Chapter 20 Bacteria and Viruses 1/19

 NOTICE: Honors Biology and Biology Students – your book does not contain the chapter we are about to cover. All information needed for the test is in this powerpoint!

Let’s continue the crazy q’s!  “I noticed that global warming increased after daylight saving time started in Well, duh! More daylight is going to make the world hotter, isn’t it?” From a reader in Altadena, California

19.1 Bacteria  Prokaryotes  Single celled organisms lack a nucleus  1 to 5 micrometers (in general)  Classified into 2 kingdoms  Eubacteria  Archaebacteria 3/19

20.1 Bacteria (continued)  Eubacteria  Larger group  Wide range of organisms  Usually surrounded by a cell wall  Protects and determines shape Contains peptidoglycan (a carb)  Inside the cell wall is a cell membrane surrounding the cytoplasm 4/19

 Archaebacteria  Equally small in size  Have cell wall that is chemically different from Eubacteria’s cell walls  Live in extremely harsh environments  Oxygen free  Methane  Thick mud  Salty  HOT 5/ Bacteria (continued)

 KEY:  Archaebacteria lack peptidoglycan and have different membrane lipids  The DNA sequences of Archaebacteria genes are more like those of eukaryotes than those of Eubacteria.  Identifying Prokaryotes  KEY: Are id’ed by characteristics: shape, cell wall’s chemical nature, how they move, and how they obtain energy. 6/ Bacteria (continued)

 Shape  Cocci  Bacilli  Spirilla  Cell Wall’s Chemical Nature  Gram Stain Red/pink is negative and Purple is positive  Crystal violet (stain), iodine, alcohol, safranin (counterstain) Gram positive cells have a thick peptidoglycan wall Gram negative cells have thinner walls inside a lipid layer (COOH dissolves lipid, removes crystal violet) 7/ Bacteria (continued)

Click here for a video on Gram Staining approx 7 min

 Movement  Don’t  Propelled by flagella  Lash/snake/spiral forward  Glide  The way they obtain energy  Metabolic Diversity Prokaryotes are in 2 groups, depending on energy and if they use O 2 for respiration Heterotrophs Autotrophs 8/ Bacteria (continued) Click here for a video showing movement in a microscopic view of worm compost showing ciliate protozoa, flagellate protozoa, and bacteria

 Heterotrophs  Get energy from organic molecules  Chemoheterotrophs Take in organic molecules  Photoheterotrophs Use light for energy, also need organic compounds  Autotrophs  Makes own food from inorganic molecules  Chemoautotrophs Make organic carbon molecules from CO 2, need chemicals (like ammonia, sulfur) not light  Photoautotrophs Use light energy and a carbon source 9/ Bacteria (continued)

 Releasing Energy  Bacteria constantly need energy  Need to release the energy by cellular respiration, fermentation, or both  Obligate Aerobes Require O 2 to live  Obligate Anaerobes Require absence of O 2  Facultative Anaerobes Survives w/ or w/o O 2 (switch b/w cell resp & ferm) 10/ Bacteria (continued)

 Growth and Reproduction  In favorable conditions, bacterial growth can be very fast (19 minutes!)  In 48 hrs, 1 bacteria could divide so many times that the mass would be about 4000 times the mass of the Earth  With so many bacteria, why doesn’t that happen ? Food availability & waste accumulation stops growth 11/ Bacteria (continued) Click here for a video showing bacterial division

 Binary Fission  Asexual reproduction  Bacteria divides in half making 2 identical daughter cells  Conjugation  Hollow bridge forms between 2 cells, genes move across Transfer of genetic material increases diversity  Spore Formation  Unfavorable conditions, some bacteria form Endospores form when bacteria make a thick internal wall, enclosing its DNA and a portion of its cytoplasm Can stay as a spore for months or years Until favorable conditions occur again 12/19 Bacillus anthracis 20.1 Bacteria (continued)

 Bacteria are IMPORTANT  They supported Ms. McKenna’s family &  Are producers (capture energy by photosynthesis)  Decompose Break down nutrients in dead matter and atmosphere Basically recycle nutrients (wood, sewage treatment)  Nitrogen fixation Bacteria in soil convert N gas to a usable form 13/19 Nitrogen-fixing bacteria on a petri dish 20.1 Bacteria (continued)

 Human uses Foods and beverages Digest petroleum Remove wastes/poisons from water Mine minerals Synthesize drugs/chemicals Make vitamins the body can’t produce itself Make enzymes 14/ Bacteria (continued)

20.2 Viruses  What is a virus?  Particles of nucleic acid, protein, sometimes lipids  Usually a core of DNA or RNA surrounded by a protein coat.  Can reproduce only by infecting living cells  Vary in size and structure  Common – enter living cells, use the cell to produce more viruses 15/19 Human Influenza Virus Click here for viral art web article

20.2 Viruses (continued)  Simplest have only a few genes, others may have >100 genes  Capsid = virus protein coat  Enables virus to enter the host cell. Tricks cell into allowing it in. Cell transcribes & translates the viral DNA or RNA and viral capsids. Sometimes host cell is destroyed. Viruses bind precisely, so they are highly specific to cells the infect Bacteriophage – virus that infects bacteria 16/19

20.2 Viruses (continued)  Viral Infection–2 processes once it’s in  Lytic Infection Makes copies of itself Causes host cell to burst  Lysogenic Infection A virus integrates its DNA into the host’s DNA Viral genetic info replicates along with the host cell’s DNA Virus remains inactive over a period of time Viral DNA that embeds itself is called a prophage Prophage–can remain inactive part of host’s DNA for a long time. May not stay in that form forever 17/19 TEM of bacterial lysis due to T4 phage infection

20.2 Viruses (continued)  Retroviruses  Contain RNA as their genetic info  When they infect, they produce a DNA copy of their RNA.  Acts like a prophage - inserts into the host cell’s DNA.  Can remain dormant for some time before becoming active, producing new viruses, causing death of host cell. 18/19

20.2 Viruses (continued)  Retroviruses (continued)  Called retro because their genetic info is copied backwards  RNA to DNA.  HIV is a retrovirus  Viruses and Living Cells  Viruses are parasites!!!  They depend upon another living organism for their existence, harming that organism in the process 19/19

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