Gene clusters involved in the biofilm formation of Escherichia hermannii

Abstract

Genes involved in promoting biofilm formation of Escherichia hermannii strain 11-2, a clinical isolate from a persistent apical periodontits lesion, were identified using EZ-Tn 5™<KAN-2> transposon mutagenesis. Biofilm-defective mutants were isolated by measuring viscosity of spent culture media from 486 kanamycin resistant mutants of strain 11-2. Six mutants that did not produce viscous materials were obtained and a single insertion of transposon on their genomes were confirmed by Southern analysis. Sequencing of the EZ-Tn 5™<KAN-2> transposon flanking sequences of six mutants revealed that all insertions were located on gene clusters for lipopolysaccharide synthesis and transport. Only mutant strain 455, with an insertion of transposon in wzt (one of the ABC-transporter genes) lost capacity to produce viscous material and to form meshwork-like structures around the cells. These results suggest that gene clusters for lipopolysaccharide synthesis might be involved in the biofilm formation of this organism, and in particular, that wzt might play a crucial role in this biofilm formation.