External Bacteria Structure

What are the shapes and arrangements of bacteria?

• cocci (circular)

• Bacilli (rod-shaped)

• spiralia (spiral)

• filamentous

• fruiting

• arrangements

  • singles

  • diplo (pair)

  • staphlylo (clusters)

  • tetrad (3)

  • strepto (chains)

What shape/arrangement is this bacteria?

diplobacilli

What shape/arrangement is this bacteria?

streptobacilli

What shape/arrangement is this bacteria?

staphylococcus

What shape/arrangement is this bacteria?

spirilla

approximately how big is a

• red blood cell

• typical bacteria (ex. E coli)

• streptococcus

• virus

• red blood cell - 7um

• typical bacteria (ex. E coli) - 4um

• streptococcus - 1um

• virus - 20 to 400nm

What are the main functions of the bacterial cell wall?

• maintain turgor pressure (osmotic balance)

• protection from host/environment

Describe the peptidoglycan structure

• 1 strand of peptidoglycan repeats NAG and NAM disaccharides

• peptides extend out from backbone

• forms a helical molecule crosslinked by glycenes attached to NAM or through covalent bonds between amino acid peptides (Depends on bacteria)

What phyla are gram positive cell walls most often seen in?

firmicutes and actinobacteria

What is teichoic acid?

• in gram positive cell walls

• polymers covalently connected to peptidoglycan chains

• extend from plasma membrane surface through peptidoglycan layer

• present in gram positive bacteria

• anchor peptidoglycan wall to membrane

• protection against antibiotics and host immune response

• perform ion uptake

• can help bacteria bind to a bacteria tissue for spreading

What is the periplasmic space?

The space between the plasma membrane and beginning of outer membranes of bacteria

What are porin molecules?

• transport across outer membrane through passive diffusion

• hydrophilic channel

• integrated in outer membrane

• in gram-negative cells

How do gram positive and gram negative cell walls differ?

• gram positive - thick peptidoglycan layer, teichoic acid for support, protection and binding,

• gram negative - outer membrane above thin peptidoglycan layer, porin, LPS, outer membrane receptors

What is LPS (lipopolysaccharide)?

• component of outer membrane of gram-negative bacteria

• contributes to overall negative charge of outer membrane

• stabilizes outer membrane

• creates permeability barrier

• protect from host defense (pathogens)

• potential target for host; often changed to avoid effective immune responses

• 3 parts - Lipid A/Endotoxin, core, O antigen

What are the 3 components of the LPS?

• Lipid A (endotoxin) - anchors into outer membrane

• core

• O antigen

Is porin present in gram positive or gram negative bacteria?

gram negative

What is osmotic lysis?

Osmotic lysis is the rupture of a cell due to an influx of water, causing the cell to swell and burst, often occurring in hypotonic environments.

What happens when penicillin or a lysozyme breaks/inhibit cell wall syntheses?

• forms protoplast (w/messed up cell walls)

• cant regulate osmosis in cells and bursts (lysis)

What are mycoplasma?

Mycoplasma are a group of bacteria that lack cell walls, making them resistant to antibiotics that target cell wall synthesis

What are capsules?

• well organized layers firmly attached to outside of cell wall

• usually polysaccahride

• not vital for growth (can live without)

• virulence factors

what is a slime layer?

• zone of unorganized material on outside of cell

• not very well attached

• protection, adhesion to surface

What is an S layer?

• ordered surface covering on outside of cell

• protein or glycoptrotein composition

• provides shape and protection

• some virulence factors

• useful for adhesion

What are glycocalyx?

general term for any outer covering on surface of cell wall or outer membran eof bacteria

What are Pili?

• hair-like filamentous appendages on surface of bacteria

• for attachment, DNA exchange, motility

• Sex pili for conjugation

• shorter and thinner than flagella

What are fimbriae?

• filamentous protein structure on surface of bacteria

• shorter than pili

• for attachment

What are flagella used for?

mostly motility, but also attachment and as a virulence factor

Describe the 3 parts of flagella

1. filament - made of flagellin protein subunits; ringed structure

2. Hook - projects filament from cell; attached to basal body

3. basal body - extends from outer membrane/peptidoglycan to proteins in plasma membrane; motor part, powers turning through e- transfer

What are the 4 types of flagellar distribution?

• monotrichous - 1 flagella

• lophotrichous - multiple flagella on one end

• amphitrichous - flagella on both ends

• peritrichous - flagella all over

What are the types of flagellar movement?

• counterclockwise

• clockwise

• swarming (cells move in unison across surface)

What is chemotaxis?

nonrandom movement in response to stimuli; go towards food or away from danger

How do spirochetes move and why?

• move in an undulating pattern

• flagella wrap around inside periplasmic space

What are endospores?

• Highly resistant structures formed by some bacteria to survive harsh conditions, allowing them to endure extreme temperatures, desiccation, and radiation

• have specialized spore coat

• no division (dormant)

• germinate when conditions improve

Briefly describe sporulation

• process of forming endospores from Mother cell

How large are eukaryotic cells typically?

Eukaryotic cells are typically 10 to 100 micrometers in diameter, larger than prokaryotic cells.