Summary: The chitinolytic properties of a facultatively anaerobic bacterium isolated from the hindgut of plaice were compared with those of sp. strain 9.1, a bacterium isolated from anoxic estuarine sediment. The chitinolytic enzyme systems of the gut isolate and strain 9.1 both released -diacetylchitobiose (NAG) as the major hydrolysis end-product. During the hydrolysis of chitin, there was transient accumulation of a non-sedimentary chitin fraction which was not detectable by high-performance liquid chromatography. Growth on NAG repressed chitinase synthesis in the gut isolate but not in the species. Thiol reagents were strongly inhibitory to the chitinase of the strict anaerobe but did not affect the hydrolytic enzymes of the gut isolate. When the two bacteria were cocultured with chitin as the sole carbon and energy source, sp. strain 9.1 was always outcompeted. Experiments with batch and phauxostat cultures showed that the competitiveness of strain 9.1 could be improved dramatically by the inclusion in the cocultures of a non-chitinolytic bacterium capable of fermenting chitin oligomers. The cooperation between the oligomer-fermenting species and the sp. is discussed in relation to the regulation of chitinolytic activity in the latter organism.


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