Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies The First Single-Celled Creatures Chapter 13 Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Outline Structure of Bacteria Bacterial Reproduction Bacterial Metabolism Bacterial Lifestyles Viruses  Structure  Reproductive Cycles  HIV  Disease Viruses

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies The Simplest Organisms Bacteria have been plentiful on earth for over 3.5 billion years.  For at least 2 billion years, bacteria were the only organisms that existed. - Play key role is material recycling. - Photosynthetic bacteria were partly responsible for introduction of oxygen into earth’s atmosphere.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Structure of Bacterium Small, simply organized, single cells lacking an organized nucleus.  Rod shaped (bacilli)  Spherical (cocci)  Spirally coiled (spirilla) Classified by presence / absence of lipid polysaccharide membrane.  Gram-positive (no outer membrane)  Gram-negative (possess outer membrane)

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Structure of Bacteria Many bacteria possess threadlike flagella to aid in movement.  Shorter outgrowths (pili) act as docking cables and help in attachment.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Bacterial Reproduction Binary Fission - individual cell increases in size and divides in two.  Some bacteria can pass plasmids from one cell to another (conjugation).

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Comparing Bacteria to Eukaryotes Bacterial Metabolism  Autotrophs - Obtain energy from inorganic carbon dioxide.  Heterotrophs - Obtain carbon from organic molecules such as glucose.  Photoautotrophs - Use sunlight to build organic molecules from carbon dioxide.  Chemoautotrophs - Obtain energy by oxidizing inorganic substances.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Bacterial Metabolism  Photoheterotrophs - Use light as source of energy but obtain carbon from organic materials.  Chemoheterotrophs - Obtain both carbon and energy from organic molecules.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Importance of Bacteria Material Recycling  Carbon  Nitrogen Genetic Engineering Diseases  Anthrax  Plague  Pneumonia

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Kinds of Bacteria Over 4,800 named species of bacteria. Separated into archaebacteria and eubacteria kingdoms.  Differ in fundamental ways: - Cell walls - Plasma membrane - Gene translation machinery - Gene architecture

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Bacterial Lifestyles Archaebacteria  Methanogens - Use hydrogen gas to to reduce carbon dioxide to methane.  Thermoacidophiles - Occupy hot, acidic habitats. Eubacteria (Most common)  Hetrotrophic and Photosynthetic - Cyanobacteria (photosynthetic)  Heterocysts - nitrogen-fixing cells

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Discovery of Viruses Viruses are parasitic segments of DNA or RNA wrapped in a protein coat.  Non-living and can only reproduce in cells.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Structure of Viruses Capsid - Protein sheath around nucleic acid core.  Envelope - membrane-like structure surrounding capsid. Bacteriophages - Bacterial viruses.  Very complex Animal and Plant Viruses  Helical - Rod-shaped  Isometric - Spherical

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Bacterial Structure

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Bacteriophages Enter Cells Lytic Cycle  Tail fiber contacts lipoproteins of host bacterial cell wall.  Head contents injected into host cytoplasm.  Viruses multiply within infected cell.  Rupture cell wall and spread to other cells.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Bacteriophages Enter Cells Lysogenic Cycle  Integrate nucleic acid into genome of infected host cell. - Prophage  May later exit genome and initiate virus replication.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Lytic and Lysogenic Cycles

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Animal Viruses Enter Cells Human Immunodeficiency Virus  Clinical symptoms of AIDS do not begin to develop until generally eight to ten years after infection with HIV.  Attachment - Virus circulates throughout entire body but will only infect certain cells (macrophages).  Uptake and recycle organic debris.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Human Immunodeficiency Virus Gp120 protein spikes found on HIV surface.  When gp120 contacts cell surface marker matching its shape, it adheres to the cell and infects it. - Fits CD4 marker on macrophages.  After docking onto CD4, HIV requires second receptor protein CCR5 to pull itself across plasma membrane.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Human Immunodeficiency Virus Once inside macrophage, HIV sheds protective coat, releasing RNA.  Reverse transcriptase enzyme binds to tip of viral RNA and synthesizes DNA matching contaminating viral RNA. - Produces many new mutations.  Eventually, HIV alters gene for gp120 and causes it to produce a new form that binds to CXCR4 receptors on T cells.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies HIV Infection Cycle

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Disease Viruses Influenza  RNA animal viruses - Types A,B and C  Subtypes - Differ in protein spikes. - hemagglutinin - neuraminidase  Readily re-assorted by genetic recombination.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Disease Viruses Smallpox  Caused by inhaling variola virus. - Characteristic fever and skin rash symptoms appear after about 12 days.  15 million cases worldwide in  Still exists in two high-security laboratories.  Bioterrorist threat ?

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Disease Viruses Emerging Viruses - Originate in one organism and pass to another.  Represent considerable threat in age of rapid transportation. - Filamentous viruses attacking human connective tissue.  Ebola.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Prions and Viroids Transmissible spongiform encephalopathies (TSE’s) are fatal brain disease causing small cavities as neurons die producing marked spongy appearance.  Mad Cow  Creutzfeldt-Jakob Caused by protein “proteinaceous infectious particle.” Viroids - naked molecules of RNA important infectious disease agents in plants.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Review Structure of Bacteria Bacterial Reproduction Bacterial Metabolism Bacterial Lifestyles Viruses  Structure  Reproductive Cycles  HIV  Disease Viruses

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Copyright © McGraw-Hill Companies Permission required for reproduction or display