Genomic insights into Marinospirillum alkalitolerans sp. nov., a novel PHB producing bacterium from an Indian impact crater, and an emended description of family Oceanospirillaceae

Abstract

Two Gram-stain-negative bacterial strains (MEB164^T and MEB148), were isolated from haloalkaline waters of Lonar, crater lake, India. The strains were helical, non-spore-forming and motile with polar tufts of flagella. Optimal growth occurred at 37 ℃, at pH 10 and with 3% (w/v) NaCl. 16S rRNA gene sequences of strains (MEB164^T and MEB148) demonstrated the highest similarity with Marinospirillum alkaliphilum DSM 21637^T (97.8%) followed by Marinospirillum celere DSM 18438^T (96%). The genome size of strain MEB164^T was determined to be 2.8 Mb with genomic DNA G + C contents of 53.1 mol %. ANI and dDDH values between strain MEB164^T and the most closely related type strain M. alkaliphilum DSM 21637^T were (72.3% and 21.4 ± 2.3%) while (AAI and POCP) values were (66.8 and 70.8%), respectively. Strain MEB164^T exhibited potential for polyhydroxybutyrate (PHB) production, supported by key genes involved in PHB metabolism. Genome analysis further revealed presence of various pH tolerance genes, highlighting its adaptation to Lonar Lake. The predominant cellular fatty acids were summed feature 8 (C_18:1 ω7c/C_18:1 ω6c), C_16:0 and summed feature 3 (C_16:1 ω7c/C_16:1 ω6c). The major respiratory quinone was ubiquinone-8. The prevalent polar lipids were diaminophosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified amino phospholipids, three unidentified phospholipids and one unidentified lipid. Polyphasic analysis suggests that the two strains constitute a novel species within the genus Marinospirillum (family Oceanospirillaceae), proposed as Marinospirillum alkalitolerans sp. nov. The type strain is MEB164^T (= JCM 35957^T = MCC 5207^T = NCIMB 15458^T) and MEB148 (= JCM 35956 = MCC 5212 = NCIMB 15459) is an additional strain.