Showing papers in "Journal of Applied Microbiology in 1976"

Production of plant growth regulators by rhizosphere phosphate-solubilizing bacteria.

Abstract: Culture supernatant fluids of 50 phosphate-dissolving bacteria isolated from rhizospheres of crop plants were examined for IAA, gibberellins and cytokinins. These bacteria possessed phytase activity and 27 could dissolve rock phosphate. Twenty bacteria synthesized all 3 types of plant hormones, 43 produced IAA, 29 formed gibberellins and 45 cultures produced cytokinin-like substances. Of the 50 bacteria tested 28 decomposed IAA. Plant growth inhibitors were detected in cultures of some isolates. The ecological significance of these rhizosphere bacteria and their mode of action when used as inoculants is considered.

Comparison of the Biochemical Properties of Bacteroides melaninogenicus from Human Dental Plaque and Other Sites

Abstract: A total of 45 strains of black-pigmented bacteroides, including Bacteroides melaninogenicus subsp. melaninogenicus, Bacteroides melaninogenicus subsp. intermedius and Bacteroides melaninogenicus subsp. asaccharolyticus, have been examined for morphological and physiological characteristics. They were also tested for the range of acidic metabolites, the typical basic amino acid of the mucopeptide, the base composition of DNA, the electrophoretic mobility of malate dehydrogenase and the susceptibility to certain antibiotics. The subspecies most commonly isolated from supragingival human dental plaque are B. melaninogenicus subsp. intermedius and B. melaninogenicus subsp. melaninogenicus. A list of tests for the differentiation of the three subspecies is given, but the separation of B. melaninogenicus subsp. asaccharolyticus from the other two subspecies of B. melaninogenicus is nevertheless recommended.

Oxidation of arsenite by a soil isolate of Alcaligenes.

Abstract: A strain of Alcaligenes, isolated from soil and grown in nutrient broth in the presence of arsenite, possessed the ability to oxidize arsenite to arsenate. Washed cell suspensions consumed one-half mol of oxygen/mol of arsenite and produced arsenate. The optimum pH for arsenite oxidation was 7.0. The Km for arsenite was 1.5 × 10-4 M and Vmax was 6.7 μl of oxygen/min. The arsenite-oxidizing enzyme system was induced by growth in arsenite. Response of the arsenite-oxidizing enzyme system to respiratory inhibitors suggested that electrons resulting from arsenite oxidation by an oxido-reductase with a bound flavin are transferred via cytochrome c and cytochrome oxidase to oxygen. The presence of the cytochromes in crude extract was confirmed by spectral measurements.

Substrate limitation of bacterial growth at meat surfaces.

Abstract: Utilization of the low molecular weight, soluble components of meat by an anaerobic and an aerobic spoilage bacterium was examined. During growth of the anaerobe in a meat juice medium, the only substance utilized in detectable amounts was glucose. The growth of the bacterium on the surface of meat was limited by the rate of diffusion of fermentable substrates from within the meat to the surface. The aerobe utilized amino acids and lactic acid when glucose was exhausted. The growth of the bacterium on the surface of meat was not limited by substrate availability or by the increased pH at the surface resulting from degradation of amino acids.

The Thermal Denaturation of Partly Purified Bacterial Deoxyribonucleic Acid and its Taxonomic Applications

Abstract: 1 Partly purified DNA and the corresponding highly purified DNA was obtained from 25 strains of Gram negative, rod-shaped bacteria. 2 The DNAs were examined by the thermal denaturation method and the melting temperatures of both partly and highly purified DNA samples from the same strain were in close agreement. 3 For all strains, the mean difference in G+C contents estimated from the melting temperatures of each partly and highly purified DNA was 0.4% G+C. 4 The presence of residual RNA and protein in the partly purified DNA samples contributed to variations in the total hyperchromism but did not significantly affect the accuracy of the melting temperature determination.

The Effect of Sugars and Polyols on the Heat Resistance and Morphology of Osmophilic Yeasts

Abstract: Heat resistance at 65· of Saccharomyces rouxii and Schizosaccharomyces pombe was enhanced in solutions of sugars and polyols, containing 0·1 M-phosphate buffer, pH 6·5, at a water activity of 0·95. Resistance was maximum in solutions of sucrose, less in sorbitol and least in solutions of glucose, fructose and glycerol. Examination of the yeast cells by phase contrast microscopy showed shrinkage of cells in all solutions. Electron microscopy of freeze-etched preparations of Sacch. rouxii indicated plasmolysis of cells in sucrose and sorbitol solutions only.

The characterization of clinically important gram negative anaerobic bacilli by conventional bacteriological tests.

Abstract: One hundred and sixty-five reference strains and laboratory isolates of Gram negative, non-sporing, anaerobic bacilli were subjected to a series of simple laboratory tests that were initially selected for their discriminatory value. Conventional biochemical tests, tests of resistance to antibiotics, and tolerance to dyes and bile salts were included. These tests allowed a clear separation of strains into three main groups: Bacteroides fragilis, B. melaninogenicus and Fusobacterium spp. Certain tests were found useful for identifying recognized subspecies of B. fragilis and B. melaninogenicus. A scheme for the identification of unknown laboratory isolates of Gram negative anaerobic bacilli is presented.

Methods for Examining the Microflora of Mouldy Hay

Abstract: A comparison of four methods of estimating the microflora of mouldy hay showed that more micro-organisms were removed by washing samples than by blowing in a small wind tunnel. By contrast, actinomycete spores were estimated more efficiently from air using an Anderson Sampler than by plating diluted washings because fewer bacteria were blown than washed off the hay. Estimates of fungal spores were larger from counts in haemocytometer cells than by dilution plating but counts of actinomycetes and bacteria were higher by dilution plating. Fungi grew equally well from air or water suspensions and with the Cascade Impactor and Anderson Sampler their numbers were estimated with less variation than for the numbers of ‘actinomycetes and bacteria’even on improved media and after correcting for viability, clumping and interference between colonies.

The occurrence of aflatoxin-producing strains of Aspergillus flavus in the mould floras of ground spices.

Abstract: All of 20 different ground spices and three mixtures purchased locally were significantly contaminated by bacteria, and only cloves were free of moulds, but thermophilic actinomycetes were isolated from only six spices. In general, the mould floras were dominated by Aspergillus spp.: A. glaucus (group) and A. niger being the most common. A. flavus was found in 14 spices and seven of 24 strains examined produced aflatoxins in vitro. Whole ginger and Jamaica, red and white peppers supported growth of A. flavus strains and production of aflatoxins.

Taurolin, a New Chemotherapeutic Agent

Abstract: Taurolin, bis-(1,1-dioxo-perhydro-1,2,4-thiadiazinyl-4)-methan, is a novel, broad spectrum, non-systemic chemotherapeutic agent. It is effective in vivo against a wide range of pathogenic organisms including Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, and Salmonella typhimurium, and would be of particular use against antibiotic-resistant organisms. It is based on an endogenous substance, taurine, which acts as a non-toxic formaldehyde carrier donating methylol groups to bacterial protein and endotoxin thus causing denaturation and polycondensation of the pathogens and their pyrogens. It is anticipated that Taurolin will be of value in the treatment of faecal peritonitis.

A simplified method for the isolation of Bacteroides nodusus from ovine foot-rot and studies on its colony morphology and serology.

Abstract: A simple method for the isolation of Bacteroides nodosus from foot-rot lesions in sheep is described together with observations on the colony morphology of freshly isolated strains and variant colonies arising on subculture in the laboratory. Serological results from a study of English isolates demonstrate a multiplicity of types based on the K antigens as well as additional antigens common to all strains.

Investigations on a metabolite from Lactobacillus bulgaricus which neutralizes the effect of enterotoxin from Escherichia coli pathogenic for pigs.

Abstract: Eleven species of lactic acid bacteria when grown on a milk-based medium reduced the pH value to < 4.7. The cells of nine of these species inhibited the growth of Escherichia coli on agar in Petri dishes. However, only Streptococcus faecium and Lactobacillus bulgaricus gave significant cell free anti-E. coli activity. Activity against E. coli enterotoxin was also found only in two species. L. bulgaricus and S. faecalis. Part of the activity in the former species was cell free. Further investigation of the cell-free anti-enterotoxic activity from L. bulgaricus showed that it had a low molecular weight probably < 103, was not very stable and was independent of the anti-E. coli activity. Broths containing L. bulgaricus fermented to produce high levels of antienterotoxin were beneficial when added to diets for early weaned pigs. It was inferred that this effect was likely to be caused by the anti-enterotoxic activity.

Heat Resistance Studies on Yeast spp. Causing Spoilage in Soft Drinks

Abstract: A test method to investigate the heat resistance of yeasts has been developed The method was used to study the heat resistance of 120 yeast strains, representative of the fungal flora in soft drinks and certain acid food products: 35 asporogenous yeast strains (Brettanomyces, Candida, Kloeckera, Rhodotorula and Torulopsis) and 85 ascomycetous strains (Debaryomyces, Hansenula, Kluyveromyces, Lodderomyces, Pichia, Saccharomyces and Saccharomycopsis) were tested Generally, asporogenous yeasts were found to be less heat resistant than ascomycetous types The genus Saccharomyces showed the highest heat resistance, especially strains of the species Sacch cerevisiae and Sacch chevalieri For an evaluation of the practical implications of these results additional studies on environmental factors influencing the heat resistance of ascomycetous yeast species are required

Production of cell-bound proteinase by Lactobacillus bulgaricus and its location in the bacterial cell.

Abstract: Lactobacillus bulgaricus NCDO 1489 produced a single, cell-bound proteinase during growth on nutrient medium at 45°C. Proteinase activity was optimal at 45–50°C and pH 5.2–5.8. and was inhibited by chelating agents. The enzyme was mainly associated with the cell envelope but could be liberated from cells under conditions favouring autolysis or by treatment of the cells with lysozyme. Its relation to the growth of the organism in milk and possible role in formation of fermented milk products are discussed.

The Application of Miniaturized Methods for the Characterization of Various Organisms Isolated from the Animal Gut

Abstract: Miniaturized methods for the characterization of streptococci, lactobacilli and aerobic Gram negative rods are described and the results obtained with 461 cultures from the calf rumen and quail gut tabulated. The methods afford a considerable saving in time and materials without concomitant loss of accuracy.

Effect of Temperature and Added Polyphosphate on the Survival of Salmonellae in Poultry Meat during Cold Storage

Abstract: 1 The behaviour of five salmonella serotypes in minced chicken breast (pH 5.8) and leg muscle (pH 6.4) held at 1 °C, -2 °C, -5 °C and -20 °C was studied with and without the addition of 0.35% polyphosphate (Puron 604). 2 In the absence of polyphosphate, survival of the test organisms was greater in breast than in leg muscle at all four temperatures, but was greatest at -20 °C in both types of muscle and least at -2 °C and -5 °C, just above and below the freezing point of the muscle. 3 Addition of polyphosphate increased the death rate of the salmonellae in breast muscle held at -2 °C and to a lesser extent at -20 °C but had little or no effect in leg muscle or in breast held at 1 °C or -5 °C.

Role of Azotobacter paspali in Association with Paspalum notatum

Abstract: Azotobacter paspali grows in the rhizospheres of Paspalum notatum where it is thought to fix nitrogen actively and hence improve pasture growth. In the experiments described here A. paspali improved growth primarily by producing growth regulating substances. Nitrogenase activity was not detected in rhizospheres of young plants. Its occurrence in older plants was not necessarily associated with the presence of A. paspali and was greater in the rhizopheres of control than of inoculated plants.

Antibacterial activity of ambodryl and benadryl.

Abstract: Of nine antihistamines screened for in vitro antibacterial activity, ambodryl (bromodiphenhydramine hydrochloride) and benadryl (diphenhydramine hydrochloride) were the most active. At 50 to 100 μ/ml concentrations these inhibited a large number of Gram negative and Gram positive bacteria in vitro, with ambodryl having a broader spectrum. In vivo tests showed that the compounds at single doses of 3 and 1.5 μg/g body weight protected mice against a challenge with a virulent strain (LD50) of Salmonella typhimurium, and also significantly reduced the multiplication of this organism in the liver, spleen and blood of the protected animals in comparison with the unprotected controls.

Dissimilatory nitrate and nitrite reduction under aerobic conditions by an aerobically and anaerobically grown Alcaligenes sp. and by activated sludge

Abstract: The oxygen uptake of an Alcaligenes sp., isolated from activated sludge, was inhibited by small amounts of nitric oxide. The occurrence of this inhibition was dependent on the growth conditions and the pretreatment of the cells. Anaerobically grown cells, which had subsequently been aerated in a nitrogen-free medium, accumulated nitric oxide, after the addition of nitrate or nitrite. When the oxygen uptake was inhibited by nitric oxide, dissimilatory reduction of nitrate and nitrite proceeded under aerobic conditions at the same rate as in the absence of oxygen. Activated sludge removed nitric oxide actively under aerobic conditions and as a consequence the oxygen uptake of the sludge was not inhibited in the presence of nitrite. The rate of nitrate reduction under aerobic conditions was about 20% of that in the absence of oxygen.

An investigation of antibiotic and drug residues in fish.

Abstract: The use of antibiotics and drugs in fish farming has prompted an investigation into the elimination of these residues from fish muscle. Young rainbow trout were given intraperitoneal injections of either chloramphenicol, framycetin, oxytetracycline or sulphadiazine/ trimethoprim and muscle tissue was examined by microbiological assay over a period of weeks for the presence of active residues. The effect of the method of administration of two of the drugs was also investigated and the results discussed.

The distribution of O-antigen types of Escherichia coli in normal calves, compared with man, and their R plasmid carriage.

Abstract: The distribution of O-antigen types of Escherichia coli in calves over a ten-month period has been determined. A total of 400 calves from separate farms located over a wide area of England and Wales have been surveyed. Of the 148 O-types recognized, 93 were found in calves, compared with 107 in a previous survey in man; 42 of these were common to both hosts. In calves 60% of isolates were resistant to at least one antibiotic. Of these, 71% belonged to ten O-types, 9 of which were found in man. It is concluded that calves form a potential reservoir of R plasmid carrying E. coli.

Isolation of Actinomycetes and Fungi from Mouldy Hay using a Sedimentation Chamber

Abstract: 1 Actinomycetes and fungi causing farmers’lung and infections in man and animals were isolated preferentially using an Andersen sampler after shaking spores from mouldy hay in a sedimentation chamber. 2 Actinomycetes were isolated after 2 h sedimentation and Aspergillus fumigatus and Absidia spp. after 30 min.

Simple media containing stabilized tributyrin for demonstrating lipolytic bacteria in foods and soils.

Abstract: A medium containing tributyrin stabilized with polyvinyl alcohol was used to demonstrate the lipase activity of bacteria in foods. A modification of this new medium enables a search to be made for lipolytic bacteria in soil.

Application of flow microcalorimetry to analytical problems: the preparation, storage and assay of frozen inocula of Saccharomyces cerevisiae.

Abstract: A simple procedure for the freezing of large batches of yeast inocula (up to 150 samples) for storage at liquid nitrogen temperatures with the retention of high viability after thawing is described. The recovered frozen cells were examined using a flow microcalorimetric procedure which enables a rapid determination of viability. The application of such inocula to antibiotic assays and growth studies is discussed.

A Simple and Sensitive Technique for Determining the Fermentation Reactions of Non-sporing Anaerobes

Abstract: 1A new technique is described for determining the fermentation reactions of non-sporing anaerobes. 2The fermentation reactions are carried out on horse blood agar plates to which fermentable substrates are added. 3The technique is simple, sensitive and yields reproducible fermentation patterns.

A longitudinal study of Escherichia coli in cows and calves with special reference to the distribution of O-antigen types and antibiotic resistance.

Abstract: The faecal excretion of E. coli from 6 adult cows was followed over a period of 105 days. E. coli were excreted in only 23·4% of specimens and the patterns of excretion varied between animals. All isolates of E. coli were antibiotic sensitive and fell into 6 O-antigen types; very few were non-typeable. The O-types excreted by each animal, compared with those from other cows in the same house, were traced with time. A similar but less intense study was undertaken in 8 calves. In contrast E. coli was excreted from all samples and included both antibiotic sensitive and resistant strains; 37 O-types were represented. The persistence of specific O-types within each calf and their spread to other calves in the same house were studied. A comparison of the O-types in the bovine species with those isolated from man has been made.

An Evaluation of Commercial Thiosulphate Citrate Bile Salt Sucrose Agar (TCBS)

Abstract: The recovery of vibrios, in particular Vibrio cholerae, non-cholera vibrios and V. parahaemolyticus, on four brands of TCBS has been compared. The selectivity of the media was also compared. Eiken TCBS performed best in our tests but was closely followed by Oxoid TCBS.

Effects of temperature and nutrients on proteinase production by Pseudomonas fluorescens and Ps. aeruginosa in broth and milk.

Abstract: Temperature and the composition of the medium influenced the production of proteinase by Pseudomonas fluorescens and Pseudomonas aeruginosa isolated from raw milk. Many isolates of Ps. fluorescens digested litmus milk at 10° but not at 5° or 2°. With Ps. fluorescens proteinase production per unit of growth in a Peptone–Yeast Extract broth declined progressively as the incubation temperature was reduced from 20° to 5°. At 30° there was heavy growth in the same medium but only slight proteinase production whereas enzyme production by Ps. aeruginosa was maximal at this temperature. Proteinase production by both species in semi-defined media was essentially a function of the organic nitrogen content of the medium; there was evidence of catabolite repression by glucose and, to a lesser extent, lactate. In milks seeded with these pseudomonads, the extent of proteolysis was either increased markedly or slightly decreased when glucose was included.