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Completed research project

Title / Titel FREDI: Functional Role and Ecotype DIvergence in freshwater ultramicrobacteria (09-EuroEEFG-FP013)
PDF Abstract (PDF, 14 KB)
Summary / Zusammenfassung FREDI:
Freshwaters systems are crucial in the turnover and remineralization of
organic carbon both from internal primary production and terrestrial
runoff. Microorganisms are centrally involved in both CO2 production and
consumption processes; they are responsible for most cycling of organic
matter and for the larger part of respiration in limnic systems. The
numerically abundant microbes in the freshwater plankton are
ultramicrobacteria with cell sizes of 1 micron and less. The high
abundances and cosmopolitan distribution of relatively few phylogenetic
lineages of ultramicrobacteria point to their evolutionary success and
functional significance at the ecosystem level. The least studied
ultramicrobacteria are affiliated with the LD12 clade, a sibling group
to a dominant bacterial lineage in marine surface waters. LD12 related
ribosomal RNA gene sequences have hitherto only been detected in
freshwater habitats, and there is limited information about their in
situ abundance, seasonality or metabolic traits. First surveys point to
the presence of LD12 in a wide range of systems and a key role of pH in
controlling their distribution and quantitative significance in lake
bacterioplankton. These bacteria are also believed to contain
light-harvesting pigments for energy generation, so-called
proteorhodopsins. We will study the population dynamics and
ecophysiological adaptations of different phylogenetic groups within the
LD12 lineage. In this context, we will analyze samples from a variety of
freshwater habitats with contrasting limnological properties. Moreover
we will conduct studies at high temporal resolution during the period of
highest LD12 abundances in Lake Zurich. Hypotheses about substrate
versatility or specialization from metagenomic analyses and metabolic
reconstructions of LD12 will be tested in situ. We will furthermore
collect sequence information of proteorhodopsin genes from bacteria
affiliated with LD12 from a variety of habitats. Since proteorhodopsins
from marine waters may be tightly tuned to the ambient light spectrum, a
comparative analysis of these genes focused on their adaptation to light
color will be performed. This will yield important additional
information about the local adaptation and phylogeography of LD12
bacteria. The project forms part of a consortium of scientists from
several European countries (Germany, Austria, Czech Republic) within the
framework of the EUROCORES Programme 'Ecological and Evolutionary
Functional Genomics' of the European Science Foundation. Its overall
goal is to elucidate the functional role and diversification in
different groups of freshwater ultramicrobacteria.
Project leadership and contacts /
Projektleitung und Kontakte
Prof. Dr. Jakob Pernthaler (Project Leader)
Dr. Hans-Peter Grossart  
Dr. Jan Jezbera
Prof. Stefan Bertilsson
Funding source(s) /
Unterstützt durch
SNF (Personen- und Projektförderung)
In collaboration with /
In Zusammenarbeit mit
Dr. Martin Hahn
Institute for Limnology
Herzog Odilostrasse 101
A-5310 Mondsee
Duration of Project / Projektdauer Aug 2010 to Jul 2013