title: [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].
abstract: 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.
  
  
  CONCLUSIONS
  The results enrich our knowledge on the phylogenetic and physiological diversity of cold-adapted strains producing beta-galactosidase in cold environments.
authors.affiliation: School of Food Sciences, Shihezi University, Shihezi 832000, China. shzuzm2009@163.com
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.forename: Yanling
authors.initials: Y
authors.lastname: Gu
authors.forename: Yuli
authors.initials: Y
authors.lastname: Xu
authors.forename: Xuewei
authors.initials: X
authors.lastname: Shi
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Zheng
authors.forename: Hong
authors.initials: H
authors.lastname: Zhou
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Ni
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D044822:Biodiversity; D002681:China; D003080:Cold Temperature; D014644:Genetic Variation; D019015:Geologic Sediments / Q000382:microbiology*; D046448:Ice Cover / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001616:beta-Galactosidase