A new form of swarming or social motility discovered in an archaeon: what might be the function for this?

[extracellularmatrix]

Hello everyone,

 

I was involved in a recent study where we found a new form of social motility or swarming-like behavior in the archaeal species Haloferax volcanii. If you are not familiar with the idea of swarming in microbes, it is very interesting and something good to know about!

 

We usually think about swarming in insects, or similar behaviors in animals like schools of fish, herds of buffalo, etc.. But microbes undergo similar activities as well. One well known example is the soil species Myxococcus xanthus that is able to prey upon nearby colonies of other bacteria. M. xanthus cells form waves or ripples of cells (like wolf-packs) that travel through and lyse cells of the prey species (there are some good videos of this on YouTube).

 

If you are not familiar with Haloferax volcanii, this is an archaeal species that was first isolated from mud in the Dead Sea in the 1970's. H. volcanii is a halophile, so it lives at high salt concentrations. This is the first time that a collective activity like those seen in M. xanthus (and some other bacteria) has been seen in an archaeon. This is interesting because archaea are more closely related to eukaryotes than they are to bacteria.

 

The best way to look at the behavior is by looking at the time-lapse movies in the paper:

 

http://www.biomedcentral.com/1741-7007/12/65

http://www.biomedcentral.com/content/pdf/s12915-014-0065-5.pdf (direct link to PDF)

 

Though the behavior was observed, we do not yet know if there are any associated functions. Does anyone have any ideas as far as why the cells are coordinating their actions? Maybe it is a type of collective-feeding like in M. xanthus? It seems there is likely a function or ecological role for the swarming behavior, since it is likely an energetically costly activity that involves many genes (controlling chemotaxis, motility, etc.).

[Micro.Pete]

Many pathogenic bacteria have swarming motility (e.g: Bacillus spp., Serratia spp., Salmonella spp., Proteus spp., and many more). In pathogenic context the ability to swarm over surfaces allows bacteria to move, colonize and eventually invade tissues, cells and organs. Because of that, this ability gives those bacteria an advantage over non-swarming species. Thus your hypothesis sounds logical and plausible to me.

 

And here is probably one of the best known swarming bacteria that exist: Proteus mirabilis. Seen here swarming over Chocolate agar.

This culture was obtained from an ear swab.

[CharonY]

The myxobacterial swarming is definitely one of the more specialized and interesting form of swarming. But simply put most data indicate that it is a response to nutrient cues and typically also coordinate via quorum sensing. It is likely that it results in a more cost-effective migration than possible than individual movement, though I am not sure whether someone actually calculated the energy expenditure accurately. There are also other specialized function (at least speculated) which may be relevant in certain host-bacteria interactions.

 

I would be careful withe archaea-eukaryote statement, as to my knowledge this issue is far from being resolved.

[Adriana Reis]

never heard of this before. it is rather interesting. thanks for giving me new insight