Inorganic Nitrogen Availability Drives Metabolic Specialization and Adaptive Strategies in Vibrio harveyi and Vibrio parahaemolyticus
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Nitrogen availability is a key factor shaping microbial metabolism, ecological adaptation, and nitrogen cycling in aquatic environments. Members of the genus Vibrio are ubiquitous heterotrophic bacteria in marine and aquaculture ecosystems, yet their responses to different inorganic nitrogen sources remain poorly understood. Here, we systematically compared the growth characteristics, nitrogen transformation capacity, and molecular responses of Vibrio harveyi and Vibrio parahaemolyticus under ammonium (NH 4 + ), nitrate (NO 3 − ), and nitrite (NO 2 − ) conditions using physiological assays, comparative genomic analysis, and transcriptomic profiling. V. harveyi exhibited broader nitrogen utilization capacity and was able to grow under all three nitrogen conditions, whereas V. parahaemolyticus showed a strong preference for NH 4 + and limited growth under NO 3 − and NO 2 − conditions. Moreover, V. harveyi displayed rapid population expansion accompanied by reduced long-term viability, while V. parahaemolyticus maintained greater population stability. Both species showed NO 3 − accumulation during growth despite lacking canonical nitrification genes under NH 4 + condition, suggesting the potential involvement of non-canonical heterotrophic nitrification processes. Transcriptomic analysis revealed nitrogen source-dependent metabolic specialization in V. harveyi . NH 4 + availability promoted motility-associated responses and metabolic overflow, whereas NO 3 − induced iron acquisition-related pathways and NO 2 − activated assimilatory nitrite reduction coupled with oxidative stress adaptation. These findings demonstrate that inorganic nitrogen availability drives divergent metabolic and adaptive strategies in Vibrio , providing new insights into their nitrogen metabolic potential and ecological roles in aquatic environments.
Importance
This study demonstrates that V. harveyi and V. parahaemolyticus exhibit distinct inorganic nitrogen utilization strategies, with V. harveyi displaying broader nitrogen utilization capacity. Transcriptomic and metabolomic analyses revealed that different nitrogen sources drive distinct metabolic and environmental adaptation responses in V. harveyi , including enhanced motility-associated functions and metabolic overflow responses under NH 4 + condition, increased iron acquisition pathways under NO 3 − condition, and activation of assimilatory nitrite reduction coupled with oxidative stress adaptation under NO 2 − condition. Furthermore, significant nitrate accumulation was observed in both Vibrio strains during ammonium cultivation despite the absence of canonical nitrification genes, suggesting unexplored nitrogen transformation potential in vibrios. This study expands our understanding of how inorganic nitrogen availability shapes microbial adaptation strategies and ecological functions in aquatic environments.
