A steroidal molecule present in the egg wax of the tick Rhipicephalus (Boophilus) microplus inhibits bacterial biofilms

Abstract

The cattle tick Rhipicephalus (Boophilus) microplus lays eggs in the soil near the roots of grass, or in similar highly moist environments that are prone to biofilm formation. Tick eggs have a protective wax coating that may be a source of nutrients for microorganisms. However, as the eggs remain viable and show no visible signs of microbial colonization, we hypothesized that the coating might have anti-biofilm properties. We show here that the coating inhibits biofilm formation by both Gram-negative and Gram-positive bacteria, though by different mechanisms. We have identified the anti-biofilm molecule as N-(3-sulfooxy-25-cholest-5-en-26-oyl)-L-isoleucine (boophiline), and we show that it inhibits the expression of fliC (flagellin) and cdrA (biofilm scaffold), whose products are necessary for biofilm formation in Pseudomonas aeruginosa. Boophiline is a novel biofilm inhibitor being also effective against Staphylococcus epidermidis biofilm. In our study we show evidences of the boophiline mode of action in the protection of arthropod eggs against biofilm colonization.