L1: Phylogeny and Morphology of Bacteria Flashcards
What is the traditional definition of a prokaryotes in terms of: Chromosome number: Chromsome ploidy: Chromosome shape: Nuclear membrane presence: Mitosis occurrence: Ribosome size: Mitochondria, ER presence: Phagocytosis occurring: Sterols in membrane:
Chromosome number: 1 Chromsome ploidy: Haploid Chromosome shape: Circular Nuclear membrane presence: No Mitosis occurrence: No Ribosome size: 70S Mitochondria, ER presence: No Phagocytosis occurring: No Sterols in membrane: No
What is the traditional definition of eukaryotes in terms of: Chromosome number: Chromsome ploidy: Chromosome shape: Nuclear membrane presence: Mitosis occurrence: Ribosome size: Mitochondria, ER presence: Phagocytosis occurring: Sterols in membrane:
Chromosome number: >1 Chromsome ploidy: Dipoid or higher Chromosome shape: Linear Nuclear membrane presence: Yes Mitosis occurrence: Yes Ribosome size: 80S Mitochondria, ER presence: Yes Phagocytosis occurring: Yes Sterols in membrane: Yes
What problems have arisen with the traditional definition of prokaryotes? (4)
- Many bacteria have >1 chromosome
- Ploidy is variable based on growth rate
- Many bacteria have linear chromosomes
- Shouldn’t use negatives to define a category
What is the only remaining defining feature of bacteria?
Ribosome size
What is the ribosome made of?
What does this mean for defining bacteria?
What does this mean for evolution?
RNA
Differences between pro and euk are differences in RNA composition.
Can use nucleotide sequencing to determine the evolutionary relationships of all organisms
Using recent analysis, what has the traditional all-encompassing kingdom of prokaryotes been split into?
(Eu)Bacteria
Archaea
All known human bacterial pathogens are from what domain of prokaryotes?
Eubacteria
All of the kingdoms of eukaryotes have been united into what?
Eukarya domain
Which has more subdivisions, eukarya or the two prokaryotic domains?
What does this mean?
Two prokaryotic domains
Bacteria are more diverse than eukaryotes
The genomes of chloroplast and mitochondria are related to many bacterial species, suggesting what?
That the endosymbiotic theory of eukaryotic cellular evolution is correct.
Do the vast majority of bacteria have any impact on humans?
No
Bacteria are critical for what two things? (2)
- Recycling of environmental materials
2. Maintaining a healthy environment
Can bacteria be domesticated?
Yes such as in fermentation of alcohol
Of the few bacteria that interact with humans, are most harmful, harmless, and/or beneficial?
Harmless or beneficial
These bacteria that are harmless or beneficial to humans are called what?
Natural flora
In the human body, how do the cell numbers of human cells and bacterial cells compare?
10X more bacterial cells than human cells in human body.
In the human body, how do gene numbers of human genes and bacterial genes compare?
100X more bacterial genes than human genes in body.
What is the rigidity of the bacterial cell wall due to?
Peptidoglycan
Which is the first big stain to use when determining bacteria?
Gram stain
The gram stain separates cells based on what?
Being either Gram positive or Gram negative which is based on their cell wall architecture
Relatively speaking, how many bacteria have peptidoglycan in their walls?
Nearly all
What does a peptidoglycan consist of?
- Peptide: Amino acids
2. Glycan: sugars
The glycan portion of peptidoglycan consists of what? (2)
- N-acetylglucosamine (NAG)
2. N-acetyl-muramic acid (NAM)
What are the two exceptions to bacteria with peptidoglycan in their cell walls?
- Mycoplasma
2. L-Forms
Describe the organization of the sugars in peptidoglycan?
Alternating NAG and NAM
Describe the organization of peptide in peptidoglycan.
A chain of mixed D- and L- amino acids attached to NAM with a di-amino acid in the third to last position and ending with D-ala-D-ala.
what is a di-amino acid? (2)
- lysine
2. diaminopimilic acid
Is the composition of the D- and L- amino acids always the same for bacterial peptidoglycan?
No, varies by species
How does cross linking occur between peptides of the same peptidoglycan?
The penultimate D-ala of one peptide chain joins with diamino acid of another which causes deletion of the terminal D-ala of the first.
Does the peptide bridge vary much?
Yes, from direct linkage between the two peptides to several amino acids
What allows for the crosslinking between glycan chains?
The peptide chain flexibility
Purpose of crosslinking of peptidoglycans?
Formation of meshwork that provides tensile strength necessary to (1) restrain the cytoplasm and (2) give the cell shape.
What pressure does crosslinking try to combat?
Turgor pressure
Gram positive cell walls have what 3 main features?
- Thick (up to 30 layers) of peptidoglycan externally
- Wall- and lipo-techoic acids
- Integral membrane proteins
Is PTG permeable?
Yes
Which have a higher internal osmotic pressure, gram positive or gram negative bacteria?
Gram positive
In layman’s terms, what are wall- and lipo-techoic acids?
Repeating sugar phosphate chains
Function of wall-and lipo-techoic acids?
Give cell negative charge in order to attract positive charges adding strength to the wall
Do gram-negative cells have wall- and lipo-techoic acid?
No
3 components of gram-negative cell wall?
- Outer membrane
- Thin peptidoglycan layer
- Peri-plasm separating inner and outer membranes and contains the peptidoglycan and proteins for processing solutes
What does the outer membrane act as for gram-negative bacteria?
Permeability barrier
The outer membrane of gram-negative bacteria consists of what four parts?
- Phospholipids like those in inner membrane
- Lipoproteins: Attach PTG layer to Outer
- Porins: Allow some diffusion
- Lipopolysaccharide
What are the 4 parts of lipopolysaccharide?
- O-antigen
- Core polysaccharide
- Disaccharide diphosphate
- Fatty acids
Together, the disaccharide diphosphate and fatty acids of LPS make up what?
Lipid A
Lipid A of LPS is known as what?
Endotoxin
Result of Endotoxin in the blood?
Fever, shock, and death during gram-negative infections
The O-Antigen has what significance in immunology?
It is a major antigenic determinant and is used to characterize bacteria
What are the five steps of a gram stain.
- Fixation
- Crystal violet
- Iodine treatment
- Decolorization
- Counter stain of safranin
What is the key step of a gram stain?
Decolorization step
How does decolorization affect both gram positive and gram negative?
Gram positive: Dehydrates the PTG thus trapping the stain
Gram negative: Strips the outer membrane from the cell allowing the primary stain to escape
Mycoplasma stain what?
Gram negative even though they are closer to Gram-positive since they dispensed with a cell wall
What color is gram positive?
Purple
what color is gram negative?
Pink
Describe the set up of a mycobacterial cell wall
Gram positive cell wall with an outer membrane that is NOT similar to a gram negative OM.
Mycobacterial cell wall consists of what 3 things?
- Thick peptidoglycan layer
- Arabinogalactan (sugar) layer
- Mycolic acids/Wax D
What 3 main bacteria don’t have a cell wall
- Mycoplasma
- L-forms
- Domain archaea
What causes mycoplasma to have such a strong membrane?
Sterols
What do archaea have instead of peptidoglycan?
Pseudopeptidoglycan
Why don’t mycobacteria stain well?
Stains can’t penetrate the mycolic acid wax
How does one stain for mycobacteria?
Acid fast stain
What are the steps of the acid fast stain?
- Carbol Fuchsin primary stain steamed in to penetrate the membrane and stian the cells red.
- Acid alcohol leaches the stain out of all cells that are NOT mycobacteria
- Methylene blue counterstains the leached cells