For the first time, scientists have sequenced the genome of a mysterious giant bacterium that can be seen without a microscope.
Discoveries about their reproductive strategies, survival mechanisms, and unique metabolic mechanisms (similar to mitochondria) may one day be useful in developing sustainable energy technologies and improving agricultural efficiency.
In a tropical marine environment, the bacillus spp. lives symbiotically in the internal organs of a type of fish. Most bacteria are too small to be seen without a microscope, and these single-celled "mammoths" are a million times larger than their well-known close cousin, E. coli, meaning they can be identified with the naked eye.
Esther Angert, a microbiologist at Cornell University in the United States, said: "This incredible giant bacterium is unique and interesting in many ways. Revealing the genomic potential of this creature amazed us. ”
The first member of the genus epulopiscium was discovered in 1985, and the name comes from the Latin words for "guest" and "fish".
Angel and her American colleagues named the species they studied "epulopiscium viviparus": the second word refers to reproduction that leads to live births.
Bacteria usually split in half, giving rise to two new cells, and "epulopiscium viviparus" can replicate up to 12 of itself inside the parent cell and then swim out into the outside world.
Unable to be cultivated in the laboratory, this giant bacterium remains a treasure of the biological world. Therefore, in order to study "epulopiscium viviparus", researchers must catch the fish in which it lives and carefully collect the cells as quickly as possible for DNA sequencing and transcriptome analysis.
Most bacteria either use oxygen to breathe or obtain energy from the environment through fermentation, which usually results in less energy production.
"Epulopiscium viviparus" happens to be a leavening culture, but it's confusing because it's huge, multiplies quickly, and can swim – all of which require relatively large amounts of energy.
It seems that the bacteria have optimized their metabolism and adapted to the sodium-rich fish intestinal environment. The flow of sodium ions across the cell membrane creates a powerful "sodium power" that is used to make energy and rotates their hair-like appendages, flagella, in order to move.
This sodium motility also powers flagellar movement in Vibrio cholerae, the bacterium that causes cholera.
The team also found that a large part of the genetic code of "epulopiscium viviparus" can make enzymes that efficiently extract nutrients from host fish, especially carbohydrates known as polysaccharides from algae.
Epulopiscium viviparus also has a large number of enzymes that make ATP, which is the "energy currency" that supports a variety of cellular processes. They found space for these molecules in a unique membrane that resembles the mitochondria of more complex organisms.
"We all know the phrase 'mitochondria are the power stations of the cell,' and surprisingly, these membranes of 'epulopiscium viviparus' have the same pattern as mitochondria," Anjet said. ”
They have a highly folded membrane that increases the surface area where these energy-generating pumps work, while the increased surface area creates a powerful energy. ”
Epulopiscium viviparus" is an effective way to harness algae nutrients that may have many uses in the future. Algae is becoming increasingly popular as a renewable energy source, food for livestock and humans** because it grows without interfering with terrestrial agriculture.
However, there are still some unsolved mysteries. As Angel and colleagues point out, further research is needed to fully understand how "epulopiscium viviparus" uses its enzyme library. This provides a solid foundation for understanding their growth needs.
"It's remarkable that we found that the largest known bacterium to date has not been isolated," the authors wrote. This suggests that bacterial behemoths are highly tuned to survive in the environment in which they evolved. ”
The study was published in the Proceedings of the National Academy of Sciences.
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