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Objective(s): Alginates play a key role in mucoid Pseudomonas aeruginosa colonization, biofilm formation, and driving out of cationic antibiotics. P. aeruginosa alginate lyase (AlgL) is a periplasmic enzyme that is necessary for alginate synthesis and secretion. It also has a role in depolymerization of alginates. Using AlgLs in cystic fibrosis patients along with antibiotics enhances bacterial killing and host healing. In this study, we investigated the different biochemical properties of a newly isolated AlgL from P. aeruginosa S21 to complete the databank of AlgLsMaterials and Methods: The enzyme was extracted from the periplasmic space of the bacteria by the heat shock method. Using the TBA method, the enzyme activity and biochemical properties were assessed. The mutability of P. aeruginosa S21 AlgL to increase its thermal stability was investigated. The most favorable mutations were studied computationally. The molecular dynamics simulation (MDS) package GROMACS was used for determining the effect of S34R mutation on enzyme’s thermal stability.Results: Data showed that this enzyme has the best activity at 37 °C and pH 7.5 and it can degrade mannuronate blocks, guluronate blocks, and sodium alginate. After 7 hr at 80 °C, 45% of the enzyme activity was retained. This enzyme needed 15 min to completely degrade accessible sodium alginate. Tris buffer, pH 8.5 and Britton-Robinson buffer, pH 7.0 were the preferable buffers for the enzyme activity. MDS of native and mutated enzymes showed desirable results.Conclusion: P. aeruginosa S21 AlgL can be used in medical and industrial applications to degrade alginates.

Objective(s): Pseudomonas aeruginosais a Gram-negative and aerobic rod bacterium that displays mucoid and non-mucoid phenotype. Mucoid strains secrete alginate, which is the main agent of biofilms in chronic P. aeruginosa infections, show high resistance to antibiotics; consequently, the biological disruption of mucoid P. aeruginosa biofilms is an attractive area of study for researchers. Alginate lyase gene (algl) is a member of alginate producing operon which by glycosidase activity produces primer for other enzymes in this cluster. Also this activity can destroy the extracellular alginate; therefore this enzyme participates in alginate production and destruction pathway. Alginate lyase causes detachment of a biofilm by reducing its adhesion to the surfaces, and increases phagocytosis and antibiotic susceptibility. In this study, alginate lyase was purified in just one step and its properties were investigated. Materials and Methods: The purification was done by affinity chromatography, analysed by SDS-PAGE, and its effect on P. aeruginosa biofilms was surveyed by micro titer plate assay and SEM. The substrate specificity of the enzyme was determined by PCR. Results: Alginate lyase from isolate 48 was purified in one step. It is more thermally resistant than alginate lyase from Pseudomonas aeruginosa PAO1 and poly M, poly G and poly MG alginate were the substrate of this enzyme. Moreover, it has an eradication effect on biofilms from P. aeruginosa 48 and PAO1. Conclusion: In this study an alginate lyase with many characteristics suitable in medicine such as thermal stability, effective on poly M alginate, and bacterial biofilm destructive was introduced and purified.

Objective(s): Pseudomonas aeruginosa is a nosocomial pathogen resistant to most antimicrobial treatments. Furthermore, it persists in adverse environments thereby forming biofilms on various surfaces. Researchers have therefore focused on antibiofilm strategies using nanoparticles due to their unique physicochemical properties. Superparamagnetic iron oxide nanoparticles (SIONPs) have recently shown to possess antimicrobial and anti-biofilm characteristics. In this study, the effects of SIONPs and some antibiotics were tested against strong biofilmproducing P. aeruginosa isolates.Materials and Methods: 60 isolates of P.aeruginosa were screened for biofilm formation on microtiter plates using 0.1%w/v crystal violet (CV) staining. Twenty isolates producing strong biofilms were selected for further study on the effects of antimicrobial agents. Microdilution method was used to assay twenty isolates susceptible to antibiotics. The effects of antibiotics and SIONPs on biofilm formation were determined by the microdilution method and 0.1% CV staining. The checkerboard dilution technique was used to determine the combined effects of SIONPs and imipenem. Results: In twenty isolates, the rate of resistance to ciprofloxacin, levofloxacin, amikacin, azithromycin was 65, 75, 45 and 95% respectively. SIONPs at 30 µg/ml reduced biofilm biomass in 11 isolates; however it stimulated biofilm formation in 9 isolates. The effects of SIONPs in combination with imipenem in the 10 isolates were different exhibiting synergistic or antagonistic relationships.Conclusion: P. aeruginosa has increasingly developed resistance to many antimicrobial agents but the resistance to nanoparticles is less frequently been reported. However, iron oxide nanoparticles could enhance biofilm production in isolate- dependent manner because they may possibly utilize this nanoparticle as an iron source, an important element in biofilm production. The exact mechanism of these effects however, remains to be elucidated.