Use of E. coli reporter genes to monitor predatory activity by Bdellovibrio bacteriovorus.

Abstract

The predatory bacterium, Bdellovibrio bacteriovorus, breaks down host proteins as part of the infection process. Two reporter proteins, green fluorescence protein (gfp) and luciferase (lux) were used as monitors of predatory activity by Bdellovibrio. Plasmids encoding these reporter proteins (pGLO1 and pJE202, respectively) were introduced into ML35 (a strain of E. coli preferred by Bdellovibrio) by electroporation. Loss of fluorescence by prey cells containing pGLO1 was monitored by long wave UV light. Loss of luminescence by prey cells containing pJE202 was monitored by scintillation counting in chemiluminescence mode. Testing host independent (109J-KA1 and 109J-HI) and host-dependent (109J) strains of Bdellovibrio with these reporter proteins suggest that host independent strains are not quickly breaking down cellular host proteins (unlike the host-dependent strain). In addition, it was found that prey cells containing pJE202, when attacked by 109J, displayed increased light production early in infection. This may be due to release of cofactors utilized by luciferase during predation, while full inactivation of luciferase takes more time.