LAUSR

Abstract The objective of this work was to study the role of pyrroloquinolinequinone (PQQ) of Serratia sp. S119 strain in the maintenance of the bacterial redox state and in the early interaction with peanut. Lipid peroxidation and antioxidant enzymatic activities were analyzed in Serratia sp. S119 and in its PQQ minus mutant Serratia sp. RSL, exposed to hydrogen peroxide (H2O2). In the plant-bacteria interaction histochemical detection and quantification of H2O2 content was determined in peanut roots inoculated with the strains. The response to the oxidant agent showed significant differences between both studied bacteria. RSL showed growth decrease, lipid peroxidation increase and catalase enzyme activity reduction when the strain was exposed to H2O2. Also, a decrease in peroxidase activity was observed, regardless the presence or absence of this reactive species in this strain. The histochemical staining and quantification of ROS in peanut roots indicated an increase of H2O2 at 60 and 240 min postinoculation (pI) when plants were inoculated with RSL and S119 strains, respectively. In conclusion, PQQ would participate in the maintenance of cellular redox balance during oxidative stress in Serratia sp. S119 and, in the early recognition steps between this strain and peanut plant.