- Volume 90, Issue 1, 1975

SUMMARY: Synthesis of the Pseudomonas aeruginosa aliphatic amidase was repressed severely by succinate and malate and less severely by glucose, acetate or lactate. Amidase synthesis in inducible and constitutive strains was stimulated by cyclic AMP, which also gave partial relief to catabolite repression produced by the addition of lactate to cultures growing in pyruvate medium. Mutants which were resistant to catabolite repression were isolated from succinate + lactamide medium.

SUMMARY: Five strictly anaerobic bacteria able to hydrogenate unsaturated fatty acids were isolated from sheep rumen. One was characterized as Ruminococcus albus, two as Eubacterium spp. and two as Fusocillus spp., one of which is named as a new species. The Fusocillus organisms were able to hydrogenate oleic acid and linoleic acid to stearic acid, and linolenic acid to cis -octadec-15-enoic acid. The R. albus and the two Eubacteria did not hydrogenate oleic acid but converted linoleic and linolenic acids to a mixture of octadecenoic acids; trans-octadec-11-enoic acid predominated but several isomeric cis and trans octadecenoic acids were produced together with isomers of non-conjugated octadecadienoic acids.

The intermediate and final products of hydrogenation by each organism were compatible with the results from mixed rumen bacteria.

SUMMARY: The polysaccharide, elaborated in trachoma-inclusion conjunctivitis (TRIC) agent inclusions, was isolated from baby hamster kidney (BHK) cells grown and infected in suspension cultures. It was characterized by physical, chemical and enzymic methods as a glycogen with an average chain length of 14 to 16 glucose units.

SUMMARY: A mutant, dai, has been isolated from the Escherichia coli k12, strain k2.1 t, as a colony resistant to 2-deoxyglucose (DG) when growing on fructose but still sensitive to DG when growing on other sugars. The mutation in dai specifically affects the catabolite inhibition of fructose utilization by glucose and glucose-6-phosphate; the affected gene (designated cif) is located at min 41 on the E. coli linkage map and is highly co-transducible with the genes that specify the uptake of fructose (ptsF) and enzvmic conversion of fructose-1-phosphate to fructose-1,6-bisphosphate (fpk).

SUMMARY: The spore of Cunninghamella echinulata is contained inside a monosporic sporangiolum. The spore wall consists of two layers: an outer thin electron-dense layer and an inner thick electron-transparent layer. The inner layer appears fibrillar. During spore germination a localized area of new wall material is formed beneath the existing spore wall at the site where germ-tube formation will occur. This new wall pushes out through the spore and sporangiolar walls and forms the wall of the germ tube.

The germination of spores of fungi as a group is discussed. At present no taxonomic significance can be attached to the mode of germination.

SUMMARY: Suppression of germination of conidia of Cochliobolus victoriae was similar during incubation on sand being leached with water and on sand leached with salt solutions. Conidia of C. victoriae, Thielaviopsis basicola and Curvularia lunata, and sclerotia of Sclerotium cepivorum, exuded more 14C label during leaching with phosphate buffer than on buffer-saturated sand without leaching. Conidia of C. victoriae and Cochliobolus sativus became dependent upon exogenous nutrients after 7 days’ incubation on soil or leached sand. Decreased viability followed the loss of nutrient independence. Germination of C. victoriae and Cu. lunata was stimulated when they were leached with exudate from spores of either fungus, or by a dilute nutrient solution simulating natural exudate. Conidia rendered nutrient-dependent by leaching, germinated and accumulated radioactivity when incubated on exudate from 14C-labelled spores. Nutrient-independent spores exude non-specific energy-rich nutrients which may be rendered unavailable to the spores by microbial activity in soil, resulting in fungistasis.

SUMMARY: Sensitivity of conidia of Cochliobolus victoriae to fungistasis decreased markedly following incubation on moist sand for at least 1 h. Germination was greater on Conover loam or on sand being leached with water than on an alkaline clay loam soil known to produce a volatile fungistatic substance. Evolution of 14CO2 began within 3 min after [14C]glucose was applied to the soils; the rate of 14CO2 evolution was faster with Conover loam. Germinationot Thielaviopsis basicola conidia per unit of glucose remaining in agar discs initially containing 0·1% glucose, was lower for discs incubated on the clay loam soil than on Conover loam, and was greatest on a bed of sand undergoing aqueous leaching. Germination of ascospores of Neurospora tetrasperma and conidia of C. victoriae was suppressed on discs of washed, Purified Agar or polyacrylamide gel incubated on or over the clay loam soil, but no suppression resulted when discs were incubated on Conover loam. Extensive aeration of either soil did not remove its fungistatic effect. Fungistasis in Conover loam appears to be caused primarily by nutrient deprivation, whereas volatile fungistatic substances may play a major role in the clay loam soil.

Summary: The concentrations of free amino acids, particularly alanine, altered as stromata developed on germinating sclerotia. Lipid reserves in the sclerotium provided the principal carbon and energy source, and the nutrients required for stromatal growth appeared to be provided by the sclerotial tissues immediately beneath the point of attachment of the stroma. Alkaloid did not disappear from the sclerotia during germination. Very high levels of polyol, particularly mannitol, were attained in the stromata as germination progressed; the synthesis of polyol was usually accompanied by that of soluble sugars, notably glucose. In an attempt to ascertain the role of mannitol in germination, the relationship between polyol and soluble sugars was investigated in excised stromata after their submergence in buffered media containing a variety of soluble carbohydrates. Mannitol was synthesized under these conditions by way of phosphorylated intermediates, and chiefly in the capitulum, after rapid, and probably passive, absorption of the exogenously supplied sugar. The tissues equilibrated rapidly with the supplied carbohydrate, whose concentration was maintained by further uptake whilst mannitol was being synthesized. The concentrations of assimilated glucose and synthesized mannitol tended toward the same value during incubation and the results suggested that the synthesis was compartmentalized within the stromata. Very little exogenously supplied mannitol was assimilated.

SUMMARY: Protein synthesis by both laboratory-grown bacteria and isolated nodule bacteroids of Rhizobium lupini (strain wu8) is inhibited by d-threo-chloramphenicol, the bacteroid form being the more sensitive to the antibiotic. A comparison between the two forms of the uptake of [14C]chloramphenicol showed that the bacteria always attained a lower intracellular chloramphenicol concentration. It is proposed that the sensitivity difference is due to a difference in membrane permeability between the two forms.

SUMMARY: The effects of induction synchrony by 2′-deoxyadenosine and the ionophore A23187 were compared with selection synchrony methods in Kluyveromyces fragilis. 2′-Deoxyadenosine synchronizes nuclear division and this is followed by synchronous cell division, but DNA synthesis is not synchronized. The ionophore A23187 also induces synchronous nuclear division and synchronous cell division, but likewise does not synchronize DNA synthesis.

SUMMARY: The percentage of bacterial carbon that was derived from exogenous labelled compounds present in the medium during the growth of some methylotrophs on trimethylamine or on non-C1 compounds was determined. Less than 10% of bacterial carbon was derived from acetate during the growth of the obligate methylotrophs 4b6 and c2a1, and of the restricted facultative methylotroph pm6; the other restricted facultative methylotroph W3A1 gave a value of 18%. Corresponding values for three typical facultative methylotrophs growing on trimethylamine were 41. 42 and 52%. Aspartate, fructose, pyruvate and succinate made only a small percentage contribution (0.4 to 12%) to bacterial carbon in 4b6, c2a1, W3AI and pm6. Washed suspensions of 4b6, c2a1, w3a1 and pm6, all grown on trimethylamine, assimilated labelled acetate only in the presence of trimethylamine and there was a linear relationship between the amount of acetate assimilated and the amount of trimethylamine oxidized. Organisms 4b6, c2a1, w3a1 and pm6 assimilated 14C from labelled acetate predominantly into lipid (except pm6), glutamate, arginine, proline and leucine, whereas the typical facultative methylotrophs assimilated 14C from acetate into lipid, nucleic acid and all the protein amino acids. These results are consistent with the presence of a deficient tricarboxylic acid cycle in the obligate methylotrophs and in the restricted facultative methylotrophs.