Open AccessThe use of mutants to discern the degradation pathway of 3,4′‐dichlorobiphenyl in Pseudomonas acidovorans M3GY
Author(s) -
Mc Cullar Michael V.,
Koh SungCheol,
Focht Dennis D.
Publication year - 2002
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.2002.tb00997.x
Subject(s) - strain (injury) , biology , mutant , pseudomonas , biphenyl , bacteria , enzyme , biochemistry , carbon source , mutation , microbiology and biotechnology , gene , genetics , chemistry , organic chemistry , anatomy
Pseudomonas acidovorans strain M3GY is a recombinant bacterium with the novel ability to utilize 3,4′‐dichlorobiphenyl (3,4′‐DCBP) as a growth substrate. This strain was previously shown to oxidize the 3′‐ring and produce 4‐chlorobenzoate (4‐CBa) through the standard biphenyl pathway. Although 4‐CBa was metabolized through the meta ‐fission pathway, the genes encoding the ortho ‐chlorocatechol pathway were retained. Nevertheless, neither 3‐CBa nor 3‐chlorocatechol (3‐CC) were detected as intermediates during metabolism of 3,4′‐DCBP, nor was 4‐CBa utilized as a sole carbon source, by this strain. Two mutant strains were produced to resolve these anomalies. Mutant strain M3GY–9 was obtained by Tn 5 insertion and selection for growth on biphenyl, and was unable to grow on 3‐CBa. It accumulated 3‐CC from 3,4′‐DCBP when grown on biphenyl. Thus, M3GY attacks both rings, and the failure to isolate 3‐CBa or 3‐CC is due to rapid turnover by the enzymes of the ortho ‐chlorocatechol pathway in the wild‐type strain. Mutant strain M3GY–1 grew on 4‐CBa, unlike the wild‐type strain. Washed cell suspensions of mutant strain MEGY‐1 consumed 4‐fluorobenzoate, 4‐bromobenzoate, and, to a lesser extent 4‐iodobenzoate. The mutation that resulted in the ability of mutant strain M3GY‐I to effectively utilize 4‐CBa as a sole carbon source was associated with a transport mechanism.