Background: Recently, there has been a renewed interest in the use of biological control agents against biofilms. These agents include the use of invertebrates and protozoa to reduce biofilms by means of grazing and the use of bacteriophages.

In our work we have used bacterium from the genus Bdellovibrio in order to reduce and control biofilms. Bdellovibrio spp. are Gram negative, motile and uniflagellated bacteria. This genera is characterized by predatory behavior (or an obligatory parasitic life cycle). Bdellovibrios attack other Gram-negative cells, penetrate into their periplasm, multiply in the periplasmic space, and finally burst the cell envelope to start the cycle anew.

Pretreated	+ B.b.	-B.b.

FIG. 1. Predation on E. coli biofilms by B. bacteriovorus. E. coli biofilms were developed for 18 hrs in 96 well microtiter plates (pre-treatment), followed by 24 hr exposure to B. bacteriovorus lysate (+ B.b. ) or a sterile lysate solution (- B.b. ), then rinsed and stained with CV. Addition of B. bacteriovorus effectively reduces the E. coli biofilm.

Pretreated	+ B.b.	- B.b .

FIG. 2. Visualizing biofilm predation. Scanning electron micrographs taken after E. coli biofilms were developed for 18 hrs on PVC plastic cover slip (pre-treatment) and exposed for 24 hrs to a sterile lysate solution (- Bdellovibrio ) or B. bacteriovorus lysate (+ Bdellovibrio ). Arrow showing attached B. bacteriovorus. Scale bar 2 m m. Once again, our data show that addition of the predator effectively reduces the bacterial biofilm.

Conclusions

• Our data suggest that growth in a biofilm does not eliminate predation by Bdellovibrio , but allows a level of survival from attack greater than that observed for planktonic cells.
• The methods developed in our lab should allow a more rigorous assessment of the potential use of Bdellovibrio as a biocontrol agent versus biofilms and its use as a tool to improve classical biofilm control strategies.

In recent studies, we have also shown that another bacterial predator, Micavibrio aeruginosavorus, also has the ability to attack biofilms of a wide range of microbes. Daniel Kadouri, a former post-doc in the lab, is continuing these studies in his own lab at UMDNJ. Learn about his lab here.

From more information, please see:

Kadouri, D. and O'Toole G.A. 2005. Susceptibility of biofilms to Bdellovibrio bacteriovorus attack. Appl Environ Microbiol. 71:4044-51.

Kadouri D, Venzon NC, O'Toole GA. 2007. Vulnerability of pathogenic biofilms to Micavibrio aeruginosavorus. Appl Environ Microbiol. 73(2):605-14.