Miniphocaeibacter halophilus sp. nov., an ammonium-tolerant acetate-producing bacterium isolated from a biogas system

Abstract

An anaerobic bacterial strain, designated AMB_01T, recovered from mesophilic propionate enrichment of a high-ammonia biogas digester, was characterised using phenotypic and molecular taxonomic methods. Cells of AMB_01T are coccus-shaped and often occur arranged as diplococci or sarcina. Growth occurred at 20–45 °C, initial pH 5.5–8.5 and with up to 0.7 M NH4Cl, with optimum growth at 37–42 °C and pH 8.0. AMB_01T achieved high cell density and highest acetate production when grown on carbohydrates, including monomers, disaccharides and polysaccharides, such as glucose, maltose, cellobiose and starch. The strain was also able to use amino acids and some organic acids and alcoholic compounds for growth. Acetate was formed as the main product and yeast was not required for growth. The major cellular fatty acids were summed feature 4 (iso-C17 : 1I and/or anteiso-C17 : 1B), C18 : 1ω7, C14 : 0, C16 : 0 and summed feature 3 (C16 : 1ω7 and/or iso-C15 : 0 2OH). The highest 16S rRNA gene sequence similarity found was with Miniphocaeibacter massiliensis (96.6 %), within the family Peptoniphilaceae , phylum Bacillota (Firmicutes). The genomic DNA G+C content was 29.0 mol%. An almost complete set of genes for the acetyl-CoA pathway was found. Genome comparisons between AMB_01T and close relatives showed highest digital DNA–DNA hybridisation to Finegoldia magna (23 %), highest average nucleotide identity with genome nucleotide and amino acid sequences to M. massiliensis (72 and 73 %, respectively) and highest average nucleotide identity (87 %) with Schnuerera ultunensis , indicating that AMB_01T represents a novel species. Analysis of genomic, chemotaxonomic, biochemical and physiological data confirmed that strain AMB_01T represents a novel species, for which the name Miniphocaeibacter halophilus sp. nov. is proposed. The type strain is AMB_01T (=DSM 110247T=JCM 39107 T).