- Volume 6, Issue 1-2, 1952

Summary: By using a culture of Streptococcus agalactiae in its logarithmic phase of growth as test organism, it is possible to assay nisin satisfactorily with an incubation period of approximately half an hour. Penicillin, streptomycin, aureomycin and gramicidin cause a qualitatively similar response in the test organism. A similar technique could therefore be used to assay these antibiotics.

Summary: Certain races of streptococcal phage with a normal lytic action on some strains of streptococci were found to be adsorbed on, and to inhibit the growth of, other strains, without the occurrence of lysis or multiplication of the phage. One race of phage inhibited the growth of several streptococcal strains which had hitherto been considered unrelated to one another on the basis of their reactions to lytic phages. Cultures which recovered from temporary inhibition by phage contained variants which were resistant both to inhibition and to lysis by phages which attacked the original strain. This resistance is, however, short-lived as compared with the resistance of variants obtained through the action of a lytic phage.

Summary: The difficulties of assaying micrococcin by the usual microbiological methods and means of obviating or decreasing some of them are described. Certain detergents have a solubilizing effect on micrococcin and it is possible to assay such ‘solutions’ by hole-plate or other diffusion methods which cannot otherwise be applied. Low results are obtained by this method in crude fermentation liquors, probably because some of the micrococcin is present in a bound form. Ethanolic solutions of micrococcin have a powerful purple fluorescence in ultraviolet light by which amounts of the order of 2·5 μg./ml. may be accurately estimated. Details are given of the procedure, and of the special precautions necessary when micrococcin in broth or tissue is to be estimated. Micrococcin may also be estimated by measuring the absorption in ethanolic solution at 345 mμ., at which wavelength E 1 cm. 1 % = 177·5.

Summary: A number of media have been developed for the production of micrococcin. A satisfactory medium consists of corn steep liquor to 1800 mg. N/1. with an aqueous extract of dried autolysed yeast to 1800 mg. N/1., which gives titres of the order of 40–60μg. micrococcin/ml. in 3 days. A soluble yeast extract such as Marmite may be used in place of the dried autolysed yeast. Moderate aeration is required for good titres but initial pH is relatively unimportant, any value in the range 6·0–7·0 being suitable. The main energy source in sugar-free media is probably the aerobic oxidative deamination of amino-acids. An inoculum that has been pre-incubated gives better results than an inoculum used immediately after it has been prepared. The addition of various inorganic ions to the medium was tried without any detectable influence on titre.

Summary: The antibacterial activity of a strain of a Cephalosporium sp. was found to be due to a number of antibiotics. One group of these, named Cephalosporins P, is soluble in organic solvents and active only against Gram-positive bacteria.

The P antibiotic(s) is produced in good yield in deep culture in a medium comprising corn steep liquor and glucose at an initial pH of 6·3. A high aeration rate assisted by adequate stirring is essential. Submerged cultures 72 hr old form convenient inocula. Under optimum conditions with 2% (v/v) of such an inoculum the maximum titre is reached after 47–50 hr. at 24°, and thereafter falls.

Summary: The diffusion rate of nisin through agar at pH 7·0 is increased by the addition of a non-ionic surface active agent to the medium. A linear relationship exists between log units nisin/ml. and inhibition zone depth over the range 100–5000 units/ml. By using seeded agar in small glass tubes and delaying growth of the test organism for 24 hr., a convenient form of assay is available for dealing with large numbers of samples.

Summary: The nutrition of three virulent and three avirulent strains of Pasteurella pestis has been studied at temperatures between 23 and 37° on a basal medium containing glucose, ammonium and other inorganic salts. The organism has considerable synthetic powers and the distinction between essential nutrients and non-specific stimulants of growth is not always definite. At 32° and below, the optimal medium contained phenylalanine, valine, isoleucine, cysteine, methionine and haemin. Five out of the six strains utilized leucine in place of valine, but the maximum count was then delayed. At 36° the optimal medium contained in addition, alanine, leucine, serine, threonine, biotin and pantothenate. Omission of alanine or leucine delayed growth without reducing the maximum population. When biotin and pantothenate were omitted the organism required a mixture of twenty amino-acids.

SUMMARY: Extracts of 288 plants, mostly British, were examined for suppressive action on the development of a bacteriophage of Pseudomonas pyocyanea. Many possessed this property and eight of them suppressed the growth of phage at concentrations less than one-tenth of those which affected the growth of the host, Ps. pyocyanea.

Extracts from 142 of the plants were tested against Influenza A virus in embryonated eggs and twelve of them suppressed virus multiplication. All extracts active against Influenza A virus were also active against the bacteriophage. Four extracts tested against Influenza A in mice were inactive. Eight extracts were investigated further; these were inactivated by proteins and were only active when in direct contact with the virus in protein-free media, Activity was closely associated with the tannin content of the extracts and could not be separated from it. Commercial tannins were also highly active in protein-free media.

Summary: When fat and acetate are the principal substrates, the aneurin requirement of the ciliate Tetrahymena geleii is decreased but not entirely eliminated, in a way comparable to the aneurin-sparing effect of fats in metazoa. Aneurin-deficient cultures utilizing glucose or fat as substrates accumulate pyruvic acid.

Summary: Effects of phenol, 2-phenoxyethanol and cetyltrimethylammonium bromide on the oxygen uptake of suspensions of Escherichia coli supplied with various single oxidizable substrates were examined. Phenol and 2-phenoxyethanol at low concentrations caused a stimulation of oxygen uptake in the presence of mannitol, glucose or lactose which was not associated with an increase in viable count, no stimulation with glycerol, and a retarded oxygen uptake with lactate, succinate or pyruvate. At higher concentrations phenol and 2-phenoxyethanol caused a retardation of oxygen uptake with all substrates, the degree varying with the substrate. Cetyltrimethylammonium bromide was toxic at very low concentrations and no stimulation of oxygen uptake by low concentrations or differential response in presence of different substrates was found.

Summary: Different strains of staphylococci vary in ability to produce free coagulase. Methods are given for the selection of suitable strains and for the production and concentration of coagulase from one of them. Of animal plasmas examined, cow, sheep, dog, guinea-pig and mouse showed a relative deficiency in coagulase activator, while plasma of man, monkey, horse, cat, pig, fowl and rabbit contained the most.

Coagulase activator resembles prothrombin closely in physical properties such as thermolability, behaviour during salting out and removal by adsorbents. They are both partly lost in blood clotting and in dicumarol poisoning, but while prothrombin is apparently removed from plasma by repeated Seitz filtration there is no loss of activator. The question of probable identity is discussed.

Antibody to coagulase is present in the sera many normal individuals and in those suffering from chronic staphylococcal infections. The intramuscular injection of coagulase adsorbed on aluminium phosphate produces similar antibodies in the sera of rabbits.

Summary: An investigation has been carried out into the association between ciliate Protozoa and bacteria in a chalk stream. The ciliates are discussed in the present paper. In general, the largest number of ciliate species and individual species were associated with a growth of green or blue-green filamentous algae. A zonation in the distribution of species along the length of the stream was observed, and particular species were found to undergo cyclical variations in the numbers of individuals. Though there was no correlation between total bacterial numbers and total numbers of ciliates present at any time, the highest bacterial numbers occurred when diatom-eating ciliates were dominant. Statistical analysis showed that the presence of Gram-negative rods in the bacterial flora was correlated with the presence of bacteria-eating ciliates. Gram-positive rods, on the other hand, were correlated with the presence of diatom-eating ciliates. The bacterial flora of the stream was in part determined from that of the surrounding soil. The periods of abundance of ciliates seemed to be related to weather conditions, since ciliates were found to increase in numbers after heavy rain or during prolonged droughts when the banks tended to crumble. Various observations suggest that the ciliate faunas of soil and brook are largely identical. The addition of a small quantity of a broth culture of a micrococcus isolated from the brook to cultures of soil ciliates in soil-extract hay-infusion medium led to a rapid multiplication of ciliates.

Summary: Clostridium propionicum evidently possesses a mechanism for the conversion of lactate to propionate different from that found in the previously studied propionic acid producing bacteria. Reactions common to certain propioni-bacteria and Veillonella gazogenes which could not be demonstrated with Cl. propionicum include: (a) the decarboxylation of succinic acid; (b) the fermentation of malate and fumarate; (c) the variation in the ratio of acetic to propionic acid according to the concentration of CO2; (d) the fixation of CO2 in propionic acid.

Summary: The selenate ion, a remarkably powerful competitive antagonist of the reduction of sulphate by Desulphovibrio desulphuricans (Hildenborough) suspensions, did not affect reduction of sulphite and thiosulphate. Cysteine, methionine and glutathione had no anti-selenate effect. Selenate also inhibited the growth of D. desulphuricans; this effect was antagonized competitively by sulphate and non-competitively by sulphite. Repeated subculture in subinhibitory selenate + sulphate mixtures did not give rise to a selenate-resistant strain, though selenium was deposited in these conditions.

The monofluorophosphate ion behaved similarly: it was a competitive sulphate antagonist in growth and in sulphate reduction, though it had a lower specific anti-sulphate activity than selenate. It did not affect the metabolism of sulphite or thiosulphate. At high concentrations it showed non-competitive inhibition of sulphate reduction.

Of the other ‘analogues’ of sulphate tested, potassium tellurate suspensions and chromate inhibited growth and sulphate reduction, but were not competitive sulphate antagonists. High concentrations of perchlorate depressed sulphate reduction in a non-competitive manner, and methanesulphonate, β-hydroxyethanesulphonate, benzenesulphonate, ethylsulphate, sulphamate and dimethylsulphone were inactive.

An acridinium dye known to inhibit the growth of D. desulphuricans did not affect sulphate reduction, and, in growth, was not antagonized by sulphate or complex nitrogenous supplements. The organism was readily ‘trained’ to resist this dye.

Summary: Changes in the metabolism of the chick embryo host cell produced by p-aminobenzoic acid or sodium cyanide did not influence the multiplication of psittacosis or Newcastle virus. A suspension of psittacosis virus was unable to catalyse oxygen uptake in presence of glutamic acid, casein hydrolysate, succinic or pyruvic acids. The results suggest that, in its relation to certain metabolic activities of the host cell, psittacosis virus more nearly resembles the true viruses than the Rickettsiae.

Summary: Tubes of Kraft paper which can be used repeatedly up to six times are used for encasing individual pipettes.

Summary: By the preparation of specific type sera 24 types of streptococci within group D are designated on the basis of agglutination tests. Subtypes associated with three of these types are indicated by reciprocal absorption. Precipitin tests with absorbed sera substantiate the division of types by agglutination. Of 353 strains of streptococci identified serologically as group D and further specified by physiological characters, 281 were typed by slide agglutination; the remaining 72 did not fall into any of the 24 types. Whilst there is no absolute correlation between serological type and physiological characteristics, a broad division can be made between Streptococcus faecalis and its varieties on the one hand and Strep. durans, Strep. bovis and various unclassified strains on the other.

Summary: The method of most probable numbers (MPN) was employed in order to determine the number of resistant brucella cells at concentrations of streptomycin of 1, 10 and 100 µg./ml. The examination showed agreement with the centrifugation method (plating of the sediment of at least 100 ml. of culture together with the required concentration of streptomycin) in a range up to 1000 resistant cells/100 ml. The method showed that there exist differences in the numbers of resistant cells in different strains, and that in cultures originating from the same colony variations occur. The general trend is a relative increase of the resistant cells with the age of the culture.

Summary: Using staphylococci grown from single-cell isolations made at various stages of selection on penicillin media, it was observed that the 18 hr. progeny show variations in penicillin sensitivity, as tested by increase in resistance. The range of variation is about the same at any stage in selection; variation appears to be continuous in any one population of the microbes, since the number showing increased resistance depends upon the closeness of the steps in penicillin concentration used in testing the resistance.