[Phylogenetic and physiological diversity of cold-adapted bacteria producing beta-galactosidase from permafrost sediments of the bottom layer of the Glacier No. 1 in the Tianshan Mountains].

OBJECTIVE

The purpose of this research is to isolate cold-adapted bacteria producing beta-galactosidase from permafrost sediments of the bottom layer of the Glacier No. 1 in the Tianshan Mountains, China. Physiological test and phylogenetic analysis were undertaken to expand our knowledge on diversity of psycrotrophic and psycrophlic bacteria.

METHODS

By using lactose as the main carbon source and X-Gal as chromogenic agent in the medium, cold-adapted strains producing beta-galactosidase were detected. Taxonomic identity and genetic diversity of strains isolated were determined by spatial 16S rRNA gene sequences and rep-PCR fingerprint. In addition, we analyzed the phonotypic differences between strains showing high similarity of 16S rRNA gene sequences, including the optimum growth temperature, salt tolerance, ability to use carbon source and antibiotic resistance spectra.

RESULTS

Of the total 90 cold-adapted bacterial strains isolated, we found 25 stains with beta-galactosidase activity, 76% of which were Gram-positive bacteria. According to growth temperature range, 80% of strains producing beta-galactosidase were identified as psychrophilic bacteria, 20% as psychrotrophs. Phylogeneticlly, the beta-galactosidase-producing bacterial isolates fell in four groups: subclasses alpha, beta and gamma of Proteobacteria, and Firmicutes phylum.

CONCLUSION

The results enrich our knowledge on the phylogenetic and physiological diversity of cold-adapted strains producing beta-galactosidase in cold environments.