NRSG 205 Lecture 4 Part 1 - Prokaryotic Cells

2 requirements for prokaryotic cells

1. Unicellular

2. Lacks nucleus and membrane-bound organelles

Prokaryotic domains of life

1. Bacteria

2. Archaea

How do bacteria reproduce?

Binary fission (split in half)

3 examples of qualities that differentiate bacteria from each other

1. Morphology

2. Chemical composition

3. Energy sources

Size of most bacteria

Most are 0.2-2 μm

3 shapes of bacteria

1. Coccus (spherical)

2. Bacillus (ovular)

3. Spiral

Monomorphic bacteria

take on one shape

Pleomorphic

can take on multiple shapes

2 arrangements of bacteria

1. Strepto-: strip/chain of bacteria

2. Staphylo-: clusters of bacteria

Glycocalyx

sugar coating on the outside of the cell wall that helps the bacteria evade the immune system and its environment

4 functions of glycocalyx

1. Evasion of immune system

2. Adherence

3. Prevention of dessication

4. Nutrients

3 forms of glycocalyx

1. Capsule

2. Slime layer

3. Extracellular polysaccharide

Capsule

firmly attached to the cell wall, and their primary function is to evade phagocytosis (capsulated bacteria are more virulent)

2 examples of bacteria with capsules

1. Bacillus anthracis

2. Streptococcus pneumoniae

Slime layer

loosely associated with the cell wall, and primary functions are intercellular communication and attachment to surfaces

Extracellular polysaccharide (EPS)

biofilms that create a community of bacteria that communicate with another and help with attachment

What comprises flagella?

Bacterial flagellin

Function of flagella

rotates to push the organism forward

What kind of microorganism possesses axial filaments?

spiral bacterial cells

What is another name for axial filaments and why are they called this?

Also called endoflagellum because it has the same role as a flagella outside the cell (propulsion), but it wraps around the cell underneath an outer sheath of the cell wall

What class of bacteria possesses axial filaments?

Spirochaete

2 examples of specific bacteria with axial filaments

1. Traponema pallidum (syphilis)

2. Borrelia burgdorferi (lyme disease)

Fimbrae location

Protrude from the cell wall

Function of fimbrae

adherence to surfaces

Pili location

Protrude from the cell wall

2 functions of pili

1. Motility

2. DNA transfer

2 types of motility associated with pili

1. Twitching

2. Gliding

Sex pilus

DNA transfer allows for transfer of plasma DNA from one bacterial cell to another

Cell wall

structure that surrounds the plasma membrane

Cell wall function

protect cell from changes in water pressure

What comprises the bacterial cell wall?

Made of peptidoglycan (sugar-protein polymer consisting of NAG, NAM, and amino acids)

Gram positive bacteria cell wall

Gram positive bacteria have a very thick peptidoglycan layer that also contains teichoic acids, that surrounds the plasma membrane

Gram negative cell wall

Gram negative bacteria have a very thin peptidoglycan layer that surrounds the plasma membrane and is covered by the outer membrane

Lipopolysaccharides (LPS)

cover the outer membrane of the bacteria (also known as an endotoxin)

Function of bacterial outer membrane

 protects from antibiotics and anything else that may destroy bacteria

4 steps of gram staining

1. Add crystal violet stain that adheres to the peptidoglycan cell wall

2. Add iodine (mordant)

3. Decolorize with alcohol

4. Add safranin counterstain

2 forms of atypical cell walls

1. No cell wall

2. Acid-fast cell wall

Which type of bacteria naturally lacks a cell wall?

Mycoplasma

Plasma membrane structure

 lipid bilayer with phosphate heads (outward) and fatty acid tails (inward)

2 functions of plasma membrane

1. Control membrane proteins

2. Selectively permeable (controls what goes in and out of the cell)

2 types of movement across plasma membrane

1. Passive transport

2. Active transport

Passive transport

high concentration → low concentration (no energy required)

3 types of passive transport

1. Simple diffusion

2. Facilitated diffusion

3. Osmosis

Simple diffusion

small molecules freely move in and out of the cell

Facilitated diffusion

molecules move in and out of the cell through a transport protein or channel protein embedded in the plasma membrane

Osmosis

movement of water from low to high solute concentration

Active transport

up concentration gradient that requires transport proteins (energy required)

6 components of cytoplasm

1. Water

2. Organic and inorganic molecules

3. DNA

4. Ribosomes

5. Cytoskeleton proteins

6. Inclusion bodies

Nucleoid

Circular chromosome area where DNA is located

Which ribosome size is found in bacterial ribosomes?

70S ribosomes

Ribosome function

Site of protein synthesis/translation

Inclusions

Functional areas that are not membrane bound, but are reserved deposits

6 inclusions

1. Metachromatic granules

2. Polysaccharide granules

3. Sulfur granules

4. Lipid inclusion

5. Magnetasomes

6. Gas vacuoles

Metachromatic granules

hold onto inorganic phosphates (come in handy for energy production)

Polysaccharide granules

hold onto glycogen or starch (nutrition)

Lipid inclusion

hold onto lipids

Sulfur granules

Hold sulfur

Magnetasomes

Hold iron oxide

Gas vacuoles

Useful for buoyancy

Are endospores typically gram positive or gram negative bacteria?

Gram positive

Function/utility of endospores

Resting structure during adverse conditions (can survive harsh conditions)

Example of an endospore (harmful, real world application)

Spore-forming bacteria (i.e. bacillus anthracis) can be used as bioterrorism because of this

Example of an endospore (disease application)

Clostridium (another spore-forming bacteria) is responsible for tetanus and botulinum toxin

Archaella

Archaea equivalent of flagella

What are archaella made of?

Archael archaellin

Archaella function

 rotates to push the organism forward

What is the cell wall of archaea made of?

Pseudomeurin

Daptomycin

targets the plasma membrane

Polymyxins (Colistin, Polymyxin B)

target gram negative bacteria and disrupt outer membrane

Glycopeptides

target gram positive bacteria and inhibit cell wall growth

Beta-lactam antibiotics

target gram positive bacteria and cause cell lysis

Lipopeptides

target gram positive bacteria and inhibit cell wall growth

Isoniazid (INH)

targets acid-fast cell walls and inhibits mycolic acid synthesis

Lysinoalanine (LAL) crosslink inhibitors

target the flagella and interfere with the protein bonds of the flagella

Macrolides

target the 50S ribosome subunit and inhibits protein synthesis

Tetracycline

targets the 30S ribosome subunit and inhibits protein synthesis

Ciprofloxacin

targets bacterial DNA and is used for gram positive and gram negative bacteria

Levofloxacin

targets bacterial DNA and is used for gram positive, gram negative, and atypical pathogens

Moxifloxacin

targets bacterial DNA and is used for gram positive, gram negative, and atypical pathogens