Nature fist review (IF=60) Shantou University’s Lu Zheng and other systems introduced when anaerobic bacteria encounter oxygen: oxygen toxicity, tolerance and defense mechanism

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The defining feature of iNature obligate anaerobes is that oxygen hinders their growth, but the underlying mechanism is still unclear
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A popular hypothesis is that these microorganisms have failed to evolve defenses to protect themselves from reactive oxygen species (ROS) such as superoxide and hydrogen peroxide, and this failure is what prevents them from expanding into oxygenated habitats.
Reason
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However, studies have shown that anaerobic bacteria actually have most of the same defense capabilities as aerobic bacteria, and many of them have the ability to tolerate large amounts of oxygen
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Therefore, in order to understand the structure of the microbial community and the dynamics of the real world, researchers have studied how anaerobic bacteria such as Bacteroides, Desulfovibrio, Pyrococcus, and Clostridia respond to changes in oxygen
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The hypoxic environment in which these organisms live-including mammalian intestines, sulfur vents, and deep deposits-experience intermittent oxidation
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On June 28, 2021, Shantou University Lu Zheng and others published an online review article titled "When anaerobes encounter oxygen: mechanisms of oxygen toxicity, tolerance and defence" in Nature Reviews Microbiology (IF=60.
33).
The review discussed oxygen The molecular mechanism that damages anaerobic bacteria and the extent to which the bacteria protect their metabolic pathways from their influence
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The emerging view of anaerobic is that the best strategy for anaerobic metabolism depends on free radical chemistry and low-potential metal centers
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This catalytic site is inherently susceptible to the direct toxicity of molecular oxygen and ROS
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Observations indicate that anaerobic bacteria have evolved strategies to either minimize the extent to which oxygen disrupts their metabolism or restore function shortly after the stress has dissipated
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The earth’s primitive atmosphere is actually hypoxic, and its molecular oxygen (O2) content is lower than the current level
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It is under this situation that life appeared 3.
8 billion years ago (Ga), and the basic biochemical mechanisms and metabolic pathways of organisms were established here
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Photosystem II appeared about 300 million years ago; it enables archaea to obtain reducing equivalents from water, thereby freeing photosynthetic microorganisms from dependence on electron sources such as hydrogen and hydrogen sulfide
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It also produces molecular O2 as a by-product
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Since O2 passes through the cell membrane at a high rate, early users of the photosystem will not be affected by the increase in O2 levels in the cell
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In addition, O2 diffused from these cells is chemically removed through abiotic reactions with environmental reducing agents, especially dissolved ferrous and sulfur substances.
For the next 100 million years, the ocean and the atmosphere are still deprived of oxygen
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However, by 250 million years ago, molecular O2 levels gradually increased
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O2 in the atmosphere stabilized at about 10% of contemporary levels, and then finally rose again from 80 million years ago
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In response to this opportunity, the anaerobic respiratory chain of some bacteria has evolved so that they can use O2 as a new electron acceptor
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Another microbial population maintains their anaerobic metabolism, and their contemporaries live in sediments and intestinal habitats in hypoxic and hypoxic zones
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These environments effectively isolate oxygen through the violent respiration of aerobic and facultative anaerobic bacteria in adjacent layers
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These anaerobic bacteria are known for their inability to maintain their core metabolism when exposed to O2
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Microbiologists can easily conclude that these anaerobic bacteria have failed to evolve with the oxidation of the earth, and this failure is the reason why they are restricted to the hypoxic microenvironment
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One of the goals of this review is to correct the idea that anaerobic microorganisms actually share most of the oxidative defenses with their aerobic microorganisms
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Instead, their long-lasting O2 sensitivity is a by-product of the chemical type that optimizes anaerobic energy production
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This review explored the molecular mechanisms by which oxygen damages anaerobic bacteria and the extent to which bacteria protect their metabolic pathways from its effects
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The emerging view of anaerobic is that the best strategy for anaerobic metabolism depends on free radical chemistry and low-potential metal centers
.

This catalytic site is inherently susceptible to the direct toxicity of molecular oxygen and ROS
.

Observations indicate that anaerobic bacteria have evolved strategies to either minimize the extent to which oxygen disrupts their metabolism or restore function shortly after the stress has dissipated
.

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