Biologists from Irkutsk State University, together with colleagues from the University of North Florida (USA), studied the metabolism of Baikal actinobacteria, large microorganisms capable of synthesizing biologically active substances. It turned out that they lack genes for the enzymes common for this group, which are responsible for the production of antibiotics. This means that these microorganisms fight microbes with the help of other proteins and, possibly, compounds that are still unknown to science. The article was published in Aquatic microbial ecology. This work was supported by a grant from the Russian Science Foundation.
Actinobacteria are a class of bacteria of large size and complex shapes that have the ability to destroy toxic compounds that pollute the environment. They are producers of secondary metabolic products that they do not need for growth and development, but perform some other functions. Among these compounds are growth factors that stimulate various cellular processes and pheromones for "chemical communication". Man uses the property of these substances to suppress the growth of pathogenic bacteria and fungi, and uses them in medicine. In this work, scientists studied the formation of secondary metabolic products in 24 strains of actinobacteria isolated from the deposits of Lake Baikal. Scientists have compared it to processes in marine and freshwater organisms.
“Previous research has highlighted the ecology and geographic distribution patterns of actinobacteria from terrestrial and marine ecosystems. However, representatives of this class from freshwater sediments are still insufficiently studied,”says Maxim Timofeev, project manager for a grant from the Russian Science Foundation, Doctor of Biological Sciences, Director of the Research Institute of Biology of Irkutsk State University. Samples were recovered from the bottom of the lake at a depth of 200 meters. To obtain colonies of actinobacteria, the sediments were placed on a nutrient medium, which made it possible to suppress the growth of other microorganisms. Three days later, DNA was isolated from the colonies and, using molecular methods, it was determined whether there were genes specific for actinobacteria - this way you can make sure that the bacteria necessary for research have grown. In this case, and in the experiment itself, the DNA chains were "multiplied"because in the cell itself there is too little material for analysis, and artificial copying of the molecule solves the problem.
Researchers have paid attention to genes that are associated with the synthesis of biologically active compounds. They found that the isolated strains of Baikal actinobacteria lack the genes of FAD-dependent halogenases. These enzymes use the energy stored in FAD and are responsible for attaching to various halogen molecules such as chlorine and bromine. As a result, antibiotics such as tetracyclines, chloramphenicol and others are obtained. Most of the halogenases are found in marine microorganisms. The fact that they are absent in Baikal actinobacteria testifies to their adaptability to life in water with a low salt content. At the same time, biological activity was observed in 75% of the strains of actinobacteria isolated during the study. This means that it manifested itself at the expense of other enzymes.
“Common actinobacteria can incorporate halogen atoms into the chemical molecules they synthesize. The lack of this ability in Baikal actinobacteria is their unique difference, which speaks of the long evolution of these species in an ultrafresh environment. The peculiarities of Baikal actinobacteria allow us to speak about their significant potential for the production of antibiotics and natural compounds unknown to science,”says Maxim Timofeev.
Author: Alexey Paevsky