Mining novel Streptomyces species from extreme environments provides a valuable strategy for the discovery of new antibiotics. Here, we report a strain of Streptomyces sp. HMX87^T, which exhibits antimicrobial activity and was isolated from desert soil collected in the Tuha Basin, China. Molecular taxonomic analysis revealed that the 16S rRNA gene sequence of strain HMX87^T shares the highest similarity with those of Streptomyces bellus CGMCC 4.1376^T (98.5%) and Streptomyces coerulescens DSM 40146^T (98.43%). In phylogenetic trees, it formed a distinct branch. The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain HMX87^T and the above two type strains were below the thresholds of 95% and 70%, respectively, confirming that strain HMX87^T represents a novel species within the genus Streptomyces, for which the name Streptomyces hamibioticus sp. nov. is proposed. Physiologically, the strain HMX87^T grew at temperatures ranging from 25 to 37 °C, tolerated pH values from 5 to 12, and survived in NaCl concentrations of 0% to 8% (w/v). Chemotaxonomic characterization indicated the presence of LL-diaminopimelic acid (LL-DAP) in the cell wall, ribose and galactose as whole-cell hydrolysate sugars, MK-9(H8) (66.3%) as the predominant menaquinone, and iso-C_16:0 (25.94%) and anteiso-C_15:0 (16.98%) as the major fatty acids characteristics that clearly distinguish it from its closest relatives. Whole-genome sequencing of strain HMX87^T revealed an abundance of genes associated with high-temperature tolerance, salt-alkali resistance, and antimicrobial activity. The genomic features and secondary metabolic potential reflect its adaptation to extreme environmental conditions, including high temperature, salinity, alkalinity, strong ultraviolet radiation, and oligotrophic nutrients. The strain HMX87^T has been deposited in the Czech Collection of Microorganisms (CCM 9454^T) and the Guangdong Microbial Culture Collection Center (GDMCC 4.391^T). The 16S rRNA gene and whole-genome sequences have been submitted to GenBank under accession numbers PQ182592 and PRJNA1206124, respectively.

Acyl-CoA carboxylase (YCC) complexes generate essential starter and extender units for fatty acid and polyketide biosynthesis in Actinobacteria. In Streptomyces coelicolor, two tri-subunit YCC complexes, acetyl-CoA carboxylase (ACC) and propionyl-CoA carboxylase (PCC), have been characterized. However, comparative genomic analyses indicate that β/ε subunits are more diversified than currently appreciated. Here, we identify a previously unrecognized β/ε pair, AccB2 and AccE2, and demonstrate that they assemble with the canonical α subunit to form a functional YCC complex. Both genes are transcribed in vivo, and co-immunoprecipitation (Co-IP) reveals association with AccA1 and AccA2, with AccE2 showing stronger relative association with AccA1-containing pull-downs. In vitro reconstitution confirms carboxylation activity toward acetyl-CoA, propionyl-CoA, and butyryl-CoA, which is strongly dependent on AccE2. These findings expand the YCC repertoire in S. coelicolor and support a modular assembly model in which alternative β/ε combinations contribute to functional diversification of YCC complexes.

Water-soluble blue microbial pigments with antioxidant activity remain rare, and their host-level protective mechanisms are poorly understood. Here, we identified the genetic basis of blue pigment biosynthesis in the glacier-derived strain Arthrobacter antioxidans QL17. Heavy-ion mutagenesis yielded a hyperpigmented mutant (M157) and a pigment-deficient mutant (M186), and pigment yield was positively associated with hydrogen peroxide (H₂O₂) tolerance. Genome mining identified MWM45_RS16760 as the sole core biosynthetic gene in a candidate nonribosomal peptide synthetase (NRPS)-like cluster. The encoded protein displayed an adenylation–peptidyl carrier protein–thioesterase (A-PCP-TE) architecture with a predicted L-glutamine-specific A domain, and its transcript abundance paralleled pigment production across the three strains. Phylogenetic analysis placed MWM45_RS16760 in a distinct actinomycete-associated indigoidine-like lineage separated from the characterized BpsA and IndC branches. Heterologous expression in Escherichia coli reconstructed a blue-pigment-producing phenotype, increased H₂O₂ tolerance, and was accompanied by enhanced extracellular DPPH and ABTS radical-scavenging activities in the culture supernatant. Comparative transcriptomics further revealed coordinated activation of oxidative-stress and proteostasis responses alongside repression of tryptophan biosynthesis and flagellar assembly. These findings identify MWM45_RS16760 as a candidate indigoidine-like NRPS associated with blue pigment biosynthesis and oxidative-stress resistance, with heterologous expression linked to enhanced radical scavenging and coordinated transcriptional reprogramming, expanding the phylogenetic and functional diversity of indigoidine-like systems.