- Volume 55, Issue 2, 1969

SUMMARY: L-forms of Serratia marcescens were produced and serially transferred in osmotically stabilized agar with penicillin. The bacterial form was pigmented, while the L-form colony was not. Lack of colour in the L-form colony was not due to pigment diffusion into the agar; an extract of agar with L-form growth did not show an absorption spectrum for prodigiosin.

SUMMARY: Growth of a strain of Saccharomyces cerevisiae in an inositol-deficient chemically defined medium resulted in marked changes in the composition of the cell wall. Organisms grown in the complete absence of inositol possessed a weakened cell wall which contained more glucan and hexosamine but less mannan, phosphorus and protein than normal walls. The amino acid contents of the two types of cell wall were quite different but no significant change occurred in either the amount or the fatty acid composition of cell wall lipid. Treatment with ethylenediamine facilitated the isolation of three fractions, A, B, and C from normal and from deficient cell walls. The mannan and protein content of fractions A were strikingly similar. Deficient fractions B and C however contained considerably less mannan and protein but more glucan and hexosamine than the corresponding normal fractions.

Summary: The occurrence of multivesicular bodies (m.v. bodies) in Sclerotinia fructi-gena, both in vivo and in vitro, was studied by electron microscopy. This investigation was an attempt to correlate the existence of m.v. bodies with extracellular enzyme production. It was observed that when the fungus grew in its natural hosts or in media containing pectin or sodium pectate, where extracellular pectolytic enzyme secretion was high, m.v. bodies were present in the hyphae. However, when the fungus grew in synthetic media without pectin or sodium pectate, these m.v. bodies were absent, and the extracellular enzyme activity was very low. Multivesicular bodies in S.fructigena seemed to originate from the endoplasmic reticulum, moving later to the periphery of the cell.

A new histochemical technique was used at the electron microscope level; this provided supporting evidence that m.v. bodies are the cytoplasmic constituents involved in extracellular enzyme secretion by this fungus.

SUMMARY Streptococcus lactis was grown in media containing various concentrations of benzylpenicillin; 0·05 μg./ml. was without effect and 0·40 μg./ml. inhibited growth. Intermediate concentrations in increasing steps of 0·05 μg./ml. were investigated. The Gram-positive cocci tended to become Gram-negative rods, the most effective concentration of penicillin for this effect was 0·15 ± 0·05 μg./ml. The rod forms frequently had surface vesicles which appeared to be membrane-bounded but were osmotically stable; the dry wt yield/ml. medium was diminished. Such forms contained up to 10 times more nisin/unit dry wt than the control. At penicillin 0·20 to 0·25 μg./ml. growth was followed by lysis which was followed by new growth after a long delay; morphologically these forms resembled the controls and the dry wt yield increased. Higher concentrations of penicillin (0·35 μg./ml.) decreased the dry wt yield/ml. medium and growth appeared only after a delay of 16 hr. Morphologically these forms tended to elongate again and the cell nisin/unit dry wt was 8 times higher than the control. Single-colony isolates obtained from the higher penicillin concentrations were grown in penicillin-free medium and when again challenged with penicillin no longer formed rods at 0·15 μg./ml. This more penicillin-resistant population occurred at a frequency of 1 :500 of the parent population and was distinguished from it by a number of physiological properties. These results suggest that penicillin acted by selecting resistant individuals already present in the parent population.

SUMMARY: Reversions to wild type occurred when conidia of a number of biochemically deficient mutants of Aspergillus niger were treated with DNA from the wild-type strain. No reversions or wild-type colonies were obtained when an equivalent number of conidia from deficient strains were either treated with the same DNA as the recipient, or were plated without any DNA treatment. Increase in the percentage of transformation was observed up to 6 μg./ml. of donor DNA. The transforming activity of the donor DNA was found to be inhibited by the action of u.v. radiation, heat and DNase. The frequency of transformation was low which could be attributed to the method of extraction of DNA which involved crushing of cells in the presence of alumina, possibly breaking the DNA into small fragments thus making it biologically less active.

SUMMARY: The thermal stability of interspecies DNA duplexes is markedly increased by raising the incubation temperature. When the DNA reassociation reactions are carried out at 75° in 0·12 m-phosphate buffer the thermal denaturation temperature of the reassociated product is almost identical to that of the native DNA, indicating that only DNA segments of very similar nucleotide sequence are associating. The genus Neisseria very clearly forms three groups based on the relatedness of their DNA to that of N. meningitidis; the ‘pathogenic’ Neisseria which have at least 80 % of their nucleotide sequences similar; the ‘non-pathogenic’ Neisseria which share only 8 to 15 %; and N. catarrhalis which shows no relatedness.

SUMMARY: The mode of action of actinonin, a pseudo-peptide antibiotic has been investigated. When added to cultures of Bacillus subtilis 7198 and 3610 actinonin inhibits growth. Evidence is presented which shows that this inhibition of growth reflects a bacteriostatic rather than bactericidal effect and that the site of action of the antibiotic is associated with RNA synthesis.

SUMMARY: When the growth of surface cultures of Mycobacterium phlei was limited by nitrogen or sulphur, the organisms synthesized both glycogen and lipid as endogenous reserves. Equal weights of glycogen and lipid accumulated intracellularly which, combined, may account for 50 % of the cell dry weight. Both storage materials also accumulated when growth was inhibited by chloramphenicol or p-fluorophenylalanine in otherwise nutritionally adequate media. In the absence of exogenous carbon substrate, the glycogen and lipid reserves were utilized as energy and carbon for nitrogen incorporation and continued growth. Evidence is presented which suggests that glycogen may be the preferred endogenous reserve in M. phlei.

SUMMARY: Three heterotrophic marine bacteria, isolated from the Tyrrhenian sea on the basis of their relative growth requirements for acetate and ammonium, were studied mainly in regard to their biochemical and nutritional characters. Data about the amino acid pools, protein amino acids, CO2: O2 ratios, enzyme activities and sensitivities to metal ions and antibiotics, are reported. The utility of an index obtained from the study of the oxygen uptake with various organic-C concentrations and the use of defined media for a more satisfactory discrimination of the various strains, is shown.

SUMMARY: Capitella of Mycotypha africana and M. microspora regularly produce sterigmata of two lengths. Spores of M. africana are dimorphic and this is probably also the case in M. microspora. A membrane which separates from the spore, particularly on germination, is interpreted as evidence that the spore of M. africana is a sporangiole and it is suggested that the genus Mycotypha should probably be classified in Thamnidiaceae.

SUMMARY: Halobacterium strains produce a truly extracellular proteinase which degrades gelatine and casein. It has a pH optimum of about 8 and depends upon divalent cations and a high concentration of NaCl or KCl for activity and stability. Proteolytic enzymes were also found in cell homogenates obtained by ultra sonic treatment. A caseinolytic enzyme, probably different from the extracellular one, is associated with particles which sediment upon ultracentrifugation. A soluble peptidase of lower molecular weight is also present in the extract. Both enzymes are dependent upon divalent cations and a high concentration of NaCl or KCl for activity. In contrast to other halophilic enzymes, the proteolytic enzymes of Halobacterium salinarium are more active in the presence of NaCl than KCl at equimolar concentrations.

SUMMARY: During utilization of [14C]acetate by non-photosynthetic Euglena gracilis var. bacillaris, 14C was regularly found in trehalose, phosphate esters, glutamate, malate, fumarate, succinate, aspartate, alanine, γ-aminobutyrate, and six unidentified ethanol-soluble compounds. Of the unidentified substances only two, an anthrone-positive material and an ether-soluble substance, were quantitatively important. Small amounts of radioactive laminaribiose, lamin-aritriose, and what were probably higher oligosaccharides of the laminarin series were found by a more sensitive procedure, as well as several additional labelled ninhydrin-positive substances. The kinetics of labelling were consistent with oxidation of acetate via the tricarboxylic acid cycle and assimilation via the glyoxylate cycle and ‘reversed’ glycolysis. There was no indication of any qualitative difference between the intermediates of acetate metabolism and those of oxidation of endogenous reserves. Rapid fluctuations in levels of labelled intermediates were observed, some of which coincided with shoulders or plateaux in the radioactivity of the ethanol-soluble fraction as a whole.

SUMMARY: In an effort to understand the mechanisms controlling germ-tube differentiation in Peronospora tabacina the biochemical events occurring early in germination have been investigated Actidione [2 × 10−6 m] inhibited germination, indicating that differentiation required the synthesis of new protein. However, not all the protein synthesized prior to emergence was essential; only the protein synthesized within 30 min. of the start of germination appeared to be necessary. Inhibitors of RNA synthesis prevented the incorporation of [3H]uridine into RNA, yet had no effect on germination, indicating that differentiation did not require the synthesis of RNA. It is concluded that the protein required for differentiation is synthesized on a stable template of messenger RNA present within the dormant conidium.

SUMMARY: Bacillus cereus strain 569H became resistant to tetracyclines, arsenite and cyanide. The degree of resistance acquired was independent of the inducing concentration up to 2 × 10−5 m. Recovery from tetracycline and arsenite inhibition involved a change in the bacteria themselves; cyanide resistance involved also the destruction of this inhibitory agent. Although there were many similarities between the tetracycline and arsenite recoveries, two distinct mechanisms were involved. Adaptation to tetracycline was not observed with B. megaterium, Pseudomonas aeruginosa or Escherichia coli. Bacillus megaterium and E. coli did adapt to cyanide. Although polymyxin B was inactive by itself against B. cereus, lytic activity due to the antibiotic was seen when a tetracycline was also present in the medium. The lytic activity ceased when the bacilli recovered from tetracycline. Bacillus cereus did not adapt to other inhibitors of protein synthesis, RNA synthesis or oxidative phosphorylation.

Summary: A heterotrophic bacterium has been isolated which can use thiocyanate as its sole source of cellular nitrogen and also sulphur; ammonium ions inhibit the utilization of thiocyanate. It can utilize both phenol and thiocyanate simultaneously; it is a pseudomonad and is most similar to Pseudomonas stutzeri.

Summary: Diploid conidiospores of Aspergillus nidulans are uninucleate and have twice the volume of haploid conidiospores. On the other hand, the hyphae are coenocytic, and it has been found that the dimensions of the hyphal cell are unaffected by ploidy but that diploid cells have half as many nuclei as haploid ones. It is concluded from this that both cessation of growth in cells of fixed size and the timing of mitoses in coencytes are determined by a critical volume of cytoplasm per genome, rather than per nucleus.

In the conidial apparatus, the dimensions of the coenocytic conidiophore, like the hyphae, are unaffected by ploidy, while the uninucleate sterigmata are larger in the diploid. In the case of the primary sterigmata, however, the volume in the diploid is less than twice that in the haploid, suggesting that the mechanism controlling cytoplasmic volume is not fully operative at this stage.

Summary: Proline suppressor mutant su-19 was analysed for arginase and ornithine δ-transaminase (OTA) activity. Both enzymes are constitutively produced by this mutant. Five other suppressor loci not linked with su-19 or to each other are involved in regulation of the two enzymes.

A mutant showing no OTA activity was isolated. Properties of this mutant and its effect in various strains of the pro su type were studied.

SUMMARY: Phage N6 lysates of Micrococcus lysodeikticus and Sarcina lutea were very viscous and were found to mediate genetic transfer of an adenine marker (ade+) to adenine-dependent strains of M. lysodeikticus. The transfer activity of these lysates was found to reside in a high molecular weight DNA fraction rather than in the phage particles themselves. DNA that was isolated and purified from phage lysates and lysozyme-treated cells was shown to possess transforming activity. Recipient competence was maximal during late logarithmic growth (14–18 hr). The cell density of the transfer suspension was optimum at about 107 colony forming units/ml. Transformants were recovered after 1 hr exposure to DNA and continued to increase in number up to 6 hr. Transformants appeared in higher frequencies on Difco agars that were less purified. Under optimal conditions, transformation frequencies up to several percent per colony forming unit were obtained. All strains of M. lysodeikticus tested (atcc 4698, atcc 15801, ccm 1335, pu, um, wru, isu) could serve as donors of the ade+ marker. All strains, except atcc 4698, were competent recipients of the adenine marker.