Biofilm Development in Gram-Positive and Gram-Negative Bacteria

Abstract

Biofilms are the communities of microorganisms, especially bacteria attached to a biotic or abiotic surface. These biofilms live in a self-sustained matrix and produce different substances called extracellular polymeric substances (EPS) which are responsible for the pathogenicity of a number of bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Vibrio cholerae, Klebsiella pneumoniae, Escherichia coli, etc. These EPS substance makes it difficult to eradicate the biofilm present on the surface. Biofilm formation is a five-step process. Biofilms can be monospecies or multispecies. In biofilms, cells communicate via Quorum Sensing (QS). QS is the regulation of gene expression in bacteria with respect to changes in cell population density. In QS, bacteria produce various signaling molecules called Auto-inducers (AI). AI concentration increases as the bacterial population increases. Bacteria respond to these AIs results in an alteration of gene expression, which results in the release of various virulence factors. QS involves a two-component signaling process which is different for both Gram-positive and Gram-negative bacteria. QS and EPS make the bacteria resistant to various antibiotics, which make the eradication difficult and hence requires more effective treatment. This article discusses the biofilm structure, phenomenon of biofilm formation, signaling, and pathogenicity to highlight the understanding of processes involved in biofilm formation.