Effect of aeration conditions on growth and leaf infection of Pseudomonas syringae pv. syringae B728a

BIANCHI, F.I.; LÓPEZ, N.I.; RICARDI,M.M.; TRIBELLI, P.M.; IBARRA J.G.

Congreso; V Congreso Argentino de Microbiología Agrícola y Ambiental (CAMAYA); 2021

In Pseudomonas anaerobic metabolism is controlled by the regulator Anr, which binds to thepromoter region of target genes, called Anr-box. P. syringae is a plant pathogen that includesmany pathovars. P. syringae pathovars are considered aerobes due to the lack of genes involvedin nitrate reduction and arginine fermentation. However, P. syringae pv syringae B728a (B728a)possess the arginine deiminase pathway with an Anr-box upstream of arcD. The aim of this workwas to analyze the effect of low oxygen conditions on B728a growth and infection ability using theplant model Nicotiana benthamiana. Anr regulon comparison in different plant associatedPseudomonas species was done focusing on genes involved in virulence or plant interaction.B728a was grown in 0.5NE2 medium supplemented with 1% glucose and 50 mM of arginine.Microaerobic cultures (M) were incubated in sealed bottles without agitation while aerobic cultures(A) were incubated in Erlenmeyer flasks at 200 rpm. N. benthamiana leaves were inoculated with100 µl of cultures at OD 600nm= 0.5. After 16 and 72 h post-inoculation (hpi), the virulence halosdiameter was measured and bacterial counts (CFU/ml) were performed on cetrimide agar plates.Additionally, H 2 O 2 disk assays and DNA agar, milk agar and blood agar plates were used tomeasure oxidative stress and activities halos. Anr-boxes were predicted using PRODORICplatform.At 16 hpi most of the leaves inoculated with B728a M did not present virulence halos but thoseinoculated with B728a A did, while at 72 hpi halos showed no significant differences (t-Student test;P>0.05). At 72 hpi, 2667±1115 CFU/ml in the leaves inoculated with A and 9244±3598 CFU/ml inthose inoculated with M were observed, showing significant differences between aerationconditions (P