Cheryl Andam

Graduate Program Coordinator for Genetics
Phone: (603) 862-1881
Office: Molecular, Cellular, & Biomedical Sciences, Rudman Hall, Durham, NH 03824
Cheryl Andam

My research focuses on microbial population genomics and evolution. I was trained at the University of the Philippines (B.S.), Binghamton University (M.S.), University of Connecticut (Ph.D.), Cornell University (Postdoc) and the Harvard School of Public Health (Postdoc).

Current work in my lab aims to elucidate the evolutionary processes and ecological factors that drive the genomic diversification and adaptation of microbial populations in different environments. We are interested in different bacterial species. We study how different strains of the same species adapt to human hosts, animal hosts and environment. My lab works closely with the New Hampshire Veterinary Diagnostic Laboratory (NHVDL) to study the ecology and evolution of multiple Staphylococcus species and enteric bacteria from pets, livestock and wildlife. We also work with NH state health lab to study the genome dynamics and evolution of bacterial pathogens infecting humans and animals. We study the actinobacterium Streptomyces, which are known as the major source of naturally derived antibiotics and many pharmaceutically relevant compounds (e.g., antifungals, antitumor, antihelmintics, antiprotozoans, immunosuppressants).

Using an inter-disciplinary approach combining next-generation sequencing (genomics), population genetics, phylogenetics and lab-based assays, we examine inter-strain and inter-species variation:

(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?

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 acquisition of genetic material through genetic exchange of similar DNA sequences) are important processes that can lead to extensive genetic diversity in terms of gene content and allelic variation within a species.


  • 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 795W: Investigations
  • BMS 503: General Microbiology
  • BMS 504: General Microbiology Lab
  • BMS 703: Infectious Disease and Health
  • BMS 795W: Investigations Biomedical Sci
  • BMS 799H: Senior Honors Thesis
  • GEN 713/813: Microbial Ecology & Evolution
  • INCO 790: Adv Rsrch Exp/MCBS
  • MCBS 999: Doctoral Thesis

Selected Publications

Belknap, K. C., Park, C. J., Barth, B. M., & Andam, C. P. (2020). Genome mining of biosynthetic and chemotherapeutic gene clusters in Streptomyces bacteria. Scientific Reports, 10(1). doi:10.1038/s41598-020-58904-9

Lee, I. P. A., & Andam, C. P. (2019). Pan-genome diversification and recombination in Cronobacter sakazakii, an opportunistic pathogen in neonates, and insights to its xerotolerant lifestyle. BMC Microbiology, 19(1). doi:10.1186/s12866-019-1664-7

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., . . . Hanage, W. P. (2018). Genomic epidemiology of meticillin-resistant Staphylococcus aureus ST22 widespread in communities of the Gaza Strip, 2009. Eurosurveillance, 23(34). doi:10.2807/

McGill, C. M., Tomco, P. L., Ondrasik, R. M., Belknap, K. C., Dwyer, G. K., Quinlan, D. J., . . . Barth, B. M. (2018). Therapeutic effect of Northern Labrador tea extracts for acute myeloid leukemia. Phytotherapy Research, 32(8), 1636-1641. doi:10.1002/ptr.6091

Andam, C. P., Doroghazi, J. R., Campbell, A. N., Kelly, P. J., Choudoir, M. J., & Buckley, D. H. (2016). A Latitudinal Diversity Gradient in Terrestrial Bacteria of the Genus
Streptomyces. mBio, 7(2). doi:10.1128/mbio.02200-15

Pepe-Ranney, C., Koechli, C., Potrafka, R., Andam, C., Eggleston, E., Garcia-Pichel, F., & Buckley, D. H. (2016). Non-cyanobacterial diazotrophs mediate dinitrogen fixation in biological soil crusts during early crust formation. The ISME Journal, 10(2), 287-298. doi:10.1038/ismej.2015.106

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

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