[Mutagenesis on biofilm formation of Listeria monocytogenes by Tn917 transposon insertion].

ABSTRACT

Surface-attached populations of bacteria comprising either single or multiple species were referred to as biofilm. The bacteria in the biofilm had more resistant ability against antibiotics and disinfectors, which could cause the constituent clinical affection or food contamination. In order to isolate and characterize the genes involved in biofilm formation of Listeria monocytogenes, the plasmid pTV1-OK containing the transposon Tn917 was transformed into the protoplasm of Listeria monocytogenes. After cultivating for 4 days, twenty positive transformants per microgram DNA were generated. Some transformants were selected for inducing transposition in water bath overnight at 42 degrees C, and the transposition efficiency of Tn917 was 10(-7). The LM-49 strain with higher ability on biofilm formation than the wild strain was obtained by microtiter plate assaying, and the purple ring formed by the LM-49 was thicker than that by the wild after a 4-day incubation. The PCR result using specific primers of Tn917 proved that Tn917 was inserted into the genome of L. monocytogenes. So the LM-49 strain can be regarded as the mutant of biofilm formation, and the higher ability of biofilm formation is caused by the insertion of Tn917.