Lab Members


Principal Investigator

Shelley M. Payne

Shelley Payne

UT-CNS Profile
PubMed Record

Google Scholar Record


B.A. Rice University, 1972
Ph.D. Texas Health Science Center (Dallas), 1977
POSTDOC: University of California at Berkeley

Our studies focus on the genetics and regulation of iron acquisition systems and other virulence factors of Shigella and Vibrio species. The iron transport systems are of interest because the ability of potential pathogens to acquire iron from the host is an important determinant of microbial virulence. Iron is required for growth of bacteria, but little free iron is available in mammalian hosts. Many bacteria have been found to secrete high affinity iron-binding compounds, or siderophores, which may function to remove iron from host proteins and make it available to the microorganism for growth in vivo.

Vibrio species produce a variety of siderophores and iron-regulated outer membrane proteins. In response to iron deprivation, Vibrio cholerae synthesizes a norspermadine containing siderophore, and five cell surface proteins, including receptors for the siderophore and for heme. The Shigella species, a group of enteric pathogens, have at least three distinct iron transport systems. Two of these, the aerobactin and enterobactin systems, consist of siderophores and their associated outer membrane receptor proteins. Expression of these systems is regulated at the level of transcription by the concentration of iron within the cell. A third pathway is required for the transport and utilization of iron in the form of heme. Virulence assays of mutants defective in one or more of these systems suggest that siderophores provide iron in the extracellular environment while heme transport is utilized by Shigella growing intracellularly within epithelial cells. A heme-binding protein is found on the surface of wild-type Shigellae. Although this protein is not required for heme transport, it is required for invasion of intestinal epithelial cells by S. flexneri. The protein allows the bacteria to bind large amounts of heme on the surface of the bacteria and promotes the attachment of the bacteria to the host cells. This protein is encoded on a large 220 kilobase plasmid, and its synthesis is regulated by both temperature and pH. Analysis of regulatory mutants indicates that at least two loci, one chromosomal and one plasmid encoded, are responsible for the regulation of the structural gene for this cell surface protein. Genetic and recombinant DNA techniques are being used to characterize chromosomal and plasmid sequences involved in iron transport and invasion in these enteric pathogens. The genes have been cloned and gene fusions have been constructed to measure the expression of these genes under different environmental conditions. Techniques have been developed also to measure gene expression and synthesis of virulence-associated proteins by S. flexneri growing within host cells. These studies will allow us to determine the molecular mechanisms of iron acquisition and ultimately to assess the roles of these systems in bacterial infections.


Senior Scientists

Alex R. Mey  

Alex MeyPubMed Record
Google Scholar Record


B.A. Biology, University of Texas at Austin, 1994
Ph.D. Molecular Biology, University of Texas at Austin, 2002

I am interested in how V. cholerae senses and responds to environmental signals, and how these signals are integrated into the regulation of virulence gene expression and pathogenesis in the host. My most recent studies have focused on the role of amino acids in the expression of the virulence gene regulator ToxR. Through this work, I have uncovered a previously unknown link between ToxR and the global regulator CsrA, which is involved in controlling various cellular processes including carbon metabolism, quorum sensing, and virulence in response to extracellular signals. By linking environmental sensing to the ToxR regulon, CsrA may effectively act as a switch that controls pathogenesis in response environmental stimuli. We are currently working to understand more completely the role of CsrA in V. cholerae cellular metabolism and virulence.

In my spare time, I enjoy reading, playing piano, baking, hiking, traveling, and spending time with my family.


Research Technicians

Carolyn Fisher  
Carolyn Fisher


B.S. Texas A&M University, Biomedical Science, 1979

In my 10+ years in the Payne lab I have worked on various projects studying both Vibrio cholerae and Shigella flexneri. My current project involves the study of manganese homeostasis in Vibrio cholerae. In addition to research, I help keep the lab running by purchasing supplies and equipment. Outside the lab, I enjoy taking care of my animals which include chickens, a horse, cattle, and two dogs and spending time with family.


Graduate Students

Nick Xerri


B.S. University of Pittsburgh, 2016

In order to establish infection, enteric pathogens must interact with and ultimately establish amongst the resident gut microbiota. However, the interactions that are important to Shigella flexneri in the colon remain largely unknown. For my research, I am interested in examining interspecies interactions between S. flexneri and normal members of our gut microbiota and determining which interactions influence in S. flexneri growth and virulence.

In my spare time I enjoy reading, cooking, and binge-watching travel shows on Netflix.

Camilo Gómez



Google Scholar Profile


B.S. Universidad de los Andes (Bogotá, Colombia), Chemistry, 2014
B.S. Universidad de los Andes (Bogotá, Colombia), Microbiology, 2015
M.S. Universidad de los Andes (Bogotá, Colombia), Biological Sciences, 2017

Most living organisms require iron as an indispensable nutrient to maintain their homeostasis. Vibrio cholerae is not an exception. This bacterium utilizes the FeoABC operon as a system for ferrous iron transport and, although this system is highly spread among bacteria, how it works remains largely unknown. My research in Payne’s lab is focused on the interaction between Feo proteins and the role that they play in iron transport. Besides, I am also interested in the relationship between iron transport, high-order complex formation and nucleotide hydrolysis activity exhibited by Feo.

Outside of lab, my favorite hobbies include cooking, swimming, and reading.



Grace Kago  


B.A. McDaniel College, Biology, 2010
In the Payne lab, I am interested in two broad topics: how Shigella moves around in the host cell, and how Shigella responds to stress in its environment. Once Shigella invades a cell, it actually moves around with the help of the host cell via a mechanism called Actin Based Motility (ABM). The mechanisms are mostly well characterized, but there are a few unknowns. Additionally, upon cell invasion, Shigella (like most pathogens) has the ability to sense and respond to stress in its host environment. I hope to learn some mechanistic details of this response process.
Outside of lab, I love spending time with friends and family, writing about science, and doing outreach around Austin.

Google Scholar Profile

Undergraduate Students

Julian Merville  

ToxS is the partner protein of ToxR, a major regulator of virulence genes in Vibrio cholerae. I
am interested in studying the relationship between ToxS and ToxR, as well as investigating the
mechanism by which CsrA, a global regulatory RNA-binding protein, controls the expression of
this protein pair.

Outside of the lab, I enjoy spending time with friends, running, exploring Austin, and listening to


Joseph Garza  

Microbes have evolved an impressive array of systems designed to solubilize and capture iron
from their environments for metabolism. These include siderophores, low molecular weight
iron-chelating compounds that are secreted into the environment, and cell surface receptors,
proteins in the outer membrane that acquire iron from host complexes. I am interested in
studying the regulation of siderophore and iron uptake systems in Vibrios and their role as
components of the virulence of these bacteria.

Outside of the lab, I love to cook and grill and sharing these moments with friends and family. I
also enjoy exploring the outdoors and reading a book or two.