טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentGancz Hanan
SubjectInteractions between the Bacterium Vibrio cholerae
and Chironomids (Non-Biting Midges)
DepartmentDepartment of Biotechnology and Food Engineering
Supervisors Professor Yechezkel Kashi
Professor Meir Broza


Abstract

Vibrio cholerae is the causative agent of cholera. The natural reservoir of these bacteria is referred to as the “aquatic environment”. The finding that points to the chironomids (Chironomidae: Diptera) as a possible natural reservoir of these bacteria in the aquatic environment is the basis of the work described herein. Here it is shown that V. cholerae supernatants lyses the gelatinous matrix of the chironomid egg mass, and inhibits eggs from hatching. The extra-cellular factor responsible for the degradation was purified from V. cholerae, and identified as hemagglutinin/protease (HAP). The substrate found in the egg mass has protein qualities as well as glycan properties. These findings show that HAP plays an important role in the interaction of V. cholerae and chironomid egg masses. In addition, this study contributes to the understanding of V. cholerae dissemination. The theoretical modes of dissemination of the bacteria include direct contact of human sewage with drinking water, seaborne currents, and marine transportation. Herein, evidence is presented that flying, non-biting midges (Diptera; Chironomidae), collected in the air, carry viable bacteria belonging to the non-O1 non-O139 serogroups. In simulated field experiments, the transfer of environmental V. cholerae by adult midges from the aquatic environment into water-pools that did not contain the bacteria previously, was recorded. In laboratory experiments, flying adult midges that emerged from V. cholerae contaminated water transferred the bacteria from one laboratory flask to another. These findings show that aerial transfer by flying chironomids plays a role in the dissemination of V. cholerae in nature.