Lecture 7: Appendages and Internal Structures

Question 1

Describe the structural differences between capsules and slime layers.

Answer 1

Capsules are well organized and tight around the cell.

Slime layers are loosely organized (stringy) and are harder to visualize.

Question 2

List two functions of capsules and slime layers.

Answer 2

1. Allows adhesion to surfaces.

2. Prevents our own cells from phagocytizing the bacteria.

Question 3

Discuss two examples of how formation of glycocalyces by bacteria affect human life and health. Compare the structure of a flagelllum to that of a type III secretory system.

Answer 3

Glycocalyces can be formed by:

1. Sucrose in the mouth induces glycocalyx production which may cause tooth decay.
2. Psudomonas produces a biofilm which can surround and clog water pipes. Pseudomonas produce algamate and adheres to the surfaces of pipes and water intakes and causes biofouling. Biofouling is many layers of glycocalyces.

The flagellum contains a roter (that contains a hook o produce torque), a state, bushings, a reverse gear (C-ring). The type III secretory systems have a roter as well but it does not have a hook and therefore has no torque. It has brushings but does not have a stater and does not have a reverse gear (C-ring).

Question 4

Understand how reversal of flagellar rotation leads to running and tumbling.

Answer 4

When tumbling, reorientation is completely random. The flagellum will spin in the direction of running as long as it is close to the attractant, if it becomes further from the attractant, it will tumble until it reorientates in the correct direction of the attractant.

Question 5

Understand that bacteria only move towards continually increasing concentrations of a nutrient.

Answer 5

The cell suppresses tumbling when attractant binds to the chemoreceptor, alpha-helix is pushed downward, it inhibits phosphorylation and the bacteria will continue to run. The cell with methylate (at a delay and will undo phosphorylation) when the chemoreceptor no longer is bound to enough attractant, the alpha-helix will be pushed back upward, and will begin to tumble until it gets in a more concentrated area of attractant.

Question 6

List four major functions of pili.

Answer 6

1. Motility
2. Transfer electrons (nanowires)
3. Adhere to surfaces (fimbriae)
4. DNA transfer; Horizontal Gene Transfer (F-pilus)

Question 7

Contrast flagella-based motility with pilus-based motility.

Answer 7

Flagella-based motility is a lot less powerful than the pilus-based motility. Pilus-based motility occurs in more of a twitching and grappling hook manner.

Question 8

Explain why bacteria form storage granules under some growth conditions.

Answer 8

Storage granules are used as reserve stores for metabolism.

Question 9

List 3 major types of storage granules.

Answer 9

1. Carbon
2. Phosphorous
3. Sulfer
   (nitrogen is also one but we did not discuss it)

Question 10

Explain how bacteria increase the efficiency of some enzymes by concentrating them and their substrates in intracellular inclusion bodies.

Answer 10

Bacteria have micro-compartments that concentrate enzymes and substrates. Like a camera shutter, proteins rotate to open or close a pore, trapping enzymes inside. The more concentrated the enzyme is, the more catalytic it will be.

Question 11

List four types of bacterial intracellular inclusion bodies.

Answer 11

1. Photosynthetic pigment- Phycobilisomes
2. Photosynthetic pigment- Chlorosomes
3. Gas Vesicles for Buoyancy
4. Magnetosomes (acts like a compass in order to steer the bacteria into the right environment).

Question 12

List the seven steps involved in endospore synthesis.

Answer 12

Stage 0: Normal growth
Stage 1: Bacterial division
Stage 2: Assymetric Septation
Stage 3: Engulfment
Stage 4: Cortex synthesis
Stage 5: Coat Synthesis
Stage 6: Lysis of Mother Cell
Stage 7: Free Spore

Question 13

Explain how the structures of the endospore (coat, cortex, and core) protect it against chemical damage, radiation, and dehydration which allow spores to survive for millennia.

Answer 13

Spores DNA is inert (inactive) because it is wrapped around SASP (which is similar to our histone proteins).

Calcium dipicolinic acid reduces water activity and therefore enzymatic activity in the core. This reduces the amount of energy that the endospore uses.

Loose peptidoglycan in cortex soaks water out of the core. Water has a high heat capacity so without water, the heat capacity is lower and the endospore is less likely to be damaged by heat.

The dense protein coat protects against UV and radiation.