Isolation, Genome Sequencing and Proteomic Analysis of a LiCl-Tolerant Bacillus rugosus E-4 Strain from East Taijinar Salt Lake on the Qinghai-Tibet Plateau.

Salt lake is the important source for lithium-tolerant microorganisms. Strain E-4 isolated from East Taijinar salt lake which located in the Qinghai-Tibet Plateau and exhibited LiCl tolerance to 2 mol/L. It was identified to Bacillus rugosus by 16 S rRNA gene sequence and complete genomic sequence. Its genome contained one chromosome and one plasmid, with a sequence size of 4,083,056 bp and G + C content of 43.93%. A total of 3956 coding genes, 27 rRNAs and 87 tRNAs were predicted. There were a large number of genes encoding Na(+)/H(+) antiporters, Ktr/TrK system potassium uptake, compatible solutes synthesis, ABC transporters, general stress proteins and chaperone proteins in the genome. In order to understand the mechanisms in LiCl tolerance, E-4 was analyzed by label-free proteomic method through comparing differentially expressed proteins (DEPs) incubated with no LiCl and 1 mol/L LiCl. 875 DEPs were identified and a total of 401 up-regulated DEPs were found in 1 mol/L LiCl Group, including synthesis and transport of compatible solutes, general stress protein and chaperone protein. Meanwhile, the 475 DEPs related to polyketide synthase, iron complex transport system substrate-binding protein, flagellar protein, and ribosomal proteins were down-regulated. These findings provide insights into the LiCl-resistance mechanism in Bacillus rugosus E-4.