A phyllosphere-associated bacterial strain resistant to uv light

SANDOVAL NE; LANFRANCONI MP

Congreso; SAMIGE XVIII; 2023

Phyllosphere of Patagonian plants has been largely understudied, this environment is continually exposed to stressful conditions such as UV exposure, drought, and temperature fluctuations which makes it a promising place to find bacteria with new metabolites to apply in the industry. A yellow bacterial strain, named 44HA, was isolated from leaves of Olea europaea var. frantoio, showing tolerance to UV-light exposure. Our goal was to taxonomically identify this strain and analyze its resistance to UV-light. Whole-genome sequence was determined by Illumina technology, assembled with SPAdes and annotated with RAST and PATRIC. In order to assign this strain to a phylogenetic group, classic essential genes, e.g., 16S rDNA, rpoD and gyrB were analyzed. These studies showed the highest identity with Halomonas zhanjiangensis, however, the values obtained were not conclusive to assign 44HA to this species. Other comparative tools such as GGDC, TYGS and ANIb yielded the same results, consolidating the premise of a new species. When we explored the ability of the strain to tolerate UV light, our results demonstrated that 44HA has a survival rate of 30% after 15 minutes of exposure to UV-C. Based on largely reported photoprotective features of exopolysaccharides (EPS) and pigments, we reconstructed their synthesis pathways in Halomonas sp. 44HA. We found both, carotenoid and capsular EPS routes. We also found genes encoding enzymes associated with ROS like catalase, superoxide dismutase and glutathione peroxidase as well as enzymes involved in the reparation of DNA damage from UV such as photolyase. Carotenoids production was tested spectrophotometrically after pigment extraction, confirming that H. sp. 44HA produces them, as indicated by the characteristic peaks at 475nm and 450nm. Future studies will be directed to evaluate different growth conditions that could trigger H. sp. 44HA pigment production and also identify which carotenoid, among the great variety that exists, is present in this strain