 Hi everyone. Welcome to the basic science series by Dr. Lokendra Kumar. I have created this program to promote scientific knowledge among students and young researchers. In this episode, we will discuss in detail about microbial biofilms. Also refer as the city of microbes. We will know what are microbial biofilms and what are the basic components of microbial biofilms. We will also know about different stages of microbial biofilm formation and by the end of the episode you will have all the basic information about microbial biofilms. Let's first define a microbial biofilm. A typical biofilm is composed of a population of microorganisms in which microbial cells are attached to each other and also attached to a solid surface. These cells are embedded within a slimy extracellular matrix that is composed of extracellular substances. This extracellular substance acts as a cementing material to keep the structure of biofilm intact. Extracellular substances include polysaccharides, proteins, lipids and DNA which is deoxyribonucleic acid. Because of their three-dimensional structure they are called as cities of microbes. Biofilms may form on living as well as on non-living material and can be present in almost every environmental conditions including nature, industry and hospitals. In a distance biofilms look like a hydrogel but these are 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. Alright let's discuss the stages of biofilm formation. There are five distinct stages of biofilm formation. Stage one initial attachment. Stage two irreversible attachment. Stage three initial maturation. Stage four final maturation. And stage five dispersion. Let's start with the stage one which is initial attachment. This stage starts with the attachment of free floating cells to a solid surface. At first cell might attach the surface by weak Wonderwall forces. These forces are the physical forces present between molecules and atoms and there is no chemical interaction present. Using these forces bacteria make their initial attachments to a solid surface. Stage two is irreversible attachment. In this stage if the initial attachment process is successful bacteria use cell adhesion structures to attach tightly to the surface. Most important cell surface structure is pillae. Pillae are the hairlike structure found on the surface of many bacteria. Another property of bacterial cell that help in the attachment is hydrophobicity. Hydrophobicity is the property of molecule that quantify how much a molecule is repelled by the water. Most of the time biofilms are found in a moist environment so hydrophobicity helps the cells to get repelled by the water environment and forced to be remain close to the solid surface. Stage three 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 determine the amount of microbial cell present in the surrounding area. When the amount of these molecules reach up to a threshold concentration these molecules induce activation of these cells and then cells switch the expression of various new proteins. This complete process helps in the formation of biofilm as well as the spread of microbial biofilms. Stage four is the final maturation stage. At this stage bacterial cells start producing 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 five is the dispersion or the detachment stage. At this stage the cells detach themselves from microbial biofilms to look for new area for the formation of new biofilms. If the cell keep themselves to the same place the population will grow and the nutrient will be depleted leading to the death of the biofilm. Therefore for the survival of microbial biofilm the cells should keep looking for new places to colonize. Cells use an enzyme called dispersion B to make their way out from a microbial biofilm by degrading extra cellular substances. After getting detached from the microbial biofilm the cells again start with the stage one and the complete process is repeated to make new biofilm. The stage of dispersion fits interestingly to the idea that humans are also trying to find new planets for their survival. We know that resources are limited and we need space, food, energy. Therefore like microbes we are at this stage of dispersion to make new habitats. So the human community can survive if the resources are finished on planet Earth. With this note I conclude this presentation. Please like and share the video with students and young researchers. Please subscribe the YouTube channel to get updates on new presentation on basic science topics. Please forgive my mistakes. Thank you and Namaste.