- Volume 65, Issue 3, 1971

SUMMARY: The enzyme endopolygalacturonase secreted by the fungus Ganoderma lucidum was purified by a three-step procedure until pectin methylesterase was no longer detectable. The endopolygalacturonase activity was inhibited by divalent metal ions. The enzyme had a peak of activity at pH 5.4 and two temperature optima: one at 50° and the other at 70°.

SUMMARY: Mitochondria isolated from Tetrahymena pyriformis carried out oxidative phosphorylation with succinate and 2-oxoglutarate as substrates. Electron transport was inhibited by rotenone, piericidin A, antimycin A and cyanide. Succinate-cytochrome c and ferricyanide oxidoreductases were antimycin A sensitive. NADH-cytochrome c and ferricyanide oxidoreductases were only partially inhibited by high concentrations of rotenone. Externally added NADH gave no oxygen uptake in the absence of artificial electron acceptors. The mitochondria contained haems a, c and protohaem, and difference spectra revealed the presence of cytochromes b, c, c1 and a pigment with an extinction maximum at 620 nm. Steady-state and kinetic measurements of cytochrome components were made. Several kinetically distinct flavoprotein components were present. Kinetic measurements suggested that the reduced 620 nm. component reacted sufficiently rapidly with molecular oxygen to have been the terminal oxidase.

SUMMARY: The occurrence and distribution of Saprolegniaceae in and around Marion Lake, British Columbia, Canada, has been investigated by single-core samples and transects in order to determine the principal sites of activity of these fungi. The lentic muds under 1 m. or more of water are generally very poor both in number of species and abundance. The marginal lentic muds are richer but reflect the flora of the emergent littoral muds. It is probable that many of the lentic mud records are for alien spores originating either from the open water community or the emergent littoral flora. These findings are discussed in relation to a general theory of fungi in the lake ecosystem. The majority of Saprolegniaceae are to be regarded as fungi of the emergent littoral. The distinctive acidophile community has again been recognized.

SUMMARY: Four monokaryotic axenic cultures derived from a dikaryotic isolate of Puccinia graminis tritici race 126-ANZ-6, 7 were tested for pathogenicity on wheat leaves. Only two rust cultures were pathogenic, one of which was propagated on wheat for six uredial generations. Cytological examination showed that cells of this culture were uninucleate and apparently haploid. This isolate may have arisen by somatic recombination.

SUMMARY: In Salmonella typhimurium PG154 the time taken for a round of DNA replication (C) at 37° is approximately 48 min. The time between the end of a round of DNA replication and the following cell division (D) is approximately 25 min. at 37°. In a temperature-sensitive mutant of S. typhimurium defective in the initiation of DNA synthesis, cell division at the restrictive temperature occurs at an approximately normal rate for 75 min., suggesting that C+D = 75 min.; the cells then elongate and form filaments. After about a further 1 h. in minimal medium at 38° cell division recommences at the ends of the filaments to form small cells. Filaments can divide at each end to produce more than one small cell. Once formed, small cells do not grow further. They do not synthesize DNA, RNA or protein and contain little DNA. Complete inhibition of DNA synthesis at the time of the shift stops cell division within about D min. and almost completely stops the production of small cells. A period of growth at 38° before the inhibition of DNA synthesis allows more division and the production of an almost normal number of small cells. Both the early divisions and the production of small cells are considered to be the result of the termination of rounds of DNA replication in the absence of new initiations.

SUMMARY: Thirty-nine out of 72 drug-resistant strains of Aeromonas liquefaciens isolated from cultured fish and soft-shelled turtles (Trionyx sinensis japonicus) in various districts of Japan carried transferable drug resistance factors. The fish included eel (Anguilla japonica), carp (Cyprinus carpio), ayu (Plecoglossus altivelis) and goldfish (Carassius auratus). The most common type of resistance factors had the markers of resistance to sulphanilamide and tetracycline and all belonged to the fi-type. Transferable drug resistance was not found in any of 12 strains of A. liquefaciens isolated from wild eels. The high incidence of resistance factors in A. liquefaciens from cultured fish is assumed to be due to the selective pressure exerted by chemotherapeutics used in fish culturing.

SUMMARY: X-irradiated Escherichia coli B, a filament-forming strain, showed improved survival of X-rays after treatment with its own extract, either in liquid or on solid media. Extract-promoted recovery was not shown by a non-filament-forming strain E. coli Bs-1. We failed to observe liquid holding recovery of X-irradiated bacteria in the absence of extract. Most experiments were performed in liquid medium where the increased number of survivors depended on the incubation period and the extract concentration. In about 30 min. the increase reached a saturation value; the maximum number of survivors was obtained using a certain (optimal) concentration of extract which was then employed in all subsequent experiments. The activity of the extract was completely destroyed by heating at 52° for 40 min. No activity was detected in the DNA, RNA or ribosomal fractions of the extract. The soluble remainder, however, was fully active, suggesting that soluble protein was the active principle.