Prey Phenotypic Changes During Long-Term Exposure to Bdellovibrio bacteriovorus HD100

Abstract

Bdellovibrio bacteriovorus is gram-negative predatory bacteria who prey on other gram-negative bacteria. Once B. bacteriovorus meet their prey bacteria, they penetrate to periplasmic space and digest and absorb cytosolic contents of prey such as proteins, nucleic acids, and lipids. Because of their unique life cycle, many researchers believe these predatory bacteria could be next generation antibiotics. As they digest almost all cell structure when they invade in prey cell, researchers expected to B. bacteriovorus might not causing resistance on their predation. Previously, few researchers tried resistance development in prey cells against to predation, but they reported it is plastic. Thus, in this study, I wanted to try following prey survival and mutation to get predation resistance by exposing prey cells to B. bacteriovorus. Usually, experiments related with B. bacteriovorus were performed no more than 72 hours, which means prey was exposed to predation situation only in 72 hours. To expose prey cells to B. bacteriovorus predation situation in order that I tried a batch and continuous culture. In both methods, prey cells decreased more than 4-log right after exposed to the predators, however, the number of prey cell recovered about 1-log and kept recovered population while predator cells present in media constantly. Interestingly, in continuous culture, the morphology of prey cell on the solid media had changed when they exposed to predator more than 5 days (120 hours). This morphological change of prey cell colonies was kept constantly even after storage in -80℃ or cultured in rich media. From the microscopic image of phase changed colony from continuous culture, they usually showed smaller size compared with wild-type, about 60% of wild-type cell size. Moreover, in RNA-seq, about 250 genes related with the membrane, and flagellar were differentially expressed in phase changed colony compared with wild-type.