2-Bacterial Classification

Question 1

What is serotyping?

Answer 1

can distinguish a particular strain of bacteria with the use of Ab’s which detect characteristic antigens on the bacteria.

Question 2

When is serotyping used?

Answer 2

Typically used to identify organisms that are either to dangerous or to difficult to grow in the lab, associated with specific disease syndromes, or need to be identified rapidly.

Question 3

What is biotyping?

Answer 3

Biochemical testing, certain tests go with certain organisms. Connect what tests go with what organism. Catalase, coagulase, indole, etc.

Question 4

What is DNA hybridization?

Answer 4

When DNA is heated to denaturation temperatures to form single strands and then cooled double helices will re-form (renaturation) at regions of sequence complementarity. This technique is useful for determining sequence similarity among DNAs of different origin and the amount of sequence repetition within one DNA.

Question 5

When is DNA hybridization used?

Answer 5

Most commonly used for the analysis of sequences of ribosomal DNA to detect the highly conserved sequences of ribosomal DNA (identify a family or genus) and highly variable sequences (identify a family or genus)

Question 6

What is the gram staining process?

Answer 6

Process: Bacteria Heat Fixed –> Stained with Crystal Violet –> Stained with Iodine –> Unbound and excess stain with washed away with Decolorizer (acetone based) and Water –> Stain with Safranin (Red Counterstain; added to stain any decolorized cells)

Question 7

What bacterial cannot be classified by gram staining?

Answer 7

• Mycobacteria and mycoplasms cannot be classified by gram stain

Question 8

What is the coccus shape?

Answer 8

a spherical-shaped bacterium. Many species of bacteria have characteristic arrangements that are useful in identification. Pairs of cocci are called diplococci; rows or chains of such cells are called streptococci; grapelike clusters of cells, staphylococci; packets of eight or more cells, sarcinae; and groups of four cells in a square arrangement, tetrads. These characteristic groupings occur as a result of variations in the reproduction process in bacteria

Question 9

What is an example of a coccus bacteria?

Answer 9

staphylococcus aureus

Question 10

What is the bacillus shape?

Answer 10

cylindrical or rodlike bacteria

Question 11

What is an example of a bacillus bacteria?

Answer 11

B. anthracis

Question 12

What is the spirillum shape?

Answer 12

Curved shaped bacteria

Question 13

What is an example of a spirillum bacteria?

Answer 13

spirillum minus

Question 14

What is the branched filamentous shape?

Answer 14

look like little filaments; often appear beaded when staining

Question 15

What is an example of the branched filamentous shape?

Answer 15

candidatus savagella

Question 16

What is the diplococcus shape?

Answer 16

paired spherical bacteria, including those of the genus Diplococcus, some of which are pathogenic

Question 17

What is an example of a diplococcus bacteria?

Answer 17

neisseria meningitidis

Question 18

What is the pleomorphic shape?

Answer 18

Different morphological forms of same species or strain. Changes within natural environment

Question 19

What is an example of a pleomorphic bacteria?

Answer 19

diphtheroids, Corynebacterium sp

Question 20

What is the cell wall of the gram + bacteria look like?

Answer 20

thick, multilayered cell wall consisting mainly of peptidoglycan surrounding the cell membrane. There is not outer membrane and therefore no hydrophobic barrier.

Question 21

What are the 2 layers of the gram (-) bacteria?

Answer 21

1) Thin Peptidoglycan layer- makes up 5-10% of the cell wall by weight, no teichoic or lipoteichoic acids. 2) Outer membrane has lipopolysaccharides, access through this outer membrane is through porins. It maintains the bacterial structure and is a permeability barrier to large molecules and hydrophobic molecules. It also provides protection.

Question 22

What is teichoic acid?

Answer 22

water-soluble polymers, containing a ribitol or glycerol residue linked by phosphodiester bonds; found in cell walls and is chemically bonded to peptidoglycan. Essential to cell viability and important factor in virulence.

Question 23

What is lipoteichoic acid?

Answer 23

found in cell membrane and is chemically bonded to membrane glycolipid (fatty acid), particularly in mesosome. Anchored into the cytoplasmic membrane, these surface antigens are used to distinguish bacterial serotypes and promote attachment to other bacteria and to specific receptors on mammalian cell surfaces (adherence). When these antigens are shed initiate innate protective responses similar to endotoxin.

Question 24

Where is teichoic and lipoteichoic acid found?

Answer 24

Gram + bacteria

Question 25

What cells have the periplasmic space?

Answer 25

Gram (-) cells

Question 26

What is the periplasmic space?

Answer 26

an area between the external surface of the cytoplasmic membrane and the internal surface of the outer membrane is referred to as the periplasmic space, this is where many of the virulence factors (collagenases, hyaluronidases, proteases, and β-lactamases) are located.

Question 27

What cells have the LPS endotoxin?

Answer 27

Gram (-) cells

Question 28

What is the LPS endotoxin?

Answer 28

found on the out leaflet of the outer membrane of Gram- negative cells. Consists of lipid A and a polysaccharide composed of a core and terminal repeating units. The LPS is negatively charged and non-covalently cross-bridged by divalent cations. The LPS serves as an endotoxin (powerful stimulator of the immune system); it is shed from the bacteria into the media and host. The toxicity is associated with the lipid A. It also contains major surface antigenic determinants, including O antigen found in the polysaccharide component.

Question 29

What type of cells have porins?

Answer 29

Gram (-) cells

Question 30

What are porins?

Answer 30

In Gram – there are proteins that traverse the lipid bilayer and thus they are transmembrane proteins, they allow the diffusion of hydrophilic molecules (metabolites and hydrophilic antibiotics)

Question 31

What is the structure of the peptidoglycan layer in gram + bacteria?

Answer 31

highly cross-linked, multilayered (usually thick) peptidoglycan cell wall that traps large crystal violet-iodine complex

Question 32

What is the structure of the peptidoglycan layer in gram (-) bacteria?

Answer 32

thin (1-3 layers) of peptidoglycan layer linked to an outer membrane; the peptidoglycan is not highly cross-linked, so it easily loses the gram crystal violet/iodine dye complex on decolorization with alcohol

Question 33

What are pili?

Answer 33

rigid hairlike surface appendages composed mainly of a protein called pilin; typically are small and not coiled in structure. Promotes adherence (adhesins) to other bacteria or to the host and are involved in attachment of donor and recipient bacteria in G- cell conjugation (sex pili; F pili)

Question 34

What are capsules?

Answer 34

a loose polysaccharide (sticky) or protein layer found in G+ and G- bacteria. The capsule is very important for survival in the host, it is poorly antigenic and antiphagocytic and is a major virulence factor. It also has several other functions: Adherence , Prevent dehydration, Nutrient source, Avoid phagocytosis. Some bacteria will produce a polysaccharide biofilm which establishes a community of microorganisms and protects them from antibiotics and host defenses (ex: tooth plaque).

Question 35

What are flagella?

Answer 35

one or more ropelike protein appendages for locomotion and contain prominent antigenic determination. Composed of helically coiled protein subunits (flagellin) that are anchored in bacterial membranes through hook and basal body structures and are driven by membrane potential. Provides motility so the bacteria can follow chemotaxis.

Question 36

What are plasmids?

Answer 36

pieces of DNA that replicate independently of chromosomal replication. They may exist in an episomeform that can integrate into the bacterial chromosome and replicate with it. Plasmids tend to carry antibiotic resistance genes, toxic genes, and transposons (moveable genetic elements).

Question 37

What is the 1st step in peptidoglycan synthesis?

Answer 37

Synthesis in the Cytosol

UDP-NAG and UDP-NAM polymers formed

Peptides added to UDP-NAM

Question 38

What is the 2nd step in peptidoglycan synthesis?

Answer 38

Synthesis in the Cell membrane

UDP-NAM transferred to a lipid carrier (bactoprenol)

Bactoprenol is a carrier for NAG-NAM to take it across the membrane, then the carrier gets recycled

UDP displaced

NAG added to NAM

Bactoprenol transports to a cell wall growth point

Question 39

What is the 3rd step in peptidoglycan synthesis?

Answer 39

Synthesis in the Periplasm or exterior

Autolytic enzymes cut NAG-NAM loose from bactoprenol

New NAG-NAM polymer is added to the cell wall

Cross-linking of peptides occurs

Penicillin Binding Proteins (PBP’s) are enzymes that cross-link amino acids

Question 40

What is the mechanism of action of penicillin?

Answer 40

Penicillin- inhibit the transpeptidation enzymes involved in cell wall synthesis
Active against G+ and G- Bacteria
React with Penicillin-Binding Proteins
The transpeptidase binds penicillin (which inhibits it) thereby preventing the cell wall from properly forming and causing it to fall apart, as a result killing the cell (bacteriocidal)
Have a β-lactam ring structure that is inactivated by β-lactamases (penicillinases), which are genetically coded in some bacterial DNA or some R plasmids.

Question 41

What is the mechanism of action of cephalosporins?

Question 42

What genera form spores?

Answer 42

• Some G+ (but never G-) bacteria such as members of the genera Bacillus and Clostridium are spore formers
o Bacillus antrhacis (anthrax) & Clostridium tetani (tetanus; lock jaw)

Question 43

What is the importance of spore formation?

Answer 43

• Under harsh environmental conditions, such as loss of a nutritional requirement, sporulating bacteria can convert from a vegetative state to a dormant state, spore. Location of spore may be used in identification of bacterium. The spore is a dehydrated, multishelled structure that protects and allows the bacteria to exist in “suspended animation”, it is the most resistive state of bacterium (difficult to decontaminate with standard disinfectants). However once the bacteria is in a favorable environment it may start back up the germination process essentially coming back to life.