Thus, there is evidence that free radical production (superoxide O2 -, hydrogen peroxide H2O2, or hydroxyl radical HO-) in bacterial cells is stimulated at low temperatures, apparently in an iron-independent manner. Therefore, the expression of oxidative stress adaptation genes, such as catalases, increase considerably [48, 49]. A similar response may occur in

our strain, justifying the observed induction in the catalase gene, as low temperature induces free radical production in cells, in turn increasing catalase production. The expression of the gene encoding catalase PF-01367338 nmr (KatB) was evaluated by RT-PCR analysis (Figure 3). Furthermore, it has been reported that iron-starvation inducible genes are also induced in response to oxidative stress in P. aeruginosa. This response appears to be due to a transient loss of Fur repressor function [50]. These observations are consistent with our data and support our hypothesis about the inactive status of the Fur protein at low temperatures. Additionally, within Cluster 6, we also found PSPPH_1309,

which encodes the cysteine desulfurase IscS, and PSPPH_1311, ARS-1620 which encodes iron-sulfur cluster assembly protein IscA, both components of ISC (iron-sulfur cluster) system essential in the biogenesis of iron-sulfur (Fe-S) proteins in bacteria. It has been observed that some pathways involved in Fe-S cluster assembly operate under iron starvation and oxidative

stress conditions [51, 52], which agrees with the results obtained. On the other hand, several reports have indicated a correlation exists between the uptake-transport iron system and motility process and biofilm formation. Thus, iron deficiency stimulates twitching motility, a form of surface motility that is inconsistent with microcolonies and biofilm formation [53]. This is consistent with the results obtained in our experiments, because iron metabolism genes and siderophores production are induced, simulating iron deficiency conditions, and motility processes appear to be favored, whereas biofilm or extracellular polysaccharide formation is decreased (see data below). Hypothetical proteins and proteins with unknown function are induced at 18°C Among the differentially regulated genes induced PLEK2 at 18°C, we found 15 genes that hypothetically encode conserved proteins (Cluster 7). Additionally, Cluster 8 has genes that could not be grouped into any specific biological process but showed high transcript levels at 18°C relative to 28°C. Within this cluster are genes encoding various transcriptional regulators, a gene that encodes an ATP-dependent helicase, DinG family (PSPPH_1406), and the PSPPH_4151 gene that encodes RNA polymerase sigma-54 factor RpoN whose expression was validated by RT-PCR assays (Figure 3). Low temperature represses alginate Osimertinib supplier synthesis in P. syringae pv.