Halotolerantifilum yawarlongkerapense gen. nov., sp. nov., a novel halotolerant and thermotolerant bacterium isolated from Lake Warden, and proposal of Guggenheimellaceae fam. nov. in the order Peptostreptococcales

A novel, strictly anaerobic, thermotolerant/halotolerant, heterotrophic bacterial strain, SD5^T, was isolated from a brine lake near Esperance, Western Australia. The strain was a non-motile, non-spore-forming, Gram-stain-positive rod. The DNA G+C content was 53.1 mol%, and the length of the closed genome was 3.14 Mbp, with 2,978 protein-encoding genes. 16S rRNA gene sequence identity indicates that the strain is most closely related to <i>Fusibacter fontis</i> KhalAKB1^T (89.50% identity). SD5^T was phylogenomically distinct from its closest neighbors in the family <i>Acidaminobacteraceae</i>, with percentage of conserved proteins values ranging from 38.74% to 42.66%. The strain grew between 4 and 42 °C (optimum 37 °C), at pH values between 6.5 and 9.0 (optimum 7.0) and with 1-10% (w/v) sodium chloride (optimum 5%). The strain exhibited an aggregated growth phenotype associated with biofilm formation under stress, with cell chains reaching nearly 100 µm in length. The predominant fatty acids were iso-C_15:1 <i>ω</i>7<i>c</i> (11.8%), iso-C_15:0 (9.3%) and C_16:0 (9.3%). Based on phylogenomic and chemotaxonomic analyses, SD5^T represents a novel species in a new genus, for which the name <i>Halotolerantifilum yawarlongkerapense</i> gen. nov., sp. nov., is proposed. The type strain is SD5^T (=DSM 117693^T=ATCC TSD-463^T). From this work, we also propose the reassignment of several currently unranked genera within the class <i>Clostridia</i> to families within the order <i>Peptostreptococcales</i> and propose the novel family <i>Guggenheimellaceae</i> fam. nov. based on our sequencing results.