© Springer International Publishing Switzerland 2016 329
T. Sime-Ngando et al. (eds.), Lake Pavin, DOI 10.1007/978-3-319-39961-4_20
Molecular Diversity Studies in Lake
Pavin Reveal the Ecological Importance
of Parasitic True Fungi in the PlanktonTélesphore Sime-Ngando , Mélanie Gerphagnon ,
Jonathan Colombet , Marlène Jobard , Emilie Lefevre ,
Sébastien Monchy , Serena Rasconi , Delphine Latour ,
Jean-François Carrias , and Christian AmblardAbstract
Parasitism is one of the most common symbiotic interactions, occurring in almost all envi-
ronments. Microbial parasites are typically characterized by their small size, a short genera-
tion time, high rates of reproduction, and a simple life cycle usually completed within a
single host. Microbial parasites are phylogenetically diverse and ubiquitous in aquatic eco-
systems, comprising viruses, prokaryotes and eukaryotes. Pioneering environmental
18S-rDNA surveys of microbial eukaryotes in Lake Pavin, France, revealed the presence of
a high diversity of undescribed eukaryotes, primarily affi liated to the fungal phylum
Chytridiomycota (chytrids), and more than likely playing major roles as infecting agents in
the system. These early diverging fungi produce free-swimming dispersal propagules
characterized by a small size (2–8 μm) and a single, posterior fl agellum. These characteris-
tics make chytrids part of the so-called ‘zoosporic fungi’. Chytrids are particularly adapted
to a planktonic lifestyle and have been shown to infect a wide variety of hosts, including
fi sh, eggs, zooplankton, other aquatic fungi, and primarily phytoplankton in aquatic envi-
ronments. Related ecological implications are important for pelagic food webs. Released
organic particles resulting from the death of infected hosts can be used as substrates for
other microbial processes, and zoospores themselves can provide nutrient-rich particles for
planktonic grazers. The application of the plankton ecology group (PEG) model on Lake
Pavin indicated that chytrid epidemics could represent an important driving factor for phy-
toplanktonic seasonal successions. Besides, the observation that phytoplankton chytridio-
mycosis preferentially impacts larger size species (e.g., fi lamentous cyanobacteria) suggests
that bloom of such species may not represent a trophic bottleneck for the system as previ-
ously thought. In this chapter, based on studies we conducted in Lake Pavin and other lakes
in the vicinity, we summarize knowledge on diversity, community structure, quantitativeT. Sime-Ngando (*) • M. Gerphagnon • J. Colombet • M. Jobard
D. Latour • J.-F. Carrias • C. Amblard
LMGE, Laboratoire Microorganismes: Génome et Environnement ,
UMR CNRS 6023 , Université Clermont-Auvergne, Université
Blaise Pascal, BP 80026 , 63171 Aubière Cedex , France
e-mail: [email protected]
E. Lefevre
LMGE, Laboratoire Microorganismes: Génome et Environnement ,
UMR CNRS 6023 , Université Clermont-Auvergne, Université
Blaise Pascal, BP 80026 , 63171 Aubière Cedex , France
Present address: Department of Civil and Environmental
Engineering , Duke University , 121 Hudson Hall Box , 90287 ,
27708-0287 Durham , NC , USA
20
S. Monchy
LMGE, Laboratoire Microorganismes: Génome et Environnement ,
UMR CNRS 6023 , Université Clermont-Auvergne, Université
Blaise Pascal, BP 80026 , 63171 Aubière Cedex , France
Present address: INSU-CNRS, UMR 8187 LOG, Laboratoire
d’Océanologie et de Géosciences , Université du Littoral Côte
d’Opale, ULCO , 32 avenue Foch , F-62930 Wimereux , France
S. Rasconi
LMGE, Laboratoire Microorganismes: Génome et Environnement ,
UMR CNRS 6023 , Université Clermont-Auvergne, Université
Blaise Pascal, BP 80026 , 63171 Aubière Cedex , France
Present address: WasserCluster – Biological Station Lunz ,
Inter-university Centre for Aquatic Ecosystem Research ,
A-3293 Lunz am See , Austria