- Volume 44, Issue 2, 1966

SUMMARY: Some yeast strains are able to give rise to “petite” mutants upon treatment with euflavine while some other strains do not give rise to cytoplasmic respiration-deficient mutants. Nevertheless euflavine mimics the effect of the petite mutation in those strains which are unable to give petite mutants. There is a correlation between the presence of the Crabtree effect in a yeast strain and its ability to give petite mutants.

SUMMARY: The properties of three transducing phages derived from providence strains NCTC 9207, 9246, 9290 and phage M derived from Proteus morganii NCTC 10041 are described. The providence phages are present in supernatant fluids of young broth cultures; phage M is ultraviolet-inducible. The 3 providence phages only attack and transduce into providence strains NCTC 9211, 9295; the action of phage M is restricted to P. morganii NCTC 2815. The phages transduce different markers at rates of 3 × 10−7—1 × 10−6/phage adsorbed and are thus capable of generalized transduction. No abortive transductants were encountered. The providence phages are serologically related. Morphologically the phages resemble the salmonella transducing phage P22 but phage M differs in that it possesses a delicate collar round the short neck. The infectivity of the phages is Ca2+ independant. Phage M is more heat susceptible than the providence phages while its transducing particles are chloroform sensitive. Mutants of providence NCTC 9211, 9295 lysogenized by the phages are competent recipients in transduction experiments, while mutants of strain NCTC 2815 lysogenized by phage M yield no transductants when treated with suitable lysates of this phage. Small doses of ultraviolet irradiation of providence phages increase transduction rates. Phage M lysates similarly treated show no such stimulation. The phages have deoxyribonucleic acid base compositions similar to the organisms which they transduce and density gradient centrifugation reveals that transducing activity forms single peaks 2 or 3 fractions heavier than corresponding plaque-forming particles.

SUMMARY: Three similar and apparently previously unrecorded viruses were studied and found to be most like viruses of the turnip yellow mosaic group. Andean potato latent virus (APLV) was obtained from primitive cultivated potatoes collected in the high tropical Andes, dulcamara mottle virus (DMV) from Solanum dulcamara L. growing near Rothamsted, and Ononis yellow mosaic virus from Ononis repens L. growing in many parts of England. All three viruses are readily transmitted by sap inoculation; APLV and DMV are transmitted through the seed of infected plants; DMV is transmitted by the flea beetle Psylloides affinis Paykull. Plants infected by one of the viruses are not protected against infection by the others.

Purified preparations of these viruses have many common properties. Each virus has isometric particles 25-30 mμ in diameter, indistinguishable in appearance from one another and from the particles of turnip yellow mosaic virus. Preparations of each contain mainly two types of particles with sedimentation coefficients of about 115S and 55S, corresponding to infective nucleoprotein particles and non-infective “empty” particles respectively. Each contains nucleic acid with a molar base composition of about G 16% A 22% C 33% U 29%. The three viruses are serologically related; antisera titres are 8-128 times greater with homologous than with the heterologous viruses. No serological relationship was found between these viruses and turnip yellow mosaic, wild cucumber mosaic, cocoa yellow mosaic, squash mosaic and red clover mottle viruses.

Plants infected with APLV or DMV when sprayed with solutions of 2-thiouracil or 6-azauracil produced fewer nucleoprotein particles and more “empty” protein particles, than plants sprayed with water.

SUMMARY: Pseudomonas aeruginosa NCTC 8203 was shown to metabolize guanine by deamination to xanthine, which was then oxidized to uric acid and further products. Guanine deaminase activity was present in non-induced bacteria but was 3-4 times greater in guanine-induced bacteria. Xanthine oxidase, and the uric acid oxidizing enzymes, were not found in bacteria grown in a minimal salts medium but were induced by adding guanine or xanthine to the culture medium towards the end of the growth period. When uric acid was added, only the uric acid oxidizing enzymes were induced. Enzyme induction also occurred when washed suspensions of the bacteria were incubated with guanine, xanthine or uric acid in Warburg flasks. 8-Azaguanine was deaminated more rapidly than guanine by non-induced bacteria and the rate was again greater with guanine-induced bacteria. 8-Azaguanine and 8-azaxanthine were not oxidized and did not induce the synthesis of deaminases or oxidases. 8-Azaguanine and 8-azaxanthine had no effect on the oxidation of guanine, xanthine or uric acid by fully induced bacteria. Equimolar concentrations of 8-azaguanine inhibited adaptation to the oxidation of guanine, xanthine and uric acid when added before the substrates. 8-Azaxanthine, under the same conditions, delayed adaptation to guanine and xanthine oxidation, and completely inhibited adaptation to uric acid. Mutant strains were isolated which were resistant to 10 mM-8-azaguanine and 5 mM-8-azaxanthine which completely inhibited growth of the parent strain. Another class of mutants was isolated resistant to 8-azaguanine and not resistant to 8-azaxanthine. Both classes of mutants were indistinguishable from the parent strain in their susceptibility to 8-azaguanine and 8-azaxanthine inhibition of adaptation to purine oxidation.

SUMMARY: A reaction mixture is described consisting of a buffered solution of amino acids, salts, growth factors and glucose in which freshly harvested washed Streptococcus lactis incorporated radioactive tracers and synthesized nisin. Rapid nisin synthesis started after a delay of 30-60 min. but bacteria pre-incubated in the reaction mixture synthesized nisin without delay although the rate of protein synthesis remained the same as that of freshly harvested bacteria. Although growing S. lactis is sensitive to penicillin and mitomycin these antibiotics had no effect on nisin synthesis by washed organisms. Actinomycin D inhibited uptake of tritiated uridine immediately and inhibited nisin synthesis after a delay of about 60 min. Antibiotics which interfere with protein synthesis, e.g. chloramphenicol, puromycin and terramycin also interfered with nisin synthesis. The inhibition was immediate and occurred irrespective of whether the antibiotics were added at the beginning of an experiment or after 50 min. Nisin synthesis was more sensitive than protein synthesis. The data suggest that nisin synthesis occurs by a mechanism similar to that of protein synthesis.

SUMMARY: There is evidence that oxidation of o-cresol by Pseudomonas aeruginosa proceeds through 3-methylcatechol and 2-hydroxy-6-oxohepta-2,4-dienoic acid. 3-Methylcatechol has been characterized as a metabolite in growing cultures, and is oxidized by cells or cell extracts obtained from cultures grown on o-cresol but not by those grown on glucose. The rates of dissimilation of 2-hydroxy-6-oxohepta-2,4-dienoic acid are in excess of its rates of formation from 3-methylcatechol by extracts of cells. The catechol 2,3-oxygenase is formed in response to a variety of inducers and will cleave the ring of catechol and 4-methylcatechol also. The low specificity of the 2,3-oxygenase and earlier enzymic activities (hydroxylases), to both inducers and substrates, is discussed.

SUMMARY: Although staphylococcal β-haemolysin does not lyse rabbit erythrocytes, it is absorbed by these cells and produces a prelytic change which can be recognized by facilitation of other haemolytic reactions. Combination of two haemolytic processes serves in general to detect latent effects of lytic agents or to accelerate their quantitative evaluation. β-Haemolysin apparently causes the same primary change in sheep and rabbit erythrocytes, namely enzymic splitting of sphingomyelin and related compounds, but only the sheep cells, when subjected to cooling, are able to undergo a second reaction, responsible for the release of haemoglobin.

SUMMARY: The results are presented of a survey of NAD and NADP concentration in twenty micro-organisms. They fell into three categories with respect to NAD concentration. (i) High NAD (> 4·5 μmoles/g. dry weight) in obligate anaerobes, members of the Lactobacillaceae and Saccharomyces cerevisiae. (ii) Medium NAD (1·0-3·0 μmoles/g. dry weight) in faculative anaerobes, photosynthetic bacteria and Nocardia globerula. (iii) Low NAD (< 0·9 μmoles/g. dry weight) in obligate aerobes.

Different categories were not found with respect to NADP concentration.

Consistent differences in NAD concentration due to conditions of aeration were not found, but growth on different substrates frequently led to changes in NAD concentration. The concentration of NAD in Streptococcus faecalis grown on gluconate was only 6% of the concentration in glucose-grown organisms. In Pseudomonas oxalaticus NAD concentrations when grown on formate or oxalate were 13 and 8 times, respectively, greater than the concentration in acetate-grown organisms.

NADP concentrations in Leuconostoc mesenteroides and Streptococcus faecalis were increased 2- to 5-fold by aeration. In Nocardia globerula, Streptomyces griseus and Bacillus megaterium the concentrations of NAD found after growth in complex media were 3-5 times greater than the amounts found after growth on minimal media. This effect was not observed with Pseudomonas fluorescens.

SUMMARY: ‘Substrate-accelerated death’ ( Postgate & Hunter, 1963a ; 1964) occurred when a nitrogen-limited variant of Aerobacter aerogenes NCTC 418 ( Postgate & Hunter, 1962 ) was starved at growth temperature (37° or 40°) in aerated saline buffers containing ammonium ion; it was not observed when the parent strain of A. aerogenes or Escherichia coli (MRE 162) was grown and starved under similar conditions. Sulphate ion increased the lethal effect of ammonium ion on the variant and magnesium did not abolish either the effect of ammonium or ammonium + sulphate ions. The A. aerogenes variant differed from the parent strain in morphology, colonial appearance on nutrient agar, biochemical and immunological reactions and ability to synthesize polysaccharide. In ammonium-limited medium at 37° or 40° at a dilution rate near 0·25 hr−1 the variant contained 3-5% and the parent strain 12-16% of dry weight as polysacharide; in spent medium or phosphate buffer at 37° with added glycerol the rate of polysaccharide synthesis by the variant was about 25% that of the parent strain. When grown in nitrogen-deficient medium with excess glycerol in batch culture, populations of the variant containing 25% polysaccharide were obtained; the survival of the polysaccharide-rich variant was not affected by ammonium ion.

SUMMARY: The relationships of eleven strains of Trypanosoma brucei were determined by agglutination tests with antisera to the basic and predominant antigens of the strains to assess (a) the relative values of these antigens for classification purposes, and (b) the antigenic diversity of T. brucei in Nigeria. The indications of the antigenic relationships of the strains obtained by comparisons based on both types of antigens were very similar, but comparisons of predominant strain antigens were easier to make and were applicable to more strains than were comparisons of basic strain antigens. Clones prepared from four strains isolated in one place in Nigeria were antigenically related, but clones of two other strains from the same area were antigenically distinct. Six strains from widely separated localities were antigenically different and produced few antigens in common.

SUMMARY: The magnesium and RNA contents of Aerobacter aerogenes, growth-limited by Mg2+, K+, NH4+ or carbon source, in defined media at 35° increased with growth rate. The results support the view that the amounts of these constituents are functions of the growth rate and are inter-dependent. Up to 26% of the total Mg2+ of bacteria freshly harvested from cultures containing excess magnesium was loosely bound to the bacterial surface; this adsorbed Mg2+ was removed by washing with 0·85% (w/v) NaCl but was unaffected by distilled water. Mg2+-limited bacteria had no surface-adsorbed magnesium. Surface-adsorbed Mg2+ stimulated polysaccharide synthesis, and affected the response of bacteria in saline buffer to stresses including starvation, heat-accelerated and substrate-accelerated death, and cold shock.

SUMMARY: Species of the genus Staphylococcus have a guanine + cytosine (GC) content in DNA within the range 30·7-36·4 moles %. All the Gram-positive cocci so far designated as micrococci and sarcinas which produce acid from glucose when grown under anaerobic or aerobic conditions and have a GC content in DNA within this range should be also classified as Staphylococcus. On the other hand species of the genus Micrococcus have a GC content in DNA within the range 66·3-73·3%. All the Gram-positive cocci hitherto designated as sarcinas and staphylococci which do not produce acid from glucose under aerobic or anaerobic conditions or only aerobically and which have a GC content in DNA within this range, should be also classified as Micrococcus. The range of GC content as outlined is approximate; it will be made more accurate (perhaps a little broader) when more data are available on the DNA base composition of the species belonging to the family Micrococcaceae.

On the basis of their DNA base composition the strains belonging to the genus Micrococcus are divided into three groups: group 1 (70·8-73·3 moles % GC); group 2 (67·5-69·5 moles % GC); group 3 (66·3-67·0 moles % GC). Similarly the strains belonging to the genus Staphylococcus have been divided into three groups: group 5 (36·4 moles % GC); group 6 (33·3-34·2 moles % GC); group 7 (30·7-32·7 moles % GC). Strains within each group are believed to be phylogenetically related. When subjected to Adansonian analysis, the strains of the individual groups were clustered into subgroups. Each subgroup comprised the strains with approximately the same DNA base composition and a high % similarity of physiological and biochemical characters. Strains clustered into subgroups are believed to be genetically closely related, some may be identical. The following subgroups are suggested: micrococcus subgroups 1a, 1b, 2a, 2b, 2c, 3a, 3b; staphylococcus subgroups 5a, 6a, 7a. Arabic numerals refer to the designation of the group.

The classification of micrococci presented in this paper is substantially the same as that of Baird-Parker (1965) . The authors are of the same opinion as Baird-Parker (1965) that Micrococcus denitrificans should be reclassified with the Gram-negative genera.

SUMMARY: An enzyme extracted from Bacillus cereus spores caused to germinate spores of this organism which had been sensitized by reagents which rupture disulphide bonds. Inactivation of the enzyme by thiol-blocking agents and by oxidation, and reactivation by reduction suggested that the enzyme's ability to germinate spores depended on thiol groups. No evidence was obtained to support the hypothesis that the enzyme was present in dormant spores in the oxidized inactive form and became reduced and active during germination. When spores were disrupted at pH 3 the enzyme was found to be bound to debris; probably on or within the central core of the spore. At pH 5·8 or below the enzyme remained bound to the debris, but at pH 7·0 the enzyme was irreversibly released when the ionic strength of the medium was high. In solutions of sodium phosphate less than 0·05 M, the enzyme remained mostly bound even at pH 7·0. It was largely released when the concentration of sodium phosphate was increased to 0·2 M. Extracts of germinated spores contained more unbound and less bound enzyme than extracts of ungerminated spores, suggesting that release of enzyme from a bound form occurred during germination of the spores.

SUMMARY: The uptake of aliphatic amides by Pseudomonas aeruginosa 8602 was studied by using 1-14C-acetamide and 1-14C-N-acetylacetamide (a non-metabolizable analogue). 1-14C-acetamide was accumulated by the wild-type strains and by an amidase-negative mutant. The maximum ratio of internal to external concentration measured was 100:1. 1-14C-N-acetylacetamide was concentrated by the wild-type strain and the maximum ratio of internal to external concentration measured was 80:1. No difference was detected in amide uptake as between induced and non-induced cultures of the wild-type or mutant strains. It is concluded that the organism possesses a constitutative permease for these amides. Cyano-acetamide had no significant effect on N-acetylacetamide accumulation by the wild-type strain at concentrations which repressed amidase synthesis. Repression of amidase synthesis by amide analogue repressors is therefore not due to inhibition of amide uptake by the bacteria.