Comments on The Evilutionary Biologist: Quorum Sensing or Diffusion Sensing?

John, thanks for the boost.Rford, there's a nice p...

2007-11-30T18:48:00.000-05:00

John, thanks for the boost.

Rford, there's a nice paper from Ken Bayles lab (Shompole et al. 2003 Mol. Micro. 49: 919-927) showing that single Staph aureus cells use autoinducers to detect that they are in an intracellular endosome and to induce expression of the genes that get them out into the cytoplasm.

Ford, that should be an interesting article. Keep ...

2007-11-30T10:28:00.000-05:00

Ford, that should be an interesting article. Keep me posted on it!

Thanks, Andrew and John. Toby Kiers and I are wor...

2007-11-29T13:58:00.000-05:00

Thanks, Andrew and John. Toby Kiers and I are working on an article for Annual Review of Ecology etc. on the rhizosphere mutualisms. For some microbial activities that happen to benefit plants (and, indirectly, other microbes) it's easy to see potential benefits to individual microbial cells, but quorum-sensing seemed to indicate an important role for kin selection as well. Now we'll have to re-evaluate some of those examples.

Rosie cites this paper as evidence for the hypothe...

2007-11-29T09:35:00.000-05:00

Rosie cites this paper as evidence for the hypothesis that cells can make sufficient enzymes to benefit themselves.
http://tinyurl.com/2oau8r

Full quote from her paper, "For example, in laboratory cultures of the soil bacterium Bacillus subtilis, autoinducers reach inducing concentrations at culture densities <10^8 cells ml-1 [17], implying that each cell can fill a volume of 10^4 μm3 with an activating concentration of inducer."

I'm sure a lit search will turn up further examples.

rford,I am not sure that an enclosed space is a ne...

2007-11-28T20:26:00.000-05:00

rford,

I am not sure that an enclosed space is a necessary condition. The viscosity of aqueous solutions is quite high at micro-scales. Since we are talking about relatively large molecules, it is possible that they might not diffuse away very quickly even in relatively open environments. If I recall my fluid dynamics correctly, diffusion can also be quite low on boundries, such as the surface of particles.

I agree that a key assumption of the hypothesis is that a single cell can make enough enzyme to benefit itself. My question is: why is the default assumption that they can't?

A key assumption of the diffusion hypothesis is th...

2007-11-28T19:00:00.000-05:00

A key assumption of the diffusion hypothesis is that a single cell can make enough extracellular enzyme to benefit itself, i.e. that cells find themselves in small enclosed spaces with limited diffusion fairly often. Has anyone looked at this question quantitatively? Another assumption (probably true) is that it's cheaper to make the quorum/diffusion probe to use the extracellular enzyme itself as the probe.

Even worse. I've made quite a few people read the...

2007-11-28T09:27:00.000-05:00

Even worse. I've made quite a few people read the paper and even having done so, most people seem to almost willfully miss the point that the diffusion sensing hypothesis negates the need to invoke group benefits.

Very frustrating