Cryo-adapted bacterial copiotrophs from a Trans-Himalayan lake-desert ecosystem as biogeothermometers of warming and mitigators of microbiome perturbation

A Trans-Himalayan lake-desert ecosystem was explored for the low-to-high temperature adaptations of copiotrophic psychrophiles having potentials for substantive carbon remineralization under natural and/or anthropogenically-influenced conditions of high organic matter delivery to the cryospheric environment. Overall 27 bacterial species were isolated from the brackish-water and sediment-surface of Tso Moriri (a massive lake on the Changthang plateau that remains frozen for approximately one third of the year), and the fine talus covering a lake-side rocky mountain. In Luria broth (LB), all isolates grew at 4°C and 15°C; at -10°C, 13 could grow while others remained only metabolically-active. Catabolizing different complex-organic-compounds, all isolates achieved considerable growth at 4°C; 20 accomplished low growth at -10°C. LB-based growth dwindled with rising temperature: 23, 11, and none of the isolates grew at 28°C, 37°C, and 42°C respectively. The isolates’ genomes, and the habitats’ metagenomes, encompassed diverse genes for extreme-temperature adaptation and carbohydrate catabolism. Within high-altitude cryospheres, cessation of organotrophy, in general, would cut-back simple fatty acids, CO ₂ and N ₂ O production (short-supply of CO ₂ and acetate would in turn cutback methanogenesis, if the concerned archaea are present in situ ). Such negative feedback controls of greenhouse gas production at the micro-habitat level can add-up in the biome-scale to mitigate broader environmental warming. However, homeostasis via abolition of growth for indigenous psychrophiles is fraught with the danger of ecosystem takeover by thermally-better-adapted foreign microbes. At 28°C, majority of the actinobacterial isolates inhibited bacteria from discrete warmer habitats; they can, therefore, be viewed as potential defenders of the cold/frigid ecosystem.