Bacterial Capsules, Inclusions, and Endospores

Question 1

What is a bacterial capsule?

Answer 1

• usually composed of polysaccharides
• well organized and not easily removed
• seen well on a negative stain

Question 2

What are the advantages of having a bacterial capsule?

Answer 2

• allow for attachment to surfaces and each other (biofilms)
• helpful for nutrient absorption
• protects against desiccation, phagocytosis, viruses, detergents, toxins, and antimicrobials

Question 3

What are slime layers?

Answer 3

• similar to capsules except diffuse, unorganized and easily removed
• may aid in motility
• not seen well on a negative stain

Question 4

What are cell inclusions?

Answer 4

• aggregates of organic or inorganic material
• can be granules, crystals, or globules
• some enclosed by a single-layered “membrane” or invaginations of the plasma membrane

Question 5

What are storage inclusions?

Answer 5

• store nutrients, metabolic end products, and energy building blocks
• ex: carbon (glycogen, PHB), phosphate granules, sulfur globules, and nitrogen (cyanophycin granules)

Question 6

What are carbonate minerals?

Answer 6

• stored minerals used for stabilization in water

- ex: found in aquatic bacteria in alkaline lakes

Question 7

What are gas vesicles?

Answer 7

• store gas
• found in cyanobacteria (use oxygenic photosynthesis)
• have hollow protein tubes only permeable to gases
• aid in motility

Question 8

What are magnetosomes?

Answer 8

• magnetic bacteria
• held in invaginations of the cytoplasmic membrane
• typically found in water at the bottom (low O2 conditions)
• attracted to Earth’s magnetic field

Question 9

What are bacterial endospores?

Answer 9

• complex, dormant, survival structures formed by some bacteria
• have various locations in the cell (species specific)
• resistant to heat/freezing, radiation, chemicals, starvation, and desication

Question 10

What are the different locations of the endospore?

Answer 10

• central
• subterminal (close to end)
• terminal
• swollen sporangium (in a mother cell)

Question 11

What is the structure of an endospore?

Answer 11

• exporium on the outside
• spore coat
• outer membrane
• cortex
• germ cell wall
• inner membrane
• core

Question 12

What is the exosporium?

Answer 12

a thin outside layer of the endospore made of protein

Question 13

What is the spore coat made of?

Answer 13

proteins, very protective

Question 14

What is the cortex made of?

Answer 14

peptidoglycan, but less cross linked

Question 15

What layers of the endospore make up the vegetative cell?

Answer 15

germ cell wall, inner membrane, and core

Question 16

What is the core of an endospore made of?

Answer 16

• cytoplasm of the cell
• ribosomes, DNA, enzymes
• very dehydrated (frozen state)

Question 17

What makes an endospore so resistant?

Answer 17

• the core has low water content
• calcium dipicolinate binds water to dehydrate the core
• small, acid-soluble, DNA-binding proteins (SASPs) compact the DNA to keep it safe from the environment
• core has a slightly lower pH to keep enzymes from functioning
• exosporium and spore coat provide protection

Question 18

What triggers endospore development?

Answer 18

• harsh conditions

- typically a lack of nutrients that keeps the bacteria from being able to divide normally

Question 19

What is the process of sporulation and germination?

Answer 19

1. Asymmetric cell division commits the cell to sporulation. (Stage I)
2. The cell is divided into prespore and mother cell by a septum. (Stage II)
3. The prespore gets an outer membrane and becomes engulfed by the cell. (Stage III)
4. The cortex is formed around the endospore. (Stage IV).
5. The spore coat is added. Ca2+ and dipicolinic acid uptake occurs. SASPs are formed. (Stage V).
6. The cell matures and eventually lyses (Stage VI, VII).
7. The now free endospore germinates into a vegetative cell which can divide by binary fission or begin the process of sporulation again.

Question 20

How is the vegetative cell formed?

Answer 20

• activation prepares spores for germination (ex: heating)
• during germination, environmental nutrients are detected
• spore swelling and rupture of the spore coat occurs causing the cell to take in water
• endospores are no longer resistant and metabolic activity is increased
• eventually outgrowth occurs, where the vegetative cell emerges
• the exosporium, spore coat, outer membrane, and cortex are left behind