Description of two novel Micromonospora species: Micromonospora psammae sp. nov. from desert soil and Micromonospora lacuserhaii sp. nov. from lake sediment.

Three strains - CPCC 205556^T and CPCC 205543 isolated from gravel soil in China's Gurbantunggut Desert and CPCC 205547^T obtained from Erhai Lake in Yunnan - were characterized as Gram-stain-positive, orange to dark brown-pigmented actinobacteria. These isolates were mesophilic, exhibiting optimal growth at pH 7.0-8.0. Phylogenetic analyses based on 16S rRNA gene sequences placed these isolates within the genus Micromonospora, with high similarity (>99%) to Micromonospora solifontis NBRC 113441^T and Micromonospora veneta DSM 109713^T. Chemotaxonomic analyses (fatty acids, polar lipids and peptidoglycan) and the genomic G+C content further supported their classification within Micromonospora. However, whole-genome comparisons revealed distinct taxonomic relationships: strains CPCC 205556^T and CPCC 205543 shared 85.6-85.7% average nucleotide identity (ANI) and 33.5% digital DNA-DNA hybridization (dDDH) with Micromonospora auratinigra DSM 44815^T, while CPCC 205547^T shared 85.7% of ANI and 32.0% of dDDH with Micromonospora coxensis JCM 13248^T. Notably, CPCC 205556^T and CPCC 205543 exhibited near-identical genomic relatedness (ANI=99.3%, dDDH=93.3%), confirming their status as a single novel species. Based on these findings, two novel species were proposed: Micromonospora psammae sp. nov. (type strain CPCC 205556^T=MS1047^T=KCTC 59310^T), representing the desert isolates, and Micromonospora lacuserhaii sp. nov. (type strain CPCC 205547^T=EH501^T=KCTC 59309^T) from the lake habitat. Genomic analysis highlighted their biosynthetic potential for specialized metabolites, consistent with the genus's recognized metabolic diversity.