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Chapter 19 Bacteria and Viruses Prokaryotes: single-celled organisms that lack a nucleus Eubacteria walls contain peptidoglycan (a carbohydrate found in cell walls of eubacteria) Archaebacteria: includes methanogens, halophiles and thermophiles Lack peptidoglycan DNA sequences of key archaebacteria genes are more like eukaryotes than eubacteria. Classifying prokaryotes Done by shape Reaction to Gram stain (due to nature of cell wall) Arrangement Diplo = 2 Staphylo = cluster Strepto = chain Movement Some non-motile Some undulate like a snake Others use flagella or secretions to move Identifying Prokaryotes 1. Shapes a. Bacilli (rod shaped) b. Cocci (spherical) c. Spirilla (spiral) Reaction to Gram stain is due to nature of cell walls a. Gram-positive (cell walls contain w/peptidoglycan) – appear purple b. Gram-negative (cell walls lack peptidoglycan – appear red Obtaining Energy 1. Autotrophs a. Photoautotrophs: obtain energy from photosynthesis b. Chemoautotrophs: obtain energy from inorganic molecules 2. Heterotrophs a. Can cause food poisoning b. Photoheterotrophs: photosynthetic, but also need organic compounds for nutrition Releasing Energy 1. Obligate aerobes: require oxygen 2. Obligate anaerobes: cannot live in presence of oxygen 3. Facultative anaerobes: do not need oxygen, but can live in the presence of it Growth and Reproduction 1. Binary fission: cell divides, asexual 2. Conjugation: transfer of genetic information from one cell to another, sexual 3. In unfavorable conditions, many bacteria can form endospores – can remain dormant for months or years Exponential Growth Curve Uses of Bacteria • Food – cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut • Industry – cleaning up oil spills, mining minerals, synthesizing drugs (such as insulin and human growth hormone) • Assist in digestion – symbiotic relationship in our digestive tract. Bacteria in Nature Decomposers 1. Help recycle nutrients – break down dead organisms 2. Used in sewage treatment Bacteria are important as decomposers Recycles important nutrients. Bacteria in the Nitrogen Cycle Nitrification – “fixing” N2 1. Nitrogen fixation: converting nitrogen gas into nitrate or ammonia 2. Example: Rhizoacter which grow on roots of soybeans and other legumes. Reduces need for application of fertilizer. Bacteria also release nitrogen back into the environment. Called (denitrification) Controlling Bacteria 1. Sterilization: destroy bacteria by subjecting them to great heat or chemicals a. Boiling, frying, steaming can all kill bacteria b. Disinfectant chemical solutions can be used in homes and hospitals 2. Refrigeration – bacteria grow slowly at low temperatures Bacteria and Disease 1. Pathogen: disease-causing agents 2. 2 ways bacteria cause disease a. Break down tissues for food b. Release toxins 3. Many can be prevented with vaccines, can be treated with antibiotics Cross-linkages holding cell wall and cell membrane together do not form properly. Antibiotics First discovered accidentally, Alexander Fleming Work by interfering with cell wall production so bacterial can’t reproduce. Cross linkages cannot form so cell wall develops holes and bacterium ruptures. Some bacteria have antibiotic properties; ex: Streptomyces Only bacteria … not viruses … can be killed with Bacterium elongates antibiotic treatment. preparing to divide. Then ruptures when cell wall fails. PENICILLIN KILLING E. coli Bacteria in Biotechnology Transformation – Bacterial cells pick up DNA from other sources (including dead bacteria) and incorporate it into their own genome. Increases genetic variety and opportunities for resistance. Transduction – Process of using a virus to transfer DNA from one bacterial cell to another. PCR – insert gene into bacterial plasmid for rapid replication of sample Bacterial Diseases: Necrotizing fasciitis • Caused by a mutated Streptococcus • Reproduces rapidly • Tissue must be removed to stop spread • Patient is put into a pressure chamber (forcing O2 into tissue to assist healing) to reduce the spread. Anthrax Direct contact Many different strains Found in lower vertebrates – goats, sheep, cattle Three types Cutaneous – skin – death rare if treated Inhalation – Cold-like – fatal Gastrointestinal – 25-60% Bubonic Plague or Black Death Caused by pathogenic bacteria spread from China on trade ships (13 Symptoms include swollen lymph nodes (buboes, hence the name), high fever, and delirium. 90% death rate Killed 1/3 of the population of Europe within a 5 year period 1347-1352 (including Shakespeare’s siblings) Lyme Disease • Transmitted by Deer tick. Lyme Disease Symptoms Botulism & E. Coli • Botulism • • • Muscle-paralyzing disease. Food-borne Anaerobic • E. Coli • • • • 1,000 of strains Undercooked meat Sewage water Lives in intestines without causing a problem VIRUSES Non-living particles consisting of nucleic acid (RNA or DNA) surrounded by a protein coat No organelles, no nucleus, etc. Parasitic Rely on a host for replication Bacteriophage = virus that infects bacteria III. Viruses A. Viruses: particles of nucleic acid and protein 1. Nucleic acid = DNA or RNA that contains instructions for making new copies of the virus 2. Capsid: outer protein coat Bacteriophage: virus that infect bacteria Mechanism: Fibers attach Contractile sheath squeezes down Nucleic acid (DNA or RNA) in head (capsid) is injected into bacterial host Head/Capsid Contractile Sheath Tail Tail Fibers Base Plate In a viral infection, do people get sick from the protein coat or the DNA core? Viral Infection Cycles 2 types of viral infections a. Lytic infection: virus enters cell, make copies of itself and causes the cell to burst b. Lysogenic infection: virus embeds its DNA into DNA of host and is replicated with host cell’s DNA Virus Reproduction The Lysogenic Cycle Virus Reproduction The Lytic Cycle Viral Diseases 1. Common human diseases caused by a virus: common cold (rhinovirus), chickenpox, measles, mumps, polio, rabies, hepatitis Many viruses can be prevented through the use of vaccines (polio, measles, influenza) 2. Oncogenic viruses cause cancer 3. Retroviruses contain RNA 4. Prions contain no DNA or RNA, only protein Human Viral Diseases: Ebola Found in Primates Animal-Borne Virus RNA virus Incubation – 2-21 days Fever, headache, joint & muscle pain – rash red eyes – Extensive bleeding from all orifices. SARS Severe Acute Respiratory Syndrome Hot Zone- China, Toronto Symptoms – Flu like- fever, headache, dry cough Transmission- Person to person contact, respiratory secretion Military action has been taken to keep virus controlled. Small Pox Humans are the natural host. Spread by face to face contact. – Also body fluids. Most Contagious during Early Rash continues till the last scab falls off. HIV Human Immune Deficiency Virus Fastest Spreading disease in Africa Effects white blood cells. T-Cells AIDS diagnosed when T-cell count falls below 200 West Nile Virus Host – Birds Spread through mosquitoes Fever, headache, and body aches, occasionally with skin rash and swollen lymph nodes. Rare encephalitis 1% of mosquitos carry the virus, 1% of those infected will die. Viroids and prions Viroids: tiny, naked circular RNA that infect plants; do not code for proteins, but use cellular enzymes to reproduce; stunt plant growth Prions: “infectious proteins”; “mad cow disease”; trigger chain reaction conversions; a transmissible protein