Lecture 1: Bacterial Morphology and Structure 1 Flashcards
What are the two most common shapes of bacteria
- Coccus- sphere/round
- Bacillus- rod
What are 4 other common shapes of bacteria
- Coccobacillus- short rod
- Vibrio- comma shape
- Spirochete- flexible, thin spiral-shaped rod
- Spirillum- rigid, spiral-shaped rod
What does it mean if a bacteria is pleomorphic
Has no defined shape, variety of shapes in one species
Identify bacteria shapes 1-6
- Coccus
- Bacillus
- Coccobacillus
- Vibrio
- Spirillium
- Spirochete
What is the prefix of bacteria that divides in one plan in a pair
Diplo
What is the prefix of bacteria that divides in one plain in a chain
Strepto
What is the prefix of a bacteria that divides in 2 planes in a grape like cluster
Staphylo
What is the prefix of a bacteria that divides in 2 planes in a packet of 4 cells
Tetrads
What is the prefix of a bacteria that divides in 2 planes in packets of 8 cells
Sarcina
Identify bacteria based on arrangement and shape
Diplococcus
Identify the bacteria based on arrangement and shape
Streptococcus
what is the arrangement of this bacteria
Staphylo
What is the arrangement of this bacteria
Tetrad
What is the arrangement of this bacteria
Sarcina
What are the functions of the bacterial cytoplasmic membrane
Permeability and transport, site of electron transport chain, excrete toxins, chemotaxis
What are 2 examples of bacteria genera without cell walls
- Mycoplasma
- Ureaplasma
What are the three main types of cell walls
- Gram negative
- Gram positive
- Acid fast
In order from left to right identify the types of bacterial cell walls
left: gram negative
Middle: gram positive
Right: acid fast
What are the 2 main components all three cell walls have
- Peptidoglycan
- lipoproteins
What is the function of peptidoglycan and lipoproteins
Structural support
What 3 parts make up the peptidoglycan layer
- Backbone: NAG-NAM segments
- Set of tetrapeptide chains
- Set of peptide cross bridges
Why is peptidoglycan clinically relevant when treating a bacterial infection
Can target peptidoglycan layer as it is crucial to cell support, damage it and cell wall loses integrity and can lyse
What enzyme is found in secretions and can weaken the cell integrity by damaging peptidoglycan layer
Lysozymes
Gram positive or gram negative: thick peptidoglycan layer
Gram positive
What color does gram positive bacteria stain
Purple
Gram positive or gram negative: thin peptidoglycan layer
Gram negative
What color does gram negative bacteria stain
Red
What is the primary stain in a gram stain
Crystal violet
What is the counter stain in gram stains
Safranin (red)
What is the periplasmic space and is it typical of gram positive or negative
Found in gram negative
Space between inner and outer membranes
What does periplasmic space contain
- Thin peptidoglycan layer
- Binding proteins
- Transport proteins
- Hydrolytic enzymes
What is the outer membrane and is it specific to gram negative or positive
Specific to gram negative
Bilayered structure: inner layer: resembles cytoplasmic membrane, outer membrane: contains phospholipids and LPS
What is the distinct component on the outer membrane of a gram negative bacteria
LPS
What is the function of the outer membrane
Protective permeability barrier to large molecules and hydrophobic molecules, impedes phagocytic destruction
What are the 3 components of LPS
- O-antigen
- Core polysaccharide
- Lipid A
What is/ what is the function the O- antigen
Outermost portion of LPS, serves as attachment sites, inhibits phagocytosis, can identify strains
What is/the function of the core polysaccharide
Attaches O-Antigen to Lipid A
What is/the function of Lipid A
Virulence factor/toxin of LPS—> endotoxin that produces cytokines and inflammatory mediators that can lead to endotoxic shock
Which component of the LPS is responsible for endotoxic shock
Lipid A
Why are endotoxins clinically relevant in horses
Leading cause of equine death—> major part of GI disorders like colic and neonatal foal septicemia
Why are endotoxins clinically relevant in cattle
Play significant role in laminitis and abomasal displacement
Which bacterial cell wall has trimeric porins
Gram negative
What is the function of a porin
Transport of solutes
What are the two components only found in gram positive bacteria
- Teichoic acid (WTA)
- Lipoteichoic acid (LTA)
Where is teichoic acid anchored to
Peptidoglycan
Where is lipoteichoic acid anchored to
Cell membrane
What is the function of teichoic and lipoteichoic acid
Adherence to cell host, serves as a virulence factor and can initiate endotoxin like behavior
Gram negative or gram positive: release endotoxins
Gram negative (gram positive can have endotoxin like effects but has no LPS so not endotoxin)
What structure is specific to outer layer of acid fast bacteria cell walls
Mycolic acid layer
What does the mycolic acid layer consist of
Long fatty acid chains and lipids that give waxy coat
How are mycolic acids connected to peptidoglycan layer
Via arabinogalactan
What is the function of mycolic acid layer
Provides resistance to dessiccation and some antibiotics, inhibits phagocytosis
What bacterial cell wall has tetrameric porins
Acids fast bacteria
What are two clinically relevant genera that are acid fast
- Mycobacterium
- Nocardia
What is the primary stain in acid fast
Carbolfuschin (acid fast-red)
What is the counter stain in acid fast
Methylene blue (nonacid-blue)
What are the steps in acid fast staining
- Primary stain-carbolfuschin (acid fast-red)
- Heat
- Acid-alcohol wash-depolarization
- Counterstain- methylene blue (non-acid fast)
In this acid fast stain, what is A and B, and which one is acid fast bacteria
A. Staphylococcus (grape like clusters, round)
B. Mycobacterium- acid fast- red
A stained tracheal mucus specimen collected from a cattle shows acid fast bacilli. Which of the following genera should be included in your differential diagnosis:
A. Clostridium
B. Bacillus
C. Staphylococcus
D. Mycobacterium
D. Mycobacterium
A foal was diagnosed with endotoxemia caused by endotoxins released into bloodstream. The bacterial cell wall structure causing the patients symptom is which of the following:
A. Lipid A
B. O antigen
C. Teichoic acid
D. Lipoprotein
A. Lipid A
Gram negative or positive: sensitive to penicillin
Gram positive more susceptible
Gram negative or positive: sensitivity to lysozymes
Gram positive yes