Lecture 4: Microbial Physiology

Question 1

What are the three basic shapes of prokaryotic cells?

Answer 1

• rod
• coccus
• spirillum

Question 2

What size are prokaryotic cells?

Answer 2

1-5 micrometers

Question 3

Additional morphologies of prokaryotic cells

Answer 3

• Star shaped: stella
• rectangular Haloarcula (Archaea)

Question 4

Pleomorphic Bacteria Shapes

Answer 4

Rhizobium and Corynebacterium

Question 5

Largest bacteria ever

Answer 5

Thiomargarita Magnifica

Question 6

Cell wall

Answer 6

• peptidoglycan
• Sugar chains cross linked by peptides
• Cell wall building/turnover during growth and division can influence cell shape

Question 7

Turgor Pressure

Answer 7

• Cells contain lots of stuff-DNA, proteins, sugars,
  salts
• If cells are in an aqueous (watery) environment,
  the surrounding medium has less stuff in it
• Because of this disparity, water tends to flow into
  the cells, results in turgor pressure

Question 8

Rod Shaped

Answer 8

• bacilli (bacillus is a genus name)
• G+ and G- rods

Question 9

What axis do bacilli divide?

Answer 9

divide along narrow axis

Question 10

Streotiobacilli

Answer 10

long chains of rods

Question 11

diplobacilli

Answer 11

pairs of rods attached end to end

Question 12

coccobacilli

Answer 12

very short rods, almost cocci

Question 13

vibrios “curved rods”

Answer 13

• Vibrio cholerae the agent of cholera
• In the book described as spiral bacteria, but phylogenetically aligned with G- rods

Question 14

cocci

Answer 14

sphere
- gram negative and positive

Question 15

different cocci have ___ division planes

Answer 15

different

Question 16

What possible advantage is there to being rod or spirillum shaped vs. cocci?

Answer 16

The way they associate with surfaces is different. Rod shaped has more contact with the surface than spheres. The way they stack/pack is also more beneficial.

Question 17

Streptococci

Answer 17

divide along a single plane, form chains

Question 18

Staphylococci

Answer 18

divide along all planes, form clumps

Question 19

how do other cocci divide?

Answer 19

form tetrads and sarcinae, as well as pairs (diplococci)

Question 20

Spirillum

Answer 20

• one or two turns around helical axis
• external flagella

Question 21

Spirochete

Answer 21

• flagella sheathed, run along length of cell
• “corkscrew motility”
• Borrellia Burgdorferi (Lyme disease) , treponema pallidum (syphilis)

Question 22

Prokaryote Physiology

Answer 22

• Cell Membrane
• Outer membrane
• Cell wall (peptidoglycan)
• Exopolysaccharide matrix
• Flagella
• Pili and Fimbriae
• Genome Structure
• Ribosomes

Question 23

Overall Bacterial Structure

Answer 23

• External structures
  (pili, flagella, fimbriae)
   Outer Membrane G-
  only
   Cell wall
  (peptidoglycan sacculus or wall)
   Cell membrane
   Cytosol

Question 24

3 parts of Flagella

Answer 24

3 parts
- filament (made of the protein flagellin)
- hook (different protein)
- Basal body

Question 25

Flagellar Assembly

Answer 25

- flagellin subunits travel up through the middle of the flagellum, to the growing tip - similar, evolutionarily related to Type III secretion important in pathogenesis.

Question 26

_____ flagella-distributed over cell body

Answer 26

Peritrichous

Question 27

On cell surface, flagella can also be at....

Answer 27

the poles

Question 28

monotrichous

Answer 28

single at one end

Question 29

lophotrichous

Answer 29

clump of flagella at one end

Question 30

Amphitrichous

Answer 30

flagella at both ends

Question 31

Spirochete Flagella

Answer 31

- Very cool structure  Doesn’t emerge from the cells  Cool propulsion mechanism  Cryoelectron tomography

Question 32

Are all bacteria motile?

Answer 32

No

Question 33

Types of motility

Answer 33

- Tumble and swim chemotaxis - “gliding motility” - Spirochete corkscrew motility

Question 33

Fimbriae

Answer 33

- generally smaller and spread throughout a cell - Fimbriae-protein filaments on cell outer surface - Either at poles or evenly distributed - Important in cell attachment to surfaces - Well studied in Neisseria gonorrhoeae - Fimbriae are a virulence factor for enteric, urogenital pathogens

Question 34

What do bacteria secrete/their pathways?

Answer 34

- make proteins to be exported to periplasm and surroundings - Sec pathway (general secretion) - Sec independent (type II) - Type III (virulence) - there are 10 known secretion pathways

Question 34

pilus/pili

Answer 34

- generally larger/longer and more sparse on the cell - involved in cell-cell attachment phenomena, in preparation for DNA transfer (conjugation) - Pili are sometimes the site of attachment for bacteriophages, viruses that infect bacteria

Question 35

Exopolysaccharide (EPS) Matrix (glycocalyx)

Answer 35

- Environmental bacteria often live on surfaces covered in EPS - Called a biofilm - In pathogenic microbes, this is often called the slime capsule - An important defense against the immune system - A virulence factor, esp. for G+ cocci pathogens

Question 36

S. Pneumoniae Capsule

Answer 36

- Streptococci are known for the production of capsule - Primary component hyaluronic acid - Mutants that don’t make capsule are avirulent - This was used to prove that DNA is the genetic material (1941)