High-temperature adaptation of three Sonoran Desert Bacillus species: Ecological and evolutionary prospects

Abstract

Growth at high temperature of wild isolates of three species of Bacillus was analyzed to assess potential responses to global warming. Experimental populations were grown at temperatures from 32° to 60° C. The higher temperatures include ones near and above maxima previously reported for laboratory strains. Summer soil temperatures, three centimeters below the ground surface, were recorded at the same site from which the wild isolates came, show that temperatures in the Sonoran Desert often reach 50° to 60° C. The growth data show that the desert isolates of B. subtilis and B. licheniformis have thermal maxima close to those reported by Gordon et al. (1973), while B. megaterium grew well at 2-3°C above the reported maximum. Global Climate Models predict a rise of 1° to 4.5°C over the next 60-100 years. Such a rise could shorten periods of active growth and nutrient cycling by Bacillus decomposers.