Fundamentals of biofilm formation in soil: From functionalized self-assembled monolayers to rewilding

Abstract

Surface energy and surface charges play crucial roles in bacterial adhesion and biofilm formation, however the mechanisms underlying the bacteria-surface interaction, particularly on the formation of soil biofilms, remain unclear. In spite of considering the spatiotemporal dynamics of biofilm formation on different soil surfaces, we compared the impact of four different substrates on bacterial attachment and biofilm formation. The substrates were constituted of gold layer covered by NH2+, CH3, COO- and OH-terminated self-assembled monolayers (SAMS). Two soil habitat bacteria with different Gram barriers, Bacillus subtilis and Acinetobacter baylyi, were grown with incubation times of 6-72 h on each type of surfaces. Bacterial attachment and biofilm formation was assessed using metabolic activity of the cells adhered to the surfaces. The spatial distribution of adhere bacteria was visualized by scanning electron microscopy and confocal laser scanning microscopy. We also investigated whether the surface impacts the biofilm matrix composition. A general view of our results suggests a major influence of the surface chemistry on bacterial potential to form biofilms. The hydrophobic or positively charged substrates attract bacteria while a lack of attachment and biofilm formation on hydrophilic and negatively charged surfaces. This work points out the potential of surface treatments in the environment where it is intended to either repel or attract bacteria.

Reconciling the importance of minerals for propagation of antibiotic resistance genes in the environment

“…Substrate topography is a key determinant of biofilm formation [60] [64-66] that with reason can be expected to vary among different types of minerals. With the use of gold substrate terminated with self-assembled monolayers of various chemicals, we also previously found that positively charged and hydrophobic particles support biofilm formation, while negative surface charge and hydrophilic particles resist bacterial communities to congregate [67]. The strong attraction to positive charged surfaces and vice versa repulsion to negative charged particles, can potentially be explained by the general net negative charge of bacterial cells [68, 69].…”