Open AccessExpression of an alcohol dehydrogenase gene in a heterotrophic bacterium induces carbon dioxide-dependent high-yield growth under oligotrophic conditions
Author(s) -
Shinnosuke Inaba,
Hironori Sakai,
Hiromi Kato,
Takayuki Horiuchi,
Hirokazu Yano,
Yoshiyuki Ohtsubo,
Masashi Tsuda,
Yasunobu Nagata
Publication year - 2020
Publication title -
microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.352
H-Index - 35
eISSN - 1465-2080
pISSN - 1350-0872
DOI - 10.1099/mic.0.000908
Subject(s) - mutant , alcohol dehydrogenase , biology , transposon mutagenesis , gene , transposable element , mutagenesis , escherichia coli , plasmid , biochemistry , phenotype , microbiology and biotechnology , bacteria , genetics , ethanol
Sphingobium japonicum strain UT26, whose γ-hexachlorocyclohexane-degrading ability has been studied in detail, is a typical aerobic and heterotrophic bacterium that needs organic carbon sources for its growth, and cannot grow on a minimal salt agar medium prepared without adding any organic carbon sources. Here, we isolated a mutant of UT26 with the ability to grow to visible state on such an oligotrophic medium from a transposon-induced mutant library. This high-yield growth under oligotrophic conditions (HYGO) phenotype was CO 2 -dependent and accompanied with CO 2 incorporation. In the HYGO mutant, a transposon was inserted just upstream of the putative Zn-dependent alcohol dehydrogenase (ADH) gene ( adhX ) so that the adhX gene was constitutively expressed, probably by the transposon-derived promoter. The adhX -deletion mutant (UT26DAX) harbouring a plasmid carrying the adhX gene under the control of a constitutive promoter exhibited the HYGO phenotype. Moreover, the HYGO mutants spontaneously emerged among the UT26-derived hypermutator strain cells, and adhX was highly expressed in these HYGO mutants, while no HYGO mutant appeared among UT26DAX-derived hypermutator strain cells, indicating the necessity of adhX for the HYGO phenotype. His-tagged AdhX that was expressed in Escherichia coli and purified to homogeneity showed ADH activity towards methanol and other alcohols. Mutagenesis analysis of the adhX gene indicated a correlation between the ADH activity and the HYGO phenotype. These results demonstrated that the constitutive expression of an adhX -encoding protein with ADH activity in UT26 leads to the CO 2 -dependent HYGO phenotype. Identical or nearly identical adhX orthologues were found in other sphingomonad strains, and most of them were located on plasmids, suggesting that the adhX -mediated HYGO phenotype may be an important adaptation strategy to oligotrophic environments among sphingomonads.