Genomic and Transcriptomic Profiles of Hyperswarming Vibrio cholerae O1

Vibrio cholerae O1 is the etiological agent of pandemic cholera. This Gram-negative waterborne pathogen infects millions and leads to 100,000 deaths annually. There is substantial evidence that motility and virulence are inversely regulated, encouraging the continued refinement of motility-related research for this pathogen. A class of motility called 'swarming' is the fastest and most organized method of bacterial motility on semi-solid surfaces, and spontaneously occurring "hyperswarmer" (HS) Vibrio cholerae mutants were the subjects of this research. Reduced-function motility mutants have been previously profiled with NGS approaches, but the global genomic and transcriptomic profiles of HS Vibrio cholerae have yet to be established. The goal of this research was to investigate possible genomic bases for the emergence of the HS phenotype, as well as characterizing the transcriptome of such mutants. High quality NGS short-read sequences generated from Illumina MiSeq allowed for genomic variant discovery at the single-nucleotide level, while TGS long-reads produced by MinIon Nanopore allowed for the construction of closed genome sequences. RNAseq was utilized for generating transcriptomic profiles of several mutant types. We found parallel microevolution between HS mutants, as they displayed an array of different point mutations occurring within a limited variety of genes. Interestingly, the genes included those involved with virulence, c-di-GMP modulation, and chemotaxis. This research provides a novel whole-genomic and whole-transcriptomic framework for hyperswarming V. cholerae O1, which may help in further development of counteractive measures toward this deadly pathogen.