N-163. Richness and Endemicity of Sulfate-Reducing Bacteria for the Elfin Forest in Puerto Rico

C. E. Bonilla-Rivera, J. R. Perez-Jimenez;
Univ. del Turabo, Gurabo, PR.

The prevalence of sulfate-reducing bacteria (SRB) has not been well-documented from terrestrial ecosystems as for seawater-related settings (deep-sea, estuarine, and manglal sediments). The elfin forest (cloud forest) develops at high elevations with very dense stands of stunted trees and shrubs, water-saturated soils, heavy rain, strong winds, and relative cool temperature. Our objective is to assess the richness and endemicity of SRB in the elfin forest at El Yunque Rain Forest (Puerto Rico, USA). Soil samples collected during June and December 2005 from plots at different depths (0-5 cm, 5-10 cm) were studied. Total genomic DNA was extracted for PCR amplification of the dissimilatory sulfite reductase gene (dsrAB) and Terminal Restriction Fragment Length Polymorphisms (TRFLP) analysis of their NdeII digests. Also, dsrAB amplicons were cloned for sequencing. A diverse sulfidogenic community is comprised by 419 TRFs (representing 144 sizes) among the set of samples analyzed so far. Four TRFs (2.8%) are shared and 48 (33%) are unique among samples. The profiles are dominated by minor peaks. Heterogeneity of sulfidogenic communities, represented by unique TRFs, is evident among plots (47.8%), depth (38.8%), and seasons (80%). SRB are more predominant for June and the deeper layer (5-10 cm). In order to describe the endemicity, a clonal library is being sequenced. Preliminary efforts retrieved sequences related to dsrAB cloned from China, Japan, deep-sea, and United Kingdom. Soil samples from additional seasons are being analyzed for further insights into the SRB richness. Spatialy and temporally diverse SRB are found within the elfin forest. Sulfidogens, known versatile degraders, seem to thrive within the saturated soils of the elfin forest with a potential role on decomposing complex substances from decaying trees.