Question

Discuss Biofilms. You might want to address their formation, location, composition, advantages for microorganisms they contain, a few examples where we find them etc.

Answer 1

Biofilm:

Formation: Biofilm is a specialized surface attached community of one or several species of microorganisms i.e. bacteria, fungi and protists. The first stage of biofilm formation occurs due to specific environmental signal. In response to this signal the planktonic cells attach to the near by wet surfaces by means of flagella, pili, LPS etc and begin to reproduce. They form an monolayer of extracellular matrix or slime to which more planktonic cells attach and starts dividing. Thus formation of microcolonies takes place where the cells communicate with each other by quorum sensing.

Location: Biofilm is formed over solid surfaces submerged in water or surrounded by moist environment.

Composition: Biofilm is mainly composed of microbial cells and extracellular polymeric substances or EPS produced by them for their protection. This EPS matrix is mainly composed of polysaccharaides, protein, lipid, cell debris and nucleic acids.

Advantage: Biofilm i) Protect the cells from damage from various environmental stresses.

ii) Provide a good nutritional source i.e. nutrition rich surfaces.

iii) Provide resistance to antibiotics.

iv) Provides a cellular communication and cooperation platform.

v) Facilitate genetic exchange due to close proximity.

Example: i)  Pseudomonas aeruginosa form single species biofilm in the lungs of cystic fibrosis patients.

ii) Plaque formation on teeth (dental plaque) by bacteria within mouth.

iii) Pond scum formed by algae or cyanobacteria.