Bacterial chitin utilization at halophilic conditions

Chitin is a dominant structural polymer produced in large amounts by brine shrimp Artemia in hypersaline lakes. Microbiological analysis of chitin utilization as a growth substrate in hypersaline chloride-sulfate lakes in the south Kulunda Steppe (Altai, Russia) revealed two groups of bacteria able to grow on chitin at moderate salinity. Under aerobic conditions, an enrichment culture was obtained at 2 M NaCl. Further purification resulted in the isolation of strains HCh1 and strain HCh2, identified as representatives of the genera Saccharospirillum and Arhodomonas (both in the Gammaproteobacteria). The chitin-utilizing potential has not been previously recognized in these genera. The Saccharospirillum sp. strain HCh1 grew on chitin within the salinity range from 0.5 to 3.25 M NaCl (optimum at 1 M), while Arhodomonas sp. strain HCh2 grew up to 2.5 M NaCl but had a higher salt optimum at 1.5 M. Anaerobic enrichments grew with chitin at 2 and 4 M NaCl, but growth in the latter was extremely slow and the culture eventually lost viability. The enrichment at 2 M NaCl resulted in the isolation of strain HCh-An1, identified as a distant new species of the genus Orenia in the clostridial order Halanaerobiales. It was able to grow on chitin within a salinity range from 1.0 to 2.5 M NaCl (optimum at 1.5 M). The strain is proposed as a new species of the genus Orenia-O. chitinitropha.