Microbiology Lecture 5: Composition And Structure

Front 1

What is the outer covering of the cell called?

What does it consist of (3)?

Back 1

Cell envelope

Cell envelope consists of:
Cell membrane, semi permeable
Cell wall, rigid
In Gram negative bacteria, extra layer outer membrane.

Front 2

The plasma membrane is also known as...(2)

What is the function of the plasma membrane?

Back 2

Aka, cell membrane, cytoplasmic membrane.

Function is regulation the passage of molecules and ions, as well as rigidity.

Front 3

What is the structure of the plasma membrane?

How are the associated proteins removed?

Back 3

60-70% protein, 40-30% lipids (phospholipids.)

Intrinsic proteins removed by detergents
Extrinisc proteins removed by mild NaCl

Front 4

In bacteria domain, the lipids in the plasma membrane have BLANK linkages between BLANK and BLANK BLANK. In the Archaea the linkages are BLANK linkages between BLANK and chains of BLANK

Back 4

Ester
glycerol
fatty acids

Ether
glycerol
isoprene

Front 5

Plasma membrane

1. Intrinsic, BLANK proteins, make BLANK of the membrane proteins. Embedded in the BLANK of the lipid bilayer.
2. Extrinsic, BLANK proteins, found on the lipid bilayer. Some bind to the BLANK proteins.

Back 5

integral
70-80%
interior

peripheral
intrinsic

Front 6

The plasma membrane possess a net BLANK charge. A molecule’s passage through it depends on BLANK BLANK; certain large molecules are degraded by BLANK BLANK

Back 6

negative

lipid solubility

hydrolytic enzymes

Front 7

The shapes of cells are due to their cell wall, aka the BLANK

What is the function of the above? What does it consist of?

Back 7

Sacculus

It is a barrier to the environment. Consists of peptioglycan.

Front 8

What does peptidoglycan consist of?

Back 8

Polysaacharide chains of glycan wrapped in circles linked by peptides of 4 amino acids

Front 9

Peptidoglycan consists of repeating units of two carbohydrate derivatives, BLANK and BLANK. Which one is only found in peptidoglycan?

Both are linked to each other via...

Back 9

NAG, N acetylglucosamine
NAM, N acetylmuramic acid

NAM only

beta 1,4 linkages

Front 10

In cell walls, attached to the NAM are 4 amino acids, a BLANK.

What is the amino acid sequence in G- and G+?

Where is NAM not found?

Back 10

tetrapeptide.

G-: L-alanine, D-glutamate, Meso diaminopimelate, and D-alanine

G+: L-alanine, D-glutamate, L-lysine, and D-alanine

Archaea

Front 11

Penicillin blocks formation of the BLANK BLANK; penicillin only works on BLANK bacteria

Back 11

pentaglycine bridge

growing

Front 12

The mechanical strength of peptidoglycan in the cell wall is due to the BLANK between NAM and NAG.

Major strength comes from the cross linkages between BLANK and BLANK of adjacent tetrapeptides.

Back 12

beta 1,4 linkages

the 3rd and 4th amino acids

Front 13

In gram positive bacteria, the tetrapeptides are linked via a BLANK BLANK. About BLANK of the tetrapeptides are cross linked. The peptidoglycan consists of BLANK of their cell wall.

The remainder is acidic polysaccharides, BLANK BLANK, which are repeating BLANK or BLANK units linked via phosphodiester linkages.

Back 13

pentaglycine bridge
75%
90%

teichoic acids
ribitol or glycerol

Front 14

Gram negative bacteria has cross linking between the BLANK and BLANK tetrapeptides.

Cross linking occurs at a BLANK frequency; peptidoglycan layer represents BLANK to BLANK of the cell envelope.

Back 14

D-alanine
meso diaminopimelate

25%
5 to 20%

Front 15

The cell wall in gram negative bacteria also has a...

What does it consist of? Where do lipoproteins attach?

Back 15

Outer membrane

Outer membrane consists of phospholipid bilayer with proteins and lipoproteins

Peptidoglycan layer

Front 16

BLANK molecules aka BLANK are arranged within the external phospholipid layer and account for BLANK of the Gram negative cell surface.

What is an example?

Back 16

Lipopolysaccharide (LPS)
endotoxins
40%

Braun's lipoprotein

Front 17

What are the three components of LPS aka endotoxins?

Back 17

1. O-specific side chain: O antigen polysaccharide
2. A core polysaccharide
3. Lipid A portion: toxic glycophospholipid

Front 18

Lipid A is responsible for BLANK and BLANK seen with Gram negative infections.

BLANK variants of salmonella, detected by...

Back 18

Fever and shock

2400

antiserum

Front 19

Why was the Gram stain developed?

Back 19

To differentiate between streptococcus and human lung tissue.

Front 20

Bacterial cytoskeleton
-homologous to BLANK and BLANK
-BLANK in s. aureus
-BLANK in E.coli

Back 20

tubulin and actin

Fts Z

Nre B

Front 21

How are bacteria without cell walls derived? How are the cells stabilized?

Back 21

Lysozyme is used to hydrolyze the 1,4 linkages between NAG and NAM.

Stabilized in sucrose aka protoplast

Front 22

What are L form bacteria? Name an example.

How are they grown?

Back 22

Bacteria that lack cell walls.
Ex: mycoplasma
Grown in penicillin.

Front 23

What is gap that separates the plasma membrane from the outer membrane called? What is located in this space?

It is only seen in...

Back 23

The periplasm

Hydrolytic enzymes

Gram negative bacteria

Front 24

What is an additional layer external to the cell, found on many pathogenic bacteria? What is it's purpose? What does it consist of?

Back 24

Capsules

protects against ingestion of phagocytes

consists of polysaccharide or glycoprotein.

Front 25

T or F: Capsules are easily detected by the human body
----------------------
What are two ways capsules are detected?

Back 25

FALSE FOOL
--------------------
Staining with India ink or a quelling reaction

Front 26

What genus of gram postive bacteria is responsible for dental plaque and food thickeners?

How does the process work?

Back 26

Leuconostoc which make dextrans

Leuconostoc converts sucrose into capsule or biopolymer

Front 27

What two organisms make dextrans?

What capsule was given as a vaccine in the 1960s?

Back 27

Leuconostoc and streptococcus mutans

Streptococcus pnuemoniae

Front 28

What are short thin structures found in large numbers on the surface of Gram negative bacteria?

What are the two types?

Back 28

Pili

Type I and F type

Front 29

What is the purpose of Type I pili? Name an example

What is the purpose of F type pili?

Back 29

For the attachment of bacteria to eukaryotic cells.
Ex: Neisseria gonorrhoeae

Makes the conjugation bridge to transfer extrachromasomal fragments between bacterial cells.

Front 30

Describe the synthesis of peptidoglycan polymers (4 distinct stages)

Back 30

1. NAM attaches to UDP to form UDP-NAM. Five amino acids are added to this complex. (Only time there is protein synthesis without ribosomes, mRNA, and tRNA.)

2. Complex moves to the plasma membrane, attaches to bactoprenol-P. (Which makes NAM more hydrophobic to transport across the phospholipid membrane.)

3. Complex is linked to UDP-NAG, the crosslinking peptide bridge is added to the pentapeptide.

The NAG-NAM-pentapeptide-bactoprenol complex moves across the plasma membrane & incorporated into cell well.

4. This newly synthesized section attaches to the existing wall by transglycosylation