A magnetic levitation-based system to study the mechanisms of bacterial flocculation and autoaggregation

Abstract

Objective. To evaluate the potential of magnetic levitation systems when studying the autoaggregation of gram-negative and gram-positive pathogenic bacteria and elucidating mechanisms controlling autoaggregation.Materials and methods. Escherichia coli O157:H7, Pseudomonas aeruginosa, Staphylococcus aureus, and Listeria monocytogenes were used. The number of alive bacteria was determined using a Live/Dead® dye. E. coli curli were stained with Congo red.Results. All four tested bacterial species formed autoaggregates that levitated within the liquid volume for up to 72 hours (observation time). After 72 hours, the number of alive bacteria in the autoaggregates ranged from 82% (E. coli) to 99% (L. monocytogenes). The formation of E. coli autoaggregates was shown to depend on the production of curli, which represent surface structures playing an important role in biofilm formation.Conclusion. The proposed system of magnetic levitation can be used to study molecular mechanisms of bacterial autoaggregation and flocculation.