Unknown Widespread Iron- and Sulfur-Oxidizing Bacteria beneath the East Antarctic Ice Sheet

Abstract

Comparative analysis of the Vostok ice core (Central East Antarctica; one horizon, three boreholes) and D10 ice core (shoreline nearby the French Dumont d’Urville station) has reliably revealed three phylotypes (species) of aerobic iron-oxidizing betaproteobacteria of the family Gallionellaceae (closely related at the genus level to Sideroxydans lithotrophicus and Ferriphaselus amnicola), one of which has been detected from both the Vostok (borehole 5G-3) and D10 cores. In addition, the phylotype related to sulfur-oxidizing bacteria Tumebacillus sp. has been detected from both the Vostok (borehole 5G-2) and D10 cores. The both ice cores are almost equal in age, about 20 000 years; however, they differ in origin: the ice from Dumont d’Urville is atmospheric, while that from Vostok is a lake ice. The ice samples greatly vary in the storage time before treatment in the laboratory (from 0.5 to 40 years) and in intervals between treatments (from 1 to 5 years). The drilling sites are more than 1000 km apart. No evident hydrological links (the transfer of water beneath the ice sheet) between the Lake Vostok and Dumont D’Urville station have been found. This coincidence can be explained by the fact that minerals from the bedrock under the glacier, containing ferrous iron and reduced sulfur compounds, as well as physical and chemical conditions in both sites, liquid fresh water at a temperature near the freezing point, are similar. These and other assumptions are considered in the present article.