Showing papers in "Journal of Applied Microbiology in 1958"
TL;DR: A quantitative study of the growth and carbohydrate metabolism of Aerobacter aerogenes in continuous culture with particular reference to 2:3-butanediol production is described, with no sign of loss of butanediol-producing ability by any of the cultures.
Abstract: SUMMARY: A quantitative study of the growth and carbohydrate metabolism of Aerobacter aerogenes in continuous culture with particular reference to 2:3-butanediol production is described. The effects of varying dilution rate, oxygen uptake rate, pH value, temperature and CO2 pressure were studied.
The optimum pH value was 5·0°6·0. The optimum temperature was 35–37° with a dilution rate of 0·2 hr−1. The rate of sugar metabolism was decreased by raising the CO2 pressure.
In continuous culture the maximum diol output rate/1. of working volume exceeded the greatest rate reported for batch culture by a factor of three. The maximum diol concentration and yield as a percentage of the theoretical maximum were lower in continuous culture than in batch culture. Reasons for this are given.
Some variants of the parent organism were found in continuous cultures but they caused no change in the yield of butanediol. There was no sign of loss of butanediol-producing ability by any of the cultures, some of which were maintained for 2,000 hr. For the first few generations the rate of production of butanediol actually increased.
64 citations
TL;DR: A study was made of selected properties of 189 psychrophilic bacteria isolated from chilled beef and associated sources, finding that flagellar characters were associated with the production of green pigment, with theProduction of acid from lactose and with resistance to several antibiotics.
Abstract: SUMMARY: A study was made of selected properties of 189 psychrophilic bacteria isolated from chilled beef and associated sources. Of these, 182 were Gram-negative and 7 were Gram-positive. Of the former, 128 were typical pseudomonads with polar flagella. They were resistant to penicillin and oxidized glucose to acid. There were 52 non-motile Gram-negative bacteria of which 42 were judged to be pseudomonads on the basis of penicillin resistance and the oxidation of glucose to acid. Flagellar characters were associated with the production of green pigment, with the production of acid from lactose and with resistance to several antibiotics.
55 citations
TL;DR: Spoilage in both control and antibiotic treated poultry was accompanied by a rise in pH in the contaminated muscles, but for various reasons this change could not be used as a direct measure of the extent of the microbial contamination.
Abstract: SUMMARY: Chlortetracycline, oxytetracycline and tetracycline, incorporated at 10 p/m in the ice slush used for cooling, were equally efficient in extending the storage life of eviscerated poultry which was subsequently frozen, thawed and stored at 1°. There was complete correlation between the sensory assessment of ‘off’odour and the total numbers of micro-organisms present when these were determined by taking bulk samples of skin from the area under the wing and of the surface tissue of the visceral cavity near the vent. Direct microscopical counts confirmed that the latter area was the most heavily contaminated part of the visceral cavity. Non-pigmented strains of Pseudomonas were the main spoilage organisms of untreated chickens but Achromobacter strains and yeasts were responsible for the spoilage of the chlortetracycline treated chickens. Fluorescence was only observed in spoiled chickens where pigmented strains of Pseudomonas occurred in significant numbers. Spoilage in both control and antibiotic treated poultry was accompanied by a rise in pH in the contaminated muscles, but for various reasons this change could not be used as a direct measure of the extent of the microbial contamination.
50 citations
TL;DR: In this article, the application of a radial mechanical shaft seal and other improvements to a 2.3 1.5-capacity culture vessel were described, and the performance of the shaft seal was evaluated.
Abstract: SUMMARY: The application of a radial mechanical shaft seal, and other improvements to a 2–3 1. capacity culture vessel, are described.
41 citations
TL;DR: The thermal death curves for spores suspended in milk yielded Q10 values of about 30 in the range 110–120°, higher than the figures previously reported in the literature for R. subtilis spores.
Abstract: SUMMARY: Thermal death curves for spores of Bacillus subtilis 786 have been determined in water and in milk Generally a non-logarithmic order of death was observed Numbers of survivors were lower in milk than in water, suggesting that there may be inhibitory factors in UHT sterilized milk which affect the germination and/or subsequent growth of heated spores
The thermal death curves for spores suspended in milk yielded Q10 values of about 30 in the range 110–120° This is higher than the figures previously reported in the literature for R subtilis spores Spores of a number of strains of B subtilis were compared with strain 786 and all gave high Q10 values
The results obtained in this work have been used to predict the destruction of spores at higher temperatures in a UHT plant (Burton et al 1958) The calculated values agree well with the results obtained in the plant by Franklin et al (1958)
28 citations
TL;DR: There was a marked seasonal variation in the B. cereus index of raw milk supplies; maximum numbers were obtained from July to September and minimum numbers in April and May.
Abstract: SUMMARY: Methods for determining the Bacillus cereus content of milks and of rinses of dairy equipment are described and their limitations discussed. Milk samples from various sources were examined throughout the year for ‘bittiness’ as well as for B. cereus. The organism was not detected in all samples showing bittiness. There was a marked seasonal variation in the B. cereus index of raw milk supplies; maximum numbers were obtained from July to September and minimum numbers in April and May. Rinses of farm dairy equipment yielded few B. cereus spores but milk cans not uncommonly contained large numbers, especially in the summer months, when 10·5% of cans showed more than 5 × 103/can. Preliminary observations on other sources of B. cereus are described and some of the problems of the control of this organism in raw milk supplies are discussed.
25 citations
24 citations
TL;DR: A medium is described by means of which cells of Bacillus cereus in milk may be estimated without the prior use of a heat treatment, providing information additional to that obtained by plating after aHeat treatment.
Abstract: SUMMARY: A medium is described by means of which cells of Bacillus cereus in milk may be estimated without the prior use of a heat treatment. Into a nutrient agar are incorporated: egg yolk, to demonstrate production of the characteristic opacity; citrate, to render the inoculated medium more transparent; lithium chloride and polymyxin, to reduce the growth of other bacteria. A cover of water agar limits the development of certain spreading organisms. The medium has proved of value in a survey of samples of raw milk, providing information additional to that obtained by plating after a heat treatment.
24 citations
18 citations
TL;DR: Forty-seven cultures of yeasts, isolated from 47 packs of spoiled acetic acid preserves including 11 varieties and originating from nineteen manufacturers, have been identified according to the system of Lodder & Kreger-van Rij.
Abstract: SUMMARY: Forty-seven cultures of yeasts, isolated from 47 packs of spoiled acetic acid preserves including 11 varieties and originating from nineteen manufacturers, have been identified according to the system of Lodder & Kreger-van Rij. Forty-three cultures had the characteristics of Saccharomyces acidifaciens and four those of Pichia membranaefaciens.
17 citations
TL;DR: The behaviour of other organisms was studied and a reduced sensitivity gave a diminished loss which persisted through many subsequent subculturings.
Abstract: SUMMARY: Following the accidental discovery and subsequent confirmation of an 80% loss of viability in a suspension of Escherichia coli when the ionic environment was changed from phosphate buffer to Ringer's solution, and of similar losses after changes in the reverse direction, the behaviour of other organisms was studied. Clostridium butyricum, Streptococcus lactis, Escherichia coli, and Micrococcus candidus gave positive results, Mycobacterium smegrmatis and a brewer's yeast did not. The survey included variations in the conditions, mostly with E. coli. Minor constituents of the solutions or alteration of their pH modified the effect, e.g. that of 1% NaCl in place of Ringer's solution or of pH 8·0 instead of the usual pH 7·2, was quite different. Also, the addition of glucose, sodium thioglycollate, or methylene blue diminished it, with one exception in the case of glucose. Mic. candidus responded if the solutions were chilled, but not at room temperature. With electrolyte concentrations below about 0·02 M there was no effect. Various other changes of anions were effective, as also was change from a univalent to a bivalent cation. A second treatment, following the necessary intermediate reverse change which had no effect, caused another smaller mortality. This reduced sensitivity gave a diminished loss which persisted through many subsequent subculturings.
TL;DR: The maximum possible oxygen solution rates in bacterial cultures with different aeration conditions were appreciably less than those in a sodium sulphite solution containing a copper catalyst under the sameaeration conditions.
Abstract: SUMMARY: The maximum possible oxygen solution rates in bacterial cultures with different aeration conditions were appreciably less (0·5°0·7 times) than those in a sodium sulphite solution containing a copper catalyst under the same aeration conditions. Knowledge of the relationship between the maximum oxygen solution rates in a culture and the sulphite solution enables one to predict from the sulphite measurements the aeration conditions required to satisfy the oxygen demand of a culture.
TL;DR: In this article, the authors reviewed methods of continuous infrared absorption analysis and gave the description and performance of a commercial infrared CO2 analyser and demonstrated the use of an infrared analyser recorder to measure CO2 in effluent air from deep cultures.
Abstract: SUMMARY: The report reviews methods of continuous infrared absorption analysis and gives the description and performance of a commercial infrared CO2 analyser. Examples are given of the use of an infrared analyser recorder to measure CO2 in effluent air from deep cultures. This measure of metabolic activity can be used to estimate growth rate. It is particularly useful because results are obtained with little or no measurement lag and without the need to sample the culture fluid itself.
TL;DR: Inhibition of foaming in a continuous culture of bacteria has been studied and a preferred method the antifoam was added at regular intervals which were sufficiently short to inhibit foaming completely throughout the intervening periods.
Abstract: SUMMARY: Inhibition of foaming in a continuous culture of bacteria has been studied. At first, foaming was inhibited by the addition of antifoam to the culture only when a foam layer was present. When the antifoam was added in this way foaming often became intense and antifoam additions had to be more and more frequent. In a preferred method the antifoam was added at regular intervals which were sufficiently short to inhibit foaming completely throughout the intervening periods. This method required less antifoam than the other. The effects of foaming in cultures, its causes, and allied problems are discussed.
TL;DR: Bacteria counts were similar under all conditions, though membrane filters on nutrient agar tended to give slightly low counts, and Phenol treated bacteria gave much lower counts when membrane filters were used.
Abstract: SUMMARY: Counts of Escherichia coli were done on nutrient agar (control), on membrane filters on nutrient agar and on membrane filters on filter paper pads. With untreated bacteria counts were similar under all conditions, though membrane filters on nutrient agar tended to give slightly low counts. Phenol treated bacteria gave much lower counts when membrane filters were used: the mean counts for 3 strains of the test organism with filters on nutrient agar varied from 35–65% of the control, while counts with filters on filter paper pads were somewhat lower, varying from 30–47% of the control. The low counts on membrane filters on filter paper pads were not due to adsorption of phenol by the filters or to a low concentration of nutrients in the growth medium.
TL;DR: In this article, the rates of growth of bacteria on Hevea latex systems in the presence and absence of ammonia have been derived from colony count data obtained on a modified Kligler's iron agar medium.
Abstract: SUMMARY: The rates of growth of bacteria on Hevea latex systems in the presence and absence of ammonia have been derived from colony count data obtained on a modified Kligler's iron agar medium. For fresh latex, ammoniated field latex, and ammoniated latex concentrate, variations in the bacterial populations encountered are given for a period of about one year's testing, with some data on commercial samples of latex concentrate. Field latex at routine collection contained about 8 × 106 bacteria/ml. This could be reduced by 62% by the use of sterile tapping cups. In the routine latex, the mixed population grew logarithmically after a lag phase of 2·1/2–3 hr. In clean latex the lag phase was extended to 4 hr. On ammoniation to 0.3% (w/w), the population was reduced over about 2 hr, but subsequently logarithmic growth recurred, without a lag phase. On concentration and further ammoniation to 0·7% (w/w), the count dropped still further, levels of 10/ml or less being achieved in clean conditions, but very slow logarithmic growth again occurred with a lag phase preceding it.
TL;DR: A spore ‘spectrum’ is described of aerobic mesophiles capable of resisting different heat treatments and it is shown that B. licheniformis is the most common spore former found in bulk milk but since its spores are rapidly destroyed at 100°, the more heat resistant B. subtilis isThe dominant surviving sporeFormer in commercial sterilized milk.
Abstract: SUMMARY: A spore ‘spectrum’ is described of aerobic mesophiles capable of resisting different heat treatments. It is shown that B. licheniformis is the most common spore former found in bulk milk but since its spores are rapidly destroyed at 100°, the more heat resistant B. subtilis is the dominant surviving spore former in commercial sterilized milk. The thermal resistance of strains of B. subtilis and B. licheniformis isolated from different sources has been investigated and the strains of B. subtilis typed according to the behaviour of their spores when heated at 100°. All strains of B. licheniformis were destroyed more rapidly by boiling for 2 min than strains of B. subtilis but only those strains of the latter which showed some degree of heat activation were more resistant than B. licheniformis. The ‘resistant’ and heat activated strains of B. subtilis appear to be sparsely distributed in nature and were only isolated from sterilized milk where the heat treatment applied would tend to eliminate other strains. The spore content of bovine faeces was similar to that in bulk milk and the total spore content varied seasonally, the spore content of faeces being on the average a hundred times greater during indoor feeding than during the period when the cattle were fed outside. A faecal infection of the milk in the ratio of 1:104 would infect the milk with spores at about the same concentration as they are found in bulk raw milk, and it is suggested that bovine faeces could be a primary source of spore formers in milk supplies.
TL;DR: The distribution of species and types isolated from milk did not differ materially from that for dairy equipment, Klebsiella cloacae, K. aerogenes and Citrobacter freundii being the dominant species, while the incidence of Escherichia coli was relatively low.
Abstract: SUMMARY: A series of 1,040 cultures of coli-aerogenes bacteria isolated at 30° from farm dairy equipment and raw milk was classified according to the recommendations of the Coliform Sub-Committee of the Society for Applied Bacteriology (Report, 1949). The distribution of species and types isolated from milk did not differ materially from that for dairy equipment, Klebsiella cloacae, K. aerogenes and Citrobacter freundii being the dominant species, while the incidence of Escherichia coli was relatively low. There was no marked seasonal incidence of any type, though E. coli I formed a slightly higher proportion of the coli-aerogenes microflora in winter, whereas K. aerogenes I was slightly higher in summer. Many of the cultures of the dominant types, K. cloacae, K. aerogenes I and Cit. freundii I, did not form acid and gas from lactose in two days at 37°. Consequently 37° negative, anaerogenic and paracolon strains constituted a relatively high proporton (49%) of the coli-aerogenes microflora.
TL;DR: In this paper, the degree of vacuum and time of application needed to dry steam sterilized dressings has been investigated and it was shown that if the steam supply is dry, and the pressure in the drying stage is reduced to an absolute pressure of 50 mm Hg, dressings will be cool and dry without holding the vacuum, provided they are not damp before sterilization.
Abstract: SUMMARY: The degree of vacuum and time of application needed to dry steam sterilized dressings has been investigated. If the steam supply is dry, and the pressure in the drying stage is reduced to an absolute pressure of 50 mm Hg, dressings will be cool and dry without holding the vacuum, provided they are not damp before sterilization.
TL;DR: Suspensions of Escherichia coli I, consisting of washed cells suspended in a phosphate buffer solution, maintained a higher viability and resistance to phenol than suspensions either of unwashed cells or of washed Cells suspended in water.
Abstract: SUMMARY: Suspensions of Escherichia coli I, consisting of washed cells suspended in a phosphate buffer solution, maintained a higher viability and resistance to phenol than suspensions either of unwashed cells or of washed cells suspended in water. When stored for 5 weeks at room temperature, variations in their extinction times on exposure to aqueous phenol solutions were not significantly greater than variations with suspensions freshly prepared for each determination. Loss of resistance of a stored suspension to phenol, roxenol, lysol and potassium laurate was roughly parallel. Conditions of culture of the bacteria influenced the survival of suspensions, but the results indicated that pronounced differences may only be found in suspensions prepared from young cultures. The use of stored suspensions in the routine evaluation of bactericides is recommended.
TL;DR: Past and present work on the spoilage of ciders by lactic acid bacteria is discussed, special reference being made to their activity against malic acid as well as chlorogenic acid and its derivatives.
Abstract: SUMMARY: The spoilage of wines and ciders by lactic acid bacteria is described. The pioneering work on wine bacteriology at the turn of the century is discussed in addition to modern work carried out in Australia and the U.S.A. Similarly, past and present work on the spoilage of ciders by lactic acid bacteria is discussed, special reference being made to their activity against malic acid as well as chlorogenic acid and its derivatives.
TL;DR: The modification of the 44° test proposed by Mackenzie, Taylor & Gilbert (1948) is useful for the rapid identification of Escherichia coli I in water and foods.
Abstract: SUMMARY: The modification of the 44° test proposed by Mackenzie, Taylor & Gilbert (1948) is useful for the rapid identification of Escherichia coli I in water and foods. False positive tests caused by other coli-aerogenes bacteria, or by their association with other organisms, can be considered rare. Only a few E. coli I fail to produce indole or ferment lactose at 44°, and further confirmation for routine purposes is necessary only when the results at 44° are discordant, e.g. indole positive-lactose negative or indole negative-lactose positive.
TL;DR: In this article, when sweet pea seeds were soaked in mercuric chloride solution, a considerable quantity of mercury was taken up and was not removable by a washing procedure even more thorough than that usually employed in the technique for the surface sterilization of plant tissues.
Abstract: SUMMARY: When sweet pea seeds were soaked in mercuric chloride solution a considerable quantity of mercury was taken up and was not removable by a washing procedure even more thorough than that usually employed in the technique for the surface sterilization of plant tissues. To remove the bulk of it, soaking the seed for 48 hr was needed.
TL;DR: An organism which has been frequently isolated from the rhizosphere of plants of Lolium perenne (Perennial Rye-grass) is described; it has the typical morphology and flagellation of Pseudomonas but the biochemical reactions of Klebsiella.
Abstract: SUMMARY: An organism which has been frequently isolated from the rhizosphere of plants of Lolium perenne (Perennial Rye-grass) is described; it has the typical morphology and flagellation of Pseudomonas but the biochemical reactions of Klebsiella
TL;DR: In this article, a stainless steel fermentation vessel of the Waldhof type was used for the cultivation of moulds for the purpose of obtaining fat in a defined media containing inorganic salts and glucose with vigorous agitation and aeration.
Abstract: SUMMARY: A description is given of a stainless steel fermentation vessel of Waldhof type which was used for the cultivation of moulds for the purpose of obtaining fat. In this vessel Aspergillus nidulans, Penicillium javanicum and Pencillium spinulosum were grown in defined media containing inorganic salts and glucose, with vigorous agitation and aeration. In a medium containing glucose (90 g/1.) A. nidulans produced 4·4 g of fat/1, and the fat coefficient (g of fat formed/100 g of sugar utilized) was 8·9; while P. javanicum in this medium produced 3·6 g of fat/1. and the fat coefficient was 7·6. In a different medium containing glucose (100 g/1.) P. spinulosum produced 11·4 g of fat/1. and the fat coefficient was 12·0.
TL;DR: Dehydrogenase activities have been determined of washed suspensions of Escherichia coli prepared from cultures grown in a synthetic medium, and in the same medium supplemented with yeast extract, under conditions of controlled aeration.
Abstract: SUMMARY: Dehydrogenase activities have been determined of washed suspensions of Escherichia coli prepared from cultures grown in a synthetic medium, and in the same medium supplemented with yeast extract, under conditions of controlled aeration. This supplementation resulted in increased activity of enzymes attacking L(+)-alanine, DL-serine, formate and succinate, no apparent change in activity of enzymes attacking L(+)-gmlumate and D(—)-ribose, and decreased action on D(+)-glucose, mannitol and lactate. The results are discussed in the light of present knowledge of the metabolism of E. coli.
TL;DR: In this paper, a study has been made of the immersion cleaning technique as applied on commercial farms, and the results showed that the poor results were caused partly by sporing bacteria which survived the caustic soda treatment, presumably in the spore state, and partly by non-sporing organisms, chiefly chromobacteria and micrococci.
Abstract: SUMMARY: A study has been made of the immersion cleaning technique as applied on commercial farms. In an initial survey bacteriological results for rinses and swabs of the milking equipment were satisfactory on most farms, but on one farm the results were very disappointing. Further investigations at this farm showed that the poor results were caused partly by sporing bacteria which survived the caustic soda treatment, presumably in the spore state, and partly by non-sporing organisms, chiefly chromobacteria and micrococci.
These non-sporing organisms are found in abundance on the surface of dirty wash troughs, and under certain conditions re-contamination of the milking equipment can occur during the rinsing operation. Suggested modifications to the original immersion cleaning technique include the use of hot water for the before-milking hypochlorite rinse, brushing the equipment in the after-milking rinse to remove extraneous dirt, regular cleansing of the wash trough and the monthly cleansing of the basket and bin.
TL;DR: On a microscope slide arranged to simulate a percolating sewage filter the sequence of invading organisms was examined and a primary and secondary invader recognised and these organisms form a substratum suitable for fungal growth.
Abstract: SUMMARY: On a microscope slide arranged to simulate a percolating sewage filter the sequence of invading organisms was examined and a primary and secondary invader recognised. These organisms form a substratum suitable for fungal growth.
TL;DR: The temperature of treatment had little effect on this, though in experiments with added organic matter or lower concentrations of QAC the temperature was important.
Abstract: SUMMARY: A suspension of bacteria was evenly spread on descaled stainless steel strips and air dried. The strips were put into the QAC solution and after the required period the bactericidal action was stopped by adding a neutralizing agent. The strips were covered with nutrient agar and incubated at 37° for 24 hr to enable the surviving organisms to grow into colonies. On removing the thin layers of agar from the strips the colonies were left adhering to the metal. They were stained with carbol fuchsin and counted using a dissecting microscope.
Using the recommended strength of a QAC-detergent solution (200 p/m QAC) and an exposure time of 2 min a mortality of at least 99·58% was obtained. The temperature of treatment had little effect on this, though in experiments with added organic matter or lower concentrations of QAC the temperature was important.