- Volume 133, Issue 1, 1987

Bacteroids isolated from stem nodules of Sesbania were able to reduce C2H2 when glucose or succinate was the energy-yielding substrate. To be efficient, glucose always required low O2 concentrations, both with free O2 and with O2 delivered by leghaemoglobin extracted from French-bean nodules. Lactate detected in the stem nodule cytosol supported C2H2 reduction by bacteroid preparations, but the O2 tensions required for optimal activity were always higher than those defined for glucose, as predicted by the model of Bergersen & Trinchant (J. theor. Biol. 115, 93–102, 1985). In contrast, lactate was only present at very low concentrations in the cytosol of French-bean nodules and was unable to support C2H2 reduction by bacteroids isolated from these nodules. Lactate dehydrogenase (EC 1.1.1.27) extracted from stem nodule bacteroids and free-living cells of Rhizobium sp. (Sesbania) exhibited a higher affinity for lactate than did the enzyme from Rhizobium meliloti, R. leguminosarum biovar phaseoli or Bradyrhizobium and their symbiotic forms. Lactate appears to be a specific energy-yielding substrate supporting N2 fixation by Sesbania bacteroids and could play a major role when fermentative processes take place in the nodules.

The lipophilic cations butyltriphenylphosphonium (BTPP+), tetraphenylphosphonium (TPP+) and triphenylmethylphosphonium (TPMP+) were taken up into cells of Bacteroides amylophilus H18 under anaerobic conditions. Uptake was dependent on the presence of maltose together with both HCO− 3 and Na+; it was at a maximum at concentrations of ≥ 20 mm-HCO− 3 and ≥2 mm-Na+. The addition of 2-(n-heptyl)-hydroxyquinoline-N-oxide (HpHOQnO) or of an uncoupler of oxidative phosphorylation, or air, resulted in efflux of the lipophilic cations. From the binding behaviour and the physiological effects of the lipophilic cations, a membrane potential (Δψ) of 140 mV was estimated. There was no detectable ΔpH at an external pH of 6·7. The cytoplasmic Na+concentration was estimated to be 0·2 mm, indicating that B. amylophilus can maintain a Na+concentration gradient equivalent to at least 150 mV. Variation in the external Na+concentration (2 to 180 mm) had little influence on Δψ. High external concentrations of the fermentation products acetate, formate and succinate had little effect on the growth rate and the Δψ. The cytoplasmic ATP concentration decreased rapidly on addition of HpHOQnO oxide or of an uncoupler. The maximum internal ATP concentration was only maintained at an external concentration≥2mm-Na+. The NADH: fumarate reductase activity of vesicles of B. amylophilus was associated with alkalization of the suspension medium. The amount of H+taken up was in excess of the expected amount of scalar H+and was partially sensitive to uncoupler. It is concluded that the Δψ was generated via H+translocation driven primarily by the cytochrome-deficient NADH: fumarate reductase system. The transmembrane Na+gradient could be supported via the action of a Na+/2 H+antiporter.

An inducible methanol dehydrogenase showing high activity with 2-chloroethanol was purified from 2-chloroethanol-grown cells of the 1, 2-dichloroethane utilizing bacterium Xanthobacter autotrophicus GJ10. The enzyme consisted of a 60 kDa polypeptide that was associated with a 10 kDa polypeptide and contained pyrrolo-quinoline quinone (PQQ) as a prosthetic group. Chloroethanol-grown cells of strain GJ10 also contained an inducible NAD-dependent chloroacetaldehyde dehydrogenase. Its involvement in the metabolism of 2-chloroethanol was inferred from its absence in a 2-chloroethanol non-utilizing mutant. Three different isolates of X. autotrophicus that do not utilize 2-chloroethanol for growth produced chloroethanol dehydrogenase and chloroacetaldehyde dehydrogenase activities at similar levels as strain GJ10. It is concluded that both dehydrogenases are involved in the metabolism of natural compounds and due to their broad substrate specificity fortuitously also play a role in the metabolism of the xenobiotic compounds 1,2-dichloroethane and 2-chloroethanol.

A total of 564 strains of heterotrophic non-halophilic, marine, moderately halophilic and extremely halophilic bacteria was isolated from a saltern located near Huelva, SW Spain, facing the Atlantic Ocean. With the exception of the extremely halophilic bacteria, these were analysed by numerical techniques using the simple matching (SSM ) coefficient and clustering was achieved using the unweighted pair group method with averages (UPGMA) algorithm. At the 72.5% similarity level, a different number of phenons was found for each salinity group of bacteria. Of the 154 non-halophilic strains, the majority were recovered in 10 phenons, representing members of the genera Staphylococcus, Bacillus and Micrococcus. The 138 marine strains, with the exception of 24 strains, clustered into 12 phenons; seven phenons were assigned to the suprageneric grouping Pseudomonas-Alteromonas-Deleya, and the other phenons to Micrococcus, Staphylococcus, Bacillus and Vibrio. The 140 moderately halophilic strains grouped into eight phenons, with only 11 strains left unassigned. The majority of these isolates were assigned to the genus Deleya (two phenons) and they showed great similarity with the recently described species D. halophila, isolated from hypersaline soils. Four phenons comprised microorganisms with phenotypic characteristics very similar to the moderately halophilic Vibrio costicola. Two phenons were assigned to the genera Flavobacterium and Acinetobacter but these strains were not similar to previously described species. Of the 145 extremely halophilic isolates studied, the most important group was identified as belonging to the species Halobacterium salinarium (86 strains), followed by H. saccharovorum (20 strains), H. vallismortis (19 strains), Haloarcula hispanica (12 strains) and Halobacterium mediterranei (7 strains). Only one coccus was isolated, with characteristics very similar to those of Halococcus morrhuae.

Xanthomonas campestris pv. manihotis (ISPP List 1980) and X. campeststris pv. cassavae (ISPP List 1980) strains, isolated from cassava (Manihot esculenta) plants of different geographical origin, were studied by numerical analysis of 267 phenotypic features, computer-assisted comparison of gel electrophoregrams of soluble proteins, mol% G + C determinations, DNA: DNA hybridizations and virulence tests. X. campestris pv. manihotis and pv. cassavae constituted separate biological entities which could be differentiated from each other by four biochemical features, their symptoms on cassava, their soluble protein electrophoregrams and their DNA characteristics. Within each pathovar no correlation was found between phytopathogenicity, geographic origin and year of isolation of the strains, on the one hand, and the biochemical, physiological and protein electrophoretic properties on the other. Two yellowish Xanthomonas strains, CIAT 1164 and CIAT 1165, isolated from cassava in Colombia were genetically and electrophoretically similar to X. campestris pv. poinsettiicola, but were unable to infect Euphorbia pulcherrima. X. campestris pv. poinsettiicola was genetically more related to the X. campestris pv. manihotis cluster than to the X. campestris pv. cassavae cluster.

SUMMARY: The proteins of 14 strains of Mycoplasma hominis were compared by SDS-PAGE in gradient gels, by two-dimensional (2D) gel electrophoresis of extracts of 35S-labelled cells and by immunoblot analysis of cell proteins. The strains examined included the M. hominis type strain PG21 and 13 others isolated variously from genital tract, mouth, blood, upper urinary tract and a wound. These 14 strains shared 76–99% of proteins in SDS-gradient gel analysis and 41–72% in the 2D gels. As expected, the immunoblot analysis likewise revealed the existence of an extensive common protein pattern in M. hominis, in addition to a number of antigens shared only by some strains.