Benzene, toluene, ethylbenzene, and xylene (BTEX) are highly water soluble, hence can contaminate a large volume of groundwater and soil, exhibiting a serious negative impact on human health. To get efficient biodegradation and bioremediation of BTEX in the highly salt and pH contaminated sites, this study captured, investigated and identified three novel haloalkaliphilic bacterial strains HA10, HA12 and HA14 belong to genus Pseudomonas that have strong capability to degrade BTEX at 7% NaCl (w/v) and pH 9. Study of enzymes in halophiles will help understanding the mechanism of BTEX degradation in saline and alkaline environments. Three novel catechol 2,3-dioxygenase genes C23O10, C23O12 and C23O14 were amplified, cloned and overexpressed from the three obtained haloalkaliphilic strains HA10, HA12 and HA14 respectively. Phylogenetic tree analysis for the three novel C23Os and their relatives formed a new branch. C23O12 and C23O14 showed activity with only catechol, while the activity was observed in C23O10 on catechol and 2,3-dihydroxybiphenyl. Kinetic properties analysis for C23O10 indicated that its preferred substrates were catechol and 2,3-Dihydroxybiphenyl. C23O10 activity severely affected and rapidly inactivated by 3-Chlorocatechol. This finding may be necessary for developing in-site bioremediation of BTEX contaminated sites in both highly saline and alkaline environments.
Keywords: BTEX; Catechol 2,3-dioxygenase; Haloalkaliphilies.
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