Microbial war

– Jan. 27, 2020

The oceans are the battleground of a struggle that dates back to the cradle of life. In a pioneering effort, marine biologists at the University of Southern California have now succeeded in actually revealing the arms race between viruses and bacteria. The conservation of biodiversity in ecosystems will benefit greatly from this knowledge.

Waging war on the waves with phages

Oceans are replete with viruses and bacteria. This location is where they play a pivotal part in the food chain and count among the largest concentrations of genetic diversity. While these microbes are mostly harmless to humans, they interminably wage internal war. Bacteriophages, or simply phages, are viruses that specifically target bacteria to use them as hosts. Scientists have now discovered the reason that this combat between bacteria and phages produces a perpetual stalemate. 

Mutants and the Red Queen

A multi-year study of San Pedro Channel off the coast of San Francisco mapped the species diversity of local viruses. The results proved that the variety of species in the water has been stable for a long while: 95% of species were present in all water samples. Among these species, there was a constant shift between different mutants that dominated the population for a limited time. Mutations make the next generation of viruses stand out slightly from their predecessors. As a result, the bacterial immune system fails to recognise them. Because this immune system will adapt as well, however, only new mutants can stay ahead of the system. Their continuous shift allows viruses to stay ahead of the bacterial immune system, so the struggle always ends in a stalemate. 

This discovery is among the few field studies that confirm the so-called 'Red Queen hypothesis', which proposes that organisms must constantly adapt in order to survive and proliferate. Otherwise, they will die in a constantly changing environment with ever-evolving opposing organisms. The tiniest life forms and their hosts are tirelessly trying to outdo one another. While the ocean may seem peaceful at first sight, it actually stages an invisible and incessant struggle for survival.