3/17/13 - Gram +/- Flashcards
What are Koch’s Postulates?
1) Find the bacteria in disease.
2) Grow the bacteria in pure culture.
3) Reproduce the disease in animals using the pure culture.
4) Reisolate the bacteria from the experimental infection
Koch’s molecular postulates
1) Phenotype under investigation should be associated with a pathogenic organism
2) speific inactivation of a gene should lead to decrease in virulence
Restoration of pathogenicity should result by replacing the mutated virulent gene with the WT
Classes of Microorganisms
1) Algae - no pathogen, all photosynthetic
2) fungi - some pathogen, non photo, rigid cell wall (chitin)
3) Protosoa - some pathogens, no rigid cell wall, unicellular, nonphoto ( some cysts have rigid walls)
4) Bacteria - many pathogens, many need organic compounds as energy source. Some non-pathogens are photo. All, but one, have rigid cell wall
Chromosomes - Euk vs Prok
Eucaryotic - nuclear membrane. Linear chromosomes, mitosis
Procaryotic - one circular chromosome not bound by nuclear membrane. Chromosome segregation, no mitosis.
MT and other membrane structures - Euk vs Prok
Eucaryotic - MT has oxidative enzymes for oxidative phosphorylation. Vacuoles, perioxisomes
Procaryotes - No MT. Oxidative phosphorylation associated with cytoplasmic membrane
Cellular movements - Euk vs Prok
Eucaryotic - cytoplasmic steaming (amoeboid) or contraction of flagella (cilia). Cilia is a 9+2
Procaryotic - No cytoplasmic streaming. Some have flagella known as H-antigen. No microtubules. Instead, it is a long helical rod made of flagellin. No membrane coat.
Cell wall - Euk vs Prok
Not found in animal cells
Eucaryotic - higher plants and algae made of polysaccharide cellulose. In fungi is made of chitin and beta 1,3 glucan.
Prokaryotic - made of a peptidoglycan polymer, containing MURAMIC acid (made of acetyl glucosamine) and D-AA. Penicillin interferes with formation of peptidoglycan.
RNA - Euk vs Prok
Eucaryotic - RNA transcribed in nucleous, spliced and transported to ER for protein making.
Procaryotic - no nucleous, RNA translated as made. No splicing.
Size of Bacteria
Light microscope resolving power
~1 um (0.001 mm, 1000 nm)
Light - 0.2um
Morphology of Bacteria
1) Coccus
(Pneumococcus and Gonococcus are elongated cocci. Staph is perfect circle)
2) Rod / Bacillus
(some gram - rods look a lot like cocci)
3) Curved Rod or spiral
(spirochetes, such as Treponema pallidum that causes syphillis - dont have a very rigid cell wall.
Arrangements
1) chain of cocci - Steptococci)
2) irregular cocci - Staphylococci
3) rod division at right angles - common among aerobic Bacilli
4) stacks of rods - corynebacterium
Binary fission
Bacteria multiplication using a central transverse wall.
Contents of a typical bacterial cell
1) Cytoplasmic membrane
2) Nuclear equivalents (nucleoid)
3) Cell wall
4) Capsule (optional)
5) Flagella (optional)
Cytoplasmic membrane
Semipermeable phospholipid bilayer. Rarely contains sterols.
Function:
1) contains oxidative enzymes and resembles inner membrane of MT
2) contains enzymes that make cell wall
3) Transport - active, selective, diffusion
4) excrete toxins
Nucleoid
Bacteria nuclear equivalent. No chromosome or membrane
Periplasmic space
Between cytoplasmic membrane and outer membrane. Find enzyme degrading extracellular substances
Ribosomes
Bacterial is 70S (human 80S) and is smaller
Cytoplasmic Granules
Storage bodies in cytoplasms when excess food is available. Ex - high molecular weight lipid or glycogen.
Metachromatic granules - polymerized phosphate. Stains dark, dound in Diptheria (Corynebacterium diphtheriae)
Cell wall
20-30% weight. All except MYCOPLASMA have cell wall. The structure is a polymer of N-acetyl glucosamine (NAG) linked to muramic acid by glycosidic bond. Also linked to 4 AA in a D-conformation
Peptidogycan
CROSS-Linking gives rigidity - Binding through AA side chains of COOH of tetrapeptide to another neighbor
Muramic acid
N-acetyl glucosamine linked to lactic acid.
Penicillin
Blocks cross-linking of peptidoglycan
Lysozyme
splits glycosidic bond between N-acetyl glucosamine and muramic acid.(NAG)
Gram positive characteristics
Contain thick peptidoglycan as well as different carbohydrate polymers. No phospholipid outer membrane.
Examples - staphylococcus, streptococcus
Ribitol phosphate (sugar alcohol) in staph or teichoic acid linked to peptidoglycans act as antigens. in outside later of peptidoglycan.
Order:
Polymer
Peptidoglycan
cytoplasmic membrane
Gram negative characteristics
Peptidoglycan later (mucopeptide) is thinner. They have an outer membrane OM whcih contains lipoposaccharides on the outer surface (LPS).
Order:
OM
Peptidoglycan
Cytoplamic membrane
Periplasmic space found ONLY in gram - bacteria. Contains binding proteins and hydrolytic enzymes. Found between the inner and outer membranes
Porins in outer membrane allow entry of nutrients by diffusion
