Exploring and characterizing the sensitivity of Bdellovibrio bacteriovorus against different stressors.

Abstract

Given the increasing concern of antibiotic resistance, scientists have been pushed to look for new and interesting ways to kill bacteria. One area of research focuses on using bacterial predators, such as the Gram-negative predatory bacteria Bdellovibrio bacteriovorus, which has been proposed as a “living antibiotic.” B. bacteriovorus consumes other Gram-negative bacteria, burrowing into the periplasmic space and digesting the prey from the inside before releasing several progeny cells. Using a host-independent mutant, we have exposed B. bacteriovorus to various physiologically relevant stressors, such as temperature and the presence of a model antimicrobial peptide (AMP), used as part of the innate immune response. We first noticed that B. bacteriovorus cultures grown at 37°C become dark yellow after one day of growth, while B. bacteriovorus grown at 30°C remain light yellow even after several days of growth. The dark yellow color is caused by the production of ubiquinone-8 (UQ8), an essential member of the bacterial electron transport chain (ETC).We also found that B. bacteriovorus grown at 37°C has increased sensitivity to the AMP magainin 2 (MAG2). MAG2 kills bacteria by forming pores in bacterial membranes, which will disrupt the bacterial ETC, and lead to the production of reactive oxygen species. We monitored the autofluorescence of B. bacteriovorus during MAG2 treatment and observed an oxidative burst directly after adding MAG2.With the increased production of UQ8, B. bacteriovorus grown at 37°C could have a difference in membrane fluidity, making it easier for MAG2 to insert into the cell membrane, disrupting the ETC and killing the cell. By determining how we can manipulate its stress response, we can engineer B. bacteriovorus to become a true “living antibiotic.”