Other Cell Structures

Question 1

What are the major attachment structures? What are their roles?

Answer 1

• Fimbriae
   Its role is attachment
   Assists in the formation of biofilms
   In pathogenic bacteria assists the attachment to host cells
   Fimbriae protein genes are found in plasmids
• Pilus
   Attaches bacteria cells to each other
   Its role is to facilitate horizontal gene transfer (conjugation)
• Glycocalyx
• Some pathogenic bacteria
• Aquatic prokaryotes: to attach to surfaces or each other (forming a biofilm)

Question 2

What is conjugation?

Answer 2

Horizontal gene transfer

Question 3

What are the different forms of the glycocalyx? What are the main features of each?

Answer 3

• Capsule
   Rigid, tightly organized
   Exclude large molecules
• Slime layer
   More loosely organized
   Doesn’t exclude large molecules
   Can’t be seen in traditional stains

Question 4

What are the function of the glycocalyx?

Answer 4

1) Attachment
a. Some pathogenic bacteria
b. Aquatic prokaryotes: to attach to surfaces or each other (forming a biofilm)
2) Motility
a. Gliding bacteria: non-flagellated motile bacteria
3) Protection
a. Against phagocytosis by white blood cells
b. Against dehydration
c. Against O2 levels

Question 5

Where is the glycocalyx located?

Answer 5

Outside the cell wall

Question 6

What is an endospore?

Answer 6

Highly resistant,h dormant structure produced by certain species of bacteria

Question 7

What is sporulation?

Answer 7

Process by which an endospore is produced

Question 8

Which organisms produce endospores?

Answer 8

some gram-positive bacteria

 Soil bacteria: e.g. Bacillus species, Clostridium species

Question 9

To what is an endospore resistant to?

Answer 9

	Heat
	Acid/bases
	Chemical disinfectants
	Dessication
	UV/ionizing radiation

Question 10

To what is the glycocalyx resistant to?

Answer 10

• Phagocytosis by white blood cells
• Dehydration
• O2 levels

Question 11

How can endospores be killed?

Answer 11

By autoclaving (121°C/15 psi)

Question 12

What are the possible locations of the endospore? What determines its location

Answer 12

Depends on genome location in cell
 Terminal spores
 Subterminal spores
 Central spores

Question 13

What is the structure of an endospore? What is the function of each component?

Answer 13

 Complex multilayer of proteins

• Exosporium: outermost layer; thin protein covering
• Spore coats: within the exosporium; thick layers of spore-specific proteins
   Responsible for impermeability of endospores to stains
• Core: surrounded by cortex
   Cortex: composed of loosely cross-linked peptidoglycan
   Provides rigidity to maintain core integrity
   The core contains the core wall, cytoplasmic membrane, and the cytoplasm

Question 14

What are the main characteristics of the endospore core?

Answer 14

1) Complex of dipicolinic acid and Ca2+
2) Partially dehydrated state
3) Low pH
4) SASPs (small acid-soluble proteins)

Question 15

What are the functions of the dipicolinic acid:Ca2+ complex?

Answer 15

i. Size exclusion molecules: decrease water content (i.e. dehydrate the endospore) in order to maintain DNA integrity in harsh environments
ii. Stabilize spore nucleic acids, especially non-genomic nucleic acids (stabilizes DNA against heat denaturation)

Question 16

Why is the endospore core partially dehydrated?

Answer 16

i. Increases resistance to heat and chemicals

ii. Reducing water shuts down metabolism

Question 17

What does a low pH accomplish in the endospore core?

Answer 17

Stabilizes genomic DNA

Question 18

What are SASPs?

Answer 18

(small acid-soluble proteins)

a. These proteins interact with acids, especially genomic DNA (nucleic acids)
b. Bind to DNA and further stabilizes genomic DNA (against effects of UV radiation and dry heat)

Question 19

What triggers sporulation?

Answer 19

exhaustion of nutrients
 Introduction to harsh environments
 Water depletion

Question 20

What is the vegetative cycle?

Answer 20

cell grows and divides

Question 21

What are the stages of endospore formation?

Answer 21

1. Assymetric cell division; commitment to sporulation
2. Isolation of prespore (separated from mother cell by septum)
3. Engulfment of prespore
4. Formation of cortex (around prespore; between cell wall and cytoplasmic membrane)
5. Formation of spore coat; import of Ca2+, SASPs and dipicolinic acid in prespore
6. Maturation: formation of layers of spore specific proteins; exosporium (?), coat; cell lysis
7. Germination: when the conditions are right, the endospore will germinate and be set free; formation of a new vegetative cell