- Volume 57, Issue 3, 1969

Disrupted cells of some Desulfovibrio species, of Desulfotomaculum ruminis and of certain other anaerobes produced methane as a minor product of pyruvic phosphoroclasm. In one Desulfovibrio species the reaction, which was not specially sensitive to air, involved vitamin B12, co-enzyme A, thiamine pyrophosphate, magnesium ions and acetyl phosphate. Adenine and other nucleotides stimulated the reaction; a mixture of ATP and AMP was most effective. Methionine stimulated the reaction but the other methyl donors did not. In optimal conditions methane accounted for 0·1 to 0·02 mole % of the pyruvate metabolized, formed at 20 to 30 nl. CH4/mg. bacterial protein/hr. Tests in D2O indicated that the methane came from the methyl-carbon of pyruvate; correspondingly, ethane formation from β-ketobutyrate was detected.

Washed suspensions of Entodinium caudatum grown in vitro and incubated anaerobically incorporated 14C from [14C]glucose into the cell pool as [14C]glucose, maltose and hexose phosphate and into protozoal polysaccharide and intracellular bacteria as a glucose polymer. The uptake of sugars into the pool was by an active process (predominant at low sugar concentrations) probably into the protozoal endoplasm, and by a passive process (predominant at high concentrations) into another part of the cell. Uptake of glucose by the active process was not sufficiently rapid to increase the level of glucose in the pool by more than 17% per hour; this was probably insufficient to increase appreciably the rate of glucose utilization. These protozoa hydrolysed starch to maltose and glucose and the level of these sugars in the pool of protozoa metabolizing starch grains was controlled in part by the inhibitory effect of these sugars on the enzymes that formed them. Studies on the enzymes involved in the metabolism of starch showed that the glucose in starch was hydrolysed to free glucose before phosphorylation. In experiments on the effect of carbohydrates on the survival of protozoa, starch was the most effective in prolonging protozoal life, followed by maltose and glucose in that order. The greater effectiveness of maltose was correlated with the finding that the rate of uptake of maltose carbon was always greater than that for glucose when the two sugars were present in equimolar concentrations. However, the rate for both sugars was markedly decreased in the presence of penicillin and neomycin. Evidence is presented that the protozoal ectoplasm may be freely permeable to sugars in the medium and that there is a barrier between the ectoplasm and endoplasm. 14C from [14C]starch grains was incorporated by the protozoa but there was no synthesis of protozoal protein from carbohydrate.

Similarity values based on 199 features of 88 strains of bacteria, including freshly-isolated strains of streptococci and named strains of the genera Streptococcus, Listeria, Microbacterium, Erysipelothrix, Brevibacterium and Arthrobacter, were analysed by single and complete linkage sorting programmes. It is concluded that Erysipelothrix, Listeria and strains currently known as Microbacterium thermosphactum show closer relations to the family Lactobacillaceae than to the other representatives of the family Coryne-bacteriaceae here examined.

A group of 62 strains, mostly members of the genera Micrococcus and Sarcina, has been subjected to a numerical–taxonomic analysis. All 57 characters have been scored according to the scale 0 to 5 and an appropriate formula has been used for the calculation of similarity. The method of clustering of organisms applied here is a modification of the original ‘single-linkage method’. Eleven 85-phenons were found and the rank of species has been attributed to them. On the basis of existing taxonomic studies it appears probable that aerobic sarcinas must be considered as members of the genus Micrococcus and that they are R-dissociated forms of proteolytic micrococci.

A strain of Azotobacter chroococcum (designated A. chroococcum nts) which produces fragile cysts was isolated from soil. Fragility of the cysts was measured by ultrasonic treatment and compared to the fragility of cysts of a typical strain of A. chroococcum. Differences in fragility and resistance to ultraviolet radiation were observed but differences in desiccation resistance were not perceptible between the two strains. Electron micrographs of cysts of the new isolate revealed a structural aberration in the exine area of the cyst coat which may be associated with the physiological differences described. The morphological aberration and the fragility of the cysts are inheritable traits of this strain of A. chroococcum.

Several mutants isolated from three Klebsiella aerogenes strains showed characteristics differentiating them from the wild type and also from the normal type of non-mucoid mutants. These mutants synthesize much less polysaccharide slime or capsule than the parent bacteria at low incubation temperature, but similar amounts at 37°. The colonies are of rough appearance at 20° and liquid cultures at this temperature autoagglutinate. At 37°, mutant and parental types are indistinguishable. The mutants show altered phage sensitivity patterns at 20° and the yield of lipopolysaccharide appears to be decreased at lower temperatures. Double mutants retaining certain of these characteristics but devoid of exopolysaccharide-synthesizing activity have also been isolated. The properties of the parent and mutant types are compared.

The aflatoxins of Aspergillus flavus are very toxic for mycophagous mites Glyciphagus and less toxic for Histiostoma. Some Penicillium species producing mycotoxins were not favourable for the multiplication of Glyciphagus, but other moulds such as Penicillium roqueforti were suitable.

Ribose mononucleotides accelerated morphogenesis in Dictyostelium discoideum at 10‒4 M and above; equimolar purines, pyrimidines, ribose, phosphate, ribose-5-phosphate and nucleosides either slowed morphogenesis or had no effect; 5′-GMP, 5′-UMP and 5′-CMP were about as effective as AMP. The position of attachment of the phosphate to the ribose moiety was not critical; 3′,5′-cyclic mononucleotides influenced chemotaxis and accelerated morphogenesis.

It is proposed that a second family be re-established within the Mycoplasmatales for those strains not requiring sterol. Following the nomenclature of Sabin, who first made this proposal, the sewage strains of Laidlaw and Elford are renamed Sapromyces laidlawii and assigned to a family Sapromycetaceae. The status of strains not requiring sterol is discussed, including that of sewage a and b. In the light of recent evidence the pig isolates, originally named Mycoplasma granularum, seem to belong to the genus Sapromyces. Recently described tissue-culture isolates, as yet unnamed, represent another species within the Sapromycetaceae. It is questionable whether the organisms classified as M. laidlawii var. inocuum deserve the status of a named variety of S. laidlawii.

Data from previous numerical analyses have been combined to produce an over-all classification of the genus Thiobacillus; 93 strains were examined using 38 tests and 106 character states. The results indicated the possible existence of a new species and demonstrated an unexpectedly close similarity between T. neapolitanus and T. thio-oxidans.

A number of diagnostic tests have been selected from those used for the numerical analysis. A brief description of the other important features of each species recognized is also given.

A new medium (FTO), selective for Gram-positive bacilli from human skin, was developed, consisting of trypticase-soy, yeast-extract agar supplemented with (i) Tween 80 (0·5%) to support growth of lipophilic corynebacteria. (ii) Oil Red O (0·0005%) to distinguishlipophilic from non-lipophilic bacteria, and (iii) Furoxone (50 to 100 μg./ml.) to inhibit growth of Gram-negative bacilli and Gram-positive cocci. Furoxone may be used to render other media selective for more fastidious diphtheroids.

The half-maximal growth rate of a streptomycin-dependent mutant of Escherichia coli b on limiting concentrations of dihydrostreptomycin varied with the nature (but not with the initial concentration) of the carbon source. It was highest with gluconate, lower with glucose and glycerol and lowest with lactate. Glucose-sensitive enzymes (acetohydroxy acid synthetase, fumarase, aconitase, citrate synthase and isocitric dehydrogenase) were specifically repressed by antibiotic limitation. Parallelism was observed between decreasing dihydrostreptomycin concentration, decreasing growth rate and increasing catabolite repression of certain glucose-sensitive enzymes. The results are not incompatible with the hypothesis that the primary site of action of dihydrostreptomycin in the dependent organism is an anabolic process (e.g. protein synthesis). However, the growth-limiting effect of antibiotic deprival appears to be augmented by catabolite repression.