Microbiology lecture notes from 8-31 to 9-4 classes

Microbiology, August 31 – September 2 and 4, 2009 Major categories of microbes NOTES
I. Definition of Microbes: An organism that’s small enough that we have to use a microscope to see it. Can’t see with the naked eye.
II. Eukaryotes: cells have nuclei
Nucleus: Membrane bag surrounds DNA
Most kinds of eukaryotes on earth are microscopic. Most are single-celled.
All eukaryotes very genetically similar to each other. Look at figure 1.27b in the text book for chart from class about archaea, bacteria, and Eukarya
Vaccines: make your body make a specific immune response against a particular kind of pathogen(disease-causing organism).
Antibiotics: Drug that you ingest (not made by you) that kills bacteria in general
Koch organism can’t change
Pasteur thinks can change/adapt.
Robson finds this important
III. Prokaryotes: Cells without membrane bag surrounding DNA (no Nucleus)
a. Archaea:
• prokaryotes
• no membrane bound nucleus.
• Called archaea is because thought to have not changed much for billions of years. (they have chemical characteristics that make us think they may have been unchanged for very long period of time.)
• have more in common with eukarya cells than they do bacteria.
• No nucleus, like bacteria, but otherwise more similar to eukaryotic cells than to bacteria.
i. EX. Cell membrane (chemistry of membrane is more similar to eukaryotic rather than bacterial cell membranes), RNA polymerase like that of eukaryotes(similar to eukarya cells) – makes polymers of RNA enzyme that does transcription. DNA transcriped into RNA if doesn’t happen proteins cant be made that form cells. death if doesn’t occur.
ii. Extremophiles
Most archaea that we know about live in very extreme environments:
• Geysers, ocean vents, other water with very high (>100°C) temputures
• Dead Sea
• Lots of others (cold, high pressure, low pHs.)
b. Bacteria:
• Prokarotyes
• no membrane bound nucleus
• more closely related to each other than they are to archaea or eukarya.
• Huge genetic diversity of bactiera.
• Have distincitive cell wall and cell membrane structures
• Distinct RNA polymerase
i. Gram positive
• Minority of bacteria on earth, but important clinically
1. Plasma Membrane
2. Peptidoglycan( protein and carbohydrate) (has ~ 30+ layers that is linked and cross linked) (Cross linked with lipoteichoic acid)cell wall with lipoteichoic acid (LTA) (fatty acid) (LTA is unique to Gram positive bacteria.)
Gram staining techniques works because:
• Crystal violet
• Iodine
Crystal violet and iodine clumps in cell staining purple.
• Decolorize w/ ethanol (lots of layers causes cell to stay purple hard for the alcohol to clear all purple) (if thin cell wall color leaves
• Pink stain ( then allows you to see if not purple then pink that shows thin cell wall gram negative cell.
9-4-09 Notes
Antibiotics: attack target in bacterial cells necessary for cell survival that our cells don’t have
See archaea question reasoning like on first exam.
RNA polymerase different therefore find one for archeae and kill your own RNA polymerase as well.
Don’t use “I feel that…” or “I believe that…”
ii. Gram negative
1. Plasma membrane
2. Peptidoglycan cell wall with no LTA ( have fewer (just a few ~ 5 peptidoglycan layers) in cell wall layers))
3. Periplasmic space
4. Outer membrane containing lipopolysaccharide (LPS) (outside) phospholipids (inside leaflet)
Other points on LPS and LTA:
• Inflammatory response – reacts very violently against non-eukaryotic chemical components
• So too much LP Sor LTA in blood  violent inflammation, often death
- Lipid A, inside part of LPS,  most violent response
iii. Acid-fast
1. Plasma Membrane
2. Cell wall containing LTA
3. Outer membrane (more like an additional wall) containing mycolic acid
- Mycolic acids are really really dense waxy like molecules.
- Very resistant to drying out  can survive for a long time in dry environments.
- Hydrophobic membrane
- Lots of soil bacteria are acid fast bacteria
- Gram staining technique doesn’t work on acid-fast bacteria. Because the Mycolic acid layer prevents the ingredients from penetrating bacteria cell envelope
Consequences of having a rigid cell wall made out of peptidoglycan
Clearly defined shapes
Round/spherical: cocci
Tubes/cylindrical: bacilli
Spirochetes (spiral/corkscrew)
iv. Mycoplasms
No cell wall
Plasma membrane
Ex. Chlamydia
1. Plasma membrane
2. Maybe another membrane ( not necessarily the same as gram-negative’ outer membrane, though)

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