Valerie A. Ray – Microbiology and Immunology
Mentor – Dr. Karen L. Visick
Loyola University Medical Center, Maywood, IL
Explanation of project:
My research in the Visick lab at Loyola University Medical Center focuses on
understanding bacteria-host interactions. Specifically, we are interested in how
bacteria transition from living as single cells to living as part of a community, or
biofilm, and how biofilm formation impacts host colonization. Since many diseasecausing bacteria form biofilms, it is important to understand how biofilm formation
is regulated. To do this, I study biofilm formation using a well-characterized model
system, in which the bacterium Vibrio fischeri enters into a symbiotic relationship
with the Hawaiian bobtail squid Euprymna scolopes. During the initial stages of
colonization, biofilm formation by V. fischeri is a critical process. Furthermore, we
know that biofilm formation depends upon a set of genes, syp, predicted to be
involved in the regulation, production, and transport of an important biofilm
component. Since biofilm formation is a tightly regulated process, and is typically
limited to the appropriate conditions, we are particularly interested in how the syp
genes are regulated under different environmental conditions. Currently, we have
evidence to suggest that loss of molecules predicted to be involved in the
biosynthesis of the amino acid cysteine leads to a loss of biofilm formation. One
readily testable hypothesis is that cysteine is required for normal expression of the
syp genes. Thus, to begin to understand how cysteine regulates biofilm formation,
we will start by examining syp gene expression under a variety of different
conditions, and if we observe an effect, we will probe the regulatory level at which
the effect occurs. Overall, understanding how cysteine regulates biofilm formation
will provide insights into the environmental control of biofilm formation by V.
fischeri during colonization of the squid host.
Description of Summer Undergraduate Work:
The project goal is to understand how cysteine regulates biofilm formation. Thus,
the student will begin by examining the impact of cysteine of gene expression
(transcription), focusing on the syp genes, which are known to play a critical role in
biofilm formation. To do this, the student will make use of genetic “reporter” tools
that permit an assessment of transcription using a colorimetric assay called a galactosidase assay. This assay allows us to examine the relative level of
transcription from a syp reporter strain in various V. fischeri mutants (e.g., cysteine
biosynthesis mutants) and under various conditions, such as in the presence or
absence of cysteine. The results of these experiments will dictate future work. With
my help, the student will develop and test specific hypotheses to further understand
the impact of cysteine on biofilm formation. The research will take the following
form: the summer student will spend the first couple of weeks learning the
literature and background for the project as well as learning standard laboratory
practices and, in particular, how to perform the -galactosidase assay. Once
reproducible data have been obtained, additional permutations of the assay may be
completed, such as using additional mutant strains or different amounts of cysteine.
With the results in hand, and with my help, the student will develop specific testable
hypothesis and likely, generate additional particular strains of interest. Possible
experiments include assessing the production of proteins by an immunologic
approach called the Western blot, the generation of other amino acid biosynthesis
mutants, and/or a genetic approach to search for additional members of a genetic
pathway for cysteine-mediated control of biofilm formation. The student should
expect to be in lab ~7-8 hours a day Monday-Friday to generate useful data; the
more you put into lab, the more you get out of it. Overall, the student will gain a
general understanding of standard laboratory practices and importantly, learn how
a scientist follows the results of their data to develop and test specific hypotheses, as
well as how to think critically.