Microbial biofilm: formation, architecture, antibiotic resistance, and control strategies

Abstract

The assembly of microorganisms over a surface and their ability to develop resistance against available antibiotics are major concerns of interest. To survive against harsh environmental conditions including known antibiotics, the microorganisms form a unique structure, referred to as biofilm. The mechanism of biofilm formation is triggered and regulated by quorum sensing, hostile environmental conditions, nutrient availability, hydrodynamic conditions, cell-to-cell communication, signaling cascades, and secondary messengers. Antibiotic resistance, escape of microbes from the body's immune system, recalcitrant infections, biofilm-associated deaths, and food spoilage are some of the problems associated with microbial biofilms which pose a threat to humans, veterinary, and food processing sectors. In this review, we focus in detail on biofilm formation, its architecture, composition, genes and signaling cascades involved, and multifold antibiotic resistance exhibited by microorganisms dwelling within biofilms. We also highlight different physical, chemical, and biological biofilm control strategies including those based on plant products. So, this review aims at providing researchers the knowledge regarding recent advances on the mechanisms involved in biofilm formation at the molecular level as well as the emergent method used to get rid of antibiotic-resistant and life-threatening biofilms.

Keywords: Antibiofilm; Antibiotic resistance; Biofilm; Biofilm formation; Plant; Quorum sensing.

Fig. 1

Steps of biofilm formation. The multi-step biofilm formation starts with the attachment of planktonic microorganisms to the surfaces which is sub-divided into reversible and irreversible attachment followed by microbial division to form microcolonies. Microcolonies undergo maturation characterized by specific composition, shape, and architecture followed by dispersion of biofilm to repeat the cycle. A mature biofilm is a heterogeneous mixture of planktonic (green flagellated), sessile (green), persistent (brown), dead (black) cells, water channels, and different types of signaling and stabilizing molecules like acyl-homoserine lactones (AHL), lipids, polysaccharides, proteins, extracellular DNA (eDNA)

Fig. 2

Antibiofilm strategies. The different novel strategies to deal with biofilm menace could be broadly divided into three broad categories: biological, chemical, and physical strategies

Fig. 3

Plant-based antibiofilm strategies. The figure mentions the different ways plants are being used nowadays to inhibit, reduce, or eradicate biofilm formation. As indicated in the figure, the plants act as inhibitors of quorum sensing (QS), biofilm-related enzymes, extracellular polymeric substance (EPS) matrix synthesis, virulence factors, secondary messengers, signaling cascades, biofilm promoting genes, and other biofilm-related factors. From the figure, it is clear that plants could be used effectively against microbial biofilms