01_Bacteria Structure Flashcards
Note: These are just a few cards. In info was mostly review for me.
Note: These are just a few cards. In info was mostly review for me.
When stained, what are the colors of gram positives? Gram negatives?
- Positives = violet
* Negatives = red
What are Koch’s postulates?
- find bacteria that causes disease
- grow bacteria in culture
- reproduce disease
- re-isolate bacteria from disease
What are Koch’s Molecular Postulates?
- The phenotype of the specific gene should be associated with a pathogenic strain
- Knock out should lead to reduced virulence
- Knock in should restore of virulence
What are the distinguishing characteristics (cell wall? Pathogenic? Energy source? Nucleus?) of… Algae Fungi Protozoa Bacteria
- Algae: no pathogens, all photosynthetic, nucleus
- Fungi: some pathogens, non-photosynthetic; rigid cell wall; (fungi, including pathogenic fungi, will be discussed later in the course); nucleus
- Protozoa: some pathogens, no rigid cell wall; unicellular, nonphotosynthetic. Some parasites have cysts with a rigid cell wall. Ameba, Paramecium, Euglena; nucleus
• Bacteria:
o many pathogens
o most require organic compounds as energy source
o some of the non-pathogens are photosynthetic
o all (with one exception) have a rigid cell wall
o Nucleus
Explain the differences in movement of eukaryotes and prokaryotes.
- Euks: Cytoplasmic streaming (amoeboid), flagella, cilia
* Proks: flagella (with no microtubules, and does have H-Antigen)
Explain the differences in cell wall of eukaryotes and prokaryotes.
- Euks: Plants and algae have polysaccharide (glucose); fungi have chitin (acetyl glucosamine polymer) and beta1,3 glucan (glucose polymer)
- Proks: peptigoglycan polymer containing muramic acid (derivative of acetyl glucosamine); D-amino acids
What are the three shapes of bacteria?
- Coccus (round)
- Bacillus (rod)
- Spiral
Do bacteria have sterols in the cytoplasm or membrane?
- No. There is only one exception: mycoplasma.
- Euks do contain sterols.
- Proks DO NOT contain sterols
What is a diagnostic quality of Streptococci with regard to cell division? What about Staphylococci?
- Streptococci: form long chains
* Staphylococci: form clusters, like grapes
What are the layers of a gram +?
- membrane
- Thick peptidoglycan (not an antigen) with Teichoic acid (antigen) and Lipoteichoic acid (antigen)
- Note: Teichoic acid uses the sugar Ribitol
What are the layers of gram -?
- Inner membrane
- Thin peptidoglycan
- Outer membrane with Lipopolysaccharide (LPS) (endotoxin and O-antigen) and porins (passively transport
- Capsule (?)
- Note: There is the periplasmic space between the inner and the outer membrane
What is the H-antigen? What is the O-antigen?
- H = flagella
* O = LPS
What is the only bacteria without a cell wall?
• Mycoplasma (not mycobacteria!
What are the components of the cell wall in bacteria?
- N-acetyl glucosamine (NAG) linked to N-acetyl muramic acid (NAM) (this is a glycosidic bond)
- Short peptide (4 aa) linked to the lactic acid residue of the NAM
- Forms a chain linked fence
- This is called a peptidoglycan
How does penicillin affect the cell wall?
• it blocks the chain linking of the fence and the bacteria die
How does lysozyme (in tears) affect the cell wall?
• splits the glycosidic bond between NAG and NAM
What are the differences between gram – and gram +?
• see A-16 in notebook
What are the functions of the gram – outer membrane?
• B barrier to antimicrobial agents
• reacts with antibodies
• blocks entry of large molecules
o ex: lysozyme cannot degrade cell wall unless part of the outer membrane is removed
• more resistant to antibiotics and detergents than gram +
What is the function of porins in the outer membrane of gram -?
- Porins allow passive transport of small molecules and block other molecules
- Antibiotics against gram – must pass through porins in order to work on gram –
What is lipopolysaccharide (LPS)?
- found in the outer membrane of gram –
- Know: the Lipid A portion is embedded in the outer membrane, where as the oligosaccharide (the O antigen) is exposed to the environment
- There are many O antigens even within species of bacteria and are responsible for immunological specificity (different serotypes)
What is found in the periplasmic space in gram - ? How do gram + mimic this function?
- gram - : protective enzymes that degrade foreign molecules (like antibiotics)
- gram + : extrude degradative enzymes into its immediate environment
Explain the gram staining procedure.
- Stain with violet (violet enters the cytoplasm)
- Treat with iodine (the iodine binds with the violet)
- Wash with ethanol (the thick peptidoglycan of gram + traps the purple inside; for gram – the purple washes out)
- Counter stain with red (stains gram – red)
What are the exceptions?
- old gram + sometimes lose their purple-stain-retaining property
- If the cell wall of gram + were removed, it would stain as gram -
- There are “gram variable” bacteria exceptions. Some of these are medically important
