Andreas Brune
Department of Biogeochemistry
Andreas Brune
born 22.03.60
Diplom (Biology), University of Marburg, 1986
Dr. rer. nat. (Microbiology), University of Tübingen, 1990
Postdoc (Microbiology), Michigan State University, East Lansing, 1991–1993
Research Associate and Group Leader (Microbial Ecology), University of
Konstanz, 1993–2003
Habilitation (Microbiology and Microbial Ecology), University of Konstanz,
2000
Research Group Leader (C3), Department of Biogeochemistry, MPI Marburg,
since 2003
Adjunct Professor, Biology Department, Philipps-Universität Marburg, since
2005
Insect gut microbiology and symbiosis
Termite guts are tiny bioreactors that convert lignocellulosic matter to microbial fermentation products fueling
the metabolism of their host. We are studying the role
of the gut microbiota in the symbiotic digestion of wood
— either sound or in its various stages of humification.
Our particular interest lies in the biology of prokaryotic
and eukaryotic gut microorganisms of wood-feeding termites, their symbiotic interactions, and the ecology of
the intestinal microecosystem. Further projects concern
microbial processes in the intestinal tracts of other globally important groups of soil fauna, including soil-feeding
termites and the humivorous larvae of scarab beetles.
During the last decade, our analysis of structure–function relationships among the gut microbiota revealed a
central role of molecular hydrogen in the intestinal processes of wood-feeding lower termites (Brune, 2009).
The hydrogen is formed during lignocellulose digestion
by anaerobic protists that occupy the bulk of the hindgut
volume. These flagellates are found exclusively in termite guts and are consistently associated with prokaryotic symbionts that colonize both the surface and cell
contents of their eukaryotic hosts.
Symbionts of termite gut flagellates
Following up on our discovery that a wide range of termite gut flagellates harbor specific lineages of bacterial endosymbionts from the candidate phylum Termite
Group 1 (TG1), we started to investigate the evolutionary relationship between the symbiotic pairs in more
detail. We could show that each lineage of these “Endomicrobia” must have been acquired independently by
certain flagellate lineages, either from free-living forms
or by horizontal transfer of endosymbionts (Desai et al.,
2009), whereas the “Endomicrobia” within a particular
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flagellate lineage were vertically transferred, leading to
cospeciation of the symbiotic pair (Ikeda-Ohtsubo and
Brune, 2009). The acquisition of “Endomicrobia” by gut
flagellates of the genus Trichonympha apparently took
place long after the establishment of the symbiosis between termites and gut flagellates ca. 130 million years
ago. This was corroborated by the detection of basal lineages of putatively free-living “Endomicrobia” in artificially defaunated termites (Ikeda-Ohtsubo et al., 2010;
Fig. 1). Together with colleagues at the Joint Genome
Institute (JGI) of the U.S. Department of Energy, we
sequenced and annotated the metagenome of “Candidatus Endomicrobium trichonymphae”, which colonize the
Trichonympha species in Zootermopsis nevadensis (Herlemann et al., in preparation).
In collaboration with the group of Renate Radek from
the Free University of Berlin, we also studied the molecular phylogeny and ultrastructure of a deep-branching lineage of uncultivated Bacteroidetes that colonize
the cell surface of devescovinid flagellates of dry-wood
termites (Desai et al., 2009; Fig. 2). We could show
that “Candidatus Armantifilum devescovinae” is strictly
cospeciating with flagellates of the genus Devescovina,
which indicates an intimate metabolic relationship between the partners in the symbiosis. We are currently
investigating the possible role of the ectosymbionts in
nitrogen fixation. Interestingly, ectosymbiontic Bacteroidetes are absent from Metadevescovina species, a phylogenetic sister group of devescovinid flagellates (Strassert
et al., 2009), which suggests that also these ectosymbionts were originally recruited from free-living ancestors
in the termite gut.
Andreas Brune
Department of Biogeochemistry
the discovery that the microbial processes in the gut
are fueled by nitrogenous soil components — a finding
that we could recently extend also to humivorous scarab
beetle larvae (Andert et al., 2008). The digestion of peptides and the subsequent fermentation of amino acids in
the gut of soil-feeding termites give rise to an enormous
accumulation of ammonia, which is partially oxidized
and denitrified by a hitherto unknown process (Ngugi
et al., submitted). So far, little is known about the gut
microbiota of soil-feeding termites, which comprises
large populations of phylogenetically novel and hitherto
uncultivated bacteria of unknown function (e.g., Köhler
et al., 2008). We are currently investigating the diversity of the gut microbiota in their highly compartmented
intestinal tracts and their functional roles using highthroughput sequencing and 15N tracer techniques.
Fig. 1. Phylogenetic tree of the Elusimicrobia phylum (formerly
TG1), illustrating the major phylogenetic lineages harboring clones from many different habitats. Endomicrobia (red)
represent obligate endosymbionts of termite gut flagellates,
but also comprise putatively free-living forms (Ikeda-Ohtsubo
et al., 2010). The only cultivated representative of the phylum
is Elusimicrobium minutum, a member of the Intestinal cluster
(green) (Geissinger et al., 2009).
The first isolate of the Elusimicrobia phylum
A recent highlight of our research was the isolation
of the first member of the Elusimicrobia phylum (formerly TG1) from the hindgut of a humivorous beetle
larva (Geissinger et al., 2009). The ultramicrobacterium
Elusimicrobium minutum is a representative of the hitherto uncultivated „Intestinal cluster“ of 16S rRNA gene
sequences occurring in the guts of insects and also the
cow rumen, and is only distantly related to the “Endomicrobia” (Fig. 1). In collaboration with our colleagues
at the JGI, we conducted a complete genome analysis
of E. minutum, which gave important insights into the
metabolism of this species, including its unusual cofermentation of sugars and amino acids (Herlemann et
al., 2009; Fig. 3).
Fig. 2. Scanning electron micrographs of a Devescovina species and its ectosymbiotic bacteria. The entire surface of the
flagellate (A) is covered by a layer of uniform, filamentous bacteria (B) classified as “Candidatus Armantifilum devescovinae”,
which have strictly cospeciated with their host flagellates (Desai et al., 2009). Scale bars: 20 µm (A), 3 µm (B); the arrows indicate the tips of a single filament.
Microbial processes in soil-feeding insects
Little is known about the digestive processes in higher
termites, especially the soil-feeding taxa, which are hot
spots of carbon and nitrogen mineralization in tropical
soils and globally significant sources of the greenhouse
gas methane (Brune, 2009). Our previous studies of the
transformation and mineralization of soil organic matter in the intestinal tract of soil-feeding termites led to
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Department of Biogeochemistry
Andreas Brune
Fig. 3. The energy metabolism of Elusimicrobium minutum, the first isolate of the Elusimicrobia (formerly TG1 phylum). Sugars are
degraded via the Embden-Meyerhof pathway and pyruvate-ferredoxin oxidoreductase (PFOR) (blue box). NADH is regenerated by reduction of acetyl-CoA to ethanol or, at low hydrogen partial pressure, by the cytoplasmic [FeFe] hydrogenase. Reduced ferredoxin is
regenerated by the membrane-bound [NiFe] hydrogenase. Amino acids are metabolized by transamination with pyruvate and subsequently oxidatively decarboxylated to the corresponding acids by several homologs of PFOR (yellow box). Alanine can be generated not
only by transamination but also by reductive amination of pyruvate (green box). The export of alanine generates a sodium-motive force,
which is coupled to the proton-motive force, the synthesis/hydrolysis of ATP via ATP synthase, and the proton-dependent uptake of
amino acids or oligopeptides. Pathways were reconstructed based on the manually annotated genome and the results of physiological
studies (Herlemann et al., 2009; Geissinger et al., 2009).
Research perspectives
In the next years, our focus will remain on the microbial
ecology of the termite gut and the metabolic capacities
of the microorganisms colonizing this habitat. Since the
majority of the bacteria in the hindgut of lower, woodfeeding termites are associated with the cellulolytic gut
flagellates, it is important to learn more about the metabolic link between the bacterial symbionts and their
eukaryotic partners, especially the putative role of the
ectosymbiotic Bacteroidetes in nitrogen metabolism. To
understand the evolutionary events leading to the endosymbiosis, we will also extend our investigations of the
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“Endomicrobia” to their closest free-living relatives present in all Dictyoptera, including cockroaches.
One of the major obstacles in termite gut research is
the inability to cultivate termites in the absence of their
complex gut microbiota. Recent phylogenetic studies
have revealed that termites are more closely related to
cockroaches than originally assumed. Despite their complex sociality and their unusual diet, they seem to be a
sister group of the cockroach family Blattidae, which includes well-known pest species like Blatta orientalis and
Periplaneta americana, that have reportedly been raised
in a germ-free environment. However, to date, the gut
Andreas Brune
microbiota of not a single cockroach species has been
analyzed with cultivation-independent tools.
Our preliminary findings indicate that several lineages
of bacteria specific to the termite gut have their closest
relatives in the cockroaches. This has important implications for the evolution of the termite gut microbiota
and will be followed up by a comprehensive analysis of
all major dictyopteran lineages. In addition, we successfully established the cockroach Shelfordella lateralis as a
model system for future gnothobiotic studies involving
the establishment of artificial microbial communities in
germ-free animals (Fig. 4).
Department of Biogeochemistry
Publications
Andert, J., Geissinger, O., Brune, A. (2008). Peptidic
soil components are a major dietary resource for the
humivorous larvae of Pachnoda spp. (Coleoptera, Scarabaeidae). J. Ins. Physiol. 54, 105–113.
Gross, E.M., Brune, A. & Walenciak, O. (2008). Gut
pH, redox conditions and oxygen levels in an aquatic
caterpillar: potential effects on the fate of ingested tannins. J. Ins. Physiol. 54, 462–471.
Köhler, T., Stingl, U., Meuser, K., Brune, A. (2008).
Novel lineages of Planctomycetes densely colonize the
alkaline gut of soil-feeding termites (Cubitermes spp.).
Environ. Microbiol. 10, 1260–1270.
Desai, M. S., Strassert, J. F. H., Meuser, K., Hertel, H.,
Ikeda-Ohtsubo, W., Radek, R., Brune, A. (2009). Strict
cospeciation of devescovinid flagellates and Bacteroidales
ectosymbionts in the gut of dry-wood termites (Kalotermitidae). Environ. Microbiol. (published online http://
dx.doi.org/10.1111/j.1462-2920.2009.02080.x).
Fig. 4. The cockroach Shelfordella lateralis is an excellent
model for gnothobiotic studies. Hatchlings can be raised germfree if the ootheceae are surface-sterilized before hatching
(Thompson and Brune, unpublished results).
Geissinger, O., Herlemann, D.P.R., Mörschel, E., Maier, U.G., Brune, A. (2009). The ultramicrobacterium
“Elusimicrobium minutum” gen. nov., sp. nov., the first
cultivated representative of the Termite Group 1 phylum. Appl. Environ. Microbiol. 75, 2831–2840.
Herlemann, D.P.R., Geissinger, O., Ikeda-Ohtsubo, W.,
Kunin, V., Sun, H., Lapidus, A., Hugenholtz, P., Brune,
A. (2009). Genomic analysis of “Elusimicrobium minutum,” the first cultivated representative of the phylum
“Elusimicrobia” (formerly Termite Group 1). Appl. Environ. Microbiol. 75, 2841–2849.
Ikeda-Ohtsubo, W., Brune, A. (2009). Cospeciation of
termite gut flagellates and their bacterial endosymbionts:
Trichonympha species and “Candidatus Endomicrobium
trichonymphae”. Mol. Ecol. 18, 332–342.
Strassert, J.F.H., Desai, M.S., Brune, A., Radek, R.
(2009). The true diversity of devescovinid flagellates
in the termite Incisitermes marginipennis. Protist 160,
522–535.
Ikeda-Ohtsubo, W., Faivre, N., Brune, A. (2010). Putatively free-living “Endomicrobia” – ancestors of the intracellular symbionts of termite gut flagellates? Environ.
Microbiol. Rep. (in press).
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Andreas Brune
Department of Biogeochemistry
Reviews
Ekschmitt, K., Kandeler, E., Poll, C., Brune, A., Buscot,
F., Friedrich, M., Gleixner, G., Hartmann, A., Kästner,
M., Marhan, S., Miltner, A., Scheu, S., Wolters, V.
(2008). Soil-carbon preservation through habitat constraints and biological limitations on decomposer activity. J. Plant Nutr. Soil Sci. 171, 27–35.
Melanie Zenker (2009) Charakterisierung des Bakteriums “Dysgonomonas rapiformis”, isoliert aus dem Darm
der Termite Reticulitermes santonensis (Universität Marburg)
Structure of the group (12/2009)
Brune, A. (2009). Methanogenesis in the digestive tracts
of insects. In: Handbook of Hydrocarbon and Lipid Microbiology, Vol. 1 (K. N. Timmis, ed.). Springer, Heidelberg, pp. 707–728.
Group leader: Prof. Dr. Andreas Brune
Brune, A. (2009). Symbionts aiding digestion. In: Encyclopedia of Insects, 2nd edn (V.H. Resh and R.T. Cardé,
eds.). Academic Press, New York, pp. 978–983.
PhD students: Oliver Geissinger, Tim Köhler,
Christine Schauer, James Nonoh (DAAD), Pinki Rani,
Jürgen Strassert (external, FU Berlin)
Finished theses
PhD theses
Postdoctoral fellows: Claire Thompson, David
Kamanda Ngugi, Mahesh Desai
Research associate: Nicolas Faivre
BSc student: Patrick Köhler
Herlemann, Daniel (2009) The candidate phylum “Termite group 1” – diversity, distribution, metabolism and
evolution of representatives of an unexplored bacterial
phylum (Universität Marburg)
Technical assistant: Katja Meuser
Desai, Mahesh (2008) Bacterial symbionts of termite
gut flagellates: cospeciation and nitrogen fixation in the
gut of dry-wood termites (Universität Marburg)
Deutsche Forschungsgemeinschaft, SFB-TR1 (TP A9)
“Endosymbiosis: From Prokaryotes to Eukaryotic Organelles”: Phylogeny and comparative genome analysis of
Endomicrobia, bacterial endosymbionts of termite gut
flagellates. Support for one postdoc (since 7/2006).
Ngugi, David Kamanda (2008) Transformation and mineralization of nitrogenous soil components in the gut of
soil-feeding termites (Universität Marburg)
Diploma/MSc theses
Tobias Wienemann (2008) Eine Symbiose mit drei Partnern: Bakterielle Symbionten von Trichonympha spp. in
niederen Termiten (Universität Marburg)
Nicolas Faivre (2008) Symbiontes procaryotes des
flagellés Trichonympha spp. chez le termite Hodotermopsis sjoestedti (Université Montpellier)
BSc theses
Bettina Buchmann (2009) Characterization of Breznakia globella gen. nov. sp. nov., the first representative of
a new lineage of Gammaproteobacteria (Universität Marburg)
Annika Quell (2009) Charakterisierung des Bakteriums
Clostridium Stamm ZT9 isoliert aus dem Darm der Termite Zootermopsis nevadensis (Universität Marburg)
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External funding
Deutsche Forschungsgemeinschaft (BR 1224/4-1): The
multiple symbioses of flagellates and their bacterial
endo- and ectobionts in dry-wood termites: an analysis
of ultrastructure, phylogeny and cospeciation. Together
with Renate Radek, FU Berlin, support for one graduate
student (since 1/2008).
Alexander von Humboldt Foundation: Support for one
postdoc (since 3/2009)
Deutscher Akademischer Austauschdienst (DAAD):
Support for two graduate students (until 10/2008; since
10/2009)
Andreas Brune
Department of Biogeochemistry
Invited lectures
Address
ASM General Meeting, Boston, Mass.
(01–05/06/2008)
Prof. Dr. Andreas Brune
Max-Planck-Institut für terrestrische Mikrobiologie
Karl-von-Frisch-Straße
35043 Marburg/Germany
12th ISME Conference, Cairns, Australia
(17–22/08/2008)
CSIRO Tropical Forest Research Centre, Atherton,
Australia (28/08/2008)
Phone: +49 6421 178-700
Fax: +49 6421 178-709
E-mail: [email protected]
School for Environmental Research, Charles Darwin
University, Darwin, Australia (05/09/2008)
International Symbiosis Society Congress, Madison,
Wisc. (9–15/08/2009)
NABU Ruhr, VHS Essen (04/11/2009)
Institut für Genetik und Mikrobiologie, Ludwig-Maximilians-Universität, München (17/11/2009)
Members of the Brune group and invited speakers of the lab retreat “Rheingau 2009” (16 – 20 May) during an oenological tour of
the wine cellars at the Research Institute Geisenheim. From right to left: Jürgen Strassert (FU Berlin), Dr. Claire Thompson, Sibylle
Franckenberg (LMU München), Prof. Dr. Andreas Brune (covered), Dr. Michael Pester (U Wien), Nicolas Faivre, Melanie Zenker (covered), Katja Meuser, Annika Quell, Dr. Janet Andert (U Uppsala), Dr. Mahesh Desai, Oliver Geissinger, Christine Schauer, Tim Köhler
(covered), Daniel Herlemann, Karen Brune (Science Editor, Ebsdorfergrund), Prof. Dr. Monika Christmann (Forschungsanstalt Geisenheim). Photographed by Dr. David Kamanda Ngugi.
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