Researchers discover and cultivate a new group of deep-sea Chloroflexus that can perform photosynthesis

Recently, the microbiology journal mBio released the research results of Sun Chaomin's research group from the Institute of Oceanography, Chinese Academy of Sciences on the pure culture of the deep-sea refractory microorganism-Chloroflexi bacteria and its special energy metabolism method for obtaining light energy through photosynthesis, which is a breakthrough.
The culture bottleneck of difficult-to-cultivate microorganisms in the deep sea provides an effective means and provides research materials for in-depth understanding of the special life processes of important microbial groups in the deep sea
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Chloroflexobacteria, formerly known as "green non-sulfur bacteria", are a highly diverse group in the bacterial domain
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The members of Chloroflexbacteria are widely distributed in marine ecosystems, and their abundance is very high, but there are only a handful of taxa cultivated in deep-sea habitats, which are typical difficult-to-cultivate microorganisms, and their biological characteristics are basically blank at home and abroad
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At present, members of Chloroflexi are divided into 9 classes (including 14 orders, 19 families, 34 genera, and 56 species), some of which contain only 1 species, which indicates that most members of Chloroflex Pure culture has not yet been obtained, and it is urgent to establish an innovative isolation and culture method to obtain more Chloroflexus
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In this study, a batch of Chloroflexus was enriched and cultured by adding rifampicin to the basal medium.
Through continuous subculture, 3 pure cultures of Chloroflexus were finally obtained
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Among them, one strain of Chloroflexus (named Phototrophicus methaneseepsis ZRK33) belongs to the tentative class Thermofonsia branch 2, which is speculated to be a new type of photosynthetic bacteria, but it has not been confirmed due to the lack of pure culture strains
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After obtaining a pure cultured strain, the researchers confirmed that the strain was a representative strain of a new taxa by means of 16S rRNA gene and genome evolution analysis
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Genome sequencing found that the deep-sea Chloroflexus strain has a complete photosynthesis pathway, suggesting that it may have the potential to utilize light energy
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Further experiments showed that different light, especially red light, could promote the growth of this strain, confirming its characteristic of utilizing light energy
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Using transcriptomic methods, it was revealed that the expression of a series of key factors related to photosynthesis in the genome of this strain was significantly increased under red light irradiation, confirming that it utilizes light energy through photosynthesis
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As a deep-sea microorganism, can this strain of Chloroflexus also perform photosynthesis in deep-sea habitats? The researchers cultivated the Chloroflexus in the deep sea for 10 days through the advanced device of the "Science", and combined transcriptomic methods to confirm that the strain is indeed capable of photosynthesis in deep-sea habitats, and confirmed the presence of photosynthesis pathways by metagenomic methods.
Chloroflexus is widely distributed in deep-sea hydrothermal fluids and cold springs, indicating that deep-sea Chloroflexus is an important group of light energy utilization
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In recent years, the team has successively discovered non-photosynthetic bacteria that utilize light energy through minerals, photosensitive proteins and photoreceptor proteins
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There is growing evidence that different forms of geoluminescence or bioluminescence exist not only in deep-sea hydrothermal areas, but also in other deep-sea habitats (eg, cold springs) (closer to 80% of deep-sea animals can emit light)
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Therefore, in future research, more deep-sea microorganisms that can utilize light energy should be cultivated, the mechanism of light energy utilization should be analyzed, new light energy utilization pathways should be discovered, and the contribution of microorganism-mediated light energy metabolism in the deep-sea energy cycle should be evaluated
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The research was jointly funded by the Strategic Pilot Science and Technology Project of the Chinese Academy of Sciences, the Oceanographic Association's "Deep Sea Biological Resources Plan", and the Frontier Deployment Project of the Oceanographic Research Center of the Chinese Academy of Sciences
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Based on the selection pressure of rifampicin, a deep-sea Chloroflexus was isolated.
The newly isolated Chloroflexus is a representative strain of a new order.
The new group of Chloroflexus has typical characteristics of photosynthetic microorganisms in the laboratory and in situ in the deep sea.
Photosynthetic properties of Chloroflexus are widely distributed in deep-sea cold springs and hydrothermal habitats Source: Institute of Oceanography, Chinese Academy of Sciences