[ISME] Break the existing conclusions!

Recently, the research groups of Dong Xiuzhu and Zhou Yuguang of the Institute of Microbiology of the Chinese Academy of Sciences conducted research on strains of Flavobacterium glacialis collected from Tibet, Xinjiang, Gansu, Sichuan and other places, and found that a carotenoid called zeaxanthin helps them in hypoxia.
Using light energy to grow under low-nutrient conditions, this new discovery poses a challenge to the light-promoting growth mechanism of Flavobacterium rhodopsin-determining that has been generally believed in the world.

Related results were recently published in the "Journal of the International Society of Microbial Ecology".

"This will expand our understanding of the use of light by microorganisms as a means of energy, and also help explain a phenomenon that people often observe, that is, many microorganisms isolated from glaciers produce more pigments.

" The reviewer of the journal commented on this potential.
New light energy utilization mechanism.

Breaking the existing conclusions Photosynthesis is the basis for the survival of life on earth.

Pigments are the "organs" that capture sunlight energy during photosynthesis.

Plants, algae and some bacteria convert light energy into bioenergy through chlorophyll, and convert water, carbon dioxide, nitrogen compounds, etc.
into organic matter such as starch, fat, protein, and nucleic acid.

There are three main types of pigments known on the earth on which photonutrient metabolism depends: chlorophyll, carotenoids and phycobilidin.

For a long time, it has been generally accepted internationally that Proteobacterium rhodopsin is a functional protein of Flavobacterium that uses light energy.

Rhodopsin is a membrane-bound protein, which cannot be light-sensitive by itself, but needs to bind to retinal molecules (a carotenoid) to receive light energy.

"Retinal is actually an analog of vitamin A.

" Dong Xiuzhu, the corresponding author of the paper and a researcher at the Institute of Microbiology, said in an interview with the "Chinese Journal of Science".

Under the leadership of Dong Xiuzhu, the researchers conducted multi-omics studies on 47 strains of Flavobacterium glacialis collected from glaciers in Tibet, Xinjiang, Gansu, Sichuan and other places.

Genomic analysis revealed that 37 strains contained the proteus rhodopsin gene, and the other 10 strains did not contain the gene.

However, light growth experiments found that both the Flavobacterium carrying and ignoring the rhodopsin gene, or the strains with artificially knocked out the gene, showed the characteristics of light-promoting growth.

"From the gene expression profile of these research strains, the retinal synthesis gene is almost not expressed; nor has it been tested to synthesize retinal in these strains.

Therefore, we believe that photo-promoted growth should have nothing to do with rhodopsin.

" Dong Xiuzhu said.

This research has undoubtedly challenged previous views.

Zeaxanthin may promote the light growth of bacteria About 20 years ago, researchers discovered in the ocean that Flavobacterium carries rhodopsin protein that uses light energy to produce proton pumps, and gives Flavobacterium the use of light energy to adapt to a low-nutrient environment.

"If it is said that (the growth of Flavobacterium) has nothing to do with rhodopsin, then what does it have to do with glaciers under low oxygen and oligotrophic conditions?" Dong Xiuzhu and his collaborators continued to ask.

Further research, they found that the light-promoted growth of Flavobacterium glacialis is related to the synthesis of pigments such as zeaxanthin.

Β-carotenoids such as zeaxanthin and lycopene can provide light radiation protection for Flavobacterium glacialis and maintain cell membrane stability at low temperatures.
Flavobacterium glacialis that contains only yellow pigments cannot grow under light conditions.

"The author reported that light stimulates the growth of Flavobacterium glacialis to produce zeaxanthin.

Through physiological experiments, genome and transcriptome analysis, the authors discovered a new mechanism of light energy harvesting system similar to Flavobacterium glacialis.

" Article reviewer Liu Yongqin, a researcher at the Institute of Qinghai-Tibet Plateau of the Chinese Academy of Sciences, commented, "This topic is very interesting and the results are very convincing.

" "If this model is established, it will be another new light energy utilization mechanism (or at least Light-mediated conservation of energy).

” Another reviewer of the study said.

The reviewer expects to further clarify the photo-promoting mechanism of zeaxanthin in the future.

Building a "bank" of microbial resources Glaciers have always been a hot environment in the field of extreme microbiology, which contains abundant low-temperature microorganisms.
The glacier ecological environment has endowed glaciers with microbial species, genetics and metabolism diversity.

Taking zeaxanthin as an example, Dong Xiuzhu introduced that this is a polar carotenoid.

"Similar to the carotenoids in the carrots and tomatoes we eat, they are fat-soluble and are easier to absorb when fried in oil than directly eaten.

" She added.

The cell membrane of low-temperature bacteria is mostly composed of unsaturated fatty acids and has strong fluidity, which can ensure that the cell membrane does not solidify at low temperatures and communicate with the outside world.

But the cell membrane composed of unsaturated fatty acids is also easy to rupture.

Zeaxanthin, a polar carotenoid, is like a skeleton.
The molecular skeleton is partly embedded in the cell membrane, and the head is located outside the membrane, which strengthens the overall structure of the cell membrane at low temperatures and is not easy to rupture.

As the first domestic collection center certified by the international standard ISO9001, Zhou Yuguang, director of the General Microbiology Center (CGMCC) of the China Microbial Culture Collection Management Committee and director of the Culture Collection Center of the Institute of Microbiology, introduced that the three types of bacteria that CGMCC is currently responsible for preservation are—— Ordinary microbial strains, basic research strains, pathogenic microbial strains, the total strain resources are more than 80,000 strains, including more than 4000 strains of low-temperature bacteria isolated from 11 glaciers in my country, establishing my country's characteristic glacier low-temperature bacteria Strain resource library.

Glacial microorganisms are ideal resources for discovering new materials, new genes, new mechanisms and new functions.

The temperature difference between the north and the south of our country is large.
The use of high-medium-low temperature bacteria in temperature-adapted areas will bring great convenience to industrial and agricultural production.

For example, some low-temperature enzymes can improve the sterilization and decontamination ability of detergents in cold northern regions, and some low-temperature bacteria are also conducive to biogas fermentation in northern regions in winter and biodegradation and reuse of black soil in northeastern regions.

Zhou Yuguang gave an example.

"It is precisely because we have preserved these Flavobacterium well 8 years ago that we have the results of today's study.

" Dong Xiuzhu said.

The collection center is like a microbial "bank", collecting and storing microbial resources accumulated in scientific research, and providing researchers with in-depth study of biological characteristics, metabolic pathways and gene functions.

"Share on the basis of preservation and realize the sustainable use of microbial resources, so that the country's early investment can lay the foundation for follow-up research.
This is also the reason why the country has established such a non-profit public welfare platform.

" Zhou Yuguang said.

(Author: Dan Yang Zi Feng Li)