Isoptericola haloaureus sp. nov., a dimorphic actinobacterium isolated from mangrove sediments of southeast India, implicating biosaline agricultural significance through nitrogen fixation and salt tolerance genes

Abstract

Strain MP-1014^T, an obligate halophilic actinobacterium, was isolated from the mangrove soil of Thandavarayancholanganpettai, Tamil Nadu, India. A polyphasic approach was utilized to explore its phylogenetic position completely. The isolate was Gram-positive, filamentous, non-motile, and coccoid in older cultures. Ideal growth conditions were seen at 30 °C and pH 7.0, with 5% NaCl (W/V), and the DNA G + C content was 73.3%. The phylogenic analysis of this strain based upon 16S rRNA gene sequence revealed 97–99.8% similarity to the recognized species of the genus Isoptericola. Strain MP-1014^T exhibits the highest similarity to I. sediminis JC619^T (99.7%), I. chiayiensis KCTC19740^T (98.9%), and subsequently to I. halotolerans KCTC19646^T (98.6%), when compared with other members within the Isoptericola genus (< 98%). ANI scores of strain MP-1014^T are 86.4%, 84.2%, and 81.5% and dDDH values are 59.7%, 53.6%, and 34.8% with I. sediminis JC619^T, I. chiayiensis KCTC19740^T and I. halotolerans KCTC19646^T respectively. The major polar lipids of the strain MP-1014^T were phosphatidylinositol, phosphatidylglycerol, diphosphotidylglycerol, two unknown phospholipids, and glycolipids. The predominant respiratory menaquinones were MK₉ (H₄) and MK₉ (H₂). The major fatty acids were anteiso-C_15:0, anteiso-C_17:0, iso-C_14:0, C_15:0, and C_16:0. Also, initial genome analysis of the organism suggests it as a biostimulant for enhancing agriculture in saline environments. Based on phenotypic and genetic distinctiveness, the strain MP-1014 ^T represents the novel species of the genus Isoptericola assigned Isoptericola haloaureus sp. nov., is addressed by the strain MP-1014 ^T, given its phenotypic, phylogenetic, and hereditary uniqueness. The type strain is MP-1014^T [(NCBI = OP672482.1 = GCA_036689775.1) ATCC = BAA 2646^T; DSMZ = 29325^T; MTCC = 13246^T].