- Volume 75, Issue 2, 1973

SUMMARY: When 3-O-methyl glucose is actively transported into the fungus Dendryphiella salina metabolizable soluble carbohydrate is converted into polysaccharide and other insoluble material such that the total soluble carbohydrate concentration remains constant. Uptake of 3-O-methyl glucose from 1.0 mM solution is inhibited by equimolar glucose, fructose, mannitol or arabitol and by potassium acetate, both ionic species being involved. The results are discussed in relation to the control of hyphal osmotic pressure.

SUMMARY: The ability of certain lipids to induce polymerization of staphylococcal α-toxin has been investigated using polyacrylamide disc gel electrophoresis in the presence of sodium dodecyl sulphate to monitor conversion of the monomeric form of α-toxin (molecular weight = 36 000) to the α125 aggregate. The widely differing lipids varied in the order diglyceride > lecithin > cholesterol > lysolecithin in polymer-inducing activity. No individual component was as efficient as a mixed dispersion of lecithin, cholesterol and dicetyl phosphate (molar ratio 70:10:20) in inducing polymerization. In general our observations indicate that there is no specific lipid inducer and that the outcome of the interaction between staphylococcal α-toxin and biological membranes probably depends on the location of lipids in the membrane and their distribution in relation to one another. Also the results with diglyceride confirm our earlier suggestion that α-toxin can react hydrophobically with lipids.

SUMMARY: The derepression and localization of the glyoxylate cycle enzymes in Coprinus lagopus (sensu Buller) have been studied. Differential and sucrose density gradient centrifugation of extracts indicated a particulate localization for isocitrate lyase (EC. 4.1.3.1) and malate synthase (EC. 4.1.3.2). The particle is distinct from, and less dense than, the mitochondrion and is considered to be a glyoxysome.

SUMMARY: Polyribosomes and ribosomes were isolated from vegetative Myxococcus xanthus FB and myxospores. The sedimentation coefficients of monoribosomes and ribosomal subunits were the same as those for equivalent particles from Escherichia coli. Conditions for the dissociation of the ribosomes and the unfolding of the subunits (in strong salt or very low concentrations of magnesium salts) differed from those required for analogous processes in E. coli. The stability of the 30 S subunits differed in preparations from vegetative M. xanthus and myxospores. Spermidine promoted the unfolding of the larger (50 S) subunit in low-magnesium buffer.

Proteins were isolated from ribosomal subunits of Myxococcus xanthus, fractionated by polyacrylamide-gel electrophoresis and a catalogue was compiled. The proteins derived from ‘native’ subunits and from subunits partly unfolded in strong salt and from ribosomal subunits derived from vegetative cells and myxospores were compared. A difference in the profile of proteins from the 30 S subunits of myxospores and vegetative cells was found. The significance of these results is discussed in the light of the dissociation properties of the ribosomes and also the morphogenetic cycle of M. xanthus.

SUMMARY: RNA was isolated from vegetative Myxococcus xanthus FB and myxospores. Organisms were labelled with [32P]orthophosphate during encystment and the metabolic stability of the radioactive RNA was followed by fractionating purified RNA from ‘pulse-chased’ cultures by polyacrylamide gel electrophoresis. Much of the label was in heterodisperse (messenger-like) RNA but the stable RNA (present in the mature myxospores) was largely high-molecular weight ribosomal RNA and its precursors.

The role of RNA synthesis in the morphogenetic cycle of Myxococcus xanthus is discussed in the light of these data and of the properties of the ribosomes and ribosomal proteins from this organism.

SUMMARY: On storage, pigmented (orange or yellow) strains of Staphylococcus aureus produce non-pigmented variants which are more susceptible to desiccation and to linoleic acid than are the corresponding wild strains. The association of these properties could explain why most staphylococci isolated from clinical sources are pigmented, although the pigmented character is lost at high frequency in vitro.

The genes determining these properties are not borne by a typical plasmid since the capacity to produce pigment was not transducible, and no covalently closed circular DNA was detected in lysates of three pigmented strains. There was an apparent reduction in cellular DNA of 30 to 40% associated with the loss of these genes; however, DNA/DNA hybridization could not distinguish between total cellular DNA from a pigmented strain (PAR5) and that isolated from the corresponding non-pigmented variant.

SUMMARY: Within the order Mycoplasmatales guanine plus cytosine contents and genome sizes have been determined for 17 strains representing 15 bovine and two ovine species, subspecies or serogroups. The guanine plus cytosine contents were found to vary between 24.4 and 32.9%. The genome sizes were 4.0 to 5.6 × 108 daltons for 14 sterol-requiring strains and 0.99 to 1.1 × 109 daltons for three non-sterol-requiring strains. These results support earlier findings that members of the genus Acholeplasma (family Acholeplasmataceae) have genome sizes about twice those of the genus Mycoplasma (family Mycoplasmataceae).

SUMMARY: After extensive ethidium bromide (EB) treatment or ultraviolet irradiation or petite mutants could be isolated from the obligate aerobe Hansenula wingei. Petite-negativity is correlated with a lack of glucose repression. Hansenula wingei issensitive to EB on fermentable as well as non-fermentable carbon sources. Growth arrest by EB of single cells on agar is immediate but one or two divisions occur in liquid before the sensitive cells stop growing. Although EB treatment of the sensitive wild-type does not result in either petite mutagenesis or cell killing, there is a reversible inhibition of growth observed when EB-treated cells are plated on non-crmentable substrates. Mutants resistant to EB were isolated on either glucose + EB or glycerol + EB plates. Mutants resistant to EB in glycerol medium are also (csistant to EB in glucose medium. However, mutants isolated on glucose + EB medium are still sensitive to EB in glycerol medium. When mutants resistant to EB in glycerol medium revert to sensitivity they retain resistance to EB in glucose medium. Resistance to EB in glucose medium is recessive in the diploid.

SUMMARY: A glycerol-negative respiratory-deficient mutant is described which is not petite as judged by several criteria: (i) it grows slowly on glycerol; (ii) it reverts to glycerol-positive; (iii) it grows slowly on other non-fermentable carbon sources; and (iv) it has a normal cytochrome spectrum. It is not an oxidative phosphorylation mutant because the growth yield on glucose is the same as the parent. This glp mutant is specifically blocked in glycerol respiration but, in addition, is pleiotropic, affecting growth rates on other carbon sources, sporulation and diploid mitotic segregational frequencies of other genes.

SUMMARY: Non-conditional morphological mutant envC derived from Escherichia coli K-12 strain P678, isolated after treatment with 1-methyl-3-nitro-1-nitrosoguanidine, produced chains of bacteria on synthetic or rich media at 30° and 40°. It was sensitive to deoxycholate and less resistant to penicillin and rifampicin than the parent strain. In section under the electron microscope, the mutant showed greatly disorganized septum formation. Preliminary mapping of envC by conjugation located it near xyl. The morphological and physiological characteristics of envC + recombinants and the envC + parent were identical.

SUMMARY: Acinetobacter calcoaceticus, a soil isolate capable of utilizing ethanol as a sole carbon source, was cultivated in a chemostat under ethanol-limiting conditions. The pulse addition of ethanol (to less than 0.1% final concentration) to steady state cultures inhibited growth. Growth inhibition was accompanied by conversion of ethanol to acetate, after which growth resumed on the accumulated acetate and the culture returned to the original steady state. The final concentration of ethanol added and acetate accumulated were lower than levels that inhibited growth in batch culture. The rate of acetate synthesis after the pulse addition of ethanol was sufficient to support the maximum specific growth rate. (μmax) although the growth rate immediately before ethanol addition was only 47% of μmax. In batch culture acetate- or ethanol-grown cells preferentially consumed the acetate component of an ethanol-acetate mixture, but in chemostat cultures the presence of acetate did not prevent ethanol oxidation.