Exposure to low UVA doses increases KatA and KatB catalase activities, and confers cross-protection against subsequent oxidative injuries in Pseudomonas aeruginosa

Abstract

Solar UVA radiation is one of the main environmental stress factors for Pseudomonas aeruginosa. Exposure to high UVA doses produces lethal effects by the action of the reactive oxygen species (ROS) it generates. P. aeruginosa has several enzymes, including KatA and KatB catalases, which provide detoxification of ROS. We have previously demonstrated that KatA is essential in defending P. aeruginosa against high UVA doses. In order to analyse the mechanisms involved in the adaptation of this micro-organism to UVA, we investigated the effect of exposure to low UVA doses on KatA and KatB activities, and the physiological consequences. Exposure to UVA induced total catalase activity; assays with non-denaturing polyacrylamide gels showed that both KatA and KatB activities were increased by radiation. This regulation occurred at the transcriptional level and depended, at least partly, on the increase in H 2 O 2 levels. We demonstrated that exposure to low UVA produced a protective effect against subsequent lethal doses of UVA, sodium hypochlorite and H 2 O 2 . Protection against lethal UVA depends on katA, whilst protection against sodium hypochlorite depends on katB, demonstrating that different mechanisms are involved in the defence against these oxidative agents, although both genes can be involved in the global cellular response. Conversely, protection against lethal doses of H 2 O 2 could depend on induction of both genes and/or (an)other defensive factor(s). A better understanding of the adaptive response of P. aeruginosa to UVA is relevant from an ecological standpoint and for improving disinfection strategies that employ UVA or solar irradiation.

Tolerance of Pseudomonas strain to the 2,4-D herbicide through a peroxidase system

“…This enzyme has two isoforms: KatA and KatB ( Fig 7 ). KatA, which is active in all growth phases and more related to the control of high concentrations of H 2 O 2 and KatB, which is active only in the presence of H 2 O 2 in Pseudomonas aeruginosa [ 41 ]. KatB provides resistance to exogenous hydrogen peroxide in P .…”

“…KatB provides resistance to exogenous hydrogen peroxide in P . aeruginosa [ 41 – 43 ]. For Pseudomonas sp.…”

Role of quorum sensing in UVA-induced biofilm formation in Pseudomonas aeruginosa

“…The cycling conditions for lasI , rhlI , lasR and rhlR genes were as follows: denaturation at 95 °C for 5 min; 40 cycles at 95 °C for 25 s, 58 °C for 15 s and 72 °C for 15 s. The same conditions were used for pelA and pslA amplification, except that the annealing temperature was 55 °C. The 16S rRNA gene was used as a reference for normalization of the expression levels of target genes under each condition [46]. Relative changes in the expression of individual genes between the treated and control conditions were obtained through the relative standard curve method [59].…”

“…The lethal effects of UVA radiation have been used for disinfection purposes in strategies such as SODIS (SOlar DISinfection of natural waters) and photocatalytic treatments [39, 40]. However, exposure to low doses of UVA induces several sublethal effects, such as a transient inhibition of bacterial growth without significant cell death [41], and loss of phage susceptibility [42], as well as adaptive responses related to the expression of genes related to DNA repair and antioxidative defence [43–46].…”

Tolerance of Pseudomonas Strain to the 2,4-D Herbicide through a Peroxidase System

“…KatA, which is active in all growth phases and more related to the control of high concentrations of H 2 O 2 and KatB, which is active only in the presence of H 2 O 2 in Pseudomonas aeruginosa [30]. KatB provides resistance to exogenous hydrogen peroxide in P. aeruginosa [30][31][32]. For Pseudomonas sp.…”