Bacteria Structure & Function Flashcards
1
Q
Identification of Bacteria
A
- Starts w/ knowledge of colony appearance on plates & growth requirements
- appearance of individual bacterial cells
- staining characteristics
2
Q
Gram staining - what is it
-how does it work
A
- Gram staining differentiates bacteria by chem. & physical properties of their cell walls - detects peptidoglycan
- Gram positive retains crystal violet due to thick layer of peptioglycan
- Gram negative lose crystal violet (are stained with counter stain safranin [pink]) due to v. thin peptoglycan wall
*is first step in identifying bacteria
3
Q
Gram staining - what is it
-how does it work
A
- Gram staining differentiates bacteria by chem. & physical properties of their cell walls - detects peptidoglycan
- Gram positive retains crystal violet due to thick layer of peptioglycan
- Gram negative lose crystal violet (are stained with counter stain safranin [pink]) due to v. thin peptoglycan wall
4
Q
To get a good gram stain (3)
A
- Use young cultural bacteria - gram positive bacteria that is old can leach out crystal violet (gives false impressions as to what’s in sample)
- Very thin smear of cells
- If staining unknown bact., use controls
5
Q
Unique features of prokaryotes
A
-They don’t have a nucleus
6
Q
Components of Bacteria; Ribosomes
A
- site of protein synthesis
- composed of RNA and protein
- abundant in bacteria due to fact they are continuously producing proteins (many of their genes are inducible)
7
Q
Components of Bacteria; Nucleoid
-Features of Bacterial DNA
A
- Is a region in the cell where the chromosome is (usually single chromosome)
- composed of DNA (usu. ds) in circular formation (although are cases where it’s linear)
- Does not have introns
8
Q
Components of Bacteria; Plasmid
A
- extra chromosomal DNA free in cytoplasm which encodes genetic information - usu. provide bacteria w/ extra proteins and abilities (i.e. toxins, cell adhesion proteins & enzymes)
- Can share DNA plasmids amongst bacterial cells (via conjugation using pili)
9
Q
Components of Bacteria; Nucleoid
-C+G content
A
- Is a region in the cell where the chromosome is (usually single chromosome)
- composed of DNA (usu. ds) in circular formation (although are cases where it’s linear)
- Does not have introns
-Chromosome: C+G content varies from 24% to 70% depending on genus and species
10
Q
Components of Bacteria; Plasma Membrane
A
- Bilipid membrane, fluid mosaic structure w/ proteins embedded (transport)
- Retains cytoplasm
- semi-permeable
- Location of metabolic processes (ATP generation requires electrons flowing across membrane)
- contains receptor molecules that can assist w/ gene regulation w/in cell
11
Q
Components of Bacteria; Cell Wall
A
- Chemically complex, rigid structure
- is what gives bacteria shape*
- protects it from osmotic lysis
- has a role in pathogenicity
- Is a site of action for antibiotics (i.e. penicillin - inhibits enzymes involved in cell wall synthesis)
-Most bacteria have one - not mycoplasmas
12
Q
Cell wall - peptidoglycan subunit
A
- Sugar based molecule w/ a.a. linked to it
- contains unusual a.a. not found in proteins (have different structure)
- Is a major component of cell walls
- aka murein
- is a large polymer
13
Q
Gram Positive vs Gram negative envelope - structure
A
- Gram positive = large peptidoglycan layer w/ lipteichoic & telchoic acid embedded w/in
- periplasmic space between layer and plasma membrane
- Gram negative: outer membrane (has lipopolysaccharides), thin layer of peptidoglycan w/in periplasmic space and has another plasma membrane
-Gram positive sensitive to penicillin and lysozyme (gram negative isn’t)
14
Q
Cell wall - peptidoglycan subunit
A
- Sugar based molecule w/ a.a. linked to it
- contains unusual a.a. not found in proteins (have different structure)
- Is a major component of cell walls
- aka murein
- is a large polymer
- made of N-acetylglucosamine & N-acetylmuramic acid
15
Q
Cell wall - Lipopolysaccharide
A
- found in gram negative bacteria. Has 3 import. regions:
1. O polysaccharide (outer portion): repeats of 4-5 sequences of sugars - may be branched
- antigenic, generates specific immune response
- highly specific, gives the serotype to bacterium
2. Core polysaccharide (R=rough)
3. Lipid A: endotoxin made of fatty acids and N-acetylglucosamine - is the toxic element of LPS
