- Volume 95, Issue 1, 1976

SUMMARY: A streptomycete strain (ferm-p1185), isolated from soil, secreted a slime on glucose-asparagine agar, and produced viscous growth in liquid media containing peptone as nitrogen source. A purified polysaccharide isolated from the culture broth was composed of glucose and mannose units (molar ratio 1.87:1). Periodate oxidation, Smith degradation, methylation analysis, infrared and 13C nuclear magnetic resonance spectra, indicated that this manhoglucan had a linear structure consisting of α-1,3- and α-1,4-linked glucopyranose and mannopyranose units.

SUMMARY: Aspergillus ornatus produces conidia when grown in continuous light but few, if any, when grown in continuous darkness. A minimum of 3 h of exposure to light is needed for induction. Light inhibits growth, glucose uptake and phosphorylation but does not inhibit the uptake of lysine. A low molecular weight substance produced or accumulating in the light inhibits the phosphorylation of glucose. It is suggested that the inhibition of glucose uptake and phosphorylation precedes conidiation and that conidiation may be the result of starvation caused by this light-induced inhibition.

SUMMARY: Butyricin 7423 is a trypsin-sensitive bacteriocin produced by Clostridium butyricum ncib7423 and active against some other species of Clostridium. It has a bactericidal but non-lytic action on growing cultures of Clostridium pasteurianum. The primary action of butyricin 7423 appears to be at the cell membrane. Thus treatment of C. pasteurianum with an excess of butyricin altered the permeability of its cell membrane, allowing the release of several metabolites and ions. Efflux of rubidium ions from organisms preloaded with 86Rb+ was particularly rapid and extensive. The action of butyricin 7423 on Clostridium species seems to differ from that of other clostridocins, such as the boticins and perfringocin 28, and more closely resembles the mode of action on susceptible (aerobic) organisms of bacteriocins such as staphylococcin 1580 or colicins A, E1, I and K.

SUMMARY: The activities of l-threonine dehydrogenase (I), 2-amino-3-oxybutyrate: CoA ligase (II), malate synthetase (III), isocitrate lyase (IV), glyoxylate dehydrogenase (V), glycine decarboxylase (VI), l-serine hydroxymethyltransferase (VII), glucan synthetase (VIII), glucose 6-phosphate dehydrogenase (IX) and succinic dehydrogenase (X) were detected in cell-free extracts prepared from the mycelium of the fungus Sclerotium rolfsii type R. Transfer of S. rolfsii to a threonine-containing medium resulted in a significant increase in the intracellular concentrations of l-threonine, glycine, serine and glyoxylate, and a decrease in oxalate. Incubation with 14C-labelled l-threonine resulted in an immediate output of 14CO2, and an accumulation of labelled glycine and serine in the mycelium. l-Threonine (10−2 m) increased branching, favoured formation of sclerotia, and induced the formation of enzymes I to VIII, but not IX and X. Sodium oxalate (1·5 × 10−2 m) inhibited branching, sclerotium formation and the activity of enzymes III and IV. Glycine (10−1 m) inhibited branching, sclerotium formation and activity of I and II. Ammonium chloride (10−1 to 10−2 m) inhibited formation of sclerotia, threonine uptake and activity of III. Acetyl-CoA inhibited V and l-cysteine inhibited I as well as sclerotium formation and branching. It is suggested that hyphal morphogenesis and formation of sclerotia in S. rolfsii require an increased supply of carbohydrate intermediates and energy and that these are mainly supplied by the glyoxylate pathway.

SUMMARY: The malate synthase activity detectable in crude extracts of Pseudomonas AM1 has been shown to be due to a coupling of a malyl-CoA hydrolase with malyl-CoA lyase and not due to a discrete malate synthase enzyme. The partial purification of this malyl-CoA hydrolase from Pseudomonas AM1 has shown that it is distinct from citrate synthase which also hydrolyses malyl-CoA. The malyl-CoA hydrolase has a low K m for malyl-GoA (7·0 μM). A mutant of Pseudomonas AM1, ICT51 ( Taylor & Anthony, 1975 ), which is unable to grow on ethanol, malonate or 3-hydroxybutyrate, has been shown to have an altered malyl-CoA hydrolase with a K m for malyl-CoA 30 times higher than that of the enzyme present in the wildtype organism. Two classes of revertants to growth on these substrates have been isolated: (i) those with a malyl-CoA hydrolase of similar K m to the wild-type and (ii) those in which the malyl-CoA hydrolase activity remains the same as in the mutant ICT51. The nature of the mutation leading to the latter class of revertants is unknown.

SUMMARY: In Pseudomonas ami, conversion of 3-hydroxybutyrate to acetyl-CoA is mediated by an inducible 3-hydroxybutyrate dehydrogenase, an acetoacetate: succinate coenzyme A transferase (specific for succinyl-CoA) and an inducible β-ketothiolase. Ethanol is oxidized to acetate by the same enzymes as are involved in methanol oxidation to formate. An inducible acetyl-CoA synthetase has been partially purified and characterized; it is essential for growth only on ethanol, malonate and acetate plus glyoxylate, as shown by the growth characteristics of a mutant (ict54) lacking this enzyme. Free acetate is not involved in the assimilation of acetyl-CoA, and hydroxypyruvate reductase is not involved in the oxidation of acetyl-CoA to glyoxylate during growth on 3-hydroxybutyrate. A mutant (ict51), lacking malate synthase activity, has been isolated and its characteristics indicate that this activity is normally essential for growth of Pseudomonas ami on ethanol, malonate and 3-hydroxybutyrate, but not for growth on other substrates such as pyruvate, succinate and C1 compounds. The growth properties of a revertant ( ict51r) and of a mutant lacking malyl-CoA lyase (pct57) indicate that an alternative route must exist for assimilation of compounds metabolized exclusively by way of acetyl-CoA.

SUMMARY: Escherichia coli strain SPA o converts methionine to ethylene by an inducible enzyme system. l-Cysteine, l-homocysteine, methionine derivatives and the sulphur-containing analogues of l-methionine also act as precursors of ethylene. Ethylene is produced by cell suspensions only in the presence of air; cell-free preparations can produce ethylene aerobically and anaerobically, but the extent to which they do so depends on the mode of culture growth. Light stimulates ethylene production by cell suspensions and its presence is essential for production by cell-free preparations. The kinetics of ethylene biogenesis and its pH and temperature optima suggest that ethylene is a secondary metabolite.

SUMMARY: Rothia dentocariosa was seen as a typical prokaryotic cell, lacking nuclear envelope, mitochondria and a reticulum with ribosomes. The plasma membrane was located close to and parallel to the wall. The outer limits of the wall were associated with what may be capsular or slime material. Chain-like filaments of thick-walled coccoid cells underwent septation both transverse and parallel to the long axis of the chain. Side branching and terminal clavate forms were also present. These clavate forms may represent specialized cells during the life-cycle. Fragmentation of the chain resulted when the outer wall ruptured to release the coccoid bodies.

SUMMARY: Strain Bali 1 of Allomyces arbuscula is infected with a RNA virus; strain North Carolina is not. The virus appears to be avirulent, for strain Bali 1 showed no signs of pathogenicity. Virus aggregates occurred mostly in the cytoplasm during different stages of the gametophytic and sporophytic generations. Small intranuclear aggregates were found only in differentiating gametophytic hyphae and immature gametangia. In motile cells (gametes and zoospores) the aggregates are exclusively contained within the nuclear cap. This represents a reliable mechanism of transmission throughout the life-cycle.

SUMMARY: The antibiotic whose biosynthesis is determined by the SCP1 plasmid of Streptomyces coelicolor A3(2) has been characterized as the recently described methylenomycin A (2-methylene-cyclopentan-3-one-4, 5-epoxy-4, 5-dimethyl-1-carboxylic acid).

SUMMARY: SCP1′-cysB carries a short chromosomal insertion: cysB was the only chromosomal locus identified on this plasmid; the plasmid was seldom lost; and a comparatively low frequency of crossing-over occurred between the exo- and endogenote in a cysB +/cysB heterozygote. SCP1′-argA, uraB carries a longer chromosomal insertion: five chromosomal loci have been detected on the plasmid; it was very often lost; and there was frequent crossing-over between exo- and endogenote in heterozygous strains.

Both SCP1 plasmids gave rise to plasmids closely resembling, or perhaps identical with, the original SCP1 by deletion of the chromosomal insertion. Markers argA and uraB were always deleted together from SCP1′-argA, uraB, whereas random deletion should more often have removed uraB alone. This suggests that special DNA sequences are involved in SCP1′ formation.

An analysis of recombination between exo- and endogenote within a double heterozygote for argA and uraB supports the hypothesis that single copies of plasmid and chromosome assort from a pool of interacting molecules at, or immediately before, spore formation.

A strain carrying the SCP1′-cysB plasmid gave rise to a ‘bidirectional’ donor of chromosomal markers in which the plasmid had apparently integrated into the chromosome at or close to the cysB locus.

SUMMARY: As the result of P1-mediated cotransduction with serB from Salmonella potsdam to the Escherichia coli/Salmonella typhimurium hybrid 4617, one recombinant, l4004, was isolated which had a restriction-modification (R-M) system different from the SB and SP systems of its parents, and was designated SQ. The genes of SQ were allelic to those of the SB system of S. typhimurium and were shown by complementation experiments to be functionally related to those of the K system of E. coli. Evidence that the SQ system in l4004 arose as the result of a recombination event within the hsdS genes of SB and SP is discussed.

SUMMARY: Amoebae of the true slime mould Physarum polycephalum were cultured in two fully-defined liquid media containing amino acids, glucose, three vitamins and a buffered salts solution. Absolute requirements were demonstrated for methionine, haematin, thiamine and biotin, all of which were known to be specific requirements of the plasmodial stage. Methods are described for large-scale culture in three semi-defined media.