Advances in the Study of Phytases and Phosphatases in Bacteria Associated with Plants Grown in Chilean Extreme Environments.

Bacteria are relevant for nutrient recycling in nature. The ability of bacteria to mobilize insoluble organic phosphorus (Po) forms in soils has been attributed to their capacity to produce P-hydrolyzing enzymes. In rhizosphere soils, bacterial phytases and phosphatases are responsible for hydrolyzing Po to inorganic phosphate for plant nutrition and their genes used as molecular markers. However, the abundance and diversity of both bacterial enzyme genes in soils and plants are poorly known, especially in extreme environments. During recent years, we have used culture-dependent and culture-independent approaches to study the total bacterial communities and the occurrence of beta-propeller phytase (BPP) and alkaline phosphomonoesterases (APase) genes in bacteria associated with soils and plants in Chilean extreme environments (Atacama Desert, Andes Mountain, Patagonia and Antarctica). Our results have showed differences in the composition of total bacterial communities between extreme environments and plant species. Lower bacterial diversities were observed in Atacama Desert than other extreme environments and some phytate-hydrolyzing isolates (identified as Bacillus) showed BBP genes in their genome as revealed by PCR. However, and despite extensive PCR optimization used, results showed numerous unspecific amplification with poor or no identity to known BPP genes, demonstrating our insufficient knowledge on bacterial phytases to provide adequate coverage of bacterial phytase genes in nature. Respect to APase, the gene abundances and APase activities were also lower in soils from Atacama Desert, whereas the highest values were observed in Patagonia. In addition, APase gene abundances were positively correlated with APase activity of soils, but negatively correlated with P availability. Although bacterial phytase and phosphatase genes were observed in all studied samples, their relevance to soil Po recycling in soils and their contribution to P nutrition in plants from extreme environments remains unclear and further studies are needed. Acknowledgments: Fondecyt no. 1160302.