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1887

Microbiology Society logo - Volume 133, Issue 1, 1987

Volume 133, Issue 1

Volume 133, Issue 1, 1987

  • Physiology And Growth

      • Acetylene Reduction by Bacteroids Isolated from Stem Nodules of Specific Role of Lactate as an Energy-yielding Substrate

        https://doi.org/10.1099/00221287-133-1-37

        Bacteroids isolated from stem nodules of were able to reduce CH when glucose or succinate was the energy-yielding substrate. To be efficient, glucose always required low O concentrations, both with free O and with O delivered by leghaemoglobin extracted from French-bean nodules. Lactate detected in the stem nodule cytosol supported CH reduction by bacteroid preparations, but the O 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 CH reduction by bacteroids isolated from these nodules. Lactate dehydrogenase (EC 1.1.1.27) extracted from stem nodule bacteroids and free-living cells of sp. () exhibited a higher affinity for lactate than did the enzyme from biovar or and their symbiotic forms. Lactate appears to be a specific energy-yielding substrate supporting N fixation by Sesbania bacteroids and could play a major role when fermentative processes take place in the nodules.

    • The Membrane Potential in a Cytochrome-deficient Species of Its Magnitude and Mode of Generation

      https://doi.org/10.1099/00221287-133-1-73

      The lipophilic cations butyltriphenylphosphonium (BTPP), tetraphenylphosphonium (TPP) and triphenylmethylphosphonium (TPMP) were taken up into cells of H18 under anaerobic conditions. Uptake was dependent on the presence of maltose together with both HCO and Na; it was at a maximum at concentrations of ≥ 20 m-HCO and ≥2 m-Na. The addition of 2-(n-heptyl)-hydroxyquinoline--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 Naconcentration was estimated to be 0·2 m, indicating that can maintain a Naconcentration gradient equivalent to at least 150 mV. Variation in the external Naconcentration (2 to 180 m) 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≥2m-Na. The NADH: fumarate reductase activity of vesicles of was associated with alkalization of the suspension medium. The amount of Htaken up was in excess of the expected amount of scalar Hand was partially sensitive to uncoupler. It is concluded that the Δψ was generated via Htranslocation driven primarily by the cytochrome-deficient NADH: fumarate reductase system. The transmembrane Nagradient could be supported via the action of a Na/2 Hantiporter.

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  • Systematics

      • A Taxonomic Study of Heterotrophic Halophilic and Non-halophilic Bacteria from a Solar Saltern

        https://doi.org/10.1099/00221287-133-1-45

        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 () 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 and The 138 marine strains, with the exception of 24 strains, clustered into 12 phenons; seven phenons were assigned to the suprageneric grouping , and the other phenons to and 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 (two phenons) and they showed great similarity with the recently described species , isolated from hypersaline soils. Four phenons comprised microorganisms with phenotypic characteristics very similar to the moderately halophilic Two phenons were assigned to the genera and 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 (86 strains), followed by (20 strains), (19 strains), (12 strains) and (7 strains). Only one coccus was isolated, with characteristics very similar to those of

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