Bacterial Structure and Classification Flashcards
What are the two major shapes of bacteria?
Rods ( Bacilli ) and Spheres ( Cocci )
What are chains of Cocci?
What are pairs of Cocci ?
Grape like clusters of Cocci ?
Streptococci
Diplococci
Staphlococci
What are the major features that distinguish prokaryotes from Eukaryotes?
A nucleus and membrane bound organelles
What is the bacterial cell wall made of ?
Peptidoglycan- The cell wall in bacteria provides rigidity.
What are the major targets for antimicrobial therapy ?
The cell wall and its biosynthetic machinery
What is a way you can distinguish between Gram Positive and Gram negative bacteria?
The characteristics of the cell wall.
*Thick and heavily cross linked = Gram +
*Thin and lightly cross linked = Gram -
Do bacteria have sterols in their membranes?
No
What are some bacterial components that differ in bacteria and animals enough to be targets for antibiotic therapy?
Ribosomes ( smaller in bacteria )
RNA Polymerase
Topoisomerase
What is different in the cell membrane between gram + and gram - bacteria ?
The gram - bacteria have an extra layer in the cell membrane
Is the peptidoglycan layer external or internal to the cytoplasmic membrane?
The peptidoglycan layer is external to the cytoplasmic membrane
What are the two purposes of Pili ?
Sex Pili - are used to transfer genetic materal from one bacterium to another in conjugation,
Attach bacteria to the host surface.
What is the purpose of a flagella ?
Cell motility
What is a capsule ?
External structures composed of either polysaccharide or polypeptide that serve to protect and encapsulate bacteria from phagocytosis
What type of bacteria forms spores?
Gram positive rods can form spores in response to stress and nutrient limitation.
Other than pepditoglycan what other compounds compose the bacterial cell wall?
Teichoic acid and Lipoteichoic acid
How many layers deep is the gram negative bacterial cell wall?
Two
What space is found between the inner and outer bacterial cell walls?
Periplasmic space
What is the charge of the outer bacterial membrane and how does this help the bacteria to survive?
The outer membrane is negatively charged. This helps the bacteria evade phagocytosis, hinder antibiotic uptake, and avoid the action of complement.
How do nutrients pass through the outer membrane?
Porins are molecular sieves that allow substrates such as sugars to be transported across the membrane.
Does the periplasmic space contain any enzymes?
Yes, degrative enzymes will attempt to degrade antibiotics.
What molecule is unique to the outer membrane of gram (-) bacteria
Lipopolysaccharide (LPS) which is found in the outer leaflet of the membrane
What other molecules are contained in LPS?
3
Lipid A- recognized by the innate immune response to elicit a cytokine storm which leads to sepsis or septic shock
Endotoxin- a toxic phospholipid
O-Antigen- major surface antigen of gram negative bacteria.
Describe Type 1 secretion from bacteria.
In type 1 secretion proteins are secreted directly into the extracellular environment from the cytoplasm.
Can Type 1 secretion have any affect on antimicrobial drugs?
Yes, The antimicrobial drugs can be directly pumped out of the cell promoting drug resistance.
What type of bacteria have Type 1 Protein Secretion Systems ?
Gram ( + )
What type of bacteria have Type 2 Protein Secretion Systems ?
Gram ( - )
How does a type 2 Protein Secretion System work?
Proteins are first secreted into the periplasmic space then into the extracellular space.
Describe type 3 protein secretion systems.
Type 3 protein secretion systems acts like a molecular syringe becuase their structure allows for direct injection of toxins and other virulence factors into the cytosol.
What is peptidoglycan made up of?
Repeating disaccharides of N-Acetylmuramic acid and N-Acetylglucosamine
What are the repeating disaccharides of peptidoglycan linked via?
Transglycosylase
What bridges the sugar backbones of peptidoglycan?
Pentapeptide crosslinks formed by transpeptidases and carboxypeptidases.
What are penicillin binding proteins?
Transpeptidases.
What portion of nacetylmuramic acid pentapeptides contain a target for antimicrobials?
Terminal D-Alanine Pair which is critical for cross-linking of the bacterial cell wall.
What common antibiotic targets the terminal alanine pair?
Vancomycin
Where is the bacterial cell wall assembled?
In the cytoplasm
What is a natural defence that targets the bacterial cell wall?
Lysozyme which is present in tears, saliva, and in the lysosomes of phagocytic cells
What will offer the bacteria antibiotic resistance to vancomycin?
Vancomycin resistance occurs when D-Alanine D- Lactone is synthesized.
What are the two types of bacteria that do not stain using the gram stain method?
Mycoplasma and Chlamydia
What composes the cell wall of mycobacterium?
A waxy coat of mycolic acid.
What happens to anaerobic bacteria in the presence of oxygen?
They get killed.
What type are the majority of pathogens?
Facultative anaerobes
What kind of bacteria can grow in the absence of oxygen?
Microaerophilic
What is a useful technique to classify Fermentative bacteria?
The end products of fermentation.
What can be used to determine the major pathogenic members of the Streptococcus species?
Lancefield Antigen which is commonly referred to as the GAS antigen
How can you distinguish between different strains within a genus of bacteria ?
Serotyping
