Good question! I don’t know, but I think that they don’t necessarily need to. Something I didn’t get into in the post but which is pretty important for understanding bacterial genomes is that they do horizontal gene transfer, which basically means that they trade genes between individuals rather than exclusively between parents and offspring.
From what I understand, this means that although on average the bacteria shed the unhelpful DNA if given the opportunity, so long as a few individuals within the population still have the gene, it can get rapidly reacquired when needed. I don’t know exactly how the math works out, but I’d guess that in big enough populations, if antibiotic encounters are somewhat common, then probably they don’t need to do it de novo each time?
This also means bacterial genomes are much more distributed than eukaryotic ones. So long as any individual bacteria has some gene, it’s “as if” the whole species has it. Which means their genomes are, in a sense, actually longer than they might naively seem. Being distributed has advantages: no single genome needs to be very long, yet the population can hold onto useful stuff. But it also has disadvantages: any adaptation that relies on genes being close together in a single genome is unlikely to develop (which includes e.g. all of the regulatory hierarchy stuff mentioned in the post). So I do still expect that the pressure towards short genomes meaningfully stunts bacterial complexity.
Good question! I don’t know, but I think that they don’t necessarily need to. Something I didn’t get into in the post but which is pretty important for understanding bacterial genomes is that they do horizontal gene transfer, which basically means that they trade genes between individuals rather than exclusively between parents and offspring.
From what I understand, this means that although on average the bacteria shed the unhelpful DNA if given the opportunity, so long as a few individuals within the population still have the gene, it can get rapidly reacquired when needed. I don’t know exactly how the math works out, but I’d guess that in big enough populations, if antibiotic encounters are somewhat common, then probably they don’t need to do it de novo each time?
This also means bacterial genomes are much more distributed than eukaryotic ones. So long as any individual bacteria has some gene, it’s “as if” the whole species has it. Which means their genomes are, in a sense, actually longer than they might naively seem. Being distributed has advantages: no single genome needs to be very long, yet the population can hold onto useful stuff. But it also has disadvantages: any adaptation that relies on genes being close together in a single genome is unlikely to develop (which includes e.g. all of the regulatory hierarchy stuff mentioned in the post). So I do still expect that the pressure towards short genomes meaningfully stunts bacterial complexity.