Scientists “revive” amoebas from the Arctic permafrost
Scientists from St. Petersburg State University (SPbU) and the Institute of Physicochemical and Biological Problems of Soil Science have discovered previously unknown species of amoebae in the Arctic permafrost and succeeded in “reviving” them. For the first time in the world, researchers were able to demonstrate that these organisms could be conserved in the frozen soil for tens of thousands of years, without losing the ability to “come back to life” after being thawed out and to integrate into the present-day microbial community.
Scientists from St. Petersburg State University (SPbU) and the Institute of Physicochemical and Biological Problems of Soil Science have discovered previously unknown species of amoebae in the Arctic permafrost and succeeded in “reviving” them. For the first time in the world, researchers were able to demonstrate that these organisms could be conserved in the frozen soil for tens of thousands of years, without losing the ability to “come back to life” after being thawed out and to integrate into the present-day microbial community.
Staying alive after 60,000 years
A joint team of researchers unifying SPbU scientists headed by Associate Professor Alexey Smirnov, and Liubov Shmakova, senior researcher from the Laboratory of Soil Cryology, the Institute of Physicochemical and Biological Problems of Soil Science (Russian Academy of Sciences) revived and investigated amoebae strains isolated from permafrost samples of different age and origin. Investigators were able to find the total of 26 strains of viable amoebae from the permafrost sediments sampled at the Gydan and Bykovsky peninsulars and Yana-Indigirka and Kolyma Lowlands at the Russian Arctic regions.
The study was conducted from 2012 to 2016 on the basis of SPbU laboratories, the Resource Centre “Culture Collection of Microorganisms” and “Centre for Molecular and Cell Technologies” from the Research Park of SPbU, and the Laboratory of Soil Cryology at the Institute of Physicochemical and Biological Problems of Soil Science (Pushchino, Moscow Region). Scientists described two new species of amoebae belonging to the genus Flamella. From the same samples Liubov Shmakova was able to isolate viable protists belonging to the genera Acanthamoeba, Acramoeba and Phalansterium, as well as representatives of amoeboid protists belonging to the class Heterolobosea. Eight of the isolated strains are still impossible to classify with certainty. The age of the microorganisms is 30,000-60,000 years.
Cysts will tell us about the evolution
Under adverse environmental conditions, a thick multi-layered protective covering is formed on the surface of amoeba cells. Thus, the amoeba goes into a dormant state by forming the so-called “cyst”, in which all life processes are much slowed down, nearly stopped. The cyst may be conserved for years or even decades without losing viability. However, no one could imagine that even many thousands of years in sub-zero temperatures is not the limit for amoeba cysts.
“It is this remarkable survivability that makes amoebae from Arctic permafrost sediments a very promising model for research,” said Associate Professor Alexey Smirnov. “The protozoa isolated from permafrost sediments give us a “snapshot” of evolution frozen in time. If we manage to find their direct descendants in present-day fauna of the same regions, we for the first time will be able to see how the genes of these microorganisms had changed during the 60,000 years of evolution and possibly to calibrate the “molecular clock” - a technique based on estimating the mutation rate in the genes of organisms, which allows us to date the most important evolutionary events.”
Naturally occurring layers of permafrost often break off the cliffs, river banks and sea coasts, and then melt down. Thus, the microorganisms conserved inside the ice have a chance to come “back to life” and to integrate into the present-day microbial community. How they are going to incorporate in it, is yet unknown. This is a completely new field of research.
The results of the study, according to Liudmila Chistiakova, Director of the SPbU Resource Centre “Culture Collection of Microorganisms”, draw the researchers’ attention to the promising method of cryogenic storage of protists. The study has confirmed that this way of preserving culture collections of unicellular organisms is much more economical and technologically convenient than the constant passages required to maintain cultures in the living and active state.
Amoebae in space
Since amoeba cysts isolated from permafrost sediments had demonstrated a unique ability to resist environmental impacts, they were chosen to participate in the Ekzobiofrost space experiment. The study was conducted in 2013 on the Bion-M1 satellite, with participation of the Institute of Physicochemical and Biological Problems of Soil Science. Amoeba cysts of the genus Acanthamoeba isolated from permafrost sediments aged 34,000 years were for a month exposed to the effects of deep space. “The post-flight analysis showed that 90% of the cysts were still alive, capable of excystment and further growth,” says Liubov Shmakova, senior researcher at the Institute of Physicochemical and Biological Problems of Soil Science. “These results, in particular, once again raise the issue of sterilisation of space missions launched to other planets in order to avoid mistaking tellurian organisms for alien life forms.”
Read more about the research in the article: Shmakova L. A., Rivkina E. M. , Bondarenko N. I., Smirnov A. V. Vital species of Flamella (Amoebozoa: Variosea) isolated from ancient Arctic permafrost sediments // Protist, 2016. Vol. 167, P. 13–30. DOI: 10.1016/j.protis.2015.11.001.