Functional genomics of chitin degradation byVibrio parahaemolyticusreveals finely integrated metabolic contributions to support environmental fitness

Abstract

Vibriospecies are marine prokaryotes that inhabit diverse ecological niches, colonizing abiotic and biotic surfaces. These bacteria are vital players in the global carbon cycle, assimilating billions of tonnes of chitin for carbon (and nitrogen) metabolites. Many bacterial proteins involved in the process-including chitinases, sugar transporters, and modifying enzymes-have been well studied. However, the genetic functional interplay and key drivers ofVibriocompetitive survival in the presence of chitin as the dominant carbon source is not understood. To address this question, we carried out transposon sequencing (Tn-seq) to determine the genetic fitness ofVibrio parahaemolyticusmutants grown on chitin as a sole carbon source. Along with validating knownVibriogenes associated with chitin metabolism, our data newly identified vital roles for an unclassified OprD-like import porin and a HexR family transcriptional regulator. Furthermore, we functionally implicated HexR in regulating multiple physiological processes involved inV. parahaemolyticusenvironmental survival including carbon assimilation and cell growth, biofilm formation, and cell motility. Notably, our data revealed a strict requirement for HexR in filamentous cell morphology, a critical trait forV. parahaemolyticusenvironmental fitness. Therefore, a vital import porin and genomic regulation mediated by HexR supports multiple physiological processes forVibriochitinolytic growth and environmental fitness.