Bacillus subtilis biofilm development in the presence of soil clay minerals and iron oxides

Abstract

Clay minerals and metal oxides, as important parts of the soil matrix, play crucial roles in the development of microbial communities. However, the mechanism underlying such a process, particularly on the formation of soil biofilm, remains poorly understood. Here, we investigated the effects of montmorillonite, kaolinite, and goethite on the biofilm formation of the representative soil bacteria Bacillus subtilis. The bacterial biofilm formation in goethite was found to be impaired in the initial 24 h but burst at 48 h in the liquid–air interface. Confocal laser scanning microscopy showed that the biofilm biomass in goethite was 3–16 times that of the control, montmorillonite, and kaolinite at 48 h. Live/Dead staining showed that cells had the highest death rate of 60% after 4 h of contact with goethite, followed by kaolinite and montmorillonite. Atomic force microscopy showed that the interaction between goethite and bacteria may injure bacterial cells by puncturing cell wall, leading to the swarming of bacteria toward the liquid–air interface. Additionally, the expressions of abrB and sinR, key players in regulating the biofilm formation, were upregulated at 24 h and downregulated at 48 h in goethite, indicating the initial adaptation of the cells to minerals. A model was proposed to describe the effects of goethite on the biofilm formation. Our findings may facilitate a better understanding of the roles of soil clays in biofilm development and the manipulation of bacterial compositions through controlling the biofilm in soils.

Microbial Reduction of Metal-Organic Frameworks Enables Synergistic Chromium Removal

“…SEM images showed that MIL-100 and Fe-BTC were highly aggregated, while MIL-88A was comprised of small, well-defined crystals approximately the same size as MR-1 (Figure S5). Based on its morphology, MIL-88A is unlikely to support biofilm development (22, 23) . Although they are morphologically similar, MIL-100 and Fe-BTC vary significantly in accessible surface area.…”

Social behaviours by Bacillus subtilis: quorum sensing, kin discrimination and beyond

“…In many cases, a buffered defined medium using glutamic acid, as the sole nitrogen source, and glycerol, as the sole carbon source, is used to trigger production of the biofilm matrix (Branda et al, ). A few studies have also examined biofilm formation of model strains in different growth conditions (Dogsa et al, ; Ma et al, ), while limited insights into the diversity of biofilm regulation and biofilm properties of different B. subtilis isolates have been acquired (Oslizlo et al, ; Sanchez‐Vizuete et al, ; Yu et al, ).…”

Soil biofilms: microbial interactions, challenges, and advanced techniques for ex-situ characterization

“…However, microorganisms in the natural environment frequently exist as surface-attached structures termed biofilms (Flemming and Wingender, 2010;McDougald et al, 2011;Flemming et al, 2016). Biofilms generally colonize carbon rich surfaces of soil media such as plant roots and clay minerals, and secrete EPS to form aggregates (Ma et al, 2017;Nunan, 2017;Cai et al, 2018). The multicellular aggregates formed by soil microbes are known as soil biofilms, or unsaturated biofilms, owing to low water availability as the distinguishing environmental factor of the local environment (Holden, 2001).…”