going to biology 132 mini lecture number 11 so we've just completed our section on Evolution phog gentics and now we're going to get in and start looking at all of those organisms so when I show a phog gentic tree now I expect that through that beginning um now that we finished units one and two you'll be able to read that in and I won't spend a lot of extra time on that so you you may have to go back and review your information if you're feeling you're not grasping a phog gentic tree or relationships uh throughout the rest of the semester please go ahead and review uh that that unit one and two material uh as well as some of the terms I'll use I'll just kind of cruise through and and discuss about divergent evolution and so on or say this is a result of convergent evolution and I expect that you remember that from uh that unit one so if you need to don't be afraid to go back and review so for this mini lecture we're going to talk about living things that aren't really organisms so viruses which are living but aren't organisms and we're going to see why so we're going to talk about three hypothesis about how viruses evolved we're going to describe the general structure of a virus recognize the basic shapes of viruses understand the past and emerging classification systems I'm really going to focus on mainly the Baltimore classification system I'll just let that out now list phases of viral replication and basics of each talk about some diseases caused by viruses discuss some economic impacts of viruses um and compare vaccination and antiviral drugs in treating viruses I will say this is actually a really good chapter of your textbook um so if you haven't been reading the textbook uh this one's really really accessible and I think there's a of good information so I would encourage you to do that as well I am not a virologist we have a virologist two of them on on our faculty um I am more of a a larger organism person but I know enough to to get through this so I'm going to encourage you what I'm saying there is I'm going to encourage you to to read about this if you have more questions okay introduction to viruses um I'm sure we're all sick of seeing the that virus up on the right side so what is a virus a virus is an obligate intracellular par parasite so let's break this definition down obligate or obligate if you're obligated to do something you have to do it right so they are obligate they have to intracellular that's within a cell parasite they have to be a parasite within a cell it says that they have to live within the cells of other organisms right so that is what that definition is telling us okay so viruses are these obligate intracellular parasites they need a host a viron is a single virus particle know we're saying particle and not organism right because they're not really organisms and we'll see why in a minute they're generally very very small 20 to 250 nanometers and most can only be seen with an electron microscope which we have downstairs in Crawford Hall thanks to uh my colleagues um however some really big ones so some DNA viruses some pox viruses can be observed with light microscopy under really high um magnification so we can look at all the different images of uh Corona virus I'm not going to take the time to do that here um this would be an N link I would encourage you to just look at different images of viruses so let's talk about the evolution of viruses where they come from different hypotheses and let me get myself out of the corner here so we can bump that up okay oh that's G to just do that all right so there we go I'll leave that alone so one we have a agressive hypothesis so they were once free living cells that then lost most of the information um in the structure so here's our regression hypothesis so they have reductive Evolution now we're going to talk about reductive evolution in later in in some organisms because Evolution doesn't favor complexity right um so things like tapeworms have no digestive system but they would have had a free living ancestor right so they've evolved for Simplicity so just keep that in mind so here we have a a protocell and then we lost a lot of the structure right reductive Evolution lost of translation became an obligate parasite and so the only way it can get its DNA is to to the next generation is to move it into another hostel and splice it in okay Progressive hypothesis says that viruses were really RNA or DNA that escaped their host cells um so kind of here's our our escaped hypothesis so here's a modern cell there's a little DNA we see they kind of Escape right and now become their own virus their own particle right and then the self-replicating hypothesis um pool of replicons we kind of saw this with our pool of of procaryotes with the ring model of evolution in the three domains um this would kind of be analogous to that so you have a pool of these replicons or these replicating um units of material and somehow they became encased and we've got these virus-like entities they increased in complexity and emerging translated and then started infecting a cell okay viral Basics so what is a virus it's a non-cellular biological entity um meaning it has no cellular structure so they have a nucleic acid core they have an outer protein coating called a capsid and they have a phospholipid membrane called an envelope but they don't always have an envelope not all have an envelope so it's not always present so when I learned early virus classification is was it enveloped or not so we had enveloped and non-enveloped viruses um and let's talk about one big thing complexity is not associated with the host make sure you remember this so bacterio phases so bacteria or virus of bacteria can be some of the most complicated out there and bacteria obviously are not super complicated compared to a large multicellular organism right so so just keep that in mind that the complexity of the virus isn't directly associated with complexity of the host so here we have not envelope this is what I always think of when I think of a virus the little alien lifecraft here so it's got the head right and it's got the genome in it Little Neck little endplate and what it does is it lands on a host cell and then ejects that nuclear or that genome into the cell right this is what I always think of now currently because we've seen images of Corona viruses and things like that uh we've seen these kind of circular viruses have these Spike proteins if you pay attention to the news covid type research you learn all about spikee proteins um and then they have their their genome RNA in the middle right and they can they can then get that in and here's their capsid protein here's the capsid of this one okay moving on here we go they can be complex or not complex um so notice we've got our bacterial phase ouro virus here's our capsid D different glycoproteins on the outside and then we have our HIV retrovi so which is a retrovirus so it's got these glycoproteins it's got this capsid RNA different transcripts an envelope and so on okay there are lots of different viral shapes some can be helical like many plant viruses iosa hedral so roughly sphere like polio virus and herpes viruses enveloped things like HIV different animal viruses and head and tail that infect the bacteria so we can go to that and we can see all these different shapes um and you can go there up okay so here's a helic like edro in the complex viruses can have either RNA or or DNA um but either way it's contained within a core so their genome is in the virus core so we have RNA viruses which only have RNA and so RNA viruses must encode their own enzymes to replicate RNA to either RNA or RNA to DNA if they're a retrovirus um they're more prone to change so RNA polymerases make more errors now what does that mean for the virus so when we think of of human cells right right so if in the replication process there's an error right that stops and that cell dies in most cases um it can tolerate some some mutation um and we know that there's lots of cases where we see mutated uh individual cells but overall if our replication is incorrect then it ends ends in a it stops right and so what happens is Arna viruses are incredibly tolerant of those errors right and so they can evolve really rapidly and they can have a lot of mutations to the point where we can trace individual um hosts based on creating a philogenetic tree of the virus and we can look at where those mutations occurred and we can see host to host to host how it's moved or how it's um evolved okay DNA viruses so in this case the viral DNA tricks the host cell into replicating its genome where the RNA had asked to splice in um DNA just gets it to do that and so there's a really good video here kiss of death is BL that in get rid of that nobody needs to see that um we can actually watch this video and use this you can see different um examples just to look at different ways that viruses enter all right virus classification one we can look at structure so enveloped or not this is the way I said I learned this right pretty simple is it enveloped or not what's the capsid look like is it RNA or DNA that's all um did as I learned this um now we have the Baltimore classification that looks like morphology genetics how mRNA is produced and so on and we get groups one through seven I mean you can go to table 23.1 for examples on that so again Kiss of Death here switching between his presentation but it worked so we have a different group one group two group three group four five six seven I encourage you to go ahead and look at these this is the the viral Zone um website but we're looking at the Baltimore classification so if you just um search Baltimore classification of viruses you can probably learn a whole bunch about this okay viral Cycles so we start with the permissive which is a host cell where the virus replicates and permissive cells have to have a receptor so we say permissive cell has a receptor now I talked about the the evolution in the of the Delta 32 deletion or the ccr5 protein um where those individual were probably immune to the plague and are now immune to HIV that means those cells are not permissive they don't have the receptor for that virus right so attachment so viruses have to attach to that cell and it has to have this specific receptor so permission and attachment go together so it has to have the receptor um be the virus has to be able to to attach or to find that receptor then it has to attach to that specific receptor it enters via endocytosis in plant and animal cells and membrane fusing in in other cells um and so endocytosis into cell so it goes into the cell then under goes replication and assembly so the viral mRNA the reverse transcription things like HIV and then it has to leave so it has to egress so it has to release new Vons and it can do this through Lis and apoptosis or through budding and there's a really good video on HIV reproduction um that we don't have time for in this mini lecture so permission attachment entry replication egress what's the first step permission okay viral diseases we can see acute viral diseases where symptoms get worse over a short period of time before elimination from the body so think about you get that 24-hour bug um that's acute right symptoms get really bad and then your body's able to fight it off and get rid of it and you're better chronic would be long-term things we're now hearing a lot about long-term covid um things like that so the long-term infections intermittent symptoms then things that kind of come and go and and then we have a lot of individual hosts that will be asymptomatic so they will show no symptoms whatsoever um but they can really spread a lot of the new virus or the virus to a lot of other people and then we have oncogenic viruses so some that can cause cancer and so the most common of these is a human Poma virus or HPV which now we know we have vaccines for so figure 21.13 in your book you can see all the different virus not all of them obviously um but lots of different viruses um and what areas they impact so skin infections hepatitis cardiovascular viruses ritis um pneumonia things like that prevention of viral disease how do we prevent viruses well we know prevention can be a lot of different ways it can be simply um people who are infected not going out in areas where they're going to infect new people that's an easy way to prevent uh viruses but you as someone who's not infected can't really help that so what can we do for people that uh that can't help that well one we have vaccination so vaccine consists of a live um um virus a killed virus or molecular subunits of a virus so some things that that we look at so we have live strains um so LIF strain viruses you get a dose of of the virus a really light dose um so that your body can recognize it and build the immune uh cells in response necessary um or we can see some some back mutation um earlier versions of that virus and again we have a high mutation rate of viruses right so think about your flu vaccine if you get that every year it's based on the previous year's most common one um but because that influenza virus can can mutate so fast and we can get so no so many new strains um you're protected against the most some of the most common of of before but not guaranteed that that it's not a new that you don't get a new string however they're really effective and generally one in five who get the vaccine um only end up getting the virus and then we have antiviral drugs so I guess we should talk about molecular subun units sorry um so we can create vaccines based on things like um the molecular makeup of things like the spike proteins in the in the Corona virus right so we can create in a lab molecular subunits of those Spike proteins which which is on the virus and it identifies the virus as a virus and that's how your body identifies the virus and so if we just give your body those things that it uses to identify the virus then it can mount and create those cells to remember it so that it attacks it much faster once you get infected right and so that's what happens you get infected your body takes some time to build the immune cells and to recognize um those cells to have the memory cells so that the next time you encounter that virus it fights it off much faster right so it avoids you having to get the virus in the first time all right antiviral drugs manage symptoms they're not Curative and they may control viral replication rates so growing up in the 80s uh 1980s during the HIV pandemic or epidemic um we knew going in that if you got HIV that was pretty much a death sentence at that time that you you would develop AIDS and die um there wasn't really a drug out there to control the replication rates um and it was pretty scary and now we see there's people alive years and years later um who are still surviving with HIV so it's an example of the somewhat what the drugs can do okay vaccines boost immunity prevent infection action of the antiviral drug we can see they try to block it as it leaves to control that level all right let's talk about non-virus disease causing organisms um some fascinating things here these are called prons they cause transmissible sponger form and Seath cephalopathy or tsse uh this would be things like chronic wasting disease crutch jaob disease Kuru bovine spongiform and sopath madcow scrapey so on so crazy thing about prons is there're not even DNA right they're just proteins that cause other proteins to misfold so proteins have to be folded a certain way um structure to serm function so the protein molecules fold a certain way it functions normally the prion causes it to misfold and then it doesn't function um they're generally pretty fast acting and they're always fatal so right now chronic wasting disease thing I'm most familiar with um it's on a landscape it can survive in the soil for a long period of time um it would to be near a facility that was working with Scrapy when it came out so that was in sheep um and so what we found with prons is burning carcasses doesn't necessarily kill them burying them obviously they can stay in the soil and then some animal dig them up and they can spread them around um so you have to denature them and what denatures them kind of like think about in your in your digestive system how you denature proteins it's with acid and enzymes so if you think of a lot of carcasses being disposed of by having to be dissolved in acid and enzymes you can imagine what a what an issue that is um okay so that ends mini lecture number 11 so that's all we're going to do with viruses um so again if you found the viruses interesting the book your book is a really good source um and you can look some more up and we are going to move into the procaryotes in mini lecture 12