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Living antibiotics – bacteria that suck the life out of their prey

The views expressed are those of the author and are not necessarily those of Scientific American.

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Bacteria will eat anything. Their highly diverse biochemistry, and ability to adapt quickly to change means that they can adapt to take up nutrients from a range of sources, including hot acid lakes and the interior of underground thermal vents. However bacteria also predate each other, and one particular bug, Micavibrio aeruginosavorus does this by latching onto a fellow bacteria and sucking the life out of it.

There are a range of different types of predatory bacteria, and I discussed a few of them in my old blog in the post ‘Bacterial Hunting Strategies‘. While that post examined bacteria that hunt down their prey like wolf-packs, and the little Bdellovibrio that curls up inside a bacteria and devours it from the inside, the Micavibrio was a new one for me. It differs from other bacterial predators as rather than getting inside the cell, or killing it and then eating the remains, it simply hangs onto the slowly dying cell and sucks the life out of it, dividing around it’s prey until the prey finally dies. Like a very determined and slightly horrific leech.

A leech

This was the nicest picture of a leech I could find. By Shizhao from wikimedia commons

The Micavibrio life cycle therefore consists of two main stages. First the attack stage, where the bacteria must seek out its prey. Micavibrio were originally thought to be very fussy about which particular bacteria they feed off, but some have been found that are less specific about their prey. The specificity is very exciting from an antimicrobial point of view, as anything that targets a dangerous bacteria while not affecting the non-dangerous bacteria that live within our bodies has therapeutic potential. Particularly interesting is that the Micavibrio are not put off by biofilms; the sticky layer that bacteria such as Pseudomonas aeruginosa tend to coat themselves in. Antibiotics have real difficulties with biofilms, but the Micavibrio can swim right through them.

Examining the genome of the Micavibrio yields exciting answers as to how it functions as a leeching parasite. Despite relying exclusively upon other bacteria for survival, it has an impressive collection of metabolic enzymes, with very little of the genomic loss seen in other parasitic bacteria. It is, however, missing several genes required to make amino-acids (the building blocks of proteins) which explains its dependance on bacterial-prey. While the Micavibrio seems more than happy to produce its own energy, in order to grow, reproduce, or make any new proteins, it needs a bacterial host. The Micavibrio is also incapable of taking up amino-acids from the environment. You can grow it in a media containing all the amino-acids it needs and it will still die because it can’t transport them into the cell. It needs to be attached to another bacteria to survive. Quite how it gets the amino-acids out of its prey is as yet unknown, although cytoplasmic bridges and intracellular nanotubes have been proposed.

micovibrio aeruginosavorus

The micovibrio (in yellow) attached to its prey (in purple). Picture from the University of Virginia press release (link below)

While this is fascinating from a microbiological perspective, the synthetic biologist inside me is already asking whether this specific bacteria-killing machine could be of any medical use. Using bacteria to kill bacteria is an interesting idea, although the Micavibrio would have to be fitted with a death gene to dispose of it once the disease bacteria were removed. The problem with a death gene is simply that it is highly evolutionarily disfavored. Any bacteria that manage to loose the death gene will be at a massive advantage and would quickly spread.

However while the living antibiotics might not be immediately applicable in medical scenarios, there are plenty of industrial situations that could benefit from the specificity and hunting ability of the Micavibrio. Biofilms form in pipes, and block up nozzles in equipment, and as using antibiotics tends to leave behind small parts of the biofilm (which has an increased likelihood of being resistant) using the search-and-destroy feature of Micavibrio could be really useful. It could also (with some genetic tweaking) play a part removing contaminating bacteria from fermenting solutions, without requiring the need for antibiotic treatments.

University of Virginia Press Release

Wang Z, Kadouri DE, & Wu M (2011). Genomic insights into an obligate epibiotic bacterial predator: Micavibrio aeruginosavorus ARL-13. BMC genomics, 12 PMID: 21936919

S.E. Gould About the Author: A biochemist with a love of microbiology, the Lab Rat enjoys exploring, reading about and writing about bacteria. Having finally managed to tear herself away from university, she now works for a small company in Cambridge where she turns data into manageable words and awesome graphs. Follow on Twitter @labratting.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. EyesWideOpen 9:00 pm 11/10/2011

    Sounds like the perfect sleeper from bio-terrorism to military bio-warfare weapons of mass destruction. Of course like nuclear energy and every other advancement in science, this bio-technology has the capacity for great good or unspeakable evil.

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  2. 2. S.E. Gould in reply to S.E. Gould 5:07 am 11/11/2011

    Thanks for the comment! I’m not sure how many military applications a bacteria-eating-bacteria would have, but it’s certainly true that synthetic biology is a field that needs careful monitoring to prevent potential misuse. It certainly is something that the scientists within the field are well aware of – there are numerous conferences and organising bodies set up to discuss the best way to prevent such threats.

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  3. 3. Quinn the Eskimo 2:18 am 11/14/2011

    Everything in the Lab escapes. Synthetic Life cannot be stopped. Once created, as Hollywood said, Life finds a way.

    Everything in the Lab escapes.


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  4. 4. S.E. Gould in reply to S.E. Gould 6:30 am 11/15/2011

    Most bacteria worked on in the lab wouldn’t survive outside of a lab environment, and those that can are kept under tight containment measures. There is always a risk, but efforts are taken to minimise it as far as possible.

    Technically there’s always a risk that the missile-targeting Doomsday machine will malfunction, or a meteorite will hit the earth, or a novel deadly viral strain will evolve outside of the lab completely. All risk is relative.

    ” Synthetic Life cannot be stopped” – I wish someone had told my experiments that! One of the biggest problems in researching Synthetic biology isn’t cells surviving, it’s that they have a horrible tendency to die, and refuse to grow with your genome in them.

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  5. 5. MolBioPhys 4:44 pm 11/17/2011

    You go girl!

    I have been suffering from Lyme Disease for too long that it seems it cannot be killed at this point – it hides, it creates bio-films, it curls up into a tight ball (cyst) and it even changes its outer coating to fool the immune system and the antibiotics.

    I hope that you can take this idea to the next level! I remember a while ago that there was a Russian team working on virus-killing bacteria but stopped for lack of funding or something.

    Now, here are bacteria-killing bacteria. Brilliant! Please please please keep working on this.

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  6. 6. S.E. Gould in reply to S.E. Gould 11:42 am 11/18/2011

    Thanks for the comment! This is not an area I am working on (I communicate the research rather than doing it) but it looks like a fascinating area to be involved in. There are a lot of people looking into much-needed alternatives for antibiotics and there are some interesting ideas starting to get into the clinical trials pipeline.

    The virus-killing bacteria you speak of are called bacteriophages. A fair amount of work was done on them in Russia, and it’s started to spread over into other areas as well. Funding is still hard to come by, but I do know labs that are working on this ‘phage-therapy’. Bacteriophages will probably never replace antibiotics, but they could certainly prove very useful to help antibiotics be more effective, or boost the effectiveness of antibiotics which bacteria are resistance to.

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