- Volume 3, Issue 3, 1949

Summary: The general form of assay for streptomycin described by Brownlee, Delves, Dorman, Green, Grenfell, Johnson & Smith (1948), based on an 8 × 8 quasi-Latin square layout of cavities on a large agar-covered glass plate, in place of Petri dishes, can be adapted to penicillin. A new design, using the principle of double confounding, allows the estimation by the usual four-point assay, of seven (instead of three) unknown solutions per plate of 64 holes. In routine use this assay gives fiducial limits (P = 0·95) of about ± 9·6%, including dilution errors.

The assay procedure previously described in this Journal (Brownlee et al. 1948) for streptomycin, is immediately adaptable to penicillin. For dealing with large numbers of fermenter samples in particular, we have found modifications desirable, which we describe in the present paper.

Summary: Of 46 strains of Haemophilus pertussis, 34 recently isolated strains were all agglutinated by Phase 1 antiserum. Of 12 laboratory strains, 5 had lost their agglutinability. The agglutinable strains were precipitated by aluminium phosphate, and lysed by sodium hydroxide or 10% sodium desoxycholate and were virulent to mice. The virulent strains, which were precipitable by aluminium phosphate, produced toxic substances in a fluid culture. Precipitation by aluminium phosphate provides a quick method for distinguishing virulent and avirulent strains of H. pertussis.

Summary: About three hundred strains of proactinomycetes were isolated from Rothamsted soils and examined together with certain strains from the National Collection of Type Cultures and other sources. Although little more than 9% were partially acid-fast on immediate isolation, subcultivation on rich media such as milk or nutrient glucose broth increased the percentage to 31%. The strains showed a range of features, from the soft mycobacterial type of growth with transient vegetative mycelium and very sparse aerial mycelium, if any, to the harder, more actinomycete-like variety. Of the acid-fast species Proactinomyces opacus, Proactinomyces salmoni-color, and Proactinomyces paraffinae predominated. In all, ninety-two strains were observed continuously for nearly two years on a variety of complex and simple media, and were stained at frequent intervals. Acid-fast cell elements occurred more often in complex protein- and fat-containing media, and in chemically defined media containing paraffin or large quantities of glycerol. They varied in shape and size according to the species and the age and quality of the growth. It is thought that differences of permeability of the cytoplasmic membrane in different environments may account for these variations. No evidence was obtained of any “resting spores? or “chlamydospores? in the vegetative mycelium. Since there are no true spores in the aerial mycelium when it is present, the proactinomycetes in general may be regarded as asporogenous.

SUMMARY: The assimilation of glutamic acid by washed suspensions of Staphylococcus aureus is inhibited by 8-hydroxyquinoline (oxine). Fermentation and respiration are also inhibited but only at higher concentrations of oxine than those required for the complete inhibition of assimilation. The inhibition of assimilation by oxine can be annulled by washing the cells in water or in salts of certain divalent metals; manganese salts are more effective than those of Co, Fe or Mg. The inhibition produced by high concentrations of oxine can be decreased by metals known to form chelate complexes with oxine; the addition of an equivalent of Mn completely abolishes the inhibition.

Glutamate assimilation in Staph. aureus is impaired by a deficiency during growth of either Mn or Mg, but is not abolished unless both metals are absent. Washed suspensions of Mn- and Mg-deficient cells are activated by the addition of either Mn or Mg; Mg is more effective than Mn in activating washed cells whereas Mn is more effective than Mg in activating growing cells.

Assimilation of glutamic acid is activated by either Mn or Mg, Mn being utilized preferentially during growth. In the absence of Mn, the organisms utilize Mg and the sensitivity of assimilation to inhibition by oxine decreases.

SUMMARY: The aerobic sporing Streptomyces may be distinguished from the parasitic anaerobic Actinomyces by the type of branching which they possess. It is proposed that they should be assigned to separate orders, Streptomycetales and Actinomycetales. The latter order is subdivided according to the type and arrangement of the component cells, and consists of two Families. The first, Actinomyceta-ceae, includes anaerobic actinomyces, and also ‘soil diphtheroids’ for which a new genus, Jensenia is proposed. The second, Mycobacteriaceae, includes Mycobacterium, Corynebacferium and Nocardia.

Summary: None of the various methods proposed for the microbiological assay of cystine is entirety satisfactory. Leuconostoc mesenteroides P-60 appeared to be the most suitable micro-organism, but assays were nevertheless variable and, occasionally, completely unreliable. A toxic effect characterized all assays to some extent, but no satisfactory explanation of its occurrence can be advanced.

Summary: Bacteria capable of synthesizing polysaccharides are present in various agricultural, moorland and forest soils, and may form from 5–16% of the viable bacterial population, as estimated by the plate-dilution counting technique. Chemical examination of the polysaccharides synthesized distinguished four types: levans, glucose-uronic acids, glucose-mannose-uronic acids and glucose-mannose-rhamnose-uronic acids. Bacteria synthesizing these polysaccharides are well distributed in the soils studied, those forming the first two types being by far the most common. There is no clear relationship between morphology of the organisms and type of polysaccharide synthesized.

SUMMARY: The production of licheniformin-like antibacterial activity in culture by a single strain of Bacillus licheniformis required neutral or alkaline conditions, conveniently attained by the use of lactate rather than glucose as a source of carbon in a chemically defined medium.

When the medium contained initially about 0·04–0·10 % nitrogen, supplied as asparagine or as ammonium lactate, and the cultures, harvested after 4–9 days at 37°, were sterilized by bringing to pH 2·5 and autoclaving, the inhibitory dilution against a test strain of Mycobacterium phlei was 1/160 or greater.

Fluid from cultures in a chemically defined medium, containing 0·06 m ammonium lactate and 0·05 m sodium lactate, inhibited the test organism at a dilution of 1/200–1200 (geometric mean, 530) in 44 consecutive batches of 100–200 1. culture fluid produced by incubation of cultures in shallow layers. The pH value of the harvested fluid was about 9 and the antibiotic material was partly bound by the cells. It was largely freed by adjustment to pH 2·5.

When amino-acids were added to the medium either as a mixture of known amino-acids, or as a casein hydrolysate. the maximum titre was attained earlier, but with no significant change in its value. A similar result was obtained with yeast extract added alone or with casein hydrolysate.

Summary: Magnesium is essential for the normal cell division of bacilli in complex media. Under conditions of magnesium deficiency or magnesium excess, cell division is inhibited and filamentous cells may be formed. Under the same conditions there is no appreciable interference with the division of chromatinic bodies. The magnesium requirements of the Gram-positive bacteria are considerably greater than those of the Gram-negative bacteria, possibly because the former incorporate magnesium into the structure of the Gram complex.

SUMMARY: In simple chemically defined media all of 15 bacteria failed to grow in the complete absence of magnesium. The concentration of magnesium for maximum growth was dependent upon the Gram reaction of the individual species examined, the magnesium requirements of the Gram-positive organisms being some ten times greater than the requirements of the Gram-negative organisms. In contrast to the observations made in more complex media (peptone water), normal cell division occurred in chemically defined media containing suboptimal amounts of magnesium. It is suggested that magnesium is involved in the synthesis of bacterial protoplasm as well as cell division and, in simple chemically defined media, the synthetic reactions require the higher magnesium concentration.

SUMMARY: Thirty strains of Bacillus polymyxa were isolated from soil, vegetation and water, and nine strains were received from other sources. At the time of isolation the new strains were of a white or sporogenous colony type, but rapidly produced asporogenous and rough variants. Four bacteriophages were isolated from a variant of a soil strain and from soil and sewage. These differed in host-strain specificity, particle size, heat resistance, citrate sensitivity and serological reactions.

SUMMARY: Several Gram-negative bacteria produce pleuropneumonia-like (L-) forms, some under ordinary cultural conditions, others only when exposed to abnormal ones. The formation of these bodies starts with the production of small nuclear elements surrounded with a thin cytoplasmic layer; these elements fuse with neighbouring elements and the L-body is complete. Whereas some L-strains reproduce themselves indefinitely, others revert to the bacterial form. Thus the bacterial and the L-forms are now regarded as two different generations of the same organism and my symbiosis theory is abandoned.