Bacterial sensors of oxygen
Many bacteria are facultative anaerobes, that is, they can grow in the presence or absence of O2. In contrast to anaerobic respiration or fermentation, O2 and aerobic respiration confer enormous energetic benefits on facultative bacteria by allowing the complete oxidation of a growth substrate and the concomitant conservation of much larger amounts of energy. Moreover, some energetically expensive processes such as nitrogen fixation are inhibited by O2. Furthermore, hypoxic conditions are a signal to adopt a different “lifestyle” for some bacteria such as the dormant state of Mycobacterium tuberculosis associated with latent TB infections. The ability to adapt to changes in O2 availability by expressing different groups of genes is controlled at the level of transcription by O2-sensing regulatory proteins.
Bacterial sensors of oxygen. Curr Opin Microbiol. Feb 24 2009
The concentration of molecular oxygen (O2) began to increase in the Earth’s atmosphere approximately two billion years ago. Its presence posed a threat to anaerobes but also offered opportunities for improved energy conservation via aerobic respiration. The ability to sense environmental O2 thus became, and remains, important for many bacteria, both for protection and switching between anaerobic and aerobic respiration. Utilizing an iron–sulfur cluster as the sensor of O2 exploits the ability of O2 to oxidize the iron–sulfur cluster, ultimately resulting in cluster disassembly. When utilizing heme as the sensor, the capacity of O2 to form a reversible Fe–O2 bond or alternatively the oxidation of the heme iron atom itself is used to detect O2 and switch regulators between active and inactive forms.
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Tags: Bacteria, Biology, Environment, Microbiology, Science
The evolution of facultative anaerobes also allowed Engelmann to perform his famous experiment revealing two photosynthetic systems in green plants. I’ve always thought of that as the first modern bioassay, and one of the most elegant experiments ever performed.
“Its presence posed a threat to anaerobes but also offered opportunities for improved energy conservation via aerobic respiration.” This feature is effectively utilized by our cells- mitochondria that is responsible for energy production, are endosymbionts.