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Impact of drinking water conditions and copper materials on downstream biofilm microbial communities and legionella pneumophila colonization
Citation:
Lu, J., H. Buse, V. Gomez-Alvarez, I. Struewing, J. Santodomingo, AND N. Ashbolt. Impact of drinking water conditions and copper materials on downstream biofilm microbial communities and legionella pneumophila colonization. JOURNAL OF APPLIED MICROBIOLOGY. Blackwell Publishing, Malden, MA, 117(3):905-918, (2014).
Impact/Purpose:
The aim of this pilot study was to explore the impact of introduced L. pneumophila with or without a host amoeba (Acanthamoeba polyphaga) to CDC reactors containing Cu or PVC coupons by examining changes in established biofilm communities in the effluent norprene tubing lines. Biofilm DNA diversity was determined by qPCR and 16S/18S cloning and Sanger sequencing. This study can help to understand microbial ecology and pathogen colonization in the drinking water PVC/copper pipe line.
Description:
Legionella pneumophila, the medically important species within the genus Legionella, is a concern in engineered water systems. Its ability to amplify within free-living amoebae is well documented, but its interactions/ecology within the microbial community of drinking water biofilms is poorly understood. This study characterized biofilm communities developed on effluent tubing from triplicate CDC biofilm reactors, containing either polyvinyl chloride (PVC) or copper (Cu) coupons. Pre-inoculation biofilms were formed over a twelve month period during which low chlorine residual drinking water was continuously run through the reactors, then a length of effluent tubing biofilm was sampled. The reactors were either 1) spiked with L. pneumophila strain Lp02; 2) spiked Lp02 and Acanthamoeba polyphaga; or 3) left unspiked as a control. Post-inoculation biofilms then continued to grow on the same tubing over a four month period before sampling. L. pneumophila were determined by qPCR and total bacterial and eukaryotic communities characterized from 16S and 18S rRNA gene clone libraries. For the microbial communities, sequences similar to Mycobacterium spp. (37%), α- and β-proteobacteria (~10%), free living amoeba like sequences (42%) and Hartmannella vermiformis (32%) were dominant, but no Acanthamoeba polyphaga was detected. Copper from upstream coupon displayed significant impact on effluent tubing microbial community. Specifically, in the tubing biofilms downstream of PVC than copper, there were higher species diversity with more microorganism OTU groups, more abundance for most of those appeared OTU groups and more density for some dominant sequences like Hartmannella vermiformis, while some dominant sequences like Mycobacterium spp. displayed less abundance or impact by copper. L. pneumophila (detected by qPCR assays targeting three virulence genes) was significantly higher in the tubing biofilm downstream of Cu coupons than that downstream of PVC coupons for the Lp02/Ap inoculated reactors. Ongoing work is seeking to further understand the ecology of L. pneumophila and associated community within drinking water pipe biofilms.
