Martin HahnMartin Hahn

 

Present position:

Associate Professor, Head of Research Institute
Head of working group "Environmental Microbiology"

Research area:

Ecology and Diversity of Bacteria

Phone:
Fax:
e-mail:

+43 512 507-50244
+43 512 507-50299
martin.hahn@uibk.ac.at


Employment History · Research · Staff · Projects · Teaching · Publications ·
 
Professional Memberships and Honours · Editorial Advisorship/Editorial Board Service


Employment History


  • Nov 2014-present: Associate Professor at the Research Department for Limnology, Mondsee, University of Innsbruck;

  • June 2013–Oct. 2014: Assistant Professor at the Research Institute for Limnology, Mondsee, University of Innsbruck

  • Sept 1, 2012-May 2013: Senior Scientist at the Research Institute for Limnology, Mondsee of the University of Innsbruck and head of working group "Environmental Microbiology"

  • 2005-Aug 31, 2012: Senior Scientist at the Institute for Limnology in Mondsee and head of working group "Environmental Microbiology"
  • 1999-2004: Junior Scientist at the Institute for Limnology in Mondsee and head of working group "Environmental Microbiology"

  • 1997-1998: Postdoctoral Research Associate at Max-Planck-Institute for Limnology, Plön, Germany

  • 2013: venia legendi at Paris Lodron University of Salzburg (Austria)
  • 1997: Ph.D. in Biology/Microbiology at the University of Braunschweig, Germany

  • 1992-1996: Research Associate at the GBF (National Research Center for Biotechnology) in Braunschweig, Germany
  • 1992: M.Sc. (Diplom) in Biology, University of Freiburg

  • 1987: B.Sc., University of Freiburg


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Research

Research interests

  • Microevolution and genome evolution of bacteria
  • Diversity and taxonomy of freshwater bacteria
  • Evolution of obligate endosymbiosis between ciliates (Euplotes spp.) and Polynucleobacter bacteria
  • Physiology and biogeochemical role of abundant freshwater bacteria

We investigate the ecology, diversity, and evolution of bacterial taxa occurring in freshwater systems with high cell numbers. These abundant bacterioplankton taxa are investigated by an approach combining experimental investigations on cultivated representatives and cultivation-independent in situ methods. Our major model organisms are Polynucleobacter bacteria (e.g., Hahn, 2003; Hahn et al., 2009), freshwater Actinobacteria (e.g. Sharma et al. 2009), and filamentous Bacteroidetes affiliated with the genera Aquirestis and Haliscomenobacter (e.g., Schauer & Hahn, 2005). Polynucleobacter spp. (Betaproteobacteria) represent a major component of bacterioplankton in many freshwater lakes and ponds. For instance, the species P. necessarius has a ubiquitous (Jezberova et al., 2010) and cosmopolitan (Hahn et al., 2009) distribution in standing freshwater systems, and occurs in natural systems with relative abundances of up to 70% of total bacterial numbers (Jezberova et al., 2010). Isolation of > 200 P. necessarius strains from a broad diversity of freshwater systems (pH range 3.5 to 9.0) located on all continents and in all climatic zones (including Antarctic, Arctic and tropical zones) enabled a detailed phylogenetic characterization of this taxon (Fig. 1).

Fig. 1. Diversity of Polynucleobacter bacteria. Phylogenetic tree based on 16S rRNA gene sequences of cultivated and uncultivated (environmental sequences) Polynucleobacter spp. strains (Betaproteobacteria). The tree illustrates the phylogenetic diversity and highlights the close phylogenetic relationship between strains with an obligate free-living (planktonic, black font) and strains with an obligate endosymbiotic lifestyle (red font). The previously designated subclusters (Hahn, 2003) PnecA, PnecB1, PnecB2, PnecC, and PnecD represent the species P. rarus, P. difficilis, P. acidiphobus, P. necessarius, and P. cosmopolitanus, respectively.


Fig. 1. Diversity of Polynucleobacter bacteria.
Phylogenetic tree based on 16S rRNA gene sequences of cultivated and uncultivated (environmental sequences) Polynucleobacter spp. strains (Betaproteobacteria). The tree illustrates the phylogenetic diversity and highlights the close phylogenetic relationship between strains with an obligate free-living (planktonic, black font) and strains with an obligate endosymbiotic lifestyle (red font). The previously designated subclusters (Hahn, 2003) PnecA, PnecB1, PnecB2, PnecC, and PnecD represent the species P. rarus, P. difficilis, P. acidiphobus, P. necessarius, and P. cosmopolitanus, respectively.

Based on these phylogenetic characterization (i.e. 16S-23S ITS sequences), reverse line blot hybridization (RLBH) probes were developed, which enable the specific detection of P. necessarius subgroups in environmental samples (Jezbera et al., 2011). This method was used to test if the ubiquitous and cosmopolitan distribution of the species results from a generalist adaptation or from radiation in specialized lineages differing in environmental adaptations. Investigation of 121 habitats for presence/absence of these subgroups revealed that ubiquity of the species resulted from ecological diversification (Jezbera et al., 2011).

Fig. 2. Pond-1, a small acidic pond located at an altitude of 1300 m in the Austrian Alps. This pond is persistently inhabited by a particular P. necessarius lineage represented by a genome-sequenced strain (strain QLW-P1DMWA-1).


Fig. 2. Pond-1, a small acidic pond located at an altitude of 1300 m in the Austrian Alps. This pond is persistently inhabited by a particular P. necessarius lineage represented by a genome-sequenced strain (strain QLW-P1DMWA-1).

Sequencing of the genome of a free-living representative of a P. necessarius lineage (F10) contributing on average 11% of bacterioplankton in a small pond (Pond-1; Fig. 2) revealed an unexpected small genome size (2.1 Mbp), and comparative genome analyses suggested a highly passive lifestyle of the bacterium (Hahn et al., 2012). This bacterium lacks flagella-mediated motility, quorum sensing, and encodes only a small number of signal transduction genes (Fig. 3). Several other strains also affiliated with the F10 lineage could be isolated from Pond-1 over a period of four years. Interestingly, multilocus sequence analysis of these strains revealed only very minor genetic differences between those strains (only 0.17% polymorphic sites), which indicate a rather low microdiversity of the F10 population persisting in Pond-1. It is surprising that a low-diversity population of a bacterium with a highly passive lifestyle comprises on average 11% to bacterial numbers in a limnologically quite dynamic habitat (Hahn et al., 2012).

Fig. 3. Gene number of bacterial genomes versus number of encoded signal transduction genes. The plot depicts the total number of annotated signal transduction genes in particular bacterial genomes versus the total number of genes of the respective genomes. P. necessarius QLW-P1DMWA-1 isolated from Pond-1 is highlighted as a yellow dot. (A) Entire data set consisting of 904 analyzed bacterial genomes. Red dots indicate bacteria obligately associated as symbionts or pathogens with a host; blue dots indicate free-living or facultative host-associated bacteria. (B) Plot of genomes of bacteria classified as free-living or facultative host-associated (shown in (A) as blue dots) with ≤ 100 signal transduction genes. All blue dots represent bacteria either facultatively associated with hosts (e.g., dwelling in the oral cavity or in the intestinal tract) or dwelling as free-living organisms in extreme environments (permanently anoxic, low or high temperature, low pH). The yellow (Polynucleobacter) and the green dots represent the only exclusively free-living taxa inhabiting non-extreme systems. Almost all of them are phototrophic (Synechococcus and Prochlorococcus) or predominantly heterotrophic taxa (Pelagibacter and Puniceispirillum) dwelling as planktonic bacteria in marine systems. (Hahn et al., 2012)


Fig. 3. Gene number of bacterial genomes versus number of encoded signal transduction genes. The plot depicts the total number of annotated signal transduction genes in particular bacterial genomes versus the total number of genes of the respective genomes. P. necessarius QLW-P1DMWA-1 isolated from Pond-1 is highlighted as a yellow dot. (A) Entire data set consisting of 904 analyzed bacterial genomes. Red dots indicate bacteria obligately associated as symbionts or pathogens with a host; blue dots indicate free-living or facultative host-associated bacteria. (B) Plot of genomes of bacteria classified as free-living or facultative host-associated (shown in (A) as blue dots) with ≤ 100 signal transduction genes. All blue dots represent bacteria either facultatively associated with hosts (e.g., dwelling in the oral cavity or in the intestinal tract) or dwelling as free-living organisms in extreme environments (permanently anoxic, low or high temperature, low pH). The yellow (Polynucleobacter) and the green dots represent the only exclusively free-living taxa inhabiting non-extreme systems. Almost all of them are phototrophic (Synechococcus and Prochlorococcus) or predominantly heterotrophic taxa (Pelagibacter and Puniceispirillum) dwelling as planktonic bacteria in marine systems. (Hahn et al., 2012)

By combining genome analysis, physiological characterization (e.g. substrate assimilation tests), and experimental investigations we could get insights in the ecological role of the F10 lineage bacteria inhabiting Pond-1 (Fig. 4; Hahn et al., 2012). These investigations suggested that this lineage is mostly utilizing low molecular weight photooxidation products of humic substances mainly resulting from the impact of UV light on humic substances contained in the water column of the pond. These findings again reflect the highly passive lifestyle of the F10 lineage bacteria.

Fig. 4. Conceptual model on carbon fluxes utilized by the P. necessarius F10 lineage population in Pond-1. The model suggests origin and transformation of major carbon sources utilized by the F10 lineage population inhabiting Pond-1. Humic substances (HS) leached from soils (1) and floating mats (2) (Schwingrasen, formed mainly of Sphagnum and Carex) are transported by percolating water to the pond. Polynucleobacter bacteria affiliated with the F10 lineage mainly utilize low-molecular-weight (LMW) photooxidation products of HS (3). Direct utilization of aliphatic residues of HS by enzymatic cleavage is also expected to take place (4). Another potential substrate source could be fermentation products released by bioturbation and other processes from the sediment (5) to the water column of the pond. (Hahn et al., 2012)


Fig. 4. Conceptual model on carbon fluxes utilized by the P. necessarius F10 lineage population in Pond-1. The model suggests origin and transformation of major carbon sources utilized by the F10 lineage population inhabiting Pond-1. Humic substances (HS) leached from soils (1) and floating mats (2) (Schwingrasen, formed mainly of Sphagnum and Carex) are transported by percolating water to the pond. Polynucleobacter bacteria affiliated with the F10 lineage mainly utilize low-molecular-weight (LMW) photooxidation products of HS (3). Direct utilization of aliphatic residues of HS by enzymatic cleavage is also expected to take place (4). Another potential substrate source could be fermentation products released by bioturbation and other processes from the sediment (5) to the water column of the pond. (Hahn et al., 2012)

Future studies will focus on microevolution, genome evolution, biogeography, and physiology of our model bacteria.


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Staff


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Projects

  • Ecological Diversity of Polynucleobacter Bacteria, funded by the Austrian Science Fund (FWF), Project no. P19853, finished

  • Polynucleobacter Genome Project, funded by the DOE Joint Genome Institute (USA), finished
    Genome sequencing of a free-living Polynucleobacternecessarius strain Link and a obligately endosymbiotic P. necessarius strain Link

  • Mechanisms Controlling the Diversity of Bacterioplankton, funded by the Austrian Science Fund (FWF), Project no. P15655-Bio, finished

  • Interaction of Protists and Bacteria (Jubiläumsfondsprojekt #7767,) funded by the Austrian National Bank, finished

  • Biogeography and within-taxon ecological differentiation of Polynucleobacter necessarius subsp. asymbioticus and Limnohabitans planctonicus (Betaproteobacteria), Austrian-Czech cooperation project with Jan Jezbera (Czech Republic), funded by the OEAD, finished

  • Ecological and phylogenetic comparison of bacterial populations inhabiting Antarctic and European lakes, binational Acciones Integradas Projekt with Antonio Camacho (Spain) funded by the OEAD, finished

  • Eco-physiological characteristics of two important groups of Betaproteobacteria abundant in freshwater bacterioplankton, Austrian-Czech cooperation project with Karel Šimek (Czech Republic), funded by the OEAD, finished


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Teaching

at University of Innsbruck in Innsbruck or at Research Department for Limnology, Mondsee (ILIM), in German

Wahlmodul 19C Genomevolution (Bachelorstudium)-ILIM

Biologisches Seminar (Mikrobiologie, Bachelorstudium)

VO Einführung in die Systematik der Mikroorganismen (Bachelorstudium)

VO Systematik I (Bacteria, Archaea) (Masterstudium Mikrobiologie)

Wahlmodul Evolutionsökologie aquatischer Organismen (Masterstudium Ökol./Biodiv.)-ILIM


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Publications

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in press

 


  • Hahn M.W., Schmidt J., Ssanyu G.A., Kyrpides N.C., Whitman W.B. (in press) Reclassification of a Polynucleobacter cosmopolitanus strain isolated from tropical Lake Victoria as Polynucleobacter victoriensis sp. nov. Int. J. Syst. Evol. Microbiol.

2017

  • Hahn M.W., Koll U., Karbon G., Schmidt J., Lang E. (2017). Polynucleobacter aenigmaticus sp. nov. isolated from the permanently anoxic monimolimnion of a meromictic lake in Austria. Int. J. Syst. Evol. Microbiol. 67:4646–4654 doi: 10.1099/ijsem.0.002347

  • Hoetzinger M., Hahn M. W. (2017). Genomic divergence and cohesion in a species of pelagic freshwater bacteria. BMC Genomics 18: 794 https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-017-4199-z doi.org/10.1186/s12864-017-4199-z

  • Hahn M.W., Karbon G., Koll U., Schmidt J., Lang E. (2017). Polynucleobacter sphagniphilus sp. nov. a planktonic freshwater bacterium isolated from an acidic and humic freshwater habitat. Int. J. Syst. Evol. Microbiol. 67:3261-3267

  • Hahn M.W., Schmidt J., Koll U., Rohde M., Verbarg S., Pitt  A., Nakai R., Naganuma T., Lang E. (2017). Silvanigrella aquatica gen. nov., sp. nov., isolated from a freshwater lake, description of Silvanigrellaceae fam. nov. and Silvanigrellales ord. nov., reclassification of the order Bdellovibrionales in the class Oligoflexia, reclassification of the families Bacteriovoracaceae and Halobacteriovoraceae in the new order Bacteriovoracales ord. nov., and reclassification of the family Pseudobacteriovoracaceae in the order Oligoflexales. Int J Syst Evol Microbiol 67:2555–2568  doi: http://dx.doi.org/10.1099/ijsem.0.001965

  • Vannini C. , Sigona C., Hahn M.W., Petroni G., Fujishima M. (2017). High degree of specificity in the association between symbiotic Betaproteobacteria and the host Euplotes (Ciliophora, Euplotia). Eur. J. Protistol. 59:124–132 https://doi.org/10.1016/j.ejop.2017.04.003

  • Hahn, M.W., Huymann, L.R., Koll, U., Schmidt, J., Lang, E.,  Hoetzinger, M. (2017). Polynucleobacter wuianus sp. nov., a free-living freshwater bacterium affiliated with the cryptic species complex PnecC. Int. J. Syst. Evol. Microbiol. 67:379–385

  • Hoetzinger M., Hahn M.W., Jezberová J., Schmidt J., Koll U. (2017). Microdiversification of a pelagic Polynucleobacter species is mainly driven by acquisition of genomic islands from a partially interspecific gene pool. Applied and Environmental Microbiology (AEM) 83: 3 e02266-16, doi.org/10.1128/aem.02266-16

2016

  • Hahn M. W. (2016). Rhodoluna, 1–9 DOI: 10.1002/9781118960608.gbm01312, In: Whitman, W.B. (ed.) Bergey's Manual of Systematics of Archaea and Bacteria, Wiley Online ISBN: 9781118960608

  • Nakamura S., Kikukawa T., Tamogami J., Kamiya M., Aizawa T., Hahn M.W., Ihara K., Kamo N., Demura M. (2016). Photochemical characterization of actinorhodopsin and its functional existence in the natural host. Biochimica et Biophysica Acta-Bioenergetics 1857: 1900–1908.

  • Hahn M. W., Schmidt J., Pitt A., Taipale S. J., Lang E. (2016). Reclassification of four Polynucleobacter necessarius strains as Polynucleobacter asymbioticus comb. nov., Polynucleobacter duraquae sp. nov., Polynucleobacter yangtzensis sp. nov., and Polynucleobacter sinensis sp. nov., and emended description of the species Polynucleobacter necessarius. Int. J. Syst. Evol. Microbiol. 66: 2883–2892. PDF

  • Hahn M.W., Jezberová J., Koll U., Saueressig-Beck T., Schmidt J. (2016). Complete ecological isolation and cryptic diversity in Polynucleobacter bacteria not resolved by 16S rRNA gene sequences. The ISME Journal 10:1642-1655. pdf

2015

  • Taipale, S.J., Peltomaa, E., Hiltunen, M., Jones, R.I., Hahn, M.W., Biasi, C., Brett, M.T. (2015) Inferring phytoplankton, terrestrial plant and bacteria bulk delta C-13 values from compound specific analyses of lipids and fatty acids. PLOS ONE 10(7) e0133974

  • Keffer J.L., Hahn M.W., Maresca J.A. (2015). Characterization of an unconventional rhodopsin from the freshwater Actinobacterium Rhodoluna lacicola. J. Bacteriol.  197(16) 2704-2712 doi:10.1128/JB.00386-15

  • Keffer J. L., Sabanayagam C. R., Lee M. E., DeLong E. F., Hahn M. W., Maresca, J. A. (2015). Identifying rhodopsin-containing cells using TIRF microscopy. Applied and Environmental Microbiology. 81:10 3442-3450.

  • Hahn, M.W., Koll, U., Jezberova, J. and A. Camacho (2015). Global phylogeography of pelagic Polynucleobacter bacteria: Restricted geographic distribution of subgroups, isolation by distance, and influence of climate. Environ. Microbiol.17(3), 829–840. PDF

2014

  • Hahn M.W., Schmidt J., Taipale S.J., Doolittle W.F., Koll U. (2014). Rhodoluna lacicola gen. nov., sp. nov., a planktonic freshwater bacterium with stream-lined genome. Int. J. Syst. Evol. Microbiol., 64: 3254–3263. PDF

  • Taipale, S.J., Brett, M.T., Hahn, M.W., Martin-Creuzburg, D., Yeung, S., Hiltunen, M., Strandberg, U., and P. Kankaala (2014). Differing Daphnia magnaassimilation efficiencies for terrestrial, bacterial and algal carbon and fatty acids. Ecology 95:563–576.

2013

  • Jezberova, J., Jezbera, J., and Hahn M.W. (2013). Insights into variability of actinorhodopsin genes of the LG1 cluster in two different freshwater habitats. PLoS ONE 8(7): e68542.
  • Šimek K., Kasalický V., Jezbera J., Horňák K., Nedoma J., Hahn M.W., Bass D., Jost S., Boenigk J. (2013). Differential freshwater flagellate community response to bacterial food quality with a focus on Limnohabitans bacteria. The ISME Journal 7: 1519–1530.
  • Kasalický V., Jezbera J., Hahn M.W., Šimek K. (2013). The diversity of the Limnohabitans genus, an important group of freshwater bacterioplankton, by characterization of 35 isolated strains. PLoS ONE 8(3): e58209, doi:10.1371/journal.pone.0058209
  • Jezbera J., Jezberová J., Kasalický V., Šimek K., Hahn M.W. (2013). Patterns of Limnohabitans microdiversity across a large set of freshwater habitats as revealed by Reverse Line Blot Hybridization. PLoS ONE 8(3): e58527, doi:10.1371/journal.pone.0058527

2012

  • Jezbera J., Jezberová J., Koll U., Hornak K., Simek K., Hahn M.W. (2012). Contrasting trends in distribution of four major planktonic betaproteobacterial groups along a pH gradient of epilimnia of 72 freshwater habitats. FEMS Microbiology Ecology 81: 467-479.

  • Hahn M.W., Scheuerl T., Jezberová J., Koll U., Jezbera J., Šimek K., Vannini C., Petroni G., Wu Q. L. (2012). The passive yet successful way of planktonic life: Genomic and experimental analysis of the ecology of a free-living Polynucleobacter population. PLoS ONE 7(3): e32772. PDF

  • Meincke L., Copeland A., Lapidus A.,  Lucas S.,  Berry K. W.,  Glavina Del Rio T., Hammon N.,  Dalin E.,  Tice H., Pitluck  S.,   Richardson  P.,  Bruce, D., Goodwin L., Han C.,  Tapia R., Detter J. C., Schmutz J., Brettin  T., Larimer  F.,  Land M., Hauser  L., Kyrpides N. C., Ivanova N., Göker M., Woyke T., Wu Q. L., Pöckl M., Hahn M. W., Klenk H.-P. (2012). Complete genome sequence of Polynucleobacter necessarius subsp. asymbioticus type strain (QLW-P1DMWA-1T). Standards in Genomic Sciences 6: 74-83 doi:  10.4056/sigs.2395367

  • Hahn M.W., Minasyan A., Lang E., Koll U., Spröer, C. (2012). Polynucleobacter difficilis sp. nov., a planktonic freshwater bacterium affiliated with subcluster B1 of the genus Polynucleobacter. Int. J. Syst. Evol. Microbiol. 62: 376 - 383.

2011

  • Wang, J., Yang, D., Zhang, Y., Shen, J., van der Gast, C., Hahn, M.W., and Q. Wu (2011) Do Patterns of Bacterial Diversity along Salinity Gradients Differ from Those Observed for Macroorganisms? PLoS ONE 6(11): e27597. LINK

  • Taipale, S., Kankaala, P., Hahn, M. W., Jones, R. I., and Tiirola, M. (2011). Methane oxidizing and photoautotrophic bacteria are major producers in a humic lake with large anoxic hypolimnion. Aquat Microb Ecol. 64: 81–95.

  • Hahn, M.W., Lang, E., Tarao, M., and Brandt, U. (2011). Polynucleobacter rarus sp. nov., a free-living planktonic bacterium isolated from an acidic lake. Int. J. Syst. Evol. Microbiol. 61: 781-787. PDF

  • Hahn, M.W., Lang, E., Brandt, U., and Spröer, C. (2011). Polynucleobacter acidiphobus sp. nov., a representative of an abundant group of planktonic freshwater bacteria. Int. J. Syst. Evol. Microbiol. 61: 788-794. PDF Suppl.Mat.

  • Jezbera, J., Jezberová, J., Brandt, U., and Hahn, M.W. (2011). Ubiquity of Polynucleobacter necessarius subspecies asymbioticus results from ecological diversification. Environ. Microbiol. 13: 922–931. PDF

2010

  • Kasalický, V, Jezbera, J., Šimek, K., and Hahn, M.W. (2010). Limnohabitans planktonicus sp. nov., and Limnohabitans parvus sp. nov., two novel planktonic Betaproteobacteria isolated from a freshwater reservoir and emended description of the genus Limnohabitans. Int. J. Syst. Evol. Microbiol. 60: 2710-2714.

  • Hahn, M.W., Kasalický, V., Jezbera, J., Brandt, U., and Šimek, K. (2010). Limnohabitans australis sp. nov., isolated from a freshwater pond, and emended description of the genus Limnohabitans. Int. J. Syst. Evol. Microbiol. 60: 2946-2950. PDF

  • Hahn, M.W., Kasalický, V., Jezbera, J., Brandt, U., Jezberová, J., and Šimek, K. (2010). Limnohabitans curvus gen. nov., sp. nov., a planktonic bacterium isolated from a freshwater lake. Int. J. Syst. Evol. Microbiol. 60: 1358-1365.

  • Jezberová, J., Jezbera, J., Brandt, U., Lindström, E.S., Langenheder, S., and Hahn, M.W. (2010). Ubiquity of Polynucleobacter necessarius ssp. asymbioticus in lentic freshwater habitats of a heterogenous 2000 km2 area. Environ. Microbiol. 12: 658-669.

  • Šimek, K., Kasalický, V, Horňák, K., Hahn M.W., and Weinbauer, M.G. (2010). Assessing niche separation among coexisting Limnohabitans strains through interactions with a competitor, viruses, and a bacterivore. Appl. Environ. Microbiol. 76: 1406–1416.

  • Šimek, K., Kasalický, V., Jezbera, J., Jezberová, J., Hejzlar, J., and Hahn, M.W. (2010). Broad habitat range of the phylogenetically narrow R-BT065 cluster, representing a core group of the betaproteobacterial genus Limnohabitans. Appl. Environ. Microbiol. 76: 631-639.

  • Hahn, M.W., Lang, E., Brandt, U., Lünsdorf, H., Wu, Q.L., and E. Stackebrandt. (2010): Polynucleobacter cosmopolitanus sp. nov., free-living planktonic bacteria inhabiting freshwater lakes and rivers. Int. J. Syst. Evol. Microbiol. 60: 166-173.

2009

  • Xing, P., Hahn, M.W., and Wu, Q.L. (2009): Low taxa richness of bacterioplankton in high-altitude lakes of the Eastern Tibetan Plateau with predominance of Bacteroidetes and Synechococcus. Appl. Environ. Microbiol. 75: 7017–7025

  • Jezbera, J., Sharma, A.K., Brandt, U., Doolittle, W.F., and M.W. Hahn. (2009): "Candidatus Planktophila limnetica", an actinobacterium representing one of the most numerically important taxa in freshwater bacterioplankton. Int. J. Syst. Evol. Microbiol. 59: 2864-2869.

  • Hahn, M.W., Lang, E., Brandt, U., Wu, Q.L., and Scheuerl, T. (2009): Emended description of the genus Polynucleobacter and the species P. necessarius and proposal of two subspecies, P. necessarius subspecies necessarius subsp. nov. and P. necessarius subsp. asymbioticus subsp. nov. Int. J. Syst. Evol. Microbiol. 59: 2002-2009.

  • Tarao, M., Jezbera, J., and Hahn, M.W. (2009): Involvement of cell surface structures in size-independent grazing resistance of freshwater Actinobacteria. Appl. Environ. Microbiol. 75: 4720-4726.

  • Hahn, M.W. (2009): Real-time evolution observatories in the wild (Crystal ball - 2009). Environ. Microbiol. Reports 1: 8-9.

  • Sharma, A.K., Sommerfeld, K., Bullerjahn, G.S., Matteson, A.R., Wilhelm, S.W., Jezbera, J., Brandt, U., Doolittle, W.F., and Hahn, M.W. (2009): Actinorhodopsin genes discovered in diverse freshwater habitats and among cultivated freshwater Actinobacteria. The ISME Journal 3: 726–737.

  • Hahn, M.W. (2009): Description of seven Candidatus species affiliated with the phylum Actinobacteria, representing planktonic freshwater bacteria. Int. J. Syst. Evol. Microbiol. 59: 112-11.

2008

  • Hahn, W.W. and Wu, Q.L. (2008): Planktonic bacteria in Chinese and European lakes: Are they different? In: Microbes and the Environment: Perspective and Challenges, S.-J. Liu H. L. Drake (eds.), Science Press, Beijing, pp. 73-78.

2007

  • Wu, Q.L., Zwart, G., Wu, J. , Kamst-van Agterveld, M.P., Liu, S., and Hahn, M.W. (2007): Submersed macrophytes play a key role in structuring bacterioplankton community composition in the large, shallow, subtropical Taihu Lake, China. Environ. Microbiol. 9:2765–2774.

  • Groben, R., Hahn, M.W., Horňák, K., Mergeay, J., Šimek, K., and Vrb, J.. (2007): Meeting Report: ALTER-Net Workshop about the “Application of Molecular Techniques to Study Biodiversity, Structure and Function of Planktonic Communities in Lakes” at Blanes, Spain, February 15-16, 2007. Protist 158:417-421.

  • Hahn, M.W. and Schauer, M. (2007): ‘Candidatus Aquirestis calciphila’ and ‘Candidatus Haliscomenobacter calcifugiens’, filamentous, planktonic bacteria inhabiting natural lakes. Int. J. Syst. Evol. Microbiol. 57:936-940.

  • Wu, Q.L., Chen, Y., Xu, K., Liu, Z., and Hahn, M.W. (2007): Intra-habitat heterogeneity of microbial food web structure under the regime of eutrophication and sediment resuspension in the large subtropical shallow Lake Taihu, China. Hydrobiologia 581:241–254.

  • Vannini, C., Pöckl, M., Petroni, G., Wu, Q.L., Lang, E., Stackebrandt, E., Schrallhammer, M., Richardson, P.M., and Hahn, M.W. (2007): Endosymbiosis in statu nascendi: Close phylogenetic relationship between obligately endosymbiotic and obligately free-living Polynucleobacter strains (Betaproteobacteria). Environ. Microbiol. 9:347-359.

2006

  • Wu, Q.L., Zwart, G., Schauer, M., Kamst-van Agterveld, M.P., and Hahn, M.W. (2006): Bacterioplankton community composition along a salinity gradient of sixteen high-mountain lakes located on the Tibetan Plateau, China. Appl. Environ. Microbiol. 72:5478–5485.

  • Wu, Q.L. and Hahn, M.W. (2006b): High predictability of the seasonal dynamics of a species-like Polynucleobacter population in a freshwater lake. Environ. Microbiol. 8:1660-1666.

  • Šimek, K., Horňák, K. , Jezbera, J. , Nedoma, J. , Vrba, J., Straškrábová, V. , Macek, M. , Dolan, J. R., and Hahn., M.W. (2006): Maximum growth rates and possible life strategies of different bacterioplankton groups in relation to phosphorus availability in a freshwater reservoir. Environ. Microbiol. 8:1613-1624.

  • Schauer, M., Jing, J., and Hahn, M.W. (2006): Recurrent seasonal variations in abundance and composition of filamentous SOL cluster bacteria (Saprospiraceae, Bacteroidetes) in oligomesotrophic Lake Mondsee (Austria). Appl. Environ. Microbiol. 72:4704-4712.

  • Hahn, M.W. (2006): The microbial diversity of inland waters. Current Opinion in Biotechnology 17: 256-261.

  • Wu, Q.L. and Hahn, M.W. (2006): Differences in structure and dynamics of Polynucleobacter communities in a temperate and a subtropical lake revealed at three phylogenetic levels. FEMS Microb. Ecol. 57(1):67.

2005

  • Schauer, M., Kamenik, C., and Hahn, M.W. (2005): Ecological differentiation within a cosmopolitan group of planktonic freshwater bacteria (SOL cluster, Saprospiraceae, Bacteroidetes). Appl. Environ. Microbiol. 71:5900–5907.

  • Camacho, A., Rochera, C., Silvestre, J.J., Vicente, E., and Hahn, M.W. (2005): Spatial Dominance and Inorganic Carbon Assimilation by Conspicuous Autotrophic Biofilms in a Physical and Chemical Gradient of a Cold Sulfurous Spring: The Role of Differential Ecological Strategies. Microb. Ecol. 50: 172 - 184. Link

  • Hahn, M.W., Pöckl, M., and Wu, Q.L. (2005): Low intraspecific diversity in a Polynucleobacter subcluster population numerically dominating bacterioplankton of a freshwater pond. Appl. Environ. Microbiol. 71: 4539–4547. Abstract

  • Schauer, M. and Hahn, M.W. (2005): Diversity and phylogenetic affiliations of morphologically conspicuous large filamentous bacteria occurring in the pelagic zones of a broad spectrum of freshwater habitats. Appl. Environ. Microbiol. 71: 1931-1940. Abstract PDF

  • Hahn, M.W. and Pöckl, M. (2005): Ecotypes of planktonic Actinobacteria with identical 16S rRNA genes adapted to thermal niches in temperate, subtropical, and tropical freshwater habitats. Appl. Environ. Microbiol. 71: 766–773. Abstract PDF

2004

  • Boenigk, J., Stadler, P., Wiedlroither, A., and Hahn, M.W. (2004): Strain-specific differences in the grazing sensitivities of closely related ultramicrobacteria affiliated with the Polynucleobacter cluster. Appl. Environ. Microbiol. 70: 5787-5793.

  • Hahn, M.W. (2004): Broad diversity of viable bacteria in ‘sterile’ (0.2µm) filtered water. Research in Microbiology 155: 688-691. Abstract

  • Hahn, M.W., Stadler, P., Wu, Q.L., and Pöckl, M. (2004): The filtration–acclimatization method for isolation of an important fraction of the not readily cultivable bacteria. Journal of Microbiological Methods 57: 379-390. Abstract

  • Hahn, M.W., Lünsdorf, H., and Janke, L. (2004): Exopolymer production and microcolony formation play an important role in protistan grazing defense of novel bacterial strains isolated from freshwater plankton. Aquat Microb Ecol. 35:297-308. Link

  • Wu Q.L., Boenigk J., and Hahn M.W. (2004): Successful predation by a nanoflagellate on filamentous bacteria challenges current models on flagellate bacterivory. Appl. Environ. Microbiol. 70: 332–339. Abstract PDF

2003

  • Hahn, M.W. (2003): Isolation of Strains Belonging to the Cosmopolitan Polynucleobacter necessarius Cluster from Freshwater Habitats Located in Three Climatic Zones. Appl. Environ. Microbiol. 69: 5248-5254. Abstract

  • Hahn, M.W., Lünsdorf, H., Wu, Q., Schauer, M., Höfle, M. G., Boenigk, J., and Stadler P. (2003): Isolation of novel ultramicrobacteria classified as Actinobacteria from five freshwater habitats in Europe and Asia. Appl. Environ. Microbiol. 69(3): 1442-1451. Abstract PDF

2001

  • Hahn, M.W. and Höfle, M.G.(2001): Grazing of protozoa and its effect on populations of aquatic bacteria (MiniReview). FEMS Microbiology Ecology 35: 113-121. Abstract Full article: PDF

2000

  • Hahn, M.W., Moore, E.R.B., and Höfle, M.G. (2000):. Role of microcolony formation in the protistan grazing defense of the aquatic bacterium Pseudomonas sp. MWH1. Microbial Ecology 39: 175-185. Abstract 

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Professional Memberships and Honours

  • Ambassador of the International Society for Microbial Ecology (ISME) Link (2003-present)

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Editorial Advisorship/Editorial Board Service

  • Frontiers in Aquatic Microbiology (2010-present)

  • Applied and Environmental Microbiology (2001-2010)

  • Environmental Microbiology (2009-present)


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