Survival of thermostable φ6 genotypes in acidic, basic, and UV environments

Mutations can facilitate viral resistance to a single extreme environment. But it is unknown how often these mutations confer resistance to other extreme environments to which the viruses have not been previously exposed. Here, we focus on how prior adaptation to thermal stress affects viral survival during exposure to acidic, basic, and UV conditions. We exposed four genotypes (3 single mutants and an unmutated ancestor) of the bacteriophage φ6 with varying thermostability (low, high, or ancestral) to acid (pH 4) for 2 minutes, to base (pH 11) for 16 hours, or to UV radiation for 1 minute. We hypothesized the most thermostable genotype would also have higher survival in pH and UV stress. Unexpectedly, the least thermostable genotype demonstrated the highest survival in acidic, basic, and UV conditions, while the most thermostable genotype tended to show the lower survival in these environments. These results suggest that mutations that increase phage thermostability may not always increase pH or UV stability. Rather, molecular mechanisms of stability may depend on the environment. Investigating the survival of φ6 in other adverse environments could provide further information on molecular mechanisms of stability and viral survival strategies.