Two novel, obligately anaerobic Firmicutes from the family Erysipelotrichaceae were isolated from the intestinal tracts of a cockroach (strain ErySL, Shelfordella lateralis) and a scarab beetle larva (strain Pei061, Pachnoda ephippiata). Phylogenetic analysis indicated that the strains belong to a monophyletic group of hitherto uncultured bacteria from insect guts that are only distantly related to any described species (<90% 16S rRNA gene sequence similarity). Ultrastructural analysis revealed a Gram-positive cell envelope and, in the case of strain ErySL, a wide electron-lucent space between the cytoplasmic membrane and cell wall. In older cultures, cells formed pleomorphic rods with a thicker peptidoglycan layer. Both strains were obligately anaerobic and fermented glucose to formate, ethanol, and acetate as major products, but strain Pei061 tolerated up to 1% oxygen in the headspace. The same type of metabolism was observed with Erysipelothrix inopinata, except that the latter grew, albeit poorly, even under air. However, previous claims of a microaerophilic or facultatively anaerobic metabolism in the genus Erysipelothrix could not be substantiated. Based on phenotypic and phylogenetic evidence, we propose to classify the isolates as members of a new genus, Breznakia blatticola gen. nov. sp. nov. and Breznakia pachnodae sp. nov., with strain ErySL(T) (=DSM 28867(T)=JCM 30190(T)) and strain Pei061(T) (=DSM 16784(T)=JCM 30191(T)) as type strains, and provide an emended description of the family Erysipelotrichaceae.
Keywords: Emended family description; Erysipelotrichaceae; Insect gut bacteria; Mixed-acid fermentation; Novel genus; Obligately anaerobic.
Copyright © 2016 Elsevier GmbH. All rights reserved.