Shiro Kohshima

Dark-colored material (cryoconite) covering Himalayan glaciers has been reported to greatly accelerate glacier-melting by reducing surface albedo. Structure, formation, and the darkening process of the cryoconite on a Himalayan glacier were analyzed. The cryoconite was revealed to be a stromatolite-like algal mat, a product of microbial activity on the glacier. The granular algal mat contains filamentous blue-green algae (cyanobacteria) and bacteria, and grows on the ice by trapping mineral and organic particles. This structure seems to enable high algal production in nutrient poor glacial meltwater by gathering and keeping nutrient rich particles inside. The dark coloration of the mats promotes melt-hole formation on the ice (cryoconite holes), providing a semistagnant aquatic habitat for various algae and animals in the glacier. Optical and chemical analyses of the cryoconite strongly suggests that their high light- absorbency (dark coloration) is mainly due to dark-colored humic substances, residues from bacterial decomposition of the algal products and other organic matter. Our results strongly suggest that biological activity on the glacier substantially affects the albedo of the glacier surface. The structure of the algal mat seems to be important in the glacier ecosystem and biological process affecting glacier albedo.

Antibiotic resistance genes are biologically transmitted from microorganism to microorganism in particular micro-environments where dense microbial communities are often exposed to an intensive use of antibiotics, such as intestinal microflora, and the soil microflora of agricultural fields. However, recent studies have detected antibiotic-resistant bacteria and/or antibiotic resistance genes in the natural environment geographically isolated from such areas. Here we sought to examine the prevalence of antibiotic resistance genes in 54 snow and ice samples collected from the Arctic, Antarctic, Central Asia, North and South America and Africa, to evaluate the level of these genes in environments supposedly not affected by anthropogenic factors. We observed a widespread distribution of antibiotic resistance genes in samples from various glaciers in Central Asia, North and South America, Greenland and Africa. In contrast, Antarctic glaciers were virtually free from these genes. Antibiotic resistance genes, of both clinical (i.e. aac(3), blaIMP) and agricultural (i.e. strA and tetW) origin, were detected. Our results show regional geographical distribution of antibiotic resistance genes, with the most plausible modes of transmission through airborne bacteria and migrating birds.

The bacterial flora and biomass in mountain snow from the Tateyama Mountains, Toyama Prefecture, Japan, one of the heaviest snowfall regions in the world, were analyzed by amplified ribosomal DNA restriction analysis followed by 16S rRNA gene sequencing and DNA quantification by real-time PCR. Samples of surface snow collected in various months during the melting season contained a psychrophilic bacterium, Cryobacterium psychrophilum, and two psychrotrophic bacteria, Variovorax paradoxus and Janthinobacterium lividum. Bacterial colonies that developed in an in situ meltwater medium at 4 degrees C were revealed to be V. paradoxus. The biomasses of C. psychrophilum, J. lividum, and V. paradoxus, as estimated by real-time PCR, showed large increases during the melting season from March to October (2.0 x 10(5)-fold, 1.5 x 10(5)-fold, and 1.0 x 10(4)-fold increases, respectively), suggesting their rapid growth in the surface snow. The biomasses of C. psychrophilum and J. lividum increased significantly from March to April, reached a maximum in August, and dropped at the end of the melting season. In contrast, the biomass of V. paradoxus did not increase as rapidly during the early melting season but continued to increase from June until October. The differences in development observed among these bacterial species suggest that their growth was promoted by different nutrients and/or environmental conditions in the snow. Since these three types of bacteria have also been reported to be present in a glacier in Antarctica and a Greenland ice core, they seem to be specialized members of the snow biota that are distributed in snow and ice environments in various parts of the world.