Identification of oestrone-degrading Betaproteobacteria in activated sludge by microautoradiography fluorescent in situ hybridisation

Natural oestrogens, which are degraded but not completely removed in wastewater treatment plants, are suspected of causing the endocrine disruption of aquatic organisms in the receiving water body. While several bacterial isolates were reported to be oestrogen-degrading bacteria, a previous study by the authors implied that only the unidentified rod-shaped Betaproteobacteria in chains were responsible for oestrone degradation by activated sludge especially at the sub-milligram per litre level. The Betaproteobacteria were suspected to be related to genera Sphaerotilus and Leptothrix according to morphological observations. Probe Spha823 was newly developed to target 16S rRNA gene clones obtained from activated sludge and closely related to the above genera. [(3) H]oestrone-incubated sludge samples showed that most of the (3) H-labelled cells hybridised with probe Spha823 by microautoradiography fluorescent in situ hybridisation. Spha823-defined cells were present in all three activated sludge samples tested, where they accounted for up to 3% of the total microbial biomass. Spha823-defined cells comprised 59.5-80.1% of the total microautoradiography-positive cells, which suggested that the Sphaerotilus-Leptothrix related bacteria were the most abundant microorganisms involved in estrone degradation (at 200 ?g l(-1) ) in the activated sludge samples.

Authors: Kurisu F, Zang K, Kasuga I, Furumai H, Yagi O. ;Full Source: Letters in Applied Microbiology. 2015 Feb 26. doi: 10.1111/lam.12407. [Epub ahead of print] ;