Genome-Wide Identification of Fitness Factors in Seawater for .

Marine pathogens are transmitted from one host to another through seawater. Therefore, it is important for marine pathogens to maintain survival or growth in seawater. However, little is known about how marine pathogens adapt to living in seawater environments. Here, transposon insertion sequencing was performed to explore the genetic determinants of survival in seawater at 16 and 28°C. Seventy-one mutants with mutations mainly in metabolism-, transportation-, and type III secretion system (T3SS)-related genes showed significantly increased or impaired fitness in 16°C water. In 28°C seawater, 63 genes associated with transcription and translation, as well as energy production and conversion, were essential for optimal survival of the bacterium. In particular, 11 T3SS-linked mutants displayed enhanced fitness in 16°C seawater but not in 28°C seawater. In addition, 13 genes associated with oxidative phosphorylation and 4 genes related to ubiquinone synthesis were identified for survival in 28°C seawater but not in 16°C seawater, which suggests that electron transmission and energy-producing aerobic respiration chain factors are indispensable for to maintain survival in higher-temperature seawater. In conclusion, we defined genes and processes related to metabolism and virulence that operate in to facilitate survival in low- and high-temperature seawater, which may underlie the infection outbreak mechanisms of and facilitate the development of improved vaccines against marine pathogens. is one of the most important marine pathogens and causes serious edwardsiellosis in farmed fish during the summer-autumn seasonal changes, resulting in enormous losses to aquaculture industries worldwide. Survival and transmission of the pathogen in seawater are critical steps that increase the risk of outbreaks. To investigate the mechanism of survival in seawater for this marine pathogen, we used transposon insertion sequencing analysis to explore the fitness determinants in summer and autumn seawater. Approximately 127 genes linked to metabolism and virulence, as well as other processes, were revealed in to contribute to better adaptations to the seasonal alternations of seawater environments; these genes provide important insights into the infection outbreak mechanisms of and potential improved treatments or vaccines against marine pathogens.