Transcript viruses
1 Pathogens Any disease causing agent is called a pathogen. How Big Is It? 1 nanometer (nm) = one billionth of a meter 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 2 Types of Pathogens 1. Virus - An infectious particle made only of a strand of DNA or RNA surrounded by a protein coat, NON-LIVING. 2. Bacteria - Prokaryotic unicellular microorganisms, LIVING. Lactobacilli: rod-shaped Enterococci: spherical Spirochaeta: spiral 3 II. Viruses A. Traits of a Virus 1. Non-living Pathogen- there are no cell parts, no cell, no growth or response at all. - Do not belong to any kingdom. 2. Made up of 2 Parts a. Capsid- Protein coat which surrounds…. b. Genetic material (DNA or RNA) 4 3. Two regions of a virus a. Head – contains the DNA or RNA b. Tail – allows it to attach onto a host. 4. Ways to group or classify a virus a. Shape of the protein coat surrounding the head b. What the virus infects c. Size of the virus 5 •The make-up of a viral capsid give viruses a variety of shapes. •In some, the protein coat (capsid) is surrounded by a lipid envelope. -Protective outer coat with spiky structures of proteins and sugars may stick out. •Structure and shape are important in how a virus infects something •Each virus can only infect certain hosts. •Recognizes host by fitting surface proteins onto receptor molecules on a host- like a lock and key Viruses that infect bacteria are called Bacteriophages. They infect the bacterial cell by piercing it and injecting DNA. capsid DNA tail sheath tail fiber colored SEM; magnifications: large photo 25,000; inset 38,000x 7 Viruses and Disease All viruses live as parasites. Spread from one organism to another by air, insects, water, and food. Viruses cause 2 types of infections. 1. Lytic Infection Lytic – virus infects cell and causes the cell host to burst open releasing more viruses. 8 Viruses cause two types of infections. A lytic infection causes the host cell to burst. host bacterium 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. 2. Lysogenic Infection – does no immediate harm to the host. - some viruses stay hidden for a long time before they are noticed. - There are no symptoms until something triggers it to be active, and the virus just stays in the body. Example: cold sores – Herpes simplex I The prophage may leave the host’s DNA and enter the lytic cycle. Many cell divisions produce a colony of bacteria infected with prophage. The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. 10 6. The human defense is the WHITE BLOOD CELL a. Some surround and destroy the virus b. Others make ANTIBODIES • Chemicals made by specialized white blood cells • Help stop viruses and harmful bacterium • Foreign invaders may be destroyed directly by antibodies OR may be held captive until white blood cells can surround and destroy it 11 Vaccines are made from weakened pathogens. A vaccine stimulates the body’s own immune response. Vaccines are the only way to control the spread of viral disease. -Vaccines prepare the immune system for a future attack. 12 Differences between an antiseptic and disinfectant Antiseptic – (against microorganisms) is used to destroy microorganisms living on live or living surfaces. Examples: Bactine, soap, listerine Disinfectant – destroy microorganisms living on non-living surfaces. Prokaryotes Prokaryotic cell- Lack nucleus and organelles. Has DNA in the form of a circle separate from the main chromosome – Known as a Plasmid. Members from the Domains Bacteria and Archaea comprise all of Earth’s prokaryotes. Grouped based on their need for Oxygen 1. Obligate anaerobe – Do not need oxygen to survive. Poisoned by Oxygen 2. Obligate aerobe- Need Oxygen 3. Facultative aerobe- Can survive with or without Oxygen 14 Bacteria and Archaea BACTERIA •3 common shapes •Found eveywhere •Peptidoglycan in cell wall BOTH •Prokaryotes •Unicellular •Very small •Cell wall (Chemically Dif.) •Plasma membrane •Plasmids (DNA) •May have Flagella (Structurally Different) •Pili ARCHAEA • Many shapes •Extreme environments •No peptidoglycan in cell wall 15 I. Eubacteria (Prokaryotes) A. Traits of bacteria 1. Unicellular and can be found in pairs, colonies or in chains. (Arrangement) 2. Prokaryotic cells – lack a nucleus, but have DNA 3. Microscopic, but larger than viruses. - 300 could be in a line on the tip of your pencil, but they’re still larger than viruses 4. Found almost everywhere 5. Classified by shape a. cocci – round b. bacilli - rod c. spirillia - spiral 16 3 Common shapes or types of bacteria Lactobacilli: rodshaped Enterococci: spherical Spirochaeta: spiral 17 Eubacteria (Prokaryotes) 6. A capsule protects the bacteria from drying out and helps it to stick to things. (Slime Layer) 7. Some have whip-like tails - FLAGELLA – to move. 8. Reproduce through binary fission– asexual reproduction 9. Requirements of life = Food, certain temperature, moisture, most like darkness and most need oxygen. 10. When growing conditions are not right, certain bacteria form endospores to protect themselves until conditions become pili favorable again. plasma membrance chromosome flagellum cell wall plasmid This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences. 18 Prokaryotes provide nutrients to humans and other animals. Prokaryotes live in digestive systems of animals. make vitamins break down food Used to make antibiotics – Chemicals that kill or slow bacteria growth. - Prevents cell wall formation Antibiotics Do not work on viruses! Why don’t antibiotics affect our bodies’ own cells? 19 Bacteria can evolve resistance to antibiotics Bacteria are gaining resistance to antibiotics. overuse underuse 1. A bacterium carries genes for antibiotic resistance on a plasmid. 2. A copy of the plasmid is transferred through conjugation. misuse Antibiotics must be used properly. 3. Resistance is quickly spread through many bacteria. conjugation bridge 20