MCB Exam 3

Gram positive (purple)

no outer membrane, thick peptidoglycan (large pores), thin periplasmic space, find proteins and Teichoic and lipoteichoic acids floating around

Teichoic acids

dont go down the plasma membrane, floating around peptidoglycan

lipoteichoic acids

floating around peptidoglycan, tail goes into plasma membrane and is anchor

Gram negative (pink)

bigger periplasmic space (PPS) with lots of enzymes and proteins (brauns lipoprotein) floating, ppetidoglycan THIN embedded in PPS, outer membrane made of LPS, has porins and transporters

porin proteins in E.coli

more permeable than plasma membrane due to presence of porin proteins and transporter proteins

LPS (lipopolysaccharides)

in outer membrane of gram -

gram -, lipids + sugars

made of Lipid A, core polysaccharide, O antigen

LPS function

negative charge on cell surface, stabilize outer membrane, permeability layer, biofilm formation (sticky attachment), protection (endotoxin)

Brauns lipoprotein

= anchor outer membrane to peptidoglycan in gram -

Lipid A

OUTER MEMBRANE, inner layer of LPS fatty acids, rigid/ anchor —> endotoxin in environment

Core polysaccharide

links lipid A and O antigen together, made of sugars

O antigen/ side chain

External part of LPS, largest

mechanisms of gram staining

Gram + : Thick peptidoglycan layer dehydrates and shrinks during decolorization, trapping the crystal violet

Gram - : Outer membrane (LPS) is dissolved by the decolorizer, and the thin peptidoglycan layer loses the dye

Flagella

extends from cell envelope (embedded in cell wall)

• spiral thin rigid

peritrichous

entire surface flagella

polar flagella

flagella attached at one end of the cell

monotrichous flagella

one flagella

amphitrichious flagella

single flagella at each end

lophotrichous flagella

cluster of flagella at one or both ends

flagella components

filament hook basal body

Filament

external and longest layer, hollow, rigid, flagellin subunits

• sits in hook protein

Hook protein

connects filament to basal body

basal body

= motor portion, anchor basal body to cell

made of hollow shaft with ring structures (more in gram -)

basal body of flagella in gram - cells (4 rings)

• L ring - outer

• P ring = peptidoglycan

• MS ring = plasma membrane

• C ring = cytoplasm

basal body of flagella in gram + cells (2 rings)

• inner and outer rings

Building Flagella

builds from tip

operon = holds genes so they can be transcribed at once

Bacterial Flagellar Movement

propeller, Counterclockwise = run, clockwise = stop/tumble

Chemotaxis

use flagella for directed movement in response to chemical stimulus, must have flagella and chemoreceptors

archaea = can move backwards

bacteria can not

positive chemotaxis

movement toward a chemical stimulus

negative chemotaxis

movement away from a chemical stimulus

chemotaxis system

chemoreceptor --> cheW --> cheA --> cheY --> cheZ --> motor switch

cheW

receives info from chemoreceptors

cheA

sensor kinase that phosphorylates CheY

cheY

allows us to change the orientation of movement

cheY - phosphorylated

run to a tumble

cheY - dephosphorylated

tumble to a run

How flagellum spin

rotor + stator

rotor

C ring + MS ring (gram -)

inner + outer ring (gram +)

stator

electromagnet, mot A + mot B = form PMF and spin rotor

spirochetes

INTERNAL flagella, wrap around periplasmic space = cork shape

Nonflagaller motility

1. gliding motility

2. twitching motility

3. polymerization of actin

gliding motility

slime layer secretes smooth sliding over a surface

twitching motility

slow, jerky process using pili (army crawl by sticking)

polymerization of actin

move intracellular bacteria between hosts and adjacent cells, uses as tail

Pili main function

1. adherence

2. conjugation

Stalk

low nutrient environments, extension of cell membrane to get more surface area to get more nutrients

holdfast = sticky tip of stalk w polysaccharides

S layer (layer outside cell wall)

Surface, composed of proteins

Glycocalyx (layer outside cell wall)

capsule OR slime layers

• aid in attachment to solid surfaces

capsules (glycocalyx layer)

polysaccharides, thick layer, visible in light microscope

1. protection (thick layer hides it)

2. adherence sticky

Slime layer (glycocalyx layer)

polysaccharides, thinner and Unorganized (cant see under light microscope), can easily remove

1. attachment

2. protection

• motility (gliding motility)

S layer (surface array layer)

proteins and glycoproteins that self assemble (cage over bacterial cell like chainmail)

Gram - = S layer outside membrane

Gram + = S layer peptidoglycan surface

s-layer functions

1. protect from ion + pH fluctuations, osmotic stress, enzymes, and predation

2. maintain shape and rigidity

3. promote adhesion to surfaces

4. protect from host defenses

5. nanotechnology uses

Endospores

resistant to heat, radiation, chemicals, desiccation

soil-dwelling complex, dormant structure formed by some bacteria

endospore location examples

central, swollen sporangium, terminal, subterminal

bacterial endospore layers

• core

• nucleoid

• core wall

• cortex

• inner coat

• outer coat

Core endospore

DNA, dehydrated

inner membrane of endospore

germinant receptors

cell wall of endospore

peptidoglycan

cortex of endospore

large part of spore volume

peptidoglycan (specialized, not fully cross-linked), heat resistance

cross-linked proteins

separates the inner and outer coat of endospores

exosporium (optional)

glycolipids and another layer to block environmental factors

what makes endospores so resistant?

1. calcium w/ dipicolinic acid - will dehydrate cells

2. dehydrated core - metabolically inactive

3. spore coat + exosporium

4. small, acid-soluble DNA binding proteins (SASP) - block UV rays

sporulation

all or nothing response, starts when theres no nutrients, spo0A = regulator

7 stages of sporulation

1. axial filament formation - DNA replication occurs

2. septum formation and forespore development

3. engulfment of forespore

4. cortex formation - peptidoglycan between inner and outer membrane

5. coat synthesis

6. completion of coat synthesis - increase in retractility and heat resistance

7. lysis of sporangium, spore liberation - mother cell lysis

Germination

spore back to normal vegetative cell

vegetative cell formation

1. activation, 2. germination - environmental nutrients are detected, spore swelling, rupture of absorption of spore coat, loss of resistance but increased metabolic activity, 3. outgrowth - emergence of vegetative cell by breaking through spore coat

taxonomy

• phylum

• class

• order

• family

• genus

• species

methanogens

first named archaeons

archaea determined to be different from bacteria

through sRNA sequencing

how are archaea similar to bacteria?

• size (but archaea longer)

• shape + rectangular

• singular, circular chromosome

• lack membrane bounded nucleus

how are archaea similar to eukarya?

• dna complex with histones (larger genome)

• dna replication/ transcription/ translation machinery

Distinct Archaeal Features

plasma membrane organization and cell wall composition

Cell envelope Archaea

6 configurations

ALL have plasma membrane

Archaeal Plasma Membrane

• can be bilayer or monolayer (mono = rigid, better for hot envi)

• selectively permeable

• contains hydrocarbons derived from isoprene units

• hydrocarbons are attached to glycerol by ether linkages

what type of bond holds hydrocarbons in cell envelope in archaea? bacteria?

bacteria - ester

archaea - ether

bilayer plasma membrane archaea

glycerol 1-phosphate + phytanyl

monolayer plasma membrane archaea

glycerol 1-phosphate + phytanyl + glycerol 1-phosphate

Cell wall archaea

• same function but more diverse w 5 configurations

• S layer bigger role

• pseudomurein - no peptidoglycan

• beta-1,3 linkage - not beta-1,4 (lysozymes wont work)

• NAG and NAT - no NAM

• no d-ala (transpeptidase wont work)

cannulae (S layer archaea)

• S layer element

• not all have

• hollow glycoprotein tubes that form network between cells

hami (S layer archaea)

barbed wire with grappling hook on end, major role = attachment, help form biofilms

Archella (S layer archaea)

similar to flagella, they rotate to move the cell, evolved independently

1. thinner

2. composed of 2+ flagellin proteins

3. grow from base rather than tip

energy to flip = hydrolyzing ATP in archaea

Dont tumble, CCW = forward CW = backwards

metabolism

all of the chemical reactions that occur within an organism

catabolism

releases energy as it breaks down molecules

anabolism

uses energy as it builds up molecules

1st law of thermodynamics

energy is neither created nor destroyed

2nd law of thermodynamics

every energy transfer or transformation increases the entropy of the universe.

metabolic pathways determined by

enzymes, decrease activation energy = speeds reaction

spontaneous reaction

free energy of products must be less than that of reactants

enzymes do not alter

amount of free energy

greater Ea

slower

how do enzymes lower the activation energy?

increasing concentration of substrates and orienting substrates properly

Enzyme Substrate Interaction

1) lock and key

2) induced fit

lock and key

all active site have specific conformation that substrate (key) fits in

Induced fit

complementary conformation active site (doesnt change), enzyme is flexible and can determine final enzyme

apoenzyme

protein portion of an enzyme, inactive

coenzyme

organic cofactor

holoenzyme

whole enzyme = apoenzyme + cofactor

cofactor

nonprotein portion of an enzyme that can activate it

coenzyme (temporary) + prosthetic groups (permanent bond)

Enzymes denatured by

temperature and pH

Vmax

max rate of reaction, when all enzyme active sites are completely saturated with substrate