18.1 Studying Viruses and Prokaryotes
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18.1 Studying Viruses and Prokaryotes KEY CONCEPT Infections can be caused in several ways. 18.1 Studying Viruses and Prokaryotes Viruses, viroids, and prions can all cause infection. • Any disease-causing agent is called a pathogen. 1 nanometer (nm) = one billionth of a meter 100 nm eukaryotics cells 10,000-100,000 nm viruses 50-200 nm prokaryotics cells 200-10,000 nm viroids 5-150 nm prion 2-10 nm 18.1 Studying Viruses and Prokaryotes • A virus is made of DNA or RNA and a protein coat. – non-living pathogen – can infect many organisms • A viroid is made only of single-stranded RNA. – causes disease in plants – passed through seeds or pollen 18.1 Studying Viruses and Prokaryotes • A prion is made only of proteins. – causes misfolding of other proteins – results in diseases of the brain 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Characteristics of Viruses • NO - nucleus, cytoplasm, organelles, or cell membrane • NOT capable of carrying out cellular functions • NOT alive! 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Viruses Obligate Intracellular parasites - depend on host cells for replication • Spread by wind, water, food, blood or other bodily secretions • Named for the disease they cause or the tissue they infect 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Viral Structure Nucleic acid • Either DNA or RNA, but not both • Helical, closed loop, or a long strand • Protein coat surrounds nucleic acid (capsid) • Some have a membrane like structure outside capsid called an envelope • Ex: influenza, herpes, chickenpox, HIV 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Viruses differ in shape and in ways of entering host cells. enveloped (influenza) capsid nucleic acid lipid envelope polyhedral (foot-and-mouth disease) helical (rabies) Surface proteins capsid nucleic acid surface proteins lipid envelope surface proteins capsid nucleic acid 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes • Bacteriophages – virus that infects bacteria. capsid DNA tail sheath tail fiber 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes colored SEM; magnifications: large photo 25,000; inset 38,000x 18.1 Studying Viruses and Prokaryotes Flu Attack • http://www.youtube.com/watch?v=Rpj0emEGShQ 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Attachment to a host cell • Virus - recognize and attach to a receptor site on the plasma membrane of host • Protein on capsid locks with receptor site • Each virus has a specifically shaped attachment protein (jigsaw puzzle) – Can only attach to a few hosts 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Viruses cause two types of infections. 1. Lytic 2. Lysogenic 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Lytic cycle • Virus invades a host cell • produces new viruses (transcription, translation and assembly) • immediately destroys host releasing newly formed viruses - virulent virus • Lysis - cell disintegration 18.1 Studying Viruses and Prokaryotes host bacterium Lytic Cycle The bacterophage attaches and injects it DNA into a host bacterium. The host bacterium breaks apart, or lyses. Bacteriophages are able to infect new host cells. The viral DNA forms a circle. The viral DNA directs the host cell to produce new viral parts. The parts assemble into new bacteriophages. 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Lysogenic Cycle • Infect a cell without causing its immediate destruction - temperate virus • Viral DNA is integrated into hosts DNA – prophage • Can stay in host cell for an extended period of time • Every time host cell reproduces = prophage is replicated • Every cell is also infected • Trigger will activate lytic cycle later • Ex: Herpes, chicken pox 18.1 StudyingCycle Viruses and Prokaryotes Lysogenic The prophage may leave the host’s DNA and enter the lytic cycle. The viral DNA is called a prophage when it combines with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage. Although the prophage is not active, it replicates along with the host cell’s DNA. 18.2 Structure Viruses and Reproduction 18.1Viral Studying and Prokaryotes Retroviruses • RNA viruses • Most complex replication cycle • Ex: HIV Once inside host retrovirus makes DNA • Reverse transcriptase – produce DNA from viral RNA • Then it is integrated and becomes a prophage If reverse transcriptase is in a person then they have been infected with a retrovirus 18.3 Diseases Viruses and Prokaryotes 18.1Viral Studying Viruses cause many infectious diseases 18.3 Diseases Viruses and Prokaryotes 18.1Viral Studying Common human viral diseases • Rabies - transmitted by the bite of an infected animal – virus is carried in saliva – virus travels from wound to central nervous system – fever, headache, throat spasms, paralysis, coma 18.3 Diseases Viruses and Prokaryotes 18.1Viral Studying Chicken pox • Virus multiplies in lungs, uses blood vessels to reach skin • Fever, skin rash • Transmission from direct contact with the skin rash and through the air • Recover - usually followed by a lifelong resistance to re-infection • Can persist in nerve cells as a prophage - cause shingles later in adulthood • Fever is higher • Immune system weakens • Pneumonia may occur 18.3 Diseases Viruses and Prokaryotes 18.1Viral Studying HIV • Human immunodeficiency virus • Infects white blood cells • Prophage eventually enters lytic cycle leading to rapid decrease in white blood cells • AIDS - acquired immunodeficiency syndrome • Person dies from other infections 18.3 Diseases Viruses and Prokaryotes 18.1Viral Studying Prevention and Treatment Treatment • Antiviral Drugs- interfere with viral nucleic acid synthesis Prevention • Vaccination - stimulates body’s immune system to provide protection against that pathogen 1. Inactivated - viruses do not replicate in a host system 2. Attenuated - viruses are genetically altered so that they are incapable of causing disease under normal circumstances • (preferred - protection is greater and lasts longer) 18.3 Diseases Viruses and Prokaryotes 18.1Viral Studying 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes KEY CONCEPT Bacteria and Archaeabacteria are both singlecelled prokaryotes. 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Bacteria Classification: • Kingdom: Monera • Eubacteria (germs) & Archaeabacteria 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Microscopic Prokaryotes • Unicellular • No nucleus • No membrane-bound organelles • Alive! • Can do cell functions! 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Archaebacteria: The extremists • Unusual lipids (fats) in their cell membranes • Introns (junk) in their DNA • Cell wall lacks Peptidoglycan (protein carbohydrate compound found in cell walls of eubacteria) 18.4 and Archaeabacteria 18.1Bacteria Studying Viruses and Prokaryotes Extreme Environments: Examples Methanogens - convert hydrogen and carbon dioxide into methane gas • Live in anaerobic conditions ex: bottom of a swamp and sewage, intestinal tract of humans and other animals Extreme Halophiles - live in high salt concentrations • Use salt to generate ATP 18.4 and Archaeabacteria 18.1Bacteria Studying Viruses and Prokaryotes Thermoacidophiles - live in extremely acidic environments that have extremely high T • T up to 110 degrees C (230 degrees F) • Ph less than 2 • Hot springs, volcanic vents, hydrothermal vents 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Eubacteria commonly named for shape • • • • • • Rod-shaped - bacilli Spiral - spirilla or spirochetes Spherical – cocci Streptococci – chains of cocci Staphylococci – grapelike clusters of cocci Vibrio - coma shaped Lactobacilli: rod-shaped Enterococci: spherical Spirochaeta: spiral 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Eubacteria: Streptococci Staphylococci 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Eubacteria structure • Cell membrane - contains enzymes that catalyze the reactions of cellular respiration • DNA is a single, closed loop 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes • Capsule - outer covering made of polysaccharides (sugars) protect it against drying out or harsh chemicals • Pili - short hair-like protein structures found on the surface of some species of bacteria *help bacteria adhere to host cells *used to transfer genetic material 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Movement Structures • Flagella - turn and propel the bacterium (single or multiple) • Layer of slime - wavelike contractions of outer membrane propel it • Spiral - shaped bacteria move by corkscrew-like rotation 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes pili plasma membrance chromosome cell wall plasmid This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences. flagellum 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Endospores • Dormant structure that is produced by some (grampositive) bacterial species that are exposed to harsh environmental conditions • Help bacteria resist high temperatures, harsh chemicals, radiation, drying and other environmental extremes • Conditions become favorable endospore will open, allowing the living bacterium to emerge and multiply 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes • Gram staining identifies bacteria. – stains peptidoglycan – gram-negative - stains pink - less peptidoglycan – gram-positive - stains purple - more peptidoglycan Gram-negative bacteria have a thin layer of peptidoglycan and stain red. Gram-positive bacteria have a thicker peptidoglycan layer and stain purple. 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Gram-positive bacteria Examples: • Streptococci - causes strep throat • Grow in milk producing lactic acid yogurt • Lactobacilli - found on teeth cause tooth decay • Actinomycetes - form branching filaments, found in soil, and produce antibiotics • Exotoxin - secreted into the environment and cause disease (Tetanus) 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Gram-Negative Bacteria Examples: • Escherichia coli - lives in human intestine where it produces vitamin K and assists enzymes in the breakdown of foods • Salmonella - responsible for food poisoning • Chemoautotrophs • Endotoxin - Not released until bacteria die 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes *Gram positive and gram negative have different susceptibilities to: • antibacterial drugs • produce different toxic materials • react differently to disinfectants 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Heterotroph • Saprophyte - feed on dead and decaying material • parasitic Autotroph • Photoautotrophs - sunlight to make E (Cyanobacteria) • Chemoautotrophs – chemicals to make E 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Eubactria can be grouped by their need for oxygen. • Obligate anaerobes - are poisoned by oxygen • Obligate aerobes - need oxygen • Facultative aerobes - live with or without oxygen 18.4 and Archaeabacteria 18.1Bacteria Studying Viruses and Prokaryotes Examples: • Obligate Anaerobes - Clostridium tetani – Tetanus • Facultative anaerobes - E. coli • Obligate Aerobes - Mycobacterium tuberculosis Tuberculosis 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Spirochetes • • • • • Gram-negative, spiral shaped, heterotrophic bacteria Aerobic or anaerobic Move by corkscrew rotation Live freely, symbiotically, or parasitically Treponema pallidum causes syphilis 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes Cyanobacteria (Blue-Green algae) • Photosynthetic • Encased in a jellylike substance and often cling together in colonies Eutrophication - population bloom - sudden increase in the number of an organism due to large increase of nutrients 18.4 and Archae 18.1Bacteria Studying Viruses and Prokaryotes Asexual Reproduction • Binary Fission • rapid 18.5 18.4 Beneficial and Roles Archaebacteria of Prokaryotes 18.1Bacteria Studying Viruses and Prokaryotes Genetic Recombination • Transformation - bacterial cell takes in DNA from external environment • Conjugation - two living bacteria bind together and one bacterium transfers genetic information to the other • Pili binds to bacteria to form a conjugation bridge 18.4 and Archaebacteria 18.1Bacteria Studying Viruses and Prokaryotes conjugation bridge TEM; magnification 6000x 18.5 Roles of Prokaryotes 18.1Beneficial Studying Viruses and Prokaryotes KEY CONCEPT Prokaryotes perform important functions for organisms and ecosystems. 18.5 Roles of Prokaryotes 18.1Beneficial Studying Viruses and Prokaryotes Prokaryotes provide nutrients to humans and other animals. • Prokaryotes live in digestive systems of animals. – make vitamins – break down food – fill niches 18.5 Roles of Prokaryotes 18.1Beneficial Studying Viruses and Prokaryotes • Bacteria help ferment many foods. – yogurt, cheese – pickles, sauerkraut – soy sauce, vinegar 18.5 Roles of Prokaryotes 18.1Beneficial Studying Viruses and Prokaryotes Prokaryotes play important roles in ecosystems. • photosynthesize • recycle carbon, nitrogen, hydrogen, sulfur • fix nitrogen 18.5 Roles of Prokaryotes 18.1Beneficial Studying Viruses and Prokaryotes • Bioremediation uses prokaryotes to break down pollutants. – oil spills – biodegradable materials 18.6 Diseases and Antibiotics 18.1Bacterial Studying Viruses and Prokaryotes KEY CONCEPT Understanding bacteria is necessary to prevent and treat disease. 18.6 Diseases and Antibiotics 18.1Bacterial Studying Viruses and Prokaryotes Some bacteria cause disease. 18.6 Diseases and Antibiotics 18.1Bacterial Studying Viruses and Prokaryotes Bacteria cause disease • • • • Plants and animals Carried in air, food, and water Sometimes invade through skin wounds Growth of bacteria can interfere with normal function of body tissue • Or it can release a toxin that directly attacks host 18.6 Bacterial Diseases and Antibiotics 18.5 Beneficial Roles of Prokaryotes 18.1 Studying Viruses and Prokaryotes Bacterial Diseases • Transmitted by ticks • Borrelia burgdorferi - causes Lyme disease – Bull’s eye rash around bite mark – Sever headaches, backaches, chills, and fatigue- can lead to death • Rickettsia rickettsii - causes Rocky Mountain spotted fever – 3-12 days after infection- high fever and severe headache – 3-5 days after that- rash on extremities, diarrhea, cramps- can lead to death 18.6 Diseases and Antibiotics 18.1Bacterial Studying Viruses and Prokaryotes • Normally harmless bacteria can become destructive. – may colonize new tissues 18.6 Diseases and Antibiotics 18.1Bacterial Studying Viruses and Prokaryotes • Normally harmless bacteria can become destructive. – immune system may be lowered 18.6 Bacterial Diseases and Antibiotics 18.5 Beneficial Roles of Prokaryotes 18.1 Studying Viruses and Prokaryotes Antibiotics - interfere with bacteria cellular functions Antibiotics do not work on viruses • Penicillin - interferes with cell wall synthesis • Tetracycline - interferes with protein synthesis • Sulfa Drugs - are made in laboratories 18.6 Diseases and Antibiotics 18.1Bacterial Studying Viruses and Prokaryotes Bacteria can evolve resistance to antibiotics. • Bacteria are gaining resistance to antibiotics. A bacterium carries genes – overuse for antibiotic resistance on a plasmid. – underuse – misuse A copy of the plasmid is • Antibiotics must be transferred through conjugation. used properly. Resistance is quickly spread through many bacteria. 18.6 Bacterial Diseases and Antibiotics 18.5 Beneficial Roles of Prokaryotes 18.1 Studying Viruses and Prokaryotes Antibiotic Resistance • Population of bacteria exposed to antibiotic Most susceptible bacteria die first a few mutant bacteria are resistant and may continue to grow and multiply results in a resistant population
