GENOMIC AND PHYSIOLOGICAL STUDIES ON Pseudomonas syringae pv. syringae B728a UNDER LOW OXYGEN CONDITIONS.

BIANCHI FLORENCIA; RICARDI, MARTINIANO M.; IBARRA JOSE G.; LOPEZ NANCY I.; TRIBELLI PAULA M

Congreso; XVII Congreso Argentino de Microbiología General; 2022

The Pseudomonas genus has a wide metabolic versatility that allows bacteria to adapt to hangingenvironmental conditions, including variations in oxygen (O2) levels. The availability of O2 is relevantfor species of agricultural importance since the soil and the different plant tissues are environmentscharacterized by the presence of gradients. In Pseudomonas, the transition from aerobiosis toanaerobiosis is controlled by the global regulator Anr, which binds to consensus regions calledAnr-box. P. syringae pv. syringae B728a (B728a) is a foliar pathogen that causes bacterial brown spotin common bean (Phaseolus vulgaris), in other species of commercial importance and in the modelplant Nicotiana benthamiana. Genes involved in arginine fermentation, that produce ATP byphosphorylation at the substrate level in absence of oxygen, are present in the genome of B728a. Inthis work, the impact of O2 availability and the presence of L-arginine on important cellular functionsfor plant interaction were analyzed. B728a was capable of growing at low O2 conditions in L-argininesupplemented medium, thus microaerobic (M) and aerobic (A) cultures were used to investigate O2impact on B728a physiology. Arginine was found to promote biofilm formation in vitro and repress the swarming capacity of B728a. M cultures of B728a showed deficiencies in the early stages of foliarinfection of N. benthamiana, compared to A cultures, probably due to the lower resistance tooxidative stress of bacteria grown in microaerobic cultures, or by physiological differences affectingrelevant traits, such as envelopes or expression of virulence factors, under these growth conditions.At 72 h the virulence halos formed by bacteria from aerobic and microaerobic cultures presented asimilar area. Viable bacteria count indicated the presence of 2.8 x 103 CFU/cm2 from leavesinoculated with B728a (A) and 9.7 x 103 CFU/cm2 from leaves inoculated with B728a (M) (p