Comments on: Replaying evolution reveals the benefits of being slow and steady

By: JSmith

JSmith — Thu, 31 Mar 2011 09:21:51 +0000

Lenski bred the dozen strains from a common ancestor in ***1988.***

By: amphiox

amphiox — Sat, 19 Mar 2011 04:44:07 +0000

Yep, it’s the citrate-using one. Neat, huh?

Mondo neat indeed. That picture is “evolution before our eyes”. 12 initially identical strains, from one common ancestor, and now 20 years later, there is a difference between them so obvious that we can see it with the naked eye. So obvious that someone with no training whatsoever in microbiology can recognize that it is there.

By: amphiox

amphiox — Sat, 19 Mar 2011 04:37:57 +0000

One question that interests me is how the EWs managed to survive those first 350 generations or so before they overtook the ELs in relative fitness. Was it simply a question of hanging on as a minority population in head-to-head competition until they turned the competitive tables?

Or was it something more complicated that that? Presumably, in the original experiment, at generation 500, there were other variants in the population besides the EW and EL strains tested. Could there have been interactions between the EWs and other, untested variants, within the ‘ecosystems’ of the flasks that provided a sheltered niche for the EWs that perhaps protected them to some degree from direct competition with the ELs, giving them the opportunity to survive until they accrued to additional mutations that ultimately allowed their relative fitness to overtake the ELs?

By: Ed Yong

Ed Yong — Fri, 18 Mar 2011 23:39:30 +0000

@Amphiox – Yep, it’s the citrate-using one. Neat, huh?

@DavidB – The tortoises and hares didn’t come from separate flasks. They were competing strains within the same cultures. The earlier post refers to a different paper coming out of the same experiment and it’s irrelevant to this story. The events described in that post happened after 30,000+ generations; the events in this one started happening after just 500-1500.

By: DavidB

DavidB — Fri, 18 Mar 2011 23:21:01 +0000

I’m not sure what the significance of this is supposed to be. If the 12 evolving strains are isolated from each other, they are not in competition, the ‘tortoises’ are able to go at their own pace, and may eventually speed up and pass the ‘hares’. It is interesting if they do (and to understand the mechanisms), but does this have any relevance to the course of evolution in nature, where the ‘tortoises’ would just go extinct?

I notice that in the earlier post there was a rather different account of the experiment – or maybe a different version of it. In that version the ‘tortoises’ survived because they were able to exploit a different nutrient from the one favoured by the ‘hares’. This meant they were able to survive in low concentrations despite their competitive disadvantage.

By: Stephen

Stephen — Fri, 18 Mar 2011 16:16:44 +0000

These e. coli haven’t learned to read, obviously.

“There are no limits. There are plateaus, and you must not stay there; you must go beyond them. If it kills you, it kills you.” – Bruce Lee

By: Douglas Watts

Douglas Watts — Fri, 18 Mar 2011 03:20:33 +0000

Were they randomly exposed to DDT?

By: amphiox

amphiox — Fri, 18 Mar 2011 01:19:02 +0000

Interestingly, this seems to parallel, at least in broad strokes, patterns observed in the fossil record. The most successful and dominant lineages at any given time (the hares) often end up going extinct and very rarely end up being the ancestors of the most successful and dominant lineages of later time periods, which most often descend from rarer, less conspicuous ancestors (the turtles).

By: amphiox

amphiox — Fri, 18 Mar 2011 01:09:08 +0000

In the picture, is the strain in flask A-3 (the one with the uniquely cloudier fluid in the flask) the famous citrate strain?

By: Marian Maroszek

Marian Maroszek — Thu, 17 Mar 2011 19:31:04 +0000

“Last month, the bacteria passed their 50,000th generation.”

Last year I guess – February 2010 .

Regards.