Lecture 14: Microbial Movement and Eukaryotic Cells

how fast do flagella spin and how fast can that move a cell?

Rotate at up to 300 revolutions per second (18,000 rpm)

What are the different terms used for numbers/placement of flagella?

• Monotrichous: 1 flagella

• Amphitrichous: at both ends of cell

• Lophotrichous: few flagella at one end

• Peritrichous: over whole cell

• Polar: at end(s) of cell

• Atrichous: no flagella, cocci

How do petrichously flagellated cells move compared to polarly flagellated cells?

Petrichously flagellated cells move slowly in a straight line while polarly flagellated cells move more rapidly and typically spin around

Which kinds will run and tumble?

Peritrichous flagella

What is run and tumble

• When flagella rotate counterclockwise, they bundle together, propelling the bacteria forward (run)

• When flagella rotate clockwise, the bundle falls apart and the bacteria stops and reorients itself (tumble

why run and tumble

Helps bacteria explore environment more efficiently (run when attracted to nutrients and tumble when moving away from repellents)

What does taxis mean?

Directed movement in response to chemical/physical gradients

What different types of taxis’ are there?

Chemotaxis, phototaxis, aerotaxis, osmotaxis, and hydrotaxis

What would positive and negative look like in each taxis

Positive: moving toward / Negative: moving away from

What is stronger for cells, an attractant or repellent?

Attractants because they’re essential for bacterial survival

What is gliding motility?

Type of movement that allows bacteria to move smoothly across solid surfaces without use of flagella

How does gliding motility work

Excretion of polyshaccharide slime, pilli involved, and gliding-specific proteins powered by PMF

How is it gliding motility powered

Powered by PMF/ATP hydrolysis

What is needed for gliding motility

Surface contact, a slime layer (in some cases), and specific gliding proteins/pilli for movement

What is an endoflagella/axial filament?

Internal flagella that move cell through torsion exerted on cell by endoflagellar rotation

who has endoflagella/axial filaments

Spirochetes aka spiral-shaped bacterial

• (ex: Borrelia burgdorferi and T. pallidum)

Borrelia burgdorferi causes what disease

Lyme disease

T. pallidum causes what disease

syphilis

What is cytoplasm and what is it made of mostly?

Gel-like substance that fills interior of cell. Made up of 80% water

Ribosome – what do they make?

proteins

ribosome size in prokaryotes

small subunit: 20S

large subunit: 50S

total size: 70S

ribosome size in eukaryotes

small: 40S

large: 60S

total: 80S

What kind of RNA do ribosomes read?

mRNA

What kind of RNA makes up ribosomes?

rRNA

ribosomes - What does the “S” stand for?

Svedberg (measures sedimentation rate in centrifuge)

ribosomes - Does math make sense?

No, math is based on sedimentation rate, not mass

If I have an antibiotic that targets a 70S ribosome will our cells be affected?

No, because eukaryotic cells have 80S ribosomes

What happens if there is an Intracellular bacterial infection?

Bacteria invade and survive inside host cells

Why is an intracelluilar bacterial infection bad?

Shielded from immune system, protected form antibiotics, and hijack host cell machinery

Nucleoid Region

Area where DNA is found

who has nucleoid region

Prokaryotic cells

are nucleoid regions always in the same place

No, nucleoid is not fixed in one location and can shift within cell as needed, depending on growth and division