Reactive oxygen species and nitrogen species (ROS and RNS), produced in a wide range of physiological process even under low oxygen availability, are among the main stressors found in the environment. Strategies developed to combat them constitute key features in bacterial adaptability and survival. Pseudomonas extremaustralis is a metabolic versatile and stress resistant Antarctic bacterium, able to grow under different oxygen conditions. The present work explores the effect of oxidative stress under low oxygen conditions in P. extremaustralis, by combining RNA deep sequencing analysis and physiological studies. Cells grown under microaerobiosis exhibited more oxidative damage in macromolecules and lower survival rates than under aerobiosis. RNA-seq analysis showed an up-regulation of genes related with oxidative stress response, flagella, chemotaxis and biofilm formation while chaperones and cytochromes were down-regulated. Microaerobic cultures exposed to H2O2 also displayed a hyper-flagellated phenotype coupled with a high motility behavior. Moreover, cells that were subjected to oxidative stress presented increased biofilm formation. Altogether, our results suggest that a higher motile behavior and augmented capacity to form biofilm structures could work in addition to well-known antioxidant enzymes and non-enzymatic ROS scavenging mechanisms to cope with oxidative stress at low oxygen tensions.
Keywords: Antioxidative enzymes; Biofilms; Chemotaxis; Low oxygen availability; RNA-seq; Reactive oxygen species.