IP Resources

What is paratransgenesis?

Paratransgenesis in insects is the genetic alteration of microbes living in association with insects for various purposes. By way of contrast, insect transgenesis is the genetic alteration of insects (putting novel genes into insects). This field has had something of a renaissance recently as new transformation protocols allows this technique to move well beyond Drosophila melanogaster. However, paratransgenesis is a powerful new tool in pest control and insect physiology.

Insect transgenesis requires training and expertise well beyond the casual. Also, genes must be inserted into the chromosome to make them stable and heritable, and sophisticated plasmids must be constructed to achieve this. Progress is inherently slowed by the reproductive cycle of the insect, typically longer than a month.

By contrast, genes can be inserted in a few minutes into bacteria as a part of their normal plasmids (Extrachromosomal) using standard electroporation. The inserted transgenic plasmids will not start to be lost in the host bacterium until at least a month after insertion, depending on conditions and the plasmid. Plasmids are typically lost under stress such as starvation.

Carol Lauzon used plasmid-paratransgenic walnut husk flies, Rhagoletis completa, to study the colonization of the gut by two separate symbiotic bacteria that she found were vital to digestion in cyclorrhaphan Diptera. John Peloquin provided Enterobacter and Klebsiella bacteria labeled with ECFP and DsRed fluorescence respectively.

Peloquin, J. J., C. R. Lauzon, S. Potter and T. A. Miller (2002). Transformed bacterial symbionts re-introduced to and detected in host gut. Current Microbiology 45: 41-45.

Rod Dillon, University of Bath, UK, has been studying the production of phenolic compounds by gut bacteria of locusts and grasshoppers as products most likely of the digestion of secondary plant chemicals. The developing locusts use the phenolics as pheromones and signals to develop to the aggregation phase preparatory to swarming as adults.

Dillon, R. J., C. T. Vennard and A. K. Charnley Pheromones: Exploitation of gut bacteria in the locust. Nature 403: 851 (24 February 2000) “Our results show that locusts have adapted to use a pheromonal component that is derived from its digestive waste products by the action of bacteria acquired serendipitously with its food. The gut bacteria also help the locust to defend itself against microbial pathogens, mainly by producing antimicrobial phenolic compounds.”

Ravi Durvasula, School of Epidemiology & Public Health, Yale University, New Haven, CT is currently exploiting paratransgenesis as a way to control Chaga’s disease in a project pioneered by Frank Richards:

“The focus of Dr. Durvasula's laboratory is development of novel approaches to treatment of human infectious diseases. Using insect-borne Chagas disease as a paradigm, his group has developed a strategy termed paratransgenesis- -the expression of transmission- -blocking molecules in the arthropod host via genetically engineered symbiotic bacteria. Initially, the insect immune peptide, cecropin A, was expressed in the Chagas vector at levels that eliminated the parasite, Trypanosoma cruzi. Subsequently, a marker single chain antibody fragment was expressed and the Durvasula lab is currently expressing single chain antibodies that target key epitopes of T. cruzi. A strategy for spread of genetically altered bacteria amongst field populations of reduviids is being developed in collaboration with CDC groups in Atlanta and Guatemala. Application of the paratransgenic approach to sandfly-transmitted leishmaniasis is another focus of the lab. The Durvasula lab is also pursuing paratransgenic approaches to human respiratory tract infections via engineered human commensal bacteria. Dr. Durvasula also serves as Medical Director of Yale University Health Services.”

[http://info.med.yale.edu/eph/html/faculty_members/durvasula.html]

A very useful general microbiology site with insect links is:

My name is Al Chan, and I am the webmaster for Microbes.info located

at http://www.microbes.info/