Quiz 2 practice questions

Question 1

What bacterial phyla are known to contain sulfate reducers?

Answer 1

proteobacteria and firmicutes

Question 2

What bacterial phyla contain dissimilative sulfur reducers?

Answer 2

proteobacteria

Question 3

What are some ecological strategies that sulfur oxidizers use to compete with chemical oxidation of H2S? (3)

Answer 3

1. O2 dependent positioning (beggiatoa)
2. anaerobic vacuole (thiomargarita)
3. symbiotic association

Question 4

What mechanisms do free-living diazotrophs use to protect nitrogenase from oxygen?

Answer 4

1. microaerophilic lifestyle
2. specialized protective cells
3. increased respiration and conformational protection
4. alternative nitrogenase

Question 5

What are the difference between ammonia and nitrite oxidizers? What about comammox?

Answer 5

Ammonia oxidizers (AOB and AOA) use ammonia as energy source and oxidize it to nitrite while nitrite oxidizers (NOB) complete nitrification step using nitrite as energy source, oxidizing it to nitrate.

Comammox uses ammonia and completely oxidizes it to nitrate

Question 6

What habitat characteristics govern the diversity & distribution of iron oxidizers?

Answer 6

At neutral pH with low oxygen iron precipitates, while at low pH iron is stable in the reduced form.

Therefore, they evolved to live at low pH

Question 7

What key enzyme is necessary for growth of chemolithotrophs on H2 as electron donor?

Answer 7

hydrogenase

Question 8

What is the difference between and methanotroph and a methanogen?

Answer 8

methanotrophs= use methane as carbon/ energy source

methanogens produce methane as a metabolic product

Question 9

What is unique about the methanotroph Methylomirabilis oxyfera?

Answer 9

This organism uses oxygen only as the activator of MMO, while it respires anaerobically

Question 10

What environmental conditions trigger fruiting body formation in myxobacteria?

Answer 10

Nutrient stress/ other stress- related conditions

Question 11

What are the different ways in which species of Myxococcus and Bdellovibrio kill their prey?

Answer 11

Bdellovibrio is periplasmic predator while Myxococcus is social predator

Question 12

How does binary fission differ from the division process in Caulobacter?

Answer 12

In Caulobacter cell division assumes production of 2 types of cells, swarmer with flagellum and stalked cell, which is opposite from typical binary fission that results in two identical cells.

Question 13

What benefit do magnetic bacteria accrue from having magnetosomes? What is energy source in these organisms?

Answer 13

Thanks to the iron oxides in magnetosomes, cells are aligning and migrate together toward specific oxygen gradient. Function of magnetosomes – oxygen sensing. Energy source would be reduced iron

Question 14

What molecules and enzyme are required for an organism such as Aliivibrio to emit visible light?

Answer 14

Enzyme luciferase produces light, alcohol and water, and the induction of light emission occurs due to the quorum sensing molecules AHL.

Question 15

What is quorum sensing and how does it control bioluminescence?

Answer 15

Quorum sensing is mechanism that bacteria use to attract each other in stressful conditions (mode of communication between bacteria) and is controlled by AHL inducers that are secreted by bacteria, diffuse through membrane of other relatives bacteria and induce lux genes to produce luciferase that emits light.

Question 16

Compare and contrast the metabolism, morphology, and phylogeny of purple sulfur and purple nonsulfur bacteria

Answer 16

Purple Sulfur Bacteria
- H2S to run photosynthesis
- S0 granules inside the cell
- CO2 fixation

Purple Non-Sulfur Bacteria
- Light is source of energy
- Organic compounds source of carbon

Question 17

Which bacterial phyla contain phototrophs?

Answer 17

Anoxygenic – Acidobacteria, Chlorobi, Chloroflexi, Firmicutes, Proteobacteria

Oxygenic – only Cyanobacteria

Question 18

. In what ways are sulfur-reducing bacteria different from sulfate reducing bacteria and in what ways are they similar?

Answer 18

Similar are because they both use H2 or organic compounds as electron donors, but different because sulfur reducers cannot do fermentation

Question 19

List three species of Betaproteobacteria that are known to be human pathogens

Answer 19

Neisseria meningitidis, Neisseria gonorrhoeae, and Burkholderia cepacia

Question 20

What species of Pseudomonas is a common cause of lung infection in cystic fibrosis patients?

Answer 20

Pseudomonas aeruginosa

Question 21

List types of hemolysis and one organism that performs complete hemolysis. How we distinguish different types of hemolysis?

Answer 21

Alpha, beta, and gamma hemolysis. We distinguish different types of hemolysis based on morphology on blood agar plate. Beta is complete hemolysis, Alpha is incomplete and gamma is the absence of hemolysis. Bacteria that performs complete hemolysis is Streptococcus pyogenes

Question 22

What four metabolic traits are most common in species of Deltaproteobacteria?

Answer 22

Sulfur reduction, sulfate reduction, iron reduction and predator life style

Question 23

How do heterofermentative and homofermentative bacteria differ physiologically?

Answer 23

Homofermentative organisms produce only lactic acid or ethanol, while heterofermentative organisms produce mixture of lactic acid, ethanol, and H2 and CO2.

Question 24

How can Streptococcus pyogenes be distinguished from viridans?

Answer 24

S. pyogenes performs complete hemolysis while S. viridans doesn’t

Question 25

What is the major physiological connection between Bacillus and Clostridium species?

Answer 25

They both produce endospore and they are both Firmicutes.

Question 26

What is the crystalline protein made by Bacillus thuringiensis and what is its significance to agriculture?

Answer 26

The genes for the B. thuringiensis crystal protein (Bt toxin) have been in Bacillus and is used to genetically modify plants to be insect resistant. Bt toxin is toxic for insect.

Question 27

Why do mycoplasmas need to have stronger cytoplasmic membranes than other bacteria?

Answer 27

Because they lost ability to create cell wall due to the parasitic life style.

Question 28

What organism is involved in the production of Swiss cheese, and what products does it make that help to flavor the cheese and make the holes?

Answer 28

Propionic acid bacteria, and CO2 produced in its fermentation enables holes in cheese.

Question 29

Why might antibiotic production be of advantage to streptomycetes?

Answer 29

Because it is soil organism and must be able to survive in complex environment.

Question 30

What is the role of Bacteroides in the human gut?

Answer 30

Bacterial enzymes from Bacteroidetes increases the diversity of plant polymers that can be degraded in the human digestive tract (healthy microbiome).

Question 31

What is the difference between an elementary body and a reticulate body?

Answer 31

Elementary body is dense and only for transmission, while reticulate body is lest dense and serves only for replication (non infectious)

Question 32

How are Chlamydia and Mycoplasma similar? How are they different?

Answer 32

They both do not have cell walls, but Chlamydia have more parasitic life style and belong to different phyla (Mycoplasmas are Tenericutes).

Question 33

How does the stalk of Planctomyces differ from the stalk of Caulobacter?

Answer 33

Caulobacter has stalk with cytoplasm, while Planctomycetes have more protein-style stalk.

Question 34

What is unusual about the bacterium Gemmata?

Answer 34

They have DNA covalently closed, circular, and supercoiled form (prokaryotic), and packed in pirellulosomes (resembles eukaryotic nucleus). DNA is highly condensed and partitioned from the remaining cytoplasm by a true unit membrane.

Question 35

What is unique about the genome of Thermotoga and the lipids of Thermodesulfobacterium?

Answer 35

Genome of Thermotoga has high homology with archaea, and lipids of Thermodesulfobacterium are ether-linked as in archaea.

Question 36

Describe an unusual biological feature of Deinococcus radiodurans

Answer 36

The most radiation-resistant organism that survives 5,000 grays (Gy) (humans 5Gy, E. coli 800 Gy). Mechanism of resistance is very active DNA repair system.

Question 37

How do Nitrospira and Deferribacter differ in terms of lifestyle and metabolism?

Answer 37

Nitrospira uses nitrite and respires oxygen, and Deferribacter respires oxidized iron Fe3+ and can use alternative electron donors.