Uric acid-degrading bacteria in the gut of the invading apple snail Pomacea canaliculata and their possible symbiotic significance

In previous studies we have mapped uric acid deposits in specialized tissues of the invading apple snail Pomacea canaliculata. Uric acid stores function as reservoirs of combined nitrogen in insects. The first step for recycling uric acid nitrogen involves the action of uricase and here we explored the occurrence of uricase-positive bacteria in the gut of this snail. Six bacterial strains assigned to the genera Pseudomonas, Enterobacter, Citrobacter and Lactococcus were isolated on the basis of their ability to grow in vitro in a medium containing uric acid as the only carbon and nitrogen source. Uricase specific activity could be determined in three of these genera (not in Citrobacter), showing optimal pH values ranging 7.3–8.7 and optimal substrate concentrations (ranging 25–30 μM). These uricolytic bacteria may participate in recycling of combined nitrogen in this snail.