Cheryl P. Andam

Assistant Professor
Phone: (603) 862-1881
Office: Molecular, Cellular, & Biomedical Sciences, Rudman Hall, Durham, NH 03824

Postdoc, Harvard School of Public Health
Postdoc, Cornell University
PhD, University of Connecticut
MS, Binghamton University, State University of New York
BS, University of the Philippines

General areas of interest: Microbial population genomics; horizontal gene transfer and recombination; ecology; adaptation; antibiotic resistance

Overall goal: Current work in my lab aims to elucidate the evolutionary processes and ecological factors that drive the diversification and adaptation of microorganisms in different environments. Specifically, we study the genomic differences between strains and species, with implications to the evolution of antibiotic resistance, emergence of virulent lineages, host adaptation, gene flow, geographical distribution and spread. Using an inter-disciplinary approach combining next-generation sequencing (genomics), population genetics, phylogenetics and lab-based assays, we ask the questions:
(1) How extensive are the genomic differences within a species? How did they arise and to which extent are they neutral or adaptive?
(2) How do perturbations, such as antibiotic use or environmental change, alter the genomic diversity and population structure of microbes? 
(3) What is the genetic basis of host adaptation and host switching?
(4) How is resistance maintained and distributed in bacterial populations, and what are the mechanisms that promote the emergence and dissemination of super-fit multidrug resistant clones?
(5) How can we use genomic data to identify co-circulating, independent transmission chains and unsuspected “cryptic” transmission events?

We study different species of bacterial pathogens. My lab works closely with the New Hampshire Veterinary Diagnostic Laboratory (NHVDL) to study the emergence of antibiotic resistance in multiple Staphylococcus species and enteric bacteria from pets, livestock and wildlife. We also work with NH state health and agriculture agencies to study the genome dynamics and evolution of bacterial pathogens such as Salmonella enterica, Campylobacter jejuni and Staphylococcus aureus infecting humans and animals. We also use publicly available genomes to further explore the nature of microbial species and the different evolutionary processes that contribute to their diversification and adaptation.

Within-species variation: Bacterial and archaeal populations are remarkably heterogeneous. They may be clonal, but microbial populations are often composed of multiple co-circulating lineages distinguished by phenotypic and genetic differences, the latter originating from both allelic variation and gene content variation. While puzzling, within-species heterogeneity in microbes is not uncommon, but the underlying factors that drive this variation remain unclear. We are interested in understanding the processes that contribute to the generation and maintenance of this variation within a species. To address this, we study "populations of genomes" that represent clusters of close relatives within and between environments or hosts.

Horizontal gene transfer (HGT) and recombination: The acquisition of genetic material between two organisms that do not share a direct ancestor-descendant relationship is an important mechanism that contributes to the rapid creation of biological novelty that otherwise might have taken millions of years to occur. This is particularly pervasive across microbial lineages, creating phenotypic and genetic variation that can take bewilderingly complex forms even between closely related lineages. HGT enables organisms to acquire pre-existing adaptive characters from other organisms, regardless of phylogenetic distance. Thus, instead of genetic traits within lineages always emerging gradually through successive mutations and selection, evolution is accelerated as a parallel process, where inventions made in different lineages can come together in a single cell through HGT. In microbial populations, HGT and recombination (the


  • Ph.D., Microbiology, University of Connecticut
  • M.S., Biology/Biological Sciences, State University of New York at Binghamton
  • B.S., Forestry, University of The Phillipines

Research Interests

  • Drug Resistance
  • Ecology and Population
  • Evolution
  • Genomics
  • Infectious Diseases/Agents
  • Microbiology

Courses Taught

  • BMCB 795: Investigations
  • BMS 703: Infectious Disease and Health
  • BMS 795: Investigations Biomedical Sci
  • BMS 799: Senior Thesis
  • GEN 713: Microbial Ecology & Evolution
  • GEN 795: Investigations in Genetics
  • INCO 790: Adv Rsrch Exp/MCBS
  • MESB 999: Doctoral Research

Selected Publications

Smith, M. M., Park, C. J., Andam, C. P., & Aber, J. D. (2018). Utilization of Low Grade Wood for Use as Animal Bedding: A Case Study of Eastern Hemlock. JOURNAL OF FORESTRY, 116(6), 520-528. doi:10.1093/jofore/fvy040

Chang, Q., Abuelaish, I., Biber, A., Jaber, H., Callendrello, A., Andam, C. P., . . . Grp, P. I. C. R. S. (2018). Genomic epidemiology of meticillin-resistant Staphylococcus aureus ST22 widespread in communities of the Gaza Strip, 2009. EUROSURVEILLANCE, 23(34), 15-23. doi:10.2807/1560-7917.ES.2018.23.34.17-00592

Chang, Q., Abuelaish, I., Biber, A., Jaber, H., Callendrello, A., Andam, C. P., . . . On Behalf Of The Picr Study Group. (2018). Genomic epidemiology of meticillin-resistant Staphylococcus aureus ST22 widespread in communities of the Gaza Strip, 2009.. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin, 23(34). doi:10.2807/

Choudoir, M. J., Panke-Buisse, K., Andam, C. P., & Buckley, D. H. (2017). Genome Surfing As Driver of Microbial Genomic Diversity. Trends in Microbiology, 25(8), 624-636. doi:10.1016/j.tim.2017.02.006

Chaguza, C., Cornick, J. E., Andam, C. P., Gladstone, R. A., Alaerts, M., Musicha, P., . . . Everett, D. B. (2017). Population genetic structure, antibiotic resistance, capsule switching and evolution of invasive pneumococci before conjugate vaccination in Malawi. Vaccine, 35(35), 4594-4602. doi:10.1016/j.vaccine.2017.07.009

Andam, C. P., Fournier, G. P., & Gogarten, J. P. (2011). Multilevel populations and the evolution of antibiotic resistance through horizontal gene transfer. FEMS Microbiology Reviews, 35(5), 756-767. doi:10.1111/j.1574-6976.2011.00274.x

Andam, C. P., & Gogarten, J. P. (2011). Biased gene transfer in microbial evolution. Nature Reviews Microbiology, 9(7), 543-555. doi:10.1038/nrmicro2593

Williams, D., Fournier, G. P., Lapierre, P., Swithers, K. S., Green, A. G., Andam, C. P., & Gogarten, J. P. (2011). A Rooted Net of Life. Biology Direct, 6(1), 45. doi:10.1186/1745-6150-6-45

Andam, C. P., Williams, D., & Gogarten, J. P. (2010). Biased gene transfer mimics patterns created through shared ancestry. Proceedings of the National Academy of Sciences, 107(23), 10679-10684. doi:10.1073/pnas.1001418107

Andam, C. P., Mondo, S. J., & Parker, M. A. (2007). Monophyly of nodA and nifH Genes across Texan and Costa Rican Populations of Cupriavidus Nodule Symbionts. Applied and Environmental Microbiology, 73(14), 4686-4690. doi:10.1128/AEM.00160-07

Most Cited Publications