RUI-Microbial Observatories: Diversity of Halophilic Bacteria and Geochemical Signatures in a Tropical Solar Saltern

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A grant has been awarded to Drs. Lilliam Casillas and Carmen Hernandez (University of Puerto Rico-Humacao) and Pieter Visscher (University of Connecticut) to establish a Microbial Observatory in the Cabo Rojo solar salterns of Puerto Rico. The salterns provide an excellent setting for the study of life under extreme conditions due to the intense solar radiation, high wind velocity and salinity at the site. Using molecular tools different halophilic (i.e. salt-loving) organisms present at the site during wet and dry periods will be identified. Once such halophiles have been identified, some of their metabolic activities such as photosynthesis, aerobic respiration, sulfate reduction and nitrogen fixation will be studied. Using microelectrodes, in situ activities of the halophiles in the cyanobacterial mats and their contributions to the productivity of the site will be studied. At the same time, the chemical and geological composition of the sediments of the mats and the water column of the salt ponds will be identified. The main goal of this research is to understand how the various biological, chemical and geological processes act in concert to define the hypersaline ecosystems of Cabo Rojo.These studies will provide a scenario, as complete as possible, of the chemical and geological conditions in a Caribbean tropical saltern and establish the role of microorganisms in this ecosystem. Studies of this nature in the Caribbean are limited. While accessing the microbial diversity of the site it is anticipated that new organisms with novel adaptations and/or physiologies will be isolated. Special focus will be placed on the role of halophilic microorganisms in the geochemical transformations required for life to flourish. As hypersaline environments are known to have existed since Precambrian times, study of the Cabo Rojo salterns should shed light on how microorganisms and their by products could possibly have contributed in the past to establish present ecosystems.