AimsTo demonstrate the resuscitation-promoting activities of recombinant YeaZ from Vibrio harveyi SF-1. Methods and ResultsThe gene of resuscitation-promoting factor YeaZ was cloned from genomic DNA of V. harveyi SF-1. The gene was expressed in Escherichia coli, and the expressed protein was purified by Ni2+-affinity chromatography. A yeaZ mutant was constructed by using the suicide plasmid pNQ705 with homologous recombination. Disruption of yeaZ did not affect cell growth significantly in 2216 E broth at 28 degrees C. The wild-type and mutant viable but nonculturable (VBNC) cells could be resuscitated by temperature upshift method. In addition, the recombinant YeaZ increased the culturable counts from 127x10(4)CFU per ml and 199x10(4) CFU per ml to 288x10(5)CFU per ml and 459x10(5) CFU per ml, respectively. After the VBNC cells of wild-type and mutant cells were maintained at 4 degrees C for 120days, no resuscitation was obtained by temperature upshift method, but addition of the recombinant YeaZ promoted the resuscitation of the wild-type and mutant cells, with the culturable cell counts of 113x10(3) and 144x10(3) CFU per ml, respectively. Disruption of yeaZ decreased the virulence of V. harveyi in zebrafish. The lethal dose 50% of the yeaZ null mutant was more than 10-fold higher than that of the wild-type cells. ConclusionsThe recombinant YeaZ could efficiently promote resuscitation of the wild-type and mutant cells of V. harveyi from VBNC to culturable state. The protein also promoted resuscitation of the VBNC wild-type and mutant cells, which were maintained at 4 degrees C for 120days and not recovered by temperature upshift method. Disruption of yeaZ decreased the virulence of V. harveyi in zebrafish. Significance and Impact of the StudyHere, we show clear evidence of a resuscitation-promoting factor YeaZ of V. harveyi and the roles in resuscitation of the VBNC cells and its pathogenicity.