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

Abstract:

Abstract:［Objective］ The purpose of this research is to isolate cold-adapted bacteria producing β-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 β-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 coldadapted bacterial strains isolated，we found 25 stains with β-galactosidase activity，76% of which were Gram-positive bacteria． According to growth temperature range， 80% of strains producing β-galactosidase were identified as psychrophilic bacteria，20% as psychrotrophs． Phylogeneticlly，the β-galactosidase-producing bacterial isolates fell in four groups: subclasses α、β and γ of Proteobacteria，and Firmicutes phylum．［Conclusion］ The results enrich our knowledge on the phylogenetic and physiological diversity of cold-adapted strains producing β-galactosidase in cold environments．