Effects of N-acyl-L-homoserine Lactone Lactonase on Disruption of Preformed Biofilms, Bacterial Recruitment, and Prevention of Biofilms




Boswell, William T.

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Biofouling is the accumulation of biofilms on inanimate surfaces in aqueous environments. Biofouling can produce economic as well as medicinal consequences such as decreased flow efficiency of chemicals through pipes, increased drag on ships and interference with proper function of medical implants resulting in diseases. Bio films found in nature are typically composed of mixed species containing bacteria such as Pseudomonas aeruginosa. P. aeruginosa is normally found in soil and marine environments but is also an opportunistic pathogen of humans and lower eukaryotes. P. aeruginosa and many other organisms utilize a quorum-sensing pathway for cellular communication including the secretion o{acylated homoserine lactones (AHLs). Lactonases are enzymes naturally expressed by certain bacteria that have been found to disrupt ( quench) the AHL quorum-sensing pathway, but the effects of lactonase on biofilm stability and bacterial recruitment has not been well studied. In this study, wild type P. aeruginosa was co-cultured with DH5a. Escherichia coli containing a cloned lactonase gene, aiiA, from Bacillus thuringiensis under the control of isopropyl-P-Dthiogalactopyranoside {IPTG) inducible promoter to determine the effects of the AHL lactonase on biofilm stability and the effects on bacterial recruitment. Plate counts revealed that biofilm formation of PAOI and DH5a. E. coli pMAL-t-aiiA co-culture was thicker than when PAO 1 was grown in a monoculture. A moderately significant lower difference was observed when a 48-hour monoculture of PAOI was exposed to DH5a. E. coli pMAL-t-aiiA expressing lactonase when compared to exposure of PAO 1 to DH5a. E. coli pMAL-t-aiiA not expressing lactonase. Bacterial recruitment was not affected by the presence ofDHSa. E.coli pMAL-t-aiiA expressing lactonase. The results indicate that the lactonase has a small impact on bio:film stability but not bacterial recruitment.



Pseudomonas aeruginosa, Biofilms, Fouling, Fouling organisms


Boswell, W. T. (2007). <i>Effects of N-acyl-L-homoserine lactone lactonase on disruption of preformed biofilms, bacterial recruitment, and prevention of biofilms</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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