- Volume 132, Issue 10, 1986

SUMMARY: The effects of L-sorbose on the growth and biosynthesis of cellulases and other polysaccharide-degrading enzymes of Trichoderma reesei C-5 were studied. The specific growth rate and yield of this strain in batch culture were reduced by 23% and 46% respectively on addition of 1% (w/v) sorbose to Vogel's medium containing 1% (w/v) glucose. The specific consumption rate of both sorbose and glucose decreased in the presence of the other sugar at 1% (w/v) concentration. The addition of sorbose (1-5%) to cultures grown in 1% glucose resulted in enhanced activities of all cellulase enzymes, and particularly endoglucanase activity, which increased sevenfold in the presence of 5% sorbose. There was no significant effect on the activities of β-glucosidase, acid phosphatase and amylase. While the increased enzyme activities seemed to be correlated with a decreased rate of glucose consumption, a direct effect on some extracellular enzymes could not be ruled out.

SUMMARY: The effects of thioglycerol on growth and aflatoxin production by Aspergillus parasiticus were studied using conidia-initiated cultures and pregrown mycelia. Thioglycerol inhibited both growth and aflatoxin synthesis, with toxin formation being affected to a greater extent. This inhibitory activity could not be overcome by addition of methionine or zinc sulphate. Accompanying respirometric studies suggested that the primary mode of action of thioglycerol involves an inhibition of oxygen utilization.

SUMMARY: Sexual stimulation increases the β-carotene content of the fungus Phycomyces blakesleeanus. The same effect is observed in single cultures exposed to natural and synthetic trisporates and in intersexual heterokaryons. Synthetic racemic (9Z)-methyl trisporate B, a trisporate precursor made by cultures of the (+) mating type, stimulates carotenogenesis only in (-) cultures. Synthetic racemic (9Z)-methyl trisporate C is less effective and the corresponding all-(E) isomers and other related compounds are inactive. Sexual stimulation of carotenogenesis is additive with the stimulations induced by light, retinol, dimethyl phthalate, and mutation of the gene carS.

SUMMARY: Despite the usefulness of the macrocyst cycle for genetic analysis of slime mould cells, a great difficulty has been the extremely poor germination of the macrocysts. We describe culture conditions for reliable, high-frequency macrocyst germination, using Dictyostelium mucoroides 7 (Dm7) and a mutant MF1 derived from it. Irradiation with relatively short-wavelength light (blue-near-UV) was particularly important for the induction of germination, and only a short period of irradiation was required to obtain a high percentage of germination. There was a critical temperature between 19 and 22 °C for efficient induction of germination; a relatively high pH, around 8.0, also favoured germination. Germination competence increased with the age of the macrocysts.

SUMMARY: The degradation of sinapic acid, a monomer of hardwood lignins, by the yeast Rhodotorula glutinis was studied. Syringic acid, 3-O-methyl gallic acid, gallic acid and 2,6-dimethoxy-1,4-benzoquinone were identified as degradation products. Glucose was shown to be required for the demethylation of the methoxy groups on the ring. Unlike in the bacterium Pseudomonas putida, ring cleavage seemed to occur via gallic acid and not via methyl gallic acid. Cell-free oxidative decarboxylase (hydroxylase) activity was detected; this enzyme might be ultimately responsible for the formation of dimethoxyquinone.

SUMMARY: A dikaryon of the basidiomycete Schizophyllum commune growing in surface culture at 30 °C in the dark produced extracellular laccase (EC 1.10.3.2). Little extracellular laccase was formed in the light or at 24 °C. The co-isogenic monokaryons from which the dikaryon was generated generally failed to produce laccase. The activity in the medium of the dikaryon accumulated until the glucose was consumed and then declined steadily. At its peak level of activity the enzyme accounted for about 3% of the extracellular protein. The enzyme was purified by DEAE-Sephacel chromatography. Substrate specificity and inhibitor studies showed the enzyme to be a typical fungal laccase. Electrophoresis of a purified enzyme preparation showed one major band accounting for 98% of the laccase proteins, and two minor bands with laccase activity. The major laccase protein was used to raise specific antibodies. After denaturation of the major laccase two immuno-reactive protein forms of M r 64 x 103 and 62 x 103 were produced, the former being convertible into the latter form. The intracellular extract contained one immuno-reactive protein of M r 72 x 103. The presence of laccase protein in the medium of various cultures was detected using Western blots. Accumulation of extracellular laccase protein only occurred in the dikaryon at 30 °C in the dark while the subsequent decrease in activity was not accompanied by a decrease in laccase protein.

SUMMARY: The dichloromethane dehalogenases of four facultative methylotrophs that mineralize dichloromethane were compared. Similar levels of specific activity and a similar subunit M r of the dehalogenases were observed in crude extracts of the four strains. Immunodiffusion analysis and quantitative immunoprecipitation indicated that the dehalogenases closely resemble each other. This was confirmed when the N-terminal amino acid sequences of the four dichloromethane dehalogenases were found to be identical. Some variation was observed with respect to the specificity of the inducers for dichloromethane dehalogenase. In the two Hyphomicrobium strains examined 1,1-dichloroethane and 1,2-dichloroethane were effective gratuitous inducers whereas these compounds exhibited only a marginal inducing effect in the two Pseudomonas strains. The results of this comparative study are compatible with the view that dichloromethane dehalogenase represents a recently evolved enzyme which was horizontally distributed by gene transfer.

SUMMARY: A numerical taxonomic analysis was performed to evaluate the appropriateness of a single biovar designation (biovar V) for all Pseudomonas fluorescens isolates negative for denitrification, levan production and phenazine pigmentation and to determine the relationship of biovar V strains to other taxa within the same Pseudomonas RNA homology group. Seventy-two strains assigned to P. fluorescens biovar V and four strains of P. fragi were characterized and the data subjected to a numerical taxonomic analysis along with comparable data for 17 previously characterized strains of this biovar and 89 P. putida strains. Seven distinct biovar V clusters containing three or more strains were revealed, and the carbon sources useful for their differentiation were identified. Cluster 1 (38 strains) closely resembled two atypical P. fluorescens I strains. It was also related to P. fluorescens biovar IV and to P. fragi. Cluster 2 (5 strains) was related to cluster 1. Cluster 3 (7 strains) was identical to a major group of meat spoilage psychrotrophic pseudomonads (P. lundensis). Cluster 4 (3 strains) was not related to any other group examined. Cluster 5 consisted of six isolates initially designated P. putida A along with four P. fluorescens biovar V strains all of which resembled P. putida more than they resembled the other P. fluorescens groups. Cluster 6 (16 strains) was distinct from the other biovar V clusters, but was closely related to P. fluorescens biovars I and II. Cluster 7 (3 strains) shared many characteristics with cluster 5. Separate P. fluorescens biovar designations are proposed for cluster 6 and for the combined clusters 1 and 2. A new P. putida biovar is proposed for the combined clusters 5 and 7.

SUMMARY: Seventy-four Flavobacterium strains were characterized by gas-liquid chromatographic analysis of volatile fatty acids produced in the culture medium. Principal components analysis permitted the graphic representation of the relative positions of the different strains, and aggregation according to the variance enabled a hierarchical classification to be established. The study revealed three subgroups each for F. meningosepticum and F. odoratum. Our F. breve, Flavobacterium sp. group IIb and F. multivorum strains appeared to be homogeneous. These results tallied with those of previous studies on DNA base composition and reassociation, electrophoretic protein profiles and cellular fatty acid composition.

SUMMARY: Strain EPS-5028 is a free-living bacterium which contains R-bodies. By its morphology, biochemical characteristics and G + C content, strain EPS-5028 differs from the other known free-living R-body-containing bacteria, Pseudomonas avenae and Pseudomonas taeniospiralis. Phage and particles resembling phage heads were observed in cells induced with UV irradiation.

SUMMARY: Vibrio anguillarum strain 775 harbouring the virulence plasmid pJM1 produces a plasmid-mediated siderophore that can crossfeed siderophore-deficient, receptor-proficient mutants of V. anguillarum in vitro. Experimental infections of salmonid fishes with mixtures consisting of the wild-type strain and a siderophore-deficient, receptor-proficient mutant resulted in recovery of both the wild-type and the mutant strain, while in infections with mixtures consisting of the wild-type strain and a siderophore-deficient, receptor-deficient mutant only the wild-type strain could be recovered. These results suggest that the V. anguillarum plasmid-mediated siderophore is produced in vivo in a diffusible form and that it is an important factor of virulence.