Survival and persistence of host-associated Bacteroidales cells and DNA in comparison with Escherichia coli and Enterococcus in freshwater sediments as quantified by PMA-qPCR and qPCR

WATER RESEARCH

卷:87

Article

Kim, Minji¹  Wuertz, Stefan^1,2,3 

[1] Univ Calif Davis, Dept Civil & Environm Engn, Davis, CA 95616 USA

[2] Nanyang Technol Univ, SCELSE, Singapore 637551, Singapore

[3] Nanyang Technol Univ, Sch Civil & Environm Engn, Singapore 639798, Singapore

关键词: Sediment;    Microbial source tracking;    Bacteroidales;    Fecal indicator bacteria;    Propidium monoazide;    Quantitative PCR;   

DOI  :  10.1016/j.watres.2015.09.014

来源: Elsevier

【 摘 要 】

Decay of the fecal source identifier Bacteroidales in sediments has not been studied until now. Two types of microcosms inoculated with human, cow and dog feces were constructed to investigate the survival and persistence of host-associated Bacteroidates 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 oxygen-free sediments at two temperatures (6 degrees C and 20 degrees 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 propidium monoazide (PMA) 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 (Escherichia coli 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 degrees C, with two-log reduction times (T-99) >56 d (cells) and >169 d (DNA). Bacteroidales DNA persisted up to five times longer than cells in anaerobic microcosms at 6 degrees C, whereas decay rates of cells and DNA were not significantly different at 20 degrees C in anaerobic microcosms. In core microcosms, the levels of Bacteroidaies cells and DNA decreased approximately six times more slowly in sediments than in overlying water; T-99 values of Bacteroidates cells and DNA were 6-9 d (water) and 29-82 d (sediment). The survival of universal, human-, ruminant- and dog-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 E. coli 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. (C) 2015 Elsevier Ltd. All rights reserved.

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