Heterotrophic plate count vs. <i>in situ</i> bacterial 16S rRNA gene amplicon profiles from drinking water reveal completely different communities with distinct spatial and temporal allocations in a distribution net

Abstract

Heterotrophic plate count using ISO 6222 agar (HPC) vs. in situ bacterial (DF) community structure from corresponding samples of a drinking water distribution system were investigated by 16S rRNA gene-based polymerase chain reaction denaturing gradient gel electrophoresis (PCR DGGE) profiling. The investigation regime covered 10 different sampling locations and 2 points in time (t1, t2). In order to ensure accurate and reproducible 16S rRNA gene profile analysis, rigorous methodical evaluation and standardisation procedures were undertaken (DGGE optimisation, replication of PCR, multiplelane standardisation, representative sampling volume determination, application of multiple similarity coefficients). The reproducibility level of the profile analysis was determined to be ≥ 90% similarity. Two completely different communities were revealed from HPC vs. DF as indicated by DGGE analysis and sequencing. HPC populations could be identified as ubiquitously occurring cultivable copiotrophic microbes, whilst most DF sequences could be allocated to sequences from microorganisms found in oligotrophic aquatic environments. Spatial-and temporal-based 16S rRNA gene amplicon profile analysis from recovered communities further revealed contrasting results. As proven by Jackknife simulations, DF profiles remarkably corresponded to sampling time, whereas HPC profiles revealed spatial associations within the distribution system. Recovered data demonstrate that cultivation based HPC vs. direct cell-based investigations can result in completely different results if used for monitoring purposes in distribution systems.

A microbiology-based multi-parametric approach towards assessing biological stability in drinking water distribution networks

“…Similar to other drinking water systems analysed so far, Proteobacteria, which are present in most freshwater environments, dominated in the distribution networks (Burtscher et al, 2009;Eichler et al, 2006;Henne et al, 2012a;Hoefel et al, 2005a,b;Hong et al, 2010;Revetta et al, 2010;Roeder et al, 2010). However, a remarkably high abundance of candidate phyla was discovered in the present study.…”

“…As the result, the diversity indices (i.e., Chao1 and PD shown in Fig. S2) were relatively higher than in previous reports, where less sensitive methods such as DGGE or SSCP were used (Burtscher et al, 2009;Eichler et al, 2006), and also higher relative to the number of DGGE bands detected in this study (Fig. 3).…”

“…Members of the Comamonadaceae group are often found in different environments including drinking water, lake water, activated sludge or soil. As they are known to utilize a large variety of substrates, it is difficult to conclude what specifically caused the increase in the Comamonadaceae population in the drinking water network (Burtscher et al, 2009;Dias and Bhat, 1964;Pernthaler et al, 1998). Furthermore, due to the complexity of the drinking water network it was not possible to elucidate the exact cause of the change.…”

“…It is well known that only a minute fraction of drinking water bacteria readily grows on conventional nutrient media (e.g. Burtscher et al, 2009;Hammes et al, 2010a;Van der Kooij, 2003). Therefore, even though the HPC data (Fig.…”

“…Moreover, cultivation-independent microbial community analysis has to our knowledge never been used specifically as a tool to assess biological stability in non-chlorinated drinking water distribution networks. In fact, most information on the indigenous microbial community composition in drinking water is limited to chlorinated drinking water (e.g., Burtscher et al, 2009;Eichler et al, 2006;Henne et al, 2012aHenne et al, , 2012bHong et al, 2010;Revetta et al, 2010;Roeder et al, 2010;Pinto et al, 2012).…”