Bacteriology lecture 1 Flashcards
What is the estimated amount of microbial cells on earth?
~5 million trillion trillion (10^30)
What is the professors favorite bug?
Listeria
Phylogeny
Science dealing with evolutionary relationships between living organisms
What is Phylogeny based on?
Sequence of macromolecules such as DNA, RNA and protein - Phylogenetic trees
What are the 3 phylogenetic distinct lineages of cells?
2 Prokaryotic (Eubacteria and Archea) 1 Eucaryotic
Who came up with Endosymbiont Theory?
Lynn Margulis
What was the Endosymbiont Theory?
A major organizational event in the history of life probably involved the merging of two or more lineages through symbiosis.
Single-celled prokaryotic microorganisms and their DNA is not contained within a separate nucleus as in eukaryotic cells are?
Bacteria
What characteristic are used to classify and identify bacteria?
Shape and size
Approximate size of bacteria
0.1-10.0 um in size
Bacteria, bacillus/bacilli means
Rods (little stick)
Coccus/Cocci means
Round
Pleomorphic means
Bacteria which can assume many shapes
What give spirochete the more pronounced shape?
Internal flagella
Strepto means
chain
Diplococci means
two coccus
Tetrad means
four
Staphylo means
cluster
What divides bacteria individual from the environment?
Cell wall
Cell wall is present in all eubacteria except?
Mycoplasmas
In prokaryotic cell’s wall is located?
Outside the plasma membrane
Most archaeobacteria do not have a cell wall, but those that do have?
A different type of peptidoglycan or protein
Functions of the cell wall?
Prevents osmotic lysis, protects cell from external stress (host), contributes to virulence, target for antimicrobials
What is a cell wall?
Rigid structure surrounding the cell membrane
Two ways of characterize a bacteria cell wall
Gram stain
Acid fast stain
The four characterizations of the bacteria cell wall
Gram-positive
Gram-negative
Acid Fast
Wall-less
What is the chief structural & composition component of a eubacteria’s cell wall?
Peptidoglycan
Peptidoglycans are composed of?
Long chains of polysaccharides (glycan) cross-linked by short proteins (peptides)
The constitution of the polysaccharide is by what two repeating subunits?
N-acetyl glucosamine and N-acetyl muramic acid
When polysaccharide chains are cross-linked by peptides and then linked together create the?
Single rigid mesh-like molecule that forms the cell wall (chain link fence)
What determines the major difference between gram + and gram -?
Peptidoglycans in the cell wall
Gram neg peptidoglycans
Mesh is only one layer thick
Gram posit peptidoglycans
Wall is many layers thick (40)
Staining
The appearance of bacteria following the gram stain is also used for Identification
Purple/blue stained bacteria are?
Gram-Positive
Gram-Negative bacteria stain?
Pink/red
The difference in response to the Gram stain results form the ?
Composition of the cell envelope
What is the unique structure for Gram-neg bacteria?
Lipopolysaccharide (LPS)
What is an advantage of lipopolysaccharide in Gram-neg?
Major permeability barrier
Where do Gram-neg bacteria store degradative enzymes?
In the periplasmic space
Gram-pos bacteria secrete what? and why?
exoenzymes and preform extracellular digestion
Where is the periplasmic space?
Between the lipopolysaccharide membrane and peptidoglycan membrane.
What are the two staining methods?
1) Simple stain - Basic dyes
2) Differential Stain - combination of basic dyes
Basic dyes
Have a positive charge and bind to negatively charged bacteria at ~pH-7
Acidic dyes
Have a negative charge and stain background
Gram staining procedure
Fixation Crystal Violet (primary stain) Iodine treatment Decolonization (alcohol/acetone) Counter stain with Safranin
If you get Coccus with pink stain what have you done?
Very few Gram-neg Coccus. You have left the stain in the decolonization too long.
Acid fast staining procedure
Carbol fuchsin
Acid alcohol decolorizer
Counterstain malchite green or methylene Blue
Rest the dilute acid
Difference between acid fast and non acid fast bacteria?
Acid fast will remain the same color as the first stain used. Non acid fast will show up with a blue color.
What is responsible for Acid Fast staining?
The mycobacterial cell wall contains long chain length fatty acids (mycolic acids and waxes) which contribute to virulence.
Teichoic Acid and Lipoteichoic acid
Appear to extend the surface of the peptidoglycan layer in Gram-Positive Bacteria
What does Teichoic Acid do?
Provide rigidity to the cell wall
Assist in regulation of cell growth
Receptor molecules for some Gram-Positive bacteriophage
How does Teichoic Acid provide rigidity to the cell wall?
By attracting cations such as magnesium and sodium.
How does Teichoic Acid assist in regulation of cell growth
By limiting the ability of autolysins to break the Beta (1-4) bonds between the N-acetyl glucosamine and the N-acetylmuramic acid
What is the most important part of Gram-Neg bacteria?
Lipopolysaccharide
What are the three parts of the Lipopolysaccharide?
Lipid A-
Core oligosaccharide
O antigen
What does the Lipid A of the Lipopolysaccharide do?
Embedded in the membrane is responsible for endotoxin activity
What unique about the Lipid A of the Lipopolysaccharide?
C14 Fatty Acid *hydroxy myristic acid, phosphates, glucosamine
What unique about the Core oligosaccharide of the Lipopolysaccharide?
Highly conserved among different bacteria
Unique components -KDO (3-deoxy-D-manno-2-octulosonic) acid and heptose
What unique about the O antigen of the Lipopolysaccharide?
Presents is species dependent
Composed of repeating units consisting 3 to 4 CHOs polymerized into polysaccharide
Antigenic and highly variable among species and strains
What is the most potent immune system activators in the Lipopolysaccharide?
Lipid A - Endotoxin
What is the test for endotoxin Lipid A?
Limulus Amebocyte Lysate (LAL) Test
What are the specifics of the LAL test?
It is an aqueous extract of the blood cells from the horseshoe crab
What plays a critical role in the architecture and impermeability of the cell wall in mycobacteria?
Mycolic acid
How do we visualize bacteria?
Compound light microscope
Dark-field microscope
Fluorescent microscope
Electron microscope
What is the difference between Light and Electron microscopes?
Light- uses visible light
Electron - uses electron beams
What is the difference between Negative and Positive stain?
Negative - stains the background
Positive - stains the structures
