E. Fidelma Boyd, Ph.D.


BISC 682 Molecular Mechanisms of Pathogens
BISC 850 Advanced Topics in Microbiology

Research Interests

Vibrio parahaemolyticus an emerging human pathogen
Vibrio parahaemolyticus is the leading cause of bacterial seafood borne gastroenteritis worldwide. One of our questions is to determine the factors that aided the emergence of the pandemic O3:K6 serogroup hypervirulence clone. This new variant contains several pathogenicity islands that are absent from non pathogenic strains (Hurley et al., 2006, Boyd et al., 2008; Kalburge et al., 2014).Our group developed a new in vivo adult mouse model for V. parahaemolyticus colonization that allows us for the first time to determine the bacterial factors required for host colonization. Using this model we identified a number of global regulators important for in vivo survival (Whitaker et al., 2012, 2014, Haines-Menges et al, 2014). We determind that the Vibrio specifc ToxRS regulator is essential for colonization through its regulation of the porin OmpU and its role in stress tolerance (Whitaker et al., 2012). Similarly, the cell envelope stress response sigma factor RpoE is essential for in vivo survival (Haines-Menges et al., 2014). Our examination of mutants deficient in the sigma factors RpoN, FliAP or FliAL showed that they were superior colonizer compared to the wild-type strain. The superior colonization phenotype appears to be due to a faster growth rate on intestinal mucus as well as individual components of mucus (Whitaker, et al., 2014). More recent studies show that bacterial communication affects cell metabolism that is important for in in vivo fitness. This work demonstrates that quorum sensing regulation is required for in vivo colonization (Kalburge and Boyd, 2015). 

Vibrio parahaemolyticus is a halophile and salt is an absolute requirement for growth. How this species is adapted to high salt tolerance  whereas sister species are not is unclear.  We identified in the genome several osmotolerance systems including two compatible solute synthesis systems ectoine and glycine betaine (Boyd et al., 2008; Naughton et al., 2009). Our data show that growth at moderate and high salinity compared to low salinity protects at low pH (Whitaker et al., 2010; Kalburge et al., 2014).  We demonstrated that only the ectoine synthesis system but not the glycine betaine synthesis system is essential for fitness and survival at high salinity under low nutrient conditions (Ongagna-Yhombi and Boyd, 2013).  Of the four different BCCT compatible solute transporters present in V. parahaemolyticus, we have shwon that VC1456 has the most diverse substrate range (Ongagna-Yhombi, McDonald, and Boyd., 2015). Our more recent work indicates that the ectone and betaine synthesis systems are under different regulatory control.

Vibrio cholerae, the causative agent of the dreaded diarrheal disease cholera

For cholera infection, two virulence factors are indispensable; cholera toxin and the toxin corregulated pilus, and both are encoded on mobile and integrative gentic elements (MIGEs); the filamentous phage CTXphi and the TCP island or Vibrio Pathogenicity Island (VPI), respectively. My group identified a second pathogenicity island named VPI-2, which is present among all pathogenic isolates (Jermyn and Boyd, 2002, 2005). VPI-2 encodes the genes required for sialic acid scavenaging (nanH), uptake (siaPQM) and catabolism (nanA, nanEK, nagA) (Jermyn and Boyd, 2002, 2005, Almagro-Moreno and Boyd, 2009a). Sialidase encoded by nanH cleaves terminal sialic acid, a nine carbon backbone monosaccharide present on all cell surfaces, from cell surface glycans. In the intestinal mucin, sialidase converts host sialoglycans to GM1 gangliosides, the cell receptors for CT, with the release of free sialic acid that can be taken up and catabolized as a sole carbon and nitrogen source by V. cholerae (Almagro-Moreno and Boyd, 2009a). We demonstrated that the TRAP transporter SiaPQM (VC1777-VC1779) is the sole sialic acid transporter present in V. cholerae (Chowdhury et al., 2012). One of our research goals is to demonstrate that host specific nutrients such as sialic acids are essential for V. cholerae growth and survival in vivo (McDonald et al., in review).

Pathogenicity islands are large chromosomal regions acquired by a pathogenic strains within a species. We are examining the mechanisms of excision and integration of VPI-1 and VPI-2 and the role of island-encoded and host-encoded factors play in these functions. We demonstrated that VPI-2 can excise from the genome and a form circular intermediate and this is catalyzed by an integrase and excisionase encoded within VPI-2 (Murphy and Boyd, 2008; Almagro-Moreno et al., 2010).  Our data suggests that there is cross talk between different islands in V. cholerae and this communication is mediated by RDFs/excisionases (Carpenter and Boyd, In Review).

Vibrio vulnificus a marine bacterium and opportunistic pathogen of humans

Vibrio vulnificus is a highly invasive pathogen of both fish and humans.V. vulnificus population genetic structure consists of at least two major lineages containing unique regions required for survival within its varied niches (Cohen et al., 2007).  We are using molecular genetic and genomic approaches to determine the key elements that allow the organism to survive in molluscs, fish and humans.  We have identified in the genome a large number of regions unique to each sequenced strain (Quirke et al., 2006).  One such region is region XII, a 33 kb cluster that encodes genes for the transport and metabolism of glycoaminoglycans (GAGs).  GAGs can potentially be used by the bacterium as a carbon and nitrogen source and may explain the highly invasive nature of this species. 

V. vulnificus can both catabolize and synthesize sialic acid.  Only clinical isolates can catabolize sialic acid and these isolates encode a single transporter for sialic acid uptake similar to that found in V. cholerae (Lubin et al, 2012). All isolates appear to be capable of sialic acid biosynthesis.  The two sequenced strains of V. vulnificus encode highly divergent sialic acid biosynthesis neu/nab genes and we have shown that the two strains produce different amounts of sialic acid (Lewis et al., 2011).  Also it appears that V. vulnificus can synthesize different types of sialic acid (Lewis et al., 2011). Our more recent studies have shown that decoration of the bacterial surface promotes bloodstream survival of this species (Lubin et al., 2015). We are investigating the type of sialic acid produced by V. vulnificus and the surface structure(s) that is decorated with this compound (McDonald, N. unpublished data).

Research Group

Joe Borowski, B.S., -M.S. Graduate student program, (B.S. University of Delaware), Mobile elements

Megan R. Carpenter, B.S., -Ph.D./M.B.A. Graduate student program, (B.S. Lafayette College, PA), Vibrio pathogenicity Island excision and integration in Vibrio cholerae

Gwendolyn Gregory, B.S., -M.S. Graduate student program, (B.S.), Vibrio evolution and ecology

Sai Siddarth Kalburge, B.S. -Ph.D/M.B.A. Graduate student program, (B.S. Viswesvaraya Technological University, India), Vibrio parahaemolyticus stress responses.

Nathan McDonald, B.S., Ph.D./M.B.A. Graduate student in Chemistry Biology Interface Program, (B.S. University of Delaware).  Vibrio physiology and metabolism

Abish Regmi, B.S.Ph.D./M.B.A. Graduate student (B.S. Towson State University).  Vibrio parahaemolyticus metabolic fitness

Maria Limmina, Undergraduate Researcher, University of Delaware

Selected Publications

1.   Kalburge, S.S., A. Regmi, Whitaker, W.B., and E.F. Boyd. 2015. Carbon utilization patterns govern in vivo fitness in Vibrio parahaemolyticus. In Preparation.

2.   McDonald, N.D., J.B. Lubin, N.Chowdhury, and E.F. Boyd.  2015. Host-derived sialic acids are an important nutrient source that increases bacterial fitness in vivo.  In Revision.

3. Carpenter, M.R. and E.F. Boyd. 2015. Pathogenicity island cross-talk mediated by recombination directionality factors can facilitate excision and spread of virulence genes in bacteria. J. Bacteriol. In Press.    

4.   Kalburge, S.S. and E.F. Boyd. 2015. Role of quorum sensing in Vibrio parahaemolyticus intestinal colonization. In Revision.

5.   Lubin, J.B., W.G. Lewis, N.M Gilbert, S. Almagro-Moreno, E.F. Boyd, and A.L. Lewis. 2015. Host-like carbohydrates promote bloodstream survival of Vibrio vulnificus in vivo. Infection and Immunity. 10.1128/IAI.00345-15.

6. Boyd, E.F., M.R. Carpenter, N. Chowdhury, A.L. Cohen, B.L. Haines-Menges, J.J. Kingston, S. S. Kalburge, J.B. Lubin, S.Y. Ongagna-Yhombi, and W.B. Whitaker. 2015. Postgenomic analysis of the evolutionary history of Vibrio.  Microbiology Spectrum, In Press.

7.   Ongagna-Yhombi, S.Y., N.D. McDonald, and E.F. Boyd. 2015. Deciphering the role of multiple betaine choline carnitine transporters in the halophile Vibrio parahaemolyticus. Applied and Environmental Microbiology, 81(1):351-63.

8.   Haines-Menges, B.L., Whitaker, W.B., J.B. Lubin, and E.F. Boyd. 2015. Host Sialic Acids: A delicacy for the pathogen with discerning taste. In Metabolism and Bacterial Virulence. Edited T. Conway and P. Cohen, ASM Press. Microbiology Spectrum.

9.   Haines-Menges, B.L., Whitaker, W.B., and E.F. Boyd. 2014. The alternative sigma factor RpoE is essential for Vibrio parahaemolyticus cell envelope stress response and intestinal colonization. Infection and Immunity, 82:3667-77.

10.   Chowdhury, N., J.J. Kingston, W.B. Whitaker, M.R. Carpenter, A.L. Cohen, and E.F. Boyd. 2014. Sequence and expression divergence in an ancient gene duplication of the chaperonins groELgroES in Vibrio species. Microbiology 160:1953-63. 

11. Katz LS, Turnsek M, Kahler A, Hill VR, Boyd EF, Tarr CL. 2014. Draft Genome sequence of environmental Vibrio cholerae 2012EL-1759 with similarities to the V. cholerae O1 classical biotype.  Genome Announc. 2014 Jul 10;2(4).

12. Kalburge, S.S., S. Polson, K. Boyd Crotty, L. Katz, M. Turnsek, C.L. Tarr, J. Martinez-Urtaza, and E.F. Boyd. 2014. Complete genome sequence of Vibrio parahaemolyticus UCM V493. Genome Announcements, 13;2(2).

13. Kalburge, S.S., Whitaker, W.B., and E.F. Boyd. 2014. High salt pre-adaptation of Vibrio parahaemolyticus enhances survival to lethal environmental stresses. J. Food Protection, 77(2):246-53.

14. Richards, G.P, M.A. Watson, E.F. Boyd, W. Burkhardt III, R. Lau, J. Uknalis and J. Fay. 2014. Seasonal levels of the Vibrio predator Bacteriovorax in Atlantic, Pacific and Gulf Coast Seawater. International Journal of Microbiology, 2013:375371.

15. Whitaker, W.B., G.P. Richards, and E.F. Boyd. 2014. Loss of the sigma factor RpoN increases intestinal colonization proficiency of Vibrio parahaemolyticus in an adult mouse model. Infection and Immunity, 82:544-556.


Phone: (302) 831-1088

Fax: (302) 831-2281

Email: fboyd@udel.edu

Office: 328 Wolf Hall

Lab: 353 Wolf Hall

Department of Biological Sciences
Wolf Hall
University of Delaware
Newark, DE 19716


  • B.S., Ph.D. - National University of Ireland (Galway, Ireland)
  • Postdoctoral - The Pennsylvania State University
  • Postdoctoral - Harvard University
  • Postdoctoral - Tufts University School of Medicine