Aquabacterium gen. nov., with description of Aquabacterium citratiphilum sp. nov., Aquabacterium parvum sp. nov. and Aquabacterium commune sp. nov., three in situ dominant bacterial species from the Berlin drinking water system

Three bacterial strains (B4T, B6T, B8T) were isolated from biofilms in the Berlin drinking water distribution system and characterized morphologically, physiologically, and genetically. These motile, Gram-negative rods are oxidase-positive, catalase-negative, and store polyalkanoates and polyphosphates. They display microaerophilic growth, utilize oxygen and nitrate as electron acceptors, and metabolize organic acids but not carbohydrates. The three strains showed DNA relatedness of 44.9-51.3%, indicating they represent distinct species. Phylogenetic analysis based on 16S rRNA gene sequences placed them in the β-subclass of Proteobacteria, related to Leptothrix and Ideonella genera. Based on these findings, a new genus Aquabacterium gen. nov. is proposed containing three species: Aquabacterium citratiphilum sp. nov., Aquabacterium parvum sp. nov., and Aquabacterium commune sp. nov., with A. commune designated as the type species.

Key findings

• Three dominant bacterial species from Berlin drinking water biofilms constitute a new genus Aquabacterium with three species: A. citratiphilum, A. parvum, and A. commune
• All three species are Gram-negative, motile rods that are oxidase-positive, catalase-negative, and display microaerophilic growth behavior, utilizing fatty acids and organic acids but not carbohydrates
• DNA-DNA hybridization confirmed the three strains are distinct species with 44.9-51.3% relatedness; 16S rRNA analysis places them in the β-subclass of Proteobacteria
• The three species differ in substrate utilization patterns, urea and casein hydrolysis abilities, temperature tolerance, and growth on nutrient-rich media