Bacterial Metabolism: Aerobes and Anaerobes

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Questions and Answers

Describe how sulfate-reducing bacteria contribute to corrosion in iron sewer pipes.

Sulfate-reducing bacteria produce H₂S, which reacts with iron to form iron sulfide, leading to corrosion.

Outline the role of leghemoglobin in the context of nitrogen-fixing bacteria within root nodules.

Leghemoglobin binds oxygen, maintaining a low oxygen concentration in the root nodule. This prevents the inactivation of nitrogenase, which is sensitive to oxygen.

How do mixotrophs utilize dual metabolic schemes, and provide an example from the material?

Mixotrophs use both autotrophic and heterotrophic metabolism, switching between them based on environmental conditions. An example are purple and green nonsulfur bacteria, which are anaerobic phototrophs in light and aerobic chemotrophs in dark.

Explain how increased respiration rate is linked to nitrogen fixation in Azotobacter.

<p>Azotobacter increases its respiration rate to consume available oxygen, creating a microaerobic environment that protects the oxygen-sensitive nitrogenase enzyme.</p> Signup and view all the answers

Describe how Deinococcus radiodurans resists high levels of radiation.

<p><em>Deinococcus radiodurans</em> resists radiation through multiple chromosomal copies that allows duplicate genes for repair, DNA repair enzymes shielded by Mn+2-phosphate-peptide complex and DNA scaffolded so that repair can occur efficiently.</p> Signup and view all the answers

Compare and contrast the roles of sulfate-reducing bacteria and sulfur-oxidizing bacteria in the sulfur cycle.

<p>Sulfate-reducing bacteria reduce sulfate to hydrogen sulfide (H₂S), while sulfur-oxidizing bacteria oxidize sulfur or H₂S to sulfate.</p> Signup and view all the answers

Why is Pseudomonas able to occupy diverse metabolic niches?

<p><em>Pseudomonas</em> has a versatile metabolism and so is better to be adaptable than fit for one particular environment.</p> Signup and view all the answers

Describe two mechanisms nitrogen-fixing bacteria utilize to protect nitrogenase from oxygen damage.

<p>They can consume O₂ as terminal electron acceptor and/or form a stable complex with Fd (“switch off”) to protect Fe-S.</p> Signup and view all the answers

Outline the role of the Ti plasmid in Agrobacterium's interaction with plants.

<p>The Ti plasmid contains genes that <em>Agrobacterium</em> transfers into the plant cell, causing the plant to produce food for the bacterium (specifically for the bacteria).</p> Signup and view all the answers

How do bacteria contribute to the process of biomining? Give one example from the reference material.

<p>Bacteria can be used to oxidize or reduce metals, transforming them into soluble forms that can be leached from ores. For example, Mn(IV) ores are bacterially reduced to soluble Mn(II) through bioleaching, then precipitated again by <em>Pseudomonas</em>.</p> Signup and view all the answers

What is the role of methanogens in anaerobic environments, and what byproduct are they most known for producing?

<p>Methanogens reduce CO₂ using H₂ as an electron donor, producing methane gas (CH₄).</p> Signup and view all the answers

Describe the unique hunting strategy of Bdellovibrio.

<p><em>Bdellovibrio</em> is a parasitic bacterium that attacks other gram-negative bacteria, invades the periplasmic space, and grows within the host cell.</p> Signup and view all the answers

What is the primary function of root nodules in plants, and which type of bacteria is typically found in them?

<p>Root nodules provide a protected environment for nitrogen-fixing bacteria. Bacteria of genera such as <em>Rhizobium</em> are typically found in them.</p> Signup and view all the answers

Name three bacterial genera that are important in food fermentation and describe a key product each creates.

<p><em>Clostridium</em> (ABE), Lactic acid bacteria (cheese, yoghurt, buttermilk), <em>Propionibacterium</em> (swiss cheese)</p> Signup and view all the answers

Outline the role of photoluminescence in Photobacterium (Vibrio) fischerii.

<p><em>Photobacterium (Vibrio) fischerii</em> produces light in response to crowded growth conditions, or high cell density.</p> Signup and view all the answers

Explain how denitrification contributes to the global nitrogen cycle, and what form of nitrogen is produced?

<p>Denitrification converts nitrate (NO₃⁻) back into nitrogen gas (N₂), returning nitrogen to the atmosphere.</p> Signup and view all the answers

Distinguish between endospores and cysts in bacteria, focusing on their roles in survival.

<p>Endospores are highly resistant, dormant structures formed inside certain bacteria that enable survival under harsh conditions. Cysts are durable, but not as durable as endospores. Cysts are formed by Azotobacter.</p> Signup and view all the answers

Explain how the activity of nitrifying bacteria can impact the biochemical oxygen demand (BOD) in water.

<p>Nitrifying bacteria consume oxygen as they convert ammonia (NH₄⁺) to nitrite (NO₂⁻) and then to nitrate (NO₃⁻), increasing the BOD and potentially depleting oxygen levels in the water.</p> Signup and view all the answers

Summarize the importance of the Haber-Bosch process, and how nitrogen-fixing bacteria provide an alternative.

<p>The Haber-Bosch process is an industrial nitrogen fixation method that converts atmospheric nitrogen into ammonia for fertilizer production. Nitrogen-fixing bacteria provide a natural, biological alternative to this process.</p> Signup and view all the answers

Describe the social behavior observed in Myxobacteria and its purpose.

<p><em>Myxobacteria</em> exhibit social motility, aggregating into fruiting bodies when nutrients are scarce. This allows them to survive and disperse spores more effectively.</p> Signup and view all the answers

Name the two genera of nitrogen-fixing bacteria.

<p><em>Azotobacteria</em> and <em>Rhizobium</em>.</p> Signup and view all the answers

Explain a key difference between chemolithotrophs and chemoorganotrophs.

<p>Chemolithotrophs obtain energy from inorganic compounds, while chemoorganotrophs obtain energy from organic compounds.</p> Signup and view all the answers

Explain how nitrogen fixation is performed in root nodules of plants.

<p>Nitrogen fixation in root nodules is performed in the root nodules by rhizobia, symbiotic nitrogen-fixing bacteria.</p> Signup and view all the answers

Explain how aerobic chemolithotrophs are utilized in biomining.

<p>Aerobic chemolithotrophs, like sulfur oxidizers, convert insoluble metal sulfides into soluble sulfates, facilitating metal extraction from ores.</p> Signup and view all the answers

What is the unique role that Caulobacter plays in marine environments?

<p><em>Caulobacter</em> has a cell cycle where only stalked cells replicate, which allows them to effectively colonize nutrient-poor aquatic environments by attaching to surfaces via their stalks.</p> Signup and view all the answers

How would the phylogenetic tree change if the microbial world was compared in terms of metabolisms than 16S RNAs?

<p>The phylogenetic tree would likely be very different because 16S RNA are used to group organisms by genotype, whereas metabolism is a phenotype. Thus, organisms distantly related, phylogenetically, may have converged to have similar metabolisms.</p> Signup and view all the answers

Why it is hard to do reverse genetics on Archaea?

<p>It's hard to do reverse genetics on Archaea because very few genetic transfer systems have been developed.</p> Signup and view all the answers

How do sulfur oxidizers contribute to the process of biomining?

<p>Sulfur oxidizers, such as <em>Acidithiobacillus</em>, oxidize metal sulfides in ores, releasing soluble metals that can be leached out.</p> Signup and view all the answers

Describe the unique cellular structure of Corynebacterium diphtheriae and its relevance to identification.

<p><em>Corynebacterium diphtheriae</em> exhibits a 'Chinese character' arrangement of cells due to its snapping division, a characteristic used for its identification.</p> Signup and view all the answers

What are the electron donors ans acceptors for chemolithotrophic anaerobes?

<p>Electron donors for chemolithotrophic anaerobes are H2 (sometimes methanol, acetate, formate) and electron acceptors are CO2 and methanol.</p> Signup and view all the answers

What are the products, reactants, and enzymes involved for bioleaching and biomining?

<p>The reactants are Au2S3 and the products are Au + H2SO4. The enzymes are made by Sulfur oxidizers.</p> Signup and view all the answers

Describe two ecological roles performed by extreme halophiles.

<p>Extreme halophiles contribute to nutrient cycling in high-salt environments and can play a role in the degradation of organic matter.</p> Signup and view all the answers

What is the role of Rhizobium with legumes?

<p>Rhizobium infects the root and produces root nodules. In exchange for nutrients, they fix nitrogen.</p> Signup and view all the answers

The bacteria are facultative anaerobes and have fac.an. G- rods, ferment glucose, motile by peritrichous flagella. What is Enterobacteriaceae (gut bugs)?

<p>Enterobacteriaceae are a family of bacteria that are facultative anaerobes and have fac.an. G- rods, ferment glucose, motile by peritrichous flagella.</p> Signup and view all the answers

What do Sulfolobus and hyperthemophiles do?

<p>Sulfolobus and hyperthermophiles are archaea that perform the same function in thermal hot springs.</p> Signup and view all the answers

What are some ways halophiles adapt in extreme environments?

<p>Halophiles have evolved to live in areas of high salt concentration (30% NaCl).</p> Signup and view all the answers

What are two reasons Deinococcus radiodurans is radiation resistant?

<p><em>Deinococcus radiodurans</em> as two reasons for it's radiation resistence. 1) DNA repair enzymes are shielded by Mn+2-phosphate-peptide complex and 2) has multiple chromosomal copies (at least 2) allow duplicate genes for repair</p> Signup and view all the answers

What are two purposes for soil bacteria?

<p>Soil bacteria serve purposes such as spore-formers, <em>Azotobacteria</em> (N2), <em>Myxobacteria</em>, and <em>Streptomyces</em> .</p> Signup and view all the answers

Describe what a chemoorganotroph would eat and give an example of bacteria that is an obligate aerobe.

<p>Chemoorganotrophs are organisms that obtain energy by oxidizing organic compounds. <em>Mycobacterium</em> is an obligate aerobe</p> Signup and view all the answers

How do Picrophilus and Ferroplasma protect itself at extreme PH values?

<p>Tough membranes or protein cell walls rather than PG, secrete basic molecules as pH buffers, actively pump out H+</p> Signup and view all the answers

Flashcards

Chemolithotrophs & Phototrophic Anaerobes

Anaerobes oxidize inorganic compounds or use anoxygenic photosynthesis.

Chemolithotrophs & Photosynthetic Aerobes

Aerobes that use inorganic compounds or oxygenic photosynthesis for energy.

Methanogens

Archaea that use H2 as an electron donor to reduce CO2, producing methane.

Sulfate Reducers

Bacteria that use sulfate as a terminal electron acceptor, producing H2S.

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Lactic Acid Bacteria

Fermentative bacteria used in cheese, yogurt, and buttermilk production.

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Propionibacterium

Fermentative bacteria involved in Swiss cheese production and acne.

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Purple Nonsulfur Bacteria

Anaerobes that use light for energy and organic compounds as electron donors.

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Sulfur Oxidizers

Oxidize sulfur compounds for energy; O2 is the electron acceptor.

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Nitrifying Bacteria

Bacteria that oxidize ammonia or nitrite.

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Biomining

Process of using microbes to extract metals from ores.

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Nitrogenase

Enzyme complex that reduces nitrogen gas to ammonia.

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Pseudomonas

Aerobic chemoorganotrophs with versatile metabolism and fluorescent pigments.

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Deinococcus

Bacteria highly resistant to radiation damage.

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Endospores

Durable, dormant bacterial cells that withstand harsh conditions.

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Cysts (Azotobacter)

Durable, but not heat resistant, dormant cells formed by Azotobacter.

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Myxobacteria

Bacteria exhibiting social motility, aggregating into fruiting bodies.

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Streptomyces

Filamentous bacteria producing many antibiotics.

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Caulobacter

Bacteria with a cell cycle, replicating only in stalked cells.

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Bdellovibrio

Parasitic bacteria that grows within the periplasm of Gram-negative bacteria.

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Photobacterium

Bacteria producing light in response to crowded growth conditions.

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Agrobacterium

Bacteria injecting DNA into plant cells to make food for itself.

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Rhizobium

Plant symbiont fixing nitrogen in root nodules.

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Halophiles

Organisms living in saturated brine (high salt) environments.

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Hyperthermophiles

Organisms inhabiting diverse, very high-temperature environments.

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Acidophiles

Organisms that grow at very low pH levels.

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Ti Plasmid

Plasmid used by Agrobacterium to transfer genes into plant cells.

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Mixotrophs

Mixotrophs use dual metabolic schemes for growth.

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Leghemoglobin Function

Leghemoglobin binds oxygen and keeps root nodules anaerobic.

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BOD Meaning

BOD measures organic matter in water.

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Study Notes

Classifying by Metabolism

  • Diverse metabolic styles exist among bacteria

Anaerobes

  • Include chemolithotrophs, chemoorganotrophs with a respiratory chain, chemoorganotrophs via fermentation, and phototrophic bacteria that perform anoxygenic photosynthesis.

Aerobes

  • Include chemolithotrophs, chemoorganotrophs which are obligate or facultative, and photosynthetic bacteria that perform oxygenic photosynthesis

Chemolithotrophic Anaerobes: Methanogens

  • Consist exclusively of Archaea
  • Utilize H2 (sometimes methanol, acetate, or formate) as an electron donor
  • Frequently co-cultured with H2-producing bacteria
  • Reduce CO2 or methanol as the electron acceptor
  • Produce methane

Chemoorganotrophic Anaerobes: Respiratory Chain - Sulfate Reducers

  • Often use organic compounds (or sometimes H2) as an electron donor
  • Reduce SO4-2 or S as the electron acceptor
  • Produce H2S (swamp odor and black goo in the presence of Fe+2)
  • Utilize organic carbon sources

Chemoorganotrophic Anaerobes: Fermenters

  • Several bacteria serve as fermenters
  • Clostridium is industrially important (ABE)
  • Lactic acid bacteria important in cheese, yogurt, and buttermilk production
  • Propionibacterium is used in the production of Swiss cheese and is linked to acne

Phototrophic Anaerobes

  • Purple sulfur bacteria accumulate intracellular S granules and utilize H2S as an electron donor.
  • Purple nonsulfur bacteria generally use organic electron donors and can be anaerobic phototrophs or aerobic chemotrophs
  • Green sulfur bacteria have external S granules
  • Green nonsulfur bacteria are anaerobic phototrophs in light and aerobic chemotrophs in the dark
  • Mixotrophy is when a microbe is an anaerobic phototrophs in light and aerobic chemotrophs in the dark

Aerobic Chemolithotrophs - Sulfur Oxidizers

  • They use S or H2S as an electron donor
  • O2 is their electron acceptor
  • They form internal S granules
  • They produce SO4-2 or H2SO4, and some live at pH 2
  • Bioleaching and biomining are examples, Au2S3 → Au + H2SO4

Aerobic Chemolithotrophs - Nitrifying Bacteria

  • NH4+ is the electron donor
  • O2 is the electron acceptor
  • Produce NO3-
  • NH4+ → NO2- (ammonia oxidizers) and NO2- → NO3- (nitrite oxidizers), some bacteria do both
  • High BOD is seen in NH4+-contaminated water
  • They break down ammonia wastes during sewage treatment

Bacteria and Biomining

  • Bacteria are used to reduce Mn(IV) ores to soluble Mn(II) in bioleaching
  • Pseudomonas can then oxidize Mn(II) back to Mn(IV)

Nitrogen Fixation

  • O2 inactivates nitrogenase by degrading oxidizing Fe-S cofactors
  • Bacteria can use O2 as a terminal electron acceptor to prevent inactivation
  • Bacteria can form a stable complex with Fd ("switch off") to protect Fe-S

Aerobic Chemoorganotrophs - Obligate Aerobes

  • Mycobacterium are acid-fast bacteria
  • Pseudomonas are metabolically versatile and produce fluorescent pigments
  • Deinococcus exhibits super-resistance to radiation damage

Aerobic Chemoorganotrophs - Facultative Anaerobes

  • Examples include Coryneforms (diphtheroids)
  • Enterobacteriaceae (gut bugs) that include G- rods, ferment glucose and motile via peritrichous flagella

Classifying by Habitat: Soil

  • Includes spore-formers
  • Azotobacteria (N2 fixers)
  • Myxobacteria
  • Streptomyces

Classifying by Habitat: Aquatic

  • Includes prosthecate bacteria
  • Bdellovibrio
  • Bioluminescent bacteria

Classifying by Habitat: Plants

  • Agrobacterium
  • Rhizobium (N2 fixers)

Classifying by Habitat: Animals

  • All pathogens

Classifying by Habitat: Extreme Environments

  • Halophiles
  • Thermophiles
  • Acidophiles

Spores vs Cytes

  • Endospores facilitate long-term survival in harsh environments
  • Azotobacter forms cysts (not endospores, but still durable) and "fixes" N2 to NH4+
  • Limits the nitrogenase being inactivated by fixing nitrogen with a high increase in respiritation to decrease 02

Myxobacteria

  • Exhibit social motility to aggregate into fruiting bodies

Streptomyces

  • Produce many antibiotics as secondary metabolites forming filaments that form chains

Caulobacter crescentus

  • Exhibits a cell cycle for replication
  • Only stalked cells replicate
  • Flagella and stalks form in opposite daughter cells

Bdellovibrio

  • Is a parasite of Gram-negative bacteria by growing and living withing the periplasm

Photobacterium (Vibrio) fischerii

  • Produces light as it grows in crowded conditions

Agrobacterium

  • Injects its DNA (Ti plasmid) into a plant cell to have the plant cell make food for the bacterium

Rhizobium

  • Is a plant symbiont that “fixes” N2 to NH4+
  • Forms root nodules
  • Lowers the concentration of oxygen to avoid interupting the nitrogrenase process

Extreme Halophiles

  • Can survive in saturated levels of brine such as 5M, or 30% NaCl

Hyperthermophiles

  • Inhabit the environment that consists of diverse regions, such as deep sea vents, and thermal springs
  • These environments contain H2 or organic electrons as donors, with sulfuric acid acting as the receptor to produce H2S
  • Lives in sync with organisms to use H2S as an electron

Picrophilus and Ferroplasma

  • Can grow at pH0, even though their ctyoplasm stands at pH 6-7
  • Has tough membranes and protein cell walls
  • Secretes basic molecules as pH levels to act as buffers
  • Pumps H+ actively

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