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Microbiology 265 > Week 3 - Bacterial Physiology > Flashcards

Week 3 - Bacterial Physiology Flashcards

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1
Q

Gram -ve inner membrane

A

Has an outer membrane, and a thin layer of peptidoglycan followed by the periplasm and then the cytoplasmic membrane

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2
Q

Gram +ve inner membrane

A

Have a thick layer of peptidoglycan and attached to the peptidoglycan are sugars such as teichoic acid and lipoteichoic acid.

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3
Q

Peptidoglycan Structure

A
  • found in all bacteria with a cell wall.
  • made from polysaccharides N- Acetylglucosamine and N- Acetylmuramic acid
  • the sugars and amino acids are connected by glycosidic and peptide bonds
  • has Beta 1,4 link which can be destroyed by lysozyme
  • Lysine, DAP (-) and ornithine are the amino acids used to form interbridges
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4
Q

Peptidoglycan facts

A

Gram -ve: thin. 2-7nm. Located between inner and outer membrane

Gram +ve: thick. 20-35nm. Located outside the plasma membrane.

  • particles less than 2nnm can pass freely though peptidoglycan layer, others need a protein channel.
    ( Na+, H20, mono & disaccharides, lysozyme, ATP)
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5
Q

Teichoic Acid

A

Found only in gram +ve bacteria.

These are long polymers of sugar alcohol and long phosphate repeating units.

sugar alcohols are reduced (OH) while sugars are not.

-protects bacteria from host defense system

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6
Q

Gram Negative Outer Membrane

A
  • asymmetric
  • inner: phospholipids
    outer: lipopolysaccharides (Endotoxin)

LPS has 3 main layers

Lipid A- attaches to the outer membrane. Has 2 glucosamine residues with lipids attached. Conserved among species.

Core- Has KDO & HEP sugars. Conserved among species.

O-specific: Has species specific sugars. Variable and not found in all bacteria.

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7
Q

Lipopolysaccharide Biosynthesis

A

the LPS core and O-antigen, but both are made in the cytoplasm.

use of ATP hydrolysis

O antigen is made on undecaprenyl pyrophosphate, in the cytoplasm.
A protein then flips the o-antigens to the periplasmic side.
More proteins help polymerize the o-antigen.

the core is made directly on the lipid A, an ABC transporter helps flip the molecule to the periplasmic side

another protein uses energy of the di-phosphates to help attach the o-antigen to the lipid A core

finally an ABC transporter helps move the LPS to the outer leaflet of the membrane

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8
Q

Lipopolysaccharides

A

Endotoxin

Contributes to negative charge of cell

Helps stabilize outer membrane

helps with attaching to surfaces

creates permeability layer

o-antigen protects from host defense systems

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9
Q

Prorins

A

Help make outer membrane permeable

b- barrels

found mostly in gram -ve bacteria

trimeric

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10
Q

S- layers

A

Crystal line latice of glycoproteins

not common in bacteria

self assemble into 2D sheets that attach to the LPS or peptidoglycan

protect against bacteriophage, low ph and lytic enzymes

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11
Q

Capsules & Glycocalyx

A

thick polysaccharide layers present on the surface of bacteria

not part of the cell wall.

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12
Q

Types of Capsules & glycocalyx

A
  • LPS/teichoic acid/ S-layer glycans
  • Alignate
  • poly N- acetylglucosamine
  • Enterobacterial common antigen
  • cellulose
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13
Q

Secretion Systems

A

Multi-protein spanning complexes. There are different types of protein complexes which allow for transport in and out of the cell.

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14
Q

Pili

A

Thin filamentous structures made of glycoproteins.

They extend from the cell surface, and are found in all gram -ve bacteria and in some gram +ve bacteria.

These pili are retractable and can go in and out of the bacteria.

The pili help with attachment of pathogens to the host tissue,
used in conjugation for DNA transfer.

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15
Q

Types of Pili

A

Fimbrae- adherence: help attach bacteria to a surface
Conjugation- exchange: exchange genetic material, and transfer DNA
Electrically conducive Pili - Transfer of electrons/ metabolism
Type 4 pili - used for twitching motility

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16
Q

Type IVa Pilus Structure

A

The pilus helps with adhesion and twitching

The pilus is built from the bottom up using a motor. The protein extends from the inner membrane, is anchored in the peptidoglycan by a ring and extends into the outer membrane where the pilus is. The pilus is made up of individual proteins. The pilus will attach to an object and the proteins connected to it retract which cause a pulling motion.

The pilus motor, uses ATP to spin. The direction that the motor spins determines if the pilus is getting built up or broken down.

17
Q

Twitching

A

Motility on a solid surface.

Using the type 4 pili, and ATP hydrolysis, the pili is extended attached to the solid surface and is retracted. These steps cause movement.

18
Q

Gliding

A

motility on a solid surface.

The bacteria rotate and spin forward. Using the PMF, adhesion proteins and gliding motors to move.

19
Q

Swarming

A

motility on a semi-solid surface

Fast, coordinated movement of cells that is mediated by flagella. Usually patterns are formed. Bacteria move together/ communicate this causes them to form patterns.

20
Q

Bacterial Flagella

A

Flagella are thin hollow appendages they help with swarming ( semi-solid) and swimming ( liquid). The powered rotation of flagella moves bacteria.

Flagella use the proton motive force to move. The protons go through the motor proteins. The flagellum motor has the rotor and the stator. The rotor has the filament, hook, and rod. The stator has the Mot AB proteins

21
Q

Peritrichous

A

Flagella around the cell surface

CCW rotation means flagella swim in a straight line and move forward. CW rotation means they tumble randomly in all directions.

22
Q

Polar

A

Attached at the ends of the cell

CCW rotation means the flagella run in the forward direction. CW rotation means the flagella go in the reverse direction

23
Q

Lophotrichous

A

Group of flagella at one end

Unidirectional flagella only run CW

24
Q

Bacterial Flagella Biosynthesis

A

Flagella grow from the tip.
They grow from the cytoplasm to the outer membrane.
The MS ring is made first followed by the mot proteins, P ring, L ring and the early hook.
The Late hook has the cap proteins which help the flagellin (protein) form into the filament.
Flagellin is made in the cytoplasm and pushes up through the hook to create the filament.

The base of the flagellum is embedded in the peptidoglycan so its sturdy.

25
Q

Chemotaxis

A

Moving in response to chemicals such as attractants. Bacteria can sense attractants and will move in the direction with an increased concentration of attractants.

26
Q

Archaeal Membranes

A

A Glycerol phosphate backbone with an ether link to the lipid, the lipid is called phytanyl and it has no double bonds.

There are diglycerol tetraethers which make a mono-lipid bilayer. (biphytanyl)

Some of the lipids
(crenarchaeol) have ring structures which make the membrane very rigid.

27
Q

Archaeal Cell Wall

A
  • Pseudomurein
  • Methanochondroitin; long carbohydrate molecule for stability
  • S- Layer
  • Sheath: second protein s layer

Much more diverse than bacteria.

28
Q

Pseudomurein

A

A repeating disaccharide it has NAGs and NATs rather than NAMs.
The glycosidic bond is a beta 1-3 bond which can not be broken down by lysosomes.

Lysosomes may not cut NATs so even if the bond was beta 1-4 it could remain inactive.

29
Q

Archaeallum

A

Flagella like structure in archaea.

Sits in the S layer.

Uses ATP hydrolysis rather than the PMF for movement.

30
Q

Archaeal hami

A

Homologous to pilin, they are thin filamentous structures.

Contain hooks and spikes on the end of the pilin to help with adhesion.

Hami are peritrichous.

31
Q

Archaea

A

Genome: Circular DNA, plasmids, no nucleus.

Ribosomes: 70s

Inclusions: Yes

Plasma Membrane: phospholipids containing ester linkages plus hopanoids and bactoprenol.
Bilayer

Cell Wall: All contain peptidoglycan. Some contain S-layers.

Motility Structures: Pili, flagella, focal adhesions.

32
Q

Bacteria

A

Genome: Circular DNA, plasmids, no nucleus.

Ribosomes: 70s

Inclusions: Yes

Plasma Membrane: Ether linked glycerolipids containing phytanyl. Monolayer or bilayer.

Cell Wall: No peptidoglycan, all contain S- layers.

Motility Structures: Hami, archaellum

Microbiology 265 (7 decks)

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