CC BY
0INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS" _25-26 SEPTEMBER, 2024_
EXO GENES OF RHIZOBIUMRADIOBACTER 36 AND THEIR
CHARACTERIZATION
1Togayev Sobit, 2 Rasulov Bakhtiyor A., 3 Pattaeva Mohichehra A.
1,2,3Institute of Genetics and Plant Experimental Biology, Uzbekistan Academy of Sciences, 111226, Kybray District, Tashkent Province, Uzbekistan https://doi.org/10.5281/zenodo.13847220
Bacteria of Rhizobium genus are characterized with synthesis exopolysaccharides (EPS), which play a crucial role in cell defense in abiotic stress, such as salinity, drought, heavy metals exposure etc. [1, 2]. Production of EPS by Rhizobium are controlled by a set of specific genes, such as exo genes [2]. The exo genes are a set of genes responsible for the biosynthesis, polymerization, and export of exopolysaccharides. The specific genes can vary depending on the Rhizobium strain. As reported in our previous research [2], a gene-cluster consisting of exoK and exoM are responsible for EPS macromolecule formation in R radiobacter.
In this research, it was aimed to identify exoM and exoK genes of bacterial strain R. radiobacter 36.
Identification and expression of EPS gene-cluster consisting of exoM and exoK was evaluated in different cultivation conditions. R. radiobacter 36 incubated in both 0% and 2.0% NaCl supplemented medium, and the cell biomass and EPS were isolated for further evaluation. Presence of 2.0% NaCl negatively impacts on expression EPS gene-cluster and EPS formation [2]. exoM and exoK genes were identified in this research (Figure). This finding correlates with our earlier study that out of a wide variety exo genes, namely exoM, exoK, exoT, exoW, exoS, only exoK and exoM are peculiar to R radiobacter species [2]. In presence of 2.0% NaCl the biomass formation and EPS synthesis decreased. This finding suggests that salt-stress down-regulates expression of exoM and exoK genes, and therefore the synthesis of EPS decreases. In conclusion, EPS biosynthesis by R. rhizobium 36 to be regulated by EPS gene-cluster consisting of two genes, exoM and exoK.
bp
1200
1000 900 800 700 600
1 2 3 4 5 6
Figure. Identification of exo genes of R. radiobacter 36 strain. 1 — markers; 2 — exoK (NaCl free); 3 — exoK (NaCl supplemented); 4 — exoM (NaCl free); 5 — exoM (NaCl supplemented);
6 — 16S RNA
In our previous research with another strain of the same species, namely R. radiobacter SZ4S7S14 exhibited identification of both exoK and exoM genes in salt-stress and these genes took part in the EPS macromolecular formation in presence of 2.0% NaCl [2]. Comparing two
INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE "STATUS AND DEVELOPMENT PROSPECTS OF FUNDAMENTAL AND APPLIED MICROBIOLOGY: THE VIEWPOINT OF YOUNG SCIENTISTS" _25-26 SEPTEMBER, 2024_
these strains, R radiobacter 36 and R radiobacter SZ4S7S14 it can be concluded that exoK and exoM genes expression depends genotypic peculiarities of the bacterial strains, which needs further elucidation with involvement of genome and RNA-transcriptome sequencing.
REFERENCES
1. Olenska, E., Malek, W., Kotowska, U., Wydrych, J., Polinska, W., Swiecicka, I., Thijs, S. and Vangronsveld, J., 2021. Exopolysaccharide carbohydrate structure and biofilm formation by Rhizobium leguminosarum bv. trifolii strains inhabiting nodules of Trifolium repens growing on an old Zn-Pb-Cd-polluted waste heap area. International Journal of Molecular Sciences, 22(6), p.2808.
2. Rasulov, B.A., Dai, J., Pattaeva, M.A., Yong-Hong, L., Yili, A., Aisa, H.A., Qiu, D. and Li, W.J., 2020. Gene expression abundance dictated exopolysaccharide modification in Rhizobium radiobacter SZ4S7S14 as the cell's response to salt stress. International Journal of Biological Macromolecules, 164, pp.4339-4347.
