaCl no growth occurred unless the Eh level was considerably reduced. The fourth strain was less affected until the NaCl concentration was increased to 6%.