INVOLVEMENT OF MEMBRANE TRANSPORTER COMPONENTS IN BACTERIAL CHEMOTAXIS

Bacterial chemotaxis has been recognized as one of the key properties in pathogenicity and bioremediation. Here I studied on roles of membrane transporter components in chemotaxis of two species, the pathogenic bacterium Vibrio cholerae (classical biotype) strain O395N1 and the pollutant-degrading soil bacterium Burkholderia sp. NK8. First, I found that two V. cholerae proteins, Mlp2 and Mlp3, with similarities to the major amino acid chemoreceptors, mediate responses to L-serine and amino acids with small R groups, respectively. Mlp3 did not bind L-serine but co-expression of a putative serine-binding protein (named SatA) with Mlp3 increased responses to L-serine, suggesting that SatA is a primary receptor and Mlp3 is a transducer to mediate serine response. Second, I found that 3-chlorobenzoate (3CB)-degrading Burkholderia sp. NK8 is attracted to 3CB and its degradation products, 3- and 4-chlorocatechol (3CC, and 4CC), and β-ketoadipate. These tactic abilities were ablished by curing of the megaplasmid pNK8. Taxis to β-ketoadipate was complemented by the introduction of a putative outer membrane porin gene ompNK8 found in pNK8, suggesting that the porin facilitates chemotaxis to β-ketoadipate