ISOLATION AND CHARACTERIZATION OF TN5-INDUCED MUTANTS OF PSEUDOMONAS-PAUCIMOBILIS UT26 DEFECTIVE IN GAMMA-HEXACHLOROCYCLOHEXANE DEHYDROCHLORINASE (LINA)

Pseudomonas paucimobilis UT26 grows on gamma-hexachlorocyclohexane (ga mma-HCH) as a sole source of carbon and energy. Tn5 mutation was intro duced into UT26, and two kinds of mutants defective in gamma-HCH degra dation were phenotypically isolated; one (UT64) completely lacked the activity to degrade gamma-HCH, while the other (UT61) retained a very low level of activity. Tagging and sequencing analysis showed that bot h mutants had a Tn5 insertion at the same site of the linA (gamma-HCH dehydrochlorinase encoding) gene. However, UT61 had an additional rear rangement, which could be the cause of its retaining a low level of ac tivity. An in vitro complementation test with a crude extract from UT6 4 plus partially purified LinA protein showed that LinA was essential not only for the first-step reaction (gamma-HCH to gamma-pentachlorocy clohexene; gamma-PCCH), but also for the second-step reaction (gamma-P CCH to compound B) of gamma-HCH degradation in UT26.