End Products of Anaerobic Chitin Degradation by Salt Marsh Bacteria as Substrates for Dissimilatory Sulfate Reduction and Methanogenesis

Abstract

The anaerobic pathway of chitin decomposition by chitinoclastic bacteria was examined with an emphasis on end product coupling to other salt marsh bacteria. Actively growing chitinoclastic bacterial isolates produced primarily acetate, H 2 , and CO 2 in broth culture. No sulfate-reducing or methanogenic isolates grew on chitin as sole carbon source or produced any measurable degradation products. Mixed cultures of chitin degraders with sulfate reducers resulted in positive sulfide production. Mixed cultures of chitin-degrading isolates with methanogens resulted in the production of CH 4 with reductions in headspace CO 2 and H 2 . The combination of all three metabolic types resulted in the simultaneous production of methane and sulfide, with more methane being produced in mixed cultures containing CO 2 -reducing methanogens and acetoclastic sulfate reducers because of less interspecific H 2 competition.