Microbial diversity

Question 1

what do gram-positive bacteria have

Answer 1

a uniformly dense cell wall consisting primarily of peptidoglycan. Its purple

Question 2

what do gram-negative bacteria have

Answer 2

a very thin peptidoglycan layer and an outer membrane, which together make up cell envelope

Question 3

Firmicutes

Answer 3

low GC Gram-positives
* Derive name from relatively low ratio of G-C to A-Tnucleotide base pairs in their DNA
* Note that some are Gram-negative
* Some organisms have no cell wall, e.g. Mycoplasmas

Question 4

Actinobacteria

Answer 4

• Derive name from relatively high ratio of G-C to A-Tnucleotide base pairs in their DNA
• Gram-positive
• Filamentous growth form

Question 5

Firmicutes
Endo-spore forming bacteria

Answer 5

Generally rod-shaped
Form spores under a nutrient limitation or other adverse conditionsResistant to heat and other stresses
Can remain dormant for long periods

Question 6

Firmicutes
Non-spore-forming bacteria

Answer 6

Cocci in clusters
Can remain dormant for long periods20-40% normal adults50-70% hospitalized adults
Can cause skin, respiratory, intestinal, and wound infections
Can cause life threatening infections

Question 7

Proteobacteria

Answer 7

• Largest bacterial group
• Gram-negative cell structure
• Diverse metabolism although grouped together phylogenetically
• Many well-known organisms, e.g. E. coli and Salmonella Typhimurium

Question 8

Five Major Classes

Answer 8

• Alphaproteobacteria
• Betaproteobacteria
• Gammaproteobacteria
  *Deltaproteobacteria
• Epsilonproteobacteria

Question 9

Alphaproteobacteria

Answer 9

• Endosymbionts
  – N2-fixers in plant roots
  – e.g. Rhizobium
• Rickettsias
  – intracellular pathogens
  – includes protomitochondrion
  – e.g. Rickettsia rickettsii
• causes Rocky Mountain spotted fever
• spread by ticks

Question 10

Betaproteobacteria

Answer 10

• Photoheterotrophs: Rhodocyclus
• Chemolithotrophs
  – nitrifiers oxidize ammonia to nitrite
• Nitrosomonas, used in wastewater treatment
  – sulfur and iron oxidizers
• Acidithiobacillus
• Pathogens
  – Neisseria gonorrhoeae (humans)
  – Burkholderia cepacia (animals and plants)

Question 11

Gammaproteobacteria

Answer 11

Several medically and ecologically important groups of bacteria

• Sulfur and iron phototrophs
  – e.g. Chromatium spp.
  – single-flagellated rods
  – use sulfide and produce sulfur
  – deposited as cytoplasmic granules
• Sulfur chemolithotrophs
  – e.g. Beggiatoa spp.
  – Filamentous, gliding
  – oxidise H2S to sulfur
  – periplasmic granules

Question 12

Deltaproteobacteria

Answer 12

Include aerobic fruit-body forming Myxobacteria, e.g. Myxococcus xanthus
* Soil bacteria that can grow as isolated cells or aggregate into fruit bodies
* Can disperse spherical myxospores

Also includes Sulfate-reducing bacteria
* strict anaerobes
* produce sulfide
* e.g. Desulfovibrio spp