Growth rate of metal resistant bacteria.

Reichard, Larry

Bacteria isolated from the environment show the ability to tolerate a wide range of contaminants, pollutants and toxins. Previously in our lab, bacteria were isolated from soil contaminated with lead. These four isolates, Variovorax paradoxis, Pseudomonas fluorescens and two unidentified species were able to grow in medium containing lead. In our experiments, we measured the rate of growth based on optical density of liquid cultures, when grown in increasing concentrations of lead. We found that the effect varied among the organisms. We also found that the growth rate was dependent on the temperature of the culture. Additionally, we tested the effect of Co, Cd and Zn on growth rate, as many lead resistant organisms are also resistant to these heavy metals. These metals also show a varying effect depending on the organism tested. We used a lab strain of E. coli as a control, because it has little resistance to heavy metals. We will present data that suggests that each of these lead resistant bacteria are unique in their ability to grow in the presence of heavy metal.

* Romero, M., and T. Giblin. Department of Natural Sciences, Stephens College.