Postdoc at the Institute of Mineralogy and Physics of Condensed Matter (IMPMC), Paris

Genomic, transcriptomic and proteomic study of intracellular
biomineralization of calcium carbonates by cyanobacteria

Postdoctorate position 2 or 3 years

Institute of Mineralogy and Physics of Condensed Matter (IMPMC), Paris

European Research Council Starting Grant

Cyanobacteria are among the most important bacteria involved in the
interactions between the geosphere and the biosphere. They are
photosynthetic bacteria that appeared more than 2.3 billion years ago.
It is usually assumed that by fixing CO2 in the form of organic carbon,
they raise the pH of the environment and induce precipitation of calcium
carbonates. They may thus have had a major role in the formation of
carbonate rocks throughout Earth¢s history. Despite the geochemical
importance of cyanobacteria-mediated CaCO3 biomineralization, the
mechanistic details of this process are yet poorly understood.

Very recently, we discovered the existence of an early-diverging
cyanobacterial species, Candidatus Gloeomargarita lithophora, which can
form intracellular carbonates (Couradeau et al., 2012, Science). This
challenges all existing models of cyanobacterial calcification which
assumed that carbonate precipitation by cyanobacteria was exclusively
extracellular and was thus not controlled by the cells. We know almost
nothing about the phylogenetic distribution of this capability to
produce intracellular carbonates or about the involved biological
mechanisms. The study of molecular mechanisms involved in intracellular
biomineralization will have deep implications on our understanding of
how microbial communities interact with minerals in calcifying
environment and their impact on the global carbon cycle at the surface
of the Earth.

The present job will consist in studying these particular cyanobacteria
that are cultured in the laboratory and for which we have already
obtained their genome sequences. Different lines of research are
considered: 1) comparative genomics of intracellularly calcifying
strains (eventually including additional genomes of newly discovered
calcifying strains) with non-calcifying cyanobacteria to pinpoint
candidate genes involved in biomineralization; 2) search in sequenced
genomes for candidate genes potentially involved in biomineralization
and testing their role on carbonate precipitation by heterologous
expression in E. coli or any other pertinent model organism; 3)
transcriptomics of Gloeomargarita under two culturing conditions: one
allowing intracellular biomineralization and the other one not allowing
it; 4) extract proteins from intracellular inclusions of carbonates and
characterize these proteins by biochemical analysis to help testing the
role of specific proteins in biomineralization.

The candidate should have a strong experience in genomics,
transcriptomics and proteomics or at least in one of these fields,
ideally with a double formation in bioinformatics and wet laboratory
techniques. Most importantly, she/he should be motivated by working on
an interdisciplinary topic. She/he should have skills for working in a
team and supervising PhD students, conducting her/his research
autonomously and communicate her/his results in English.

The funding is for 2 or 3 years. It is provided by a Starting Grant from
the European Research Council (ERC). Employment will be arranged by the
administration of CNRS. The position can open as soon as January, 1st
2013 and should be filled no later than May 2013. Candidates should send
a detailed CV with a letter of motivation explaining the motivations for
this job to Karim Benzerara, Geobiology team at the Institute of
Mineralogy and Physics of Condensed Matter; karim.benzerara@impmc.upmc.fr

Purificacion Lopez-Garcia <puri.lopez@u-psud.fr>