Bacteria get by with a little help from their relatives

Myxobacteria fruiting bodies (Image: Michiel Vos) - Antisocial Behavior in Cooperative Bacteria (or, Why Can't Bacteria Just Get Along?). PLoS Biology Vol. 3/11/2005, e398

Myxobacteria fruiting bodies (Image: Michiel Vos) – Antisocial Behavior in Cooperative Bacteria (or, Why Can’t Bacteria Just Get Along?). PLoS Biology Vol. 3/11/2005, e398

People aren’t the only organism to lend a hand to family members in need – bacteria do it too.

We tend to think of bacteria as individual cells, acting on their own, and for the most part, that’s true. But it turns out that these lone wolves of the single-celled world work together in surprising ways.

New findings from University of Wyoming scientists show that bacteria heal their relatives. Healthy bacteria will exchange part of their good cell membrane for part of an injured relative’s membrane. “It is analogous to how a wound in your body can be healed,” explains senior researcher, Dr. Daniel Wall. “When your body is wounded, your cells can coordinate their functions to heal the damaged tissue,”

This unexpected cooperative bacteria behavior has implications for your health and evolution.

Wall and his coauthors discovered membrane-sharing behavior in soil dwelling bacteria called. Myxobacteria.

Life can be rough in the soil, and Myxobacteria are continually assaulted by biological and chemical stress. Things like extreme pH, being attacked by other microbes, and harsh chemicals in the soil can all harm bacterial membranes. By exchanging portions of membrane, individuals are able to keep up the health of their kin.

Myxobacteria won’t share membranes with just any cell – they like to keep it in the family and only heal closely related individuals. Proteins on the surface of bacteria act as ID tags for passing bacteria to check relatedness before lending a hand. By checking for ID first, bacteria are sure to only help out others that share a lot of their genes. This means that helping out isn’t purely altruistic – the healthy bacteria is benefiting its own genes that are housed in a damaged relative’s cell.

Healing relatives also includes an important implication for your health. The researchers found that dreaded antibiotic resistance could be transferred to a non-resistant strain. “This works by the cells transferring their … armor,” Wall explains. “The human skin protects the body and internal cells from environmental stresses. By analogy, bacteria protect themselves with their [cell membrane], and they are known to change their armor in response to stress. When they chemically change their armor, they can also change their antibiotic resistance profile.”

Because new antibiotic resistant strains of bacteria pop up frequently – from staph infections to gonorrhea – understanding resistance has never been so important. Although Myxobacteria do not infect humans, studying how they transfer resistance between individuals gives insight into how it can work in infectious species. Figuring out how bacteria become antibiotic resistant brings us one step closer to stopping it.

In addition to implications for your health, myxobacteria help our understanding of how multicellular organisms, like us, evolved. The evolutionary change from single cells, like bacteria, to many-celled critters requires cooperation. Scientists have long studied how to get individual cells to work together and these bacteria give a great hint. Myxobacteria sharing membranes to improve the group’s overall health provides a clear example of a shift in focus from the one to the many.

By improving the health of the weakest relatives of the bacteria community, the researchers discovered that the whole group’s health improves. Individual cells cooperatively hunt in swarms and form multicellular protective structures when food is scarce. When myxobacteria encounter a low nutrition environment they band together to create blobby structures called fruiting bodies. The top of the fruiting body produces hardy spores that are released into food-depleted environments. When conditions improve spores grow into new bacteria, ready to hunt again.

Groups of damaged cells cannot form spore-producing fruiting bodies. When damaged cells mix with healthy cells the group is able to make those critical structures, Wall and associates found. Additionally, groups that included damaged cells were sometimes better at forming multicellular fruiting bodies than healthy cells alone.

“Myxobacteria are unusual for bacteria in that they have a true multicellular life,” Wall says. “Researchers are interested in how the evolutionary transition occurred toward multi-cellularity; that is, how cooperation develops and single cells are not just interested in themselves.” Wall goes on to say that membrane sharing ushers myxobacteria from “single cellular life to a more harmonious multicellular life.”

Wall, Vassallo and colleague’s work, entitled “Cell Rejuvenation and Social Behaviors Promoted by LPS Exchange in Myxobacteria” was published May 18th in the online issue of the prestigious Proceedings of the National Academy of Sciences.

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