Altered Mercury Transport in a Mutant of Pseudomonas fluorescens B69

We describe a mutant derivative of P. fluorescens B69 which can grow in elevated concentrations of mercurials after elimination of the mercury-resistance plasmid harboured by the parental strain

T. Barkay


Scholarcy highlights

  • The ‘classic’ mercury resistance mechanism in bacteria is the inducible reduction of ionic mercuryto the volatile elemental form, which leaves the growth medium due to its high vapour pressure, allowing commencement of bacterial growth
  • Pseudomonas fluorescens B69A is a mercury-hypersensitive strain, obtained when the mercury-resistant strain B69 is cured of a 34 MDal plasmid
  • The conjugal transfer of mercury resistance from P.JEu0rescen.sB69 to its isogenic strain B69A confirms the identification of the 34 MDal plasmid as a mercury-resistance plasmid
  • No other resistance to antibacterial agents was co-transferred with mercury resistance to the recipient strains, indicating no genetic linkage between this trait and the resistances observed for P.JEwrescens B69
  • Mutants able to grow in the presence of an elevated concentration of mercury were selected when the hypersensitive strain B69A was exposed to 10 pg Hg ml-I
  • Hypersensitivity to mercury is attributed to an active merTgene in the absence of a functioning mercuric reductase gene gene;Summers 8z .If resistance in strain B69 resulted from a similar phenomenon, a functioning merT gene should be present in strain B69A, implying that either merT is not carried on the 34 MDal plasmid, or that an additional merT gene is part of P. fluorescens B69 genome
  • The only possible explanation for the decrease in the rate of mercury volatilization must lie in a reduced transport of this heavy metal from the growth medium to the cytoplasmic mercuric reductase

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