Abstract
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 ~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.
Highlights
Glacier ice has recently gained recognition as a biome driven exclusively by microorganisms [1, 2]
Considering the significance of such bacteria from physical extremes of temperature and radiation, we conducted Multilocus sequence analysis (MLSA) of eleven strains of Pseudomonas genus obtained from the supraglacial site of East Rathong glacier to resolve its taxonomy. To check their adaptive features and to establish the fact that this unique group of bacteria is the inhabitants of the pristine supraglacial environment, we investigated their survivability in physical conditions of freezing and UV radiation and examined their ability to produce extracellular cold-active enzymes
Ten strains grew over a pH range of 4–12, while one strain showed growth in the pH range of 5–12
Summary
Glacier ice has recently gained recognition as a biome driven exclusively by microorganisms [1, 2]. Encompassing the topmost layer of ice, the supraglacial zone receives ample sunlight and is subjected to the deposition of microbial cells plus nutrients by the wind [3]. The liquid water produced during the surface melting of ice promotes and supports a rich microbial life on the glacial surfaces [3, 4]. Taxonomy and adaptation of Pseudomonas from Sikkim Himalaya
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