Poster Presentation Australian Microbial Ecology 2019

A wolf in sheep’s clothing: Protozoan expelled food vacuoles are a protective transmission vector for pathogens (#131)

Gustavo Espinoza-Vergara 1 2 , Parisa Noorian 1 2 , Cecilia A Silva 3 , Benjamin A Raymond 1 , Christopher Allen 4 , M Mozammel Hoque 1 , Shuyang Sun 1 , Michael S Johnson 4 , Staffan Kjelleberg 5 , Steven P Djordjevic 1 , Maurizio Labbate 4 , Andrew Camilli 3 , Diane McDougald 1 5
  1. ithree Institute, University Of Technology Sydney, SYDNEY, NSW, Australia
  2. School of Biotechnology and Bimolecular Science, University of New South Wales, Sydney, NSW, Australia
  3. Department of Molecular Biology and Microbiology, Howard Hughes Medical Institute, Tufts University, Boston, MA, USA
  4. School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, Australia
  5. Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore

Vibrio cholerae, the causative agent of the acute diarrheal disease cholera, is an inhabitant of aquatic environments where it interacts with a wide variety of organisms, including heterotrophic protists (protozoa).  Several species of these bacterial predators have been reported to release live, undigested bacteria in expelled food vacuoles (EFVs) when feeding on certain Gram-negative and Gram-positive pathogens.  While the production of EFVs has been reported, their biological role as a vector for the transmission of pathogens remains unknown. Here we report that that protozoa release large numbers of EFVs when feeding on V. cholerae. The EFVs are stable, the bacterial cells within are protected from multiple stresses (low pH, antimicrobials and starvation) and vast numbers quickly escape when incubated at 37°C or in the presence of nutrients. We show that specific genes regulated by ToxR, play a significant role in the production of EFVs. Importantly, cells released from EFVs have a fitness advantage over planktonic cells both in vitro and in vivo and are highly infectious. Thus, results suggest that EFVs facilitate V. cholerae survival in the environment and as they move through the gastric environment, enhancing infectious potential and may significantly contribute to the dissemination of epidemic V. cholerae strains.