Who has never read science fiction stories and never watched movies, in which space explorers travel through immense interstellar distances under artificial sleep conditions helping astronauts to keep their organisms unchanged for centuries? In fact, so-called anabiosis is common in nature, especially among microorganisms, which use it for surviving unfavourable conditions, e.g. drought or famine. However, it required decades for science to study this ability of small creatures. Perhaps we can point out two main problems, which scientists are trying to solve to move closer to the answer – first is why does cell vital activity retard many-fold, and, second, how does this phenomenon correspond to incredible environmental resistance of “sleeping” microorganism.
 

A few years ago the scientists have discovered that simple organic molecules (alkyl hydroxybenzene (AHB) derivates) accumulated in bacterial culture can make the cells fall into anabiosis. These compounds interact with lipids in bacterial membranes and harden the membrane, leaving microorganism in a tough “coffin” made of “frozen” membrane lipids. Such crystal-like membrane – “coffin” – is not just solid but also permeable for water and some ions, thus the cell is dehydrated intensively. However until recently the scientists couldn’t explain why there’s no enzymatic activity in the anabiotic cell. Are these compounds to blame? To prove this hypothesis the scientists from RAS Microbiology Institute decided to observe cell behaviour in the enzyme solution – model system imitating cell internal environment. AHB even in small concentrations (thousandths of percents) turned to hamper enzyme activity significantly.
 

They have various ways to do that. At some concentrations AHB molecules embed between enzyme molecule fragments and link its chains with hydrogen bonds. At larger concentrations AHB molecule tail embeds in protein molecule pockets or between oppositely charged groups of these molecules, interacts with them, and the enzyme appears to be coated. Enzyme molecules result in turning less active and more stable, thus reversibly losing their catalytic activity. What does it mean “reversibly”? If one breaks AHB-protein complexes, the enzymes will return to their spatial structure and recover their functions.
 

Another interesting effect of AHB-protein complexes is improving their resistance to damage. By binding with proteins AHB protect these delicate molecules from environmental impact, such as heating to 100 degrees and photo-oxidation. That is why AHB provide extreme stability of membranes and enzymes in bacterial spores, thus general spore stability against environmental impact.