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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, microbial interactions, gut microbiome, vitamin cross-feeding and biosynthesis


Cobamide analogs and biosynthesis. Cobamides are a family of structurally-related cofactors that includes vitamin B12. Gut microbiomes harbor dense microbial communities with complex cobamide profiles, and the influence of cobamide analogs on community metabolism and structure are beginning to be unraveled. The lab studies cobamide analogs using high resolution mass spectrometry and major goals of the lab are to 1) characterize novel pathways for cobamide biosynthesis, 2) determine how cobamide analogs affect bacterial physiology, 3) define cobamide profiles of diverse samples, and 4) identify mechanisms for vitamin cross-feeding. Ultimately these studies will improve metagenomic predictions of cobamide production in complex communities and will help define the influence of cobamides on microbial interactions.

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


"Cobamide remodeling"
Ma AT*, Kantner DS, Beld J
Chapter 3 in Vitamins & Hormones, 119:43-63, 2022
*corresponding author

"Direct Cobamide Remodeling via Additional Function of Cobamide Biosynthesis Protein CobS from Vibrio cholerae"
Ma AT*, Beld J
J Bacteriol, 203(15):e0017221, 2021
*corresponding author

"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