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Dittmar Hahn, Ph.D. Associate Professor, Molecular Microbial EcologyPhone +1 (512) 245 3372 Fax +1 (512) 245 8713 E-mail: dh49@txstate.edu Department of Biology Texas State University 601 University Drive San Marcos, Texas 78666 USA |
Education
Ph.D. in Microbiology, 1989, Wageningen Agricultural University, The Netherlands, Department of Microbiology (Advisors: Antoon D.L. Akkermans, Alexander J.B. Zehnder)
Research Interests
I am a microbial ecologist using molecular techniques to study uncultured microbial populations in aquatic and terrestrial environments. During the last years, I have mainly addressed questions on the ecology of nitrogen-fixing actinomycetes of the genus Frankia and their host plants, but was also involved in studies on invertebrate-microorganism interactions, the ecophysiology of uncultured purple sulfur and sulfate-reducing bacteria, or the role of microorganims in bioremediation of organic and inorganic contaminants.
Current Research Projects
At the moment, three research topics are addressed:
1. The interaction between uncultured sulfate-reducing bacteria and purple sulfur bacteria is studied in the meromictic Lake Cadagno, Switzerland, in collaboration with Dr. Mauro Tonolla from the Cantonal Institute of Microbiology in Bellinzona, Switzerland. Based on a comprehensive analysis of bacterial diversity in the chemocline of this lake, probes were designed and used to monitor enrichment cultures for up to date uncultured purple sulfur bacteria and associated sulfate-reducing bacteria. Isolates are now available and will be used to further investigate the potential interactions between both bacterial groups.
2. Interactions between the salt marsh plant Spartina patens, microorganisms and the environment focus on the impact of increased nutrient availability (e.g. nitrogen), and of heavy metal or hydrocarbon/PAH contamination on the establishment and performance of plants and microbial populations (mycorrhizae, bacteria) in estuarine environments.
3. Studies on Frankia focus on the interaction of Frankia and Alnus species and address questions on the occurrence of indigenous Frankia populations in different habitats, the fate of introduced Frankia strains, their growth and persistence in soil with and without host plants and the interaction of Frankia strains with each other and soil bacterial populations.
Courses Taught
BIO 4446 Microbial Ecology Syllabus (pdf)
BIO 7360 G Molecular Techniques in Microbial Ecology Syllabus (pdf)
Selected Publications (last 5 years)
Tonolla, M., Peduzzi, S., Demarta, A., Peduzzi, R., Hahn, D. 2004. Phototropic sulfur and sulfate-reducing bacteria in the chemocline of meromictic Lake Cadagno, Switzerland. J. Limnol. 63, 157-166.
Peduzzi, S., Tonolla, M.,Hahn, D. 2003. Isolation and characterization of aggregate-forming phototrophic sulfur and sulfate-reducing bacteria in the chemocline of meromictic Lake Cadagno, Switzerland. FEMS Microbiol. Ecol. 45, 29-37.
Burke, D., Hamerlynck, E., Hahn, D. 2003. Interactions between the salt marsh grass Spartina patens, arbuscular mycorrhizal fungi and sediment bacteria during the growing season. Soil Biol. Biochem. 35, 501-511.
Peduzzi, S., Tonolla, M., Hahn, D. 2003.Vertical distribution of sulfate-reducing bacteria in the chemocline of Lake Cadagno, Switzerland, over an annual cycle. Aquatic Microb. Ecol. 30, 295-302.
Tonolla, M., Peduzzi, S., Hahn, D., Peduzzi, R. 2003. Spatio-temporal distribution patterns of phototrophic sulfur bacteria in the chemocline of meromictic Lake Cadagno (Switzerland). FEMS Microbiol. Ecol. 43, 89-98.
Zimpfer, J., Kaelke, C., Smyth, C.A., Hahn, D., Dawson, J.O. 2003. Frankia isolate, soil biota, and host tissue extracts interact to influence Casuarina nodulation. Plant Soil 254, 1-10.
Burke, D., Hamerlynck, E., Hahn, D. 2002. Interactions among plant species and microorganisms in salt marsh sediments. Appl. Environ. Microbiol. 68, 1157-1164.
Cai, H., Zarda, B., Mattison, G., Schönholzer, F., Hahn, D. 2002. Fate of protozoa transiting the digestive tract of the earthworm Lumbricus terrestris L. Pedobiologia 46, 161-175.
Burke, D., Hamerlynck, E., Hahn, D. 2002. Effect of arbuscular mycorrhizae on soil microbial populations and associated plant performance of the salt marsh grass Spartina patens. Plant Soil 239, 141-154.
Schönholzer, F., Hahn, D., Zarda, B., Zeyer, J. 2002. Image analysis and in situ hybridization as tools to study bacterial populations in food resources, gut and cast of Lumbricus terrestris L. J. Microbiol. Meth. 48, 53-68.
Nickel, A., Pelz. O., Hahn, D., Saurer, M., Siegwolf, R., Zeyer, J. 2001. Effect of inoculation and leaf litter amendment on the establishment of nodule-forming Frankia populations in soil. Appl. Environ. Microbiol. 67, 2603-2609.
Bolliger, C., Schönholzer, F., Schroth, M.H., Hahn, D., Bernasconi, S., Zeyer, J. 2000. Characterization of intrinsic bioremediation by a combined analysis of ground water chemistry, stable carbon isotope ratios and microbial populations in a petroleum contaminated aquifer. Biorem. J. 4, 359-371.
Hahn, D., Nickel, A., Zepp, K., Dawson, J. 2000. Molecular methods for the analysis of Frankia populations in plants and soil. In: Subba Rao, N.S., Dommergues, Y.R. (eds), Microbial interactions in agriculture and forestry, Vol 2, pp. 15-60. Science Publishers, Enfield, NH, USA.
Maunuksela, L., Hahn, D., Haahtela, K. 2000. Effect of freezing of soils on nodulation capacities of total and specific Frankia populations. Symbiosis (Rehovot) 29, 107-120.
Tonolla, M., Demarta, A., Peduzzi, S., Hahn, D.,Peduzzi, R. 2000. In situ analysis of sulfate-reducing bacteria related to Desulfocapsa thiozymogenes in the chemocline of meromictic Lake Cadagno (Switzerland).Appl. Environ. Microbiol. 66, 820-824.
Nickel, A., Hahn, D., Zepp, K., Zeyer, J. 1999. In situ analysis of introduced Frankia populations in root nodules obtained on Alnus glutinosa grown under different water availability. Can. J. Bot. 77, 1231-1238.
Hesselmann, R.P.X., Werlen, C., Hahn, D., van der Meer, J.R., Zehnder, A.J.B. 1999. Enrichment, phylogenetic analysis and detection of a bacterium performing enhanced biological phosphate removal in activated sludge. System. Appl. Microbiol. 22, 454-465.
Berchthold, M., Chatzinotas, A., Schönhuber, W., Brune, A., Amann, R., Hahn, D., König, H. 1999. Differential enumeration and in situ localization of microorganisms in the hindgut of the lower termite Mastotermes darwiniensis by hybridization with rRNA-targeted probes. Arch. Microbiol. 172, 407-416.
Chin, K.-J., Hahn, D., Hengstmann, U., Liesack, W., Janssen, P. 1999. Characterization and identification of numerically abundant culturable bacteria from the anoxic bulk soil of rice paddy microcosms. Appl. Environ. Microbiol. 65 , 5042-5049.
Sandaa, R.-A., Torsvik, V., Enger, Ø., Daae, F.L., Castberg, T., Hahn, D.1999. Analysis of bacterial communities in heavy metal contaminated soils at different levels of resolution. FEMS Microbiol. Ecol. 30, 237-251.
Zepp Falz, K., Holliger, C., Grosskopf, R., Liesack, W., Nozhevnikova, A.N., Müller, B., Wehrli, B., Hahn, D.1999. Vertical distribution of methanogens in the anoxic sediment of Rotsee (Switzerland). Appl. Environ. Microbiol. 65, 2402-2408.
Hahn, D., Nickel, A., Dawson, J. 1999. Assessing Frankia populations in plants and soil using molecular methods. FEMS Microbiol. Ecol. 29, 215-227.
Schönholzer, F., Hahn, D., Zeyer, J. 1999. Origin and fate of fungi and bacteria in the gut of L. terrestris L. studied by image analysis. FEMS Microbiol. Ecol. 28, 235-248.
Tonolla, M., Demarta, A., Peduzzi, R., Hahn, D. 1999. In situ analysis of phototrophic sulfur bacteria in the chemocline of meromictic Lake Cadagno (Switzerland). Appl. Environ. Microbiol. 65, 1325-1330.
Maunuksela, L., Zepp, K., Koivula, T., Zeyer, J., Haahtela, K., Hahn, D. 1999. Analysis of Frankia populations in three soils devoid of actinorhizal plants. FEMS Microbiol. Ecol. 28, 11-21.
Kohli, L., Daniel, O., Schönholzer, F., Hahn, D., Zeyer, J. 1999. Miscanthus sinensis and wild flowers as food resource of Lumbricus terrestris L. Appl. Soil Ecol. 11, 189-197.