ENDOLITHIC CYANOBACTERIA IN SOIL SULFATES FROM HYPERARID ENVIRONMENTS ON EARTH

Soil sulfates are present in arid and hyperarid soils on Earth and have been found to be abundant within soils on Mars. Examination of hand samples of soil gypsum from the Atacama Desert, Chile, the Mojave Desert, USA, and Al-Jafr Basin, Jordan, revealed thin green layers located just below the surface on all soil gypsum samples. Scanning electron microscope observations of the green layer detected close association of microbe-like objects and gypsum. Culture-dependent and –independent techniques were employed to study microbial communities in all samples. Microscopic observations of enrichment samples from the green layers revealed microbial morphologies that are characteristic of Chroococcidiopsis. 16S rRNA gene analysis of both the enrichment culture and the original gypsum rock revealed that the majority of the cloned sequences from the green layer from all three types of samples are related to the genus Chroococcidiopsis with a similarity value of 90-95%. These initial results demonstrate the presence of endolithic cyanobacteria in soil sulfates from some of the driest places on Earth and suggests that similar habitats may have been colonized on Mars if life was present.