Microbiology Lecture Notes September 11

- No cell wall
- Plasma membrane
- Do not have clearly defined shape because of lack of cell wall
- Ex) clamidyia is an example
- Maybe another membrane (not necessarily the same as gram-negatives’ outer membrane though)

Non-cellular organisms
Has to have a host cell to make its own DNA and survive
Why are only questionably alive?
lack any cellular machinery to replicate their own DNA
must use host cell genetic machinery to replicate selves
cannot copy their own genetic material w/o a host cell
everything we have talked about so far (living things) have DNA as genetic material
some viruses don’t have DNA as their genetic material
Size scale:
much smaller than bacteria
bacteria: 1-5 mm (mm=10^-6)
Viruses: -20-500 nm (nm=10^-9)
Hundreds of Xs smaller than bacteria
DNA viruses
DNA as genetic material
RNA viruses
Have RNA not DNA as their genetic material
Subcategory of RNA viruses
Infect eukaryotic cells and screw with our replication machinery while they are making copies of their RNA
Often leads to cancers b/c of effects on genetic machinery of host

- Prions
Smaller than viruses
No DNA or RNA/genetic material at all
Are capable of making copies of themselves (mad cow disease)

Bacterial Structures Continued
- External bacterial layers
Polysaccharide capsule
Made of polysaccharides (sugar) very carbohydrate dense coat
Outside the outermost layer of the bacteria
Helps bacteria stay moist by pulling water out of the atmosphere and providing it to the bacteria
Thick guey carbohydrate coat around the bacteria prevent our WBCs from phagocytosis of the bacteria
Crystalline surface layers
Made of protein
Some advantages as capsule
can have a crystalline surface layer and a polysaccharide capsule
Lipids, carbohydrates, proteins (biofilm) that are built collectively by many bacteria
Built by communities of bacteria
Help bacteria keep from drying out
Prevent phagocytosis; makes it larger than the phagocytes
same advantages of crystalline surface layers and polysaccharide capsules plus:
help protect bacteria from antibiotics and disinfectants
can’t get through the goo to the bacteria
Cell wall and membrane proteins
Integral membrane proteins
Transmembrane pumps and pores: made of integral membrane proteins
Peripheral membrane proteins
Bacterial genetic structures, anthrax, and 9/11
Nucleoid (not a nucleus)
Most bacteria have circular chromosomes unlike eukaryotes
Bacterial DNA is in tight, wound up bunch when not being used
DNA gyrase & topoisomerase IV
DNA gyrase
unwinds the bunches of DNA
Ciprofloxacin destroys the ability of DNA gyrase to do this which
makes the bacteria unable to make any new proteins and unwind the DNA
Bacillus anthracis
- Spore forming bacteria that makes durable structures that can persist in the env. For a long time
- If it gets in a wound the skin turns black and falls off
- If in the lungs same damage as to skin
- Ciproflaxacin was used to treat people exposed to anthrax so that the antrax bacteria could not unwind their DNA and reproduce
- this caused serious side effects to the people who used the antibiotic
- why did so many people get prescribed Cipro?


A story about ciproflacin and September 11

Amy Blass

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