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

Abstract

CROTHERS, S. F., and J. ROBINSON. 1971. Changes in the permeability of Esclrericlria coli during parasitization by Bdellovibrio bacteriovorrrs. Can. J. Microbiol. 17: 689-697. Bdellovibrio bacteriovorlrs strain 6-54 comp!eted 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 CaC12.2H20. Growth of this strain of B. bacteriovor~rs was optimal over the range of pH 7.5-8.5. N o 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 Mgz+.Growth and multiplication of B. hncteriovor~rs in a two-membered culture were assessed by various parameters, including decrease in absorbance at 520 mp and release of materials absorbing at 260 mp and at 280 mp. The onset of lysis of the host cell was accompanied by an increase in the release of materials absorbing at 260 mp and at 280 mp. The ratio of the absorbance of these materials at 280 and 260 mp increased at the same time, from which it may be inferred that probably amino acids or proteins were being released.No a-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-a-D-galactoside, and to the fluorescent dye 8-anilino-I-naphthalenes:~lfonic acid.

Effect of paracrystalline protein surface layers on predation by Bdellovibrio bacteriovorus

“…Aquaspirillum spp. and B. bacteriovorus 6-5-S were set up in HEPES plus Ca2' as described by Crothers 3,000 x g for 10 min, and the supernatant was then added to an equal volume of pregrown C. crescentus CB2A in PYE. The enrichment was incubated for 48 h with shaking at 30°C and centrifuged at 7,000 x g for 15 min, and the supernatant was then filtered through a series of 0.45-,um-pore-size membrane filters (Millipore Corp.).…”

“…Specimens were examined with a Philips EM300 electron microscope, operating at 60 kV. RESULTS B. bacteriovorus strains 6-5-S and 109J can multiply in the presence of viable but nonproliferating prey cells suspended in buffer supplemented with calcium and/or magnesium (3,5). This experimental medium is very useful for studies on intraperiplasmic growth, since the metabolic activities of the prey cell are minimal (22).…”

Intracellular growth of Bdellovibrio bacteriovorus 6-5-S in heat-killed Spirillum serpens VHL

“…Cultures of S. serpetrs and B. bncreriovorus were maintained by the procedures already described (4). Stock cultures of B. bacreriovorlrs were stored at -70C (Revco freezer) in a yeast -peptone -sodium acetate -cysteine (YPSC) medium (4).…”

The Search for Hunters: Culture-Dependent and -Independent Methods for Analysis of Bdellovibrio and Like Organisms

“…The suspending medium provides a weak buffering environment with cations required for predation. In early studies (Crothers and Robinson 1971) 25-mM HEPES buffer, pH 7.8 with 2 mM CaCl 2 · 2H 2 O was used for cocultures of B. bacteriovorus strain 6-5-S growing on E. coli ML35. Our lab uses HM buffer with 3 mM HEPES, pH 7.6 containing 1 mM CaCl 2 and 0.1 mM MgCl 2 (Flannagan et al 2004), but both options are valid.…”

“…Calcium is required for efficient predation in buffer systems, as it probably functions to facilitate attachment between two negatively charged surfaces. Magnesium has also been included in some buffer compositions for cocultures, but magnesium alone (without calcium) did not support efficient growth of B. bacteriovorus strain 6-5-S (Crothers and Robinson 1971).…”