Glaciochemistry and Pigment Producing Ability of Bacteria from the Roof of the World, the Glaciers of Karakoram, Pakistan

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 SO₄^2– 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.