Halotolerance in the Southeastern Michigan Soil Microbiome

Abstract

Many communities in the Midwest and Northeastern United States use salt to treat icy roads in the winter. Studies have shown that the many years of salt application have had harmful effects on freshwater ecosystems, roadside flora and fauna, and overall wetland biomes. We were interested in investigating the impact that road salt use has had on the soil microbiome. Specifically, we sought to determine if microbes that reside near salted roads have become more tolerant of salt, or more halotolerant, than microbes that reside far from roads. We accomplished this by first collecting soil samples from near roads (exposed to road salt) and far from roads (not exposed to road salt) from various parks across Southeastern Michigan. Salinity measurements were taken by mixing 1 g soil per 1 mL distilled water. We then used these soil samples to compare the number of colony forming units on 5% NaCl nutrient agar plates and standard nutrient agar plates, investigate growth rate differences between these microbes in 5% NaCl nutrient broth, and sequence various salt intolerant, halotolerant, and halophilic microbes. This allowed us to uncover relationships between the soil salt concentrations, the microbiome distances from roads, and the halotolerance of the microbiomes, as well as to gain some insight into the microbiome population makeup. Preliminary data suggests that there may be a correlation between the salt concentration in soil (ppm) and the overall soil microbiome halotolerance. This indicates that microbiomes closer to roads (which we have shown to have greater soil salt concentration) are likely more halotolerant than microbiomes further from roads (which we have shown to have lesser soil salt concentration). We will investigate the growth rate differences between halotolerant and nonhalotolerant strains as well as determine the genus of the microbes to provide further insight into the composition of the microbiome. This study suggests that the application of road salt is not only affecting wetland biomes but may also be having an effect on the soil microbiome as well.Support or Funding InformationSpecial thanks to Lawrence Technological University for laboratory space, equipment, and funding to carry out this study.