Anaerobic Degradation of Uric Acid by Gut Bacteria of Termites

Abstract

A study was done of anaerobic degradation of uric acid (UA) by representative strains of uricolytic bacteria isolated from guts of Reticulitermes flavipes termites. Streptococcus strain UAD-1 degraded UA incompletely, secreting a fluorescent compound into the medium, unless formate (or a formicogenic compound) was present as a cosubstrate. Formate functioned as a reductant, and its oxidation to CO2 by formate dehydrogenase provided 2H+ + 2e-needed to drive uricolysis to completion. Uricolysis by Streptococcus UAD-1 thus corresponded to the following equation: 1UA + lformate-. 4CO2 + lacetate + 4NH3. Urea did not appear to be an intermediate in CO2 and NH3 formation during uricolysis by strain UAD-1. Formate dehydrogenase and uricolytic activities of strain UAD-1 were inducible by growth of cells on UA. Bacteroides ternitidis strain UAD-50 degraded UA as follows: 1UA-* 3.5 CO2 + 0.75acetate + 4NH3. Exogenous formate was neither required for nor stimulatory to uricolysis by strain UAD-50. Studies of UA catabolism by Citrobacter strains were limited, because only small amounts of UA were metabolized by cells in liquid medium. Uricolytic activity of such bacteria in situ could be important to the carbon, nitrogen, and energy economy of R. flavipes.

Volatile Fatty Acid Production by the Hindgut Microbiota of Xylophagous Termites

“…6 include a graphic representation of reactions A, F, and B (Table 5). Also depicted in this figure is the participation (to a lesser degree) of other heterotrophic bacteria in acetogenesis, either directly or indirectly through H2 and CO2 production (42,43,48,49). As with Hungate's original model (22), the present model (Fig.…”

“…This inference is based on the moderate suppression of hindgut acetogenesis after R. flavipes termites were fed antibacterial drugs (Fig. 4), as well as the recognized ability of heterotrophic bacterial isolates to produce acetate (and C, and C3 to C5 VFAs) in pure culture (42,43,48) and in two-species cocultures (49). However, it is impossible at this time to ascribe the exact quantitative contribution of protozoa or bacteria to acetogenesis in situ, because the sum of the acetogenic activity of defaunated R.…”

Uric Acid-Degrading Bacteria in Guts of Termites [ Reticulitermes flavipes (Kollar)]

“…We attempted to detect anaerobic metabolism of UA in fresh termite gut contents. Since 60% or more of UA carbon is evolved as C02 by isolates (29), '4CO2 evolution from [2-'4C]UA was used as an estimate of uricolysis by minced guts. Results (Table 4) showed that such preparations degraded a significant amount of UA under strict anaerobic conditions.…”

Caste‐specific N and C isotope ratios in fungus‐growing termites with special reference to uric acid preservation and their nutritional interpretation

“…Many studies have shown that wood‐feeding termites preserve uric acid in the fat body (Potrikus & Breznak, 1980a). The uric acid can be degraded by the gut bacteria through necrophagy or cannibalism and may be recycled as a nitrogen source (Potrikus & Breznak, 1980b,c; Slaytor & Chappell, 1994). Because the food of litter‐ or wood‐feeding termites contains little nitrogen, the conservation of uric acid by these termites appears to be a strategy to overcome nitrogen deficiency (Potrikus & Breznak, 1981), however in fungus‐growing termites, it is hypothesised that the symbiotic fungi serve as a nitrogen‐rich food material, compensating for the scarcity of nitrogen in their forage (Matsumoto, 1976; Collins, 1983).…”