- Volume 132, Issue 1, 1986

SUMMARY: Botulinum C2 toxin (C2T) is composed of two dissimilar protein components, designated components I and II, which are linked with neither covalent nor noncovalent bonds. The heterogeneity of these two components of C2T produced by Clostridium botulinum type C and D strains was examined. Of 21 strains examined, 19 strains produced the two components, while the others produced neither component I nor component II. The 19 producers of C2T could be divided into three groups based on the differences in antigenicity, molecular weight and biological activity of components I and II. The results provide evidence of heterogeneity in the molecular structure of the two components of C2T, which is possibly a cause of the differences in the biological activity of the toxin observed in different strains.

SUMMARY: Various β-lactam antibiotics, including monocyclic β-lactams, induced the β-lactamase of Proteus vulgaris: when clinical isolates were induced by benzylpenicillin, each strain produced a single β-lactamase but the activity per milligram dry weight differed from strain to strain. The β-lactamases of the P. vulgaris strains were heterogeneous with respect to their isoelectric points, but had almost the same specific activities, substrate specificities and Michaelis constants. The kinetics of β-lactamase formation were investigated in three strains, each with a different β-lactamase activity. Differential rates of enzyme synthesis and peak activity depended on the concentration of inducer. The plots of the reciprocals of the differential rates versus the reciprocals of the inducer concentrations were linear, and the maximum rate of enzyme synthesis and the concentration of the inducer giving half-maximum induction were determined from this double reciprocal plot. The maximum rates of enzyme synthesis were different in the three strains. The kinetic analysis of β-lactamase formation revealed that the β-lactamase activities in a single bacterial species were determined by differences in the rate of enzyme synthesis and not by differences in the properties of the enzyme.

SUMMARY: Wood blocks colonized by the basidiomycetes Hypholoma fasciculare and Phanerochaete velutina were placed in plastic trays containing moist unsterilized soil. Both fungi grew out radially from the inoculum blocks in the form of networks of mycelial cords. When a second, uncolonized wood block, or set of wood blocks, was provided as a ‘bait’ about 5 cm from the inoculum block, marked changes in the form and growth characteristics of the mycelial network followed contact with the bait. These changes were influenced by the relative size of inoculum and bait and included inhibition of radial extension from the inoculum; stimulation of development of connective mycelium; directed growth responses to the bait; fan-shaped outgrowth with conserved polarity from the bait; eventual regression of non-connective mycelium originating from the inoculum. These effects presumably reflect the capacity of the mycelium to behave as a co-ordinated unit and to economize on biomass when growing between discontinuously supplied resource units.

SUMMARY: Hyphae of Achlya bisexualis growing on a medium deficient in amino acids elongated but produced relatively few branches. Branching was enhanced by three classes of compound: cytochalasins A and E, the calcium ionophores A23187 and ionomycin and proton ionophores such as tetrachlorosalicylanilide (TCS), carbonylcyanide m-chlorophenylhydrazone (CCCP), and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP). We suggest that the effects of cytochalasins reflect the disruption of a microfilament-based system for vesicle transport. Enhancement of branching by ionophores implicates cytoplasmic ions in the control of branch initiation. There may be links between these phenomena and the earlier discovery that a new point of proton entry precedes the emergence of a branch and predicts its locus.