Biofilms as the Central Platform Within Microbial Ecology, Heavy Metal Co-selection, and the Antibiotic Resistome

Soil is one of the most biodiverse and microbially complex ecosystems on Earth, harbouring an estimated 109 bacterial cells per gram and a rich reservoir of antibiotic resistance genes (ARGs). The emergence of antimicrobial resistance (AMR) as a global One Health crisis has intensified research into environmental ARG reservoirs, and increasing evidence points to heavy metals and metalloids - including arsenic (As), cadmium (Cd), copper (Cu), zinc (Zn), mercury (Hg), and lead (Pb) - as potent co-selective agents maintaining and amplifying the soil resistome under anthropogenic pressures. Simultaneously, microbial biofilms - structured, surface-associated communities embedded in extracellular polymeric substances (EPS) - have been identified as critical hotspots for ARG persistence and horizontal gene transfer (HGT) in terrestrial environments. Biofilms also play a crucial role in elemental dynamics. Integrating these four dimensions biofilm ecology, metal/metalloid contamination, AMR, and soil microbial community dynamics - remains a key unmet challenge in environmental microbiology.Despite considerable individual advances in biofilm biology, environmental geochemistry, and soil AMR research, the mechanistic interplay among these domains in terrestrial ecosystems remains poorly understood. Notably, a lively scientific debate still persists regarding the actual scale, definition, and structural prevalence of true biofilms within highly heterogeneous soil matrices compared to aquatic or clinical settings. This Research Topic aims to address this conceptual boundary. The co-localisation of metal resistance genes (MRGs) and ARGs on shared mobile genetic elements (MGEs) - plasmids, transposons, and integrons - enables simultaneous horizontal transfer under metal selection pressure, even in the absence of antibiotic residues. Biofilm architecture compounds this by providing a physical microenvironment that restricts antibiotic penetration, fosters close inter-bacterial contact, and sustains sub-inhibitory concentrations that drive chronic selection. Recent metagenomic studies demonstrate that bioavailable heavy metal fractions - rather than total concentrations - are the primary drivers of ARG composition in contaminated soils.This Research Topic aims to synthesize current mechanistic understanding and generate new empirical data on how biofilm formation under metal and metalloid stress accelerates ARG dissemination, alters microbial community assembly, and creates terrestrial AMR reservoirs with One Health relevance. We particularly welcome studies employing multi-omics, single-cell imaging, and spatial ecology approaches to reveal novel mechanistic and ecological insights. It will involve curiosity-driven research seeking the mechanistic to applied aspects of biofilm-mediated MRGs and AMR within microbial cross-communities. We welcome Original Research Articles, Systematic Reviews, Mini-Reviews, Methods Articles, and Perspective/Opinion pieces addressing the following themes:• EPS composition and structural dynamics of soil biofilms under heavy metal/metalloid stress• Molecular co-selection, co-expression and cross-resistance mechanisms linking MRGs and ARGs (plasmids, transposons, integrons, efflux pumps)• HGT rates (conjugation, transformation, transduction) within intact soil biofilms vs. planktonic communities• Metagenomic/metatranscriptomic profiling of soil resistomes and mobilomes in metal-contaminated soils• Microbial community assembly, functional diversity, and ecosystem service disruption under combined biofilm-metal-antibiotic stress• Rhizosphere and endosphere biofilm ecology under metalloid contamination• One Health risk pathways: ARG flow from contaminated terrestrial reservoirs to clinical settings• Novel surveillance tools, bioindicators, and regulatory/policy frameworks for metal-AMR co-contamination Topic editors: Arnab Majumdar, MRSB, AMRSC, Chujin Ruan Source: https://www.frontiersin.org/research-topics/82985/biofilms-as-the-central-platform-within-microbial-ecology-heavy-metal-co-selection-and-the-antibiotic-resistome