Pseudomonas aeruginosainactivation mechanism is affected by capsular extracellular polymeric substances reactivity with chlorine and monochloramine

Abstract

The reactivity of capsular extracellular polymeric substances (EPS) to chlorine and monochloramine was assessed and compared in this study. The impact of capsular EPS on Gram‐negative bacteria Pseudomonas aeruginosa inactivation mechanisms was investigated both qualitatively and quantitatively using a combination of batch experiments, viability tests with LIVE/DEAD staining, and Fourier transform infrared spectroscopy (FTIR). Both wild‐type and isogenic mutant strains with different alginate EPS production capabilities were used to evaluate their susceptibility to chlorine and monochloramine. The mucA22 mutant strain, which overproduces the EPS composed largely of acidic polysaccharide alginate, exhibited high resistance and prolonged inactivation time to both chlorine and monochloramine relative to PAO1 (wild‐type) and algT(U) mutant strains (alginate EPS deficient). Multiple analyses were combined to better understand the mechanistic role of EPS against chlorine‐based disinfectants. The extracted EPS exhibited high reactivity with chlorine and very low reactivity with monochloramine, suggesting different mechanism of protection against disinfectants. Moreover, capsular EPS on cell membrane appeared to reduce membrane permeabilization by disinfectants as suggested by deformation of key functional groups in EPS and cell membrane (the C–O–C stretching of carbohydrate and the C=O stretching of ester group). The combined results supported that capsular EPS, acting either as a disinfectant consumer (for chlorine inactivation) or limiting access to reactive sites on cell membrane (for monochloramine inactivation), provide a protective role for bacterial cells against regulatory residual disinfectants by reducing membrane permeabilization.

Recovery ofPseudomonas aeruginosaculturability following copper- and chlorine-induced stress

“…A representative concentration of free chlorine found in drinking water distribution systems was selected to reach a target concentration of < 0.1 mg Cl 2 L −1 after 24 h. Figure shows the loss of culturability (final to initial CFU mL −1 , N / N 0 ) of P. aeruginosa as a function of exposure to free chlorine expressed as the product of concentration and contact time (also expressed as C t in the literature) observed during the first 24 h. Similar data at lower exposure to chlorine values reported by Xue et al . () are also presented. increased initial rates of apparent inactivation of culturable P. aeruginosa by chlorine have been documented in batch and chemostat experiments (Behnke et al ., ; Xue et al ., ) showing large reductions (3.5–6 log) at initial free chlorine dosage of ≤ 1 mg Cl 2 L −1 .…”

Differential Protection from Tobramycin by Extracellular Polymeric Substances from Acinetobacter baumannii and Staphylococcus aureus Biofilms

“…The bEPS of P. aeruginosa is polysaccharide rich and consequently was thought to provide protection by decreasing diffusivity or otherwise excluding antibiotic access to the cell (30). P. aeruginosa bEPS is also effective in counteracting chlorine and monochloramine disinfectants, reducing their availability and prolonging cell life (31). A multidrug-resistant strain of A. baumannii produces bEPS in abundance compared to a drugsensitive strain (32).…”

Membrane biofouling characterization: effects of sample preparation procedures on biofilm structure and the microbial community

“…Active nitrifiers are commonly located in the surface layers of nitrifying biofilms (Schramm et al 2000;Laspidou & Rittmann 2004), and they excrete more proteins than polysaccharides with a protein/sugar ratio of 2-5, as previously reported (Liang et al 2010). In other cases such as Pseudomonas aeruginosa, polysaccharides can be produced at higher levels than proteins (Xue et al 2013). Therefore, depending on the distribution of specific microbial populations within biofilms, the effects of the rinsing procedure on the EPS composition and distribution may vary greatly.…”