To Örebro University

Biocides are crucial in industrial applications to minimize microbial growth and prevent product spoilage. Water-based construction coatings are susceptible to microbial contamination during manufacturing and storage and this adversely impacts product properties, reduces shelf-life and leads to substantial commercial losses. The future trend to lower the biocide concentrations in water-based coatings raises concerns about the emergence of biocide-resistant microbes. This study aims to identify and characterize the biocide-resistant microbe isolated from construction water-based coating materials to better understand its mechanisms of resistance. A total of 63 samples were collected from spoiled products, raw materials, and water from a manufacturing facility, and Pseudomonas oleovorans P4A were identified in all biocides-treated samples. A comparison between a P. oleovorans reference strain, 1045, and the P4A isolate revealed distinct colony morphology, growth rate and sensitivity to biocides and antibiotics. The P4A isolate was 3-fold more resistant to 5-chloro-2-methyl-isothiazolin-3-one (CMIT) and 1.5-fold more resistant to benzothiazolinone (BIT) compared to the reference strain. Conversely, it was 1.4-fold more sensitive to methylisothiazolinone (MIT) compared to the reference strain. No cross-resistance to antibiotics was observed. Metabolomic analysis using liquid chromatography combined with high-resolution mass spectrometry of lipids and polar metabolites showed that P4A had a relatively higher amount of lipids, while 1045 had a relatively higher amount of polar metabolites identified. A significant difference in lipid composition, specifically in diacylglycerol, phosphatidic acid, phosphatidylcholine, and phosphatidylserine was observed between P. oleovorans strains 1045 and P4A. These distinctions highlight increased lipid metabolism in P. oleovorans P4A and this may contribute to its adaptation to biocides. Microbial resistance can directly affect the effectiveness of these products, leading to an increased need for frequent maintenance and replacement, safety concerns, and environmental implications.