Olmo Fontánez, Angélica M.

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    Diversity of bacteria associated with the mangrove fiddler crab, Uca rapax, in Boquerón, Puerto Rico and their cellulose degradation capacity
    (2013) Olmo Fontánez, Angélica M.; Cafaro, Matías J.; College of Arts and Sciences - Sciences; Montalvo Rodríguez, Rafael; Santos Flores, Carlos J.; Department of Biology; Rodríguez, Áurea
    Mangrove habitats are considered one of the most productive ecosystems in the world, and are very important because they are habitats for many microorganisms and marine invertebrates, such as fiddler crabs. Fiddler crabs (Uca rapax) are small deposit-feeders crustaceans, hence the particles found in mangrove sand and especially detritus are part of their diet. Their primary ecological role is the recycling of organic matter; also by burrowing deep into the mud, they create tunnels that aerate the estuarine soil, what promotes aerobic conditions. Mangrove soils contain mainly lignocellulose components, cellulases are secreted by soil microorganisms, yet it is not known if fiddler crabs’s gut microflora is able to do so also. The gut microbes might contribute to the host nutritional fitness, especially by increasing the extracellular enzymes to degrade organic matter, such as lignocellulose. First, we compared the bacterial communities from mangrove soil and the hindgut microflora of fiddler crabs during the wet and dry seasons using culture-dependent methods (Chitin media, Lenox broth (LB) media, Marine agar and Mangrove soil agar). Bacterial isolates were then identified through 16S rDNA gene amplification and sequencing. UniFrac analysis found significant differences between mangrove soil and hindgut microflora bacterial communities only in the wet season. To identify specific bacterial communities associated with the hindgut of Uca rapax, we compared the genera present there with those in the soil. Vibrio was the only genus that was consistently isolated from the hindgut (in both seasons), but never detected in mangrove soil; although it was isolated at a low frequency (3.8%). We studied cellulose degradation, using carboxymethylcellulose (CMC) as carbon source in order to identify cellulase producing bacteria associated with the hindgut of Uca rapax; where more than 80% were positive cellulase producers under laboratory conditions. The statistical analysis showed significant differences in cellulose degradation capacity among bacterial strains suggesting that some strains have different enzymatic capabilities when degrading cellulose. Our results could suggest that the hindgut microflora of Uca rapax, is involved in the recycling of carbon. This implies that the activity of cellulases makes an important contribution to the nutrition by converting cellulose into simpler carbohydrates prior to the ingestion of detritus by the fiddler crabs.