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Amy T. Ma

Amy T. Ma, PhD

Assistant Professor

Department: Microbiology & Immunology


  • PhD in Microbiology and Molecular Genetics - Harvard Medical School
  • Life Science Research Foundation Postdoctoral Fellow, supported by the Howard Hughes Medical Institute – University of California, San Diego

Amy T. Ma, PhD, is an assistant professor in the Department of Microbiology & Immunology at Drexel University College of Medicine. She received her PhD from the Microbiology and Molecular Genetics Department at Harvard Medical School, and was a Life Sciences Research Foundation postdoctoral fellow at the University of California, San Diego.

Research Overview

Dr. Ma’s research combines classic bacteriology with analytical chemistry methods to characterize microbial interactions and bacterial cell biology. There are open projects for highly motivated undergraduate, master's and graduate students interested in microbiology research.

Research Interests

Bacteriology, protozoan grazers, microbial interactions, vitamin biosynthesis and utilization


Microbial interactions between protozoan grazers and bacteria. Protozoan grazers are unicellular eukaryotes that subsist by consuming microbial prey, playing a vital role in nutrient cycling within food webs. Amoebae are a polyphyletic group of protozoan grazers that ingest prey through phagocytosis. Many amoebae are bacterivores, and characterizing the long-standing interactions between predatory eukaryotes and their bacterial prey provides insight into bacterial strategies for combatting them. We are currently studying the interactions between model amoebal species (Dictyostelium discoideum and Acanthamoeba castellanii) and natural amoebal isolates with their bacterial prey, including cyanobacteria, heterotrophic bacteria, and pathogenic bacteria.

Natural amoebal isolates
Natural amoebal isolates

Corrinoid biosynthesis, specificity and utilization. Corrinoids are a family of compounds that include vitamin B12. These compounds are only produced by some prokaryotes, but are required by a range of organisms including humans. Interestingly, different corrinoid variants are produced by different bacteria. We are currently examining biosynthetic pathways for making alternate variants and for remodeling corrinoids to different variants. We are also characterizing the specificity of corrinoid-dependent enzymes for different variants and defining how organisms utilize corrinoids in support of specialized metabolic pathways.

Vitamin B12, variable upper and lower ligands shown in red
Vitamin B12, variable upper and lower ligands

In the Media


"Specificity of cobamide remodeling, uptake and utilization in Vibrio cholerae
Ma AT*, Tyrell B, Beld J
Mol Microbiol, 113(1):89-102, 2020
*corresponding author 

"An amoebal grazer of cyanobacteria requires cobalamin produced by heterotrophic bacteria"
Ma AT*, Beld J, Brahamsha B
Appl Environ Microbiol, 83:e00035-17 (spotlighted article), 2017
*corresponding author

"Isolation of diverse amoebal grazers of freshwater cyanobacteria for the development of model systems to study predator-prey interactions"
Ma AT, Daniels EF, Gulizia N, Brahamsha B
Algal Research, 13:85-93, 2016

"Regulation of Gene Expression in Diverse Cyanobacterial Species Using Theophylline-Responsive Riboswitches"
Ma AT, Schmidt CM, Golden JW
Appl Environ Microbiol, 80(21):6704-13 (cover) 2014

"In vivo actin cross-linking induced by Vibrio cholerae type VI secretion system is associated with intestinal inflammation"
Ma AT and Mekalanos JJ
Proc Natl Acad Sci, 107(9):4365-70, 2010

"Translocation of a Vibrio cholerae type VI secretion effector requires bacterial endocytosis by host cells"
Ma AT, McAuley S, Pukatzki S, Mekalanos JJ
Cell Host Microbe, 5(3):234-43, 2009

"Type VI secretion system translocates a phage tail spike-like protein into target cells where it cross-links actin"
Pukatzki S, Ma AT, Revel AT, Sturtevant D, Mekalanos JJ
Proc Natl Acad Sci, 104(39):15508-13, 2007

"Identification of a conserved bacterial protein secretion system in Vibrio cholerae using the Dictyostelium host model system"
Pukatzki S, Ma AT, Sturtevant D, Krastins B, Sarracino D, Nelson WC, Heidelberg JF, Mekalanos JJ
Proc Natl Acad Sci, 103(5):1528-33, 2006


"B12 Production and Utilization in Microbes"
Invited speaker, Department of Biological Sciences Seminar, University of the Sciences, Philadelphia, Pennsylvania, February 2018

"Amoebal Grazers of Cyanobacteria"
Invited speaker,Asia-Oceania Algae Innovation Summit, Wuhan, China, September 2016

"Corrinoids in Microbial Interkingdom Cross-feeding and Bacterial Physiology"
Poster presentation, 2016 International Symposium on Molecular Medicine & Infectious Disease, Drexel University College of Medicine, Philadelphia, Pennsylvania, September 2016

"Examination of Cyanobacterial-Amoebal Interactions"
Poster presentation, American Society of Microbiology General Meeting, New Orleans, Louisiana, May 2015

"Development of Cyanobacteria for Biotechnological Applications"
Invited speaker, Department of Biological Science Seminar, California State University, Fullerton, October 2013

Contact Information

Department of Microbiology & Immunology
245 N. 15th Street
Philadelphia, PA 19102
Phone: 215.762.8129
Fax: 215.762.1003