Rohde, Manfred

Significance We report on cultivation and characterization of an association between Candidatus Nanohalobium constans and its host, the chitinotrophic haloarchaeon Halomicrobium LC1Hm, obtained from a crystallizer pond of marine solar salterns. High-quality nanohaloarchael genome sequence in conjunction with electron- and fluorescence microscopy, growth analysis, and proteomic and metabolomic data revealed mutually beneficial interactions between two archaea, and allowed dissection of the mechanisms for these interactions. Owing to their ubiquity in hypersaline environments, Nanohaloarchaeota may play a role in carbon turnover and ecosystem functioning, yet insights into the nature of this have been lacking. Here, we provide evidence that nanohaloarchaea can expand the range of available substrates for the haloarchaeon, suggesting that the ectosymbiont increases the metabolic capacity of the host.

Abstract The recently isolated strain L21-Fru-ABT represents moderately halophilic, obligately anaerobic and saccharolytic bacteria that thrive in the suboxic transition zones of hypersaline microbial mats. Phylogenetic analyses based on 16S rRNA genes, RpoB proteins and gene content indicated that strain L21-Fru-ABT represents a novel species and genus affiliated with a distinct phylum-level lineage originally designated Verrucomicrobia subdivision 5. A survey of environmental 16S rRNA gene sequences revealed that members of this newly recognized phylum are wide-spread and ecologically important in various anoxic environments ranging from hypersaline sediments to wastewater and the intestine of animals. Characteristic phenotypic traits of the novel strain included the formation of extracellular polymeric substances, a Gram-negative cell wall containing peptidoglycan and the absence of odd-numbered cellular fatty acids. Unusual metabolic features deduced from analysis of the genome sequence were the production of sucrose as osmoprotectant, an atypical glycolytic pathway lacking pyruvate kinase and the synthesis of isoprenoids via mevalonate. On the basis of the analyses of phenotypic, genomic and environmental data, it is proposed that strain L21-Fru-ABT and related bacteria are specifically adapted to the utilization of sulfated glycopolymers produced in microbial mats or biofilms.

Novel halophilic, alkalithermophilic, Gram-type-positive bacterial strains were isolated from sediment of alkaline, hypersaline lakes of the Wadi An Natrun, Egypt. Cells of strain JW/NM-WN-LFTwere rod-shaped, non-spore-forming and non-motile. Strain JW/NM-WN-LFTgrew (at pH55 °C 9.5) between 35 and 56 °C, with an optimum at 53 °C. The pH55 °Crange for growth was 8.3–10.6, with an optimum at pH55 °C 9.5 and no growth at pH55 °C 8.2 or below, or at pH55 °C 10.8 or above. At the optimum pH and temperature, the strain grew in the Na+range of 3.1–4.9 M (1.5–3.3 M added NaCl) and optimally between 3.3 and 3.9 M Na+(1.7–2.3 M added NaCl). Strain JW/NM-WN-LFTutilized fructose, cellobiose, ribose, trehalose, trimethylamine, pyruvate, Casamino acids, acetate, xylose and peptone as carbon and energy sources. Fumarate (20 mM), S2O32−(20 mM), NO3−(20 mM) and iron(III) citrate (20 mM) were utilized as electron acceptors. During growth on sucrose, the isolate produced acetate and formate as major fermentation products. Main cellular fatty acids were iso-branched 15 : 0, i17 : 0 dimethylacetal and 16 : 0 dimethylacetal. The G+C content of genomic DNA was 40.4 mol% (HPLC). On the basis of genotypic and phenotypic characteristics, it is proposed that strain JW/NM-WN-LFTrepresents a novel genus and species,Natranaerobius thermophilusgen. nov., sp. nov. The type strain is JW/NM-WN-LFT(=DSM 18059T=ATCC BAA-1301T). Based on 16S rRNA gene sequence analysis, the strain forms a novel lineage within the class ‘Clostridia’ and clusters with uncultivated bacteria and unidentified strains retrieved from alkaline, hypersaline environments. The phylogenetic data suggest that the lineage represents a novel family,Natranaerobiaceaefam. nov., and order,Natranaerobialesord. nov.