Microorganisms Microorganisms Microorganisms Microorganisms Microorganisms

Homework for this weekend – Due Monday 10/16 Research a microbe that has impacted human history (try one that wasn’t mentioned in the video.) Write a paragraph that details its rise and fall, effect of it on human populations, and routes of transmission.

Microorganisms Day 2

Microorganisms as Model systems Model Systems – used by scientists to investigate something new in an organism or biological system they already know a lot about. Early 19th century – Anthrax was used as a model system to understand the cause of disease, transmission, and ways to combat it.

1870’s – Robert Koch – established that the true cause of anthrax was from endospores in the soil. 1880’s – Louis Pasteur – used weakened forms of anthrax to immunize sheep. He used his anthrax research to develop the vaccine for rabies.

Koch and Pasteur Founders of microbiological research Koch used his knowledge to develop postulates that establish whether a microorganism is the causative agent in a disease:

Koch’s Postulates The microorganism must be found in abundance in all animals suffering from the disease, but not in healthy animals. The microorganism must be isolated from a diseased organism and grown in pure culture. The cultured microorganism should cause disease when introduced to a healthy organism. The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Watch this: https://www.youtube.com/watch?v=jG1VNSCsP5Q Does Cholera meet all of the criteria of Koch’s postulates? (answer on L hand side – why or why not)

Defense against bacterial infections Antibiotics – main line of defense 1928 – Alexander Flemming – went on vacation, came back and found a mold growing on his plate of staphylococci. What do you notice???

Zone of Inhibition Zone of inhibition was caused by the penicillin produced by the mold.

Antibiotics Large scale production and use began in the 1940’s (during WWII.) Well known antibiotics: Penecillin Streptomyocin Erythromycin

Antibiotic Resistance Microbes evolve to resist treatment.

MRSA Methicillin Resistant Staphylococcus aureus Common inhabitant of human skin Causes pimples, skin iinfections, wound infections and toxic shock syndrome. According to the CDC, there were more than 80,000 invasive MRSA infections and 11,285 related deaths in 2011.

Watch This: https://www.youtube.com/watch?v=xZbcwi7SfZE Left side – Describe 2 different ways the use of antibiotics has created a “superbug”

Bacteria Much less complex than eukaryotes Cytoplasm – Inside of the cell Contains 70S ribosomes that are used in protein synthesis during translation. Nucleoid – Single loop of genomic DNA in a centralized area Plasmids – small, extra loops of DNA

Flagella – MANY (not all) Pilli – small, hair-like projections often present on the outside of the bacteria. Cell-cell contact Adhesion Flagella – MANY (not all) Move and swim in aquatic environments

Enclosed by a plasma membrane, and a peptidoglycan cell wall. 2 alternating sugars cross linked with small peptides (proteins). Bacteria are classified by the composition of their cell walls: Gram Positive – If they take up and retain stain Gram Negative – If they do not.

Names and Shapes 3 major shapes: Coccus – spherical in shape

2. Bacilli – oval/rod shaped. Look like hot dogs.

Spirilli – spiral shaped

Growing arrangement: The way bacteria arrange themselves while growing helps classify them too. “strepto” – twisted chain “staphylo” – bunch of grapes

Environment Requirements Oxygen Obligate aerobes – Oxygen is absolutely necessary for survival. Facultative aerobes – if they just grow better in the presence of oxygen. Anaerobes – prefer to grow in the absence of oxygen Obligate – absence of oxygen is necessary Facultative – grow better in the absence of oxygen, but not required.

Temperature Psychrophilic – grow best in cold conditions (-15 and 10°C.) Mesophilic – grow best between 15 and 40°C. Thermophilic – grow best between 45 and 80°C. Hyperthermolphilic – extreme thermophiles – thrive at temps. above 80°C.

Thermostable DNA polymerase that allows PCR to operate at high temperatures.