<em>In situ</em> characterization of microbial degraders of Triclosan and  Methyl-Triclosan from wastewater treatment plants

 

Partial or complete mineralization of contaminants by use of microorganisms is generally the most economic way of removing by-products produced by the industry or contaminants derived from polluted environments. The vast diversity of microorganisms found in complex microbial environments such as soil and sediments exposes the selection of microbes with very specialized functions. Some of these even reveal a capability to remove specific contaminating and often toxic compounds. One example is gasoline-polluted soil sites in which specific types of microorganisms with the ability to oxidize contaminants can be found in high numbers. Understanding the physiology and conditions under which these microorganisms thrive is important for optimizing the removal. Bioaugmentation has been widely applied in contaminated soil, but require establishment of cultures capable of proliferating under very artificial conditions. With very low culturability (less than 1% of all microorganisms have hitherto been cultivated in artificial media) and even lower chances of survival of the bioaugmented cultures (due to selective grazing or loss of adaptation to the environment), this approach are not suitable for most purposes. Thus organisms representative for the true xenobiotic degraders in the environment might be difficult to cultivate and impossible to use for bioremediation. Therefore, in this project we will apply culture-independent techniques to identify and characterize the microbial community able to degrade Triclosan and Triclosan-Methyl as well as study the effect of these compounds on key functional groups in the wastewater treatment process.

We propose to identify the active degrading microorganisms of Triclosan and Triclosan-Methyl by applying Stable Isotope Probing (SIP) with 13C-labeled Triclosan or Triclosan-Methyl. The information on the actively involved Triclosan-degrading microorganisms will be confirmed and quantitatively evaluated by means of microautoradiography, an extremely sensitive technique that allows the study of substrate uptake at a single cell resolution. We will investigate the substrate uptake profile of degrades of xenobiotics during various growth conditions and measure both consumption rates as well as identify the most important key-players by a combination of Microautoradiography with Fluorescence In Situ Hybridisation (MAR-FISH).

With this approach it will be possible through cultivation-independent techniques to describe not only the phylogeny of cells in a reactor with a degradation of a given contaminant, but also to identify the organisms actively utilizing the compound and determine under which growth conditions as well as wastewater treatment plant configurations they seem to be most active. From these data we expect to be able to increase the microbial removal of these xenobiotic compounds in real wastewater treatment plants.

In this project the microbial communities in 10 selected wastewater treatment plants (selected from their ability to utilise Triclosan and Triclosan-Methyl) will be investigated.