Xenobiotic breakdown by mixed cultures.

Conclusion The interactions of methanogens with other organisms in natural habitats are various. At a metabolic level methanogens may compete for substrates with other bacteria and are involved in mutualistic interactions with non-methanogenic bacteria. Mutualism between methanogens and protozoa also occurs and, in addition, methanogens interact physically as episymbionts of rumen ciliates. Knowledge of ‘mixed culture’ interactions, in nature and in the laboratory, is relevant to the technological application of methanogenic mixed cultures in anaerobic digestion because metabolic interactions and physical associations of bacteria in films and granules determine the performance of digesters.