What is paratransgenesis?
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.
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.
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.”
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.”
A very useful
general microbiology site with insect links is:
My name is Al Chan,
and I am the webmaster for Microbes.info located