58 Questions
What is a common characteristic of Proteobacteria?
Contain an outer membrane with LPS
Which group of Proteobacteria includes sulfur and iron reducers?
Deltaproteobacteria
Which bacteria can be isolated from various environmental sources like sewage and marine water?
Bdellovibrios
What is a characteristic of Epsilonproteobacteria?
Pathogens that cause gonorrhea
What role do Deltaproteobacteria play in the ecosystem?
Breaking down sulfur and iron
What is the main benefit of the mutualism between plants and nitrogen-fixing rhizobia?
Rhizobia fix more nitrogen than plants absorb, increasing the soil's nitrogen content.
How do host plants and rhizobial bacteria recognize each other as suitable partners?
Through the exchange of signaling molecules like flavonoids
What is the role of Nod factors in the symbiotic relationship between legumes and rhizobia?
They help establish species specificity between bacterium and host.
What happens to bacteroids once they are surrounded by the plant cell envelope?
They are unable to reproduce.
Why do farmers often alternate crops like corn with soybeans?
To restore nitrogen to the soil
What is the main limiting nutrient for primary productivity in many natural ecosystems and forms of agriculture?
Nitrogen
Which process involves the conversion of ammonia (NH3) to nitrite (NO2-) and nitrate (NO3-)?
Nitrification
What is the main avenue for the entry of nitrogen into the biosphere?
Bacterial and archaeal nitrogen fixation
What is the form of nitrogen that is assimilated into biomass by microbes and plants?
Ammonium ion (NH4+)
Which microbial reaction involves the oxidation of ammonia to nitrite or nitrate?
Nitrification
Why is nitrogen fixation considered energy-intensive?
The need to exclude oxygen during the process
What is the major reason why nitrogen remains limiting in ecosystems despite being ubiquitous?
Insufficient fixation rate to meet ecosystem demand
Which process contributes to the acidification of soil during nitrogen fixation?
Nitrification
What role does denitrification play in terms of nitrate reduction in ecosystems?
Converts nitrate back to nitrogen gas (N2)
What is the consequence of heavy fertilization leading to excess nitrate in ecosystems?
Increased global warming due to N2O production
What type of media favours the growth of one organism over another?
Selective media
Which type of media exposes biochemical differences between two species that grow equally well?
Differential media
Why is a medium containing bile salts and crystal violet considered selective?
It favors the growth of Gram-negative over Gram-positive bacteria
When is a differential medium needed in microbiology?
To distinguish between organisms that differ in their ability to grow
What is the primary purpose of selective and differential media in clinical microbiology?
To promote the growth of specific organisms and highlight biochemical differences
Where is anaerobic Photosystem 1 (PS1) found?
Chlorobia and Chloroflexi
Which organisms contain bacteriorhodopsin and proteorhodopsin, which are light-driven proton pumps?
Haloarchaea
What do chlorophylls and bacteriochlorophylls do in photosynthesis?
Absorb light and transfer energy to an ETS
What is the function of the antenna complex in chlorophyll-based photosynthesis?
Absorb light for transfer to the reaction center
Where are thylakoids found?
Within phototrophic bacteria or chloroplasts
What is the source of electrons for Photosystem 1 (PS1)?
H2S
What does Photosystem 2 (PS2) use to generate ATP?
$H_2O$
What is the primary product of oxygenic photosynthesis?
$O_2$
What is the primary energy source for Aquificae members?
Hydrogen gas
Where was Thermotoga maritima originally isolated from?
Vulcano, Italy
What type of bacteria are Chloroflexus species?
Photoheterotrophs
Which bacteria are informally known as 'green nonsulfur bacteria'?
Chloroflexi
What is a notable characteristic of Deinococcus species?
High resistance to radiation
What specialized cells do cyanobacteria form to exclude oxygen for nitrogen fixation?
Heterocysts
Which structures enable cyanobacteria to float in the water column?
Gas vesicles
What is the specific purpose of carboxysomes in cyanobacteria?
Fixing CO2
Which strategy do cyanobacteria use to maintain anaerobic biochemistry while producing oxygen?
Alternating between photosynthesis and nitrogen fixation
In what way do cyanobacterial filaments and colonies resemble multicellular organisms?
By differentiating into heterocysts for nitrogen fixation
What is the defining characteristic of methanotrophs?
Ability to grow on methane
Which family of bacteria includes widely studied species like Escherichia coli?
Enterobacteriaceae
What is a common feature of many Enterobacteriaceae strains regarding oxygen?
They can grow with or without oxygen
Which bacterial group includes pathogens that can infect both plants and animals?
Gammaproteobacteria
Which feature is characteristic of Xanthomonas species among agricultural pathogens?
Colonization of a wide range of agricultural plants
What is a distinctive feature of the spirochete cell structure?
Long, tight spiral that is flexible like an old-style telephone cord
How does spirochete motility differ from regular bacterial motility?
Propelled by flexing motion caused by rotating periplasmic flagella
What is the primary energy source for spirochetes?
Fermentation
Where are the periplasmic flagella located in a spirochete cell?
In the periplasmic space around the plasma membrane
What is unique about the rotation of periplasmic flagella in spirochetes?
Forces the entire cell to twist around in a corkscrew motion
What enzyme is required for nitrogen fixation in cyanobacteria like Anabaena?
Nitrogenase
How do heterocysts enable cyanobacteria like Anabaena to fix nitrogen anaerobically?
By creating a low-oxygen environment
What is the term for the specialized cells developed by Anabaena to fix nitrogen?
Heterocysts
Why is the enzyme nitrogenase sensitive to oxygen?
Because it produces oxygen as a by-product of its function
What physiological activities do cyanobacteria like Anabaena carry out simultaneously due to heterocyst development?
Nitrogen fixation and photosynthesis
Explore the unique features of proteobacteria cell envelopes, such as the gram-negative outer membrane, peptidoglycan cell wall, and inner membrane. Learn about the role of porins in nutrient intake and antibiotic exclusion.
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