Title

Inhibition of bacterial multicellular behavior by natural brominated furanones

Date of Completion

January 2003

Keywords

Engineering, Chemical

Degree

Ph.D.

Abstract

The quorum sensing disruptor, (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2( 5H)-furanone (furanone) from the marine alga Delisea pulchra , was synthesized and used to study its effects on bacterial multicellular behavior (Gram-negative bacteria) as well as used to study its antimicrobial properties (Gram-positive bacteria). Furanone inhibited the growth, swarming motility, and biofilm formation of the Gram-positive Bacillus subtilis . In addition, furanone inhibited the corrosion of mild steel related to the corrosive, Gram-positive, sulfate-reducing bacterium, Desulfotomaculum orientis. DNA microarray results indicated that furanone induced the stress response in B. subtilis, and a B. subtilis clpC mutant was found to be more sensitive to furanone than the wild-type strain. ^ Furanone is not toxic to Gram-negative bacteria; however, it inhibited the swarming and biofilm formation of Escherichia coli, as well as siderophore synthesis of Pseudomonas putida F1. Furanone also inhibited the quorum sensing of Vibrio harveyi via autoinducer-1 and autoinducer-2 (AI-2), as well as the quorum sensing of E. coli via AI-2. Hence, this furanone is a non-specific intercellular signal antagonist. By studying with DNA microarrays, furanone was found to influence the same suite of genes controlled by AI-2 since 79% of the E. coli genes repressed by furanone were also induced by AI-2. Furthermore, three additional furanones were synthesized and were found to inhibit bacterial biofilm formation. ^ DNA microarray results indicated that the sporulation genes are induced in the wild-type B. subtilis biofilms and that the competence genes are induced in the biofilms of a B. subtilis sporulation mutant (ΔspoIIGB::erm). Based on these microarray results, a knockout B. subtilis mutant lacking the yveR gene (for polysaccharide synthesis) was constructed and was found to be defective in maintaining a biofilm. In contrast, genes for stress response and type I pili were induced in E. coli JM109 biofilms grown on glass wool as shown in microarray results. ^ In addition, a plant-derived biofilm inhibitor C110 (discovered by Sequoia Sciences, Inc.) was studied with DNA microarrays and found to induce the chemotaxis, motility, and heat shock genes of E. coli K12 at concentrations that are non-toxic. Addition of C110 to mature biofilms of E. coli JM109 caused biofilm removal. ^