Microbiology Strx and Fnxn

Question 1

What is a microbe?

Answer 1

Bacteria (prokaryote)
Protozoa (eukaryote)
Fungi (eukaryote)
Viruses (neither prokaryotic nor eukaryotic)

Question 2

Prokaryote

Question 3

Bacterial Strx

Answer 3

Two basic shapes:
Rod
Cocci
Other shapes:
Spirochetes
Spirillum
Diplococci
Diplobacilli

Note HOW they grow, too

Question 4

Bacterial Strx ctd.

Answer 4

Rods
Aka “bacillus”
Two bacilli together – Diplobacilli
Chains of bacilli are called streptobacilli
Other arrangements are called “palisades”
Side by side/ “X” “V” or “Y” figures
Cocci
Spirochete: Flexible undulating corkscrew
Spirillum: RIGID corkscrew shape

Question 5

Bacterial Strx properties

Answer 5

Inner workings
Flagella and pili (fimbriae)
Capsule
Cytoplasmic membrane
Cell envelope
Gram positive
Gram negative
The Gram stain

Question 6

Cocci

Answer 6

cocci in chains = streptococci

Question 7

Rods

Answer 7

Two bacilli together – Diplobacilli

Question 8

Spirochetes

Answer 8

Flexible undulating corkscrew

Question 9

Mesosome

Answer 9

Chromosomal DNA attached to the bacterial membrane invaginated at the site of bacterial division. CONTROVERSIAL.

Question 10

Plasmid DNA

Answer 10

A self-replicating unit of DNA distinct from the chromosome.

Frequently give pathogenic or antimicrobial resistant features to bacteria. SOME ARE MOBILE (usually w/in species, but not always)

Question 11

Ribosomes and Granules

Answer 11

Question 12

PK locomotion

Answer 12

Flagella & pilli

Whatever is external on bacteria is HIGHLY ANTIGENIC

Flagella -some have >1.
Used by bacteria for locomotion.
Composed of flagellin.
Different arrangements of flagella:
Monotrichous (Vibrio cholerae)
Lophotrichous (Bartonella bacilliformis)
Amphitrichous (Spirillum serpens)
Peritrichous (Escherichia coli)

Question 13

Recognition of flagella helps determine which antimicrobial to use

Answer 13

Salmonella with a Peritrichous Arrangement of Flagella:

Question 14

The Flagellar Motor

Answer 14

Made of the protein flagellin and consists of a filament and basal region. The basal region has a hook and a basal body which has a rod and rings. Gram positive organisms have 2 rings, one in the cell wall and one in the cell membrane. Gram negative organisms have 4 rings, 2 in the cell wall and 2 in the cell membrane.

Question 15

Pili (Fimbriae)

Answer 15

Shorter and finer than flagella.
Two types:
Adherence pili – attach bacteria to surfaces.
Sex pili – important in bacterial conjugation; found in some gram negative bacteria.

Important aspects of bacterial pathogenesis (attachment)

Question 16

The Capsule

Answer 16

Some have these. Those that can…

A slimy outer coating not found in all bacteria.
Usually a complex of high molecular weight polysaccharides.
A.k.a. Slime or glycocalyx (generally more loosely associated – adherence properties).
Special Note: BIOFILMS.
Can be antiphagocytic - resistant to macrophage cells that would try to engulf it.

Question 17

Cytoplasmic membrane

Answer 17

Encloses the bacterial cytoplasm
Phospholipid bilayer – selectively permeable.
Imbedded with proteins.
Site of nutrient transport.

Peptidoglycan - b/c unique to bacteria, common antibiotic target
60-90% of gram positive cell wall, much less in gram negatives.

Question 18

Peptidogycan

Answer 18

Attached to common monomers (NAM-NAG) in some bacteria is a unique tetrapeptide

Penicllin inhibits this cross-linking so much osmotic pressure cell lyses

Question 19

Gram Positive and Gram Negative Bacterial Cell Envelopes

Answer 19

GRAM+ : lots of peptidoglycan; GRAM – have much less. Hence, much more difficult to transport stuff (antibiotics) into GRAM-’s

Question 20

The Gram Stain

Answer 20

The gram stain procedure was originally developed by the Danish physician Hans Christian Gram (no kidding) to differentiate pneumococci (Streptococcus pneumoniae) from Klebsiella pneumoniae.

The difference between gram-positive and gram-negative bacteria is in the permeability of the cell wall to “purple colored iodine-dye complexes” when treated with the decolorizing solvent.

Gram-positive bacteria retain purple iodine-dye complexes after the treatment with the decolorizing agent, gram-negative bacteria do not retain complexes when decolorized. Safranin is used after decolorization treatment to “counterstain” gram-negatives.

Question 21

Gram Stain Process

Answer 21

Works due to diff in peptidoglycan in bacterial cell walls

Bacteria are heat fixed to a slide.

Crystal violet is added – all cells stain blue.

Iodine fixes the stain into the bacterial cell.

Alcohol decolorizes gram negative bacteria. Gram positives remain blue/purple.

Safranin (counterstain) stains the gram negative bacteria a pink color.

Question 22

Gram Positives

Answer 22

Found only in the gram + cell wall are:

• Teichoic acids / Teichuronic acids*
• Lipoteichoic acid (LTA)*
• Polysaccharides*

Teichoic Acid.
A water soluble polymer of ribitol or glycerol residues joined by phosphodiester linkages.
Teichuronic Acid.
Similar to teichoic acid, but made in phosphate-limiting conditions.

Lipoteichoic Acid (LTA).
Lipid attached to Teichoic Acid – Adhesin!
Polysaccharides.
Most likely composites of sugars released from teichoic and teichuronic acid.

Question 23

Gram Negatives

Answer 23

Found only in the gram negative cell wall are:
Lipoproteins
Periplasmic space
Outer membrane
Lipopolysaccharide

Periplasmic space
A gel-like matrix between the cytoplasmic membrane and the outer membrane
Contains enzymes for nutrient breakdown and substrate binding proteins, including penicillin binding proteins.
Lipoprotein
Cross-links outer membrane to peptidoglycan
In the periplasmic space

Outer Membrane

A phospholipid bilayer containing lipopolysaccharides (later)
 Contains porins (non-specific pore proteins), anchor proteins and transport proteins.
 Protects the cell from hydrolytic enzymes.

Lipopolysaccharide (LPS)
Made of Lipid A (a complex lipid) covalently attached to a polysaccharide with core and terminal repeat units.
LPS (Lipid A) = endotoxin. It is extremely toxic to animals.
The lipid portion of LPS is attached to the outer membrane by hydrophobic bonds.
The polysaccharide chain of repeating units is called the O-antigen, is exposed to the outside of the cell, and is antigenic.

Question 24

The Mycoplasma (and Ureaplasma)

Answer 24

_{The smallest free-living organisms.}
NO CELL WALL!
That means no peptidoglycan.
Bacterial stains don’t work well.
The only barrier is the cytoplasmic membrane.
Membranes contain sterols – required for growth (not synthesized by the bacterium).

Many mycoplasmal pathogens exhibit filamentous or flask-shaped appearances and display prominent and specialized polar tip organelles that mediate attachment to host target cells.

Question 25

Acid fast bacteria

Answer 25

Mycobacteria (and Nocardia).
Contain small amounts of peptidoglycan.
Contain large amounts of glycolipids.
Lipoarabinomannan (LAM).
Mycolic acids (60% of the cell wall).
Make the cell walls impermeable.

DONT have lipid A (endotoxin)

Acid fast stain, not gram stain, will reveal if this is culprit

Question 26

Acid fast staining involves staining with red carbolfuchsin and destaining with acid alcohol. Only acid-fast bacteria will retain the stain after the decolorizing step.

Answer 26

Question 27

Bacterial Structure Protein Secretion Systems

Answer 27

Gram negatives have six classes; Gram positives have an additional class
 Play a major role in bacteria interacting with their enviroment and helping to deterimine their pathogenicity.

Structure – There are some simple systems like T1SS that consist of transporters, outer membrane factors, and membrane fusion proteins; while others (T3SS, T4SS, and T6SS) involve a transmembrane structure (injectosome) which consists of more than 25 proteins.

Genes determine which secretion system.

Inject these secretions into other cells

Question 28

Protein Secretion Systems

Answer 28

Functions
- Transport proteins or nucleic acids (T4SS) to the outside of the cell, periplasm, or inside host cells.
Transported proteins can be surface proteins like adhesins or toxins which modify host cell physiology causing pathological consequences.

Learn which species have secretion systems

Question 29

Endospores

Answer 29

Made by Bacillus and Clostridium (makes heat-resistant) species in nutrient-limiting conditions (i.e. starvation).
-Highly resistant to heat, desiccation, and chemical damage (innate to spore, not bacteria).
-Reasons for heat resistance:
Dehydration.
Calcium dipicolinate in the core (5-15% of the spore dry weight).

Question 30

Endospore Formation

Answer 30

Spore Wall (Exosporium): Contains normal peptidoglycan. Will be the cell wall of the germinating bacterium.

• *Spore Coat**: Contains keratin-like proteins, very impermeable to chemicals.
• *Cortex**: The thickest part of the spore envelope – contains peptidoglycan with fewer cross-links.
• *Core**: Contains the calcium dipicolinate, and all of the nucleic acid for later growth.**

Question 31

Viruses

Answer 31

There are 2 types of viruses:
Procaryotic viruses = Bacteriophage (upon entering, do NOT lyse cell)
Eukaryotic viruses, e.g. Animal viruses

General characteristics
Obligate intracellular parasites (need a host!)
The viral particle is DNA or RNA in a protein coat with or without a membrane
The outer coat protects the genetic material and facilitates adhesion/infection
Contains few, if any enzymes, organelles or other biosynthetic machinery.
The nucleic acids code for proteins needed for viral replication.

Question 32

Special Topics, Viruses

Answer 32

Enveloped Viruses:
Acquire membrane from the host.
Naked capsid viruses:
Consist of the nucleic material with a coat or capsid. …more easily transmitted.

Question 33

Virues, ctd.

Answer 33

Viral structures/nomenclature to know:
Envelope
From host
Nucleocapsid/Capsid
Protects nucleic acids (DNA or RNA)
Capsomere
Subunit of the capsid structure.
Polyhedral/Helical
Different Capsid structures.

Question 34

Viroids

Answer 34

Very small single-stranded circles of RNA (300-400 nucleotides).

• Cause disease in plants.
• Replication strategy unknown – probably replicate through host RNA polymerase.
• HDV is similar to a viroid.

Hepatitis D is similar to a viroid

Question 35

Prions

Answer 35

Cause “slow virus disease”
E.g.s: Scrapie, Kuru, Creutzfeldt-Jakob disease, and “Mad Cow” disease. These diseases are subacute spongiform encephalopathies
Resistant to heat inactivation (autoclaving), radiation damage, and nucleases, e.g., DNAses and RNAses (They contain no nucleic acid)
Can be inactivated by detergents, urea, phenol, etc.
Causative agent is the prion protein: PrPSC

Question 36

Prions ctd

Answer 36

Kuru: Human disease in cannibals in Papua New Guinea:

Mad Cow Disease (BSE):
A very real, serious problem is vCJD
For people, there’s CJD from an unknown source and vCJD – thought to be a variant form of BSE infectious for people.

PrPSC has the same protein sequence as a normal cellular protein PrPC.
The cellular protein and the prion protein have different folded conformations.
The PrPC protein is found in normal tissue and is degraded by proteases.
The PrPSC protein is NOT degraded by proteases.

Question 37

Prions ctd

Answer 37

The normal protein is on the left (note alpha helices) and the prion protein is on the right. The prion protein catalyzes formation of itself!

Question 38

Fungi

Answer 38

General Characteristics
Eukaryotic organisms
Have cell walls for protection
Ergosterol is the dominwnt membrane sterol rather than cholesterol (impt. for therapy)
Require preformed organic compounds for growth

Question 39

Fungi ctd

Answer 39

There are three types of fungi: yeasts, molds, and mushrooms
Some yeasts and molds produce disease

Question 40

Yeasts

Answer 40

Yeasts
Single cell fungi
Reproduce by budding (blastoconidia)
Some strains (Candida) produce pseudohyphae

Question 41

Molds

Answer 41

Molds
Grow in filamentous forms called hyphae
Many species produce cross walls of hyphae called septae
Nonseptate hyphae do exsist
Masses of hyphae are called mycelia

Question 42

Dimorphic Fungi

Answer 42

Exist as yeast or yeast-like forms and filamentous forms
Form is controlled by the enviromental conditions like temperature and nutrients
Yeast form found in the body and filamentous form in the enviroment ex. Lab culture

Question 43

Fungi spores

Answer 43

Spores
Conidia are asexual spores of molds
Arthroconidia are formed from joints in hyphae then fragmentation
Blastoconidia are yeast cell buds
Are of diagnostic value for the identification of some fungi ex, “barrel-shaped” arthrospore of Coccidiodes immitis

Question 44

Parasitology

Answer 44

Protozoa
Single cells
Exists as trophozoites (motile form) and cysts (resting stage)
Some move by flagella ex. Giardia and some by cilia ex. Balantidum

Worms
Trematodes (flukes), cestodes (tapeworms),and nematodes (roundworms) cause disease
Infection usually involves ingestion of larval or cyst forms

Question 45

Chains of bacilli are called:

Answer 45

streptobacilli

Question 46

Palisades of bacilli

Answer 46

Other arrangements are called “palisades”
Side by side/ “X” “V” or “Y” figures

Question 47

Spirillum

Answer 47

RIGID corkscrew shape