- Volume 33, Issue 1, 1963

SUMMARY: A phage able to transduce a streptomycin resistance marker in Proteus mirabilis can also separately transduce the swarming characteristic between variants of two strains of P. mirabilis. Motile non-swarming variants were made to swarm on agar by incorporation of a swarming gene via a phage lysate of a swarming strain. The production of swarms by motile non-swarming variants when treated with phage lysates of other pheno-typically similar strains indicated that at least three non-homologous factors control swarming. An O variant could also act as a donor of the swarming gene. This is because the O strain possesses an intact swarming centre which is masked by the absence of active flagella. This O variant was transduced to swarming by phage lysates of motile non-swarming strains or of a swarming strain. The gene transduced here was concerned with the presence of flagella. Factors controlling two morphological varieties of swarming were separately transduced to suitable recipients and a locus able to modify wild-type swarms was identified.

SUMMARY: Streptomycin is a specific antiviral agent for a variety of bacteriophages active against Streptococcus faecium, S. faecalis, S. liquefaciens and S. zymogenes since it inhibits bacteriophage growth even when the host is resistant to the antibiotic. An analysis of the mode of action of the antibiotic in this system reveals that it probably has two effects. If the antibiotic is present before adsorption, it inhibits injection of the phage DNA. This effect is readily reversible. If the antibiotic is added after adsorption, it appears that injection is not inhibited, but that the phage genome is inactivated. The antibiotic has no effect on replication of the phage once the genome has become established in the host cell. This is consistent with the hypothesis that the phage DNA exists transiently at a streptomycin-accessible site, and then moves to a site of replication which is inaccessible to the antibiotic. Streptomycin-resistant phages probably have a different injection mechanism from streptomycin-sensitive phages.

The senior author has reported similar findings for an RNA bacteriophage of Escherichia coli. The implications of this work for virus chemotherapy and for analysing the mode of penetration into the cell of virus nucleic acid are discussed.

SUMMARY: The nutrition and physiology of some aquatic Hyphomycetes were examined. Optimum growth temperatures were below those usually encountered amongst aquatic moulds. Several species utilized almost all the carbohydrates tested and most gave a molar growth yield between 80 and 95 mg. mycelial dry weight/m-mole carbohydrate utilized. Of the vitamins tested none appeared to be essential nutrients for most species, though some were stimulatory. Nitrate and ammonium ions both served as adequate nitrogen sources, with a preference for the latter. The ways in which aquatic Hyphomycetes may have nutritional advantages over their possible ecological competitors are discussed.

SUMMARY: The chemical form and quantity of nitrogen supplied during the growth of wild-type Neurospora crassa mycelia had a significant effect on total protein synthesis and NADP-specific glutamate dehydrogenase (NADP-GD) specific activity. Both NADP-GD specific activity and protein yields were high when NH4+ was the sole nitrogen source. At NH4+ concentrations up to the optimal for protein synthesis, NADP-GD production and protein synthesis were proportional; at higher concentrations NADP-GD specific activity decreased disproportionately. Glutamate alone, more markedly glutamate + NH4+, or a mixture of amino acids (e.g. sodium caseinate), similarly depressed NADP-GD specific activity. These data support the contention that excess nitrogen in some form acts as a specific NADP-GD repressor. Evidence is presented from experiments with nitrogen-starved mycelia that low concentrations of NH4+ per se may act to de-repress NADP-GD production. Under conditions of early nitrogen starvation, followed by a short growth period after NH4+ supplementation, more than 1 % of the soluble protein in a heat-treated extract was found to be NADP-GD.

SUMMARY: Conidia of Botrytis cinerea have a 2-layered cell wall, a thin electron-dense outer layer and a thicker electron-transparent inner one. The cell contents comprise typical nuclei, mitochondria and endoplasm with a surrounding plasmalemma and a sparse endoplasmic reticulum. There are a few small peripheral vacuoles. On germination the outer spore wall ruptures and the emergent germ tube is surrounded by the elastic inner one and what appears to be a sheath of mucilage. A cross wall with a simple central pore is laid down at the base of the germ tube at a very early stage. As the germ tube elongates the contents of the spore flow into it, causing a large vacuole to form in the centre of the original spore. The numbers of nuclei and mitochondria suggest that divisions of these organelles take place during the early stages of germination. The mucilaginous sheath surrounding the germ tube appears to condense to give a thin electron-dense outer zone to the wall at the base of the germ tube.

SUMMARY: The effect of size of inoculum on growth and carbon metabolism of Aspergillus oryzae and several other Aspergillus species was studied. During most of the development a culture from a small inoculum, as compared to a large-inoculum culture, had a smaller specific rate of respiration, formed more ethanol and acids per unit weight of mycelium, and metabolized more carbohydrate to produce a given amount of growth. It seems that this inefficient utilization of carbon source is due not only to the production of a smaller amount of energy but also to an inefficient utilization of the released energy. The higher degree of inefficiency appears to be the result of the aging process which a small-inoculum culture undergoes during its development to the stage of growth of a young large-inoculum culture; the latter also shows a decrease in efficiency during cultivation.

SUMMARY: The influence of size of inoculum on the nitrogen metabolism of Aspergillus oryzae in submerged culture was studied. In producing a given weight of mycelium a large-inoculum culture, as compared with a small-inoculum culture, showed a higher degree of assimilation of nitrogen and a lower excretion of nitrogen over most of the growth curve. This comparatively greater efficiency of the large-inoculum culture became more pronounced when mechanical stress in the culture was increased. Under high mechanical stress, the inefficiency of a small-inoculum culture was so marked that in forming unit weight of mycelium it utilized more inorganic nitrogen than did a large-inoculum culture.

SUMMARY: A method is described for assaying flagella of Salmonella typhimurium based on the incorporation of a 14C-labelled amino acid, mechanical separation of the flagella from the bacteria, and measurement of the radioactivity of the isolated flagella. There is no detectable lag before the appearance of L-[(G-3H]leucine, or L-[Me-14C]methionine in the flagella, and the rates of incorporation of these amino acids into flagella paralleled the rates of incorporation into the general cell protein. Mechanical removal of the flagella did not affect their subsequent rate of formation. The amino acid, ɛ-N-methyllysine, present in flagellin, can be labelled with either L-[U-14C]lysine or L-[Me-14C]methionine. Using ɛ-N-methyl-lysine as a marker, it has not been possible to detect soluble protein precursors in the formation of flagella by S. typhimurium.

SUMMARY: When several strains of Haemophilus vaginalis were grown on Casman rabbit blood agar, individual morphological and cultural differences were noted between the Amies strains which formed pleomorphic and filamentous organisms and large, umbonate colonies, and the Dukes, Edmunds, King and U/L strains which were microscopically coccobacillary to bacillary, non-filamentous, and formed minute convex smooth colonies. Dukes, Edmunds, King and U/L strains required whole blood for maintenance while a whole blood derivative, e.g. peptic digest or Difco chocolate-yeastolate agar, was sufficient for the maintenance of the Amies strains. Serological studies by tube agglutination, direct, indirect and inhibition immunofluorescent methods showed that Dukes, Edmunds, King and U/L strains reacted in a homologous manner with H. vaginalis antisera nos. 317, 394 and 4984. Amies strains did not react with these antisera. However, Amies strains cross-reacted with H. aegyptius antiserum 180 a, while the Dukes, Edmunds, King and U/L strains did not react with this antiserum.

SUMMARY: The application of immunofluorescent techniques for the detection and identification of Haemophilus vaginalis in vaginal secretions by using fluorescent H. vaginalis antiglobulin (strains nos. 317, 4984) were found to be as specific and sensitive as cultural methods and had the advantage of being simple and rapid.

SUMMARY: A polysaccharide constituted primarily of a unit of N-acetylneuraminic acid, two of glucosamine and one of an acid labile nitrogenous component was extracted from Citrobacter freundii O5:H30. The material after purification gave a single peak in the ultracentrifuge. N-acetylneuraminic acid and 4-oxo-norleucine were isolated from hydrolysates of the polysaccharide. A similarly constituted polysaccharide was obtained from Salmonella dahlem. C. freundii O5:H30 and S. dahlem were shown previously to be serologically related to one another and the results of the present investigations indicate that a chemical relationship also exists between these micro-organisms. Moreover, it is suggestive that the serologically related S. djkarta which contains neuraminic acid is related chemically to S. dahlem and C. freundii O5:H30. In sum, it is concluded that derivatives of neuraminic acid exist in association with other amino sugars and amino acids in mucopolysaccharides of bacterial origin as well as in those derived from mammalian origin.

SUMMARY: A method is described for purification of bacterial flagella by elution of these organelles from a DEAE cellulose column by NaCl gradients.

SUMMARY: Seventy-five mutants with alterations in penicillinase formation were isolated from a strain of Staphylococcus aureus inducible for penicillinase. The mutants fell into three main categories on the basis of penicillinase activity and inducibility: (i) microinducible mutants which formed decreased amounts of penicillinase but retained the property of inducibility; (ii) penicillinase-negative variants which produced no detectable penicillinase and which showed no effect of inoculum size on penicillin resistance; (iii) strains with a wide range of penicillinase activities that produced the enzyme constitutively. Treatment of the wild-type strain with ethylmethane sulphonate increased the frequency of occurrence of microinducible and constitutive mutants but did not alter the incidence of the penicillinase-negative variants which were present in all cultures at a frequency of about 10−3. Representative mutants of each class were examined for ability to revert to wild type and to give wild-type recombinants in transductional crosses. The constitutive strains and the microinducible strains behaved like point mutants in that they reverted and in that they gave wild-type recombinants. The penicillinase-negative mutants, however, behaved differently in that they were not observed to revert nor did they give wild-type recombinants in crosses, either with one another or with microinducible or constitutive mutants. A naturally occurring penicillinase-negative strain of S. aureus behaved similarly to the penicillinase-negative mutants in these respects. The possibility that the penicillinase region in S. aureus is associated with a plasmid and thus inherited extrachromosomally is considered and discussed. The properties of the penicillinase-negative variants could be explained as resulting from the loss of such a plasmid. Consistent with the plasmid hypothesis is the finding that ultraviolet irradiation of transducing phage produced an exponential decline of transducing titre for penicillinase; against it is the failure of acridine orange to increase the frequency of the penicillinase-negative variants.

SUMMARY: Debaryomyces subglobosus (British National Collection of Yeast Cultures, ncyc 459) excretes riboflavin at the end of the growth period in batch culture and the yield depends on the concentration of iron in the medium. Yields of riboflavin in excess of 200 μg./ml. were obtained in media of low iron content but production was completely inhibited at Fe concentrations greater than 200 μg./l. D-Arabitol was produced simultaneously, increased yields of it being obtained at high iron concentration, but riboflavin production was then decreased. Procedures are described for the recovery of riboflavin and D-arabitol from the culture fluid.

SUMMARY: Experimental batches of hay were baled at different moisture contents, and the microbial and biochemical changes studied by sequential sampling. The type of hay obtained could, in general, be related to the initial moisture content, and to the temperature subsequently attained. Good hays (about 16 % moisture) heated little and contained a small but diverse microflora. Hays baled at about 25 % moisture heated to about 45° and moulded, mainly with Aspergillus glaucus. Wet bales, with initial moisture contents of about 40 %, became very hot (60°-65°) and contained a large flora of thermophilic fungi, particularly Aspergillus fumigatus, Absidia spp., Mucor pusillus, Humicola lanuginosa, and actinomycetes. During the initial heating period, which was correlated with a general rise in numbers of micro-organisms, particularly actinomycetes and bacteria, the acidity and volatile nitrogen increased. Later, when fungi and actinomycetes grew profusely, soluble sugars decreased rapidly and the pH value rose to 7.0 or above. Stacks of wet and dry hays were compared with bales made from the same hays. The wet stack developed a core of brown acid hay, containing many spore-forming bacteria but few fungi, surrounded by a layer of mouldy hay.