Multilocus sequence based identification and adaptational strategies of Pseudomonas sp. from the supraglacial site of Sikkim Himalaya

Microorganisms inhabiting the supraglacial ice are biotechnologically significant as they are equipped with unique adaptive features in response to extreme environmental conditions of high ultraviolet radiations and frequent freeze-thaw. In the current study, we obtained eleven strains of Pseudomonas from the East Rathong supraglacial site in Sikkim Himalaya that showed taxonomic ambiguity in terms of species affiliation. Being one of the most complex and diverse genera, deciphering the correct taxonomy of Pseudomonas species has always been challenging. So, we conducted multilocus sequence analysis (MLSA) using five housekeeping genes, which concluded the taxonomic assignment of these strains to Pseudomonas antarctica. This was further supported by the lesser mean genetic distances with P. antarctica (0.73%) compared to P. fluorescens (3.65%), and highest ANI value of similar to 99 and dDDH value of 91.2 of the representative strains with P. antarctica PAMC 27494. We examined the multi-tolerance abilities of these eleven Pseudomonas strains. Indeed the studied strains displayed significant tolerance to freezing for 96 hours compared to the mesophilic control strain, while except for four strains, seven strains exhibited noteworthy tolerance to UV-C radiations. The genome-based findings revealed many cold and radiation resistance-associated genes that supported the physiological findings. Further, the bacterial strains produced two or more cold-active enzymes in plate-based assays. Owing to the polyadaptational attributes, the strains ERGC3:01 and ERGC3:05 could be most promising for bioprospection.

Automated summary

In this study, eleven strains of Pseudomonas were obtained from the East Rathong supraglacial site in Sikkim Himalaya. Through multilocus sequence analysis, these strains were identified as Pseudomonas antarctica. The strains showed significant tolerance to freezing and UV-C radiations, and the genome analysis revealed cold and radiation resistance-associated genes.