“Most of what is easily accessible has in principle already been discovered,” said Dr. Ivan Berg from the University of Freiburg, explaining why he is investigating the metabolic pathways in extremophilic microorganisms. The researcher and his team are interested in the biochemistry of organisms living in hot volcanic springs and the Dead Sea. Examples of this are two metabolic pathways which the researchers from Freiburg discovered in organisms belonging to the Crenarchaeota. The bacteria use the pathways to assimilate atmospheric carbon dioxide without the risk of poisoning themselves with the breakdown products arising at high temperatures. What can industry learn from extremophilic bacteria? What are the advantages and disadvantages for laboratory applications? And what can we learn from them about evolution on Earth?
Plants take up CO2 and convert it into sugar as part of the Calvin cycle during photosynthesis. However, many microorganisms cannot make use of this reaction pathway, in particular those that live in inhospitable corners of the Earth like volcanic springs in temperatures of up to 120°C. The reason for this is that some of the intermediary products of the Calvin cycle break down into toxic products at high temperatures that can kill cells. The unicellular organisms within Archaea that are several billion years old and have adjusted to life under extreme conditions have evolved other biochemical solutions to solve the problems that occur in Earth’s “hot spots”. “I am looking for new metabolic pathways,” said Dr. Ivan Berg, head of a group of researchers in the Department of Microbiology at the Institute of Biology II at the University of Freiburg. “I am also interested in the evolution of these metabolic pathways and their ecological importance for the respective organisms.”
Berg’s team of researchers are mainly focused on basic research, but they are also interested in the implication of their findings for industry. Lipid-degrading enzymes isolated from thermophilic bacteria have long been used in detergents because of their ability to remove oil at high temperatures. However, enzymes that are effective at low temperatures are increasingly gaining in importance as they have the potential to achieve the desired washing results at lower temperatures and hence consume less energy. There are many examples of the industrial application of such enzymes. However, such issues are not of the highest priority for Berg who is specifically interested in discovering new things and obtaining a global picture. During his postdoctoral period in the laboratory of the microbiologist Prof. Dr. Georg Fuchs from Freiburg, Berg discovered two new metabolic pathways in the Crenarchaeota, one of the two subgroups of Archaea, which use these pathways for the assimilation of carbon dioxide into more complex compounds such as sugar and proteins.
One thing is clear: the two newly discovered metabolic cycles are optimised for high temperatures. They generate no toxic breakdown products that could damage the bacterial cells. However, the enzymes’ resistance to high temperatures is a double-edged sword when used in the laboratory. “In order to investigate the proteins and metabolic products at the point at which they exert their optimal effect, we need to apply very high temperatures of around 80°C. And this requires expensive equipment and specific materials that can tolerate such high temperatures,” said Berg. On the other hand, the model organism E. coli can be used to produce highly pure crenarchaeal enzymes. “The only thing we have to do is to heat the E. coli cell extract to 80°C, which causes all proteins that do not tolerate such high temperatures to denature,” Berg explained going on to add, “many researchers do not like working with extremophilic bacteria because of the associated disadvantages in terms of expensive equipment etc.,” Berg said. “However, everything that used to be easily accessible has now been discovered. This is why I am now doing research involving extremophilic bacteria,” Berg said, stating that he feels it is now necessary for researchers to increasingly focus on the exotic if they want to make new discoveries. “If I lose some money, I will look for it where I have lost it, and not just in places where there is light, although it is good to have light,” Berg concluded.
It is often only after the basic research work has been completed that new ideas for industrial or environmental applications arise. This is what Berg’s discovery of the aerobic CO2 fixation cycle in Metallosphaera sedula clearly shows. In the meantime, genome analyses have shown that the Thaumarchaeota bacteria, which account for around 20 percent of the microbial biomass in the oceans, also possess this particular metabolic pathway. It can therefore be assumed that this metabolic pathway is also involved in the growth of the global biomass and in the carbon cycle in the biosphere. Therefore, Berg’s findings are far from just exotic knowledge. In addition to focusing on other basic research projects, Berg and his team of researchers are now planning to look at the biochemistry of the Thaumarchaeota bacteria in greater detail.
Dr. Ivan Berg
Department of Microbiology
Institute of Biology II
University of Freiburg
Tel.: +49 (0)761/ 203 2777