CELL'S MITOCHONDRIA WERE ONCE ENERGY PARASITES
Parasitic bacteria
were the first cousins of the mitochondria that power cells in animals and
plants -- and first acted as energy parasites in those cells before becoming
beneficial, according to a new University of Virginia study that used
next-generation DNA sequencing technologies to decode the genomes of 18
bacteria that are close relatives of mitochondria.
The study appears this
week in the online journal PLoS ONE, published by the Public
Library of Science. It provides an alternative theory to two current theories
of how simple bacterial cells were swallowed up by host cells and ultimately
became mitochondria, the "powerhouse" organelles within virtually all
eukaryotic cells -- animal and plant cells that contain a nucleus and other
features. Mitochondria power the cells by providing them with adenosine
triphosphate, or ATP, considered by biologists to be the energy currency of
life.
The origin of
mitochondria began about 2 billion years ago and is one of the seminal events
in the evolutionary history of life. However, little is known about the
circumstances surrounding its origin, and that question is considered an enigma
in modern biology.
"We believe this
study has the potential to change the way we think about the event that led to
mitochondria," said U.Va. biologist Martin Wu, the study's lead author.
"We are saying that the current theories -- all claiming that the relationship
between the bacteria and the host cell at the very beginning of the symbiosis
was mutually beneficial -- are likely wrong.
"Instead, we
believe the relationship likely was antagonistic -- that the bacteria were
parasitic and only later became beneficial to the host cell by switching the
direction of the ATP transport."
The finding, Wu said,
is a new insight into an event in the early history of life on Earth that
ultimately led to the diverse eukaryotic life we see today. Without
mitochondria to provide energy to the rest of a cell, there could not have
evolved such amazing biodiversity, he said.
"We reconstructed
the gene content of mitochondrial ancestors, by sequencing DNAs of its close
relatives, and we predict it to be a parasite that actually stole energy in the
form of ATP from its host -- completely opposite to the current role of
mitochondria," Wu said.
In his study, Wu also
identified many human genes that are derived from mitochondria --
identification of which has the potential to help understand the genetic basis
of human mitochondrial dysfunction that may contribute to several diseases,
including Alzheimer's disease, Parkinson's disease and diabetes, as well as
aging-related diseases.
In addition to the
basic essential role of mitochondria in the functioning of cells, the DNA of
mitochondria is used by scientists for DNA forensics, genealogy and tracing
human evolutionary history.
Comments
Post a Comment