Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Viruses and Prokaryotes 18.1- Studying Viruses and Prokaryotes • A virus is an infectious particle made only of a strand of DNA or RNA surrounded by a protein coat • A bacteria is a one-celled organism that can also cause infections 18.1- Studying Viruses and Prokaryotes • Viruses and bacteria are pathogens. Pathogens are organisms or particles that cause diseases. However, this is where the similarities end. 18.1- Studying Viruses and Prokaryotes • A virus is a problem for scientists because they don’t even believe it is a living organism. • Living things have certain characteristics: • They must show most notably reproducing on their own (VIRUSES CANNOT DO THIS) • In fact, viruses are not anywhere in Linnaean classification. 18.1- Studying Viruses and Prokaryotes • Other structures called viroids are even less like living things. Viroids cause diseases in plants. • Finally, prions are the least likely to be living. These are just proteins that cause other proteins to act incorrectly. 18.1- Studying Viruses and Prokaryotes • Viruses, Viroids, and Prions are all particles that cause infections but are not considered living things because they do not have all the characteristics of living organisms 18.2- Viral Structure and Reproduction • Virus’ structure is very basic. It is made up of genetic material (DNA or RNA) surrounded by a protein shell called a capsid. • Viruses have many different shapes and sizes. Their shape usually tells us something about how it infects a host cell 18.2- Viral Structure and Reproduction • A virus can only reproduce with the help of a host cell. • It has no mechanism to do it by itself: it has no organelles, membranes, no need for oxygen or ATP. • It simply carries its genes to a cell and has that cell copy the genes for the virus 18.2- Viral Structure and Reproduction • Viruses are specific. • Certain viruses can only infect certain cells because of the viral shape. • For example, the bacteriophage is a virus that ONLY infects bacteria. • The bacteriophage has a specific shape that allows it to anchor to bacteria and inject its DNA. The whole bacteriophage does not enter the bacteria 18.2- Viral Structure and Reproduction • Viruses that infect eukaryotes differ from bacteriophages in the way they enter cells. • Generally, the whole virus enters the cell through endocytosis. • Regardless of how viruses get into their host cells, all cause infection. • Only two types of infection a virus causes • LYTIC INFECTION • LYSOGENIC INFECTION 18.2- Viral Structure and Reproduction • A lytic infection causes the host cell to burst releasing new viral offspring into the host’s system and each new virus infects another cell. • This type of infection happens very quickly. 18.2- Viral Structure and Reproduction • A lysogenic infection merges together the host cell’s DNA and the viral DNA. • The viral DNA combines with the host cell DNA to create a prophage. • As the cell gets ready for mitosis, it copies it’s DNA and unknowingly copies the viral DNA as well. • This viral DNA then gets passed on to two more cells. This can go on forever or at anytime the prophage can activate and burst all infected cells. 18.2- Viral Structure and Reproduction 18.4- Bacteria and Archaea • Prokaryotes, which include bacteria and archaea are the most widespread organisms on earth. There are approximately (10^30) prokaryotes on Earth. • These organisms live on about every square inch of Earth including rocks, soil, polar ice caps, deserts, and volcanoes. • Scientists also acknowledge there may be as many as 1 billion different types of bacteria 18.4- Bacteria and Archaea • Prokaryotes are grouped based upon their need for oxygen: • Obligate Anaerobes- can not live in the presence of oxygen and are actually poisoned by it. These organisms live in the harshest enviornments on Earth • Obligate Aerobes- Organisms that must have oxygen to survive • Facultative Aerobes- these types of organisms can live with or without oxygen 18.4- Bacteria and Archaea 18.4- Bacteria and Archaea • Domain Bacteria and Domain Archaea comprise all prokaryotes on Earth. • Domain Bacteria are more diverse and are the ones you encounter of a daily basis. • Domain Archaea are the prokaryotes that live in the harshest of environments. • However, these two groups have some similarities. 18.4- Bacteria and Archaea Structural Comparisons• Under the microscope, Archaea and Bacteria look very similar. • Both are single-celled, prokaryotic, and have cell walls • Most all of Bacteria and Archaea come in generally 3 different shapes 1. Rod-Shaped (Bacilli) 2. Circle-Shaped (Coccus) 3. Spiral-Shaped (Spirilla) 18.4- Bacteria and Archaea • Most all prokaryotes have no membranebound organelles. • Their DNA is free-floating in the cytoplasm. • They also have a structure called a plasmid, that is a small piece of genetic material that can replicate separately from regular chromosome. 18.4- Bacteria and Archaea • Most all prokaryotes move on their own• Most use a flagella, which is a whip-like tail at the end of the organism. While looking the same, the flagella of Bacteria and Archaea are differently structurally. • Some also have pili, which are shorter extensions all around the cell. 18.4- Bacteria and Archaea Molecular Comparisons• Molecular analysis techniques finally allowed scientists to see the many differences between Bacteria and Archaea. • Actually, most scientists believe archaea are more closely related to Eukaryotes rather than Bacteria. • Archaea contain lipids in their cell membranes and walls 18.4- Bacteria and Archaea Molecular Comparisons (cont.) • Bacteria, however, contain a substance called peptidoglycan, a polymer only found in Bacteria. • The amount of peptidoglycan in the cell walls is an important characteristic of Bacteria. • This polymer is detected by a process called Gram-Staining. 18.4- Bacteria and Archaea Gram-Staining• Bacteria are placed in 2 groups based on this test: Gram tests are used to detect the amount of peptidoglycon in a cell wall. • Gram-Negative: Stains red and means there is only a thin layer of peptidoglycan • Gram-Positive: Stains purple and means there is a very thick layer of peptidoglycan 18.4- Bacteria and Archaea 18.4- Bacteria and Archaea • Prokaryotes have found numerous ways to survive and pass on genes: They are very quick at adapting to a new environment. • Most prokaryotes reproduce asexually and binary fission the chromosome copies itself and the cell doubles in size and then splits in half. • Prokaryotes can sexually reproduce through conjugation the pili of each prokaryote connect and this connection is used to exchange genes 18.4- Bacteria and Archaea • Prokaryotes can also survive unfavorable conditions by certain an endospore. • This is a specialized cell with a thick wall to protect the prokaryotes from harsh conditions 18.5- Beneficial Roles of Prokaryotes • Prokaryotes, such as bacteria, are a key part of animal digestion of foods. • If we didn’t have these bacteria, it would take up to 7 days to digest food. • They (bacteria) also make vitamins and other compounds and keep other microbes away. • The bacteria gets a place to live and food. 18.5- Beneficial Roles of Prokaryotes • Prokaryotes benefit us in other ways too. • Many of the foods we enjoy are fermented by bacteria. • Yogurt, cheese, pickles, soy, sauerkraut, and vinegar depending of prokaryotes to be made. 18.5- Beneficial Roles of Prokaryotes • Prokaryotes also help balance the ecosystem: • Some, like cyanobacteria, produce oxygen while others recycle carbon and other gases • Other bacteria fix nitrogen so plants can use it: Plants need nitrogen, but can’t use it in it’s atmosphere gas form. • Bacteria takes atmospheric nitrogen and converts it to ammonia for plants to use. • Soybeans would not survive without this benefit 18.5- Beneficial Roles and Prokaryotes • Some prokaryotes can even be used to clean the environment. • So bacteria digests oil, helping in oil spills. • Bacteria also breaks down decaying organic matter. 18.6- Bacterial Diseases and Antibiotics • Bacteria can cause sickness for a host organism in two ways: 1.Invading Tissues 2.Releasing Toxins • EXAMPLES: 1. Tuberculosis- invading lung tissues and kill white bloods cells 2. Botulism (Food Poisoning)- caused by toxins released by a bacteria called clostyidium botulinum. 18.6- Bacterial Diseases and Antibiotics Antibiotics• These are medications that fight bacterial infection. • THEY DO NOT FIGHT VIRAL INFECTIONS LIKE COLDS AND FLUS!!! 18.6- Beneficial Diseases and Antibiotics • Antibiotics work by not allowing bacteria to create cell walls so they cannot reproduce. • Some organisms, such as some fungus, create antibiotics normally. • Antibiotics, however, should not be the 1st line of defense against infections, prevention should be…………WASH YOUR HANDS!! 18.6- Bacterial Diseases and Antibiotics • Finally, when given an antibiotic, do not abuse it, but instead, follow the directions. • When mis-used, bacteria can build-up a resistance to antibiotics. • Mis-using involves using too much or not taking all of antibiotics of a given course of treatment. • Both of these cases create “superbugs” that are bacteria that can resist almost any antibiotic.