Ch11 - The Diversity of Bacteria and Archaea
What is an anaerobic environment?
A broader term that includes environments where oxygen isn't used for metabolism, including anoxic environments
Why don't anoxygenic phototrophs produce O2 gas?
Because they use H2S or organic compounds instead of water as a source of electrons to make reducing power
Compare and contrast anoxic and anaerobic environments
Both environments do not support aerobic respiration which requires oxygen, and anoxic is under anaerobic
What is an anoxic environment?
An environment that lacks oxygen entirely
What were likely the earliest photosynthesizing organisms?
Anoxygenic phototrophs
What are methanogens?
Archaea that obtain energy by oxidizing H2 gas, using CO2 as a terminal electron acceptor, generating methane and ATP
Why can environments that are routinely exposed to O2 support anaerobic growth?
Because O2-consuming or aerobic organisms consume the available oxygen for their energy production processes, making conditions favorable for anaerobic organisms that can thrive where oxygen is depleted
Are the purple and green bacteria both gram-positive or gram-negative?
Gram-negative
What are hydrogen-oxidizing bacteria?
Gram-negative bacteria such as Aquifex and Hydrogenobacter that are obligate chemolithotrophs and thermophilic
What are nitrifiers?
Gram-negative bacteria that obtain energy by oxidizing inorganic nitrogen compounds such as ammonium or nitrite.
What are cyanobacteria?
Gram-negative oxygenic phototrophs; genetically related to chloroplasts, and are capable of both photosynthesis and nitrogen fixation
What are sulfur-oxidizing bacteria?
Gram-negative rods or spirals that obtain energy by oxidizing elemental sulfur and reduced sulfur compounds, generating sulfuric acid.
What are lactic acid bacteria?
Gram-positive bacteria that generate lactic acid as a major end product of their fermentative metabolism.
What color are the gram-negative green bacteria usually?
Green or brownish
Where are anaerobes regularly found in healthy individuals?
Oral cavity, skin, and intestinal tract
What role do H2 gas and CO2 play in the metabolism of methanogens?
Methanogens are found in anaerobic environments where both H2 and CO2 are available; H2 is used as an electron donor, and CO2 is used as a terminal electron acceptor and carbon source
What are chemotrophs?
Organisms that obtain energy by oxidizing chemical compounds
What are chemolithotrophs?
Organisms that obtain energy by oxidizing inorganic chemical compounds
What are chemoorganotrophs?
Organisms that obtain energy by oxidizing organic chemical compounds such as glucose, and often use sulfur or sulfate as a terminal electron acceptor
What are anoxygenic phototrophs?
Photosynthetic organisms that do not produce O2 gas
What are the different types of anoxygenic phototrophs?
Purple bacteria, green bacteria, and gram-positive endospore forming rods of the genus heliobacterium
What colors can the gram-negative purple bacteria appear due to their light-harvesting pigments?
Purple, red, or orange
What does the metabolism of hydrogen-oxidizing bacteria involve?
Using hydrogen as a source of energy and oxygen as a terminal electron acceptor, producing water
What are heliobacterium?
They are gram-positive, endospore forming rods related to members of the genus Clostridium
Where are the components of the photosynthetic apparatus located in purple bacteria?
Unlike in other anoxygenic phototrophs, in purple bacteria, the components of the photosynthetic apparatus are all located in the cell's plasma membrane.
What does an anaerobic chemoorganotroph use for energy and as a terminal electron acceptor when performing fermentation versus anaerobic respiration?
When performing fermentation, glucose and pyruvate are used, and when performing anaerobic respiration, glucose is also used but an ionorganic compound is used for the terminal electron acceptor like nitrate or sulfate or CO2
