BIOLOGY NOTES CH 20<br />BACTERIA AND VIRUSES<br />
I. BACTERIA<br />Found everywhere on earth: mountains, hot springs, oceans, inside human body<br />Bacteria are prokaryotes – a cell with no nucleus<br />Bacterial structure:<br /> 1. single, circular strand of DNA<br /> 2. have cytoplasm<br /> 3. have cell membrane<br /> 4. have cell wall<br />
Classification – two kingdoms of bacteria:<br /> 1. Archaebacteria – ancient bacteria<br /> 2. Eubacteria– true bacteria<br />Bacterial growth and reproduction<br /> 1. binary fission – a type of asexual reproduction<br /> where the bacteria splits in two.<br /> 2. conjugation – a type of sexual reproduction where <br /> two bacteria come together and exchange DNA.<br /> 3. some bacteria can form endospores to survive<br /> harsh conditions<br />
Bacteria and disease<br /> 1. bacteria cause many diseases such as diphtheria, syphilis, cholera, Lyme disease, tuberculosis.<br /> 2. one of the most common bacteria is streptococcuspyrogenes which causes strep throat.<br /> 3. Salmonella – the bacteria that causes food poisoning in humans.<br /> 4. E. coli – bacteria that live in intestines, and are the source of many food poisoning outbreaks.<br /> 5. antibiotics – drugs that are used to treat bacterial infections.<br />
Bacteria in our world<br /> 1. decomposers – bacteria that break down dead organisms<br /> 2. bacteria in the human intestines help in digestion and make vitamins<br /> 3. nitrogen-fixing bacteria help fertilize soil<br /> 4. bacteria are used in processing foods such as cheese, sour cream, yogurt, sauerkraut, vinegar<br /> 5. bacteria also assist in sewage treatment and copper mining<br /> 6. The simplest way to control bacteria is through sterilization with the use of heat or chemicals.<br />
II. VIRUSES<br />A virus is a nonliving particle that contains DNA or RNA and cannot live outside of a living cell.<br />A virus reproduces by taking over a living host cell. The virus injects its DNA into the host cell and causes the cell to replicate more virus particles.<br />The shape and composition of the virus determines which cells it will infect.<br /> Ex: HIV infects only white blood cells called T-cells.<br />
Viral infections<br /> 1. lytic infections – the virus takes over the host cell and destroys it by causing the cell to burst.<br /> 2. lysogenic infection – the virus converts the host cell into a factory for making more of the virus.<br />
Viruses and Disease<br /> 1. retrovirus – contain RNA instead of DNA.<br /> Ex: polio virus, HIV<br /> 2. Adenovirus – virus that causes colds, spread through the air.<br /> 3. Influenza – virus that causes flu; many different strains of this virus.<br /> 4. Herpes simplex virus – virus that causes herpes infections.<br /> 5. Bacteriophage – viruses that infect bacteria cells.<br />
Vaccines – medicines used to prevent viral infections.<br /> 1. Edward Jenner – scientist who developed the first vaccine. He noticed that milkmaids who contracted the cowpox virus were immune to the smallpox virus. He used the cowpox virus to make a vaccine for smallpox.<br /> 2. The smallpox virus was completely eradicated (wiped out) through the worldwide use of vaccinations.<br />
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