Pathogen – any organism that causes disease. Exs.) virus, bacteria, protozoan. Some Examples of VIRUS Illnesses : Polio, Chicken Pox, Shingles, Hepatitis, Flu, AIDS, Common Cold.
Are Viruses Living or Non-Living?? : - Scientists debate this because viruses do not require food, oxygen, water……yet they can reproduce (note – they only reproduce inside a living host cell).
Bacteriophage – viruses that only attack bacteria. Ex.) T-4 virus T-4 Virus – a famous virus in scientific circles. • It only attacks bacteria – it is safe to humans. • It is easy to grow in petri dishes and cost is minimal. • Because of the above factors, T-4 makes a good research specimen. • T-4 is famous because it has been widely studied. Most of our early knowledge about viruses came from studying T-4.
Virus Structure – made up of a coat and a core. • Coat is outer protective covering made of protein. • Core is made up of the genetic material DNA or RNA.
Lytic Cycle – reproductive cycle for regular viruses. See figure 25-5 on page 492 in book.
Stages of Lytic Cycle: • Attachment – virus latches onto cell. • Entry – virus injects its DNA into cell. • Replication – virus DNA takes over the cell’s machinery and directs it to make virus parts. • Assembly – virus parts get put together. • Release – newly made viruses break out of cell and can now go and attack more cells. (note – the cell dies in the process).
Latent Viruses – infect you now, but do not make you sick for a period of time. Exs.) HIV, Herpes, Shingles.
3 Major Ways That Germs are Transmitted • Airborne Transmission – enter the body with the air breathed in. Exs.) smallpox, chicken pox, polio, measles, flu, common cold. Prevention – vaccines, avoid sick people, cover your mouth when sneezing and coughing.
2. Food and Water Transmission – most effect stomach and intestines. Gets into food/water from intestinal wastes. Exs.) hepatitis A, salmonella, botulism, E. coli. Prevention – good hygiene, wash hands, check canned food for damage, keep foods refrigerated/frozen, cook meats/eggs well done, have drinking water tested.
3. Contact Transmission– shaking hands, kissing, touching, sex, sharing cups, towels, etc. • Watch wounds of all kinds Prevention – practice safe sex, good hygiene, disinfect wounds.
Archaebacteria – rare – only found in a few places on earth. Exs.) in the boiling water of hot springs, in very salty waters where no other bacteria thrive, at the ocean vents where water is superheated.
Eubacteria – “true” bacteria – common, everyday bacteria. They are found just about everywhere, including in and on our bodies.
Prokaryotic Cells (Prokaryotes) = Bacteria • Thought to be the oldest cells on earth. • Do not have a true nucleus that houses the DNA. Bacterial DNA just floats unprotected inside the cell. • Very simple structure. They do not have any parts that are seen in more complex cells. • ***BACTERIA ARE THE ONLY CELLS ON EARTH THAT ARE PROKARYOTIC.***
Bacterial Shapes – Used for Identification • 1. Coccus (Cocci) • 2. Bacillus (Bacilli) • 3. Spirillum (Spirilla)
Coccus (Cocci) – round, sphere shaped. • Diplococcus – 2 joined in a pair. • Staphylococcus – clumps/clusters of cells…many cause “staph” infection. • Streptococcus – strips/chains of cells…. cause “strep” throat. • Tetrad – 4 cells arranged in a square.
2. Bacillus (Bacilli) – elongated rod shapes • Diplobacillus – 2 joined. • Streptobacillus – strips/chains.
3. Spirillum (Spirilla) – bent rods like a boomerang, or corkscrew shaped. Spirilla only occur in the single form, they do not join together in any way. See top of page 470 in book.
Nutrition in Bacteria Autotrophs – “Cyanobacteria” – SOME bacteria are photosynthetic and can make there own food. Heterotrophs – MOST bacteria rely on other organisms to make food for them. 2 types: • Saprophytes – get food from dead organisms….many of these bacteria compete with us for our food and spoil it. • Parasites – get food from living cells. These are the pathogens that infect us and make us sick.
Respiration in Bacteria Obligate Aerobes – require oxygen and cannot live without it…….most bacteria. Obligate Anaerobes – do not grow in the presence of oxygen. They use other gases such as methane or they conduct fermentation. Facultative Bacteria – live with or without oxygen. They grow faster with oxygen.
Factors That Affect the Growth of Bacteria • Temperature : • 79 – 100 degrees Fahrenheit – optimum growth range for many bacteria. • Refrigeration/cooking inhibits bacteria. • Body uses fever as defense mechanism to kill off temperature sensitive bacteria. 2. Moisture: • Bacteria are 90% water and dryness makes them inactive • We dry many foods to preserve them such as pasta, dried fruit and beans, cereal, rice, potatoes.
Factors That Affect the Growth of Bacteria 3. Radiation – sunlight and ultraviolet light kills bacteria by mutating their DNA. • We put ultraviolet lights in operating rooms to kill germs. 4. Chemicals – many kill bacteria. Exs.) chlorine, vinegar (acetic acid) to pickle foods, sugar, salt, artificial preservatives.
Bacteria Reproduction and Survival Binary Fission = simple cell division….the bacterium splits in 2. • This is how bacteria REPRODUCE when growth conditions are good.
Bacteria Reproduction and Survival Spore Formation – Bacterium makes a tough protein wrapper to protect only its DNA when conditions are not good. This is called a SPORE. • This is how bacteria SURVIVE when conditions are not suited for growth. Spores can survive quite harsh conditions.