Analysis of the Lateral Flagellar Gene System of Aeromonas hydrophila AH-3

Abstract

ABSTRACT Mesophilic Aeromonas strains express a polar flagellum in all culture conditions, and certain strains produce lateral flagella on semisolid media or on surfaces. Although Aeromonas lateral flagella have been described as a colonization factor, little is known about their organization and expression. Here we characterized the complete lateral flagellar gene cluster of Aeromonas hydrophila AH-3 containing 38 genes, 9 of which ( lafA-U ) have been reported previously. Among the flgL L and lafA structural genes we found a modification accessory factor gene ( maf-5 ) that is involved in formation of lateral flagella; this is the first time that such a gene has been described for lateral flagellar gene systems. All Aeromonas lateral flagellar genes were located in a unique chromosomal region, in contrast to Vibrio parahaemolyticus , in which the analogous genes are distributed in two different chromosomal regions. In A. hydrophila mutations in flhA L , lafK , fliJ L , flgN L , flgE L , and maf-5 resulted in a loss of lateral flagella and reductions in adherence and biofilm formation, but they did not affect polar flagellum synthesis. Furthermore, we also cloned and sequenced the A. hydrophila AH-3 alternative sigma factor σ 54 ( rpoN ); mutation of this factor suggested that it is involved in expression of both types of flagella.