Not all bacteria are the same. Most bacteria are single-celled and very small, only a few ten thousandths of a centimeter long. But bacteria in the Epulopiscium family are large enough to be seen with the naked eye, and are up to a million times larger than their more famous cousin, E. coli. A groundbreaking study of the giant bacterium Epulopiscium viviparus shows it can produce unique energy that could have applications in future algae utilization.
In a study recently published in the Proceedings of the National Academy of Sciences, researchers at Cornell University and Lawrence Berkeley National Laboratory have described for the first time the complete genome of a species in a family of giant bacteria, naming it Epulopiscium viviparus.
"This incredibly giant bacterium is unique and interesting in many ways: its huge size, the way it reproduces, the way it meets its metabolic needs, and more. Uncovering the genomic potential of this organism was eye-opening," said Esther Angert, professor of microbiology in the College of Agriculture and Life Sciences and corresponding author of the study.
Habitat and Characteristics
The first member of the Epulopiscium family was discovered in 1985. All members of this species live symbiotically in the intestines of certain swordfish found in tropical marine coral reef environments such as the Great Barrier Reef and the Red Sea.
Because of its huge size, scientists initially thought it was some kind of unique protozoa, Angert said. The name Epulopiscium comes from the Latin roots epulo meaning "guest" and piscium meaning "fish". While most bacteria reproduce by splitting themselves in half, producing two offspring, E. viviparus can produce up to 12 copies of itself, which grow inside the mother cell and are then released, "actively swimming -- viviparus means 'live birth,'" Angert said.
For decades, Angert has worked with fish biologists at Australia's Lizard Island Research Station to collect and study samples.
The researchers are particularly interested in understanding how E. viviparus meets its extreme metabolic needs. Bacteria that feed on nutrients in the environment rather than getting their own energy from sunlight generally fall into two camps: those that have access to oxygen and those that don't. "Without oxygen, bacteria typically use fermentation for energy, and fermenting organisms don't get as much benefit from nutrients," Angert said.
The fact that E. viviparus is indeed a fermentant makes the puzzle even bigger, since its huge size, prodigious reproductive capacity, and ability to swim all require more energy, not less.
Genetic adaptation and energy production
The researchers found that E. viviparus changes its metabolism to take advantage of its environment, uses a rare method of making energy and movement (the same swimming method used by the bacteria that cause cholera), and devotes a large portion of its genetic code to making enzymes to obtain nutrients in the host's gut. The most prolific of these enzymes are those used to make ATP, the energy currency of all cells. A highly folded membrane along the outer edge of E. viviparus provides vital space for energy-generating and transport proteins, which bears striking similarities to the function of mitochondria in the cells of more complex organisms.
"We all know the saying 'mitochondria are the powerhouses of the cell,'" Angert said. "What's surprising is that these membranes of E. viviparus tend to follow the pattern of mitochondria: They have highly folded membranes that increase the surface area that these energy-producing pumps can work on, and that increased surface area creates an energy source."
Potential applications and future research
Angert said this basic research has many potential applications in the future, especially because E. viviparus has such an efficient strategy for utilizing nutrients in the algae. Algae is a growing target for livestock feed, renewable energy and human nutrition because its growth does not compete with land-based agriculture.
Compiled source: ScitechDaily