Thread: Multicellular prokaryotes

Apparently there are multicellular prokaryotes. While some prokaryotes go through a multicellular stage, such as the myxobacteria, there are a few species among the magnetotactic bacteria that are described as being "obligatorily multicellular". The "organism" is multicellular at all stages in its life cycle. It forms a hollow sphere of cells reminiscent of the algae Volvox and consists of a functiionally coordinated cell layer, the cells of which undergoe synchronous division. The organism itself reproduces by undergoing binary fission. Apparently no single, free-living cells have been found. A prokaryotic organism?



Merry Youle "Everyone Rowing in the Same Direction"
Small Things Considered - The Microbe Blog
20 May 2010

Keim CN et al (2004)
Multicellular life cycle of magnetotactic prokaryotes
FEMS Microbiol Lett. 2004 Nov 15;240(2):203-8

Abreu F, Silva KT, Martins JL, Lins U (2006)
Cell viability in magnetotactic multicellular prokaryotes
International Microbiology (PDF)


Had it been April, I would have thought this was a clever joke.

Thoughts?

Implications for the evolution of multicellular life? Or dead-end oddball?

Multicellularity likely evolved separately a few times. Plants, fungi, and animals likely all have separate origins of multicellularity.

It's questionable whether the coordinated taxis of these bacteria really counts as multicellular life. I am confident in saying that they probably aren't related to the first multicellular ancestors of animals and plants. Things like quorum sensing in myxobacteria can create rudimentary coordinated behavior, this can probably give us insight into what early forms of multicellular life were like.

Yeah, they clearly aren't ancestral to the metazoa. Although such a lifestyle itself could perhaps have been a stepping stone.

It was a little more than a coordinated taxis. It is the obligate nature of the colony that is interesting. Members of a colony are capable of free-living, while these individual cells are not. Which begs the question, is it just another example of one of biology's many exceptions to s rule, or is it actually an organism? Finding free-living cells would obviously clear the issue up, but so far that's not happened.

Bacteria are usually found in communities. Even multicellular eukaryotes like us depend on these bacterial communities.

The community is a certain type of organization. Cross species even. Does that make it multicellular? Well, a single bacterium doesn't do as well as a community for many species of bacteria. Some co-dependence is present.

Within a multicellular organism this co-dependence is defined by the origin of the tissue. It all arose from the same cell. And on top of that there is the co-dependence communities with other species.

I often think that people who are fond of strict inflexible definitions have no business in biology. Ironically the strict inflexible definition is the starting point for all biological work. Hence you have a great future in biology if you are fond of the strict inflexible definition, with the note that this should be accompagnied with the ability of lateral thinking and great willingness to abandon inflexibility.

Hence we need great flexible inflexibility when considering biological concepts.

bla bla.