Bacteroides vicugnae sp. nov. isolated from the fecal material of an alpaca

Two strictly anaerobic, Gram-stain-negative rod-shaped bacterial isolates, A2-P53T and A1-P5, were isolated from an enrichment of fecal material from two alpacas (Vicugna pacos). Based on a comparative 16S rRNA gene sequence analysis, the isolates were assigned to the genus Bacteroides with the highest sequence similarities to Bacteroides koreensis YS-aM39T (A2- P53T 97.7 % and A1-P5 97.9 %). Additionally, the average nucleotide identity and digital DNA-DNA hybridization values between these isolates and their closest relatives within Bacteroides were less than 92.1 % and 49.1 %, respectively. The average nucleotide identity between isolates A2-P53T and A1-P5 was 99.9 %. The predominant cellular fatty acid for isolates A2-P53T and A1-P5 was C15:0 antesio. The G+C % content of the isolates was 41.7 %. Based on biochemical, phylogenetic, genotypic, and chemotaxonomic criteria, these isolates A2-P53T and A1-P5 represent two individual strains of a novel species within the genus Bacteroides for which the name Bacteroides vicugnae sp. nov. is proposed. The type strain of this species is strain A2-P53T (CCUG 77273T = CCM 9377T = NRRL B-65693T).

Clostridium tanneri sp. nov., isolated from the faecal material of an alpaca

A strictly anaerobic, Gram-stain-negative rod-shaped bacterium, designated A1-XYC3T, was isolated from the faeces of an alpaca (Lama pacos). On the basis of the results of a comparative 16S rRNA gene sequence analysis, the isolate was assigned to the genus Clostridium with the highest sequence similarities to Clostridium magnum DSM 2767T (96.8 %), Clostridium carboxidivorans P7T (96.3 %) and Clostridium aciditolerans JW/YJL-B3T (96.1 %). The average nucleotide identity between A1-XYC3T, C. magnum, C. carboxidivorans and C. aciditolerans was 77.4, 76.1 and 76.6  %, respectively. The predominant components of the cellular fatty acids of A1-XYC3T were C14 : 0, C16 : 0 and summed feature 10, containing C18:0/C17:0 cyclo. The DNA G+C content was 32.4 mol%. On the basis of biochemical, phylogenetic, genotypic and chemotaxonomic criteria, this isolate represents a novel species within Clostridium sensu stricto for which the name Clostridium tanneri sp. nov. is proposed. The type strain of this species is strain A1-XYC3T (=CCM 9376T=NRRL B-65691T).

Reprogramming the metabolism of an acetogenic bacterium to homoformatogenesis

Methyl groups are abundant in anoxic environments and their utilization as carbon and energy sources by microorganisms involves oxidation of the methyl groups to CO₂, followed by transfer of the electrons to an acceptor. In acetogenic bacteria, the electron acceptor is CO₂ that is reduced to enzyme bound carbon monoxide, the precursor of the carboxyl group in acetate. Here, we describe the generation of a mutant of the acetogen Acetobacterium woodii in which the last step in methyl group oxidation, formate oxidation to CO₂ catalyzed by the HDCR enzyme, has been genetically deleted. The mutant grew on glycine betaine as methyl group donor, and in contrast to the wild type, formed formate alongside acetate, in a 1:2 ratio, demonstrating that methyl group oxidation stopped at the level of formate and reduced electron carriers were reoxidized by CO₂ reduction to acetate. In the presence of the alternative electron acceptor caffeate, CO₂ was no longer reduced to acetate, formate was the only product and all the carbon went to formate. Apparently, acetogenesis was not required to sustain formatogenic growth. This is the first demonstration of a genetic reprogramming of an acetogen into a formatogen that grows by homoformatogenesis from methyl groups. Formate production from methyl groups is not only of biotechnological interest but also for the mechanism of electron transfer in syntrophic interactions in anoxic environments.

Reclassification of Clostridium cocleatum, Clostridium ramosum, Clostridium spiroforme and Clostridium saccharogumia as Thomasclavelia cocleata gen. nov., comb. nov., Thomasclavelia ramosa comb. nov., gen. nov., Thomasclavelia spiroformis comb. nov. and Thomasclavelia saccharogumia comb. nov

The genus Clostridium is phenotypically and genotypically diverse, with many species phylogenetically located outside Clostridium sensu stricto. One such group consists of the species Clostridium cocleatum, Clostridium ramosum, Clostridium spiroforme and Clostridium saccharogumia (formally clostridial rRNA cluster XVIII) [1]. Sequencing of the 16S rRNA and, more recently, the results of genomic analyses have demonstrated that these species represent a coherent cluster separated from other closely related genera located in the family Coprobacillaceae within the order Erysipelotrichales [2]. In addition to phenotypic, phylogenetic and genomic comparisons, chemotaxonomic features were consistent between all four species, the predominant fatty acids were C_16 : 0 and C_18 : 1ω9c, while glucose and ribose were the whole cell sugars present in the cell walls. Furthermore, he results of peptidoglycan analysis indicated that meso-2,6-diaminopimelic acid was present as the diagnostic diamino acid in all four species. Biochemical profiles were also concordant with them being closely related species. Therefore, on the basis of phylogenetic, genomic, phenotypic and chemotaxonomic information, a novel genus, Thomasclavelia gen. nov., is proposed. It is suggested that Clostridium cocleatum, Clostridium ramosum, Clostridium spiroforme and Clostridium saccharogumia be transferred to this genus as Thomasclavelia cocleata comb. nov., Thomasclavelia ramosa comb. nov., Thomasclavelia saccharogumia comb. nov. and Thomasclavelia spiroformis comb. nov. The type species of the genus is Thomasclavelia ramosa CCUG 24038^T (=ATCC 25582^T=DSM 1402^T).