A Living Antibiotic, Anyone?
This Bacterium Might Just Be Man's New Best Friend
Why Another Antibiotic?
Gram negative infections are the cause of a range of human infectious diseases, ranging from typhoid (Salmonella typhi), dysentery (Klebsiella, Proteus, E.coli, Granuloma), eye infections (Pseudomonas aeruginosa), respiratory and urinary tract infections (Serratia marcescens), to plague (Yersinia pestis), acidity and stomach cancers (Helicobacter pyroli). Resistance to common antibiotics is fast developing in these species. This is worrisome as the bugs seem to alter themselves and gain resistance to antibiotics much faster than the rate at which we are able to invent newer antibiotics. Newer and stronger antibiotics also seem to have an increasing panel of adverse reactions for humans.
What is Bdellovibrio bacteriovorus?
Quite a mouthful, the name. That apart, this small creature might soon turn out to be man’s best friend. Technically, its just another gram negative bacteria. But its uniqueness lies in the fact that it naturally feeds on our enemies – E.coli, Salmonella, Pseudomonas and a range of pathogenic gram negative bacteria – while having a distaste for mammalian and human cells. The immediate implications of such behaviour are that the bacterium could be used to get rid of infectious gram negative bacteria while sparing host human cells.
How Does It Kill Pathogenic Bacteria?
Bdellovibrio bacteriovorus is a predatory bacterium. It is known to infect prey gram negative bacteria by colliding with them at speeds recorded up to 160 µm/s, or over 100 times their length per second and attaches to the prey cell's outer membrane and creates a pore in it. It then squeezes itself through the pore and ‘re-seals’ it to afford itself a safe and private niche away from the exterior environment. Thereafter, it unleashes its arsenal and starts digesting the prey bacterium's cellular components from the inside out. Simultaneously, it also starts replicating itself. In about 15 minutes, it kills the prey cells and along with the newly replicated progeny, bursts out in search for more prey. Quite gory, indeed, but suits us as long as the prey is a common enemy.
No specific attachment sequence or recognition site is known as of now. This raises the hope of a wide-spectrum activity against multiple prey bacteria. It has also been found to be effective against ‘capsulated’ forms of bacteria, which are known to be more virulent and resistant to other forms of therapy.
Where is Bdellovibrio Found?
The best part is that Bdellovibrio seem to be present almost everywhere. Scientists have isolated them from soil, fresh water samples, human skin, sewage as well as the gut of humans and animals like horses and chicken.
So When Can I Get a ‘Bdellovibrio Therapy’ From My Doctor?
Still some time to go, it seems. Scientists are busy working late hours studying the physiology of this wondrous bacteria. Though its been found to be unable to infect human cells, thorough studies regarding its safety and efficacy need to be done. But the potential of this organism is quite great and if things work out, it might be just the answer to the increasing menace of drug resistance in gram negative bacteria.
Further reading
1. Bdellovibrio as a therapeutic agent, Sockett RE, Lambert C, Nature Reviews Microbiology, 2, 669-644, 2004
2. A predator unmasked : life cycle of Bdellovibrio bacteriovorus from a genomic prespective, Rendulic S, Jagtap P, Rosinus A, Eppinger M, Baar C, Lanz C, Keller H, Lambert C, Evans KJ, Goesmann A, Meyer F, Sockett RE, Schuster SC., Science, 303, 689-692, 2004
3. Predation by Bdellovibrio bacteriovorus HD100 requires type IV pili, Evans KJ, Lambert C, Sockett RE., Journal of Bacteriology, 189, 4850-4859, 2007
4. An inside job : Bdellovibrio bacteriovorus, Liz Sockett, Microbiology Today, 184-187, 2008.
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