BACTERIAL COMMUNITY STRUCTURE OF SOILS OF A HYPER-ARID REGION OF THE ATACAMA DESERT, CHILE

The hyper-arid Atacama Desert of northern Chile is arguably the driest region on Earth and thus, provides a unique opportunity to examine the influence of aridity on bacterial diversity. Soils were sampled along an east-west, regional elevational transect (Punta Negra, 23.75-24.70°S, 400-4500 m) near the driest sector to document the presence of bacterial populations and to compare the relative structure of bacterial communities throughout the transect. Statistical analysis of DNA profiles generated from each of the samples taken along the Punta Negra transect revealed that microbial communities from the extreme hyper-arid core of the desert clustered separately from all of the remaining communities. The microbial community clusters could not be explained by observed differences in soil properties or vegetation indices. The results suggest that bacterial community profiles could serve as more effective indicators of extreme hyperaridity in the Atacama Desert than the presence of perennial vegetation. The DNA profile of a sample taken from this core region was compared to that of a second sample taken 22 months later from the same area. Bands from both profiles were sequenced and identified to evaluate the relative permanence of the populations. Four of the five organisms identified from the second sample were also present among the seven unique organisms identified from the first sample confirming the existence of stable bacterial populations in this hyper-arid region. The majority of the bacteria identified belonged to divisions not typically dominant in arid soils suggesting that the hyperaridity may select for bacteria of specific divisions.