Southeastern Microbiology Summit-2014
Joint meeting of Southeastern and Florida ASM Branches
Ponte Vedra, FL, September 2014
Kathryn L. Nawrocki
Emory University, Atlanta GA 30332
I received my B.S. in Microbiology from Michigan State University in
2011 where I studied Neisseria gonorrhoeae. Presently, I am a PhD
student in the Microbiology and Molecular Genetics Program at Emory
University working in the McBride Lab. My current research interests
are understanding the impact of nutrition on Clostridium difficile
colonization and disease progression.
Ethanolamine Utilization in Clostridium difficile
Kathryn L. Nawrocki and Shonna M. McBride
The gastrointestinal (GI) tract is a competitive environment with both host and microflora
vying for nutrients. The ability to utilize nutrients specific to the GI tract can give pathogenic
bacteria an advantage that leads to successful colonization and establishment of disease.
The nutrients required for Clostridium difficile to establish infection within the GI tract remains
unknown. It has been demonstrated in other enteric pathogens that ethanolamine, a
membrane-derived intestinal metabolite, functions both as a signal to initiate production of
virulence factors and provides a growth advantage as a niche nutrient. High rates of intestinal
cell turnover and a diet rich in processed foods can create a GI environment with high
concentrations of ethanolamine. We have investigated the capacity of C. difficile to utilize
ethanolamine and the impact of ethanolamine on virulence factor expression. C. difficile
contains a putative 19 gene ethanolamine utilization (eut) operon which is induced by the
presence of ethanolamine. Through quantitative reverse transcription PCR (qRTPCR)
analysis of eut gene transcription, we determined that 14 of these ethanolamine utilization
genes appear to function as a single transcriptional unit. Using targeted mutagenesis, we
knocked out two ethanolamine utilization genes, eutA and eutG, and identified that this
operon does facilitate the utilization of ethanolamine in C. diffficle. EutA, a predicted ammonia
lyase reactivating factor, is required for the utilization of ethanolamine while EutG, a predicted
alcohol dehydrogenase, is not necessary to utilize ethanolamine in minimal media studies. In
addition, our data suggest that ethanolamine is a primary carbon source for C. difficile and
can be utilized simultaneously with glucose. Moreover, qRTPCR analyses revealed that the
eut operon has another regulatory component in addition to the putative eutV/W twocomponent regulatory system. This additional regulatory component negatively impacts
expression of the eut operon in the absence of ethanolamine. In contrast to other enteric
species studied, ethanolamine doesn’t appear to affect toxin or pilin production in C. difficile.
Our data suggests that while ethanolamine is a viable nutrient source for C. difficile,
ethanolamine does not appear to function as a virulence signal, in contrast to its influence on
other enteric species.