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Courses Taught

• Career Pathways
• Life on Planet Earth 

Research Interests

My research focuses on microbial ecology of aquatic ecosystems with emphasis on bacterial ecology of streams. Present projects in my laboratory include: Our lab focuses on examining responses of microorganisms to their environment. Examples of recent projects in the lab include: 

• Connecting microbial community structure and function
• Microbial communities of acid mine impacted streams and changes in the community associated with remediation
• Effects of dissolved organic matter on denitrification in agricultural streams
• Leaf decomposition in wetlands, streams and terrestrial systems
• Response of bacteria to nutrients and carbon
• Impacts of urbanization on bacterial community composition and antibiotic resistance

In each project, we use a variety of molecular biology techniques and microscopy to examine properties such as bacterial and fungal community structure, gene expression, diversity of denitrification genes, etc.  We seek to integrate the fields of microbiology and ecology.

Scholarly, Creative & Professional Activities

Current and past funding from NSF, NASA, EPA, and other agencies/foundations

Editor, Applied and Environmental Microbiology (2001-2011)

Editorial Boards, Applied and Environmental Microbiology (1997-1999, 1999-2001), Microbial Ecology (2001-2017), The International Society of Microbial Ecology Journal (2006-2018)

Recent Publications

1. Akins, L., Ortiz, J., & Leff, L. G. (2020). Strain-specific responses of toxic and non-toxic Microcystis aeruginosa to exudates of heterotrophic bacteria. Hydrobiologia, 847(1), 75-89.
2. Van Gray, J. B., Roberto, A. A., & Leff, L. G. (2020). Acute salt stress promotes altered assembly dynamics of nascent freshwater microbial biofilms. Hydrobiologia, 847(11), 2465-2484.
3. Ayayee, P. A., Taura, J., Roberto, A. A., Blackwood, C. B., & Leff, L. G. (2020). Patterns of Denitrification and Methanogenesis Rates from Vernal Pools in a Temperate Forest Driven by Seasonal, Microbial Functional Gene Abundances, and Soil Chemistry. Wetlands, 1-11.
4. Hossain, M. R., Jiang, M., Wei, Q., & Leff, L. G. (2019). Microplastic surface properties affect bacterial colonization in freshwater. Journal of basic microbiology, 59(1), 54-61.
5. Leff, L. G. (2019). Microbial Ecology of Streams. Encyclopedia of Water: Science, Technology, and Society, 1-13.
6. Roberto, A. A., Van Gray, J. B., Engohang-Ndong, J., & Leff, L. G. (2019). Distribution and co-occurrence of antibiotic and metal resistance genes in biofilms of an anthropogenically impacted stream. Science of the total environment, 688, 437-449.
7. Akins, L., P. Ayayee and L. G. Leff.  2018. Composition and Diversity of Cyanobacteria-Associated and Free-Living Bacterial Communities During Cyanobacterial Blooms.  Annals of Microbiology, 68:493-503.
8. Ayayee, P., C. Cosgrove, A. Roberto, A. Beckwith, and L. G. Leff. 2018. Gut bacterial assemblages of freshwater macroinvertebrate functional feeding groups, Hydrobiologia, 822:157-172.
9. Leff, L. G. 2018.  Freshwater Habitats in Encyclopedia of Microbiology, 4e, accepted.
10. Lu, X., D. L. Bade, L. G. Leff. and X. Mou. 2018. The Relative Importance of Anammox and Denitrification to Total N2 Production in Lake Erie.  Journal of Great Lakes Research. 822:157-172.
11. Roberto, A., J. Van Gray and L.G. Leff. 2018. Sediment bacteria in an urban stream: Spatiotemporal patterns in community composition, Water Research, 134: 353-369.
12. Van Gray, J and L. G. Leff.  2018. Impacts of varying durations of passive oxygen exposure on freshwater denitrifier community structure and function, Aquatic Ecology, 52: 35–49.
13. Leff, L. G. 2018. Microbial Ecology of Streams. Encyclopedia of Water: Science, Technology, and Society. Wiley.
14. Ghosh, S., P. Ayayee, Oscar J. Valverde-Barrantes; Christopher Blackwood; Todd V. Royer; Laura G. Leff. 2017, Initial nitrogen enrichment conditions determines variations in nitrogen substrate utilization by heterotrophic bacterial isolates.  BMC Microbiology 17:87 DOI 10.1186/s12866-017-0993-7
15. Brower, S. L. G. Leff and X. Mou. 2017. Effects of Short and Long-Term Hydrological Regimes on the Composition and Function of Denitrifying Bacteria in Experimental Wetlands. Wetlands, 37:573-583.
16. Ghosh, S. P. Ayayee, and L. G Leff. 2016.  Response of sediment bacterial communities to temporal variation in the dissolved organic matter pool of an agriculturally impacted stream. Fundamental and Applied Limnology, 188:171-185
17. Johnston, G. P, D. Lineman, C. G. Johnston, and L. G. Leff. 2015.  Characterization, sources and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in long-term contaminated riverbank sediments.  Environmental Earth Sciences.  74:3519-3529.