Victoria Frost, Ph.D. & Matthew Heard, Ph.D.




College of Arts and Sciences




Escherichia coli (E. coli) is a gram-negative bacteria species that thrives in a variety of environments around the world. Due to its widespread prevalence, it is commonly used as an indicator for fecal pollution and other pathogens. One place where it is not often looked for is oceanic beaches because E. coli is inhibited by salt. However, recent research has shown that E. coli often thrives in sand at many oceanic beaches. To determine how it persists in sand, we created a microcosm simulating the intertidal zone of an oceanic beach. Using this microcosm, we examined how varying levels of salinity (0-6%) affect the persistence of E. coli in these sandy environments. We found that there was a negative correlation between increasing salinity and the most probable number of E. coli colony forming units, which suggests that E. coli is being inhibited by salinity to a degree. However, we still found that E. coli was able to persist at all salt concentrations including those that exceed normal oceanic salinity. Collectively, our findings suggest that E. coli may be able to persist on sandy beaches despite the stress of salinity and may be a useful tool in the future for assessing these

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