Taxonomic Characterization, Whole-Genome Sequencing, and Cosmetic Potential of Lysinibacillus sp. JNUCC 51 Isolated from Baengnokdam Crater Lake, Mt. Halla

A novel bacterial strain, <i>Lysinibacillus</i> sp. JNUCC 51, was isolated from volcanic soil collected at Baengnokdam Crater Lake, Mt. Halla, Jeju Island, Republic of Korea. Phylogenetic, ANI (88.76%), and dDDH (70.4%) analyses indicated that the strain represents a distinct genomic lineage closely related to <i>L. xylanilyticus</i>. The complete genome (5.12 Mb; 37% G+C) encoded 4912 genes, including ten biosynthetic gene clusters (NRPS, β-lactone, RiPP, terpene, and T3PKS types), suggesting strong metabolic versatility. Cells were Gram-positive rods (1.5-3.0 × 0.5-0.7 µm) growing at pH 4.0-9.0 and up to 5% NaCl. Chemotaxonomic profiles revealed iso-C₁₅:₀, iso-C₁₇:₀, and iso-C₁₆:₀ as dominant fatty acids; MK-6/MK-7 as major quinones; and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylcholine as main polar lipids. Bioactivity-guided fractionation of the culture extract led to the isolation of Diolmycin A2 (phenolic polyketide) and maculosin (diketopiperazine), both exhibiting anti-inflammatory and melanogenesis-inhibitory effects consistent with their PKS/NRPS gene clusters. The culture broth suppressed nitric oxide production in LPS-stimulated RAW 264.7 macrophages and reduced melanin synthesis in α-MSH-induced B16F10 melanocytes. A human patch test (5% extract) confirmed dermatological safety. Overall, <i>Lysinibacillus</i> sp. JNUCC 51 is a volcanic-origin bacterium producing structurally diverse bioactive metabolites with promising postbiotic and cosmeceutical potential, particularly for skin inflammation and pigmentation control.