Gut bacteria recycle uric acid nitrogen in termites: A strategy for nutrient conservation

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Abstract
Reticulitermes flavipes termites synthesize uric acid via purine-nucleoside phosphorylase (EC 2.4.2.1) and xanthine dehydrogenase (EC 1.2.1.37), but their tissues lack uricase (EC 1.7.3.3) or any other enzyme that degrades uric acid. Uricolysis occurs in termites, but as an anaerobic process mediated by hindugt bacteria. 14C-Tracer experiments showed that termites transport uric acid from the site of synthesis and storage (fat body tissue) to the site of degradation (hindgut microbiota) via Malpighian tubules. [1,3-15N]uric acid dissimilated by gut bacteria in vivo leads to assimilation of 15N into termite tissues. NH3, a product of uricolysis, is a potential N source for termites, either directly via glutamine synthetase (EC 6.3.1.2) activity of fat body tissue or indirectly through microbe assimilation. Symbiotic recycling of uric acid N appears to be important to N conservation in these oligonitrotrophic insects. [Streptococcus sp. and Bacteroides termitidis were predominant among the bacteria isolated.].