RESUMO
Two novel anaerobic, moderately thermophilic and cellulose-/cellobiose-digesting bacteria, EBR45(T) and EBR596(T), were isolated from anaerobic sludge of a cellulose-degrading methanogenic bioreactor. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these strains belonged to cluster III within the low-G+C-content Gram-positive bacteria. The close relatives of EBR45(T) were Clostridium straminisolvens DSM 16021(T) (sequence identity, 94.6 %) and Clostridium thermocellum DSM 1237(T) (93.4 %). The closest relative of EBR596(T) was Clostridium stercorarium DSM 8532(T) (95.9 %). Both isolates were rod-shaped sporulators, growing optimally at 60 degrees C. EBR45(T) was Gram-staining-reaction-variable and non-motile, formed bright-yellow colonies on solid media, and grew on a relatively narrow range of carbohydrates including cellulose and cellobiose. EBR596(T) was Gram-staining-reaction-negative and motile, formed glossy white colonies and grew on cellobiose and various carbohydrates except cellulose. Major fatty acid compositions were 16 : 0 iso, 16 : 0 and 16 : 0 dimethylacetal (strain EBR45(T)) and 15 : 0 iso, 16 : 0 iso, 15 : 0 anteiso and 17 : 0 anteiso (strain EBR596(T)). The DNA G+C contents were 36.9 mol% (EBR45(T)) and 51.1 mol% (EBR596(T)). Based on the phenotypic and phylogenetic data and genomic distinctiveness, strains EBR45(T) and EBR596(T) represent two novel species, for which the names Clostridium clariflavum sp. nov. (type strain EBR45(T) =DSM 19732(T) =NBRC 101661(T)) and Clostridium caenicola sp. nov. (type strain EBR596(T) =DSM 19027(T) =NBRC 102590(T)) are proposed.
Assuntos
Celobiose/metabolismo , Celulose/metabolismo , Clostridium/classificação , Temperatura Alta , Metano/metabolismo , Esgotos/microbiologia , Técnicas de Tipagem Bacteriana , Composição de Bases , Clostridium/genética , Clostridium/isolamento & purificação , Clostridium/fisiologia , DNA Bacteriano/análise , Ácidos Graxos/análise , Genes de RNAr , Genótipo , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Fenótipo , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
A novel anaerobic, moderately thermophilic, spore-forming, rod-shaped bacterium (strain EBR46T) was isolated from an enrichment culture derived from an anaerobic thermophilic (55 degrees C) methanogenic bioreactor treating artificial solid wastes. Phylogeny based on 16S rRNA gene sequence analysis placed strain EBR46T within a distinct lineage between Clostridium clusters II and III. The closest recognized relative of strain EBR46T was Gracilibacter thermotolerans DSM 17427T (85.3 % 16S rRNA gene sequence similarity). The DNA G+C content of strain EBR46T was 36.2 mol%. The novel strain grew optimally at 55-58 degrees C and at pH 7.5-8.0 and was able to grow on peptone, tryptone, Casamino acids, casein hydrolysate, methionine, threonine, tryptophan, cysteine, lysine and serine in the presence of 0.2 % yeast extract. Carbohydrates were not utilized. The main products from tryptone utilization were acetate, iso-butyrate, propionate and iso-valerate. Strain EBR46T produced hydrogen sulfide from cysteine. The major fatty acids were iso-C15 : 0, C14 : 0, C16 : 0 DMA (dimethyl acetal) and iso-C15 : 0 DMA. Based on its unique phylogenetic and physiological features, strain EBR46T is considered to represent a novel species of a new genus, for which the name Lutispora thermophila gen. nov., sp. nov. is proposed. The type strain of the type species is EBR46T (=NBRC 102133T=DSM 19022T).
Assuntos
Bacilos Gram-Positivos Formadores de Endosporo/classificação , Bacilos Gram-Positivos Formadores de Endosporo/isolamento & purificação , Composição de Bases , Sequência de Bases , Reatores Biológicos/microbiologia , Primers do DNA/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Ácidos Graxos/metabolismo , Genes Bacterianos , Bacilos Gram-Positivos Formadores de Endosporo/genética , Bacilos Gram-Positivos Formadores de Endosporo/metabolismo , Temperatura Alta , Metano/biossíntese , Microscopia Eletrônica de Transmissão , Dados de Sequência Molecular , Fenótipo , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Eliminação de Resíduos , Terminologia como AssuntoRESUMO
A methanogenic bioreactor that utilized wastepaper was developed and operated at 55 degrees C. Microbial community structure analysis showed the presence of a group of clostridia that specifically occurred during the period of high fermentation efficiency. To isolate the effective cellulose digester, the sludge that exhibited high fermentation efficiency was inoculated into a synthetic medium that contained cellulose powder as the sole carbon source and was successively cultivated. A comprehensive 16S rRNA gene sequencing study revealed that the enriched culture contained various clostridia that had diverse phylogenetic positions. The microorganisms were further enriched by successive cultivation with filter paper as the substrate, as well as the bait carrier. A resultant isolate, strain EBR45 (= Clostridium sp. strain NBRC101661), was a new member of the order Clostridiales phylogenetically and physiologically related to Clostridium thermocellum and Clostridium straminisolvens. Specific PCR-based monitoring demonstrated that strain EBR45 specifically occurred during the high fermentation efficiency period in the original methanogenic sludge. Strain EBR45 effectively digested office paper in its pure cultivation system with a synthetic medium.
