Pictured is a high magnification image of
sediment enriched in syntrophic consortia. In the center of the image is
an overview of sediment containing cells, and individual -- roughly
spherical -- microbial communities are shown at high magnification at
the ends of lines extending from the center. Fluorescent signals show
the ANME-2c archaeal subgroup in red, and sulfate reducing bacteria are
shown in green. Sediment particles appear yellow.
Credit: Grayson Chadwick/Caltech
Good communication is very crucial to any relationship,
especially when partners are separated by distance. This also holds for
microbes in the deep sea that need to work together to consume large amount of
methane released from the vents on the ocean floors.
Recent work has shown that these microbes can still
accomplish their task even if they are not attached together; they use
electrons to share energy over long distances, this was done by Caltech University.
This is the first time that directs interspecies electron
transport—the movement of electrons from a cell, through the external
environment, to another cell type—has been documented in microorganisms in
nature.
The results were published in September 16 issue of the
Journal nature.
“Our lab is interested in microbial communities in the
environment and, specifically, the symbiosis of mutually beneficial
relationship,” says Professor of geobiology Victoria Orphan. For the last
decade, Orphan’s lab has focused on the relationship between the species of
bacteria and a species of archea that lives in symbiotic aggregates with deep
sea methane seeps. The organisms work together in syntrophy—meaning they feed
together—to consume up-to 80 percent of methane emitted from the ocean
floor---methane that could be otherwise contributing to climate change as a
greenhouse gas in our atmosphere.
Because these microbes grow slowly, reproducing twice per
year, and live closest with each other, it has been difficult for researchers
to isolate them for the environment to grow them in the labs. So, the Caltech
team used research submersible, called Alivin, to collect samples containing
the methane-oxidizing microbial consortia from deep-ocean methane seep
sediments and then brought them back to the lab for analysis.
The researchers used different fluorescent DNA stains to
mark two types of microbes and view their spatial orientation in consortia. In
some consortia, Orphan and her colleagues found the bacterial and archaea cells
were mixed, while other consortia, cells of the same type were clustered into
separate areas.
They wondered if the variation in the spatial organization
of the bacteria and archaea within the consortia influenced their cellular
activities and their ability to cooperatively consume methane.
To find out, they applied a stable isotope “tracer” to
evaluate metabolic activities. The
amount of isotope taken by individual archael and bacteria cells within their
microbial neighborhood in each consortium was then measured within
high-resolution instrument called nanoscale secondary mass spectrometry as
Caltech. This helped the researchers to determine how active the archaeal and bacteria partners were relative to their
distance to one another.
To their surprise, the researchers found that the spatial
arrangement of the cells in consortia had no influence on their activity.
To find out how the bacteria and archaea were partnering,
co-first authors Grayson Shadwick looked for patterns in cellular activity for
multiple consortia with different cell arrangement. They found that the
populations of the syntrophic archaea and bacteria in consortia had similar
levels of metabolic activity, the associated partner microorganism were also
equally active.
To determine how these metabolic interactions were taking
place even over relatively long distances, postdoctoral scholar and coauthor
Chris Kempes, modeled the predicted relationship between cellular activity and
distance between syntrophic partners that are dependent on the molecular
diffusion of the substrate. He found
that the conventional metabolites were inconsistent with the spatial activity
patterns observed in the data. However, revised models indicated that electrons
could likely make the trip from cell to cell across greater distances.
Using genome analysis—along with transmission electron
microscopy and a strain that reacts with these multi-heme cytohromes –the
researchers showed that these conductive proteins were also present on the
outer surface of the archaea they were studying. And that finding, Orphan says,
can explain why the spatial arrangement partners do not seem to affect their
relationship or activity.
Orphan said that the information they have learned about
this relationship will help expand how researchers think and interspecies
microbial interactions in nature. In addition, the microscale stable isotope
used in the current study can be used to evaluate interspecies electron
transport and other forms of microbial symbiosis occurring in the environment.
Credit: California Institute of Technology.
Material can be edited for content and length.
No comments:
Post a Comment