Microbial Structure and Function Lecture Sep 6 Flashcards
Are the following prokaryotes or eukaryotes?
Bacteria
Protozoa
Fungi
Viruses
Bacteria–prokaryote
protozoa-eukaryote
fungi-eukaryote
viruses–neither
How do prokaryotes and eukaryotes differ in their chromosomal organization and location?
Where are their extrachromosomal DNA?
How do they differ in cellular respiration site?
Which have pili?
Prokaryotes have a single, circular chromosome which is located in the nucleoid (with no membrane). Extrachromosomal DNA is on plasmids.
Eukaryotes have pair linear chromosomes located in the nucleus (separated by a membrane), and the extrachromsomal DNA is located in mitochondria and chloroplast.
THe iste of cellular respiration is the cell membrane in prokaryotes and the mitochondria in eukaryotes.
Only prokaryotes have pilli.
What is the difference between the ribosomes of prokaryotes and the ribosomes of eukaryotes?
They both have ribosomes, but the ribosomal proteins are different.
Prokaryote: the70S ribosome with the 30S and 50S subunits.
Eukaryote: the 80S ribosome with the 40S and 60S subunites in the cytoplasm (but 70S in organelles).
What are the two basic bacterial shapes?
What are some other shapes?
Baccilus (rods) and cocci (spheres) are the main two.
Others include spirochetes (FLEXIBLE undulating corkscrew), spirillum (RIGID corkscrew shape), diplococci, diplobailli, pleymorphic.
What are the main group arrangments for bacteria?
single, diplococcus, chains, clumps, cubical, tetrads
Two baccili together are called what?
Chains of bacilli are called what?
Other arrangements like side by side Y V or Y figures of baccili are called what?
Diplobacilli
Streptobacilli
palisades
What is the difference between the shape of a spirochete and the shape of a spirillum?
A spirochete is a flexible undulating corkscrew
A spirillum is a rigid corkscrew
(mnemonic: just think that the two ‘L”s in spiriullum are stick rigidly together because they want to be paralell.)
In bacteria, what is the nucleoid?
What is the mesosome?
The nucleoid is where the chromosome exists.
The mesosome is where chromosomal DNA attaches to the bacterial membrane invaginated at the site of bacterial division.
In bacteria, what is a self-replicating unit of DNA distinct from the chromosome called?
What does a bacteria use it for?
Why is this of particular medical importance?
The plasmids.
They are often mobile and the bacteria use them as a way of passing on their genetic information into other bacteria (usually intraspecies but interspecies as well).
They frequently confer newer pathogenicities to the bacteria, including ABx resistance.
What do bacteria use to move?
How is this related to the immune response?
What are they composed of?
Bacteria often use flagella to move.
This is related to the immune response because anything on the outside of the bacteria is highly antigenic because it’s foreign and our body will have antibodies against it.
They are composed of flagellin
What are the 4 different arrangements of flagella?
Monotrichous (only 1)
Leophotrichous
Amphitrichous
Peritrichous (many flagella)
What are pili (fimbriae) used for by bacteria?
Piliare shorter and finer than flagella
They are either used for attachment to surfaces (adherence pili) or for bacterial conjugation (sex pili)
In bacteria, what is the capsule?
What is it usually made of?
What is it also known as?
What is it’s purpose?
The capsule is a slimy outer coating on some bacteria.
Usually a complex of high molecular weight polysaccharides
Also known as a glycocalyx, slime, or biofilm
It’s used for adherence and antiphogocytic
What is an important unique component of bacterial cell walls?
Peptidoglycan
What is the general structur of a peptidoglycan wall?
It’s repeating monomers of NAM and NAG with tetrapeptides that are cross lined together to form a wall.
How are a gram positive and gram negative bacteria different?
THey differ in the composition of their cell walls.
Gram positive have thick peptidoglycan layers and a cytoplasmic membrane
Gram negative bacteria have a cytoplasmic membrane, a thinner peptidoglycan layer, then periplasmic space and an outer envelope membrane with LPS
What “color” are gram positive bacteria?
What “color” are gram negative bacteria?
What is being stained in the gram stain?
THe peptidoglycan layer is being stained.
Positive will be purple
Negative will be pink
WHat are the steps of a gram stain?
What color will each type be after each step?
- Heat fix bacteria to a slide
- Dye with crystal violet. All cells will stain blue/purple
- Iodine mordant will fix the stain into the bacterial cell wall (makes complexes that will be too big to pass through the peptidoglycan layer of positive cells, but will pass through the thinner peptidoglycan layer of negative cells). All cells would be purple.
- Alcohol decolorizes gram negative bacteria by washing out the crytsal violet-iodone complexes. Gram positive cells will remain purple, gram negative cells will be colorless
- Counterstain with safranin. This will technically color everything, but because purple is darker than pink, gram positive cells will still look purple and gram negative cells will look pink
Describe a gram positive cell wall.
THere is a cytoplasmic membrane covered with a thick layer of peptidoglycan. Through the peptidoglycan there is teichoic acid. Some of the teichoic acid will stick down into the membrane (lipoteichoic acid), and other teichoic acid will project to the outside of the peptidoglycan.
What is teichoic acid comprised of?
How about teichuronic acid?
Teichoic acid is a water soluble polymer of ribitol or glycerol residues joined by phosphodiester linkages.
Teichuronic acid is similar to teichoic acid, but made in phosphate-limiting conditions.
In gram positive cells, what percentage of the cell wall is peptidoglycan?
80%
Describe a gram negative cell wall.
Gram negative cells have a cytoplasmic membrane covered by a thin peptidoglycan layer. Beyond the peptidoglycan there is another outer membrane that is separated by the peptidoglycan by a gel-like periplasmic space. The outer leaflet of the outer membrane contains lipopolysaccharide. Since the outer membrane is much less permeable than the cytoplasmic membrane, porin proteins are placed through the membrane to allow nutrients to pass through.
What does the periplasmic space contain?
Enzymes for nutrient breakdown and substrate binding proteins, including PBPs
What connects the outer membrane to the peptidoglycan through the periplasmic space?
Lipoprotein
What is LPS comprised of?
What part is the endotoxin?
Lipopolysaccharide is comprised of Lipid A and O-antigen.
THe lipid A is a complex lipid that is covalently attached to a polysaccharide. This is the endotoxin and it’s extremely toxic to us.
THe lipid portion of LPS is attached to the outer membrane by hydrophobic bonds.
THe polysaccharide chain of releatin gunits is called the O antigen, which is exposed to the outside of the cell. THis is antigenic.
What is special about mycoplasma?
They are the smallest free-living organism. They DON”T HAVE A CELL WALL! The only barrier is the cytoplasmic membrane, but the membrane contains sterols required for growth (but aren’t synthesized by the bacterium)
They often cause walking pneumonia
Why can’t you visualized mycoplasma with gram stain?
THey don’t have a cell wall-no peptidoglycan
What is special about mycobacteria?
They contain mycolic acid in the cell wall, which prohibits gram staining. You have to use acid fast staining to visualize.
They contain small amounts of peptidoglycan and large amounts of glycolipids including LAM and mycolic acids which make the cell walls impermeable.
What does acid fast staining involve?
Staining with red carbolfuschin and then destaining with acid alcohol.
THe mycolic acid will hold onto the stain stronger than the alcohol could, so only acid fast bacteria will retain the stain after the decolorizing step.
What is a Protein Secretion System?
How many different types are there?
This is how a bacteria exchanges is proteins with the surrounding environment. They transport proteins or nucleic acids to the outside fo the cell, periplasm, or the inside of host cells (can transport adhesins or toxins)
There are 7 types (6 in gram negative and 7 in gram positive).
This plays a major role in determining a bacteria’s pathogenicity.
Some consist of transporters, outer membrane factors, and membrane fusion proteins, while others involves a transmembrane structur called an injectosome
What is an endospore?
An endospore is a version of a bacteria that is highly resistant to heat, desiccation and chemical changes.
They are produced by baccilus and clostridium species in nutrient limiting conditions and dehydration.
What is the structure of an endospore?
- Spore wall (exosporium) contains normal peptidoglycan and will ve the cell wall of the germinating bacterium
- SPore coat contains keratin-like protiens which are very impermeable to chemicals
- Cortex is the thickest part of the spore envelope and contains peptidoglycan with fewer cross-links
- The core cotains calcium dipicolinate (which is what confers the endospore with heat resistance) and all the nucleic acid for later growth
In general terms, what are the 2 types of viruses?
Viruses that infect prokaryotes = bacteriophage
Viruses that infect eukaryotes
What are the general characteristics of a virus?
- They are obligate intracellular parasites (need a host)
- The viral particle is either DNA or RNA (ds or ss) in a protein coat with or without a membrane
- THe outer coat protects the genetic material and facilitates adhesion and infection
- Contains almost no enzymes, no organelles or other biosynthetic machinery
- the nucleic acids code for proteins needed for viral replication
What is the difference between an enveloped virus and a naked virus?
Which is more durable in th environemtn?
They both have nucleic material with a coat ot capsid around it, but envelopes have an additional membrane that surrounds the capsid.
They acquire the membrane when they bud out from the host–so the membrane is basically a plasma membrane.
Naked viruses are more durable in the environment because the membrane of enveloped proteins can be broken down easily
What does the capsid do?
What is a subunit of capsid structure called?
What shapes can a capsid take?
It protects nucleic acids
A capsomere is a subunit of capsid structure
dapsid structures can be polyhedral, helical, isodecahedral, etc.
WHat is a virioid?
What do they usually cause disease in?
What human virus is similar to a viroid?
Viroids are very small single-stranded circles of RNA.
THey cause disease in plants
Hepetitis D is similar to a viroid
What is a prion?
A misfolded PrP protein (PrPsc) that can induce the same conformational change in other PrP proteins
Even though PrPc and PrPsc have the same protein sequence, they are shaped differently
The PrPsc is resistant to autoclaving, radiation, and nucleases
But they can be inactivated by detergents, urea, phenol, erc.
Examples include scarpies, Kurur, Creutsfeldt-Jakob disease, spongiform encephalopathy
A PrPsc protein will catalyze the formation of what in normal PrPc proteins?
They catalyze the formation of new beta sheets within the protein conformation
What is the big component of a fungi cell wall that can be used as a drug target?
Erogsterol
What are the three types of fungi?
What directly produce disease in humans?
Yeasts, molds, and mushrooms
Yeasts and molds can directly product disease in humans
Mushrooms cause disease indirectly by the toxins they produce
WHat are some characteristics of yeast?
Single celled fungi
Reproduce by budding
some strains produce psuedohyphae
What are some general characteristics of molds?
They grow in filamentous forms called hyphae
Many species produce cross walls of hyphae called septae (some nonseptate hyphae do exist)
Masses of hyphae are called mycelia
What does it mean for a fungi to be dimorphic?
What form is found in the body and which form is found in the enviroinment?
Dimorphic fungi can exist as a yeast or a mold form
The form is controlled by environmental conditions like temperature and nutrients
Yeast form is found in the body and the mold form is found in the environment (or lab culture)
What are three forms of fungal spores?
Conidia – asexual spores of molds
Arhtoconidia–formed from joints in hyphae and then fragmentation
Blastoconidia–yeast cell buds
What are protoza?
What forms can they take?
THey are single celled eukaryotes that can exist as trophozoites (motile form) and as cysts (resting stage).
Some move by flagella
What three types of worms can cause disease?
How does infection result?
Trematodes (flukes)
Cestodes (tapeworms)
Nematodes (roundworms)
Infection usually involves ingestion of larval or cyst form
