- Volume 4, Issue 1, 1950

SUMMARY: Two members of the pleuropneumonia group, provisionally called the P and S species, were isolated from the genital tract of cattle.

The P strains required serum for artificial cultivation. Cultures on horse serum media had a characteristic appearance, due to the precipitation of a substance, probably protein; this aided identification. Strains differed antigenically, although common antigens were sometimes shared; antisera were prepared in rabbits against three different serological types. Agglutinins for P strains were not found in sera of infected cattle. There is some evidence that these strains may be capable of causing an inflammation of the genital tract which predisposes to infertility.

The S strains resembled the saprophytic members of the pleuropneumonia group, to which they were serologically related; they grew at room temperature and on media devoid of serum. They were antigenically distinct from P strains. They may be commensals or gain access to discharges as contaminants.

The observations in cattle suggest further study of strains of pleuropneumonia-like organisms isolated from the human genital tract. The assessment of their pathogenicity for man may be complicated by the presence of more than one species in the human genital tract.

SUMMARY: Cysts of two amoebae from soil were grown in single-cell cultures to test the effect upon excystment of the presence or absence of bacteria, age and type of bacteria, age of cyst, and the concentration of sodium chloride. Within the limits of the experiments excystment in one species was independent of the presence of bacteria, and unaffected by their age and type or by the age of cyst. The other species was more sensitive and could not excyst without living bacteria of a suitable type, and the cysts become less likely to develop with age. Excystment in both species was adversely affected by increasing the concentration of sodium chloride, distilled water giving the best results.

SUMMARY: Crude preparations of the lecithinase of Clostridium bifermentans are lethal for mice. Their toxicity, haemolytic activity, and the power of liberating acid- soluble phosphorus from lecithin are neutralized by Cl. welchii α-antitoxin; in terms of lethal doses of Cl. welchii α-toxin and the bifermentans lecithinase, α-antitoxin is less than one five-hundredth as effective against the bifermentans lecithinase as against the α-toxin.

In terms of in vitro lecithinase activity in standard conditions, equipotent amounts of lecithinase from three different strains of Cl. bifermentans were respectively 9, 60 and 75 times less toxic than the corresponding amount of Cl. welchii lecithinase. The toxicity of the Cl. bifermentans lecithinase therefore is determined, not only by its lecithinase activity, but by unknown factors that vary from strain to strain of the bacillus. These factors are not likely to be contaminating substances with a synergic or inhibitory effect, since the differences in toxicity were maintained in several preparations from each of the three strains studied.

The analysis of the two antigenically related lecithinases from Cl. welchii and Cl. bifermentans provided no positive evidence against the hypothesis that the α-toxin of Cl. welchii is identical with the lecithinase.

The cultivation of Vibrio cholerae in media containing sublethal concentrations of penicillin apparently favours the selection of two morphological forms: motile spherical masses containing large numbers of apparently nuclear elements, and fantastically branched forms. On penicillin-free media both forms yield the original comma forms.

SUMMARY: Some chemical requirements for stimulating the germination of spores of a few species of the genus Bacillus were studied by means of viable counts.

Of the three compounds alanine, tyrosine and adenosine, l-alanine was present in all cases where highly significant stimulation was observed; the need for the other two compounds ranged from ability to dispense completely with both of them to a distinct need for the two together to produce a maximum effect.

Generally, the effects were greater with spores grown in a chemically defined amino-acid medium aerated by shaking than with those grown on the surface of a casein-hydrolysate agar.

In the single case examined, that of a laboratory strain of B. subtilis, the effect of l-alanine was strongly inhibited d-alanine at a molar ratio of 1:30.

SUMMARY: Suspensions of Bacillus anthracis, grown under various conditions, and disintegrated by shaking with minute glass particles, were not toxic to mice. The organisms were grown on both simple and complex media, aerobically and anaero-bically, with and without extra carbon dioxide, for periods of from 6 hr. to 10 days.

SUMMARY: The effect of dilution on numbers of local lesions produced by plant viruses was tested graphically and statistically for compatibility with contrasting hypotheses. Experimental results are incompatible with the hypothesis that lesions are produced because of chance encounters between single virus particles and susceptible regions of a uniform type, and that variations in response to similar inoculation between different leaves or plants occur solely because of variations in numbers of such regions. The results are compatible with the hypothesis that individual susceptible regions vary in susceptibility so that different doses of virus are needed to produce a lesion (the variations being such that the logarithms of minimal effective doses are normally distributed). The second hypothesis is, therefore, more probably correct, but the first can be fitted to experimental results by introducing various auxiliary assumptions, such as the existence of qualitatively different virus particles and susceptible regions. Conclusive evidence is unlikely to come from mathematical treatment of existing results, but only from a new experimental approach.

SUMMARY: Nisin, which does not diffuse quickly through agar, may be assayed by dilution methods; or, because it is bactericidal and not merely bacteriostatic, it may be assayed by estimating numbers of surviving bacteria.

Nisin in low sublethal concentration simply prolongs the lag-phase of Streptococcus agalactiae; in higher sublethal concentrations it also induces fast-growing resistant strains. In both cases the delay can be accurately related to nisin concentration, growth being measured in terms of acid production.

SUMMARY: Two types of scar are formed on yeast cells as a result of the division process: a single ‘birth scar’ marking the point at which the cell was joined to the parent, and a variable number of ‘bud scars’ marking the points at which buds have been formed. A regular sequence of bud formations occurs. Cultures grown from the first and last buds appear to be identical.

SUMMARY: Paper chromatography was used for studying qualitatively and quantitatively the reducing sugars liberated from sucrose during the synthesis of polysaccharides by certain bacteria. Glucose and fructose were the only sugars detected, varying in amount with the bacteria and with the type of polysaccharide synthesized. The results suggest that both polymerizing and hydrolytic enzymes were present.

SUMMARY: Twenty-nine strains of streptococci from patients with subacute bacterial endocarditis, three type cultures of Streptococcus sanguis, and eighty strains of streptococci from the blood of persons after dental extraction were tested physiologically and serologically.

Six endocarditis strains fall into Lancefield group H and four into Lancefield group D; the remaining nineteen were serologically heterogenous. Thirteen of the endocarditis strains produced a serologically reactive dextran in sucrose broth. Of these five were group H streptococci; the rest represented several serological types.

Of the three dextran-producing strains of Str. sanguis examined, types I and I/II were placed in Lancefield group H, whereas type II was serologically distinct.

The eighty strains from dental bacteraemias included ten which produced a dextran; five of these were group H streptococci.

SUMMARY: By adjusting the electrolyte content of variously compounded bile-salt media, the growth of coliform bacilli and R forms of intestinal pathogens can be suppressed leaving the S forms of the latter unaffected. Anaerobiosis abolishes the inhibitory effect whereas increased oxygen concentrations enhance it. The degrees of inhibition depend upon the balance of bile salt, electrolyte and oxygen concentration.