Editorial: Biofilms from a Food Microbiology Perspective: Structures, Functions, and Control Strategies

摘要

Materials and equipment in food processing industries are colonized by surface-associated microbial communities called biofilms. In these biostructures microorganisms are embedded in a complex organic matrix composed essentially of polysaccharides, nucleic acids, and proteins. This organic shield contributes to the mechanical biofilm cohesion and triggers tolerance to environmental stresses such as dehydration or nutrient deprivation. Notably, cells within a biofilm are more tolerant to sanitation processes and the action of antimicrobial agents than their free living (or planktonic) counterparts. Such properties make conventional cleaning and disinfection protocols normally not effective in eradicating these biocontaminants. Biofilms are thus a continuous source of persistent microorganisms, including spoilage and pathogenic microorganisms, leading to repeated contamination of processed food with important economic and safety impact. Alternatively, in some particular settings, biofilm formation by resident or technological microorganisms can be desirable, due to possible enhancement of food fermentations or as a means of bioprotection against the settlement of pathogenic microorganisms.In the last decades substantial research efforts have been devoted to unraveling mechanisms of biofilm formation, deciphering biofilm architecture, and understanding microbial interactions within those ecosystems. However, biofilms present a high level of complexity and many aspects remain yet to be fully understood. A lot of attention has been also paid to the development of novel strategies for preventing or controlling biofilm formation in industrial settings. Further research needs to be focused on the identification of new biocides effective against biofilm-associated microorganisms, the development of control strategies based on the inhibition of cell-to-cell communication, and the potential use of bacteriocins, bacteriocin-producing bacteria, phage, and natural antimicrobials as anti-biofilm agents, among others.This research topic aims to provide an avenue for dissemination of recent advances within the “biofilms” field, from novel knowledge on mechanisms of biofilm formation and biofilm architecture to novel strategies for biofilm control in food industrial settings.The research topic comprises three review articles, one perspective and 11 original research articles. Most of the contributions cover the most recent investigations on aspects related to the structures, architecture, and strategies for the control of biofilms formed by pathogenic or spoilage microorganisms on food processing surfaces, while two contributions are focused on the evaluation of biofilm formation by resident, technologically important or desirable microorganisms.Various contributions deal with biofilms formed by strains of Bacillus spp. The review article by Majed and co-authors discusses the state-of-the-art on biofilms produced by Bacillus cereus , and by the two closely related pathogens, Bacillus thuringensis and Bacillus anthracis ( Majed et al. ). The review summarizes economic issues caused by B. cereus biofilms, the ecological and functional impact of biofilms in their lifecycle and management strategies implemented to control them. The research article by Hayrapeytan and co-authors shows the existence of intraspecies variability in the genome-encoded repertoire of iron-transporting systems and in the ability to grow and form biofilms in the presence of complex iron sources within B. cereus , which may influence B. cereus survival and persistence in food-related niches ( Hayrapetyan et al. ). Duanis-Assaf and co-authors report in their research article that lactose may induce biofilm formation by Bacillus subtilis through a quorum sensing dependent (LuxS) pathway ( Duanis-Assaf et al. ). In particular, they demonstrate that lactose induces formation of biofilm bundles, an increase in autoinducer-2 production in response to lactose, and an up-regulation of two gene operons responsible for extracellular matrix synthesis (e.g. eps and tapA ).In relation to Campylobacter jejuni biofilms, Brown and co-authors show in their contribution that extracellular DNA (eDNA) is an important component of C. jejuni biofilms formed on stainless steel surfaces ( Brown et al. ). The authors also evidence that eDNA may also contribute to the spread of antimicrobial resistance in C. jejuni . Finally, they report that degradation of eDNA by DNase I leads to rapid biofilm detachment, which shows promise for the control of C. jejuni biofilms in food industries. The research article by Turonova and co-authors reports that acclimation of two C. jejuni strains to oxygen-enriched conditions leads to a significant enhancement of biofilm formation during the early stages of the process, indicating that oxygen demand for biofilm formation is higher than for planktonic growth ( Turonova et al. ). The authors also identify the regulator CosR as a key protein in the