Protonophore-resistance and cytochrome expression in mutant strains of the facultative alkaliphile Bacillus firmus OF4

Philip G. Quirk, Arthur A. Guffanti, Robert J. Plass, Sanda Clejan, Terry Ann Krulwich

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27 Scopus citations

Abstract

Two protonophore-resistant mutants, designated strains CC1 and CC2, of the facultative alkaliphile Bacillus firmus OF4 811M were isolated. The ability of carbonyl cyanide m-chlorophenylhydrazone (CCCP) to collapse the protonmotive force (Δ over(μ, -)H+) was unimpaired in both mutants. Both resistant strains possessed elevated respiratory rates when grown at pH 7.5, in either the presence or absence of CCCP. Membrane cytochromes were also elevated: cytochrome o in particular in strain CC1, and cytochromes aa3, b, c and o in strain CC2. Strain CC2 also maintained a higher Δ over(μ, -)H+ than the others when grown in the absence of CCCP. When grown in the presence of low concentrations of CCCP, strains CC1 and CC2 both maintained higher values of Δ over(μ, -)H+ than the wild-type parent and correspondingly higher capacities for ATP synthesis. In large-scale batch culture at pH 10.5, both mutant strains grew more slowly than the parent and contained significantly reduced levels of cytochrome o. Cells of strain CC1 also displayed a markedly altered membrane lipid composition when grown at pH 10.5. Unlike previously characterized protonophore-resistant strains of B. subtilis and B. megaterium, neither B. firmus mutant possessed any ability above that of the parent strain to synthesize ATP at given suboptimal values of Δ over(μ, -)H+. Instead, both resistant alkaliphile strains maintained a higher Δ over(μ, -)H+ and a correspondingly higher ΔGp than the parent strain when growing in sublethal concentrations of CCCP, apparently as a result of mutational changes affecting respiratory chain composition. Also of note in both the mutant and the wild-type strains was a marked elevation in the level of one of the multiple terminal oxidases, an aa3-type cytochrome, during growth at pH 7.5 in the presence of CCCP or during growth at pH 10.5, i.e. two conditions that reduce the bulk Δ over(μ, -)H+.

Original languageEnglish
Pages (from-to)131-140
Number of pages10
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1058
Issue number2
DOIs
StatePublished - 17 Jun 1991
Externally publishedYes

Keywords

  • (B. firmus OF4)
  • Alkaliphile
  • Cytochrome regulation
  • Membrane lipid
  • Protonmotive force
  • Terminal oxidase
  • Uncoupler resistance

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