Micrograph of a group of Epulopiscium viviparus bacteria. Credit: Esther Angert / Cornell University
A collaborative research endeavor has recently fully described the genome of a family of large bacteria named Epulopiscium, unveiling a unique method of energy production to fuel their extreme metabolic needs. The bacteria, which are large enough to be seen by the human eye, were first discovered in 1985 and live symbiotically within the intestinal tracts of surgeonfish.
In the study, published in Proceedings of the National Academy of Sciences, a collaborative team of researchers from Cornell and Lawrence Berkeley National Laboratory has fully described the genome of one species of Epulopiscium which they have named Epulopiscium viviparus.
This incredible giant bacterium is unique and interesting in so many ways: its enormous size, its mode of reproduction, the methods by which it meets its metabolic needs and more," said Esther Angert, professor of microbiology. "Revealing the genomic potential of this organism just kind of blew our minds."
While most bacteria reproduce by dividing themselves in half to create their offspring, E. viviparus create up to 12 copies of themselves which all grow in a parent cell before being released. E. viviparus also face unique metabolic challenges, requiring large amounts of energy to power them. While many bacteria rely on fermentation to extract energy, this puzzled researchers due to the extreme metabolic requirements of E. viviparus due to their size, high levels of reproduction, and swimming ability. "fermenting organisms just don't get as much bang for the buck from nutrients," said Angert.
The researchers discovered that E. viviparus devotes a large portion of its genetic code to making enzymes to harvest available nutrients, a rather rare method of energy production. Of the enzymes produced, ATP was one of the most widely produced by the bacteria. The team also discovered a highly folded membrane that runs along the outermost edge of the bacteria to provide space for energy-producing and transporting proteins, similar to how mitochondria function in the cells of other organisms.
"We all know that phrase 'the mitochondria are the powerhouse of the cell," said Angert, "and amazingly, these membranes in E. viviparus have kind of converged on the same model as the mitochondria: They have a highly folded membrane that increases surface area where these energy-producing pumps can work, and that increased surface area creates a powerhouse of energy."
The findings have several potential applications, particularly as the bacteria are highly effective at making use of the nutrients found in algae. With a growing focus on algae as a potential source of livestock feed, renewable energy, and human nutrition, the research conducted on E. viviparus could have long-lasting impacts on numerous industries.