Oxidative Stress and Antioxidant Cell Protection Systems in the Microaerophilic Bacterium Spirillum winogradskii

The influence of oxygen availability during cultivation on the biosynthetic processes and enzymatic activities in the microaerophilic bacterium Spirillum winogradskii D-427 was studied, and the roles played by different systems of the defense against oxidation stress were determined. The metabolic adjustments caused by transition from microaerobic (2% O₂) aerobic conditions (21% O₂ of the gas phase) were found to slow down constructive metabolism and increase synthesis of exopolysaccharides as a means of external protection of cells from excess oxygen. This resulted in a twofold decline of the growth yield coefficient. Even though the low activity of catalase is compensated for by a multifold increase in the activities of other cytoplasmic enzymes that defend against toxic forms of O₂—peroxidase and enzymes of the redox system of glutathione (glutathione peroxidase and glutathione reductase)—massive lysis of cells starts in the midexponential phase and leads to culture death in the stationary phase because of H₂O₂ accumulation in the periplasm (up to 10 g/mg protein). The absence in cells of cytochrome-c-peroxidase, a periplasmic enzyme eliminating H₂O₂, was shown. It follows that the major cause of oxidative stress in cells is that active antioxidant defenses are located in the cytoplasm, whereas H₂O₂ accumulates in the periplasm due to the lack of cytochrome-c-peroxidase. The addition to the medium of thiosulfate promotes elimination of H₂O₂, stops cell lysis under aerobic conditions, lends stability to cultures, and results in a threefold increase in the growth yield.     

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.     

Two new species of anaerobic oxalate-fermenting bacteria,Oxalobacter vibrioformis sp. nov. and Clostridium oxalicum sp. nov., from sediment samples

Two types of new anaerobic bacteria were isolated from anoxic freshwater sediments. They grew in mineral medium with oxalate as sole energy source and with acetate as main carbon source. Oxalate as well as oxamate (after deamination) were decarboxylated to formate with growth yields of 1.2–1.4 g dry cell matter per mol oxalate degraded. No other organic or inorganic substrates were used, and no electron acceptors were reduced. Strain WoOx3 was a Gramnegative, non-sporeforming, motile vibrioid rod with a guanine-plus-cytosine content of the DNA of 51.6 mol%. It resembled the previously described genus Oxalobacter, and is described as a new species, O. vibrioformis. Strain AltOx1 was a Gram-positive, spore-forming, motile rod with a DNA base ratio of 36.3 mol% guanine-plus-cytosine. This isolate is described as a new species of the genus Clostridium, C. oxalicum.     

Nitrogen fixation by Spirillum sp. from rice roots

Nitrogen fixation by Spirillum sp. obtained from the roots of rice plants grown at different levels of combined nitrogen was studied. The roots of rice plants exposed to low levels of combined nitrogen (20–40 kg N/ha) harboured Spirillum sp. possessing higher nitrogen-fixing efficiency as compared to the cultures from plants receiving 60–100 kg N/ha. More-over, the nitrogen-fixing efficiency of these Spirillum spp. varied with age of the plant, irrespective of the dosage of combined nitrogen.     

Rhodopseudomonas adriatica sp. nov., a new species of the Rhodospirillaceae,dependent on reduced sulfur compounds

A new purple nonsulfur bacterium was isolated from enrichment cultures of a sulfide-containing marine lagoon. The bacterium is similar to Rhodopseudomonas capsulata and is described as a new species of the genus Rhodopseudomonas: Rhodopseudomonas adriatica. Cells are non-motile, 0.5–0.8 m by 1.3–1.8 m, and multiply by binary fission. Intracytoplasmic membranes are of the vesicular type. The photosynthetic pigments are bacteriochlorophyll a and carotenoids of the spheroidene group. Growth is possible anaerobically in the light and at low pO₂ in the dark. Biotin and thiamine are required as growth factors. A wide variety of organic compounds, as well as sulfide and thiosulfate, are used as photosynthetic electron donors. Sulfide is oxidized to elemental sulfur, which is subsequently converted to sulfate, whereas thiosulfate oxidation occurs without measurable intermediate. Rhodopseudomonas adriatica is unable to assimilate sulfate, growth is only possible in the presence of a reduced sulfur compound.     

Bullera anomala sp. nov. and Bullera pseudovariabilis sp. nov., two new ballistoconidium-forming yeast species from Yunnan,China

Two ballistoconidium-forming yeast strains, CH 2.504 and CH 2.509, were isolated from the wilting leaves of Parthenocissus sp. collected in Yunnan, China in 1996. These two strains were assigned to the genus Bullera Derx by the characteristics of forming rotationally symmetric ballistoconidia, containing xylose in the cell hydrolysates and having Q-10 as the major ubiquinone. Molecular phylogenetic analysis based on small subunit ribosomal RNA gene (18S rDNA) and internal transcribed spacer (ITS) region sequences revealed that CH 2.504 is closely related to B. variabilis Nakase & Suzuki, while CH 2.509 is located in a clearly separate clade among the described Bullera species and related taxa. The results indicated that CH 2.509 represents a new species, for which Bullera anomala sp. nov. is the proposed name (type strain AS 2.2094^T). Further DNA-DNA reassociation data showed that CH 2.504 also represents a distinct species, for which the name Bullera pseudovariabilis sp. nov. is given (type strain AS 2.2092^T). This revised version was published online in June 2006 with corrections to the Cover Date.     

A new purple sulfur bacterium from saline littoral sediments,Thiorhodovibrio winogradskyi gen. nov. and sp. nov.

Two strains of a new purple sulfur bacterium were isolated in pure culture from the littoral sediment of a saline lake (Mahoney Lake, Canada) and a marine microbial mat from the North Sea island of Mellum, respectively. Single cells were vibrioid-to spirilloid-shaped and motile by means of single polar flagella. Intracellular photosynthetic membranes were of the vesicular type. As photosynthetic pigments, bacteriochlorophyll a and the carotenoids lycopene, rhodopin, anhydrorhodovibrin, rhodovibrin and spirilloxanthin were present.Hydrogen sulfide and elemental sulfur were used under anoxic conditions for phototrophic growth. In addition one strain (06511) used thiosulfate. Carbon dioxide, acetate and pyruvate were utilized by both strains as carbon sources. Depending on the strain propionate, succinate, fumarate, malate, tartrate, malonate, glycerol or peptone may additionally serve as carbon sources in the light. Optimum growth rates were obtained at pH 7.2, 33 °C, 50 mol m^-2 s^-1 intensity of daylight fluorescent tubes and a salinity of 2.2–3.2% NaCl. During growth on sulfide, up to ten small sulfur globules were formed inside the cells. The strains grew microaerophilic in the dark and exhibited high specific respiration rates. No vitamins were required for growth. The DNA base composition was 61.0–62.4 mol% G+C.The newly isolated bacterium belongs to the family chromatiaceae and is described as a member of a new genus and species, Thiorhodovibrio winogradskyi gen. nov. and sp. nov. with the type strain SSP1, DSM No. 6702.     

Zygozyma suomiensis,sp. nov. (Lipomycetaceae), a new species from Finland

A new species of the genus Zygozyma, Z. suomiensis, is described, based on the study of a single strain, derived from a bovine skin lesion.     

Description of four novel species of Xenorhabdus, family Enterobacteriaceae: Xenorhabdus budapestensis sp. nov., Xenorhabdus ehlersii sp. nov., Xenorhabdus innexi sp. nov., and Xenorhabdus szentirmaii sp. nov

The taxonomic affiliation was determined for four Xenorhabdus strains isolated from four Steinernema hosts from different countries. As compared to the five validly described Xenorhabdus species, i.e., X. nematophila, X. japonica, X. beddingii, X. bovienii and X. poinarii, these isolates represented novel species on the basis of 16S rRNA gene sequences and riboprint patterns, as well as by physiological and metabolic properties. They were named Xenorhabdus budapestensis sp. nov., type strain DSM 16342^T, isolated from Steinernema bicornutum; Xenorhabdus ehlersii sp. nov., type strain DSM 16337^T, isolated from Steinernema serratum; Xenorhabdus innexi sp. nov., type strain DSM 16336^T isolated from Steinernema scapterisci; and Xenorhabdus szentirmaii sp. nov., type strain DSM 16338^T, isolated from Steinernema rarum.     

New anamorphic yeast species: Candida infanticola sp. nov., Candida polysorbophila sp. nov., Candida transvaalensis sp. nov. and Trigonopsis californica sp. nov

Three new species of Candida and a new species of Trigonopsis are described based on their recognition from phylogenetic analysis of gene sequences from large subunit ribosomal RNA, ITS1/ITS2 rRNA, mitochondrial small subunit rRNA and cytochrome oxidase II. Candida infanticola sp. nov. (type strain NRRL Y-17858, CBS 7922) was isolated from the ear of an infant in Germany and is closely related to Candida sorbophila. Candida polysorbophila sp. nov. (type strain NRRL Y-27161, CBS 7317) is a member of the Zygoascus clade and was isolated in South Africa as a contaminant from an emulsion of white oil and polysorbate. Candida transvaalensis sp. nov. (type strain NRRL Y-27140, CBS 6663) was obtained from forest litter, the Transvaal, South Africa, and forms an isolated clade with Candida santjacobensis. Trigonopsis californica sp. nov. (type strain NRRL Y-27307, CBS 10351) represents a contaminant from wine in California, and forms a well-supported clade with Trigonopsis cantarellii, Trigonopsis variabilis and Trigonopsis vinaria.     

Thiocapsa halophila sp. nov., a new halophilic phototrophic purple sulfur bacterium

A new phototrophic sulfur bacterium has been isolated from a red layer in a laminated mat occurring underneath a gypsum crust in the mediterranean salterns of Salin-de-Giraud (Camargue, France). Single cells were coccus-shaped, non motile, without gas vacuoles and contained sulfur globules. Bacteriochlorophyll a and okenone were present as major photosynthetic pigments. These properties and the G+C content of DNA (65.9–66.6 mol% G+C) are typical characteristics of the genus Thiocapsa. However, the new isolate differs from known species in the genus, particularly in NaCl requirement (optimum, 7% NaCl; range, 3–20% NaCl) and some physiological characteristics. Therefore, a new species is proposed, Thiocapsa halophila, sp. nov.Dedicated to Prof. Dr. Norbert Pfennig in occasion of his 65th birthday     

Leucobacter luti sp. nov., and Leucobacter alluvii sp. nov., two new species of the genus Leucobacter isolated under chromium stress

Two strains designated RF6(T) and RB10(T) were isolated, from activated sludge and from river sediments, respectively, both systems receiving chromium contaminated water. Phylogenetic analysis showed that strain RF6(T)and strain RB10(T) represented two new species of the genus Leucobacter. Strain RB10(T) can be distinguished from RF6(T) by its ability to grow at 37 degrees C, by showing a different optimum pH, by cell wall amino acids different relative amount and by having the fatty acid strait C16:0 as the third most abundant fatty acid. On the basis of the distinct peptidoglycan composition, 16S ribosomal DNA sequence analysis, DNA-DNA reassociation values, and phenotypic characteristics we are of the opinion that strain RF6(T) represents a new species of the genus Leucobacter for which we propose the name Leucobacter luti (CIP 108818(T)=LMG 23118) and that strain RB10(T) represents an additional new species of the same genus for which we propose the name Leucobacter alluvii (CIP 108819(T)=LMG 23117).     

Candida alocasiicola sp. nov., Candida hainanensis sp. nov., Candida heveicola sp. nov. and Candida musiphila sp. nov., novel anamorphic, ascomycetous yeast species isolated from plants

In a taxonomic study on the ascomycetous yeasts isolated from plant materials collected in tropical forests in Yunnan and Hainan Provinces, southern China, four strains isolated from tree sap (YJ2E(T)) and flowers (YF9E(T), YWZH3C(T) and YYF2A(T)) were revealed to represent four undescribed yeast species. Molecular phylogenetic analysis based on the large subunit (26S) rRNA gene D1/D2 domain sequences showed that strain YJ2E(T) was located in a clade together with Candida haemulonii and C. pseudohaemulonii. Strain YF9E(T) was most closely related to C. azyma and strain YWZH3C(T) to C. sorbophila and C. spandovensis. Strain YYF2A(T) was clustered in a clade containing small-spored Metschnikowia species and related anamorphic Candida species. The new strains differed from their closely related described species by more than 10% mismatches in the D1/D2 domain. No sexual states were observed for the four strains on various sporulation media. The new species are therefore assigned to the genus Candida and described as Candida alocasiicola sp. nov. (type strain, YF9E(T) = AS 2.3484(T) = CBS 10702(T)), Candida hainanensis sp. nov. (type strain, YYF2A(T) = AS 2.3478(T) = CBS 10696(T)), Candida heveicola sp. nov. (type strain, YJ2E(T) = AS 2.3483(T) = CBS 10701(T)) and Candida musiphila sp. nov. (type strain, YWZH3C(T) = AS 2.3479(T) = CBS 10697(T)).     

Debaryomyces udenii,sp. nov. (Saccharomycetaceae), a new species from soil

A new, soil-associated species of the genus Debaryomyces, D. udenii, is described. The species is characterized by pusticulate rather than verrucate ascospores, and slowly lytic asci.     

New species of psychrophilic acetogens: Acetobacterium bakii sp. nov., A. paludosum sp. nov., A. fimetarium sp. nov.

Three strains of new acetogenic bacteria were isolated from several low temperature environments. Cells were gram-positive, oval-shaped flagellated rods. The organisms fermented H₂/CO₂, CO, formate, lactate, and several sugars to acetate. Strains Z-4391 and Z-4092 grew in the temperature range from 1 to 30°C with an optimum at 20°C; strain Z-4290 grew in the range from 1 to 35°C with an optimum at 30°C. The DNA G+C content of strains Z-4391, Z-4092, and Z-4290 was 42.1, 41.7, and 45.8 mol% respectively.     

Thermococcus litoralis sp. nov.: A new species of extremely thermophilic marine archaebacteria

We describe a new species, Thermococcus litoralis, which is different from the type species Thermococcus celer in molecular, morphological and physiological characteristics.Abbreviations 3 x SSC (standard saline citrate) - 0.45 M NaCl 0.045 M Na₃-citrate     

Frondisphaeria palmicola gen. et sp. nov. from Brunei

The monotypic genusFrondisphaeria (Unitunicate Ascomycetes inc. sed.) is introduced to accommodate a new palm ascomycete with slightly curved long-fusiform ascospores.Frondisphaeria has similarities withLinocarpon, but differs in having clavate asci, which are narrow at the apex and are provided with a refractive discoid subapical ring. Ascomata also form under darkened blotches on the host surface.     

Leptopalaemon gagadjui gen. nov., sp. nov., a new freshwater palaemonid shrimp from Arnhem land,and a re-evaluation of Palaemonetes holthuisi Strenth,with the designation of a new genus,Calathaemon

A new palaemonid shrimp, Leptopalaemon gagadjui, gen. nov., sp. nov., from the Arnhem Land plateau, Australia, is described and illustrated, and its systematic position discussed. The new genus most closely resembles Leptocarpus Holthuis, 1950, presently known only from India. Palaemonetes holthuisi Strenth is re-examined and excluded from the genus Palaemonetes. A new genus, Calathaemon, is designated for its accommodation.     

The functional role of reduced inorganic sulfur compounds in the metabolism of the microaerophilic bacterium <Emphasis Type="Italic">Spirillum winogradskii</Emphasis>

Oxidation of reduced sulfur compounds by the microaerophilic sulfur bacterium spirillum winogradskii was found to occur only concomitantly with consumption of an organic substrate and was not linked to their utilization as electron donors in energy metabolism. No enzymes of dissimilatory sulfur metabolism were found in the cells of the sulfur bacterium oxidizing thiosulfate to tetrathionate; oxidation of thiosulfate and sulfide was caused by their reaction with reactive oxygen species (ROSs), mostly H₂O₂ produced in the course of aerobic growth. A decreased lytic effect of ROSs in the presence of thiosulfate resulted in a twofold increase in the cell yield under aerobic conditions and more efficient substrate utilization. The latter effect was caused by decreased expenditure of energy for the biosynthesis of oxygen-protective polysaccharides. The stimulatory effect of thiosulfate on the growth processes was due to the activation of a number of TCA cycle enzymes producing the intermediates for constructive metabolism, especially of the NADP-dependent malic enzyme. As a result of thiosulfate-induced synthesis of SH-containing cell components, the integral antioxidative activity increased 1.5-fold.Translated from Mikrobiologiya, Vol. 74, No. 1, 2005, pp. 17–25.Original Russian Text Copyright © 2005 by Podkopaeva, Grabovich, Dubinina.