The latitudinal gradient in rock-inhabiting bacterial community compositions in Victoria Land, Antarctica.

The harsh conditions in Victoria Land, Antarctica have formed a simple ecosystem dominated by microbes that use rocks as shelters to avoid environmental stressors. The area is composed of basement rocks that illustrate the history of complex deformation, thus it is highly valuable not only in perspectives of geology but also in biological aspects. Because this region is inhospitable to higher-level organisms and receives least external influences, it can be an ideal environment to investigate the relationship between rock-inhabiting bacterial communities and environmental factors. In such conditions, inorganics dissolved from minerals can be considered as key factors influencing rock-inhabiting bacterial communities. Thus, the present study attempted to explore rock-inhabiting bacterial communities throughout Victoria Land, to identify environmental parameters that are more influential on bacterial community compositions, and to investigate latitudinal gradients in environmental parameters and rock-inhabiting bacterial communities. The results suggested that (i) rock-inhabiting bacterial communities in Victoria Land predominately consisted of either Actinobacteria or Proteobacteria; (ii) latitudinal gradients in rock-inhabiting bacterial community compositions and some environmental parameters were observed; (iii) latitude, pH, nitrate, and sulfate significantly correlated with the dominant phyla; and (iv) the Classification and Regression Tree (CART) analysis demonstrated that latitude, pH, and sulfate concentrations could explain the dominant phylum with 89% accuracy. These findings can provide important insight into the link between environmental factors and rock-inhabiting bacterial community compositions in conditions with extremely cold temperatures and high levels of radiation, which could also be of interest in astrobiology.