2What is a Virus?A virus is a noncellular particle made up of genetic material and protein that can invade living cellsStructureCore of nucleic acid surrounded by a protein coat called a capsidCapsid can be DNA or RNA, but not bothCore can be several to several hundred genes
3SO HOW BIG ARE VIRUSES??? Viruses are REALLY small. They are much smaller than bacteria.They can only be seen with an electron microscope.
4Bacteriophage Bacteriophages are viruses that infect bacteria Head – capsid and DNATail – with fibers to attach to bacteria
5T group Most commonly studied are T group – T1, T2, T3, T4 etc... T4 has a DNA core within a protein coat, and tail with tail fibers to attach to bacteria.
6Viral shapes Variety of shapes Rod Tadpole Many sided, helical or cubelike
8SHAPES MAY DIFFER BUT… All viruses have 1. Chromosome-like part that carries hereditary information – The Core2. Protein coat: Protects hereditary information and provides the shape! The CapsidTobacco MosaicVirusT4 BacteriophageInfluenza VirusRNACapsidproteinsHeadTail sheathDNATail fiberRNACapsidSurfaceproteinsMembraneenvelope
9ROUND VIRUSESHerpes virusThere are two types:Genitaloral
12Is this why viruses infect us? YES!Viruses need living organisms in order to reproduce and form more viruses!Injecting DNAvirus
13Virus SizeSize – 20 to 400 nanometers (one nanometer is one billionth of a meter)Specificity – usually infect specific organismsCannot infect animals if it infects plantsSome can infect wider varietyRabies – all mammals, some birds
14VIRUSES ARE SPECIFIC IN THE CELLS THEY INFECT Tobacco mosaic virus: only tobacco plants…not wheat or cornRabies: only nervous system cells of mammalsCommon cold: infects cells on airway passage to lungs
15Lytic InfectionCause cells to lyse or burstInfection – chance contact virus with right kind of bacterium. Virus attaches to bacterium and injects its DNA. Most times, complete virus particle does not enter.Growth – Bacterium can’t tell difference between bacterial and viral DNA. RNA polymerase causes mRNA to be made from cell for virus. Viral DNA takes over and produces more DNA and viral proteins.Replication – Virus uses bacterial material to make thousands of copies of the protein coat and DNA. Cell becomes filled with virus particles. (All three stages can happen with E. coli within 25 minutes!)DNA serves as central point for virus particles to be assembled. Cells fill with virus and lyse (burst). New viruses can now infect new cells.
16SO HOW DO VIRUSES CAUSE DISEASE? Section 19-3Bacteriophage protein coatBacteriophage DNABacterialchromosomeBacteriophage attaches to bacterium’s cell wallBacteriophage enzyme lyses thebacterium’s cell wall, releasingnew bacteriophage particles thatcan attack other cells.Lytic CycleBacteriophage injects DNA into bacteriumBacteriophage proteins and nucleic acids assemble into complete bacteriophage particlesBacteriophageBacteriophage DNABacteriophage proteinBacteriophage takes over bacterium’s metabolism, causing synthesis of new bacteriophage proteins and nucleic acids
17Retroviruses RNA viruses When they infect a cell, they produce DNA copies of their RNA genes.Retroviruses have their genetic information copied backwards. RNA DNAOne retrovirus is HIV. Others cause cancer in animals and humans.The theory is that viruses were not the first living things. They are dependent on living things to survive.
18EUBACTERIA AND ARCHAEBACTERIA: The two bacterial kingdomsBacteria on a pin head
19Eubacteria “True” bacteria largest Kindgom of prokaryotes generally surrounded by cell wall composed of complex carbohydrateshave a cell membrane (some have 2 cell membranes)Some have flagella for movementFound everywhereSome produce diseaseSome photosyntheticsome very useful – cheese is just one example
20PROKARYOTIC CELLSProkaryote – what does that mean? Classification of ProkaryotesAll prokaryotes were in kingdom Monera.Now – 2 kingdomsEubacteria and archaebacteria
21ArchaebacteriaArchaebacteria includes organisms that live in very harsh environmentsMethanogens – live in oxygen free environments – mud, digestive tracts of animalsExtremely salty environmentsHot springs
25Cell Wall Chemical nature – Gram staining Hans Christian Gram 2 dyes – crystal violet (purple) and safranine (red)bacteria either take one or the otherIf only one thick layer of carbohydrate and protein molecules outside the cell membrane – picked up crystal violet – appeared purple – GRAM POSITIVEIf cell had 2nd, outer layer of lipid and carbohydrate – picked up safranine – appeared red GRAM NEGATIVE
26Bacterial movement propelled by flagella lash, snake, or spiral forwardno movement
27Bacterial Respiration Obligate aerobes – require oxygenObligate anaerobes – must live in absence of oxygenexample is Clostridium botulinumFacultative anaerobes – can live with or without oxygen
28Reproduction Some can reproduce every 20 minutes Held in check by food and production of wastes Types:Binary FissionReplication of DNA and division in halfAsexualConjugationSexual – involves the exchange of genetic materialLong bridge of protein forms between the cellsDonor genetic information transferred to recipient through bridgeRecipient cell has different genes at the end than it did to begin with
29Importance of Bacteria Used in production of products we use every dayYogurtCheeseButtermilkSour creamPicklesSauerkrautVinegarWineIndustrydigest petroleumremove wastes and poisons from watersynthesizing drugs – through genetic engineering
30Symbiotic Relationships (mutuallism) E. coli in humans – help us digest food – make vitamins we can’t, we give them a home, food, and transportationBacteria in the intestines of cattle allow them to break down cellulose (in grass and hay)
31Bacteria in the Environment Bacteria are like the stage hands that allow the show to go on without being seen (or always given the credit)Bacteria recycle and decompose dead materialSaprophytes – organisms that use the complex molecules of a once living organism as their food source
32Sewage decompositionSewage treatment – bacteria is added directly to the raw sewageHow does a septic tank work?
33Nitrogen FixationAll organisms are TOTALLY dependent on monerans for NitrogenAll Plants need nitrogen to make amino acids (-NH2)Because animals eat plants, they get their proteins from plantsWhat percentage of the air is Nitrogen?Plants, and most other organisms cannot use this directlyNeed Nitrogen to be “FIXED” chemically as ammonia
34Nitrogen FixationScientists can make synthetic nitrogen containing fertilizers by mixing Nitrogen and Hydrogen gases, heating to 500 degrees C and compressing it to 300 X normal atmospheric pressure – dangerous, expensive, time consumingMany cyanobacteria can take nitrogen from the air and convert it to a useable form – this is called Nitrogen FixationBacteria are the only organisms that can do this.Some plants have a symbiotic relationship with nitrogen fixing bacteriasoybean – Rhizobium grows in nodules around roots
35Diseases caused by Viruses and Monerans only a small number of viruses and bacteria can cause diseasePathogens – organisms that cause diseaseAll viruses infect living cellsDisease occurs when infection causes damage to the cells
36Viruses and Disease Examples are: Small Pox Polio Measles AIDS Mumps InfluenzaYellow FeverRabiesCommon ColdEbola etc…
37Vaccine The body’s own defenses must be used Vaccine – dead or weakened viruses that stimulate the bodies defense systemSymptoms can be treated sometimes, but once someone is infected by a virus, there is not much science can do
392 ways bacteria cause disease Damage cells and tissues of infected organisms directly by breaking down cellsReleasing toxins (poisons)Many bacteria can live without a host organism (on a petri dish)Rickettsiae cannot live outside a host cell. They have leaky cell wallsRickettsiae cause Rocky Mountain Spotted Fever, typhus, and Legionnaire’s disease
40Measures to fight bacterial infection include: Antibiotics – drugs and natural compounds that attack and destroy bacteria in the bodyNOT Effective against viruses