Abstract:

Prokaryotic and eukaryotic cells both release heterogeneous extracellular vesicles (EVs), suggesting that vesiculation is a fundamental process for cellular life. EVs have diverse functions in cell-to-cell communication, as well as interactions between cells and their surrounding environments. Denitrification is a crucial metabolic pathway for bacteria to acquire energy and is a key process in global nitrogen cycle. However, the involvement of EVs in denitrification process remains to be explored. Here, we examined EV production under varying oxygen and nitrate concentrations, which are the key factors regulating denitrification. Pseudomonas aeruginosa, a ubiquitous environmental opportunistic pathogen, is well-characterized for its denitrification capability. Using proteomic analysis, we found that EVs released by this pathogen carried more proteins predicted to facilitate nutrient acquisition and pathogenesis under aerobic conditions, with the potential for pathogenesis to be further enhanced in the presence of nitrate. Under anaerobic denitrification, EVs exhibited significantly higher levels of peptidoglycan degradation enzymes compared to those under aerobic conditions, suggesting that EVs are involved in bacterial survival. Cell culture experiments further revealed the lytic effect of EVs that are produced under anaerobic conditions. Notably, these EVs cannot be effectively removed by drinking water purification processes. Our work shows that EVs mediate bacterial interactions during denitrification and they could be present in drinking water, suggesting potential health risks caused by EVs released from pathogenic bacteria.

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