Lenski bacteria & Why the size increase?

[Skepticus]

This is my first post here. I will post an intro soon, but first I would like to ask if anybody has more detail on the Lenski experiments with bacteria. In particular I am interested in the increased size of the bacteria noted in all of the cultures, as apposed to the more famous result re: the metabolic improvement to digest citrate. I haven´t had much luck with googling for it, as I get swamped with this more compelling aspect of the research. I was reading the The Greatest Show On Earth, and Dawkins explained the Lenski research, mentioning the original spurt of size increase. He alluded to there being no clear explanation for this, and a hypothesis immediately came to mind. I would like to know what others think about this size increase, and existing explanations which may have been proposed, then I will put my explanation on the table. Cheers

 

Edit: Ops! I seem to have misspelled Lenski in the title. Can that be changed?

Edited May 19, 2010 by Skepticus
Typo

[Greippi]

Have you read the relevant literature? This paper has a large section titled "cell size and yield", including several hypotheses.

[Skepticus]

Have you read the relevant literature? This paper has a large section titled "cell size and yield", including several .

 

Thanks Greppi. As I expected, the hypotheses discussed, seem to overlook the factor I have envisaged to account for the increased size.

 

They note that no filtration or selection method is employed, that could differentially retain larger cells, but don´t larger cells, automatically retain differential representation of phenotypic biomass to genotypic ´info-mass´? Itś like the fat guy on the buss who takes up two seats but only pays for one fare. If I am correct, then the size itself is a spontaneous selection factor, owing to the limited space in the pipette during inoculation. The competition for fitness, is not favoring large cells in the culture as it multiplies in each generation, but the larger an individual cell is, the more biomass of itś counterparts it can displace in transition and therefore the more ´relative representation´ it confers to itś genes.

 

Please tell me Iḿ wrong, because I cant wait for an excuse to use that cute little ´doh!´ smiley. On second thoughts I guess I just did use it, so tell me I am right instead.

[Mr Skeptic]

Welcome!

 

This website says the increase in size is still not explained. It also has a few other evolution experiments (in stratified vials, and another in an overabundance of glucose).

https://www.msu.edu/~lenski/sciencearticle.html

[Skepticus]

Welcome!

 

This website says the increase in size is still not explained. It also has a few other evolution experiments (in stratified vials, and another in an overabundance of glucose).

https://www.msu.edu/~lenski/sciencearticle.html

 

Thanks Mr Skeptic. What I think they need to try, is variation in the size of the inoculation sample, then test it against the time (number of generations) it takes to reach the optimum size. The ratio of cell volume to sample volume will be much higher for the smaller sample, so I am guessing the selection pressure on the small volume inoculate should actually decrease the generations needed to reach optimum size, even though there is a smaller sample of variation in the gene pool. That, as I understand it, should go the other way if my conjecture is wrong, because the small sample should tend to inhibit the flow of information from one generation to the next. So less gene flow = less change, if the selection for size occurs in the flasks; whereas, less gene flow = more change, if the selection pressure is caused by the sampling process. There may also be a chance for an immediate adjustment towards the maximum cell-size threshold too, if post evolved generations are used and sample size adjusted. I have to go back and have a more careful read of what they have tried so far. Thanks for the info.