Soil nano-minerals interactions with bacteria, and bacterial interactions such as cooperation and competition are being recognized as important factors in regulating the organization and function of soil biofilms. However, knowledge about the interactions at micro-scale in the soil micro-aggregates and microbiome and how it may be regulated by different fertilization practices is still limited.<br/>In the first part, the growth, biofilm formation, and gene expression of the beneficial and pathogenic bacteria were monitored following exposure to common soil minerals (montmorillonite, kaolinite, and goethite) and engineering nanoparticles. For example, <i>E. coli </i>O157:H7 growth was notably promoted, while biofilm formation was inhibited in the presence of montmorillonite, which is attributed to the suppression of colanic acid (CA) production and an increase in bacterial motility. Kaolinite not only promoted bacterial growth, but also contributed to biofilm formation upon stimulating CA production. Upon exposure to goethite, notably slower bacterial growth and higher biomass of biofilm were observed as compared to the control.<br/>In the second part, we investigated the profiles of bacterial social interactions in soils with different fertilization treatments. Biofilm formation in co-cultures was found to be significantly enhanced compared to mono-cultures for 67% among unfertilized soil, demonstrating a high prevalence of cooperation in dual-species biofilm in natural soil environment. In contrast, reduction in biofilm formation of co-cultures was dominating in soil receiving chemical fertilizer only or in combination with fresh chicken manure (74% and 46%, respectively). These findings indicate that potentially important social interactions among soil bacteria are affected by fertilization management.

Micro-scale determinants of bacterial biofilm formation in soils

256th National Meeting (2018)

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