Fernando Baquero, Teresa M. Coque, Natalia Guerra-Pinto, Juan-Carlos Galán, David Jiménez-Lalana, Javier Tamames, Carlos Pedrós-Alió

Bacterial organisms like surfaces. Water and soil contain a multiplicity of particulated material where bacterial populations and communities might attach. Microbiotic particles refers to any type of small particles (less than 2 mm) where bacteria (and other microbes) might attach, resulting in medium- long-term colonization. In this work, the interactions of bacterial organisms with microbiotic particles of the soil and water are reviewed. These particles include bacteria-bacteria aggregates, and aggregates with particles of fungi (particularly in the rhizosphere), protozoa, phytoplankton, zooplankton, biodetritus resulting from animal and vegetal decomposition, humus, mineral particles (clay, carbonates, silicates), and anthropogenic particles (including wastewater particles or microplastics). At they turn, these particles might interact and coalesce (as in the marine snow). Natural phenomena (from river flows to tides, tsunamis, currents, or heavy winds) and anthropogenic activity (such as agriculture, waste-water management, mining, soil-mass movement) favors interaction and merging between all these soil and water particles, and consequently coalescence of their bacterial-associated populations and communities, resulting in an enhancement of mixed-recombinant communities capable of genetic exchange, including antimicrobial resistance genes, particularly in antimicrobial-polluted environments. Particles also favor compartmentalization of bacterial populations favoring diversification and acquisition of mutational resistance by random drift. In general, microbial evolution is accelerated by the aggregation of microbiotic particles. We propose that the world spread of antimicrobial resistance might relate with the environmental dynamics of microbiotic particles, and discuss possible methods to reduce this problem influencing One Health and Planetary Health.