A new model for the penetration of prey cells by bdellovibrios

Bdellovibrio bacteriovorus 109J and most other bdellovibrios cause prey cells to round following penetration. Bdellovibrio sp. strain W does not cause rounding of the prey. Analysis of enzyme activities during the early stages of bdellovibrio attack indicated that strain W differs from most other bdellovibrios in that there is no glycanase activity produced during penetration. Likewise, heat-killed prey were penetrated normally by strain 109J, but the resulting bdelloplast did not become round and no glycanase was detected, indicating that glycanase is not essential for penetration. Peptidoglycan from prey cells penetrated by strain W was sensitive to lysozyme, but these cells were not susceptible to attack and penetration by strain 109J, indicating that peptidoglycan deacetylation is not the primary exclusion mechanism. We propose a model in which it is the peptidase activity of the bdellovibrios which allows them to breach the peptidoglycan of their prey and in which the glycanase activity exhibited by strain 109J and other bdellovibrios is responsible for the rounding of the bdelloplast.