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The Karakoram Mountain Range (KMR) is one of the largest mountain ranges in the world, with ∼37% of its area glaciated. Glaciers harbor various microbes, including bacteria exposed to various extreme conditions. To thrive under these conditions, bacteria adopt various strategies, one of the most important being the production of pigments. Here, we present the geochemistry of ice, sediment and meltwaters sampled from Ghulmet, Ghulkin and Hopar glaciers of the Karakoram Range, Pakistan. In addition, we report the first information on the diversity of pigmented bacteria evaluated using a culture-dependent method and determined pigment production response of selected bacterial species to different temperatures. Geochemical analyses revealed Ca2+ and SO42– to be the most abundant cation and anion species across all glacial samples. Total organic carbon (TOC), total nitrogen (T.N.) and total phosphorus (T.P.) were found in the sediments of all glaciers studied in current research. Bacterial species were capable of producing a variety of different pigments, including alloxanthin, astaxanthin, bacterioruberin, β-carotene, 19'-hexanoyloxyfucoxanthin, peridinin, violacein and zeaxanthin. Culturable bacterial diversity based on two molecular biomarkers, 16S rRNA and rpoB gene, revealed total of 82 bacterial strains representing 25 genera across all glacial samples. This study provides the first characterization of glacier-associated, pigment-producing bacterial communities from the KMR. Findings are important for consideration of alternative sources of conventional pigment production in industrial fields. [ABSTRACT FROM AUTHOR]

Bacteria inhabiting non-polar glaciers are exposed to large variations in temperature, which significantly affects the fluidity of bacterial cell membranes. In order to maintain normal functions of the cell membranes, psychrophilic bacteria adapt by changing the composition of cell membrane fatty acids. However, information on the exact pattern of cell membrane adaptability in non-polar low-temperature habitats is scarce. In the present study, 42 bacterial strains were isolated from the Ghulmet, Ghulkin, and Hopar glaciers of the Hunza Valley in the Karakoram Mountain Range, Pakistan and their cell membrane fatty acid distributions studied, using gas chromatography/mass spectrometry (GC-MS) for the analysis of fatty acid methyl esters (FAMEs) liberated by acid-catalyzed methanolysis. Furthermore, Gram-negative and Gram-positive groups were grown under different temperature settings (5, 15, 25, and 35°C) in order to determine the effect of temperature on cell membrane (CM) fatty acid distribution. The analyses identified the major groups of cell membrane fatty acids (FA) as straight-chain monounsaturated fatty acids (n -MUFAs) and branched fatty acids (br -FAs), accounting for more than 70% of the fatty acids analyzed. The distribution of br-FAs and n -FAs in bacterial cell membranes was significantly affected by temperature, with the level of br-FAs decreasing relative to n -FAs with increasing temperature. Notably, the production of polyunsaturated fatty acids (PUFAs) was only seen at lower temperatures. This study contributes to understanding, for the first time, the role of br-FAs in the maintenance of cell membrane fluidity of bacteria inhabiting non-polar habitats. [ABSTRACT FROM AUTHOR]