- Volume 84, Issue 2, 1974

Summary: Bacitracin production by Bacillus licheniformis atcc10716 is markedly inhibited by glucose. This inhibitory effect is due to the lowered pH and undissociated organic acids produced by the metabolism of glucose. The possibility that catabolite repression is an incidental result of low pH and the production of organic acids from glucose during growth is discussed.

Summary: Of 48 fungal isolates, 28 (including one Penicillium and three Aspergilli) secreted milk-clotting enzymes. This activity was in general related to the mycelial growth of a given isolate, but not with pH change of the culture filtrate during incubation. It was not found when mucilage was formed by isolates capable of doing so. The ratio of general proteolytic activity to milk-clotting activity varied from one organism to another, and with the age of culture of the same fungal strain.

Summary: The mechanism of mercury inhibition of invertase, β-d-fructofuranoside-fructohydrolase EC. 3.2.1.26, from Saccharomyces cerevisiae, both in vitro and in vivo, is similar with respect to effective mercury concentrations. Contrary to previous reports on invertase from S. cerevisiae, the enzyme in this study does not dimerize in the presence of mercury nor does it exhibit competitive inhibition kinetics. A further apparent inconsistency with previous work is the marked dependency of inhibition upon pH and anion concentrations.

Summary: Hyphomicrobium sp. were grown on ethanol, acetate, 3-hydroxybutyrate and methanol. The specific activities of the following enzymes were measured in cell-free extracts of Hyphomicrobium strain x: ethanol dehydrogenase, acetaldehyde dehydrogenase, acetothiokinase, 3-hydroxybutyrate dehydrogenase, β-keto thiolase, citrate synthase, aconitate hydratase, isocitrate dehydrogenase, α-oxoglutarate dehydrogenase, succinate dehydrogenase, fumarate hydratase, malate dehydrogenase, isocitrate lyase, malate synthase, malate dehydrogenase (decarboxylating), phosphoenolpyruvate carboxylase, pyruvate kinase, phosphoenolpyruvate carboxykinase, phosphopyruvate hydratase and phosphoglycerate mutase. From a comparison of the specific activities of these enzymes in the different cell-free extracts, it was concluded that during growth of Hyphomicrobium sp. on either ethanol, acetate or 3-hydroxybutyrate, energy and reducing power is generated mainly by the tricarboxylic acid (TCA) cycle. Carbon is assimilated via the glyoxylate cycle with phosphoenolpyruvate carboxykinase functioning as the main gluconeogenic enzyme. The conversion of ethanol, acetate and 3-hydroxybutyrate to acetyl-CoA occurs by pathways previously reported in other micro-organisms.

Summary: Four toxigenic strains each of Aspergillus flavus and A. parasiticus were grown in Schmid peptone--glucose medium to determine their ability to carry out nitrification and in a yeast extract--sucrose (YES) medium to test their toxigenicity. Two nitrifying strains each of A. flavus and A. parasiticus were grown in YES medium to examine their ability to form aflatoxin. A steam-distillation method was used to determine ammonium-, nitrite- and nitrate-nitrogen, whereas thin-layer chromatography and fluorometry served to measure aflatoxin content of broths. All eight toxigenic strains produced nitrate in Schmid and YES media when incubated without shaking. Shaking of cultures tended to increase the amount of nitrate formed in Schmid but not in YES medium. Amounts of aflatoxin produced varied with media and methods of incubation. All four nitrifying strains formed aflatoxin in YES medium. Toxigenic and nitrifying strains that gave high yields of aflatoxin did not always produce high levels of nitrate.

Summary: Mechanical damage to hyphae of some A2 compatibility-type Phytophthora spp., by cutting with a cork borer or scalpel, can induce formation of pairs of gametangia followed by oospores. The A1 compatibility types examined did not respond significantly to damage. Two homothallic species of Phytophthora responded to mechanical damage by forming increased numbers of gametangia. Induction of gametangia in A2 Phytophthora cinnamomi following damage depends on the composition of the medium. Injury produced by H2O2 or ether also induced sexual reproduction in A2 P. cinnamomi. It is concluded that the mechanism by which gametangia are induced in A2 Phytophthora strains by Trichoderma viride may involve damage and that production of oospores in response to damage may be significant in the survival of Phytophthora.

Summary: Strains of lactobacilli were examined for lysogeny after treatment with mitomycin C. Forty strains belonging to 7 species out of 148 strains of 15 species were lysed by mitomycin C. Lysis was strongly dependent upon the concentration of mitomycin C, temperature and the age of the cultures.

Phage-like particles were observed in 31 out of 40 lysates by electron microscopy. Particles from ten lysates – four from Lactobacillus casei B, five from L. casei C and one from L. acidophilus – produced plaques when plated on suitable indicator strains and were thus considered to be active phages. The remaining 21 lysates that contained phage-like particles failed to produce plaques but four of them inhibited the growth of other lactobacilli. It was concluded that the particles in these lysates were defective phages.

Activities, shapes, dimensions and serological properties of the newly induced phage-like particles were also studied.

Summary: Properties of a transducing system with a phage able to transduce a kanamycin resistance marker of the T compatibility group R factor R394 at high frequency are described. The phage was detected in Proteus mirabilis strain pm5006 transduced to kanamycin resistance by phage 34 grown on P. mirabilis strain pm13 carrying the R factor. The pm5006 transductants, specially selected at the lowest multiplicities of infection (m.o.i.) of the high frequency transducing (h.f.t.) phage, are normal lysogens. They liberate h.f.t. phage spontaneously and high-titre phage may be obtained by u.v. induction. The phage is serologically identical to phage 34 and is defective in that, at low m.o.i., transduction frequency is increased by the simultaneous presence of homologous non-transducing phage. Ultraviolet irradiation of the h.f.t. lysate produces an exponential fall in transduction frequency. It is concluded that the defective phage transduces by lysogenization. Phage present in h.f.t. lysates can also transduce various chromosomal markers of pm5006 at low frequencies. These low-frequency transductants are usually not kanamycin resistant. Transductants do not transfer the kanamycin resistance marker conjugally and produce kanamycin-sensitive normal lysogenic segregants at a high rate. Strain pm5006 is cryptically lysogenic for a phage which is morphologically and serologically identical to phage 34 and many of the particular features of this transduction system are explicable in terms of complementation or recombination between genes of the phages involved.

Summary: Three Pseudomonas aeruginosa phages specific for bacteria harbouring the P-group plasmid RP1 have been isolated, and their properties compared with those of a previously described sex-specific phage, PRR1 (Olsen & Shipley, 1973). These phages are distinguishable from each other by various criteria, although in terms of host range to FP+ and RP+ lines of P. aeruginosa pao they comprise broadly two groups. Thus all the phages infect bacteria harbouring any of a group of plasmids with similar properties to those of RP1, but whereas the filamentous phage Pf3 is specific for this group, the host ranges of PRR1, PR3 and PR4 are considerably wider. Nevertheless, with one exception, this does not extend to plasmids isolated outside the United Kingdom, which suggests that all these plasmids share a common ancestry even though by other criteria they constitute three fairly discrete subgroups. Of the plasmids that fail to allow phage propagation, three, when present in the same cell as RP1, reduce its susceptibility to phage infection. This inhibition may reflect a relationship between these elements, similar to that found among plasmids of Enterobacteria. A correlation is observed between the susceptibility of bacteria to phage infection and their ability to mediate plasmid transfer, such that these phages can conveniently be used to isolate both derepressed or transfer-defective mutants of various R factors.

Summary: Cytological aspects of monokaryotic variants produced by axenic cultures of Puccinia graminis Pers. f.sp. tritici Erikss. & E. Henn. were studied. Mitotic nuclei of variants at the end of stage I of division (late prophase to metaphase) contained approximately the same number of chromatinic bodies as haploid nuclei in dikaryotic hyphae of the parental wild type. However, an examination of spores produced by pathogenic variants showed that the size of uredospores and teliospores, the number of nuclei per spore cell, and the size of nuclei in teliospores, were all suggestive of the monokaryotic variants being diploid rather than haploid. Diploidy was also consistent with the occasional breakdown of both non-pathogenic and pathogenic monokaryons to form dikaryotic somatic cells; hyphal anastomosis was observed within one such region of dikaryotic cells produced by a non-pathogenic variant. On balance, it is concluded that nuclei in both pathogenic and non-pathogenic monokaryotic variants are diploid, and that mitotic chromosome counts do not distinguish between haploid and diploid nuclei. Diploidy is discussed in relation to naturally occurring monokaryotic rust fungi and to somatic variation in populations of dikaryotic rusts.

Summary: The effect of 14 arginine analogues on the growth of Pseudomonas aeruginosa in a liquid mineral medium with either l-glutamate or l-ornithine as the sole carbon and nitrogen source was investigated. Two analogues, l-indospicine and l-arginine hydroxamate, inhibited growth markedly. The former was most effective in the or-nithine medium and the latter only in the glutamate medium.

The inhibition by arginine analogues of the first two enzymes of the arginine pathway, N-acetylglutamate synthetase and N-acetylglutamate 5-phosphotransferase, was studied. It was found that inhibition of these two feedback-sensitive enzymes did not correlate with inhibition of growth. O-(l-norvalyl-5)-isourea, which was a rather weak inhibitor of growth, was at least three times more active as an inhibitor of the enzymes than l-indospicine and l-arginine hydroxamate. These two analogues were about ten times less effective than l-arginine, the strongest inhibitor of both enzymes.

Summary: Bacillus amyloliquefaciens took up inorganic ions from the medium during growth. Their distribution between the cytoplasmic fraction and the envelope varied from almost exclusively cytoplasmic to completely envelope-bound in the order: K+, 4·7%; Mg2+, 32·0%; phosphate, 60·2%; Na+, 80.4%; Ca2+, 96·1%; and Cl−, 100% envelope-bound. During the transition from minimum to maximum rate of extracellular enzyme secretion the intracellular levels of the following ions were unchanged at K+, 583±54 mm; phosphate, 459±40 mm; Mg2+, 56±6 mm; and Na+ 22±4 mm.