EST-analysis of the thermo-acidophilic red microalga Galdieria sulphuraria reveals potential for lipid A biosynthesis and unveils the pathway of carbon export from rhodoplasts.
When we think of extremophiles, organisms adapted to extreme environments, prokaryotes come to mind first. However, the unicellular red micro-alga Galdieria sulphuraria (Cyanidiales) is a eukaryote that can represent up to 90% of the biomass in extreme habitats such as hot sulfur springs with pH values of 0-4 and temperatures of up to 56 degrees C. This red alga thrives autotrophically as well as heterotrophically on more than 50 different carbon sources, including a number of rare sugars and sugar alcohols. This biochemical versatility suggests a large repertoire of metabolic enzymes, rivaled by few organisms and a potentially rich source of thermo-stable enzymes for biotechnology. The temperatures under which this organism carries out photosynthesis are at the high end of the range for this process, making G. sulphuraria a valuable model for physical studies on the photosynthetic apparatus. In addition, the gene sequences of this living fossil reveal much about the evolution of modern eukaryotes. Finally, the alga tolerates high concentrations of toxic metal ions such as cadmium, mercury, aluminum, and nickel, suggesting potential application in bioremediation. To begin to explore the unique biology of G. sulphuraria , 5270 expressed sequence tags from two different cDNA libraries have been sequenced and annotated. Particular emphasis has been placed on the reconstruction of metabolic pathways present in this organism. For example, we provide evidence for (i) a complete pathway for lipid A biosynthesis; (ii) export of triose-phosphates from rhodoplasts; (iii) and absence of eukaryotic hexokinases. Sequence data and additional information are available at http://genomics.msu.edu/galdieria.
Weber
Andreas P M
AP
Department of Plant Biology, Michigan State University, USA.
Oesterhelt
Christine
C
Gross
Wolfgang
W
Bräutigam
Andrea
A
Imboden
Lori A
LA
Krassovskaya
Inga
I
Linka
Nicole
N
Truchina
Julia
J
Schneidereit
Jörg
J
Voll
Hildegard
H
Voll
Lars M
LM
Zimmermann
Marc
M
Jamai
Aziz
A
Riekhof
Wayne R
WR
Yu
Bin
B
Garavito
R Michael
RM
Benning
Christoph
C
D020418:Algal Proteins / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism*; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics; D020224:Expressed Sequence Tags; D005227:Fatty Acids / Q000378:metabolism; D015723:Gene Library; D006593:Hexokinase / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D008050:Lipid A / Q000096:biosynthesis*; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D010101:Oxygen Consumption; D028061:Phosphate Transport Proteins / Q000235:genetics; D010788:Photosynthesis / Q000235:genetics; D010802:Phylogeny; D018087:Plastids / Q000378:metabolism*; D000461:Rhodophyta / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature
D020418:Algal Proteins; D018076:DNA, Complementary; D005227:Fatty Acids; D008050:Lipid A; D009004:Monosaccharide Transport Proteins; D028061:Phosphate Transport Proteins; D002244:Carbon; D006593:Hexokinase