DIFFERENTIAL VIRAL EFFECTS ON THE GROWTH EFFICIENCY OF FRESHWATER BACTERIOPLANKTON IN EUTROPHIC VS. NON-EUTROPHIC LAKES

In aquatic environments, the understanding of viral influence on bacterial carbon metabolism, particularly with nutrient availability as a key factor, remains limited. To address this, we investigated viral regulation of carbon-based bacterial growth efficiency (BGE) in a series of freshwater systems in the French Massif Central, categorized into two trophic states: eutrophic and non-eutrophic lakes. Our comparative analysis revealed that microbial abundances, including both viruses and bacteria, were approximately three times higher in eutrophic lakes than in non-eutrophic ones. This pattern was mirrored by higher bacterial production and viral lytic activity in eutrophic lakes. Variability in BGE, ranging from 10% to 60%, was attributed to the decoupling of bacterial respiration from production. In eutrophic lakes, viruses had an antagonistic effect on BGE through the selective lysis of susceptible bacterial communities. In contrast, in non-eutrophic lakes, viral-induced substrate release (viral shunt) had a synergistic effect on carbon metabolism, benefiting non-target bacterial populations. The significance of these viral processes—lysis and substrate release—on BGE was further supported by the strong correlation between bacterial abundance and production, which is often considered a proxy for top-down control. Overall, the dual role of viruses, exerting negative effects through host mortality and positive effects via substrate supply, can have important implications for carbon cycling within freshwater bacterioplankton communities.

Presentation Preference: Poster

Primary Presenter: Telesphore Sime-Ngando, CNRS, Centre National de la Recherche Scientifique (telesphore.sime-ngando@uca.fr)

Authors:

Telesphore Sime-Ngando, Laboratoire Microorganismes: Génome et Environnement  (telesphore.sime-ngando@ird.fr)