Benzoic acid-degrading bacteria from the intestinal tract of Macrotermes michaelseni Sjöstedt

The intestinal tracts of termites host a wide variety of microbial symbionts, which have been implicated in degradative processes. In this study, a fungus-cultivating termite, Macrotermes michaelseni was found to harbor 2.2 × 10⁶ bacterial cells per ml of gut homogenates capable of degrading benzoic acid. Two benzoic acid degrading bacteria were isolated from the highest dilution of gut homogenates in oxic media with benzoic acid as the sole carbon source. Isolate CBC was related to Stenotrophomonas maltophilo LMG 958^T, Xanthomonas campestris DSM 3586^T and Stenotrophomonas acidaminophila DSM 13117^T with a sequence similarity of 98.3%, 94.7% and 94.2%, respectively. Isolate CBW was related to Enterobacter aerogenes JCM 1235^T and Raoultella ornithinolytica ATCC 31898^T with sequence similarity of 98.4% and 97.8%, respectively. In addition to growing on benzoic acid (up to 9 mM) aerobically, isolate CBW also degraded benzoic acid under anoxic conditions with nitrate as electron acceptor. Isolate CBC did not degrade bezoic acid with nitrate but could degraded resorcinol under oxic conditions.