Biofilm | The city of Microbes | Microbiology | Bacteriology | Cell Biology | Basic Science Series |
Channel: Basic Science Series
Date: 2019-07-28

In this chapter, we will know about Microbial biofilm: The city of Microbes. We will discuss in detail about biofilm, the structure of biofilm, mechanism of formation of biofilm, cell communication in biofilms, and different stages of biofilm formation. Please like and share the presentation among students and young researchers. In this presentation, the artwork is done by Dr. Lokender Kumar. 
The information was collected from https://en.wikipedia.org/wiki/Biofilm.

• These cells are embedded within a slimy extracellular matrix that is composed of extracellular substances. This extracellular substance acts as cementing material to keep the structure of biofilm intact. Extracellular substances include polysaccharides, protein, lipids, and DNA which is deoxyribonucleic acid. 

• Because of their three-dimensional structure they are called cities of microbes. 
• Biofilm may form on living as well as on non-living material and can be present in almost every environment conditions including natural, industry, and hospital. 
• In a distance biofilms look like hydrogen but these more complex than that. These are not just a layer they are coordinated functional communities where even these bacteria talk to each other and respond using chemical signal molecules.  
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• Let's discuss the stages of biofilm formation. There are five distinct stages of biofilm formation. Stage-1: Initial attachment. this stage starts with the attachment of free-floating cells to a solid surface. At first cells might attach the surface by weak Vander wall forces. These forces are physical forces between atom and molecules and there is no chemical interaction present. Using these forces bacteria make their initial attachment to the solid surface. 
• Stage-2 is Irreversible attachment. In this stage if the initial attachment process is successful bacteria use cell adhesion structures to attach tightly to the surface. The most important cell surface structure is pilli.  Pilli are the hair-like structure found on the surface of many bacteria. Another property of bacterial cells that helps in this attachment is hydrophobicity. Hydrophobicity is the property of a molecule that quantifies how much a molecule is repelled by the water. Most of the time biofilms are formed in moist environments so hydrophobicity helps the cells to get repelled by the water environment and forced to remain close to the solid surface. 
• Stage-3 is the Initial maturation of biofilm. Here cell communication or quorum sensing plays a very important role. At this stage microbial cells secrete small chemical signal molecules that are also detected by the same microbial cells. The amount of these molecules determines the number of microbial cells present in the surrounding. When the amount of this molecule reaches up to a threshold concentration this molecule induces activation of the cells and then cells switch the expression of various new proteins. This process helps in the formation and spread of microbial biofilm. 
• Stage-4 is the Final Maturation: At this stage bacterial cells start producing a very high amount of exopolysaccharide material in their surrounding. This helps the cells to make the huge tower-like structure of the bacterial biofilm. 


• Stage-5 is the dispersion or detachment. At this stage the cells detach themselves from bacterial biofilms to look for new areas for the formation of new biofilms. If the cells keep themselves the same place the population will grow and the nutrient will be depleted leading to the death of biofilm. 

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