Batman — Shadow of the Bat #77: A Medical Review
Batman: Shadow of the Bat #77 “Arwin’s Theory of Devolution”
Alan Grant, writer
Mark Buckingham, penciler
Streptomycin, a potent antibiotic, will indeed kill off the bacteria E. coli — and it’s particularly effective in a Petri dish, where you don’t have to worry about nasty side effects such as kidney damage and deafness commonly seen with such antibiotics.
However, the description of how the bacteria evolve resistance to the antibiotic is a little off:
The mutation in question (resistance to Streptomycin) occurred before the antibiotic was ever added. It may be a recent mutation, or it may be an old one, but when it occurred isn’t important — all that matters is that some bacteria in the dish have the mutated gene and are resistant to the antibiotic.
Once the Streptomycin is added to the dish, the non-mutated bacteria — those susceptible to the antibiotic — die off, leaving only the mutated bacteria to reproduce.
The surviving bacteria don’t “mutate rapidly” to pass along the gene because simply being one of the few bacteria that survived guarantees that their genes will be passed to the next generation. In other words, the mutation has already occurred, no more is required for survival1.
In all fairness to the writer, these words are spoken by a college professor who is clearly more than a little nuts. So it is likely the character who misstates the science, and not Grant.
Notes:
1. There will of course be the usual random assortment of new mutations that may occur within any generation of bacteria.
July 15th, 2010 at 7:43 am
This is an example of the mistaken notion of “goal-oriented” evolution. That organisms somehow consciously evolve toward some specific end rather than, as you explain, simply produce in variety and those varieties which offer higher chances of survival (such as being reistant to a present poison) will out produce, and eventually replace, others.
On an another note, I was surprised to learn that bacteria had to deal with issues of gene dominance and resessitivty.
July 15th, 2010 at 8:04 am
I haven’t touched my biochemistry books in two months, but I would say that bacteria only have one single chromosome. No recessive/dominant genes.
July 15th, 2010 at 4:33 pm
There’s also the fun possibility that the resistant gene is on a plasmid, and can get transferred around the surviving population like a bootleg MP3.
Peer-to-Peer evolution!
July 16th, 2010 at 1:11 am
Official Comment
Oops. Good point about bacteria’s lack of dominant/recessive genes. Let me rewrite that bit…
July 16th, 2010 at 8:03 am
@Anu
I thought that to, but in doing some very cursory research (i.e. wikipedia) I found mention of the notion that baceterial DNA replicates faster than the bacteria divides, this often leaving a single bacterium with multple copies of its DNA. How that manifests itself within the bacterial phenotype, I couldn’t say.
July 16th, 2010 at 9:20 am
They writer may not have known it, but there may be something to what the mad scientist said: http://www.sciencemag.org/cgi/content/abstract/300/5624/1404?ijkey=1301a085d4929cc394e6e0f6ca253b1f5dd04dfd&keytype2=tf_ipsecsha
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