The Web of Life (36-8) Bacteria Altruism


Haemophilus influenzae – a bacterium in the respiratory tract that can cause ear infections – needs dietary iron like everything else alive. Some manage to collect more than they need, while neighbors may run short. In this instance, the iron-rich readily share to help their brethren.

Bacteria under attack by antibiotics signal their kin, increasing the chances of some surviving, as the informed ramp their resistance to fend off the assault.

Typically, only a small number of bacteria in a colony are drug resistant. These hardy souls help their more vulnerable comrades survive, even at a cost to themselves.

Bacteria in the human body are known to donate antibiotic-resistant genes to other species of bacteria. Genetic information that gives antibiotic resistance is shared by plasmid transfer to microbial neighbors. Bacteria know exactly the value of what they are sharing.

There is self-interest in maintaining a stable ecosystem. A self-respecting bacterium won’t let neighbors be poisoned.

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Bacteria selectively pick up genetic material in the environment in a process termed transformation. The death of bacteria, or simply loose plasmids, make free DNA available.

Free DNA stabilizes in the soil by combining with soil components. These are taken up by living cells. Biofilms attached to river stones happily practice what is called epilithon: aquatic transformation.

Single-celled bacteria and archaea have an immune response to viruses that infect them. As a physical memory, these prokaryotes retain strands of nucleic acids that convey information about the incursion. When a bacterium recognizes that it has been invaded, it splices and copies signature genetic material from the pathogen, then distributes that for others to pick up. By doing this, a bacterium transfers information vital to conferring immunity to that pathogen.