Description of high-altitude, cold-adaptive, metabolically versatile Dyadobacter aurulentus sp. nov. isolated from Western Himalayan farmland soils.

A novel bacterial strain, designated UC10^T, was isolated from cold, high-altitude farmland soil in the Gangotri region of the Western Himalayas, India. The strain is Gram-stain-negative, aerobic, non-spore forming, and non-motile, forming golden colonies that produce a flexirubin-like pigment. Strain UC10^T grows over a broad range of temperatures (5°C-30°C), pH (6-11), and salinities (up to 4% NaCl), with optimal growth at 30°C, pH 7.0, and 1% NaCl. The nearly full-length 16S rRNA gene sequence (MK743979) shares 98.95% similarity with Dyadobacter luticola, followed by 97.68% with Dyadobacter crusticola and 97.40% with Dyadobacter koreensis, and phylogenetic analysis places UC10ᵀ in a distinct clade within the genus Dyadobacter. Whole-genome phylogenetic analyses revealed that UC10^T is closely related to Dyadobacter linearis, D. crusticola, and D. luticola but is clearly distinguished from them by low average nucleotide identity (<81%), digital DNA-DNA hybridization (<24%), and amino acid identity (<80%) values. The genome of UC10^T is 6.93 Mb with a G+C content of 46.5 mol% and encodes multiple cold adaptation-related genes, including cold-shock proteins and fatty acid desaturases. The strain also harbors genes for aromatic compound degradation and demonstrated the ability to grow in minimal medium containing sodium benzoate as the sole carbon source. Additionally, fatty acid and polar lipid profiles of UC10^T revealed unique compositions, further supporting its differentiation. The combined genomic, phenotypic, and chemotaxonomic evidence supports the designation of strain UC10^T as representing a novel species, for which the name Dyadobacter aurulentus sp. nov. is proposed. The type strain is UC10^T (= MCC 4019^T = KCTC 72455^T = JCM 34514^T).

Importance: High-altitude, cold habitats such as the Gangotri region of the Western Himalayas remain underexplored for culturable microbial diversity. Here, we describe Dyadobacter aurulentus sp. nov., a novel cold-adapted species isolated from such an environment. This strain demonstrates unique ecological and metabolic traits, including growth at low temperatures and degradation of aromatic compounds like sodium benzoate. Genomic analysis revealed key cold adaptation features such as cold-shock proteins, fatty acid desaturases, nitrate assimilation pathways, and multidrug resistance genes, supporting survival in nutrient-limited, low-temperature soils. The strain's distinct chemotaxonomic profile, marked by elevated C_16:0 and unique polar lipids, underscores its ecological specialization. Together, these features point to its potential utility in bioremediation and cold-environment biotechnology. This study broadens our understanding of the adaptive strategies and ecological functions of Dyadobacter spp. in extreme environments, with implications for bioprospecting cold-active enzymes and understanding resistance evolution in high-altitude microbial communities.