Transcript to view - British Antarctic Survey

MICROMAT : Biodiversity of Microbial Mats in Antarctic Lakes
De Wit R1, Dyer P2, Genilloud O3, Göttlich4, E, Hodgson D5, de Hoog S6, Jones B7, Laybourn-Parry J2, Marinelli F8,
9
10
10
11
Stackebrandt E , Swings J , Vyverman W , Wilmotte A
1. Biological Oceanography, University of Bordeaux 1, 33120 Arcachon, France. 2. Biological Sciences, University of Nottingham, Loughborough LE12 5RD, UK. 3. Merck-Sharp-
Dohme Espana, 28027 Madrid. 4. IWW, 45476 Mülheim, Germany. 5. British Antarctic Survey, CB3 OET Cambridge, UK. 6. Centraalbureau voor Schimmelcultures, 3740 AG Baarn,
Netherlands. 7. Genencor, PO Box 218, 2300 AE Leiden, Netherlands. 8. Biosearch Italia SPA, 21040 Gerenzano (VA), Italy. 9. DSMZ, 38124 Braunschweig, Germany. 10.
Microbiology/Protistology, University of Gent, 9000 Gent, Belgium. 11. Botany B22, University of Liège, 4000 Liège, Belgium.
Pigment extraction from the surface
sediments of lakes in the Larsemann
Hills (BAS, UK)
Close-up of the Benthic Gradient
Chamber (U.Bordeaux, Fr)
Tetramitus sp. (protozoa) from Lake
Pendant (U. Nottingham, UK)
Bacillariophyta
Chrysophyte
Chlorophyta
Apicomplexa
Cercomonad
Ciliophora
Zoomastigina
Euglenida
Rhizopoda
Fusarium sp. observed by Confocal
Laser Scanning Microscopy after
staining with nile red fluorescent dye
(IWW, DE)
A surface sediment core containing finelylayered microbial mats from Lake Nella in the
Larsemann Hills (BAS, UK)
Fungi
Heterotroph
Metazoa
Phototroph
Unidentified
Nematoda
Tardigrada
DGGE gel of fragments of the
cyanobacterial 16S rDNA from Lake
Fryxell and Ace Lake extracted during a
MICROMAT workshop (Ulg, BE)
Blast Similarity Search for 41 eukaryotic 18S rDNA
clones from Lake Fryxell (RUG/B, BE)
Robotic station for screening
(Biosearch, I)
Summary:
A recently started EC-biotech project concerning the biodiversity of microbial mats in the lakes of Antarctica is gathering scientists who will study the diversity of cultivated and 'yet-to-be cultivated ’
microorganisms (bacteria, fungi, protists), as well as their pigments, and three biotechnology companies who will screen strains isolated by their partners for useful compounds.
Materials and Methods:
Frozen and/or refrigerated material has been collected from three locations (Dry Valleys, Larseman Hills, Vestfold Hills) from lakes of different ages and physico-chemical characteristics. Morphological diversity
of cyanobacteria and protists was assessed by direct microscopic observation. Cultivation attempts were carried out for aerobic and anaerobic heterotrophic bacteria, cyanobacteria, protists and fungi. The ‘nonculturable’ portion of the mat environments was accessed by the isolation of environmental DNA that was used for the contruction of rDNA clone libraries and the performance of DGGE-TGGE. The Benthic
Gradient Chamber (1), a novel cultivation device mimicking natural gradients, has been successfully adapted to function at 5 °C, and measurement of O2 with microprobes could be done. Screening by HTS of
isolated strains for pharmaceutical compounds and cold-adapted enzymes is being carried out.
Results:
Surprisingly, the microbial diversity is very high, with a richness reminiscent of a rainforest. These mats are truly oases of diversity within a frozen desert and each new sample studied yields additional taxa.
Many bacterial taxa are new, although they are often related to established taxa from marine habitats in polar regions and elsewhere. The pigmented bacteria with high carotenoid content and the dark coloured
sheath of cyanobacteria illustrate the need of protection against UV radiation. Clone libraries of the cyanobacterial 16S sequences show that the clones retrieved from Lake Fryxell (Dry Valleys) and Ace Lake
(Vestfold Hills) belong to different taxa, and that the genotypic diversity was higher among the clones from Lake Fryxell. The distribution of the diatom taxa, observed by microscopy, was related to the bothe to
salinity and mat/substrate type: well-developed microbial mats harbouring different diatom communities than flake mats or sediments without mats. One unexpected finding was that the diversity was higher in
sediments of saline lakes, while well-developed microbial mats were least diverse, being dominated by only a few diatom taxa. Among the fungi, the psychrophilic ascomycete Thelebolus has been isolated from
many lakes, and to some extent Hyphozyma-like fungi, Fusarium, Curvularia and Phialophora as well as yeasts such as Mrakia frigida, Cryptococcus infirmominiatus and others. Slime production was strikingly
frequent among yeasts, and could be typical of cold environments. The widespread occurrence of the same protozoan genera, such as Euplotes, Halteria and Holotricha/Plagiocampa, as well as the high
incidence of amoeba in algal mats across the Antarctic continent are interesting. In all groups, only a minority of cultivated organisms exhibited a truly psychrophilic behaviour. Before a detailed characterization
of strains is possible a rapid sorting of hundreds of bacterial isolates was necessary. An analysis by FT-IR (Fourier Transform Infrared spectroscopy) was shown to discriminate clusters of bacterial strains at the
specific and intraspecific level (2).
Photosynthesis and respiration in the artificial mats of the BGC are optimal between 5-10°C, showing a good adaptation to the environment.
The mats in shallower lakes were shown to contain more UV-screening compounds (mycosporin-like molecules, scytonemin, carotenoids) and less chlorophyll than in deeper lakes.
Screening is still in progress, but preliminary results on bacterial isolates indicate only limited extra-cellular enzyme activity.
In conclusion: a higher than expected diversity is found in the microbial mats growing in the extreme conditions experienced in Antarctic lakes!
References:
(1) Pringault et al., 1996, FEMS Microbiology Ecology 20, 237-250
(2) Tindall et al., 2000, Environmental Microbiology, 310-318.
BIOTECH
Live Sciences and Technologies
Biotechnology Programme
(1994-1998)
http://europa.eu.int/comm/dg12/biot1.html
Contact person in Biotech unit:
[email protected]
Acknowledgements for samplings: Pip Noon (BAS), Gareth Murtagh, Ingmar Janse, Tracey Henshaw and Wendy Quayle (U. Nott.) with
assistance from Davis personnel (Mark Clear, Tony Morland and others), Kathy Welch (U.S. Antarctic Program).
Biotechnology unit - DG XII
European Commission
rue de la Loi, 200 / wetstraat, 200
B-1049 Bruxelles / Brussel
Belgique / België
Fax number: +32-2-299.18.60
E-mail: [email protected]