Estrogen-Degrading Bacteria Isolated

A bacterium that efficiently degrades estrogens in wastewater treatment plants has been identified by Kung-Hui Chu and her coworkers at Texas A&M University (Environ. Sci. Technol., DOI: 10.1021/es060923f). Detection of harmful endocrine-disrupting chemicals, including estrogens, in treated wastewater is prompting researchers to take a closer look at how the compounds can be biodegraded more effectively. Working with sludge samples from a treatment plant, Chu's group isolated 14 diverse bacteria that can degrade 17β-estradiol and identified them by gene sequencing. Natural 17β-estradiol (shown) and its degradation product estrone (with the alicyclic hydroxyl group converted to a keto group) along with synthetic 17α-ethynylestradiol (found in contraceptives) are the major contributors of estrogenic activity in treated wastewater. Although all 14 bacteria degrade 17β-estradiol to estrone, only three of the species further degrade estrone, and only one of those three, a Sphingomonas species, can degrade the estrogens quickly to nonestrogenic compounds. The researchers are now looking to pinpoint the responsible enzyme produced by the bacterium, which could lead to a method to enhance total estrogen degradation in wastewater treatment plants.