Leister, CarolinCarolinLeisterReiner, Johannes EberhardJohannes EberhardReinerGrießmeier, Victoria SofieVictoria SofieGrießmeierGescher, JohannesJohannesGescherHügler, MichaelMichaelHügler2023-08-282023-08-282023-10-01Water Research 244: 120494 (2023-10-01)https://hdl.handle.net/11420/42984Microbial water quality is routinely examined using the fecal indicator bacteria Escherichia coli, coliform bacteria and enterococci. Several practical cases in German drinking water distribution systems indicated invertebrates such as insects or gastropods as a source for the microbiological deterioration. Therefore, we examined three genera of Gastropoda (Arion, Helix and Cepaea) for the presence of fecal indictor bacteria in excreta using standard methods. Enterococci and coliform bacteria were detected in high concentrations (mean values of 1.5 × 106 and 6.3 × 106 per gram feces, respectively). E. coli was also detected, still specification revealed that what was assigned by standard ISO-methods to be E. coli was indeed a novel species of Buttiauxella, exhibiting β-D-glucuronidase activity, thus, explaining the false-positive results. Microbiome analyses confirmed the cultural results. Enterobacteriaceae were dominant in the samples, yet only very few sequences could be assigned to Escherichia. Our study suggests, that enterococci and coliform bacteria are an integral component in the gastropod microbiome, whereas E. coli might be derived from other sources with gastropods being a vector. The results further indicate, that the current concept of fecal indicator bacteria needs to be extended, as not only humans and homeothermic animals could be a source for fecal indictor bacteria, but also gastropods need to be taken into consideration.en1879-24482023Coliform bacteriaDrinking waterE. coliEnterobacteriaceaeEnterococciFecal indicator bacteriaGastropodaJournal Article10.15480/882.837410.1016/j.watres.2023.12049410.15480/882.8374Journal Article