May 3, 2018
Two recent studies from the lab of
Hertz Fellow Jeff Gore at MIT’s Center for the Physics of Living Systems
illustrate a pair of compelling principles about the interactions that drive
our ecology and evolution.
first, featured on April 30 in the New York Times, is a study led by Gore lab postdoc Christoph
Ratzke, showing how a population of bacteria can pollute themselves into
extinction. The research, published in Nature
Ecology & Evolution, describes how rapid, unchecked growth of Paenibacillus
bacteria can turn their environment so acidic that the population drives itself
extinct. “The cells don’t realize what they’re doing in time to stop doing it,”
Gore told the Times.
their tendency for what Gore calls “ecological suicide,” Paenibacillus species remain a common and productive part of
microbial ecosystems, in part because other microbes have countervailing
effects on the environment. In fact, the microbes’ self-destructive tendencies
might be an important driver of diversity in microbial communities, where no
one species dominates.
a species environment does change rapidly – whether by its own doing or by
outside forces – it must adapt quickly or die. Another recent study from the
Gore lab shows how evolution might exploit accidents in the replication of the
genome to make that happen.
study, led by Gore lab postdoc Avihu Yona and published in Nature Communications, examined how likely a given DNA
sequence was to function as a promoter – the sequence of DNA near the beginning
of a gene where the process of reading the gene off the chromosome. Since
promoters have such powerful control over what genes are expressed – and
therefore every aspect of an organism’s behavior – one might think that it
would be hard for a new promoter to form through accidental mutation.
fact, exactly the opposite is true. In a randomly generated selection of gene
sequences of the right length to serve the role, the team discovered that fully
60% of them were only one mutation away from being a functional promoter.
would evolution select for a system where nearly any part of the genome could,
at any time, start accidentally being read out as if it were a gene? Yona says
a system like this could help quickly turn on new genes – whether latent in the
genome or taken in from other species through horizontal gene transfer – when
the cell needs to change quickly.
you’re far away from accidental expression, you’re also far away from an
evolutionary change when you need it badly,” says Yona. “You have to have some
mess in order to be able to adapt to new challenges.”
a balance between the desire to very tightly control how much a gene is
expressed, and being able to change that when necessary,” says Gore.
the transcription processes that promoters control – and the evolutionary
pressures that organisms face – are very similar for organisms from E. coli to humans, Gore says it wouldn’t
surprise him if our own transcription system were similarly balanced. “This
could have lessons not only for transcription in all life, but also in many
other processes” – from cellular metabolism to inter-organism cooperation – “where
you want to have this control.”