 Now, the bacteriophages are those viruses which are causing the disease inside the bacteria. Therefore, from the diagnostic point of view or from the control point of view, we can use them for controlling the bacteria. What are the different properties which are used, which are these bacteriophages are containing? However, there are also some viruses which are also causing the disease or which are also going to replicate just like the satellites and the videos which are also present inside some viruses and we will study them later. First of all, the bacteriophage. The bacteriophage is also known as only the phage. They are causing the disease. They are infecting the bacteria and they are replicating inside the cell of the bacteria and archaea. This is just the simple standard shape of the bacteriophage which is containing the head and its tail. The general characteristics of bacteriophage, the virus architecture, the virus particles called virion. It consists of the nucleic acid and surrounded by the protein code. Here you can see just like the structure. This is the virion. Virion is consist of the nucleic acid which is present inside here in the red killer. You can see the nucleic acid and it is surrounded by the protein code which is also called as capsid. And this is the helicalin structure. However, here you can see the same thing. This is the nucleic acid and this is the protein code. However, the structure is different and this is the structure or the same thing and can be seen under the electron microscopy. This is for this helical structure and this is for this rod shape virus. And here you can see the whole virus, the T-phage, P4-phage and its shapes may be isometric. You can see helical are the complex structure. Maybe complex. Maybe it contains all the structures inside it. These are the tail fibers here and it is the head. This is the collar and this is the body. This red one is the nucleic acid and here you can see it in the electron microscope. So these are the, this is the nucleic acid and the shape may be the icosahedral, helical or the complex. So there are two types of the virions. One is naked. Naked mean that it has no envelope and the other one as an envelope which are surrounded by the lipid membrane. Here is the size. You can just for the comparison of the size of the bacteriophages. You can see this is the human red blood cell, the RBC. This is just the part of the RBC. This is its size. And as compared to it, this is the adenovirus. Its size is 19 nanometer. Similarly, the tobacco mosaic virus which is causing the disease in tobacco plants which is much larger as compared to the adenoviruses and that is 250 nanometer. And here you can see T4 bacteriophage which is just about smaller than the tobacco mosaic virus. And this is the size of one simplest bacteria which we are, which is present inside the human body, inside the animal's body and it is excretia coli. So this is the excretia coli. These are the plasmid present inside and here this is the coli and you can compare the size of some viruses as compared to bacteria and then T4 bacteriophage which is causing the disease in the virus and this is the human red blood cell. So virus interactions with the host cell, the bacteriophages and its interaction and after it enters the host cell, what is its future? What it can and what it cannot be do after entering inside the body? This is the virion we already see and this will cause infection. Then it will be enters inside the host cell. Now there are two possibilities. Whether there is a genetic alteration of the host cell, of course the virus is present inside the host itself which will take over the machinery or maybe it is causing the disease of the host cell. Latent stage in the nucleic acid virus becomes a part of host cell DNA and replicates as a plasmid. This is the latent stage and the virus does not cause the disease at this moment and host cell is often modified and continues to multiply and host cell will just consider that virus the parts of its own life cycle and the virus will just retain inside the body as a latent. On the other side, the most importantly if the virus is going to cause the disease in the host cell then the reproductive infection will occur of course and due to the because of the disease more and because of the replication more and more viruses will be produced inside then there is again two possibilities. Whether the virus is capable of lysis of the cell or release of the variants if it is caused the release of the variants then there will be no lysis of the cells. However, if the lysis of the cells then the release of the variants here are two different possibilities. Either first is the release of the variants or first is the lysis or non lysis of the cells. So if the first is the lysis of the cells and then the variants are released then cell will die and if the first the release of the variants and non lysis of the cells then host cell and continues the leakage of the variants and it will be going on to continue to struggle against that virus. It is the lytic cycle of some of the bacteriophages just taking the example of the bacteriophages we can again see it's in a little bit detail we will start from here this is we taken the example of the E. coli the bacterial and these are the plasmid bacterial DNA not the plasmid first step the viruses the bacteriophages are here containing the DNA they will be just attached to the specific receptors on the cell wall of the E. coli and then after the attaching the DNA need to be entered inside the body the penetration of the DNA following attachment the phage DNA is injected into the bacterial cell of course the capsid will stay outside the body and the DNA will just enter inside the body then transcription the replication will be started the phage DNA producing the phage mRNA which is translated to the phage proteins here are the DNA and RNA and phage induced proteins are already present there which is also called as maybe the changes in the cells which is infected by the virus now it will be continued and the replication therefore the proteins different kind of the proteins will also continue it may be containing the structural protein or it may be containing non-structural proteins and the host DNA will continue to be degraded here similarly the assemblies the different viruses are increasing in number you see here is nonspecific and here is specifically you can see a lot of bacteriophages are already here and phage components are assembled into mature variants now here it can go on the other way like this and it can go on this first the step six the release first of the bacterial cell will be ruptured and the release of the infective phages to infect the other bacteria however on the other way the head of the empty the DNA is inside the head and it will be who cause the disease and if you cause the bacteriophages to make it complete to the phages the empty empty heads of the DNA are already outside so it will come out the nucleic acid will become outside and outside it will be just enter inside the head to make it just a different kind of the structures of the bacteriophages just to understand a little bit more better you can see the video in which way you can see it later take a look around from the big to the small visible to the invisible life is everywhere the smallest unit of life is called the cell and your body is made up of 30 to 40 trillion of them but if you took the total number of bacteria on your body right now that number would outnumber your body cells 10 to 1 making us theoretically 90% bacteria now it's a lot of bacteria but can you imagine total number of bacteria on earth it's a ridiculously high number and we all know bacteria can survive almost anywhere on the planet now take that total number of bacteria on the planet and add to it every other living thing from birds to mammals fish add it all on what number do you get now what's the total number of living organisms on earth what if I told you that it didn't matter because there's an entity on earth that out numbers every living thing combined that you guys probably don't even know about bacteriophages bacteriophages or phages for short are viruses that infect bacteria cells they are by far the most abundant and diverse biological entities on the planet totaling 10 to the 31st in population to put that in perspective there are 1 billion times more bacteria phages on earth than stars in the observable universe there are 10 billion times more phages than every grain of sand added up on earth lastly if you added the net worth of Bill Gates Mark Zuckerberg and Warren Buffett together and multiplied that number by a trillion you'd still have 100 million times less money than the total number of bacteriophages on the planet so should we be worried with all these viruses floating around well no these viruses are very host specific meaning they only infect certain species of bacteria cells by recognizing very specific receptors on the surface of bacteria in other words they're no harm to human cells at all bacteria phages were first co-discovered in the early 1900s by a British scientist named Frederick tort and a French Canadian scientist named Felix Durell these scientists noticed that clear circles called plaques were forming on their petri dishes that were growing bacteria suggesting that the bacteria was being killed Durell named them bacteria phages literally meeting bacteria eaters these phages solely rely on random encounters with bacteria that they infect once they come in contact with their specific host they attach to the surface of the cell with tail proteins and begin to degrade the cell wall they then inject their DNA or genetic material which is stored in the head or the capsid through their tail and into the bacteria cell depending on the virus the cell does one of two things at this point if the phage is a lytic virus the cells machinery including the ribosomes will begin to make viral proteins that were coded in the newly integrated viral DNA within minutes the cell continues to replicate the phage progeny until eventually the cell burst open and hundreds of newly created bacteria phages are released into the surroundings looking to infect more bacteria if the phage is lysogenic on the other hand it does not burst the cell open immediately instead the genetic information is replicated along with the rest of the cells genome and remains dormant once the conditions are right that's when the viral replication initiates and lysis of the cell occurs so what's the big deal why do we care about bacteria phages if they don't really affect us well first and foremost the potential antibiotic capabilities of these phages are astounding in a world where antibiotic resistance is on the rise and superbugs are always a threat on the horizon phages could offer a quick and inexpensive way to solve these bacteria problems treating bacterial diseases like tuberculosis and leprosy could potentially be achieved by introducing phages that infect that specific bacterial strain phages also have some bioremediation potential and could be used to control environmental problems in the future hospitals have been attempting to develop ways to use phages to reduce biofilm in hospital settings which is becoming an increasing problem lastly the U.S. Food and Drug Administration and the USDA have approved several phage products including treating meat and poultry products with phages a ton of research and studies continue to take place on bacteria phages many of which involve their genomics because of their abundance there's a humongous reservoir of untapped and unsequenced gene information that could lead to the next big discovery in science who knows what's to come now you have seen this is a very interesting video about the bacteria phages and you have seen about the different contents of the bacteria phages the principles of that how bacteria will attack the different the equalized cells are how the the bacteria phages the viruses will attack the bacterial cells and how it replicates and then it is capable of even the killing the bacteria or maybe it is possible that it maybe lives inside in the bacteria and it can destroy it