Bacteria and Viruses Chapter 19 anthrax Strep throat
Bacteria and Viruses Chapter 19
anthrax Strep throat
19 -1 BACTERIA • BACTERIA ARE CLASSIFIED AS PROKARYOTES – UNICELLULAR ORGANISMS THAT LACK A NUCLEUS • CLASSIFYING PROKARYOTES – EUBACTERIA – LARGER OF THE TWO KINGDOMS • LIVE IN FRESH WATER, SALT WATER, LAND, AND ON AND IN HUMAN BODY.
Prokaryotes • Traditionally all prokaryotes were classified as Monerans • Also known as bacteria (p. ) or bacterium (s. ) • Presently, prokaryotes are divided into two kingdoms Archaebacteria & Eubacteria
1. K. Eubacteria • Larger of the two kingdoms • Live almost everywhere • Vital for life functions and industry • Both helpful and harmful (E. coli!)
2. K. Archaebacteria • Believed to be earliest organisms to inhabit the Earth • All live in harsh environments • DIFFER FROM EUBACTERIA BY: – NO PEPTIDOGLYCAN – DIFFERENT MEMBRANE LIPIDS – DNA more like eukaryotes’ DNA • 3 separate phyla…
1. Methane-producing bacteria (methanogens) • Intestinal tracts of animals • Bottoms of swamps • Used for sewage treatment
2. Salt-loving bacteria (Halophiles) • Thrive in high salinity waters where no other life can exist. • Great Salt Lake • Dead Sea
3. Hot-acidic loving (thermoacidophiles) • Thrive at temperatures as great as 180ºF and p. Hs as low as 2. • Natural springs. • Yellowstone National Park
Facts about bacteria: • Found everywhere • Very small. Much smaller than any cell in our body. • No membrane-bound structures or nucleus. (prokaryotes) • Usually surrounded by a cell wall and a capsule for additional protection.
General structure:
IDENTIFYING PROKARYOTES • IDENTIFIED BY SHAPE, CELL WALLS, MOVEMENT FLAGELLA, WAY THEY GET ENERGY – SHAPES: – BACILLI (RODS), COCCI (SPHERES), SPIRILLA (SPIRAL)
Classification according to shape. 1. Coccus (spherical) Ø Can be single cells, pairs, or chains Ø Example: Strep throat
2. Bacillus (rod) • Single cells • Pairs • Chains • Example: anthrax
3. Spirillum(spiral) v. Only exist as single cells Example: cholera, syphilis
Shapes:
4 Ways to Classify Bacteria 1. shape 2. Chemical nature of cell walls (Gram + or gram -) 3. How they move 4. How they obtain energy
Gram-positive bacteria • Two kinds of cell walls in Eubactiera • Gram-positive bacteria have cell walls that are dyed a violet stain. • Can be harmed by antibiotics like penicillin • example: streptococcus
Gram-negative bacteria • More difficult to penetrate cell wall. • Appear pink/red in Gram stain • Usually more difficult to treat with antibiotics • Example: E-coli
Movement • Usually move through flagella or gliding along a surface.
Metabolic Needs • Aerobic • The most common type • Cannot live without oxygen • Anaerobic • Cannot live in the presence of oxygen • Gets energy through fermentation (CO 2)
Heterotrophic bacteria • Saprobes • Parasites • Feed off the • Live on or in remains of other living dead plants and organisms. animals. Seldom Often cause disease
2 types of heterotrophic bacteria • Chemoheterotrophs – take in organic molecules for energy and carbon (like humans!) – Largest group of bacteria! • Photoheterotrophs – use sunlight for energy, but also need to take in organic compounds
Autotrophic bacteria • Photoautotroph • Chemoautotroph • Use sunlight to convert carbon dioxide into energy • In lakes/streams/ oceans • Ex. cyanobacteria • Use inorganic chemical compounds to convert carbon dioxide into energy.
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 (E. coli)
E. 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 (such as anthrax)
Genetic material • Nucleoid= a single circular chromosome containing the DNA and RNA. • Endospore = tough protective coat that covers and protects the nuclear material.
Reproduction • All reproduce asexually • Usually through binary fission • Under certain conditions, bacteria can reproduce very quickly – A small colony can double in 20 minutes. – animation
Binary fission • The most common type of asexual reproduction. • A single cell splits to form two daughter cells
Exchange of DNA Conjugation = genes move from one cell to another
Endospores • A thick covering around the DNA that allows the bacterium to remain dormant for long periods of time. If necessary, many years.
Importance of Bacteria • Without bacteria, we would die! • Bacteria produce energy, decompose dead matter into nutrients, convert nitrogen for plants, and produce vitamins in our intestines
Helpful bacteria • • • Decompose food wastes Produce antibodies Genetic engineering – bacteria can produce heat-stable enzymes for medicines • Decomposition of dead plants and animals • Industry & agriculture – cleaning oil spills • Break down sewage into water, carbon dioxide, nitrogen
Bacteria on Plant roots • Can be helpful in ‘fixing’ nitrogen for plant use. • Rhizobium nodules on roots of soybeans convert nitrogen into ammonia
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
• • • Are they living or non-living? Contain genetic material Lack organelles Cannot reproduce unless inside a host cell. The word virus comes from the Greek word for POISON Cause many diseases.
Section 19. 2 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
How big is a virus? • Much smaller than bacterial cells. • Scientists have only recently, last 60 years, learned anything about viruses • Classified according to the types of cells they attack.
Virus structure: • A center core of DNA or RNA surrounded by a protein coat called a capsid.
Viral Body Plans • Genetic material is DNA or RNA • Coat is protein Helical virus Polyhedral virus Complex virus (bacteriophage)
DNA and RNA Review DNA – deoxyribonucleic acid chemical compound (containing hydrogen, oxygen, nitrogen, carbon, and phosphorus) with instructions for coding proteins that determines your genetic makeup RNA – ribonucleic acid - nucleic acid that contains the sugar ribose
Viral Infections A virus binds to proteins on a cell and enters the cell • 1. Infect cells and replicate inside host cell • 2. Bacteriophage: viruses that infect bacteria
2 types of viral infections a. Lytic infection: virus enters cell, makes 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
2 main types of viral reproduction: • LYTIC CYCLE 1. Injects its nucleic acid (DNA or RNA) into the cell to take over cellular activities. • LYSOGENIC CYCLE 1. Coexists with the cell without destroying the host cell
Lytic cycle
Lysogenic cycle
The Prophage • Prophage = viral DNA that is inserted into a cell • The prophage can have the cell make copies of the virus right away or may wait several generations (a latent infection) and then begins making copies at a later time
Viruses and Disease 1. 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
• Direct the production of proteins by the host cell. • RETROVIRUS = A special type of virus that can make DNA which will produce new RNA, which, in turn, makes proteins that produce new viruses. • Ex.
Bacteria and Disease 1. Pathogen: disease-causing agents 2. 2 ways bacteria cause disease a. Break down tissues for food b. Release toxins to interfere with normal cellular activity 3. Many can be prevented with vaccines, can be treated with antibiotics
Common bacterial diseases: • Lyme disease • Tetanus • Strep throat • Tuberculosis • E. coli poisoning
Controlling bacterial disease. • ANTIBIOTICS – compounds that block the growth and reproduction of bacteria • 1928. Discovery of penicillin by Sir Alexander Fleming
Common methods of bacterial infection. • Food & water (E. coli) • Coughing & sneezing • Sexually transmitted. • Carried by insects
Controlling Bacterial Growth • Sterilization by heat – most bacteria are killed by high heat! • Disinfectants – chemical solutions that kill pathogenic bacteria • Food storage – boiling/frying/steaming kills, bacteria take longer to multiply in fridge (cooler temperatures)
How do we prevent viral diseases? • Cannot be treated with ordinary antibiotics • Prevention is best way to protect against viral diseases: • A vaccine is a weakened form of a virus that is used to stimulate the immune system to produce antiviral substances.
Edward Jenner (17491823) • British physician • Developed the first vaccine in 1798 for the viral disease smallpox. • Considered the “Father of Immunology”
Common viral diseases: • • AIDS Measles Chickenpox Smallpox Influenza The common cold West Nile Polio
• Viral disease that is believed to have originated in Egypt at least 2000 years ago. • Characterized by pox lesions and boils. • Spread to the Americas by Spanish conquistadors. • Jenner’s vaccine was developed after observing a bovine disease: “cowpox”
Eradication of smallpox: • In 1967 the World Health Organization launched a global effort to eradicate smallpox. • 1978 : Last known case of smallpox. • 1980 : W. H. O. declares the world free of smallpox. • Is there any smallpox virus left?
Smallpox upmc-biosecurity. org
Viroids and Prions • Viroid • Small disease causing particle. • Affect plants • Prion • Small disease causing particle. • Affects animals. • example:
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