Cultivation and characterization of symbiotic bacteria from the gut of Reticulitermes chinensis

Abstract

The complex symbiotic relationship between wood-feeding termites and microorganisms inhabiting their intestinal tracts is a fascinating phenomenon in nature. To understand the physiological functions of symbiotic micro-organisms, bacteria were isolated from the gut homogenate of Reticulitermes chinensis with different media and culture conditions. Under aerobic conditions, 105 bacterial strains were isolated with 1/5 LB medium, 1/3 TSB medium and a modified basal mineral medium, MM-4. Most dominant isolates were bacteria in the genera Bacillus (27.6%) and Lactococcus (21.9%). Under anaerobic conditions, 60 bacterial strains were isolated with 1/5 LB medium, 1/3 TSB medium and a modified Peptone-Yeast medium. The predominant isolates were bacteria in the genus Enterobacter (41.7%) and Citrobacter (33.3%). Many of these bacterial isolates shared high sequence similarity (>98%) in 16S rRNA genes to bacterial clones obtained from the same termite and the other wood-feeding termites or cockroaches. Several bacterial species such as Deinococcus and Gryllotalpicola were isolated from termite gut for the first time. Characterization of these isolates showed that (i) most of Enterobacteriaceae and Lactococcus strains were able to hydrolyze uric acid; and (ii) many of the Bacillus and Streptomyces strains presented endo-β-1,4-glucanase activity. The preliminary results of this work gave us hints of possible functions of symbiotic bacteria in nitrogen recycling and cellulose degradation in the gut of wood-feeding termites