Effects of Chlorine Stress on Pseudomonas aeruginosa Biofilm and Analysis of Related Gene Expressions

Abstract

Chlorine is deployed worldwide to clean waters and prevent water-originated illnesses. However, chlorine has a limited disinfection capacity against biofilms. Microorganisms form biofilms to protect themselves from biological threats such as disinfectant chemicals. Pseudomonas aeruginosa is an opportunistic pathogen and its biofilm form attaches to surfaces, living buried into exopolysaccharides, can be present in all watery environments including tap water and drinking water. This research aimed to study the biofilm trigger mechanism of the opportunistic pathogen P. aeruginosa PAO1 strain, which is known to form biofilm in water supply systems and human body, under chlorine stress levels. In addition to biofilm staining, certain genes that are relevant to the stress condition were selected for gene expression analysis. The bacteria cultures were grown under chlorine stress with concentrations of 0.5, 0.7 and 1 mg/l. Six gene regions were determined related to biofilm and stress response: rpoS, bifA, migA, katB, soxR, and algC. Biofilm formation was analyzed by basic fuchsin staining, and gene expressions were quantified by quantitative real-time PCR. According to the results, highest biofilm production was observed in P. aeruginosa PAO1 wild strain under no stress conditions. Higher biofilm amounts were observed for bacteria under 0.5 and 0.7 mg/l chlorine stress compared to 1 mg/l chlorine stress.

Connected partner-switches control the life style of Pseudomonas aeruginosa through RpoS regulation

“…In Pseudomonas aeruginosa PAO1, the dependence of biofilm formation on RpoS is not as clear 7 . Biofilms formed in flow cell chambers are thicker in the absence of RpoS whereas under chlorine stress, the increase in RpoS is correlated to an increase in biofilm amount 8,9 .…”

Chlorine Tolerance and Inactivation of Escherichia coli recovered from Wastewater Treatment Plants in the Eastern Cape, South Africa

“…However, limitations in the use of chlorine include the production of off-tastes and odours, and potential formation of disinfection by-products (DBPs) such as trihalomethanes (THMs), Haloactic acids (HAAs), Haloacetylnitrile (HAN) and nitrosodimethylamine (NDMA) [13][14][15]. In addition, recovery of chlorine tolerant microbial pathogens at low chlorine dosages has been reported [16][17][18][19].…”

Disinfection Processes

“…(2016) used a semi-closed pipe-loop chloraminated DWDS simulator to evaluate biological stability of the system and describe the response of microbial communities in the bulk water and biofilm phase to a disturbance, including an episode of nitrification, followed by a chlorine burn by switching the disinfectant from chloramine to free chlorine. Kekeç et al (2016) studied the biofilm trigger mechanism of opportunistic pathogen P. aeruginosa PAO1 strain under several chlorine stress levels. Six gene regions were determined related to biofilm and stress response.…”