Module 7B

Question 1

what are some features of Firmicutes

Answer 1

• Gram-positive
• low GC content (~45-60%)

Question 2

what are some features of Actinobacteria

Answer 2

• Gram-positive
• high GC content (>60%)

Question 3

what are some notable genuses of Firmicutes

Answer 3

• Staphylococcus
• Lactic Acid Bacteria (Streptococcus & Lactococcus)

Question 4

what do Staphylococcus & Micrococcus share in common

Answer 4

• possess aerobic metabolisms
• catalase positive
• resistant to desiccation and tolerate very high salt concentrations
• very common skin-associated bacteria

Question 5

what are some features of lactic acid bacteria

Answer 5

• non-spore forming
• come in rods and cocci
• aerotolerant
• fastidious - have very complex nutritional requrements (can’t make some of the materials they need within the cell)

Question 6

what is the difference between homofermenters and heterofermenters

Answer 6

homo - simply make lactic acid
hetero - make things in addition like ethanol and carbon dioxide

Question 7

what does Streptococcus pyogenes cause

Answer 7

necrotizing fasciitis

Question 8

what does Streptococcus pneumoniae cause

Answer 8

pneumonia and strep throat

Question 9

what does Bacillus anthracis cause

Answer 9

anthrax

Question 10

what is Bacillus thuringiensis active against

Answer 10

• insect larvae
• toxic for insect digestive tracts
• their digestive tracts cleave crystalline protoxin and it acts like broken glass

Question 11

what is Bt toxin

Answer 11

the proteolytically cleaved protein in insect digestive tracts (Bacillus thuringiensis)

Question 12

what is the structure of the spore bodies of Bacillus thuringienses

Answer 12

• there is an endospore surrounded by a parasporal body
• crystalline prototoxin (“cry protein”) is produced within the parasporal body

Question 13

what are some features of Clostridium

Answer 13

• strict anaerobes
• produce spores
• Gram-positive
• completely rely on fermentation - a variety of substrates

Question 14

what causes botulism

Answer 14

• Clostridium botulinum
• both toxin and spores are dangerous to inhale or ingest
• can be useful at low concentrations, causing localized flaccid paralysis (Botox)

Question 15

which bacterium causes tuberculosis and leprosy

Answer 15

Mycobacterium tuberculosis, Mycobacterium leprae

Question 16

what are some features of Mycobacterium

Answer 16

• difficult to stain, need to force stain in with heat
• have mycolic acids in their cell wall - extremely hydrophobic lipids
• very resistant to the penetration of chemicals
• colonies have a wax-like appearance

Question 17

what are some features of actinobacteria

Answer 17

• highly filamentous
• grow as branching mycelia
• produce desiccation-resistant spores called conidia
• produce and secrete terpene compounds known as geosmins when they produce spores
• prolific producers of antibiotics

Question 18

what are some features of cyanobacteria

Answer 18

• Gram-negative
• most are oxygenic phototrophs
• come in all kinds of shapes and sizes
• found everywhere
• most are photosynthetic and have chlorophyll A to capture light energy
• some produce cyanotoxins
• form heterocysts

Question 19

what pigments are in cyanobacteria

Answer 19

phycocyanins (blue) & phycoerythrins (red)

Question 20

what are heterocysts

Answer 20

• differentiated forms of cyanobacterial cells that some filamentous cyanobacterial species can produce
• lack the oxygen-evolving photosystem II

Question 21

what is the purpose of heterocysts

Answer 21

to conduct nitrogen fixation

Question 22

why do heterocysts have thick cell walls

Answer 22

to exclude oxygen, protecting the nitrogenase

Question 23

what is the exchange between heterocysts and vegetative cells

Answer 23

• heterocysts fix nitrogen into ammonia which is then assimilated into amino acids and distributed to vegetative cells
• vegetative cells