Differential regulation of hypothalamic pituitary corticotropin releasing hormone receptors during development of adjuvant-induced arthritis in the rat

An obligately anaerobic spirochete designated strain SEBR 4228T (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 degrees C (growth temperature range 20-40 degrees C) and pH of 7.0-7.2 (pH growth range pH 5.5-8.0). Strain SEBR 4228T 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 4228T was 50%. Strain SEBR 4228T was spiral shaped measuring 5-30 by 0.3-0.5 micron and was motile with a corkscrew-like motion. Electron microscopy revealed the presence of periplasmic flagella in a 1-2-1 arrangement. Strain SEBR 4228T 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 4228T is a new species, which we have designated Spirochaeta smaragdinae. The type strain is SEBR 4228T (= DSM 11293).     

Alterococcus agarolyticus, gen.nov., sp.nov., a halophilic thermophilic bacterium capable of agar degradation

Five strains of facultatively anaerobic moderately thermophilic bacteria were isolated from two hot springs in the intertidal zone of Lutao, Taiwan. They produced extracellular agarase on agar medium, yielding reducing sugars and organic acids as the end products under either aerobic or anaerobic conditions. The growth temperature range was approximately 38-58 degrees C with an optimal temperature of about 48 degrees C. The five strains tolerated a relatively narrow pH range from 7.0 to 8.5. They were Gram-negative halophiles growing optimally at 2.0-2.5% NaCl (ca. 0.34-0.43 M). They were capable of anaerobic growth by fermenting glucose and producing various organic acids such as butyrate, propionate, formate, lactate, and acetate. Cells grown in liquid medium were motile monotrichous cocci, normally 0.8-0.9 micron in diameter. They possessed saturated anteiso-15-carbon acid (anteiso-C15:0) as the most abundant cellular fatty acid (46.0-51.3 mo1%) and had G + C contents ranging from 65.5 to 67.0 mo1%. They are the first thermophiles found to degrade agar and also the first halophilic thermophilic bacteria known to be capable of both aerobic and anaerobic fermentative growth. These bacteria are considered to represent a new genus that we named Alterococcus, and Alterococcus agarolyticus is the type species.     

Desulfovibrio aminophilus sp. nov., a novel amino acid degrading and sulfate reducing bacterium from an anaerobic dairy wastewater lagoon

A mesophilic strain of sulfate-reducing bacterium, designated ALA-3T (T = type strain), was isolated from an anaerobic lagoon of a dairy wastewater treatment plant. The curved, Gram-negative, non-sporeforming cells (0.2 x 3.0-4.0 microns) existed singly or in chains, and were motile by single polar flagella. Optimum growth occurred at 35 degrees C and pH 7.5 on a medium containing lactate and sulfate. Thiosulfate or sulfite but not elemental sulfur, nitrate, or fumarate could also replace sulfate as an electron acceptor. Formate, alanine, aspartate, leucine, isoleucine, valine, and methionine, H2/CO2 and ethanol also served as electron donors with sulfate as an electron acceptor. Pyruvate, casamino acids, peptone, serine, glycine, cysteine and threonine were fermented. Sulfite and thiosulfate were disproportionated to sulfate and sulfide. The G + C content of the DNA was 66 mol % G + C. Phylogenetic analysis revealed that Desulfovibrio africanus was the nearest relative (similarity of 89%). Strain ALA-3T is physiologically and phylogenetically different from other Desulfovibrio species, and is designated Desulfovibrio aminophilus sp. nov. (DSM 12254).     

Biohydrogen Production by Mesophilic Anaerobic Fermentation of Glucose in the Presence of Linoleic Acid

In this work, linoleic acid (LA), a long chain fatty acid bearing 18 carbons and two double bonds, inhibited hydrogen consumption in a mixed anaerobic culture acclimated to glucose. At pH = 7.6, a metabolic shift from methane to hydrogen formation was observed in cultures maintained at 37°C and fed 5,000?mg?L?1 glucose in the presence of 500–2,000?mg?L?1 LA. The hydrogen yield increased with increasing LA levels while the quantity of methane decreased. The major volatile fatty acids produced were acetate and butyrate with greater levels observed in cultures fed with LA. Acetate, butyrate, and hydrogen accumulation suggests inhibition of aceticlastic methanogens, hydrogenotrophic methanogens, and butyrate degrading microorganisms, respectively, in the presence of LA. A maximum hydrogen yield of 1.71±0.22?mole?mole?1 glucose was observed only when glucose was reinjected into cultures receiving 2,000?mg?L?1 LA plus 5,000?mg?L?1 glucose.     

Factors influencing rumen fermentation: effect of hydrogen on formation of propionate

The effect of hydrogen on fermentation of lactate, pyruvate, fumarate, and succinate by resting rumen microorganisms has been investigated. Under an atmosphere of nitrogen, lactate was fermented to yield acetate as the major product (85 to 100 mole %) and propionate (0 to 17 mole %) and butyrate (0 to 3%) as secondary products. Under hydrogen, there was increased formation of both propionate and total volatile fatty acids. The amount of propionate increased 4 to 8 times and total volatile fatty acids 2.5 to 3.2 times. Propionate formation was proportional to the hydrogen concentration and reached a maximum at a partial pressure of hydrogen of .2 N/m2. With [2-carbon-14] lactate, propionate was formed via the dicarboxylic acid pathway under both nitrogen or hydrogen. Hydrogen did not affect significantly the fermentation of pyruvate or succinate. With fumarate under hydrogen, propionate and total volatile fatty acids increased 6.8 and 2 times while acetate was unchanged. The mechanism by which hydrogen exerts these effects is discussed in relation to the role of methanogenesis in the rumen.     

Xanthobacter tagetidis sp. nov., an organism associated with Tagetes species and able to grow on substituted thiophenes

Members of the marigold genus of flowering plants (the genus Tagetes), which synthesize and accumulate thiophene compounds in their roots, were investigated as potential sources of bacteria able to degrade substituted thiophenes. Batch and continuous enrichment cultures inoculated with compost from root balls of Tagetes patula and Tagetes erecta reproducibly produced the same predominant type of bacterium when they were supplied with thiophene-2-carboxylate (T2C) or thiophene-2-acetate (T2A) as a carbon and energy substrate. This organism was a yellow-pigmented, neutrophilic, mesophilic, gram-negative, pleomorphic, rodshaped bacterium, which we classify as a new species of the genus Xanthobacter, Xanthobacter tagetidis; strain TagT2C (= DSM 11105) is the type strain. Strain TagT2CT (T = type strain) grew on simple thiophenes, such as T2C, thiophene-3-carboxylate, and T2A, on analogs of these compounds (pyrrole-2-carboxylate and furan-2-carboxylate), and on the condensed thiophene dibenzothiophene. X. tagetidis was facultatively autotrophic, fixing carbon dioxide by means of ribulose bisphosphate carboxylase, and was able to grow on hydrogen, thiosulfate, or sulfide as an energy substrate. It also grew on a wide range of other heterotrophic, chemolithotrophic, and methylotrophic substrates. Its growth on T2C was optimal at 28 to 31 degrees C and pH 7.6 to 7.8, and the maximum growth rate in batch culture was 0.22 h-1. The DNA base composition of X.tagetidis is 68 mol% G + C. A 16S ribosomal DNA sequence analysis of strain TagT2CT showed that this organism represents a distinct lineage within the Aquabacter-Azorhizobium-Xanthobacter cluster of the alpha-2 subclass of the Pro-teobacteria. Discrimination of X. tagetidis from the other genera in this group and from other Xanthobacter species is discussed.     

Meiothermus cerbereus sp. nov., a new slightly thermophilic species with high levels of 3-hydroxy fatty acids

Strains of Meiothermus cerbereus sp. nov. were isolated from the hot springs within the Geysir geothermal area of Iceland. The strains of Meiothermus cerbereus produce red-orange-pigmented colonies, have an optimum growth temperature of about 55 degrees C, and have higher levels of 3-OH fatty acids than the strains of the other species of the genus Meiothermus. These strains, unlike all other strains of the species of the genus Meiothermus examined previously, required cysteine, thiosulfate, or thioglycolate for growth in liquid Thermus medium, but not in the corresponding medium solidified with agar. Several strains belonging to Meiothermus silvanus, isolated from Geysir, also required reduced sulfur compounds for growth in liquid medium, leading to the hypothesis that this requirement is not a taxonomic characteristic of the new species. The new species represented by strains GY-1T and GY-5 can be distinguished from the other species of the genus Meiothermus by biochemical characteristics, fatty acid composition, DNA-DNA reassociation values, and 16S ribosomal DNA sequence. The type strain for Meiothermus cerbereus is GY-1 (= DSM 11376).     

Diverting Electron Fluxes to Hydrogen in Mixed Anaerobic Communities Fed with Glucose and Unsaturated C18 Long Chain Fatty Acids

Hydrogen (H2) production was maximized and methane (CH4) formation was minimized in a mixed anaerobic culture which was maintained at 21°C and fed glucose plus unsaturated long chain fatty acids (LCFAs). The initial pH in the batch reactors was 7.8±0.2. The two LCFAs under consideration included linoleic acid (LA) (two C=C bonds) and oleic acid (OA) (one C=C bond). Hydrogen production was observed when glucose was injected on Day 0 and again after Day 4. The H2 yield in cultures fed LA was less than those receiving OA. The H2 yield reached a maximum of approximately 1.1?mol?H2?mol?1 glucose when the LA level was 2,000?mg?L?1. In the case of OA, a maximum yield of 1.3?mol?H2?mol?1 glucose was attained with 2,000?mg?L?1. The inhibition caused by the addition of LA or OA diverted a fraction of electrons toward proton reduction. Under maximum H2 production conditions in the LA fed cultures the acetate production pathway was repressed, while in cultures fed OA the acetate pathway was dominant. The amount of CH4 produced decreased with increasing H2 production and the major volatile fatty acids detected were acetate, propionate and butyrate. Small quantities of formate were detected only in cultures fed LA after the first glucose injection. As the LCFA concentration increased, the initial glucose degradation rate decreased.     

Guess What! Non-inflammatory cutaneous myiasis caused by the larva of Cordylobia anthropophaga

Short-chain fatty acids produced by bacterial fermentation of dietary fiber may provide a tonic stimulus to colonocyte differentiation that contributes to the protective effect of fiber against colorectal malignancy. Since brush-border enzymes are common markers of colonocytic differentiation, we compared the effects of equimolar (10 mmol/L) concentrations of the three most common short-chain fatty acids, acetate, butyrate, and propionate, on the alkaline phosphatase and dipeptidyl dipeptidase specific activity of human colonic mucosal biopsies obtained from normal volunteers. Only butyrate significantly stimulated alkaline phosphatase specific activity (50.4% +/- 18.6%, P < .05). Short-chain fatty acid stimulation of dipeptidyl dipeptidase did not achieve statistical significance. Fibers yielding high colonic butyrate levels could have different effects on human colonic mucosal differentiation.     

Comparative study of computer-assisted image analysis and light-microscopically determined estrogen receptor status of breast carcinomas

The growth of the syntrophic propionate-oxidizing bacterium strain MPOB in pure culture by fumarate disproportionation into carbon dioxide and succinate and by fumarate reduction with propionate, formate or hydrogen as electron donor was studied. The highest growth yield, 12.2 g dry cells/mol fumarate, was observed for growth by fumarate disproportionation. In the presence of hydrogen, formate or propionate, the growth yield was more than twice as low: 4.8, 4.6, and 5.2 g dry cells/mol fumarate, respectively. The location of enzymes that are involved in the electron transport chain during fumarate reduction in strain MPOB was analyzed. Fumarate reductase, succinate dehydrogenase, and ATPase were membrane-bound, while formate dehydrogenase and hydrogenase were loosely attached to the periplasmic side of the membrane. The cells contained cytochrome c, cytochrome b, menaquinone-6 and menaquinone-7 as possible electron carriers. Fumarate reduction with hydrogen in membranes of strain MPOB was inhibited by 2-(heptyl)-4-hydroxyquinoline-N-oxide (HOQNO). This inhibition, together with the activity of fumarate reductase with reduced 2,3-dimethyl-1,4-naphtoquinone (DMNH2) and the observation that cytochrome b of strain MPOB was oxidized by fumarate, suggested that menequinone and cytochrome b are involved in the electron transport during fumarate reduction in strain MPOB. The growth yields of fumarate reduction with hydrogen or formate as electron donor were similar to the growth yield of Wolinella succinogenes. Therefore, it can be assumed that strain MPOB gains the same amount of ATP from fumarate reduction as W. succinogenes, i. e. 0.7 mol ATP/mol fumarate. This value supports the hypothesis that syntrophic propionate-oxidizing bacteria have to invest two-thirds of an ATP via reversed electron transport in the succinate oxidation step during the oxidation of propionate. The same electron transport chain that is involved in fumarate reduction may operate in the reversed direction to drive the energetically unfavourable oxidation of succinate during syntrophic propionate oxidation since (1) cytochrome b was reduced by succinate and (2) succinate oxidation was similarly inhibited by HOQNO as fumarate reduction.     

Survival during exposure to the electrophilic reagent N-ethylmaleimide in Escherichia coli: role of KefB and KefC potassium channels

On the basis of DNA-DNA hybridization data, nine intestinal spirochete strains were grouped into five genospecies. Three of these genospecies were previously recognized Serpulina species, Serpulina hyodysenteriae (type strain, B78), Serpulina innocens (type strain, B256), and Serpulina pilosicoli (type strain, P43/6/78; previously "Anguillina coli"). The other two genospecies were found to be new Serpulina species, for which we propose the names Serpulina intermedia sp. nov. (with type strain PWS/A) and Serpulina murdochii sp. nov. (with type strain 56-150). S. intermedia and S. murdochii cells had a typical spirochete ultrastructure with 22 to 28 periplasmic flagella per cell. Various soluble sugars were growth substrates for S. intermedia and S. murdochii. During growth in basal heart infusion broth supplemented with fetal calf serum beneath an O2-N2 (1:99) atmosphere, cells of these new species consumed oxygen and glucose and produced H2, CO2, acetate, butyrate, and ethanol. The G + C content of the DNA of S. murdochii 56-150T was 27 mol%, and the G + C content of the DNA of S. intermedia PWS/AT was 25 mol%. In addition, a restriction fragment length polymorphism-PCR assay for the detection of intestinal spirochetes was developed. The assay was based on generation and restriction endonuclease analysis (with HinfI, TaqI, Sau3A, and MboII) of a 558-bp amplicon of ribosomal DNA (rDNA) encoding 16S rRNA. The PCR amplification was specific for Serpulina species and Brachyspira aalborgi. Four restriction digest patterns were found for the five Serpulina species. HinfI restriction differentiated S. murdochii and S. innocens from the other species. Sau3A and TaqI restrictions gave unique fragment patterns for S. murdochii and S. pilosicoli, respectively. S. hyodysenteriae and S. intermedia DNAs gave the same fragment pattern regardless of the enzyme tested. B. aalborgi was differentiated from the Serpulina species by MboII digestion of the 16S rDNA amplicon.     

Thermotoga hypogea sp. nov., a xylanolytic, thermophilic bacterium from an oil-producing well

A new thermophilic, xylanolytic, strictly anaerobic, rod-shaped bacterium, strain SEBR 7054T, was isolated from an African oil-producing well. Based on the presence of an outer sheath (toga) and 16S rRNA sequence analysis data, this organism was identified as a member of the genus Thermotoga. Strain SEBR 7054T possessed lateral flagella, had a G + C content of 50 mol%, produced traces of ethanol from glucose but no lactate, and grew optimally in the presence of 0 to 0.2% NaCl at 70 degrees C. Its phenotypic and phylogenetic characteristics clearly differed from those reported for the five previously validly described Thermotoga species. Therefore, we propose that strain SEBR 7054T is a member of a new species of the genus Thermotoga, Thermotoga hypogea sp. nov. The type strain of T. hypogea is SEBR 7054 (= DSM 11164).     

Microbial diversity in a hydrocarbon- and chlorinated-solvent-contaminated aquifer undergoing intrinsic bioremediation

A culture-independent molecular phylogenetic approach was used to survey constituents of microbial communities associated with an aquifer contaminated with hydrocarbons (mainly jet fuel) and chlorinated solvents undergoing intrinsic bioremediation. Samples were obtained from three redox zones: methanogenic, methanogenic-sulfate reducing, and iron or sulfate reducing. Small-subunit rRNA genes were amplified directly from aquifer material DNA by PCR with universally conserved or Bacteria- or Archaea-specific primers and were cloned. A total of 812 clones were screened by restriction fragment length polymorphisms (RFLP), approximately 50% of which were unique. All RFLP types that occurred more than once in the libraries, as well as many of the unique types, were sequenced. A total of 104 (94 bacterial and 10 archaeal) sequence types were determined. Of the 94 bacterial sequence types, 10 have no phylogenetic association with known taxonomic divisions and are phylogenetically grouped in six novel division level groups (candidate divisions WS1 to WS6); 21 belong to four recently described candidate divisions with no cultivated representatives (OP5, OP8, OP10, and OP11); and 63 are phylogenetically associated with 10 well-recognized divisions. The physiology of two particularly abundant sequence types obtained from the methanogenic zone could be inferred from their phylogenetic association with groups of microorganisms with a consistent phenotype. One of these sequence types is associated with the genus Syntrophus; Syntrophus spp. produce energy from the anaerobic oxidation of organic acids, with the production of acetate and hydrogen. The organism represented by the other sequence type is closely related to Methanosaeta spp., which are known to be capable of energy generation only through aceticlastic methanogenesis. We hypothesize, therefore, that the terminal step of hydrocarbon degradation in the methanogenic zone of the aquifer is aceticlastic methanogenesis and that the microorganisms represented by these two sequence types occur in syntrophic association.     

Characterization of Eubacterium coprostanoligenes sp. nov., a cholesterol-reducing anaerobe

A small, anaerobic, gram-positive coccobacillus that reduces cholesterol to coprostanol was isolated from a hog sewage lagoon. This isolate, strain HLT (T = type strain) does not require cholesterol for growth, but it requires lecithin and has phospholipase activity. Much acid is produced by the fermentation of amygdalin, lactose, and salicin. Arabinose, cellobiose, fructose, glucose, mannose, and melibiose are fermented weakly. Acetic, formic, and succinic acids are produced, as is hydrogen. The isolate does not reduce nitrate, produce indole, or hydrolyze starch and gelatin. Esculin is hydrolyzed. The properties of strain HLT are most similar to those of members of the genus Eubacterium. Because strain HL (= ATCC 51222) has unique morphological and physiological properties, we propose that it should be the type strain of a new species in the genus Eubacterium, Eubacterium coprostanoligenes.     

Hymenobacter roseosalivarius gen. nov., sp. nov. from continental Antartica soils and sandstone: bacteria of the Cytophaga/Flavobacterium/Bacteroides line of phylogenetic descent

Aseptically collected sandstone and soil samples from the antarctic Dry Valleys were inoculated into oligotrophic media and incubated under low light intensities. A total of 41 Gram-negative isolates were obtained with reddish colonies spreading on agar. A sandstone isolate and four soil strains were characterized further. They were nearly identical in morphological, physiological, biochemical and chemotaxonomic properties. They produced large amounts of extracellular polymer and utilized for growth: glucose, saccharose, mannitol, sorbitol, L-aspartate, malate and acetate, but not D-ribose, adonitol, DL-alanine, glutamate, glycolate, lactate or succinate. All strains hydrolyzed gelatin, starch, casein, xylan, Tweens 80 or 60 and dead or living yeast cells, but not cellulose or pectin. Nitrate was not reduced, ethanol was not oxidized and acid was not produced from maltose, mannitol or dulcitol. Ammonia was not produced from peptone. They were strictly aerobic. Major fatty acids were n 16:1 d 9, n 16:1 d 11, n 17:1 d 11, and i 15:0. The strains contained the quinone MK-7 and phosphatidylethanolamine as the main phospholipid. The base ratio ranged from 55 to 61 mol% G+C. A 16S rRNA sequence analysis of strains AA-688 and AA-718 showed these to be identical and to represent a special phylogenetic group within the Cytophaga/Flavobacterium/Bacteroides major line of descent. Three soil strains labeled "Taxeobacter" Txc1, Txg1, and Txo1 (Reichenbach, 1992) belonged to the same group but had lower sequence similarities (<95%). Some of their characteristics were different from those of the antarctic strains: the utilization of C-compounds, hydrolysis of polymers, temperature tolerances, major fatty acids and base ratios. Txc1 and Txg1 may later have to be considered as members of this group, possibly on the species level, while Txo1 could represent a different related genus. It is concluded that the five antarctic strains represent a new genus and species for which the name of Hymenobacter roseosalivarius is proposed. The type strain is AA-718T (DSM 11622T).     

Impact of Initial pH and Linoleic Acid (C18:2) on Hydrogen Production by a Mesophilic Anaerobic Mixed Culture

Hydrogen production from glucose using a mixed anaerobic culture was assessed under batch conditions by adjusting the initial pH and adding linoleic acid (LA). At an initial pH of 5.0, hydrogen (1.9?mol?H2?mol?1 glucose) was detected after the first glucose injection in the controls (no LA added). At the latter initial pH and in cultures fed 2,000?mg?l?1 LA, the yield reached a maximum of 2.4?mol?H2?mol?1 glucose when glucose was injected again. Hydrogen was detected after the second glucose injection in cultures with the initial pH adjusted to 5.0 and 6.0. In cultures receiving LA and adjusted to pH 7.6, the hydrogen yield reached 1.4?mol?H2?mol?1 glucose when glucose was injected again. Acetate, propionate, and butyrate were detected under all conditions; however, the quantities were variable and dependent on the conditions examined. In comparison to the amount of volatile fatty acids produced, relatively low quantities of alcohols (ethanol, i-propanol, n-butanol, and i-butanol) were detected during the initial lag phase of 96?to?120?h.     

Apoptosis in colorectal tumour cells: induction by the short chain fatty acids butyrate, propionate and acetate and by the bile salt deoxycholate

The short chain fatty acids acetate, propionate and butyrate are produced when dietary fibre is fermented by the colonic bacteria. We have previously shown that sodium butyrate induces apoptosis in 3 colorectal tumour cell lines. We have extended our study to 3 adenoma and 4 carcinoma cell lines and investigated whether propionate and acetate also induce apoptosis. All 3 short chain fatty acids induced apoptosis at physiological concentrations, but of the 3, butyrate was the most effective. Since these fatty acids are produced as a result of bacterial fermentation of dietary fibre, this may in part explain the correlation between a high-fibre diet and low colorectal cancer incidence. Sodium butyrate induced apoptosis in all 7 of the cell lines studied; however, 2 of the 4 carcinoma cell lines (PC/JW/FI and S/KS/FI) were more resistant to butyrate-induced apoptosis than the 3 adenoma cell lines, suggesting that at least some carcinomas may evolve mechanisms to protect the cells from the induction of apoptosis. The bile acid deoxycholic acid has previously been reported as a possible tumour promoter in the large intestine and its levels are reduced by dietary fibre. Concentrations of between 10 nM and 0.1 mM had no effect on either the proliferation or apoptosis of colonic tumour cells in vitro. However, a significant induction of apoptosis was obtained at a concentration of 0.5 mM. These results may have significance for the aetiology of colorectal cancer.     

Some properties of a novel obligately autotrophic iron-oxidizing bacterium isolated from seawater

An iron-oxidizing bacterium obligately requiring NaCl for growth was isolated from seawater in Seto Inland Sea, Japan, and designated as strain KU2-11. Strain KU2-11 was a Gram negative, non-spore-forming and rod-shaped bacterium, and can grow autotrophically by using ferrous ion and elemental sulfur as sole energy sources. The optimum growth pH and temperature were 2 and 30°C, respectively. The G+C content of the DNA was 59 mol%. The bacterium could not grow in the medium without NaCl and obligately required NaCl for growth. The optimum NaCl concentration for the growth was 2%. Strain KU2-11 seemed to be identified as a member of Thiobacillus ferrooxidans on the basis of morphological and physiological properties. However, the phylogenetic analysis based on 16S rDNA gene sequences indicated that strain KU2-11 is distinct from T. ferrooxidans. Iron- and sulfur-oxidizing activity of the bacterium were not detected in a reaction mixture without NaCl, and depended on the presence of NaCl. The optimum NaCl concentrations for the iron- and sulfur-oxidizing activities were 2–4% and 1%, respectively. On the basis of the phenotypic characteristics of strain KU2-11 and its phylogenetic position, we suggested that this bacterium should be placed in a new species of the genus Thiobacillus.     

A freshwater anaerobe coupling acetate oxidation to tetrachloroethylene dehalogenation

Strain TT4B has been isolated from anaerobic sediments known to be contaminated with a variety of organic solvents. It is a gram-negative, rod-shaped bacterium and grew anaerobically with acetate as the electron donor and tetrachloroethylene as the electron acceptor in a mineral medium. cis-Dichloroethylene was the halogenated product. This strain did not grow fermentatively and used only acetate or pyruvate as electron donors. Tetrachloroethylene and trichloroethylene were used as electron acceptors, as were ferric nitriloacetate and fumarate. Nitrogen and sulfur oxyanions were not able to substitute as the electron acceptor for this organism. Modest growth occurred in a two-phase system with 1 ml of hexadecane containing 50 to 200 mM tetrachloroethylene (aqueous concentrations, 25 to 100 microM) and 10 ml of anaerobic mineral solution with Na2S as the reducing agent. Growth was completely inhibited at tetrachloroethylene levels above 100 microM.     

A periplasmic and extracellular c-type cytochrome of Geobacter sulfurreducens acts as a ferric iron reductase and as an electron carrier to other acceptors or to partner bacteria

An extracellular electron carrier excreted into the growth medium by cells of Geobacter sulfurreducens was identified as a c-type cytochrome. The cytochrome was found to be distributed in about equal amounts in the membrane fraction, the periplasmic space, and the surrounding medium during all phases of growth with acetate plus fumarate. It was isolated from periplasmic preparations and purified to homogeneity by cation-exchange chromatography, gel filtration, and hydrophobic interaction chromatography. The electrophoretically homogeneous cytochrome had a molecular mass of 9.57 +/- 0.02 kDa and exhibited in its reduced state absorption maxima at wavelengths of 552, 522, and 419 nm. The midpoint redox potential determined by redox titration was -0.167 V. With respect to molecular mass, redox properties, and molecular features, this cytochrome exhibited its highest similarity to the cytochromes c of Desulfovibrio salexigens and Desulfuromonas acetoxidans. The G. sulfurreducens cytochrome c reduced ferrihydrite (Fe(OH)3), Fe(III) nitrilotriacetic acid, Fe(III) citrate, and manganese dioxide at high rates. Elemental sulfur, anthraquinone disulfonate, and humic acids were reduced more slowly. G. sulfurreducens reduced the cytochrome with acetate as an electron donor and oxidized it with fumarate. Wolinella succinogenes was able to reduce externally provided cytochrome c of G. sulfurreducens with molecular hydrogen or formate as an electron donor and oxidized it with fumarate or nitrate as an electron acceptor. A coculture could be established in which G. sulfurreducens reduced the cytochrome with acetate, and the reduced cytochrome was reoxidized by W. succinogenes in the presence of nitrate. We conclude that this cytochrome can act as iron(III) reductase for electron transfer to insoluble iron hydroxides or to sulfur, manganese dioxide, or other oxidized compounds, and it can transfer electrons to partner bacteria.