Expression of an alcohol dehydrogenase gene in a heterotrophic bacterium induces carbon dioxide-dependent high-yield growth under oligotrophic conditions

Shinnosuke Inaba, Hironori Sakai, Hiromi Kato, Takayuki Horiuchi, Hirokazu Yano, Yoshiyuki Ohtsubo, Masataka Tsuda, Yuji Nagata

Research output: Contribution to journalArticle

Abstract

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 oligo-trophic conditions (HYGO) phenotype was CO2-dependent and accompanied with CO2 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 CO2-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.

Original languageEnglish
Article number000908
Pages (from-to)531-545
Number of pages15
JournalMicrobiology (United Kingdom)
Volume166
Issue number6
DOIs
Publication statusPublished - 2020

Keywords

  • Alcohol dehydrogenase
  • CO fixation
  • Poligotroph
  • Sphingomonads

ASJC Scopus subject areas

  • Microbiology

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