RESUMEN
Bacteriophages represent an alternative solution to control bacterial infections. When interacting, bacteria and phage can evolve, and this relationship is described as antagonistic coevolution, a pattern that does not fit all models. In this work, the model consisted of a microcosm of Salmonella enterica serovar Enteritidis and φSan23 phage. Samples were taken for 12 days every 48 h. Bacteria and phage samples were collected; and isolated bacteria from each time point were challenged against phages from previous, contemporary, and subsequent time points. The phage plaque tests, with the genomics analyses, showed a mutational asymmetry dynamic in favor of the bacteria instead of antagonistic coevolution. This is important for future phage-therapy applications, so we decided to explore the population dynamics of Salmonella under different conditions: pressure of one phage, a combination of phages, and phages plus an antibiotic. The data from cultures with single and multiple phages, and antibiotics, were used to create a mathematical model exploring population and resistance dynamics of Salmonella under these treatments, suggesting a nonlethal, growth-inhibiting antibiotic may decrease resistance to phage-therapy cocktails. These data provide a deep insight into bacterial dynamics under different conditions and serve as additional criteria to select phages and antibiotics for phage-therapy.
Asunto(s)
Genómica , Interacciones Microbiota-Huesped , Fagos de Salmonella/genética , Salmonella enteritidis/virología , Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Modelos Teóricos , Terapia de Fagos , Salmonella enteritidis/efectos de los fármacosRESUMEN
The performance of a demonstration-scale anaerobic reactor treating food waste was evaluated with an emphasis on microbial response to increasing organic loading rates (OLRs). The reactor exhibited a stable performance in terms of methane yield at OLR ranging from 1.0 to 2.4â kg VSâ L-1â day-1 (phases I and II), compared to that at phase III (OLR: 1.0-1.5â kg VSâ L-1â day-1) when the food waste exhibited greater acidity. Deep sequencing analysis revealed shifts in the microbial composition at each operational phase. The phyla Firmicutes and Bacteroidetes were favoured, whereas the abundance of Proteobacteria and Chloroflexi decreased at higher OLRs, indicating that fermenting-, hydrolytic- (and acidogenic) bacteria were selected under this condition. Changes were observed in the composition of methanogens, and not the abundance, in response to a shift in OLR. Methanosaeta and Methanospirillum dominated at low OLRs, indicating the importance of both acetoclastic and hydrogenotrophic methanogens for methane production during this condition. Methanosaeta almost disappeared at high OLRs, whereas Methanoculleus was favoured. Syntrophic prokaryotes were in high abundance (>9%), indicating that syntrophic methane production was important in this reactor. Syntrophic interactions between hydrogen-producer (Syntrophomonas and Desulfosporosinus) and hydrogenotrophic methanogens were more evident at high OLR. These results indicate that hydrogenotrophic methanogenesis contributed significantly to methane production at higher OLRs than when the reactor was operated at low OLR.