Survival and persistence of host-associated Bacteroidales cells and DNA in comparison with @entity526 and Enterococcus in freshwater sediments as quantified by XXXX -qPCR and qPCR.

@entity1 @entity235 @entity26 @entity4515 @entity15777 @entity291 @entity526
UNASSIGNED: Decay of the fecal source identifier Bacteroidales in sediments has not been studied until now. Two types of microcosms inoculated with @entity1 , @entity291 and @entity235 feces were constructed to investigate the survival and persistence of host-associated Bacteroidales cells and their DNA, respectively, in freshwater sediments: (i) a completely anaerobic microcosm where feces were entirely mixed with sediments for estimating decay of Bacteroidales in @entity26 -free sediments at two temperatures (6    C and 20    C) and (ii) a core microcosm where feces in the overlying water column settled on top of undisturbed core sediments. Quantitative PCR (qPCR) along with @entity15777 ( @entity4515 ) was used to differentiate between genetic markers present in intact cells and total intracellular as well as extracellular marker DNA. Regulated fecal indicator bacteria were measured by cultivation ( @entity526 and Enterococcus) and qPCR (Enterococcus) in relation to Bacteroidales-associated host markers. In anaerobic microcosms, the survival and persistence of Bacteroidales cells and DNA in sediments were considerably extended, especially at the lower temperature of 6    C, with two-log reduction times (T99) >56  d (cells) and >169  d (DNA). Bacteroidales DNA persisted up to five times longer than cells in anaerobic microcosms at 6    C, whereas decay rates of cells and DNA were not significantly different at 20    C in anaerobic microcosms. In core microcosms, the levels of Bacteroidales cells and DNA decreased approximately six times more slowly in sediments than in overlying water; T99 values of Bacteroidales cells and DNA were 6-9  d (water) and 29-82  d (sediment). The survival of universal, @entity1 -, ruminant- and @entity235 -associated Bacteroidales cells in sediments was similar in both microcosms under each given condition, as was the persistence of DNA. Decay rate constants of Bacteroidales cells and DNA were comparable with those of cultivable Enterococcus and @entity526 cells in core sediments while Enterococcus DNA levels fluctuated without noticeable decay. The prolonged persistence of host-associated Bacteroidales suggests that sediments should be considered in practical applications of microbial source tracking, because they can act as non-point sources of fecal markers.
