Lecture 3 Flashcards by Cagn Walker

Structure of a prokaryotic cell

-No nucleus or nuclear membrane
-No membrane bound organelles
-Single, circular chromosome
-Smaller than eukaryotes

How well did you know this?

Not at all

Perfectly

Bacterial Cell wall

-Made of peptidoglycan
-Provides structure, shape, and prevents osmotic lysis

How well did you know this?

Not at all

Perfectly

Peptidoglycan cell wall

-polymer of disaccharide and amino acids
-sugar
•NAG
•NAM
•Sugars bound together by B (1,4) glycosidic (peptide) bond

How well did you know this?

Not at all

Perfectly

Gram positive

-Thick peptidoglycan layer over inner (cytoplasmic) membrane
-90% of gram-positive dry weight is peptidoglycan
Example:
Staphylococcus aureus)

How well did you know this?

Not at all

Perfectly

Gram negative

Double membrane
-cytoplasmic membrane—peptidoglycan layer—outer membrane
-10% of dry cell weight is peptidoglycan
Example:
E. coli

How well did you know this?

Not at all

Perfectly

Gram positive surface membrane features

Techoic acid and lipotechoic acid chains in peptidoglycan layer

How well did you know this?

Not at all

Perfectly

Gram negative surface features

-Porins and polysaccharides in outer membrane
-lipopolysaccharides pop up from outer membrane

How well did you know this?

Not at all

Perfectly

Hans Gram

-classified bacteria based on cell wall composition

How well did you know this?

Not at all

Perfectly

Function of B-lactam

-Antibiotic
-inhibits peptidoglycan formation

How well did you know this?

Not at all

Perfectly

Penicillin-binding proteins (PBPs)

Enzymes involved in the terminal steps of peptidoglycan peptide cross-linking

How well did you know this?

Not at all

Perfectly

Lysozyme

-innate immune system antibiotic
-breaks B-(1,4) glycosidic bond
-highly cationic and punctures membrane

How well did you know this?

Not at all

Perfectly

Gram indeterminants

-Some bacteria contain a waxy lipid, mycolic acid, in their cell wall.
-Gram +, but stains weakly
-important examples:
Mycobacterium
Nocardia

How well did you know this?

Not at all

Perfectly

Acid- fast stain (what)

Staining tests for mycolic acids

How well did you know this?

Not at all

Perfectly

Acid-fast stain (Ziehl-Neelsen stain) steps

Fix bacteria
Stain (carbon fuschin) must be driven into the cells with heat/phenol
Decolorized with acid-alcohol (3% HCl and 70% ethanol)
•not acid fast organism decolors
Counterstained with methylene blue
•gram indeterminate stays pink
•gram determinant turns blue

How well did you know this?

Not at all

Perfectly

Archaea

-Almost all archaea have an S-layer
•considered part of the cell wall
-Some have pseudomureins
•similar to peptidoglycan

How well did you know this?

Not at all

Perfectly

Pseudomurein

-glycosidic bond is B-(1,3) instead of B-(1,4) which makes it lysozyme resistant

How well did you know this?

Not at all

Perfectly

Bacterial cell membrane (cytoplasmic membrane)

-40% phospholipid and 60% protein
-6-8nm thick
-Highly selective permeable barrier
-Embedded proteins play an important role

How well did you know this?

Not at all

Perfectly

mRNA vaccines use what for delivery?

Lipid nanoparticles

How well did you know this?

Not at all

Perfectly

Cytoplasmic membrane difference between bacteria and Archaea

Bacteria
-Ether (C-O) linkage between side chain and head
-Disconnected bilayer
Archaea
-Ester (O=C-O) linkage
-connected bilayer

Permeability Barrier

-prevents leakage and functions as a gateway for transport of nutrients into and out of the cell
•small hydrophobic molecules and water can pass through the cell membrane
•Aquaporins

Anchoring proteins

-Site of many proteins involved in transport, bioenergetics, and chemotaxis
•can accumulate nutrients against a concentration gradient

Energy production

-Site of generation and use of the Proton Motive Force (PMF)
•There is a charge difference across the membrane
•Accumulation of protons on the outside and hydroxyl ions on the inside)
•Charge separation is a form of potential energy and provides energy for transport, ATP synthesis, and motility

Cytoplasmic membrane function

Uniporter: one way transporter
Symporter: one way transporter of two nutrients
Antiporter: two way transporter

Simple diffusion

-Substances move down their concentration gradient

Transport proteins

Can move substances against their concentration gradient and concentrate them inside the cell -highly specific -Requires energy

ABC transporter (ATP-binding cassette transporter)

Periplasmic binding proteins are involved and energy comes from ATP

Group translocation

Chemical modification of the transported substance drives import against a gradient

Lipopolysaccharide (LPS)

LPS is an Endotoxin: the lipid A component of LPS is a heat-stable toxin associated with the outer membranes

Porins

Porins are transport proteins of the outer membrane that passively import nutrients (and export molecules) but at the cost of protection from the environment/antibiotics

Glycocalyx

-Secreted to the outside cell wall -A sticky, viscous, gelatinous, hydrophilic polysaccharide for (1) attachment, (2) prevention of phagocytosis, (3) prevention of drying out, (4) nutrient traps —Capsule: neatly organized —Slime layer: unorganized and loose

Capsules

-only some bacteria have or acquire capsules •capsules are called K antigen -capsule is a virulence factor •hard casing, difficult to have immune cells deal with. Examples: Salmonella typhi Streptococcus pneumoniae

Biofilms

-Collection of bacteria stick together because of glycocalyx -Many glycocalyx built up

Biofilm examples

-Contact lense build up -pacemaker build up -chronic sinusitis -dental plaque

Endospores

-tough, resistant structure that allows the bacteria to essentially exist in ‘suspended animation’ Example: C. Difficile Tetanus Anthrax

Sporulation

-formation of endospore -Some Gram+ cells sporulate when the environment is inhospitable

Endospore staining steps

1. Primary stain: Malachite green with steam heat to force dye into the endospore 2. Wash with water. The green stain trapped in endospore will remain 3. Counterstain: Safranin (pink) with no heat

Motility

-Toward a positive stimulus, such as food source or light -Away from a negative stimulus, such as a toxin or darkness

Flagella

Complex organ of motility that serves as a “motor” -80% efficiency -PMF-driven Flagella proteins are referred to as a H antigens -made of chains of flagellin

Flagella staining

-Dye + Mordant on flagella •Mordant examples: tannic acid and aluminum potassium phosphates

Monotonous flagellation

One flagella on the end

Amphitrichous flagellation

One flagella on each end

Lophotrichous flagellation

A tuft of flagella is located on one end

Peritrichous flagellation

The flagella arise all over the cell body Peritrichous flagella tumble: -bundled flagella (CCW rotation) -tumble—flagella pushed apart (CW rotation) -flagella bundled (CCW rotation)

Polar flagellation

The flagella are located on the ends of the cells

Microbial taxis

Random Walk: -Random movement, both runs and tumbles Biased random walk: -if organism senses it is moving toward a higher concentration of the attractant, runs become longer and tumbles less frequent. The reverse is also true

Axial filaments

Spiral internal flagella Found in spirochetes