Topic of PhD thesis:
Role of microsymbionts in production of bioactive compounds (antifouling activity)
Microsymbionts are present in several invertebrate phyla, and they are considered
to be responsible for the production of bioactive substances. Daniela Blihoghe
is investigating the role of microsymbionts in the production of compounds
with biomedical potential (special focus: compounds with antifouling activity).
In addition to sponges and soft corals, she is studying the association of
bacteria with opisthobranchs. In this frame, she is working on the chemistry
and biochemistry (biosynthesis and characterization of the enzymatic activities
leading to the metabolites of interest) of these metabolites in Italy, while
she will focus on bioassays, bacteria isolation and characterization, etc.
in Israel. In Italy Daniela Blihoghe is working on extraction and fractionation
procedures, as well as on the characterization of the secondary metabolites
by NMR and MS methods.
Topic of PhD thesis:
Relationship between genetic biodiversity and chemical diversity
The interface between three disciplines such as ecology, genetics and chemistry
open a field capable to provide information on the relative contribution of
genetic and environmental factors to the natural variation and unravel their
relative contribution in shaping community and ecosystem diversity. Sponges
(phylum Porifera) hold a large diversity of natural products, many of which
are play an ecological role or show some degree of activity (ecological or
pharmaceutically oriented). Since the discovery of bacteria in sponge by Vacelet
(1975), it is widely accepted that many sponge species live in close association
with microorganisms, which has opened debates on the status of this relationship
and the origin of natural products. Charlotte Noyer is currently investigating
in the relationship between genetic, microbial, and chemical diversity in
the sponge Spongia agaricina. We know little about its biology, despite their
commercial (exploited as bath sponges) and putative pharmacological (rich
in secondary metabolites) characteristics. This sponge is collected in the
western Mediterranean Sea. Charlotte Noyer is developing microsatellite markers
to investigate the genetic variation between populations, their genetic structure,
dynamics, and the relationship between the natural chemical and bacterial
diversity with genetic diversity of the sponge and the communities that inhabit.
Quantification of microsatellite polymorphism will allow to establish allelic
richness and frequencies, heterozygoty, Fst values and to determine the genetic
structure, gene flux, and population size of this sponge. She is developing
DGGE (Denaturing gradient Gel Electrophoresis) techniques to identify the
microbial richness associated with the sponge, quantify their variation under
multiple conditions and investigate its relationship with ecological and chemical
diversity. She plans to develop quantitative PCR (Polymerase Chain Reaction)
techniques to accurately quantify microbial diversity in the sponge and HPLC
(High Performance Liquid Chromatography) and/or LCMS (Liquid Chromatography
Mass Spectroscopy) techniques to evaluate the chemical diversity of S. agaricina.
This study will shed light on the relationship between ecological, microbial,
and chemical diversity in sponges. This will set the background to further
advance on these relationships and unravel the role of genetic and environmental
factors on multiple levels of diversity associated with the sponge.
Topic of PhD thesis:
Chemical ecology of sponges and their associated microorganisms
Markus Haber focuses his research on the chemical mediators of marine ecological
interactions with sponges as one of the interacting partners. Sponges are
known to be rich of associated microorganisms and secondary metabolites. By
use of bioassays, organic chemistry, microbiological and molecular techniques
Markus Haber tries to identify the producer (either the sponge itself or an
associated microorganism) and the chemical compounds involved in a variety
of ecological interactions (e.g. biofouling, biofilm formation, predator-prey
relationships, and symbioses among others). Utilizing the high-throughput
screening centre at the University of Tel Aviv he is also testing the extracts
of sponges and their associated microorganisms in a number of applied assays
designed to identify new lead compounds and natural products for the use as
pharmacological drugs.
Topic of PhD thesis:
Elucidation of biochemical pathways - biosilica
Felipe Natalio is studying the biochemistry and potential applications of
the biosilica formimg sponge enzyme, silicatein, in nanobiotechnology. In
a first step he analyzed the proteome of the marine sponge Suberites domuncula
and the freshwater Lubomirska baicalensis by one-dimensional and two-dimensional
gel electrophoresis. The epression of proteins was studied in primmorph cultures
of S. domuncula using specific antibodies.
Silicatein is also able to form titania and zirconia from titanium and zirconium
alkoxide percursors. In a nonobiotechnological approach the polymerization
of silica using functionalized spicules linked to recombinant silicatein was
investigated. Felipe Natalio succeeded to immobilize recombinant silicatein
onto spicules from S. domuncula. He could also demonstrate the formation of
biosilica on the surface of the spicules catalysed by histidin-tagged silicatein.
Moreover, formation of layered titania and zirconia catalysed by surface bound
silicatein could be observed. The structures obtained were characterized by
SEM.
Topic of PhD thesis:
Apoptosis-related proteins in sponges
Bérengère Luthringer performed the first part of her PhD study at Mainz University
under the supervision of Prof. W.E.G. Müller and his team. In Mainz she worked
with an anti-apoptotic protein called survivin which is a negative regulator
of apoptotic caspases. Survivin is also thought to be involved in positive
regulation of cell cycle thus being in fact a bifunctional protein.
In the first part of her PhD work, Bérengère Luthringer elucidated the complete
cDNA sequence of the Suberites domuncula survivin-like protein and analyzed
the survivin expression pattern using Northern blotting technique and semi-quantitative
PCR. Survivin is expressed at a very low level, which is a characteristic
feature of this protein also in the human system, where it is detectable only
in highly proliferating cells such as tumor cells.
As a next step, she cloned a further anti-apoptotic sponge gene, a Bcl2 homolog
from the demosponge Lubomirskia baikalensis. Once again, she isolated the
complete cDNA and elucidated its sequence that features the family specific
BH domains (BH1 to BH4). In addition, the first caspase from S. domuncula
was identified and cloned.
The topic of the research of Bérengère Luthringer, the apoptosis mechanism,
is one of the scientific interests of the Tallinn team as well. To elucidate
the role of survivin in sponges, Bérengère Luthringer will use the model of
developing freshwater sponge Ephydatia fluviatilis. She has started with identifying
the survivin cDNA in E. fluviatilis; the cDNA library from E. fluviatilis
is under the construction.
Topic of PhD thesis:
Isolation and characterization of adhesive proteins
Echinoderms such as starfish and sea urchins use hydraulic structures known
as tube feet for a variety of functions including food capture, locomotion
and sensation. Early investigators proposed that tube feet used suction processes
to adhere to the substratum, based largely on the shape of tube feet in certain
starfish, sea urchins and holothurians. However, further investigation showed
that the tube feet were richly supplied with secretory cells at their apex
and that tube feet without modified “sucker” discs were also able to adhere
to substrates. Histochemical investigations showed that the secretions contained
basic proteins surrounded by glycosaminoglycans.
Malgorzata Baranowska began her studentship, which seeks to characterise the
footprint material in starfish tube feet and further develop this material
as a potential commercial adhesive, in September 2005. Since this time she
has learnt techniques for protein extraction and purification, including establishing
optimum buffer conditions for extraction and analysis, dialysis, electrophoresis,
blotting and HPLC. During her time spent at Integrin she has also built up
general knowledge about marine zoology and ecology, especially in field trips
for sample collection, where samples have been collected both in the inter-tidal
and by diving (she has obtained a basic diving qualification in the last year).
She has also learnt how to look after target species in the marine aquarium,
basic techniques of Atomic Force Microscopy (AFM) and standard light microscopy
of target material.
Topic of PhD thesis:
2-5A synthetases from marine sponges
Emilie Saby will elaborate procedures for the isolation and purification of
the protein(s) responsible for the 2-5A synthetase activity in a marine sponge
crude extract and use for the marine sponges Geodia cydonium and Chondrosia
reniformis. In parallel, she will elaborate novel assays for monitoring the
specific enzymatic activities during the protein purification process. The
amino acid sequences of the purified proteins will be determined. Based on
this information the primers will be designed and the corresponding cDNAs
will be cloned and expressed. The recombinant proteins will be studied for
their activity and activation mechanisms. The results will be compared to
those obtained previously with the recombinant 2-5A synthetase which had been
cloned from the cDNA library of Geodia cydonium with a mammalian 2-5A synthetase
probe.
The functional studies will be carried out in the lab at the Mediterranian
Sea (Blanes). The access to the fresh sponge material allows to localize both
the 2-5A synthetase mRNA and protein/activities in various sponge cell fractions.
The complex studies of the 2-5A synthetase during the development of a sponge
from larvae to adult organims and in the stress conditions will help to understand
the role of 2-5A synthetase in sponges. If possible, studies for its antiviral
activity in sponges will be performed. Depending on the time schedule, some
other organisms (e.g. corals) will be studied for their 2-5A synthetase activity.
Topic of PhD thesis:
Antimicrobial proteins in marine sponges
Johanna Frotscher will start her PhD work in Blanes in January 2007.
Topic of PhD thesis:
Formation of siliceous skeletons in marine sponges
Amélie Chatel will start her PhD work in Mainz in January 2007.
The aim of the research of Lada Lukic-Bilela is to investigate ecologically active metabolites with antifouling activity from sponges and mollusca. The focus on her research is on the adhesive proteins from the shells and constructing the chimeric proteins which can be able to connect on the different surfaces. The applications of these chimeric proteins can be various (medical implants, nanotechnology). The foot of the common mussels of the genus Mytilus produces a sticky glue that keeps the shelled organism anchored to rocks, allowing it to withstand the extreme pounding of waves. Chemical analyses have shown that the key to its adhesiveness is a unique compound called mussel adhesive protein (constituted mostly of collagen), which contains a high concentration of DOPA (dihydroxyphenylalanine), which can cling to wet surfaces with extraordinary strenght. Three full-lenght cDNA clones encoding the byssal collagenes, precollagen D (preCol-D), preCol-NG and pre Col-P recently have been isloted from M. edulis and M. galloprovincialis. We use a domain of preCol-D, called silk-fibroin. Furthermore, Lada Lukic-Bilela will continue and expand her investigation of the mitochondrial DNA (mtDNA) of Porifera, including interspecies analysis of polymorphisms in the intergenic regions (IGR) of mtDNA. The mtDNA analysis was the topic of her disertation where she has described and analysed the mitochondrial genom of Suberites domuncula.
Curriculum vitae