Ammonia-Oxidizing Archaea Communities at El Yunque Rain Forest in Puerto Rico

Archaea has a key role in ammonia oxidation reactions in the first step of Nitrification. The tropical rain forest El Yunque has a gradient of climate that changes and extends through four life zones (subtropical moist forest to lower montaneforest): Tabonuco, Colorado, Elfin, and Palm.  We hypothesize that a diverse community of ammonia-oxidizing archaea (AOA) prevails across the life zones of El Yunque. Our objective is to ascertain the richness and distribution of AOA communities along microclimates throughout the elevation gradient. Genomic DNA was extracted from soil samples collected in June 2005.  AOA communities were characterized with terminal restriction fragment length polymorphisms of the archaeal ammonia-onooxygenase gene (arch-amoA) amplified from soil samples.  A total of 249 phylotypes (TRF) were detected (representing 224 different TRF’s). TRF abundance ranged among forest from 191 (palm), 31 (Colorado), 20 (Tabonuco), and 5 (Elfin).  A total of 209 phylotypes appeared once in the samples, representing 93% of the communities. Similarity analysis, based on the Sorensen’s index showed great diversity (ranging from 0-96%) without geographical clustering.  The TRFLP analysis presented a broad diversity of archaeal communities through the microclimate of El Yunque. According to the Sorensen's similarity index, diversity appears to be driven by the microclimate of each forest. That suggests that the AOA communities found in the tropical forest take part of a specific microclimate that provides the nutrients they need in a more convenient form.  By comparing microbial diversity along this gradient, we contribute to understand general properties that underlie the dynamics of ecosystems.