International Journal of Systematic and Evolutionary Microbiology (2013), 63, 959–964 DOI 10.1099/ijs.0.043703-0 Desulfoconvexum algidum gen. nov., sp. nov., a psychrophilic sulfate-reducing bacterium isolated from a permanently cold marine sediment Martin Ko¨nneke,13 Jan Kuever,2 Alexander Galushko14 and Bo Barker Jørgensen11 Correspondence 1Max-Planck Institute for Marine Microbiology, Bremen, Germany Martin Ko¨nneke 2Bremen Institute for Materials Testing, Bremen, Germany [email protected] A sulfate-reducing bacterium, designated JHA1T, was isolated from a permanently cold marine sediment sampled in an Artic fjord on the north-west coast of Svalbard. The isolate was originally enriched at 4 6C in a highly diluted liquid culture amended with hydrogen and sulfate. Strain JHA1T was a psychrophile, growing fastest between 14 and 16 6C and not growing above 20 6C. Fastest growth was found at neutral pH (pH 7.2–7.4) and at marine concentrations of NaCl (20– 30 g l”1). Phylogenetic analysis of 16S rRNA gene sequences revealed that strain JHA1T was a member of the family Desulfobacteraceae in the Deltaproteobacteria. The isolate shared 99 % 16S rRNA gene sequence similarity with an environmental sequence obtained from permanently cold Antarctic sediment. The closest recognized relatives were Desulfobacula phenolica DSM 3384T and Desulfobacula toluolica DSM 7467T (both ,95 % sequence similarity). In contrast to its closest phylogenetic relatives, strain JHA1T grew chemolithoautotrophically with hydrogen as an electron donor. CO dehydrogenase activity indicated the operation of the reductive acetyl-CoA pathway for inorganic carbon assimilation. Beside differences in physiology and morphology, strain JHA1T could be distinguished chemotaxonomically from the genus Desulfobacula by the absence of the cellular fatty acid C16 : 0 10-methyl. Phylogenetic differentiation from other genera was further supported by DsrAB and AprBA sequence analysis. Based on the described phylogenetic and phenotypic differences between strain JHA1T and its closest relatives, the establishment of a novel genus and a novel species, Desulfoconvexum algidum gen. nov., sp. nov. is proposed. The type strain is JHA1T (5DSM 21856T 5JCM 16085T). Anaerobic degradation of organic matter in marine anoxic marine sediments (Jørgensen, 1982). The major sediments generally proceeds via several steps of catabolic electron donors for sulfate reduction are end products of processes which are catalysed by a variety of micro- fermentation, such as short-chain organic acids and organisms. Since sulfate occurs at a high concentration hydrogen (Rabus et al., 2000). The concentrations of these in ocean water, the dissimilatory reduction of sulfate compounds in marine sediments are generally low, represents the major terminal remineralization process in indicating the close coupling of fermentation and the terminal oxidation step (Finke & Jørgensen, 2008). 3Present address: Organic Geochemistry Group, Department of Most of the ocean’s seafloor, including the deep ocean and Geosciences and MARUM Center for Marine Environmental Sciences, polar coastal areas, exhibits permanently cold conditions. University of Bremen, Germany Yet, only a limited number of psychrophilic or psychro- 4Present address: Department of Microbial Ecology, University of tolerant sulfate-reducing bacteria (SRB) have been isolated Vienna, Austria so far. However, rates of in situ sulfate reduction in 1Present address: Center for Geomicrobiology, Department of permanently cold sediments at the coast of the Svalbard Bioscience, Aarhus University, Denmark archipelago have been determined to be as high as those of Abbreviation: SRB, Sulfate-reducing bacteria. temperate marine sediments, pointing to the occurrence of The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA cold-adapted SRB (Sagemann et al., 1998). From the same gene, dsrAB and aprBA sequences of strain JHA1T are EF442984, location, novel psychrophilic SRB were selectively isolated JQ901403 and EF442915, respectively. at low temperatures with acetate, lactate or propionate as Two supplementary figures are available with the online version of this the electron donors (Knoblauch & Jørgensen, 1999, paper. Knoblauch et al., 1999) and most of the described isolates 043703 G 2013 IUMS Printed in Great Britain 959 M. Ko¨nneke and others Table 1. Selected characteristics for differentiation of strain JHA1T from its closest relatives Strains: 1, Desulfoconvexum algidum gen. nov., sp. nov. JHA1T;2,Desulfobacula toluolica (DSM 7467T) (data from Rabus et al.,1993);3,Desulfobacula phenolica (DSM 3384T) (Bak & Widdel, 1986); 4, Desulfospira joergensenii (Finster et al., 1997). All strains used butyrate (5 mM) and fumarate (10 mM) as electron donors, and sulfate (28 mM) and thiosulfate (10 mM) as electron acceptors. SRWG, Sulfate reduction without growth; +,positive;2, negative; ND, no data available. Characteristic 1 2 3 4 Cell morphology Curved, vibrioid Oval–coccoid Oval to curved Curved, vibrioid Cell width (mm) 1.5 1.2–1.4 1–1.5 0.7–0.8 Cell length (mm) 2.0–3.5 1.2–2.0 2–3 1–2 Motility +++2 G+C content (mol%) 46 42 41 49 Electron donors for sulfate reduction (mM) Hydrogen + 22+ Formate (20) + 2 ++ Acetate (20) 22+ 2 Propionate (15) 222 Valerate (5) + 2 ND ND Caproate (5) + 22ND Caprate (2) + ND ND ND Lactate (10) + 22+ Malate (10) +++2 Succinate (10) 2 +++ Pyruvate (10) 2 +++ Ethanol (10) +++2 n-Propanol (10) +++2 n-Butanol (10) +++2 Methanol (10) + 2 ND SRWG Glycerol (10) + ND ND + Glycine (10) + ND ND SRWG Alanine (10) + ND ND SRWG Serine (10) + ND ND ND Betaine (10) + ND ND + Choline chloride (10) + ND ND + Proline (10) + ND ND + Sorbitol (10) + ND ND 2 Mannitol (5) + ND ND 2 Benzoate (3) +++SRWG Electron acceptors (mM) Sulfite (5) 2 ND 2 + Sulfur + ND 2 + Nitrate 2 ND 22 Fermentable substrates (mM) Pyruvate 2 ND ND 2 Malate + ND ND 2 Lactate 2 ND ND 2 Fumarate + ND ND 2 Autotrophy + 22+ Conditions for growth Range (uC) 0–20 ND ND 8–30 Optimum (uC) 14–16 28 28 26–30 Optimum pH 7.2–7.4 7.0–7.1 ND 7.4 Optimum NaCl (g l21) 20–30 20 20 12–20 belonged to the order Desulfobacterales. Further studies using 1999; Ravenschlag et al., 1999, 2000, 2001). In order to molecular methods verified the presence of active and culture and identify the potentially most abundant and active abundant SRB in several coastal sediments sampled from lithotrophic SRB from these fjords, liquid-dilution cultures different fjords of the Svalbard archipelago (Sahm et al., were incubated at 4 uC with hydrogen or formate as the 960 International Journal of Systematic and Evolutionary Microbiology 63 Desulfoconvexum algidum gen. nov., sp. nov. electron donor in combination with sulfate as the sole A variety of organic compounds were tested as potential electron acceptor (Ko¨nneke, 2001). From dilution series with electron donors for sulfate reduction. Substrates were formate, seven isolates were obtained that were identified by added from sterile stock solutions at a final concentration 16S rRNA gene sequence analysis as Desulfotalea psychrophila of 2–20 mM. Hydrogen was provided (H2/CO2, 90 : 10) or Desulfotalea arctica. Three lithotrophic SRB were isolated with 1 bar overpressure in the headspace. Acetate and in pure culture with hydrogen as the sole electron donor. lactate oxidation were determined with an HPLC system According to their 16S rRNA genes, two strains were equipped with an Aminex HPX-87H ion-exclusion column affiliated with the Desulfobulbaceae within the Deltaproteo- (Bio-Rad) and analysed at 60 uC using 5 mM H2SO4 as the bacteria, sharing highest identity with the psychrophilic SRB mobile phase. Spectrophotometric detection and quan- strain LSv53 (99.9 %) and an environmental 16S rRNA gene tification were performed at 210 nm (UVIS 204; Linear sequence (Sva0999; 97.2 %). The third pure culture, strain Instruments). JHA1T, was isolated from Smeerenburgfjorden and was found to be a member of the Desulfobacteraceae.Strain The psychrophilic isolate utilized a variety of organic JHA1T was subjected to a phylogenetic, physiological and compounds, including fatty acids, alcohols and sugars as well as amino acids (Table 1). Lactate as an electron donor chemotaxonomic characterization and comparison with its T closest described relatives, Desulfobacula phenolica DSM was completely oxidized to CO2. Strain JHA1 shared the 3384T, Desulfobacula toluolica DSM 7467T (both ,95 % 16S capacity with Desulfobacula toluolica and Desulfobacula rRNA gene sequence similarity) and Desulfospira joergensenii phenolica to grow with the aromatic compound benzoate DSM 10085T (,93 %). as an electron donor for sulfate reduction. In contrast to both members of the genus Desulfobacula, strain JHA1T T Strain JHA1 was isolated from sediment at a depth of grew chemolithoautrophically with hydrogen as a sole 5 cm from a fjord on the north-west coast of Svalbard electron donor and with CO2/bicarbonate as a sole carbon (Smeerenburgfjorden; 79u 429 8150 N11u 059 1890 E). The source. Autotrophic growth was verified by transferring bottom water temperature during sampling (July 1998) the culture repeatedly into medium free of any organic was 0 uC. Initial enrichment was performed in a 10,000- substrate. Activity of CO dehydrogenase in a cell-free extract times dilution in defined carbonate-buffered saltwater of strain JHA1T, measured as previously described at 20 uC medium (Widdel & Bak, 1992) with hydrogen (headspace (Galushko & Schink, 2000), indicated the operation of the H2/CO2 90 : 10) as the sole electron