Isolation, Identification Of Salt Tolerant Petroleum-Degrading Bacterium And Degradation Characteristics

Two salt-tolerant diesel-degrading bacteria are named LS1and LS4, which couldutilize diesel as sole source of carbon and was isolated from oil-contaminated soil near oilfield in jiangsu province. On the basis of morphology, biochemical and physiologicalcharacteristics and16S rDNA sequence analysis, strain LS1was identified to bepseudomonas sp. and LS4was identified to be Chryseobacterium, they were all gramnegative bacteria; Recearch on effects of different environment and the growthcharacteristics and the diesel degradation effect of carbon source on the strain. Strain LS1could tolerate NaCl up to6%~8%and degrade diesel of12000mg·L-1. The ranges ofsuitable pH and temperature for growth of strain LS1were6.0-8.0and28℃-36℃,respectively. Under the conditions of salinity6%,pH7.0,temperature32℃,the dosage10%,degradation rate of diesel was up to78.3%with initial concentration of3000mg·L-1.Additional glucose or sucrose accelerated the degradation rate from78.3%to90.5%and92.1%, respectively. Strain LS4could tolerate NaCl up to6%and degrade diesel of11000mg·L-1. The ranges of suitable pH and temperature for growth of strain LS4are6.0~8.0and28~36℃, respectively. Under the conditions of salinity6%,pH7.0,temperature32℃,thedosage8%,degradation rate of diesel was up to61.4%with initial concentration of2000mg·L-1. Additional glucose or sucrose accelerated the degradation rate from61.4%to78.5%and81.1%, respectively. Heavy metals for LS1and LS4, had strong inhibition effect ofgrowth. Among them, the strongest inhibition effect was Hg2+, the minimum inhibitioneffect was Mn2+.The results of research on alkane hydroxylase partial gene of strains show，stain LS1alkane hydroxylase gene is708bp long and Acinetobacter junii strain part of the homologyof amino acids sequence reached99%, that of alkane hydroxylase gene was up to homologyin amino acids close level; The alkane hydroxylase partial gene of strain LS4and hemolyticstrains of Acinetobacter strains were high similarity, the highest similarity reached98%.They had the common origin of alkane hydroxylase gene, but in order to adapt to thedifferent environment, formation and evolution of alkane hydroxylase gene was differentexpression sequence in evolution.The study of strains LS1and LS4of salt tolerant mechanism was discussed, theresults shows that the salt-tolerance of strains were possible due to the accumulation of betaine in the cell, which regulated the osmotic pressure balance of cell. Additional betainecould enhance diesel degrading by strain in the presence of high salinity.