Effect of flagella on initial attachment of Listeria monocytogenes to stainless steel

Abstract

At 22 degrees C a flagellin mutant of Listeria monocytogenes was found to attach to stainless steel at levels 10-fold lower than wild-type cells, even under conditions preventing active motility. At 37 degrees C, when flagella are not produced, attachment of both strains was identical. Therefore, flagella per se facilitate the early stage of attachment.

FIG. 1

Viable cell numbers in L. monocytogenes biofilm for up to 24 h. ■ and ●, wild type incubated at 22 and 37°C, respectively; □ and ○, nonflagellated mutant incubated at 22 and 37°C, respectively. The initial concentration was 8.5 × 10⁸ CFU ml⁻¹. Error bars show the standard deviations of six values from triplicate samples.

FIG. 2

Viable cell numbers of L. monocytogenes biofilm over a 4-h period. The initial concentration was 8.6 × 10⁸ CFU ml⁻¹. ■ and ●, wild type incubated at 22 and 37°C, respectively; □ and ○, nonflagellated mutant incubated at 22 and 37°C, respectively. Error bars show the standard deviations of six values from triplicate samples.

FIG. 3

Percentage of coverage by L. monocytogenes biofilm on stainless steel over a 4-h period, determined by staining with acridine orange. Fifteen microscopic fields of each coupon were analyzed. The area covered by the bacteria on each field was compared to the total area of a microscopic field as an absolute value (100%). ■ and ●, wild type incubated at 22 and 37°C, respectively; □ and ○, nonflagellated mutant incubated at 22 and 37°C, respectively. Error bars show standard deviations of values from triplicate coupons.