Thiorhodococcus minus, gen. nov., sp. nov., a new purple sulfur bacterium isolated from coastal lagoon sediments

A new marine phototrophic purple sulfur bacterium (strain CE2203) was isolated in pure culture from a man-made coastal lagoon located on the Atlantic coast (Arcachon Bay, France). Single cells were coccus-shaped, did not contain gas vesicles, and were highly motile. Intracellular photosynthetic membranes were of the vesicular type. Bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series were present as photosynthetic pigments. Hydrogen sulfide, thiosulfate, elemental sulfur, and molecular hydrogen were used as electron donors during photolithotrophic growth under anoxic conditions, while carbon dioxide was utilized as carbon source. Acetate, propionate, lactate, glycolate, pyruvate, fumarate, succinate, fructose, sucrose, ethanol, and propanol were photoassimilated in the presence of hydrogen sulfide. During growth on sulfide, elemental sulfur globules were stored inside the cells. Chemotrophic growth under microoxic conditions in the dark was possible. The DNA base composition was 66.9 mol% G+C. Comparative sequence analysis of the 16S rRNA gene confirmed the membership of strain CE2203 in the family Chromatiaceae. Morphological characteristics of strain CE2203 indicated a close affiliation to the genera Thiocystis and Thiocapsa. However, the phylogenetic treeing revealed no closer relationship to Thiocystis spp. than to Thiocapsa roseopersicina or other known members of the Chromatiaceae. Consequently, strain CE2203 is proposed as the type strain of a new genus and species, Thiorhodococcus minus gen. nov., sp. nov. Received: 23 December 1996 / Accepted: 27 March 1997     

Characterization of a new platelet-forming purple sulfur bacterium,Amoebobacter pedioformis sp. nov.

The dominant purple sulfur bacterium of a reddish-colored waste water pond near Taichung, Taiwan, was isolated in pure culture, strain CML2. Individual cells were nearly spherical, nonmotile, and contained in their peripheral parts was vacuoles that appeared like elongated, curved tubes. Four to sixteen cells formed platelet-like aggregates reminiscent of Thiopedia rosea. The intracellular photosynthetic membrane system of the cells was of vesicular type; the photosynthetic pigments consisted of bacteriochlorophyll a and spirilloxanthin as the major carotenoid. The color of cell suspensions was pink to rosered. Under anaerobic conditions photolithoautotrophic growth occurred with sulfide, elemental sulfur or thiosulfate; sulfur globules were stored as an intermediary oxidation product. In the presence of sulfide, acetate, lactate and pyruvate were photoassimilated; strain CML2 lacked assimilatory sulfate reduction. Fastest photoautotrophic growth (11 h doubling time) was obtained at pH 7.5, 35°C and a light intensity of about 1000 lux (tungsten lamp). Chemolithoautotrophic growth in the dark was possible under reduced oxygen partial pressure with reduced sulfur compounds as respiratory substrates. The DNA base composition of strain CML2 was 65.5 mol% G+C. Strain CML2 is described as type strain of a new species, Amoebobacter pedioformis sp. nov., in the family Chromatiaceae.     

含奥氏酮嗜盐紫色硫细菌的分离鉴定及系统发育分析

[目的]为挖掘我国紫色硫细菌物种和光合蛋白基因资源.[方法]采用Pfennig紫色硫细菌无机选择性培养基和琼脂稀释法.[结果]从青岛东风盐场分离获得一株含奥氏酮、耐高浓度硫化物、嗜盐耐碱紫色硫细菌菌株283-1.该菌株能氧化硫化物产生硫粒储存在细胞内、嗜盐、细胞含有奥氏酮类胡萝卜素、细菌叶绿素a强吸收峰位于830 nm处、运动、不产生气囊,表明属于Marichromatium属.16S rDNA序列同源性比较和系统发育分析也表明这一点.但该菌株能在1%～15%NaCl、7.5 mmol/L 高浓度硫化物、45℃、5000lux、pH9.0条件下生长良好,能很好的光同化C3和C4有机酸和葡萄糖酸钠等特性,与Marichromatium属4个种有明显不同.[结论]菌株283-1是Marichromatium属一个新分离物,编号 Marichromatium sp.283-1.     

Rhodovulum phaeolacus sp. nov. a phototrophic alphaproteobacterium isolated from a brown pond

Two strains of oval-rod shaped, Gram-negative, phototrophic, purple non-sulfur bacteria designated JA580(T) and JA595 were isolated from a sediment sample collected from a brown pond. Strain JA580(T) was designated as the type strain, while strain JA595 as an additional strain has similar characteristics to the type strain. Strain JA580(T) was non-motile and grew photoheterotrophically with a number of organic compounds serving as carbon source/electron donor. Intracellular photosynthetic membranes were of the vesicular type. Bacteriochlorophyll a and carotenoids of the spheroidene series were present as the major photosynthetic pigments. Strain JA580(T) requires yeast extract for growth. Strain JA580(T) has an obligate requirement for sulfide or thiosulfate for growth. C(18:1)ω7c, C(18:0), C(18:1)ω9c were the predominant components of cellular fatty acids. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA580(T) clustered with species of the genus Rhodovulum of the family Rhodobacteraceae and is most closely related to the type strains of Rhodovulum adriaticum, Rhodovulum iodosum (96.5%), Rhodovulum robiginosum (96%), Rhodovulum imhoffii (95.6%) and other members of the genus Rhodovulum (<95%). On the basis of phenotypic and molecular genetic evidence, it is proposed that strain JA580(T) should be classified as a novel species of the genus Rhodovulum of the family Rhodobacteraceae, with the species name Rhodovulum phaeolacus sp. nov. The type strain of the species is JA580(T) (=NBRC 107612(T) =KCTC 5963(T)).     

<Emphasis Type="Italic">Desulfurispirillum alkaliphilum</Emphasis> gen. nov. sp. nov., a novel obligately anaerobic sulfur- and dissimilatory nitrate-reducing bacterium from a full-scale sulfide-removing bioreactor

Strain SR 1^T was isolated under anaerobic conditions using elemental sulfur as electron acceptor and acetate as carbon and energy source from the Thiopaq bioreactor in Eerbeek (The Netherlands), which is removing H₂S from biogas by oxidation to elemental sulfur under oxygen-limiting and moderately haloalkaline conditions. The bacterium is obligately anaerobic, using elemental sulfur, nitrate and fumarate as electron acceptors. Elemental sulfur is reduced to sulfide through intermediate polysulfide, while nitrate is dissimilatory reduced to ammonium. Furthermore, in the presence of nitrate, strain SR 1^T was able to oxidize limited amounts of sulfide to elemental sulfur during anaerobic growth with acetate. The new isolate is mesophilic and belongs to moderate haloalkaliphiles, with a pH range for growth (on acetate and nitrate) from 7.5 to 10.25 (optimum 9.0), and a salt range from 0.1 to 2.5 M Na⁺ (optimum 0.4 M). According to phylogenetic analysis, SR 1^T is a member of a deep bacterial lineage, distantly related to Chrysiogenes arsenatis (Macy et al. 1996). On the basis of the phenotypic and genetic data, the novel isolate is placed into a new genus and species, Desulfurispirillum alkaliphilum (type strain SR^T = DSM 18275 = UNIQEM U250). Nucleotide sequence accession number: the GenBank/EMBL accession number of the 16S rRNA gene sequence of strain SR 1^T is DQ666683.     

Selective enrichment and characterization of Roseospirillum parvum, gen. nov. and sp. nov., a new purple nonsulfur bacterium with unusual light absorption properties

A new type of phototrophic purple bacterium, strain 930I, was isolated from a microbial mat covering intertidal sandy sediments of Great Sippewissett Salt Marsh (Woods Hole, Mass., USA). The bacterium could only be enriched at a wavelength of 932 (± 10) nm. Cells were vibrioid- to spirilloid-shaped and motile by means of bipolar monotrichous flagellation. The intracytoplasmic membranes were of the lamellar type. Photosynthetic pigments comprised bacteriochlorophyll a and the carotenoids spirilloxanthin and lycopenal. The isolated strain exhibited an unusual, long-wavelength absorption maximum at 911 nm. Sulfide or thiosulfate served as electron donor for anoxygenic phototrophic growth. During growth on sulfide, elemental sulfur globules formed outside the cells. Elemental sulfur could not be further oxidized to sulfate. In the presence of sulfide plus bicarbonate, fructose, acetate, propionate, butyrate, valerate, 2-oxoglutarate, pyruvate, lactate, malate, succinate, fumarate, malonate, casamino acids, yeast extract, L(+)-alanine, and L(+)-glutamate were assimilated. Sulfide, thiosulfate, or elemental sulfur served as a reduced sulfur source for photosynthetic growth. Maximum growth rates were obtained at pH 7.9, 30 °C, 50 μmol quanta m^–2 s^–1 of daylight fluorescent tubes, and a salinity of 1–2% NaCl. The strain grew microaerophilically in the dark at a partial pressure of 1 kPa O₂. The DNA base composition was 71.2 mol% G + C. Sequence comparison of 16S rRNA genes indicated that the isolate is a member of the α-Proteobacteria and is most closely related to Rhodobium orientis at a similarity level of 93.5%. Because of the large phylogenetic distance to known phototrophic species of the α-Proteobacteria and of its unique absorption spectrum, strain 930I is described as a new genus and species, Roseospirillum parvum gen. nov. and sp. nov. Received: 29 December 1998 / Accepted: 17 March 1999     

Rhabdochromatium marinum gen. nom. rev., sp. nov., a purple sulfur bacterium from a salt marsh microbial mat

A new purple sulfur bacterium was isolated in pure culture (strain 8315) from a laminated microbial mat at Great Sippewissett Salt Marsh, Cape Cod, Mass., USA. Single cells were large rods, 10–20 times longer than wide, and predominantly strainght with slightly conical ends. Cells were motile by polarly inserted flagellar tufts. Intracellular photosynthetic membranes were of the vesicular-type. Photosynthetic pigments were bacteriochlorophylla and the carotenoids lycopene, rhodovibrin, anhydrorhodovibrin, and rhodopin. The new bacterium was strictly anaerobic and obligately phototrophic. Hydrogen, hydrogen sulfide, elemental sulfur, and thiosulfate were used as electron donors for photoautotrophic growth. In sulfide-reduced, bicarbonate-containing media, acetate, propionate, and pyruvate were photoassimilated. Growth factors were not required. Optimum growth rates were obtained at pH 7.3, 30°C, a salinity of 1.5–5.0% NaCl, and a light intensity of about 500 lx (tungsten lamp). The DNA base composition of strain 8315 was 60.4 mol% G+C. Comparison of 16S rDNA oligonucleotide catalogue data showed that the new bacterium must be considered a new genus of the Chromatiaceae. The nameRhabdochromatium is revived, and the new speciesRhabdochromatium marinum sp. nov. is described.     

Alkaliphilic heliobacterium Heliorestis baculata sp. nov. and emended description of the genus Heliorestis

A rod-shaped heliobacterium motile by peritrichous flagella, designated strain OS-H1, was isolated from a sample of shoreline soil of the soda lake Ostozhe (pH 9.2, total salt content 0.22%) located in the steppe of south-east Siberia. In the first few transfers, the isolate produced heat-resistant endospores. Like other heliobacteria, strain OS-H1 contained bacteriochlorophyll g and lacked intracytoplasmic membranes. The new isolate was a strict anaerobe and photoheterotroph. In the light and in the presence of organic compounds, strain OS-H1 oxidized sulfide to elemental sulfur and polysulfides, but was not capable of photoautotrophic growth. The isolate was an obligate alkaliphile able to grow at pH 8-10.2. The best growth was observed at pH 8.5-9.5, a temperature of 30 degrees C and at 5-10 g sodium carbonate l(-1). Biotin was required as a growth factor. The G+C content of strain OS-H1 was 45.0 mol%. Comparison of the 16S rRNA gene sequence to that of phototrophic bacteria showed strain OS-H1 to group within gram-positive bacteria of the family Heliobacteriaceae with the closest relationship to Heliorestis daurensis (95.6% similarity). Based on physiological, genetic and chemotaxonomic characteristics, the new heliobacterium is described as a new species of the genus Heliorestis, Heliorestis baculata.     

<Emphasis Type="Italic">Thiocapsa imhoffii</Emphasis>, sp. nov., an alkaliphilic purple sulfur bacterium of the family <Emphasis Type="Italic">Chromatiaceae</Emphasis> from Soap Lake,Washington (USA)

An alkaliphilic purple sulfur bacterium, strain SC5, was isolated from Soap Lake, a soda lake located in east central Washington state (USA). Cells of strain SC5 were gram-negative, non-motile, and non-gas vesiculate cocci, often observed in pairs or tetrads. In the presence of sulfide, elemental sulfur was deposited internally. Liquid cultures were pink to rose red in color. Cells contained bacteriochlorophyll a and spirilloxanthin as major photosynthetic pigments. Internal photosynthetic membranes were of the vesicular type. Optimal growth of strain SC5 occurred in the absence of NaCl (range 0–4%), pH 8.5 (range pH 7.5–9.5), and 32°C. Photoheterotrophic growth occurred in the presence of sulfide or thiosulfate with only a limited number of organic carbon sources. Growth factors were not required, and cells could fix N₂. Dark, microaerobic growth occurred in the presence of both an organic carbon source and thiosulfate. Sulfide and thiosulfate served as electron donors for photoautotrophy, which required elevated levels of CO₂. Phylogenetic analysis placed strain SC5 basal to the clade of the genus Thiocapsa in the family Chromatiaceae with a 96.7% sequence similarity to its closest relative, Thiocapsa roseopersicina strain 1711^T (DSM217^T). The unique assemblage of physiological and phylogenetic properties of strain SC5 defines it as a new species of the genus Thiocapsa, and we describe strain SC5 herein as Tca. imhoffii, sp. nov.     

Heterotrophic sulfur reduction by Thermotoga sp. strain FjSS3.B1

Thermotoga sp. strain FjSS3.B1 was able to reduce sulfur to sulfide when grown on a mineral medium with glucose as the sole carbon and energy source. There was no increase in specific growth yield coupled to sulfur reduction, but the specific growth rate, final growth yield, and tolerance of H2 were all increased in the presence of sulfur. At dissolved H2 concentrations, of 550 to 600 mumol/l (at 77 degrees C) growth was not possible unless sulfur was added. Glucose was fermented via the Embden-Meyerhof-Parnas pathway to lactate, acetate, H2 and CO2 (and other unidentified minor products). The thermodynamic problems associated with the relatively high redox potential electrons from the 1,3-bisphosphoglycerate/glyceraldehyde 3-phosphate couple (E'0 = -350 mV) are overcome by reducing sulfur to sulfide (E'0 = -270 mV) rather than the energetically unfavourable production of H2 (E'0 = -414 mV). Under high hydrogen partial pressures there was increased production of lactate as an alternative electron sink. The results indicate that sulfur reduction operates primarily as an electron sink rather than as a detoxification reaction or energy-generating mechanism.     

Description of Ectothiorhodospira salini sp. nov

Strain JA430(T) is a Gram-negative, vibrioid to spiral shaped phototrophic purple sulfur bacterium isolated from anoxic sediment of a saltern at Kanyakumari in a mineral salts medium that contained 2% NaCl (w/v). Strain JA430(T) grows optimally at 5-6% NaCl and tolerates up to 12% NaCl. Intracellular photosynthetic membranes were of the lamellar type. Bacteriochlorophyll a and carotenoids of the spirilloxanthin series are present as photosynthetic pigments. Major cellular fatty acids are C(18:1)ω7c, C(16:0), C(19:0)cycloω8c and C(16:1)ω7c/C(16:1)ω6c. Strain JA430(T) exhibits photoorganoheterotrophy and chemoorganoheterotrophy and requires para-aminobenzoic acid, pantothenate and pyridoxal phosphate for growth. Phylogenetic analysis on the basis of 16S rRNA gene sequence analysis showed that strain JA430(T) forms monophyletic group in the genus Ectothiorhodospira. The highest sequence similarity for strain JA430(T) was found with the type strains of Ectothiorhodospira variabilis DSM 21381(T) (96.1%) and Ectothiorhodospira haloalkaliphila ATCC 51935(T) (96.2%). Morphological and physiological characteristics discriminate strain JA430(T) from other species of the genus Ectothiorhodospira, for which we describe this as a novel species, Ectothiorhodospira salini sp. nov. ( = NBRC 105915(T) = KCTC 5805(T)).     

Ectothiorhodosinus mongolicum gen. nov., sp. nov.,--a new purple sulfur bacterium from soda lake in Mongolia

A new purple sulfur bacterium (strain M9) was isolated from the steppe soda Lake Dzun Uldziin Nur (pH 9.4; mineralization, 3.3%) situated in southeastern Mongolia. Individual cells appear as vibrios 0.3-0.5 x 0.7-1 micron in size. The dividing cells often do not separate from each other, forming an almost closed ring. The internal photosynthetic membranes are represented by concentric lamellae lining the cell wall. Photosynthetic pigments are bacteriochlorophyll a and carotenoids of the spirilloxanthin series. The main carotenoid (> 96%) is spirilloxanthin. Two typical light-harvesting complexes (LH1 and LH2) are present in the membranes in a 1:1 ratio. The bacterium is an anaerobe and facultative photoorganoheterotroph. Photolithoautotrophic growth on sulfide is scarce. Thiosulfate is utilized as an electron donor only in the presence of organic matter. Globules of elemental sulfur are formed as an intermediary product of sulfide and thiosulfate oxidation and are deposited outside the cells. The end product of oxidation is sulfate. In the presence of sulfide and carbonates, acetate, lactate, malate, pyruvate, propionate, succinate, and fumarate are used as the additional sources of carbon in anoxygenic photosynthesis. Vitamin are not required. The bacterium is an alkaliphile the pH optimum is at 8.3-9.1, the pH range is 7.6-10.1. The optimum NaCl concentration in the medium is 1 to 7%; the range is 0.5 to 0.9%. The optimum carbonate content in the medium is 2%; the range is 1 to 10%. The best growth occurs at 30-35 degrees C. The DNA G + C content is 57.5 mol%. According to the results of analysis of the 16S rRNA gene sequences, the new isolate M9 belongs to the phylogenetic cluster containing representatives of the family Ectothiorhodospiraceae within the class "Gammaproteobacteria." In this class, the new isolate forms a new branch, which occupies an intermediate position between the representatives of the genera Ectothiorhodospira and Thiorhodospira. Based on the phenotypic and genetic characteristics, the new purple sulfurbacterium was assigned to a new species of a new genus of the family Ectothiorhodospiraceae, Ectothiorhodosinus mongolicum gen. nov., sp. nov.     

Clostridium tunisiense sp. nov., a new proteolytic, sulfur-reducing bacterium isolated from an olive mill wastewater contaminated by phosphogypse

A new sporulated fermentative bacterium designated strain E1(T) (T=type strain), was isolated from an anaerobic mud of an olive mill wastewater basin contaminated by phosphogypse produced by a Tunisian factory. Strain E1(T) was a motile Gram-positive slightly curved rod with spherical terminal spore swelling the cell. It grew between 18 degrees C and 43 degrees C with an optimum at 37 degrees C and pH 7.8 (range 5.5-8.7), without NaCl (range 0-3%). Strain E1(T) was a chemoorganotrophic anaerobic bacterium fermenting only proteins and amino acids. Yeast extract was required for growth. Elemental sulfur was used as terminal electron acceptor. The G+C content of the DNA was 32.6 mol%. The closest phylogenetical relatives of strain E1(T) were Clostridium thiosulfatireducens and C. subterminale (97.3% similarity for partial rRNA gene sequences). DNA-DNA hybridization values between strain E1(T) and both species were 17% and 20.8%, respectively. On the basis of differences in genotypic and phenotypic characteristics, strain E1(T) (DSM 15206(T), CIP 107666(T)) is proposed as the type strain of a new species, C. tunisiense sp. nov. GenBank accession number for the 16S rRNA gene sequence of strain E1(T) is AY187622.     

腾冲热海一株嗜酸热硫化叶菌的分离与鉴定

从云南腾冲热海酸性温泉中分离纯化出一株极端嗜酸热菌株K4-1,并对其进行形态观察、生长特征、碳源和能源利用及16S rRNA基因分析.该菌株细胞形态为不规则球形,有单生鞭毛,严格好氧,兼性自养,能利用元素硫作为能源,也能利用酵母膏、精氨酸或核糖作为碳源和能源.其最适生长温度为75℃,最适pH为3.5.通过16S rRNA基因序列相似性对比对该菌株进行鉴定,结果表明该菌株与硫化叶茵属标准菌株的相似性介于86.6%～94.3%之间,与分离自腾冲热海的腾冲硫化叶菌Sulfolobus tengchongensis RT8-4菌株序列相似性最高,达到98.9%,可将菌株K4-1鉴定为硫化叶菌属菌株.菌株K4-1的16S rRNA基因序列号为EU729124.     

<Emphasis Type="Italic">Thermosulfurimonas marina</Emphasis> sp. nov., an Autotrophic Sulfur-Disproportionating and Nitrate-Reducing Bacterium Isolated from a Shallow-Sea Hydrothermal Vent

A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain SU872^T) was isolated from a shallow-sea hydrothermal vent at Kunashir Island. The cells were motile, gram-negative, oval or rodshaped 0.5?0.6 μm thick and 1.5?2.0 μm long, occurring singly or in pairs. Strain SU872^T grew at 50 to 79°C (optimum at 74°C), pH from 5.0 to 8.0 (optimum at 6.7?7.0), and NaCl concentration of 1.5–4.5%. Strain SU872^T was able to grow by disproportionation of elemental sulfur, thiosulfate, or sulfite, with CO₂/HCO₃^? as the sole carbon source. Growth was enhanced in the presence of ferrihydrite (poorly crystalline Fe(III) oxide) as as a sulfide-scavenging agent. Sulfate was not used as an electron acceptor. Growth also occurred with elemental sulfur, thiosulfate, or sulfite (but not sulfide) as electron donors and nitrate as an electron acceptor, with production of sulfate and ammonium. Analysis of the 16S rRNA gene sequence revealed 97.8% similarity between strain SU872^T and the type strain Thermosulfurimonas dismutans S95^T (phylum Thermodesulfobacteria). According to the results of DNA–DNA hybridization, the similarity of genomic DNA of the strains SU872^T and T. dismutans S95^T was 48%. Based on its phenotypic characteristics and the results of phylogenetic analysis, it is proposed to assign the isolate to a new species of the genus Thermosulfurimonas,—Thermosulfurimonas marina sp. nov., with the type strain SU872^T (=DSM 104922^T, =VKM B-3177^T, =UNIQEM SU872^T).     

Haloalkaliphilic spore-forming sulfidogens from soda lake sediments and description of Desulfitispora alkaliphila gen. nov., sp. nov.

An anaerobic enrichment with pyruvate as electron donor and thiosulfate at pH 10 and 0.6 M Na⁺ inoculated with pasteurized soda lake sediments resulted in a sulfidogenic coculture of two morphotypes of obligately anaerobic haloalkaliphilic endospore-forming clostridia, which were further isolated in pure culture. Strain AHT16 was a thin long rod able to ferment sugars and pyruvate and to respire H₂, formate and pyruvate using thiosulfate and fumarate as electron acceptors and growing optimally at pH 9.5. Thiosulfate was reduced incompletely to sulfide and sulfite. The strain was closely related (99% sequence similarity) to a peptolytic alkaliphilic clostridium Natronincola peptidovorans. Strain AHT17 was a short rod with a restricted respiratory metabolism, growing with pyruvate and lactate as electron donor and sulfite, thiosulfate and elemental sulfur as electron acceptors with a pH optimum 9.5. Thiosulfate was reduced completely via sulfite to sulfide. The ability of AHT17 to use sulfite explained the stability of the original coculture of the two clostridia—one member forming sulfite from thiosulfate and another consuming it. Strain AHT17 formed an independent deep phylogenetic lineage within the Clostridiales and is proposed as a new genus and species Desulfitisporum alkaliphilum gen. nov., sp. nov. (=DSM 22410^T = UNIQEM U794^T).     

Use of Reduced Sulfur Compounds by Beggiatoa spp.: Enzymology and Physiology of Marine and Freshwater Strains in Homogeneous and Gradient Cultures

The marine Beggiatoa strains MS-81-6 and MS-81-1c are filamentous, gliding, colorless sulfur bacteria. They have traditionally been cultured in very limited quantities in sulfide gradient media, where they grow as chemolithoautotrophs, forming a thin horizontal plate well below the air-agar interface. There, the facultatively chemolithoautotrophic strain MS-81-6 quantitatively harvests the flux of sulfide diffusing from below and oxidizes it to sulfate by using oxygen as the electron acceptor. Only recently have these strains been cultivated in bulk in defined liquid media (K. D. Hagen and D. C. Nelson, Appl. Environ. Microbiol. 62:947-953, 1996). In the current study, the obligately chemolithoautotrophic strain MS-81-1c was shown to have, despite much greater storage of elemental sulfur, an apparent Y(infH)(inf(inf2))(infS) twice that of MS-81-6 when the two strains were grown in identical sulfide-limited gradient media. While the basis of this difference in energy conservation has not been established, differences in sulfur oxidation enzymes were noted. Strain MS-81-1c appeared to be able to oxidize sulfite by using either the adenosine phosphosulfate (APS) pathway or a sulfite:acceptor oxidoreductase. APS pathway enzymes (ATP sulfurylase and APS reductase) were present at relatively high and constant levels regardless of growth conditions, while the sulfite:acceptor oxidoreductase activity varied at least eightfold, with the highest activity produced in sulfide gradient medium. By contrast, strain MS-81-6 showed no detectable activity of the APS pathway enzymes and possessed a sulfite:acceptor oxidoreductase activity just sufficient to account for its observed rate of growth in sulfide gradient medium. Freshwater strain OH-75-2a showed activity and regulation of sulfite:acceptor oxidoreductase consistent with lithotrophic energy conservation, a feature not yet proven for any freshwater Beggiatoa strain.     

Pyrobaculum calidifontis sp. nov., a novel hyperthermophilic archaeon that grows in atmospheric air

A novel, facultatively aerobic, heterotrophic hyperthermophilic archaeon was isolated from a terrestrial hot spring in the Philippines. Cells of the new isolate, strain VA1, were rod-shaped with a length of 1.5 to 10 microm and a width of 0.5 to 1.0 microm. Isolate VA1 grew optimally at 90 to 95 degrees C and pH 7.0 in atmospheric air. Oxygen served as a final electron acceptor under aerobic growth conditions, and vigorous shaking of the medium significantly enhanced growth. Elemental sulfur inhibited cell growth under aerobic growth conditions, whereas thiosulfate stimulated cell growth. Under anaerobic growth conditions, nitrate served as a final electron acceptor, but nitrite or sulfur-containing compounds such as elemental sulfur, thiosulfate, sulfate and sulfite could not act as final electron acceptors. The G+C content of the genomic DNA was 51 mol%. Phylogenetic analysis based on 16S rRNA sequences indicated that strain VA1 exhibited close relationships to species of the genus Pyrobaculum. A DNA-DNA hybridization study revealed a low level of similarity (< or = 18%) between strain VA1 and previously described members of the genus Pyrobaculum. Physiological characteristics also indicated that strain VA1 was distinct from these Pyrobaculum species. Our results indicate that isolate VA1 represents a novel species, named Pyrobaculum calidifontis.     

<Emphasis Type="Italic">Tindallia californiensis</Emphasis> sp. nov., a new anaerobic,haloalkaliphilic, spore-forming acetogen isolated from Mono Lake in California

A novel extremely haloalkaliphilic, strictly anaerobic, acetogenic bacterium strain APO was isolated from sediments of the athalassic, meromictic, alkaline Mono Lake in California. The Gram-positive, spore-forming, slightly curved rods with sizes 0.55-0.7x1.7-3.0 microm were motile by a single laterally attached flagellum. Strain APO was mesophilic (range 10-48 degrees C, optimum of 37 degrees C); halophilic (NaCl range 1-20% (w/v) with optimum of 3-5% (w/v), and alkaliphilic (pH range 8.0-10.5, optimum 9.5). The novel isolate required sodium ions in the medium. Strain APO was an organotroph with a fermentative type of metabolism and used the substrates peptone, bacto-tryptone, casamino acid, yeast extract, l-serine, l-lysine, l-histidine, l-arginine, and pyruvate. The new isolate performed the Stickland reaction with the following amino acid pairs: proline + alanine, glycine + alanine, and tryptophan + valine. The main end product of growth was acetate. High activity of CO dehydrogenase and hydrogenase indicated the presence of a homoacetogenic, non-cycling acetyl-CoA pathway. Strain APO was resistant to kanamycin but sensitive to chloramphenicol, tetracycline, and gentamycin. The G+C content of the genomic DNA was 44.4 mol% (by HPLC method). The sequence of the 16S rRNA gene of strain APO possessed 98.2% similarity with the sequence from Tindallia magadiensis Z-7934, but the DNA-DNA hybridization value between these organisms was only 55%. On the basis of these physiological and molecular properties, strain APO is proposed to be a novel species of the genus Tindallia with the name Tindallia californiensis sp. nov., (type strain APO = ATCC BAA-393 = DSM 14871).