sp. nov., acidotolerant actinomycetes from pine litter, reclassification of , , and as comb. nov., comb. nov., comb. nov. and comb. nov., and emended descriptions of the genus , the family and .

Filamentous actinomycetes, designated SL13 and SL54, were isolated from pine litter and their taxonomic status resolved using a polyphasic approach. The isolates exhibit chemotaxonomic and morphological properties consistent with their classification in the family . They form extensively branched substrate mycelia bearing aerial hyphae that differentiate into straight chains of cylindrical spores. The whole-organism hydrolysates contain ll-diaminopimelic acid, glucose, mannose and ribose, the predominant isoprenologue is MK-9(H), the polar lipids are diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylglycerol and glycophospholipids, and the major fatty acids are anteiso-C, iso-C, iso-C and anteiso-C. Phylogenetic trees based on 16S rRNA gene sequences and multilocus gene sequences of conserved housekeeping genes show that the isolates form a well-supported lineage that is most closely related to NBRC 115203. All of these strains form a well-defined clade in the multilocus sequence analysis tree together with DSM 46488, DSM 41836 and DSM 42083. Draft genomes assemblies of the isolates are rich in biosynthetic gene clusters predicted to produce novel specialized metabolites and stress-related genes which provide an insight into how they have adapted to the harsh conditions that prevail in pine litter. Phylogenomically, both isolates belong to the same lineage as the type strains of , , and ; these relationships are underpinned by high average amino acid identity, average nucleotide identity and genomic DNA-DNA hybridization values. These metrics confirm that isolates SL13 and SL54 belong to a novel species that is most closely related to NBRC 115203 and that these strains together with DSM 41836, DSM 42083 belong to the genus . Consequently, it is proposed that the isolates be recognized as a new species, comb. nov., with isolate SL54 (=DSM 111111=PCM3044) as the type strain, and that , and be transferred to the genus as comb. nov., comb. nov. and comb. nov. Emended descriptions are given for the genus , the family and for which was found to be a close relative of the isolates in the 16S rRNA gene sequence analyses. It is also proposed that be transferred to the genus as comb. nov based on its position in the MLSA and phylogenomic trees and associated genomic data.