Dr Melinda Mayer

Senior Researcher

Contact via email

Translational microbiome

My main research interest is studying mechanisms of combating pathogens involved in gut health and food spoilage. My scientific training was originally in Botany, with degrees from the Universities of Bristol and Durham and postdoctoral positions studying plant reactions to infection, the engineering of plant secondary metabolism and the manipulation of plant polyamine levels. Since 2004 I have been working in the Narbad group and my research has focused on searching for novel antimicrobials and mechanisms to control clostridial pathogens.

I am currently investigating the probiotic bacterium Lactobacillus johnsonii FI9785, looking at exopolysaccharide (EPS) biosynthesis and surface proteins, and investigating the effect of variants and mutants on aggregation and adhesion. We are interested in understanding the mechanism of competitive exclusion and whether surface characteristics play a role in the ability of Lactobacillus johnsonii to exclude pathogens in poultry. Recent research has elucidated the structure and function of its EPS layer, studied its ability to reduce colonisation of pathogens and demonstrated its utility as a continuous delivery system for antimicrobials.

I am also building on previous work on the discovery and application of bacteriophages and their cell lytic endolysins for the control of the important human gut pathogen Clostridium difficile, the food poisoning pathogen C. perfringens and the food spoilage organisms C. tyrobutyricum and C. sporogenes. A collaboration with EMBL, Hamburg is allowing us to investigate endolysin structure and use the information to improve enzyme activity, and with a group at INIA, Madrid we are exploring the use of endolysins and bacteriophages to detect and combat Clostridia in cheese.

In addition to my own research I am involved in a variety of projects with students and visiting workers, including the discovery and application of antimicrobials (lantibiotics with Teagasc, nanoparticles with Procarta), probiotic bacteria (IPLA, Asturias) and investigation of bacteria involved in Nigerian fermented cereals (with the University of Lagos).

I am the institute’s Equality and Diversity champion and am also a member of the Athena Swan committee and the EU working group committee.

Key Publications

Dunne, M., Leicht, S., Krichel, B., Mertens, H. D., Thompson, A., Krijgsveld, J., Svergun, D. I., Gomez-Torres, N., Garde, S., Uetrecht, C., Narbad, A., Mayer, M. J., and Meijers, R. (2016) Crystal structure of the CTP1L endolysin reveals how its activity is regulated by a secondary translation product. J Biol Chem 291, 4882-4893

Gervasi, T., Horn, N., Wegmann, U., Dugo, G., Narbad, A., and Mayer, M. J. (2014) Expression and delivery of an endolysin to combat Clostridium perfringens. Applied Microbiology and Biotechnology 98, 2495-2505

Meader, E., Mayer, M. J., Steverding, D., Carding, S. R., and Narbad, A. (2013) Evaluation of bacteriophage therapy to control Clostridium difficile and toxin production in an in vitro human colon model system. Anaerobe 22, 25-30

Hatziioanou, D., Mayer, M. J., Duncan, S. H., Flint, H. J., and Narbad, A. (2013) A representative of the dominant human colonic Firmicutes, Roseburia faecis M72/1, forms a novel bacteriocin-like substance. Anaerobe 23, 5-8

Dertli, E., Colqhoun, I. J.,Gunning, A. P., Bongaerts, R. J., Le Gall, G., Bonev, B. B., Mayer, M. J., and Narbad, A. (2013) Structure and biosynthesis of two exopolysaccharides produced by Lactobacillus johnsonii FI9785. J Biol Chem 288, 31938-31951

Diez-Echave P,Martín-Cabrejas I,Garrido-Mesa J,Langa S,Vezza T,Landete JM,Hidalgo-García L,Algieri F,Mayer MJ,Narbad A,García-Lafuente A,Medina M,Rodríguez-Nogales A,Rodríguez-Cabezas ME,Gálvez J,Arqués JL. (2021)

Probiotic and Functional Properties of Limosilactobacillus reuteri INIA P572.


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Garcia Gutierrez E., O'Connor P. M., Saalbach G., Walsh C. J., Hegarty J. W., Guinane C. M., Mayer M. J., Narbad A., Cotter P. D.. (2020)

First evidence of production of the lantibiotic nisin P

Scientific Reports

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Garcia-Gutierrez E., O'Connor P., Colquhoun I. J., Vior N. M., Rodriguez J. M., Mayer M. J., Cotter P. D., Narbad A.. (2020)

Production of multiple bacteriocins, including the novel bacteriocin gassericin M, by Lactobacillus gasseri LM19, a strain isolated from human milk

Applied Microbiology and Biotechnology

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Garcia Gutierrez E., Walsh C. J., Sayavedra L., Diaz-Calvo T., Thapa D., Ruas-Madiedo P., Mayer M. J., Cotter P. D., Narbad A.. (2020)

Genotypic and phenotypic characterization of fecal Staphylococcus epidermidis isolates suggests plasticity to adapt to different human body sites

Frontiers in Microbiology

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Diaz M., Sayavedra L., Atter A., Mayer M. J., Amoa-Awua W., Narbad A., Saha S.. (2020)

Lactobacillus garii sp. nov., isolated from a fermented cassava product.

International journal of systematic and evolutionary microbiology

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Yu L,Duan H,Kellingray L,Cen S,Tian F,Zhao J,Zhang H,Gall GL,Mayer MJ,Zhai Q,Chen W,Narbad A. (2020)

Lactobacillus plantarum-Mediated Regulation of Dietary Aluminum Induces Changes in the Human Gut Microbiota: an In Vitro Colonic Fermentation Study.

Probiotics and antimicrobial proteins

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Garde S,Calzada J,Sanchez C,Gaya P,Narbad A,Meijers R,Mayer MJ,Avila M. (2020)

Effect of Lactococcus lactis expressing phage endolysin on the late blowing defect of cheese caused by Clostridium tyrobutyricum

International Journal of Food Microbiology

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