Thermophilic sulfate-reducing bacteria in cold marine sediment

Abstract Sulfate reduction was measured with the ³⁵SO₄²⁻ -tracer technique in slurries of sediment from Aarhus Bay, Denmark, where seasonal temperatures range from 0° to 15°C. The incubations were made at temperatures from 0°C to 80°C in temperature increments of 2°C to search for presence of psychrophilic, mesophilic and thermophilic sulfate-reducing bacteria. Detectable activity was initially only in the mesophilic range, but after a lag phase sulfate reduction by thermophilic sulfate-reducing bacteria were observed. No distinct activity of psychrophilic sulfate-reducing bacteria was detected. Time course experiments showed constant sulfate reduction rates at 4°C and 30°C, whereas the activity at 60°C increased exponentially after a lag period of one day. Thermophilic, endospore-forming sulfate-reducing bacteria, designated strain P60, were isolated and characterized as D esulfotomaculum kuznetsovii . The temperature response of growth and respiration of strain P60 agreed well with the measured sulfate reduction at 50°–70°C. Bacteria similar to strain P60 could thus be responsible for the measured thermophilic activity. The viable population of thermophilic sulfate-reducing bacteria and the density of their spores was determined in most probable number (MPN) dilutions. The density was 2.8·10⁴ cells·.g⁻¹ fresh sediment, and the enumerations suggested that they were all present as spores. This result agrees well with the observed lag period in sulfate reduction above 50°C. No environment with temperatures supporting the growth of these thermophiles is known in the region around Aarhus Bay.     

Vertical distribution of methane metabolism in microbial mats of the Great Sippewissett Salt Marsh

Methane metabolism was investigated with respect to depth in intertidal microbial mats of the Great Sippewissett Salt Marsh, Massachusetts. Although sulfate-reducing organisms dominate anaerobic carbon consumption in marine microbial mats, methanogens persist and their activity varies vertically and temporally in the mat system. In the Sippewissett mats, potential methane production for all mat layers was higher in the spring (17.2 ± 4.5 nmol CH₄ cm⁻² day⁻¹) than in the fall (3.0 ± 1.1 nmol CH₄ cm⁻² day⁻¹) and maximal rates were consistently observed in proximity to the chemocline (5–10 mm depth). The methane flux from the mat surface did not vary appreciably over time due to the ability of methanotrophic activity to limit net methane production. Evidence indicates that both aerobic and anaerobic oxidation of methane occurs in this system. The importance of H₂ as a substrate for methanogenesis appeared to be the greatest at the mat surface (0–10 mm), and the proportion of methylotrophic methanogens generally increased with depth. These results suggest that both non-equilibrium H₂ dynamics and the use of non-competitive substrates permit coexistence of methanogens and sulfate-reducing organisms in the mat system.     

Anaerobic oxidation of dimethylsulfide and methanethiol in mangrove sediments is dominated by sulfate-reducing bacteria

The oxidation of dimethylsulfide and methanethiol by sulfate-reducing bacteria (SRB) was investigated in Tanzanian mangrove sediments. The rate of dimethylsulfide and methanethiol accumulation in nonamended sediment slurry (control) incubations was very low while in the presence of the inhibitors tungstate and bromoethanesulfonic acid (BES), the accumulation rates ranged from 0.02–0.34 to 0.2–0.4 nmol g FW sediment⁻¹ h⁻¹, respectively. Degradation rates of methanethiol and dimethylsulfide added were 2–10-fold higher. These results point to a balance of production and degradation. Degradation was inhibited much stronger by tungstate than by BES, which implied that SRB were more important. In addition, a new species of SRB, designated strain SD1, was isolated. The isolate was a short rod able to utilize a narrow range of substrates including dimethylsulfide, methanethiol, pyruvate and butyrate. Strain SD1 oxidized dimethylsulfide and methanethiol to carbon dioxide and hydrogen sulfide with sulfate as the electron acceptor and exhibited a low specific growth rate of 0.010 ± 0.002 h⁻¹, but a high affinity for its substrates. The isolated microorganism could be placed in the genus Desulfosarcina (the most closely related cultured species was Desulfosarcina variabilis , 97% identity). Strain SD1 represents a member of the dimethylsulfide/methanethiol-consuming SRB population in mangrove sediments.     

Spirochaeta smaragdinae sp. nov., a new mesophilic strictly anaerobic spirochete from an oil field

An obligately anaerobic spirochete designated strain SEBR 4228^T (T = type strain) was isolated from an oil field of Congo, Central Africa. The strain grew optimally with a sodium chloride concentration of 5% (sodium chloride concentration growth range 1.0–10%) at 37°C (growth temperature range 20–40°C) and pH of 7.0–7.2 (pH growth range pH 5.5–8.0). Strain SEBR 4228^T grew on carbohydrates (glucose, fructose, ribose, d -xylose, galactose, mannitol and mannose), glycerol, fumarate, peptides and yeast extract. Yeast extract was required for growth and could not be replaced by vitamins. It reduced thiosulfate and sulfur, to H₂S. Glucose was oxidised to lactate, acetate, CO₂ and H₂S in the presence of thiosulfate but in its absence lactate, ethanol, CO₂ and H₂ were produced. Fumarate was fermented to acetate and succinate. The G+C content of strain SEBR 4228^T was 50%. Strain SEBR 4228^T was spiral shaped measuring 5–30 by 0.3–0.5 μm and was motile with a corkscrew-like motion. Electron microscopy revealed the presence of periplasmic flagella in a 1-2-1 arrangement. Strain SEBR 4228^T possessed features typical of the members of the genus Spirochaeta . 16S rRNA sequence analysis revealed that it was closely related to Spirochaeta bajacaliforniensis (similarity 98.6%). The lack of DNA homology with S. bajacaliforniensis (38%), together with other phenotypic differences, indicated that strain SEBR 4228^T is a new species, which we have designated Spirochaeta smaragdinae . The type strain is SEBR 4228^T (= DSM 11293).     

Assimilation of methane and inorganic carbon by microbial communities mediating the anaerobic oxidation of methane

The anaerobic oxidation of methane (AOM) is a major sink for methane on Earth and is performed by consortia of methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). Here we present a comparative study using in vitro stable isotope probing to examine methane and carbon dioxide assimilation into microbial biomass. Three sediment types comprising different methane-oxidizing communities (ANME-1 and -2 mixture from the Black Sea, ANME-2a from Hydrate Ridge and ANME-2c from the Gullfaks oil field) were incubated in replicate flow-through systems with methane-enriched anaerobic seawater medium for 5–6 months amended with either ¹³CH₄ or H¹³CO₃^-. In all three sediment types methane was anaerobically oxidized in a 1:1 stoichiometric ratio compared with sulfate reduction. Similar amounts of ¹³CH₄ or ¹³CO₂ were assimilated into characteristic archaeal lipids, indicating a direct assimilation of both carbon sources into ANME biomass. Specific bacterial fatty acids assigned to the partner SRB were almost exclusively labelled by ¹³CO₂, but only in the presence of methane as energy source and not during control incubations without methane. This indicates an autotrophic growth of the ANME-associated SRB and supports previous hypotheses of an electron shuttle between the consortium partners. Carbon assimilation efficiencies of the methanotrophic consortia were low, with only 0.25–1.3 mol% of the methane oxidized.     

Affinity Purification of Synenkephalin-Containing Peptides Including a Novel 23.3-Kilodalton Species

Abstract: Affinity chromatography has been used for rapid and high-yield purification of synenkephalin (proenkephalin 1 -70) containing peptides present in bovine adrenal medulla (BAM) chromaffin granular lysate. A column of CN-Br-activated Sepharose 4B coupled to synenkephalin antiserum bound synenkephalin immunoreactivity which was eluted by a stepwise gradient of 50 mM ammonium acetate containing 20% (vol/vol) acetonitrile over the pH range 7–3. Synenkephalin immunoreactivity emerged as two peaks, eluting at pH 5.5 and 4.5. Characterization of the two peaks by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting indicated that the pH 5.5 peak contained principally low-molecular-weight proenkephalin species (8.6 and 12.6 kilodaltons), whereas the pH 4.5 peak contained, in addition, high-molecular-weight proenkephalin species (18.2 and 23.3 kilodaltons). The 8.6- and 12.6- kilodalton species were isolated from the pH 5.5 peak by TSK gel filtration HPLC, whereas the pH 4.5 peak was further purified by passage over successive affinity columns coupled to antiserum against BAM 22P (proenkephalin 182–203) and [Met⁵]-enkephalin-Arg⁶-Gly⁷-Leu⁸. The former column retains the 23.3-kilodalton species, whereas the latter column retains the 18.2-kilodalton species. The 23.3- kilodalton peptide represents a novel putative proenkephalin intermediate (proenkephalin-1–206), containing [Leu⁵]- enkephalin at the C-terminus.     

The role of polyglucose in oxygen-dependent respiration by a new strain of Desulfovibrio salexigens

Abstract: Desulfovibrio salexigens strain Mastl was isolated from the oxic/anoxic interface of a marine sediment. Growth under sulfate-reducing conditions was accompanied by polyglucose accumulation in the cell with every substrate tested. Highest polyglucose storage was found with glucose (0.8–1.0 g polyglucose (g protein)⁻¹), but the growth rate with this substrate was very low (0.015 h⁻¹). Anaerobically grown cells of strain Mastl exhibited immediate oxygen-dependent respiration. The endogenous oxygen reduction rate was proportional to the polyglucose content. The rate of aerobic respiration of pyruvate was also directly related to the polyglucose content indicating that this organism was only able to respire with oxygen as long as polyglucose was present. Maximum oxygen reduction rates were found at air saturating concentrations and were relatively low (3–50 nmol O₂ min⁻¹ (mg protein)⁻¹). Catalase was constitutively present in anaerobically grown cells. When batch cultures were exposed to oxygen, growth ceased immediately and polyglucose was oxidized to acetate within 40–50 h. Like the oxygen reduction activity, the nitro blue tetrazolium (NBT)-reduction activity in these cells was proportional to the polyglucose content. Under anaerobic starvation conditions there was no correlation between the NBT-reduction activity and polyglucose concentration and polyglucose was degraded slowly within 240 h. The ecological significance of aerobic polyglucose consumption is discussed.     

α-Galactosidase from the yeast Torulaspora delbrueckii IFO 1255

The yeast Torulaspora delbrueckii IFO 1255 was selected as the strain fermenting melibiose from 35 strains of Torulaspora species. The strain IFO 1255 produced extracellular and cell-associated forms of α-galactosidase when grown on either melibiose or galactose as the sole carbon source. Most of the enzyme was located outside of the cell membrane: the periplasmic space, or cell walls, or both. α-Galactosidase was purified to homogeneity from the cell-free extract of the strain IFO 1255 by acid treatment and column chromatography on DEAE-Toyopearl 650M and Butyl-Toyopearl 650M. The molecular weight of the purified enzyme was estimated to be 88 000 by SDS-polyacrylamide gel electrophoresis and 530 000 by gel filtration. The enzyme contained 50% of its molecular weight as carbohydrate. Optimum pH and temperature were 4.5–5.5 and 55°C, respectively. The enzyme was inhibited strongly by Ag²⁺, Hg²⁺ and Cu²⁺ each at 1 mmol 1^-1. The K _m (μmol 1^-1) for p -, o -, m -nitrophenyl α-D-galactopyranoside, melibiose, raffinose and stachyose were 2.8, 1.3, 2.8, 4.2, 170 and 230, respectively, and V _max (μmol min^-1 mg protein^-1) for those substrates were 310, 140, 21, 22, 30 and 44, respectively. The properties of α-galactosidase from T. delbrueckii IFO 1255 were similar to those from the related species, Saccharomyces cerevisiae.     

Sulfate-reducing bacteria in littoral sediment of Lake Constance

Abstract The viable population of sulfate-reducing bacteria (SRB) in littoral sediments of Lake Constance was investigated using enrichment and enumeration techniques. Enrichment studies established that most types of SRB grew best in media with low salt concentrations (max. 0.4 g Cl⁻/1), consistent with the low salinity of the freshwater habitat. Enumerations were based on an adequate medium with the following electron donors: H₂, lactate, acetate, propionate, butyrate, caprylate, succinate, benzoate, or S₂O₃²⁻ for thiosulfate-disproportionating bacteria. Cultures were incubated for 6 weeks to obtain maximum counts. A maximum cell density of 6.3 × 10⁶ cells per ml sediment was estimated, which is the highest number of SRB ever reported for anoxic sediments. A comparison with measured sulfate reduction rates showed that the enumeration techniques were about 10–100-fold more efficient than those previously used. The population of SRB had a characteristic structure consisting of 87.7% H₂-utilizing SRB (physiologically resembling the classical Desulfovibrio species); 12.0% propionate utilizers (tentatively identified as Desulfobulbus species); 0.3% long chain fatty acid-oxidizing Desulfovibrio sapovorans species. Acetate-utilizing SRB ( Desulfotomaculum acetoxidans ) constituted ≤ 0.05% of the total estimated population. Moreover, the latter species was only present as inactive spores. Benzoate-degrading SRB were not detected.     

Grazing by oligochaetes and snails on epiphytes

SUMMARY. 1. The isotope ³³P was used to assess the effect of grazitig by oligochaetes (mainly Stylaria lacttstris L.) and the snail, Lymnaea peregra (Muller), on epiphytes within an Equisetum fluviatile L. stand.
2. Two 1 m² polystyrene enclosures were set up within the emergent macrophyte zone of the lake. At the start of the experiment ³³P-solution was mixed with the water in both tanks. Algal and animal samples for ³³P- analysis were collected during the peak occurrence of epiphytes in June.
3. Phosphorus release rates from the animals through defaecation and excretion were measured in the laboratory. The grazing rate of oligochaetes was 2.2–4.1 mg P m⁻² (of bottom) d⁻¹ of which about two - thirds was released and recycled. The oligochaete density ranged from 13,400 to 20,900 m⁻². The snails (25 ind. m⁻²) grazed 1.2-1.5 mg P m⁻²d⁻¹of whieh about a quarter was released through defaecation and excretion.
4. Daily consumption by the oligochaetes and snails corresponded to 22–45% of the average phosphorus uptake by the epiphytes.     

The effect of moisture potential on growth and survival of root nodule bacteria in peat culture and on seed

Peat from three sources was dried, milled and packed separately in polyethylene bags and sterilized by irradiation. The carrier was impregnated with broth cultures of either Rhizobium leguminosarum bv. trifolii strain WU95, Bradyrhizobium japonicum strain CB1809 or B. lupini strain WU425 and sterile water to provide five moisture potentials in the range > - 1 × 10⁴ - 1 × 10⁶ Pa. The packets were stored at 26°C under conditions which restricted moisture loss. Numbers of root nodule bacteria were counted at intervals up to 12 weeks. No single moisture potential was optimum for all strains in all carriers because of a significant ( P < 0.05) interaction between moisture potential × strain × carrier × time. Where direct comparisons could be made, all strains survived best at - 1 × 10⁴ and/or −3.2 × 10⁴ Pa. Seeds of Trifolium subterraneum and polypropylene beads (used to avoid seed coat toxicity), were inoculated with WU95 prepared in two sources of peat and at each of the above moisture potentials and stored at 15°C. Seed coat toxicity significantly effected the log death rate ( k ) of WU95 on subterraneum clover seed for the period 0–0.25 d ( k 1.796) compared with k - 0.399 for polypropylene beads. In the first 24 h moisture did not affect survival but by 28 d rhizobia grown in Badenoch peat survived best at −3.2 × 10⁴ Pa. In Millicent peat, survival was equally as good at −3.2 × 10⁴ and −1 × 10⁴ Pa.     

Transformation of Bacillus amyloliquefaciens protoplasts with plasmid DNA

Abstract A method for efficient polyethylene glycol (PEG)-mediated transformation of Bacillus amyloliquefaciens protoplasts with plasmid DNA is described. The best conditions found for protoplast regeneration included using 0.45 M sucrose both during the cultivation of the cells and (as an osmotic stabilizer) during their treatment with lysozyme, whereas 0.25 M sodium-succinate was added to the regeneration plates. Under these conditions about 5–10% of input cells regenerated. The highest transformation frequency with plasmid DNA was obtained with a PEG 6000 concentration of 22.5% (w/v). Transforming B. amyloliquefaciens strains with the plasmid pUB110 isolated from B. amyloliquefaciens resulted in 2–4 · 10⁵ transformants/μg DNA, 100–1 000-times as high as with DNA from Bacillus subtilis , suggesting a restriction barrier between the two species. Transformation of B. amyloliquefaciens with plasmids pC194 or pE194 cop -6 gave poor yields and no restriction barrier could be demonstrated for these plasmids. However, by curing pC194 from one of the transformants, a mutant strain compatible to both the plasmids could be isolated, yielding 2–3·10⁴ transformants/μg DNA. Both laboratory and industrial B. amyloliquefaciens strains could be transformed with the procedure.     

The plant-growth-promoting rhizobacteria Bacillus pumilus and Bacillus licheniformis produce high amounts of physiologically active gibberellins

The plant-growth-promoting rhizobacteria (PGPR), Bacillus pumilus and Bacillus licheniformis, isolated from the rhizosphere of alder ( Alnus glutinosa [L.] Gaertn.) have a strong growth-promoting activity. Bioassay data showed that the dwarf phenotype induced in alder seedlings by paclobutrazol (an inhibitor of gibberellin [GA] biosynthesis) was effectively reversed by applications of extracts from media incubated with both bacteria and also by exogenous GA₃. Full-scan gas chromatography-mass spectrometry analyses on extracts of these media showed the presence of GA₁, GA₃, GA₄and GA₂₀, in addition to the isomers 3- epi -GA₁ and iso -GA₃. Isotope dilution analysis indicated that epi -GA₁ was an artefact. Likewise, iso -GA₃ is also probably an artifact spontaneously formed during extraction and/or analysis. In both culture media, GA₁ was present in higher concentrations (130–150 ng ml⁻¹) than GA₃ (50–60 ng ml⁻¹), GA₄ (8–12 ng ml⁻¹) and GA₂₀ (2–3 ng ml⁻¹). The data indicated that culture of both bacteria accumulate bioactive C19-gibberellins in relative high amounts and that these GAs appear to be physiologically active in the host plant. The evidence suggests that the promotion of stem elongation induced by the PGPR could be mediated by bacterial GAs.     

Fish production in the Jarama River, Central Spain

Fish production was estimated at three sites on the Jarama River, a small, typical upland river in Central Spain. Population estimates were made by the successive removal method of electrofishing. The same six species were recorded at each of the sites: Chondrostoma polylepis, Barbus barbus bocagei, Leuciscus cephalus pyraenaicus, Salmo trutta m. fario, Gobio gobio and Cobitis paludicola , with the first three species always dominant. Density, biomass, production (assuming that N_o is the total number of eggs spawned), and available production were, respectively: 13502-85776 ind. ha⁻¹, 178.6–221.3 kg ha⁻¹, 221.7–583.6 kg ha⁻¹ yr⁻¹, 118.1–271.9 kg ha⁻¹ yr⁻¹. Production estimates based on mortality curves were 7.9–19.5% (mean: 13.7) lower than those based on estimated from the number of eggs laid. Production per unit of area was highest at the widest and deepest site. Brown trout production contributed only 2–4% of the total production for all sites.     

Studies on the Production of Extracellular Proteinases by a Non-pigmented Strain of Chromobacterium lividum Isolated from Abattoir Effluent

A highly proteolytic bacterium isolated from abattoir effluent was identified as a non-pigmented strain of Chromobacterium lividum. Ferrous or ferric ions at concentrations between 1·8 × 10^-5 and 9 × 10^-4 g ions/1, which is 2–3 orders of magnitude greater than that required for growth, were essential for extracellular proteinase production in aerated but not in static culture. Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺ or Zn²⁺ ions could not replace iron. Four proteinases (I-IV) were produced in static culture, but only proteinase I was formed in significant quantities in aerated culture. With both forms of culture amino nitrogen was essential for proteinase production; glucose inhibited formation in aerated, but not static, cultures. Growth occurred over the range 1–33 °C, whereas proteinase production ceased at 27 °C, with maximum activity at 13 °C. Proteinase production appeared to be controlled by an interaction between iron, oxygen tension and glucose.     

Hydrogen uptake in Anabaena sp. strain CA does not protect nitrogenase from inactivation by hyperbaric oxygen

Abstract Two mutants of Anabaena sp. strain CA were used to demonstrate that oxygen-dependent hydrogen uptake was not the primary means to protect the nitrogenase enzyme complex from the deleterious effects of hyperbaric oxygen in vivo. Exposure to air caused the immediate and irreversible inactivation of nitrogenase activity in an oxygen-sensitive mutant, designated strain 22Y. Inactivation was concomitant with the destruction of the molybdo-iron (MoFe) protein of the nitrogenase complex. The mutant 22Y expressed an O₂-stable, Ni²⁺-stimulated hydrogen uptake of up to 2.7 μM H₂ per mg dry wt per h. Conversely, after exposure to 1% CO₂-99% O₂ for 3 h, both wild-type strain CA and a hydrogen uptake deficient (Hup⁻) mutant, strain N9AR, recovered 70–80% of their original acetylene reduction capacity with no apparent perturbations in the MoFe protein.     

Toll-like receptors 2 and 4 mediate Abeta(1-42) activation of the innate immune response in a human monocytic cell line

The primary molecules for mediating the innate immune response are the Toll-like family of receptors (TLRs). Recent work has established that amyloid-beta (Aβ) fibrils, the primary components of senile plaques in Alzheimer's disease (AD), can interact with the TLR2/4 accessory protein CD14. Using antibody neutralization assays and tumor necrosis factor alpha release in the human monocytic THP-1 cell line, we determined that both TLR2 and TLR4 mediated an inflammatory response to aggregated Aβ(1–42). This was in contrast to exclusive TLR ligands lipopolysaccharide (LPS) (TLR4) and tripalmitoyl cysteinyl seryl tetralysine (Pam₃CSK₄) (TLR2). Atomic force microscopy imaging showed a fibrillar morphology for the proinflammatory Aβ(1–42) species. Pre-treatment of the cells with 10 μg/mL of a TLR2-specific antibody blocked ∼50% of the cell response to fibrillar Aβ(1–42), completely blocked the Pam₃CSK₄ response, and had no effect on the LPS-induced response. A TLR4-specific antibody (10 μg/mL) blocked ∼35% of the cell response to fibrillar Aβ(1–42), completely blocked the LPS response, and had no effect on the Pam₃CSK₄ response. Polymyxin B abolished the LPS response with no effect on Aβ(1–42) ruling out bacterial contamination of the Aβ samples. Combination antibody pre-treatments indicated that neutralization of TLR2, TLR4, and CD14 together was much more effective at blocking the Aβ(1–42) response than the antibodies used alone. These data demonstrate that fibrillar Aβ(1–42) can trigger the innate immune response and that both TLR2 and TLR4 mediate Aβ-induced tumor necrosis factor alpha production in a human monocytic cell line.     

Drinking rate, uptake of bacteria and microalgae in turbot larvae

The drinking rate of turbot larvae increased from 14 to 120 nl larva^-1 h^-1 from day 2 to 11 after hatching, which gave a slightly increased specific drinking rate (calculated per biomass) from day 2 to 7 (0·8–1·9 nl μg carbon^-1 h^-1. The clearance rate of both algae and bacteria was 10–100 times higher than the drinking rate, which indicated that the larvae had an active uptake of both algae and bacteria. On day 2 and 4 after hatching highest clearance rate was observed for Tetraselmis sp. On day 6 about the same clearance rate was observed for bacteria, Isochrysis galbana and Tetraselmis sp. Until day 4 the turbot larvae had a higher ingestion rate of Tetraselmis sp. than of I. galbana , whereas on day 6 the rates were similar (28–41 ng carbon larvae^-1 h^-1). The assimilation efficiency was somewhat higher for I. galbana than for Tetraselmis sp., and on day 6 the assimilated algae constituted 1·5 and 0·9% of the larval biomass for I. galbana and Tetraselmis sp., respectively.     

Growth of a facultative anaerobe under oxygen-limiting conditions in pure culture and in co-culture with a sulfate-reducing bacterium

Abstract The occurrence and properties were studied of glucose-metabolizing bacteria present in the anaerobic sediment 5–10 cm below the surface of an estuarine tidal mud-flat. Of all these bacteria (10⁴– 10⁵ per g wet sediment) 80–90% were facultatively anaerobic species. Chemostat enrichments on glucose under aerobic, oxygen-limited and alternately aerobic-anaerobic conditions also yielded cultures dominated by facultative anaerobes. One of the dominant species, tentatively identified as a Vibrio sp., was studied in more detail under oxygen-limiting conditions. Fermentative and respiratory metabolisms were found to operate simultaneously, and the ratio between the two was regulated by the extent of oxygen limitation. A small fraction of the acetate formed under such growth conditions was shown to be subsequently respired. A co-culture was established of the Vibrio sp. and a sulfate-reducing bacterium ( Desulfovibrio HL21 ) in an aerated chemostat. The importance of these observations is discussed in relation to the role of facultative anaerobes in anaerobic habitats.     

Isolation and characterization of plant growth-promoting strain Pantoea NII-186. From Western Ghat Forest soil, India

Aims:  To isolate plant growth-promoting bacterium from Western Ghat forests in India.
Methods and Results:  A Gram-negative, rod shaped, cream white coloured strain Pantoea NII-186 isolated from Western Ghat soil sample. The taxonomic position of the bacterium was confirmed by sequencing of 16S rRNA and phylogenetic analysis. A strain grew at a wide range of temperature ranging from 5–40°C, but optimum growth was observed at 28–30°C. It showed multiple plant growth-promoting attributes such as phosphate solubilization activity, indole acetic acid (IAA) production, siderophore production and HCN production. It was able to solubilize (28 μg of Ca₃PO₄ ml⁻¹ day⁻¹), and produce IAA (59 μg) at 28°C. The solubilization of insoluble phosphate was associates with a drop in the pH of the culture medium. Pantoea sp. NII-186 tolerate to different environmental stresses like 5–40°C, 0–7% salt concentration and 4–12 pH range.
Conclusions:  The 16S rRNA gene sequence confirmed that the isolate NII-186 was belongs to Pantoea genus and showed considerable differences in physiological properties with previously reported species of this genus. Isolate NII-186 possessed multiple attributes of plant growth-promoting activity.
Significance and Impact of the Study:  Hence in the context it is proposed that Pantoea sp. NII-186, could be deployed as an inoculant to attain the desired plant growth-promoting activity in agricultural environment.