(01) Bacterial Struct And Class Flashcards
What are the two major shapes of bacteria?
- Bacilli (rods)
- Spheres (cocci)
Define each of the following arrangements.
- Strepto-
- Diplo-
- Staphylo-
Strepto = Chains Diplo = Pairs Staphylo = Grape-like Clusters
What are the most common infectious agents?
Staphylococci
What are group of bacteria is:
- comma shaped
- spiral shaped
comma = vibrio Spiral = Spirilli
Cell walls:
- Bacteria
- Animals
- Plants
- Fungi
Bacteria - Peptidoglycan
Animals - NONE
Plants - Cellulose
Fungi - Chitin
Bacterial Peptidoglycan Cell wall:
- Role in Pharm.
- Structural Role
- Classification
Pharm:
- Difference in Prokaryotes and Eukaryotes makes it an important target
Structural Role:
- Provides Rigidity
Classification:
- Gram +
- Gram -
What is the difference between a Gram + and Gram - cell wall?
Gram +
- Thick and heavily cross-linked
Gram -
- Thin and lightly cross-linked
What are the roles of Pili?
Disease:
- Attach the Bacteria to the Host Cell surface
Sex:
- Sex Pilus allows for transmission of genetic material during conjugation
Capsules:
- Job
- Presence
- Common in which disease?
- ink
Job:
- Protect Encapsulated Bacteria From Phagocytosis
Presence:
- NOT present in all bacteria
Disease:
- Meningitis is often caused by capsulized bacteria
Ink:
- Often excludes ink such as India ink
Spores
- formed by which type?
- Formed when?
- Purpose?
Bacteria:
Gram + rods
When:
- Times of Stress, nutrient limitation
Purpose :
- Dehydrated and dormant, allowing potential pathogens to survive for a VERY long time
Gram + Cell Wall:
- Thickness
- Cross-linking
- Major Components
- Roles of Components
Thickness:
> 40 Layers
Cross-linking:
- Lots
Major Components:
- Peptidoglycan
- Teichoic Acid (endotoxic effects?)
- Lipoteichoic Acid (endotoxic effects?)
What are Teichoic Acid and Lipoteichoic Acid?
Polymers of Glycerol Phosphate and Ribitol Phosphate
What is the major barrier to the environment in both Gram Positive and Gram Negative Bacteria?
Cytoplasmic Membrane
Gram - Cell Wall:
- Thickness
- Number of Lipid Membranes
- Peptidoglycan location
Thickness:
- 2 layers of Peptidoglycan Thick
Number of Lipid Membranes:
- 2
PG Location:
- BETWEEN two lipid membranes (in periplasm)
Outer Membrane:
- Charge
- Purpose of Charge
- Unique Proteins
- Porins
Outer Membrane Serves as an additional Permeability Barrier
Charge:
- Outer Membrane = NEGATIVE
Purpose of Charge:
- Evade Phagocytosis
- Hinder Antibiotic Uptake
- Avoid the action of Complement
Unique Protein:
- Lipopolysaccharide (LPS)
Porins:
- Allow Substrates to enter the periplasm
T or F: the Periplasm contains many degradative proteins.
True, these help to degrade antibiotics
What are the components of LPS?
- purpose of each
- Lipid A (endotoxin)
- toxic phospholipid - Core Polysaccharide
- O Antigen
- Major Surface antigen of Gram - bacteria
Lipid A and Septic Shock
Recognized by innate immune system and elicits CYTOKINE STORM causing septic shock
Gram (-) Type I Protein Secretion System.
- Transporter Type
- From Where, To Where?
- Other imp. features
- Type of Bacteria with it?
Transporter:
- ABC (ATP Binding Cassette)
From and To:
- Pumps from CYTOPLASM directly to EXTRACELLULAR SPACE
Important:
- Allows drugs to be pumped out leading to DRUG RESISTANCE
ALL GRAM (-) Bacteria
Gram (-) Type II Protein Secretion System.
- Purpose
- From Where, To Where?
- Type of Bacteria with it?
Purpose:
- General Secretory Pathway
From and To:
- From CYTOPLAM to PERIPLASM then to extracellular space
ALL GRAM (-) Bacteria
Gram (-) Type III Protein Secretion System.
- Purpose
- From Where, To Where?
- Type of Bacteria with it?
Purpose:
- Pathogenesis, DIRECT INJECTION of toxins
From and To:
Hydrophobic protein spans from CYTOPLASM of bacteria into CYTOPLASM of animal (crosses 3 membranes total)
ONLY PATHOGENIC GRAM (-) BACTERIA HAVE THIS
4 steps of Gram Staining
- Crystal Violet (color)
- Gram Iodine (fixes color)
- Decolorizer (EtOH or Acetone)
- color lost in gram (-) cells - Safarin Red
- colors gram (-) cells, gram (+) cells remain purple
What is formed by removal of cell walls from bacteria?
- what happens to these?
- Protoplast = bacteria w/o cell wall
- Bacterial Cell Lyses happens
**This is why cell walls are an important target
Peptidoglycan
- Disaccharides and arrangement
- Linking Enzyme
- Repeating NAM (N-acetylmuramic acid) and NAG (N-acetylglucosamine)
- Transglycoslyase = linking enzyme
Pentapeptides
- linkage to sugar
- linkage to other pentapeptides
- enzyme?
Pentapeptides linked to the NAM (N-acetylmuramic acid) of the peptidoglycan
Pentapeptides link to other pentapetides to form interstrand crosslinks
Enzyme for Crosslinking:
- Transpeptidases and Carboxypeptidases (aka penicillin binding proteins)
What is the difference in crosslinking between Gram (-) and Gram (+) bacteria?
In gram (+) bacteria a PENTAGLYCINE interpeptide lins the polypeptides
What is found at the terminal end of NAM-pentapeptides?
- purpose
- removed by?
Terminal D-alanine
Purpose:
- Critical to Cross-linking Process
Removed by:
Carboxypeptidases
***Target for antimicrobials
What do Cycloserine and Vancomycin affect?
- how do they differ?
- The D-alanine at the terminal end of the pentapeptides
Cycloserine - inhibits their incorporation into the pentapeptide
Vancomycin - masks their availability for crosslinking
Cell Wall Assembly (4 steps)
- NAM and NAG are made into a disaccharide IN CYTOPLASM
- NAM-NAG is linked to Lipid Carrier via Diphosphate bond IN CYTOPLASM
- NAM-NAG added to growing Peptidoglycan chain after being carried across membrane by Lipid carrier
- Lipid carrier dephosphorlyated and returns to inner leaflet
How do the following affect cell wall assembly?
- Lysozyme
- Bacitracin
Lysozyme:
- Cleaves NAM-NAG bond
Bacitracin:
- Prevents dephosphorylation of disphosphate from lipid carrier so it cannot be recycled
Where can lysozyme be found?
- Tears
- Saliva
- Lysosomes of Phagocytotic cells
ß-lactam
- resembles
- Bound by
- Job
Resembles:
D-alanine D-alanine terminal pair
Bound By:
Traspeptidases (penicillin-binding proteins)
What are examples of ß-lactams?
- PENICILLIN
- Cephalosporins
- Carbapenems
- monobactams
What is the difference between the action of ß-lactams and drugs like vancomycin?
Vancomycin bind D-alanine D-alanine while ITS STILL ATTACHED TO ITS LIPID CARRIER
What enzymes allow for resistance to be conferred against ß-lactams?
- ß-lactamases
2. Mutated Transpeptidases that no longer bind ß-lactams
How does Vancomycin resistance occur?
D-alanine D-lactone is synthesized
- D-alanine D-lactone is not recognized by vacomycin but can still by linked by transpeptidases
- *What is required for ß-lactams to work?
- why?
CELL GROWTH
- Growing Cells have AUTOLYSINS that cleave sugars for new subunit insertion
- ß-lactams inhibit new cross-links from forming and the cell LYSES
What are three notable examples that cannot be stained by gram stain?
- Why doesn’t gram stain work?
- what diseases are caused by these?
- Mycoplasma
- Lack a Cell wall
- cause an atypical pneumonia in humans - Chlamydia
- Lack Peptidoglycan
- Pneumonia, Blindness, Genital infections - Mycobacterium
- Waxy Coat containing Mycolic Acid
- TB and Leprosy
How are Mycobacterium cells stained?
- Carbol Fuchsin penetrates the waxy coat to enter the cells
- Cells are washed using acid-alcohol (acid-alcohol destains Gram organisms)
**These cells are call ACID-FAST
What are:
- aerobes
- anaerobes
- facultative anaerobes
**which account for the majority of pathogens?
Aerobes:
- need O2 to live
Anaerobes:
- Killed in the Presence of O2
Facultative Anaerobes:
- LIVE IN BOTH ENVIROMENTS
***MOST PATHOGENS ARE FACULTATIVE ANAEROBES
What type of bacteria grows in the absence of oxygen but grow optimally at low O2 concentration?
Microaerophilic bacteria
What 8 factors are used to classify bacteria?
- Morphology
- Arrangement
- Staining Properties
- Growth Properties
- Fermentation Properties
- Other Enzymatic and Virulence properties
- Antigenicity
- Genotype
What is Serotyping?
- Looking at the antigens on a given bacteria
What bacteria type is associated with the Lancefield Antigen?
Streptococcus
What method would you use to distinguish between the strains of a genus?
- why would you want to do this?
Serotyping
- helps determine the SOURCE and SEVERITY of the infections
Escherichia Coli O157:H7
- disease?
- what does each part mean?
Causes Diarrheal outbreaks
Escherichia = genus Coli = species O157 = O-antigen on LIPOPOLYSACCHARIDE of the strain H7 = H antigen found on the Flagella of the strain
What is the most common method used to Genotype a bacteria?
- when would this be used?
RFLP (restriction fragment length polymorphism)
- digest the genome to get specific fragment of different lengths
- Use this during outbreaks
