- Volume 28, Issue 1, 1962

SUMMARY: Aberrant forms in a streptomycin-sensitive strain of Mycobacterium phlei could regularly be shown to arise in the presence of low concentrations of streptomycin. The effect of streptomycin on the morphology of M. phlei is comparable with that of penicillin on the morphology of organisms belonging to the Enterobacteriaceae. The transfer of aberrant forms of M. phlei to a streptomycin-free medium resulted in the atypical multiplication of these forms.

SUMMARY: Bacillus cereus organisms growing exponentially have a stable length distribution. This length distribution can be analysed by the method described to give the mean rate of increase in length of organisms at any given length. The validity of the method was confirmed by observing the growth of clones of B. cereus in the culture chamber. Both methods showed that the rate of increase in length increased as the organisms got longer, and that there was no hesitation before or after division. Possible applications of this general method to other parameters that can be measured in samples of bacteria taken from stable populations are suggested.

SUMMARY: A comparison has been made between the chemical composition of the cell walls of strains from the genera Corynebacterium, Mycobacterium, Nocardia, Actinomyces and Arthrobacter, and the antigenic composition of the same cell-wall fractions as judged by an agglutination test. A common antigenic component was identified in all those strains of corynebacteria, mycobacteria and nocardias which have arabinose and galactose as their principal cell-wall sugars. Some strains of corynebacteria, and 3 strains of Nocardia pelletieri which have a different pattern of cell-wall components, appear to lack this cell-wall antigen. The antigen was not present in the cell walls of 8 strains of actinomyces and 6 of arthrobacter. Seven of the 8 strains of actinomyces had a cell-wall composition identical with that previously described for Actinomyces israelii, and these 7 strains formed a homogeneous group serologically: the other actinomyces strain differed in cell-wall wall composition and its cell walls did not agglutinate with the ‘israelii’ serum, nor did those of any of the 6 strains of arthrobacter, although some of the latter resemble A. israelii in cell-wall structure. These results show that the antigenic studies tended to confirm relationships suggested by cell-wall composition alone, especially among corynebacteria, nocardias and mycobacteria: they also suggest that Corynebacterium as at present constituted is a mixture of species of diverse origin.

SUMMARY: The method of application of negative staining with potassium phosphotungstate for the electron microscopy of bacterial surface structure is described. The method has been used to study the fimbriae of Klebsiella strains, and has confirmed, qualitatively, the results of other workers who used the shadow-casting technique. The diameters of the two types of fimbriae associated with the MS and MR adhesins were found to be 65-70 Å and about 48 Å, respectively. These figures are about 30 % less than earlier estimates. The resistance of both types of fimbriae to prolonged autolysis was shown. Other applications of the negative staining method include the study of bacterial flagellation, and of the structure of cells disintegrated by autolysis or other methods.

SUMMARY: Radioactive phenyl mercuric chloride (labelled with 203Hg) was used to measure-SH groups in the mycelium and in the medium. Tritiated phenyl mercuric chloride was used as a quantitative cytological reagent. The changes in -SH concentration of the fungus were not always directly related to the changes in total S in Aspergillus niger, Penicillium chrysogenum 49.133, Eremothecium ashbyii and Candida albicans. A peak in -SH concentration occurred in the cells of these organisms during the early growth phase. Extracellular -SH compounds were produced by all these organisms at some time during development. Cytological studies showed differences in the distribution of -SH compounds in the cell wall and cytoplasm. E. ashbyii and C. albicans had a strong -SH reaction in the cell wall, A. niger and P. chrysogenum 49.133 a weak one. Sulphydryl compounds were most concentrated in areas of hyphal bud formation in E. ashbyii but were not concentrated at the hyphal tip.

SUMMARY: The infrared spectra of 22 strains of the genus Acetobacter were significantly different from those of 9 strains of the genus Acetomonas, with one exception. Within each genus, however, the spectra formed smooth graduated series which showed no sudden differences which could be correlated with species boundaries, and exhibited no features which could be traced to the presence or absence of particular biochemical properties. These results support the division of the acetic acid bacteria into two genera Acetobacter and Acetomonas and render unlikely the existence of distinct species within the genera.

SUMMARY: An investigation has been made of the sequence of morphological events involved in the processes of microcyst formation and germination in the fruiting myxobacterium Myxococcus xanthus. By using time-lapse photo-micrographs and phase-contrast microscopy of living cells, microcyst formation is shown to involve a shortening and thickening of the entire vegetative cell with a subsequent increase of refractility. Germination is preceded by the casting off of a sheath followed by the gradual elongation and loss of refractility of the cell. Vegetative rods will readily form spheroplasts when exposed to a variety of conditions including sulphydryl compounds. The necessity for distinguishing between spheroplasts and microcysts is pointed out.

SUMMARY: Mutants of phage W with diverse virulence were used to lysogenize naturally occurring strains of Bacillus anthracis and their non-capsulogenic derivates. The temperate mutant β readily established itself as a prophage in both sporogenous and non-sporogenous strains of B. anthracis. Strains carrying β-prophage were stable, capable of giving rise to colonies, and their multiplication was not impaired in the mouse. Thus, the virulence of capsulogenic strains, lysogenic for phage β, was not diminished. A less temperate mutant of phage W, phage α, was not capable of lysogenizing an atypical asporogenous strain of B. anthracis, but formed more or less stable complexes with sporogenous strains. The stability of spores carrying phage genome α covered a wide range. Most of such spores did not give rise to colonies after germination but instead formed plaques. In some spores, however, phage α established itself as prophage so that stable lysogenic bacteria could be obtained under certain conditions. Spores of both capsulogenic and non-capsulogenic strains of B. anthracis lysogenic for phage α formed the same number of either plaques or colonies when plated on a sensitive indicator strain or spread on agar surface. When, however, the spores were spread on agar containing 0.025 M-sodium bicarbonate and the plates incubated at a high partial pressure of CO2, then phage development in the lysogenic spores was induced. Hence, under these conditions, the lysogenic spores did not give rise to colonies but lysed and liberated phage. A small proportion of capsulogenic spores carrying prophage α threw off non-lysogenic segregants which gave rise to mucoid colonies in CO2. These mucoid colonies consisted of encapsulated bacteria which probably remained non-lysogenic because their capsules prevented re-infection during their growth. Capsulogenic strains carrying prophage α were markedly less virulent in the mouse and this may be explained by induction of α-prophage by high CO2 tension in the animal body.

This competition between prophage induction and capsule formation, both of which were induced by high CO2 tension, explains the apparent diminution of the virulence of strains of B. anthracis lysogenic for α-phage.

SUMMARY: The general characters are given of a group of phages related to phage β, a temperate phage carried by Bacillus cereus strain W (McCloy, 1951, 1953, 1958). One phage, β´, has been isolated only once but may be a mutant of phage β since it, and its clear plaque variant, γ´, have many properties in common with the other phages.

SUMMARY: Techniques are described for counting and differentiating the rumen microbial population. The rumen liquor is fixed and preserved in formol saline, and counts are made in two counting chambers, whose dimensions depend on the size of the organism to be counted; stained smears of the bacteria are also examined. Counts made on small samples of rumen liquor obtained through a fistula have been compared with counts on samples of the entire rumen contents; the ratio of these counts seemed to depend on the particular organism counted, the ration and the time after feeding. The importance of differential as opposed to total counts is emphasized.

SUMMARY: In sheep fed once daily, the concentrations of micro-organisms in the rumen changed with the time after feeding, some organisms fluctuating in numbers more than others; peak concentrations were reached at different times for different organisms. These changes in concentration were reflected in changes in the proportion of dividing cells, for example, in Dasytricha ruminantium this proportion varied from less than 0.2% throughout most of the day to a maximum of 23 % a few hours before feeding; for Entodinium spp. the variation was less: it was possible to calculate the minimum doubling time for these latter organisms as about 5 hr.

One animal at different times, or different animals, on the same ration and dietary regime had very different rumen microbial populations, these differences being particularly marked in the case of some organisms. Reasons why these marked differences in microbial population are not reflected in similarly marked differences in over-all rumen metabolism are discussed.

Feeding different quantities of the same ration had little effect on the concentration of rumen microbes, provided the ration was above a minimal level; it is, however, suggested that output of microbial cells from the rumen may have varied with the amount of feed given. Starvation for a few days or prolonged under-nutrition had a marked effect, some organisms being drastically reduced in numbers or dying out completely. When the qualitative nature of the diet was changed, about 10 days were needed to complete the major adjustments in the rumen microbial population.

SUMMARY: An examination was made of the ability of amino acids, purines and related compounds, and fatty acids to stimulate growth of Saccharomyces cerevisiae in biotin-deficient medium and to restore the synthesis of nucleic acids and protein. Adenine, adenosine, aspartic acid and Casamino acids (Difco) each stimulated growth to some extent and brought about a partial restoration of nucleic acid and protein synthesis. Oleic acid also stimulated growth, but the effect was much slower than that brought about by the other biotin-sparing compounds tested and it was not accompanied by a restoration of nucleic acid and protein synthesis. Stimulation of growth in biotin-deficient media supplemented with aspartic acid + oleic acid was greater than the stimulation brought about by these compounds singly. During growth of the yeast in biotin-deficient media supplemented with this or certain other mixtures of biotin-sparing compounds there was a well defined exponential phase of growth which was not apparent during growth of the yeast in unsupplemented biotin-deficient medium. But the final cell crop in these supplemented media was still only about half of that obtained in biotin-optimal medium. These results are discussed in relation to the role of biotin in the synthesis of various yeast cell constituents.

SUMMARY: It is shown that the flavin inhibitors mepacrine and lumichrome have a greater effect on the growth of illuminated than unilluminated static liquid cultures of Phycomyces. The possible relevance of these findings to our understanding of the mechanism of phototropism is discussed.

SUMMARY: Colicine factors I and E1 enable Salmonella enteriditis, like S. typhimurium, to pair at high frequency (e.g. with 50-90 % of recipient cells) either with its own derivatives or with those of other species such as S. typhi and S. typhimurium. However, genetic recombinants occur at only low frequency in intraspecific crosses (about 10−7 of recipient cells); whereas in interspecific crosses with S. enteriditis as donor, recombination with S. typhimurium involving either closely linked or single markers occurred at an even lower frequency (about 10−9 of recipient cells). No detectable recombinants were isolated when using either S. enteriditis or S. typhimurium as donor and S. typhi as recipient, although colicine factors were transferred at high frequency.

SUMMARY: The L-phase variants of group D streptococci, analysed in this study, were not only characterized by the absence of the cell-wall polysaccharide antigen, but also by the absence of the group D antigen, which is not a constituent of the cell wall.

SUMMARY: ‘Indifferent’ strains of streptococci-i.e. strains which give no haemolysis or greening on blood-agar plates-frequently occur in cultures from dental root-canals. A serological study of over 200 strains of these streptococci showed that about half of them belonged to Lancefield groups F, G or C. It was shown by cross-absorption that the group-antigen of indifferent streptococci of group F is identical with the group-antigen of haemolytic strains of group F. Apart from the group-antigen, five independent carbohydrate type-antigens, localized in the cell wall, were demonstrated in group F strains. These type-antigens were found in groups other than F, e.g. the type-antigen I was observed in haemolytic and indifferent strains of group G; the type-antigen III occurred in indifferent strains of group C. Several strains with a type-antigen but without group-antigens were observed. The presence of carbohydrate type-antigens in formamide extracts can cause confusing cross-reactions in the grouping procedure, unless strains without type-antigen are used for the preparation of sera.