Impact of phages on the dynamics and metabolism of a model microbial community inspired from a fermented beverage
Résumé
Model microbial communities are often studied to better understand interactions and fluxes during fermentation
processes. However, models taking into consideration the potential impact of bacteriophages (phages), recognized
as drivers of microbial communities, are scarce. This study aimed at investigating the behavior of a model microbial
community inspired from cider, an alcoholic fermented beverage, including phages, and being subjected to dysbiosis.
The model microbial community was composed of three lactic acid bacteria strains belonging to the species
Liquorilactobacillus mali, Leuconosctoc mesenteroides and Oenococcus oeni, and of a Saccharomyces uvarum yeast
strain. Two phages were selected, targeting L. mali and Ln. mesenteroides strains. Experiments were performed in
MRS broth at 25°C and 15°C during 168 and 220 hours, respectively. Dysbiosis was created by a heat shock at 50°C
for 10 min applied when the community reached 105 CFU/mL before adding phages. Microbial community was
monitored by enumerating phages and bacteria, and measuring pH. The consumption of sugars and the production
of organic acids, ethanol and volatile compounds were also assessed by HPLC and GC-MS.
At 25°C, the community with phages (P) was closer to the control community (C) than to the community without
phages (D). Bacterial levels were all around 108 UFC/mL in conditions C and P, which were characterized by high
concentrations in 2-phenyl-ethanol, 3-methyl-butanol and octanoic acid. In condition D, L. mali and Ln. mesenteroides
were dominant while S. uvarum and O. oeni did not exceed 105 UFC/mL. The concentration of ethyl-lactate was
higher in condition D than in conditions C and P. After 220h at 15°C, condition P differed from conditions C and D,
as Ln. mesenteroides was not detectable while the other strains all reached approximately the same levels (about
107-108 UFC/mL).
The current study is the first report dealing with the impact of phages on a microbial model inspired from a fermented
beverage. It showed the importance of phages on microbial fluctuations and metabolism, as phages seemed to
contribute to restore microbial balance after dysbiosis, depending on temperature. Getting knowledge about phage
impacts in microbial models is crucial to guarantee the production of safe and sustainable foods.