Changes in fatty acid composition as a response to glyphosate toxicity in Pseudomonas fluorescens

Excessive use of herbicides decreases soil biodiversity and fertility. The literature on the xenobiotic response by microorganisms is focused on herbicide biodegradation as a selective event. Non-degradation systems independent of selection could allow the survival of tolerant bacteria in contaminated environments, impacting xenobiotic turnover and, consequently, bioremediation strategies. However, it is uncertain whether the response based on these systems requires selective pressure to be effective. The objective here was to analyze non-degradation phenotypes, enzymatic and structural response systems, of Pseudomonas fluorescens CMA-55 strain, already investigated the production pattern of quorum sensing molecules in response to glyphosate, not present at the isolation site. One mode of response was associated with decrease in membrane permeability and effective antioxidative response for 0–2.30 mM glyphosate, at the mid-log growing phase, with higher activities of Mn-SOD, KatA, and KatB, and presence of fatty acids as nonadecylic acid, margaric and lauric acid. The second response system was characterized by lower antioxidative enzymes activity, presence of KatC isoform, and pelargonic, capric, myristic, stearic, palmitoleic and palmitic acid as principal fatty acids, allowing the strain to face stressful conditions in 9.20–11.50 mM glyphosate at the stationary phase. Therefore, the bacterial strain could modify the fatty acid composition and the permeability of membranes in two response modes according to the herbicide concentration, even glyphosate was not previously selective for P. fluorescens, featuring a generalist system based on physiological plasticity. Graphical representation of the main results showing the different response systems to the glyphosate herbicide of Pseudomonas fluorescens CMA-55 7729. This strain originated from biofilms formed in water storage tanks used for washing herbicide containers. No glyphosate container was washed with this water. The left panel represents the enzymatic responses with high activity of Mn-SOD and KatA, and KatB isoenzymes; and specific fatty acids produced at 0x, 1x, and 10x glyphosate concentrations, with high viability rates. The right panel represents the enzymatic responses with low activity of Mn-SOD and KatA, KatB, and KatC isoenzymes; and different fatty acids produced at 40x and 50x glyphosate concentrations, with low viability rates. [Display omitted] Herbicide; Oxidative enzyme; Physiological