Identifying cadmium-resistant, probiotic bacteria for potential protection against cadmium toxicity in Drosophila melanogaster

Cadmium (Cd) is a heavy metal with many beneficial industrial uses, but can cause harmful health effects when toxicity is reached. Usually, toxicity occurs through the accumulation of Cd either through inhalation or ingestion. Cadmium toxicity can affect many organs, but damage to kidney and liver is most common due to concentration at those sites. The body is capable of reducing toxicity; however, too much Cd can overload this compensatory mechanism. Bacteria have natural mechanisms to counter heavy metal toxicity, so finding a bacterium capable of reducing Cd toxicity in a host would prove beneficial. It is unknown if intestinal probiotic bacteria resistant to Cd toxicity, can serve to protect the host against ingested Cd and subsequent toxicity. The objective of this study was to select, identify and characterize bacteria displaying resistance to high-levels of Cd. After testing four commercially available probiotic preparations, the most resistant to Cd was Bacillus coagulans GBI-30, 6086, which grew 1 mM of Cd. A second bacterium isolated from a human fecal sample, likely Escherichia coli, was resistant at 2 mM Cd concentration. Both bacteria were fed separately to Drosophila melanogaster (fruit fly) over 5 days, before the flies were fed toxic levels of Cd. Flies fed the Cd-resistant bacteria died at similar rates as the control population. Although no survival benefit was observed, additional experiments are underway to determine if these bacteria are becoming established in the fly’s gut