- Volume 27, Issue 1, 1962

SUMMARY: A method of assaying the antibiotic cephalosporin C in low concentration in culture fluids by using a strain of Vibrio cholerae is described. The formation of spheroplasts of the test organism in subinhibitory concentrations of the antibiotic and chemically related compounds is discussed.

SUMMARY: Several bacteria able to decompose native lignin prepared according to Brauns (1939) were isolated from soil; they were aerobic, Gram-negative, motile or non-motile, non-endospore forming rods belonging to the genera Pseudomonas and Flavobacterium. The decomposition was studied in a neutral medium containing the lignin as a suspension of fine particles and solidified with silica gel. 20–30% of the lignin added to the medium was decomposed by the bacteria. Independently of the biological decomposition, a non-biological transformation of lignin occurred during the later stage of the incubation when the medium dried out. The products of the non-biological transformation were dark brown, soluble in water but insoluble in ethanol. They reacted readily with nitrogen compounds in peptone, forming complexes containing about 2·5% nitrogen, half of which was α-amino nitrogen. The relation of these complexes to soil humic acid is discussed.

SUMMARY: Minimum numbers of viable organisms of the yeast species occurring in the digestive tract of 57 pigs were determined in samples from six sites in each animal (stomach, three sites in the small intestine, caecum, rectum). In 27 animals (47·4%) Candidaslooffii was found in one or more sites in numbers ranging from less than 300 to 9,000,000 viable organisms/g. wet sample. The trend was an increase in numbers towards the anus, with highest counts in the rectum and next highest counts in the caecum. The food eaten influenced the numbers of C. slooffii; food rich in starch apparently increased, while food rich in cellulose and proteins decreased, these numbers. The pig appears to constitute a suitable host for the obligate intestinal saprophyte C. slooffii. Other yeast species found at one or more sites in numbers above 100/g. wet sample (in brackets the number of positive animals) were: Candida krusei (8); Saccharomyces cerevisiae (6); Pichia membranaefaciens (6); C. albicans (3); S. tellustris (C. bovina) (2); S. chevalieri (2); S. oleaceus (2); S. carlsbergensis (2); C. parapsilosis (2); C. tropicalis (2); S. italicus var. melibiosi (1); S. steineri (1); C. utilis (1); Torulopsis glabrata (1); not identified (1). Analysis of the counts of the three most frequent species showed an increase in the anal direction. It is concluded that C. krusei, P. membranaefaciens and S. cerevisiae are facultative intestinal saprophytes of swine.

SUMMARY: A mutant of Escherichia coli was isolated which showed a requirement for methionine+lysine when a fairly large inoculum of washed organisms was used. Cystathionine or homocysteine replaced methionine, and diaminopimelic acid replaced lysine; no other amino acid or growth factor was active. The amounts of the amino acids required to promote growth were only about one-tenth of the quantity of methionine and lysine found in the grown organisms. A quantitative study with 14C-glucose and 35S-sulphate confirmed that these amino acids were synthesized de novo. Although homoserine would not replace methionine for growth, the presence of unlabelled homoserine suppressed the incorporation of isotope from 14C-glucose into methionine and threonine, indicating that the accepted pathways are operative and that the block in methionine synthesis was in the formation of cystathionine. Small amounts of yeast extract replaced the amino acid requirement and decreased one-thousandfold the size of the inoculum required.

SUMMARY: A defined medium is described for the growth of Haemophilus influenzae and H. parainfluenzae which can be used either as a liquid medium or solidified with agar. The purine and pyrimidine, vitamin, amino acid and mineral salt requirements for three strains have been analysed.

SUMMARY: The effect of certain carbohydrates, nitrogen compounds and accessory growth factors on the growth and sporulation of several strains of Penicillium vermiculatum and P. wortmanni, as well as of many commonly occurring non-perithecial species, was studied. An initial low concentration of soluble sugar was conducive to perithecial formation in the two sexual species, and perithecial growth was best with polysaccharides as carbon source. Peptone was the most favourable nitrogen source; asparagine exerted an inhibitory effect in many cases. Of six B-group vitamins tested only thiamine had any marked effect. Similar effects of the nutritional factors were seen with the non-perithecial species generally.

SUMMARY: O-Methylthreonine (OM) inhibits multiplication and photosynthetic pigment synthesis in Euglena gracilis and Ochromonas danica; it does not inhibit Chlamydomonas reinhardi or Rhodopseudomonas palustris. Inhibition of multiplication and pigment synthesis may be prevented by l-isoleucine. OM also causes the permanent loss of chlorophyll and appreciable loss of carotenoids in E. gracilis and this may be prevented by l-isoleucine, α-aminobutyric acid, α-ketobutyric acid, l-threonine, l-homoserine, or l-methionine. α-Ketobutyric acid is most effective on a molar basis and is therefore postulated to be the target of OM inhibition.

Isoleucine plays a role in the biosynthesis of photosynthetic pigments and lipids in Euglena gracilis, for the incorporation of 14C-l-isoleucine radioactivity into both the pigments and lipids is markedly diminished by bleaching agents which prevent pigment synthesis without affecting multiplication, i.e. O-methylthreonine or streptomycin. When pigment synthesis is blocked amino acids accumulate in the culture supernate.

SUMMARY: A psychrophilic species of Cryptococcus, freshly inoculated cultures of which grew well in a glucose + salts + vitamins medium at 16° but not at all at 30°, was induced to grow rapidly for a period at 30° by previous incubation at 16°. A study was made of certain aspects of the biochemical composition of the cryptococcus in cultures maintained at 16° as compared with that in cultures transferred from 16° to 30°, in order to obtain information about the biochemical basis of the low maximum growth temperature for this organism. With the cryptococcus transferred from 16° to 30°, there was rapid utilization of intracellular reserves of total amino acids and total oxo acids. Exogenous sources of amino acids were unable to replenish the intracellular amino acid pool in the cryptococcus incubated at 30°. However, addition of α-oxoglutarate, citrate, or dl-isocitrate to cultures transferred to 30° after 120 hr. at 16° enabled the cryptococcus to continue to grow at the higher temperature; stimulation of growth at 30° was most marked in cultures supplemented with α-oxoglutarate. Other tricarboxylic acid cycle and related intermediates (pyruvate, acetate, succinate, fumarate, l-malate, oxaloacetate) had no growth-promoting effect. Stimulation of growth at 30° in the presence of α-oxoglutarate was obtained only in cultures which had been incubated for 2–4 days at 16°, indicating the existence of other temperature-sensitive metabolic processes in addition to those concerned in α-oxoglutarate synthesis.

SUMMARY: Twenty-five strains currently classified into 14 serological types or species of the genus Vibrio obtained from the NCIB and NCTC have been studied in detail for morphological, cultural and biochemical characters in two independent studies. The results indicate that these strains include members of three distinct taxonomic groups or genera, Vibrio, Pseudomonas and Comamonas. The new generic name Comamonas, type species C. percolons, replaces Lophomonas (Galarneault & Leifson) which is invalid.

SUMMARY: Sixty-one polarly flagellate bacteria, initially identified as such by the type of motility they displayed, were isolated from surface waters and classified on the basis of cultural and biochemical tests into three genera: Aeromonas, Pseudomonas, Comamonas. Sixteen similarly flagellated cultures from other sources were also found to be members of these genera. Some bacteria with a single polar flagellum and giving reactions of the Alcaligenes type were isolated. It is suggested that the definition of the genus Comamonas (Davis & Park) be extended to include such forms. The possibility of confusing Aeromonas with Vibrio and with some enterobacteria is discussed.

SUMMARY: Evidence is presented that the distinction, already made on nutritional grounds, between lactaphilic and glycophilic strains of acetic acid bacteria may be traced back to the metabolic level. Thus, the capacity of cell extracts to effect reversible transamination from glutamate to aspartate was well developed in lactaphiles, but only feebly so, or not at all, in glycophiles. Again, suspensions of lactaphiles possessed greater general ability to oxidize intermediates of the tricarboxylic acid cycle than did those of glycophiles. Cell extracts of lactaphiles possessed citrogenase activity, which was not detected in glycophiles. The conversion of l-aspartate to α-alanine by extracts of lactaphiles appeared to proceed by β-decarboxylation, not by transamination.

SUMMARY: Bacteriophages were isolated from the effluents of the cities of Oxford and Salisbury. They differ in their host range but are alike in that they contain hydroxy-methylcytosine and show dependence on tryptophan for adsorption. These properties, which had been described previously only in the T-group of coliphages, are now shown to be widespread.

SUMMARY: Bacteriophages which are tryptophan-dependent for adsorption are also sometimes heat-labile in the presence of added tryptophan. The inactivation is due to the discharge of the phage deoxyribonucleic acid (DNA). This phenomenon is most marked at two different monovalent ion concentrations and is thought to be due to production of lesions at two different sites on the phage tail.

SUMMARY: Colonies of four strains of Lactobacillus casei var. casei and three strains of L. casei var. rhamnosus investigated may develop rough outgrowths while growing on a medium containing no fermentable carbohydrate. Colonies do not form visible outgrowths when growing on the same medium containing more than 0·5% (w/v) glucose. Rough elements may be present in the latter colonies, but because of lack of a selective advantage do not show phenotypically. The rough outgrowths possess the characteristics of R variants. The biochemical reactions of the R variants are identical to those of the parent S form. The mutational origin of the R variants from wild S types is demonstrated by a method involving the direct observation of rough clones. The mutation rate involved is presented for six of the strains. In continuous culture in broth both the S and the R types are stable. On agar the R variant is also stable.

SUMMARY: A curly flagellar mutant obtained from a strain of Salmonella typhimurium was unstable and repeatedly dissociated ‘curly’ and normal subclones. Examination of flagellar antigens of the normal and the curly flagellar subclones demonstrated that the changes in flagellar shape corresponded exactly with phase variation: subclones with curly flagella were always in phase-1 (antigen-i), those with normal flagella were in phase-2 (antigen-1, 2). In transduction from a normal flagellar strain to the curly phase-1 strain, transductional clones with normal flagella were isolated. The transductional clones showed the antigen of the donor in phase-1 and that of the recipient in phase-2. This indicates that the phase-1 curly determinant is closely associated with the phase-1 antigen type determinant, H1 .

Seven curly mutants were obtained from a strain of Salmonella abortus-equi: one with antigen-a (phase-1), and four with antigen-e, n, x (phase-2), and two with antigen-1, 2 (phase-2) from a transductional recombinant given antigen-1, 2. Transductional analysis with these strains showed that the phase-2 curly determinant is closely associated with the phase-2 antigen type determinant, H2 ; and the phase-1 curly determinant with H1 . In cross-absorption experiments with antisera prepared against flagella of either normal or curly mutant, no antigenic difference between normal and curly flagella could be detected. It is inferred that H1 and H2 are the primary structural determinants of flagellar protein in phase-1 and phase-2 respectively; mutation in H1 or H2 may cause an altered configuration of flagellar protein, resulting in a change in antigenic type, or in flagellar shape, or it may cause the failure of flagellar morphogenesis. Attempts to obtain recombination by transduction between the curly flagellar determinants in each of the phases have beeen unsuccessful; this suggests that in each phase the mutant sites of the curly types are very closely linked or identical.

SUMMARY: A neutralization test for the viruses of trachoma and inclusion blennorrhoea grown in HeLa cell cultures is described. Antiserum titres, which are independent of virus concentration over a wide range, can be accurately and reproducibly estimated. Limited cross-neutralization tests indicate a close antigenic relationship between one strain of trachoma virus and two strains of inclusion blennorrhoea.