14C-Lignin degradation by three Australian termite species. Isoptera: Mastotermitidae, Rhinotermitidae, Termitidae

The termites Nasutitermes exitiosus (Hill), Coptotermes acinaciformis (Froggatt), and Mastotermes darwiniensis Froggatt were examined for their ability to degrade lignin. Several 14C-(lignin)-lignocelluloses labelled in the 3 side chain position were prepared by infusing plant stems for seven days with the lignin precursor, 14C-cinnamic acid. Based on acid and alkali solubilites, the lignin precursor was more deeply incorporated into the lignin polymer than usually reported for 14C-(lignin)-lignocellulose preparations. N. exitiosus was able to degrade a 14C-(U-ring)-synthetic lignin (5% breakdown) and the lignin component of certain hardwood 14C-(lignin)-lignocelluloses (about 4–6.5% breakdown), but not the lignin component of softwood 14C-(lignin)-lignocellulose. Both C. acinaciformis and M. darwiniensis were less able to degrade any of the 14C-lignins than N. exitiosus. The difference may be due to their possessing different types of gut symbionts. Most of the degradation by N. exitiosus took place during the first week of the 14 day bioassays. Very low amounts (0.03–0.21%) were degraded in the faeces