Biofilm
Microbes form a biofilm in response to a number of different factors,[9] which may include cellular recognition of specific or non-specific attachment sites on a surface, nutritional cues, or in some cases, by exposure of planktonic cells to sub-inhibitory concentrations of antibiotics.
[10][11] A cell that switches to the biofilm mode of growth undergoes a phenotypic shift in behavior in which large suites of genes are differentially regulated.
[13] The biofilm bacteria can share nutrients and are sheltered from harmful factors in the environment, such as desiccation, antibiotics, and a host body's immune system.
[14][page needed] Biofilms are thought to have arisen during primitive Earth as a defense mechanism for prokaryotes, as the conditions at that time were too harsh for their survival.
[22] In addition to the polysaccharides, these matrices may also contain material from the surrounding environment, including but not limited to minerals, soil particles, and blood components, such as erythrocytes and fibrin.
Secreted by Pseudomonas aeruginosa, this compound induces cyclo heteromorphic cells in several species of bacteria and the yeast Candida albicans.
[47] One benefit of this environment is increased resistance to detergents and antibiotics, as the dense extracellular matrix and the outer layer of cells protect the interior of the community.
As an epigeal biofilm ages, more algae tend to develop and larger aquatic organisms may be present including some bryozoa, snails and annelid worms.
As water passes through the hypogeal layer, particles of foreign matter are trapped in the mucilaginous matrix and soluble organic material is adsorbed.
[64] These microbe associated molecules interact with receptors on the surface of plant cells, and activate a biochemical response that is thought to include several different genes at a number of loci.
Stromatolites are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by microbial biofilms, especially of cyanobacteria.
[75] Dental plaque is an oral biofilm that adheres to the teeth and consists of many species of both bacteria and fungi (such as Streptococcus mutans and Candida albicans), embedded in salivary polymers and microbial extracellular products.
About 80% of CF patients have chronic lung infection, caused mainly by P. aeruginosa growing in a non-surface attached biofilms surround by PMN.
[111] The infection remains present despite aggressive antibiotic therapy and is a common cause of death in CF patients due to constant inflammatory damage to the lungs.
[4][112] Biofilm formation of P. aeruginosa, along with other bacteria, is found in 90% of chronic wound infections, which leads to poor healing and high cost of treatment estimated at more than US$25 billion every year in the United States.
[113] In order to minimize the P. aeruginosa infection, host epithelial cells secrete antimicrobial peptides, such as lactoferrin, to prevent the formation of the biofilms.
The multi-target mechanism of action involves outer membrane permeabilization followed by biofilm disruption triggered by the inhibition of efflux pump activity and interactions with extracellular and intracellular nucleic acids.
[119] The biofilm formation of these pathogenic E. coli is hard to eradicate due to the complexity of its aggregation structure, and it has a significant contribution to developing aggressive medical complications, increase in hospitalization rate, and cost of treatment.
[126] Serratia marcescens is a fairly common opportunistic pathogen that can form biofilms on various surfaces, including medical devices such as catheters and implants, as well as natural environments like soil and water.
Research has shown that S. marcescens biofilms exhibit complex structural organization, including the formation of microcolonies and channels that facilitate nutrient and waste exchange.
The production of extracellular polymeric substances (EPS) is a key factor in biofilm development, contributing to the bacterium's adhesion and resistance to antimicrobial agents.
[137] Biofilms are used in microbial fuel cells (MFCs) to generate electricity from a variety of starting materials, including complex organic waste and renewable biomass.
[143] Bacteria can survive long periods of time in water, animal manure, and soil, causing biofilm formation on plants or in the processing equipment.
[145] As a response to the aggressive methods employed in controlling biofilm formation, there are a number of novel technologies and chemicals under investigation that can prevent either the proliferation or adhesion of biofilm-secreting microbes.
Latest proposed biomolecules presenting marked anti-biofilm activity include a range of metabolites such as bacterial rhamnolipids[148] and even plant-[149] and animal-derived alkaloids.
In the marine environment, biofilms could reduce the hydrodynamic efficiency of ships and propellers, lead to pipeline blockage and sensor malfunction, and increase the weight of appliances deployed in seawater.
Bacterial autolysis is a key mechanism in biofilm structural regulation, providing an abundant source of competent DNA primed for transformative uptake.
[168] Conjugative plasmids may encode biofilm-associated proteins, such as PtgA, PrgB, or PrgC which promote cell adhesion (required for early biofilm formation).
Membrane vesicle HGT has been witnessed occurring in marine environments, among Neisseria gonorrhoeae, Pseudomonas aeruginosa, Helicobacter pylori, and among many other bacterial species.
[168][171] Membrane vesicle HGT has also been shown to modulate phage-bacteria interactions in Bacillus subtilis SPP1 phage-resistant cells (lacking the SPP1 receptor protein).
