Surfaces are important in the establishment of microbial communities. For example, water and ions can adhere to the surface of soil particles, creating a nutrient rich microenvironment. Microbes establish themselves in microenvironments, forming communities called biofilms. Biofilms form almost anywhere there is a surface and some water. For instance, you grow your own biofilm on your teeth every night! Biofilms form when certain types of bacteria settle on surfaces and begin to produce sticky polysaccharides. Development continues as other microbes colonize the surface or become trapped in the polysaccharide, establishing the biofilm community. Microbes that live in biofilms are protected from drying out and from antimicrobials. This can make organisms that live in biofilms difficult to kill which is why they cause a wide variety of infections. In the lungs of a cystic fibrosis patient, Pseudomonas aeruginosa forms a biofilm community that is resistant to antibiotics. Biofilms also play a role in urinary tract infections, middle ear infections, and forms on catheters. In hospital settings, biofilm communities can be difficult to remove from ventilation systems and other moist areas. However, new research on the genus Bdellovibrio may lead to medical breakthroughs.
Bdellovibrio is known as a vampire in the bacterial world because they attack, destroy, and insert themselves into their gram-negative prey. It is aerobic, has curved rods, and is propelled by single flagella. Bdellovibrio has a complex life cycle, but only require one to three hours for completion. The bacterium swims rapidly about 100 cell lengths per second until it collides with its prey. It attaches to the bacterium’s surface and begins to rotate at great speed to create a hole in the host cell wall. Bdellovibrio enters leaving its flagella behind. After entry, Bdellovibrio grows between the cell wall and plasma membrane. The host bacterium forms a circular shape called a bdelloplast. Bdellovibrio elongates as it digests the host’s cytoplasm. The host cell is lysed and motile Bdellovibrio that were reproduced are released.
Carey Lambert and Andy Fenton, from the University of Nottingham, UK, who conducted this research found that Bdellovibrio can switch “engines” and crawl at 20 cell lengths. This allows “Bdellovibrio to exit from a bacterial prey cell which it has finished digesting and crawl across a solid surface to find other bacterial prey to invade.” They predict in environments with too little liquid that Bdellovibrio could be used to kill pathogenic bacteria on solid surfaces. Also, Myxobacteria have been identified to have similar slow engines like Bdellovibrio which could lead to medical advances. Myxobacteria are also gram-negative, aerobic cells and they glide along solid surfaces, feeding and leaving a slime trail. Most are predators of other microbes. A mass of myxobacteria can digest their prey more easily because they produce more enzymes than an individual cell. They secrete lytic enzymes and antibiotics to kill their prey. However, unlike Bdellovibrio they can grow in absence of prey. In conclusion, Bdellovibrio has an ability to attack and remove surface-attached bacteria or biofilms. It is hoped that Bdellovibrio species in slow motion can prey on or “mop up” bacteria in biofilms. These predators could reduce the bacterial population and change the structure of the biofilm community.
American Society for Microbiology (2011, June 20) Could bacterial predator be harnessed to mop up biofilms? ScienceDaily. Retrieved June 25, 2011, from http://www.sciencedaily.com/releases/2011/06/110617184857.htm
Fester, R. (2011). E-z microbiology. NY: Barrons Educational Series Inc.
Nunez, M.E. Biophysics of bacterial biofilms [Web log message]. Retrieved from http://www.mtholyoke.edu/~menunez/ResearchPage/AFM.html