Dr. Denis Lynn
Professor

Dr. Denis Lynn

Email: ddr@uoguelph.ca

Office: SCIE 1457
Ext: 52746
Lab: SCIE 1403/1404
Ext: 58381

Profile

Dr. Lynn began his career as an undergraduate student majoring in Honours Marine Biology at the University of Guelph. He was interested and inspired to study ciliates by the late Dr. Jacques Berger, University of Toronto, with whom he studied the endosymbiotic ciliates in the intestines of sea urchins. In this early work, he redescribed the large philasterine carnivores, Plagiopyliella and Thyrophylax, using protargol staining. Dr. Lynn’s doctoral research examined the variations in cortical ultrastructure and kinetids of colpodean ciliates. This work lead to his proposal of the structural conservatism hypothesis, which argued that the cortical ultrastructural components were more highly conserved than “higher order” structures and that these cortical structures should provide a stronger phylogenetic signal for relationships. Applying this principle, Dr. Lynn and Dr. Eugene B. Small, University of Maryland, proposed a revised ciliate macrosystem, which recognized a number of new classes of ciliates based primarily on the ultrastructure of the microtubules associated with somatic basal bodies or kinetosomes. Since the mid-1980’s, Dr. Lynn’s laboratory has been testing this proposed macrosystem using the sequences of the small subunit rRNA gene. Dr. Lynn and his students have also published research on the ecology of marine, freshwater, and terrestrial ciliates and have described a number of new species using their quantitative protargol staining procedure. Dr. Lynn is currently Editor-in-Chief of The Journal of Eukaryotic Microbiology.

Education

B.Sc. - Guelph 1969
Ph.D. - Toronto 1975

Research

My research program is broadly focused on the biology of ciliated protozoa. I am interested in a variety of aspects of their biology, from explaining how they function as unicellular organisms to exploring their role in a variety of ecosystems to describing their adaptive diversity and evolution. Research questions in my lab are generally carried out under the two major topics below, providing flexibility to students to choose a research question of interest to them.

Ecology of ciliated protozoa

Ciliates are the most conspicuous unicellular organisms in a variety of microbial ecosystems. They are found from the poles to the equator, in sea ice and in hot springs, in desert soils and tropical forest litter, and in small temporary ponds to the major oceans. Our research has developed quantitative cytological procedures for sampling the diversity of ciliates in aquatic and terrestrial ecosystems. We have explored the diversity and abundance of ciliates in temperate and tropical marine ecosystems and in temperate and tropical freshwater ecosystems. This research has demonstrated their significant role as links in the flow of energy in these ecosystems. Current research is focusing on factors that control ciliate biodiversity in temperate and tropical soils. Many ciliates feed upon bacterial populations, which are the major mineralizers of organic matter in these ecosystems. We are addressing such questions as how is ciliate biodiversity influenced:

  1. by the diversity of these prey bacterial populations;
  2. by the complex organic exudates that might vary among plant root system microhabitats; and
  3. by variations in temperature, moisture and other physicochemical parameters of the soil matrix?

Biodiversity and phylogeny of ciliated protozoa

Our ecological research depends upon our ability to recognize ciliate diversity. We are able to do this using a variety of techniques and instruments - from cytological stains and light microscopes to gene sequences and computer-constructed phylogenies of molecules. Our research has resulted in a revision of the major lines of evolution in the Phylum Ciliophora. This has relied on data provided by light microscopy, electron microscopy, and gene sequences. We are currently directing our research in molecular phylogenetics along three themes:

  1. resolving relationships among ecologically significant groups of ciliates;
  2. exploring the origin and relationships of parasitic and other symbiotic species; and
  3. discovering genes that may enable identification of species without the need for cytological staining.

However, descriptions of cell morphology will continue to be the benchmark requirement for establishing new species. We have described over 30 new species of ciliates from various aquatic ecosystems. There is still much left to learn about the absolute magnitude of the global diversity of ciliates and how loss and change of habitat may influence this diversity.

Selected Publications

Lynn, D.H., Small, E.B. 2002. Phylum Ciliophora. In: An Illustrated Guide to the Protozoa. Lee, J.J., Bradbury, P.C.,Leedale, G.F. (eds.). Society of Protozoologists, Lawrence, Kansas. Pp. 371-656

Acosta, D., Lynn, D.H. 2002. A preliminary assessment of spatial patterns of soil ciliate diversity in two subtropical forests in Puerto Rico and its implications for designing an appropriate sampling approach. Soil Biol. Biochem. 34:125-128.

Yasindi, A.W., Lynn, D.H., Taylor, W.D. 2002. Ciliated protozoa in Lake Nakuru, a shallow alkaline-saline lake in Kenya: Seasonal variation, estimated production, and role in the food web. Arch. Hydrobiol. 154:311-325.

Strueder-Kypke, M., Wright, A.-D.G., Jerome, C.A., Lynn, D.H. 2001. Parallel evolution of histophagy in ciliates of the genus Tetrahymena. BMC Evol. Biol., 5:1. [http://www.biomedcentral.com/1471-2148/1/5]

Strueder-Kypke, M.C., Wright, A.-D.G., Fokin, S.I., Lynn, D.H. 2000. Phylogenetic relationships of the subclass Peniculia Oligohymenophorea, Ciliophora inferred from small subunit rRNA gene sequences. J. Eukaryot. Microbiol. 47:419-429.

Lynn, D.H., Munawar, M. 1999. Abundance, biomass, and diversity of planktonic ciliates Ciliophora in Lake Erie. In Munawar, M., Edsall, T., Munawar, I.F. (eds,) State of Lake Erie (SOLE) - Past, Present and Future. Ecovision World Monograph Series, Leiden. Pp. 155-168.

Dale, T., Lynn, D.H. 1998. Stomatogenesis of the ciliate genus Strombidinopsis with an improved description of S. spiniferum and S. acuminatum. J. Euk. Microbiol. 45:210-217.

Teaching

ZOO*2050DE Natural History of Ontario
ZOO*2070 Invertebrate Zoology II
ZOO*2080 Invertebrate Zoology II
ZOO*3000 Comparative Histology
ZOO*3500 Research in Zoology
ZOO*6060 Special Topics in Evolution

Grad Students

Gentekaki, Eleni (Ph.D.)
Kher, Chandni (M.Sc.)
Noyes, Megan (M.Sc.)
Rip, Jason (Ph.D.)*
*Co-advised by Kevin McCann

Links

The Journal of Eukaryotic Microbiology
The Ciliate Resource Archive