9-2,4-09 Notes

Major Categories of Microbes

I. Microbes: Any organism so small it can’t be seen without a microscope
II. Eukaryotes: Cells that have nuclei
a. Nucleus: Membrane that surrounds DNA
b. Majority are Microbes: Single-celled
c. All eukaryotes are very genetically similar to each other
-Vaccines: They make your body make specific immune responses against a particular kind of pathogen (any organism that causes a diease)
-Antibiotics: Drugs that you ingest (not made by your body) that is going to kill bacteria in general++++Attack target in bacterial cells necessary for cell survival that our cells don’t have
III. Prokaryotes no membrane bound DNA
a. Archaea: Thought to have not changed much for billions of years
i. No nucleus, like bacteria, but otherwise move similar to eukaryotic cells than to bacteria
ii. Ex: RNA polymerase (enzyme that does transcription)
iii. DNA is transcribed into RNA to make proteins that our cells are made of to make more
iv. Ex2: Archaeal cell membrane chemistry are like eukaryotes (phospholipid bilayer)
v. Exteremophiles: Live in extreme environmentsgeysers, ocean vents, other water with very high temps., dead sea and lots of others
b. Bacteria:
-Prokaryotes, very distinct cell wall and cell membrane structures, distinct RNA polymerase (rifampinbacteria, inhibits the bacterial polymerase)
i. Gram-Positive Bacteria
1. Minority of bacteria on earth, but important clinically
-Why gram stain works: Crystal violet and Iodine clump in cell staining cell purple, it is then decolorized with ethanol starting to dissolve the clumps.
-30 layers of cell wall clumps that don’t come apart easily
ii. Gram-Negative Bacteria
1. Outer Membrane-kind of like phospholipid bilayer contains lipopolysaccharide (LPS)(contains a fat and sugar) lipohydrophobic
2. LPSoutside leaflet, phospholipidsinside leaflet
a. Unique to gram-negative
-Our bodies act violently against things that are never found in human cells (LPS and LTA)
-Other points on LPS & LTA
-Inflammatory response reacts very violently against non-eukaryotic chemicals
-Too much LPS or LTA in bloodviolent inflammation which often causes death
-Lipid A, inside part of LPSmost violent response
iii. Acid-Fast
1. Outer Membrane-ish of mycolic acid dense waxy molecule advantageous because they are very resistant to drying out; can survive for a long time in dry environments lots of soil bacteria are acid fast
a. Waxy mycolic acid prevents gram stains from penetrating bacteria ell envelope
-Consequences of cell wall (peptidoglycan)
b. Clearly defined shapes:
i. Round/Spherical: Cocci
ii. Tube/Cylindrical: Baccilli
iii. Spiral/Corkscrew: Spirochetes
iv. Microplasmas: lack cell wall entirely
1. Plasma Membrane
2. No clearly defined shape
a. Ex: Chlamydia
IV. Non-Cellular Organisms
-Questionably alive because it needs a host cell to survive and reproduce
a. Viruses: Must use host cell’s genetic machinery to replicate themselves & smaller than bacteria
-Living things have DNA as their genetic material but some viruses don’t
-Bacteria: 1-5 µm (µm=10^-6)
-Viruses: 20-500 nm (nm=10^-9)
-Hundreds of times smaller than bacteria
i. DNA Viruses: Have DNA as genetic material
ii. RNA Viruses: Have RNA as genetic material
1. Retroviruses: Often lead to cancer because of effects on genetic machinery of host cell
b. Prions: No genetic material, just proteins but can still replicate