Effect of oxygen and temperature on the dynamic of the dominant bacterial populations of pig manure and on the persistence of pig-associated genetic markers, assessed in river water microcosms

Aims: The aim is to evaluate the dynamic of Bacteroides-Prevotella and Bacillus-Streptococcus-Lactobacillus populations originating from pig manure and the persistence of pig-associated markers belonging to these groups according to temperature and oxygen. Methods and Results: River water was inoculated with pig manure and incubated under microaerophilic and aerobic conditions, at 4 and 20 degrees C over 43 days. The diversity of bacterial populations was analysed by capillary electrophoresis-single-strand conformation polymorphism. The persistence of the pig-associated markers was measured by real-time PCR and compared with the survival of Escherichia coli and enterococci. Decay was characterized by the estimation of the time needed to produce a 1-log reduction (T90). The greatest changes were observed at 20 degrees C under aerobic conditions, leading to a reduction in the diversity of the bacterial populations and in the concentrations of the Pig-1-Bac, Pig-2-Bac and Lactobacillus amylovorus markers with a T90 of 10 5, 8 1 and 17 2 days, respectively. Conclusions: Oxygen and temperature were found to have a combined effect on the persistence of the pig-associated markers in river waters. Significance and Impact of the Study: The persistence profiles of the Pig-1-Bac, Pig-2-Bac and Lact. amylovorus markers in addition to their high specificity and sensitivity support their use as relevant markers to identify pig faecal contamination in river waters.