Changes in the permeability of Escherichia coli during parasitization by Bdellovibrio bacteriovorus

Abstract

Bdellovibrio bacteriovorus strain 6-5-S completed a typical infection cycle when incubated with E. coli ML 35 (lac i−z+y−) in 0.025 M Hepes buffer, pH 7.8, supplemented with 0.002 M CaCl2∙2H2O. Growth of this strain of B. bacteriovorus was optimal over the range of pH 7.5–8.5. No growth occurred at pH 6.5. The broad pH range may occur because a buffer per se is not required for growth and multiplication. The parasite failed to multiply in a two-membered culture unsupplemented with Ca2+ or Mg2+.Growth and multiplication of B. bacteriovorus in a two-membered culture were assessed by various parameters, including decrease in absorbance at 520 mμ, and release of materials absorbing at 260 mμ, and at 280 mμ. The onset of lysis of the host cell was accompanied by an increase in the release of materials absorbing at 260 mμ and at 280 mμ. The ratio of the absorbance of these materials at 280 and 260 mμ increased at the same time, from which it may be inferred that probably amino acids or proteins were being released.No β-galactosidase could be detected in the culture fluid of the two-membered culture. The infected E. coli cells were more permeable than uninfected cells to o-nitrophenyl-β-D-galactoside, and to the fluorescent dye 8-aniIino-1-naphthalenesulfonic acid.