My notes from lecture today and friday! If you missed anything this will hopefully help! :)
Microbiology
September 11, 2009
Bacteria Structures, Continued….
I. External bacterial layers
a. Polysaccharide capsule
i. Very dense carbohydrate coat that is outside the outer most layer of the bacteria we’re using
ii. Much thicker than any of the other layers
iii. Keeps bacteria from drying out
iv. Helps prevent phagocytosis
b. Crystalline surface layers
i. Made of protein
ii. Same advantages as polysaccharide capsule (^ i-iv ^)
c. Biofilms
i. Big elaborate messes of lipids, carbohydrates, and proteins
ii. Built collectively by communities of bacteria
iii. ‘Goo’ that holds bacteria together until it breaks down
iv. Advantages are similar to capsule and crystalline layers. (^)
1. Additionally, help protect bacteria against antibiotics and disinfectants – very difficult for those to get through the ‘goo’ and kill bacteria
II. Cell Wall and Membrane Protein
a. Integral Membrane Proteins
i. Transmembrane pumps and pores: made of integral membrane proteins:
b. Peripheral membrane proteinsstrikethrough text HAVE NOT DONE YET
III. Bacterial genetic structures, anthrax, and 9/11/09
a. Bacterial DNA in tight, wound up bunches when not being used
b. DNA gyrase unwinds and bunches
i. Ciprofloxacin destroys DNA gyrase
c. Nucleoid (not a nucleus)
i. All curled up and bunched up bacterial DNA
1. No membrane
ii. Most bacteria have circular chromosomes
1. Almost all bacteria have only one chromosome per each bacterium
a. So all traits are dominant because there’s nothing competing against it
iii. In contrast: Eukaryotic chromosomes are almost always linear
1. Come with more than 1 per bacterium (generally)
2. Chromosomes are in sets (generally)
3. Eukaryotic cells copy chromosomes and the more they get copied the shorter the chromosomes get – one reason of death – cells just die instead of replicating chromosomes
iv. DNA gyrase & topoisomerase IV
d. Plasmids
i. Little circles of DNA (small) that bacteria may have in addition to their chromosomes
ii. Contains just a few genes – “accessory genes”
1. Genes for “bonus” - Genes that might help tie everything together, but aren’t super necessary
a. Ex. Antibiotic resistance genes
b. Ex. B anthracis gene for lethal factor is on a plasmid
i. Number of copies - plasmid can predict how bad the symptoms will be from the lethal factor protein
1. More protein = worse
iii. Easily shared among bacteria – If we see resistance in some bacteria we’re worried about that resistance being spread to other bacteria
e. A story about ciprofloxacin and September 11
i. A church-going family man that volunteered at Red Cross started sending letters filled with anthrax to people
1. He wanted people to take the idea of bioterrorism seriously
ii. He told them in the letters to take penicillin a.s.a.p
Why were all of the people given ciprofloxacin instead of penicillin?
- They didn’t want to take what the terrorist would tell them to take because he’s supposed to be trying to kill them
- 1000’s of people were given ciprofloxacin for 60 days – very long
o Caused joint problems and other side effects
o Cost way too much money
- 2001: Some strains of B. anthracis that had been genetically engineered to be penicillin-resistant
o Got this way because scientists had put plasmids from other penicillin-resistant bacteria into anthrax bacteria to make them better weapons
IV. Ribosomes
a. Synthesize proteins (by translating mRNA into an amino acid sequence) – all god’s children need proteins so all god’s children need ribosomes
b. Brings us back to point 2
Are ribosomes a good target for antibacterial drugs?
