Bacterial transport and colonization in low nutrient environments

Abstract

Crucial and potentially rate limiting events in biofilm formation are the transport of microorganisms to the solid-water interface and the subsequent attachment onto a substratum. If these attached cells find suitable environmental conditions they will replicate, grow and form a biofilm. Experiments with different surfaces—stainless steel, glass, and polycarbonate—and two Pseudomonas species were conducted and parameters describing attachment, growth, and transport were measured in situ and in real time using image analysis techniques. The phenomenon of cellular starvation was investigated with special attention to the effect on the attachment characteristics of the two tested Pseudomonas species. Experiments were conducted with Pseudomonas aeruginosa and Pseudomonas fluorescens as a Mot+ and a Mot− strain. As a result of superior transport properties, flagellated cells of Pseudomonas fluorescens colonized a substratum at a higher rate than unflagellated cells. Nutrient conditions in the bulk water influenced the growth of suspended and attached organisms, as well as the cellular transport to the solid-water interface and the rate of attachment onto the substratum. Starved cells of P. aeruginosa and P. fluorescens exhibited increased cell motility by size reduction. Cellular transport was demonstrated to be a crucial process in microbial colonization, and may be limiting the overall rate of surface colonization. The phenomenon was demonstrated for a motile and nonmotile mutant of the same strain. Hence, diffusive, advective, and hydrodynamic properties of a specific system cannot be neglected if we try to understand and simulate microbial colonization. Keywords