--FOR IMMEDIATE RELEASE--
April 4, 2011
Positive Identification
WEST BOOTHBAY HARBOR, ME — A team of scientists from Bigelow Laboratory has determined the true identity of an iron-oxidizing microbe called Leptothrix ochracea, answering a question about its evolutionary development that has eluded researchers since the species was first discovered more than 120 years ago. The paper describing their work is titled “What's New Is Old: Resolving the Identity of Leptothrix ochracea Using Single Cell Genomics, Pyrosequencing and FISH” and has just been published in PLoS ONE, an open access journal (PLoS ONE (2011)6(3): e17769. doi:10.1371/journal.pone.0017769).
Bigelow postdoctoral researcher Dr. Emily Fleming is the paper’s lead author. Co-authors are Dr. Manuel Martinez-Garcia, Dr. Ramunas Stepanauskas, Dr. Nicole J. Poulton, E. Dashiell P. Masland, Dr. David Emerson, and undergraduate intern Amy E. Langdon.
“Connecting the identity of this microbe to a specific genetic marker was only possible because of the unique technology available at Bigelow Laboratory,” said Fleming. “Bigelow’s Single Cell Genomics Center allows us to study the genomes of individual cells taken from environmental samples.”
“The Laboratory encourages researchers to collaborate with one another,” she added. “It was a tremendous help to be able to bring geomicrobiologists together with the microbial genomics researchers and population biologists here to work on this project.”
Leptothrix ochracea is a species of iron-oxidizing bacteria (FeOB) commonly found in freshwater iron seeps and iron-rich wetlands. It makes tubular sheaths encrusted with iron oxyhydroxides (rust) that color the surrounding water various shades of yellow, bright orange, and russet. Compared to other FeOB, L. ochracea is a prolific sheath-producer – a thousand microscopic L. ochracea cells can produce 2 to 3 meters of sheaths in a single day.
Photo-montage of L. ochracea sheaths and cells from Lakeside Drive.
Summer time bloom of typical LD iron mats (A), Scanning electron micrograph of a typical L. ochracea sheath (B). Epi-fluorescence of Syto 13 stained cells (C) and phase contrast image (D) of filamentous cells and sheaths from LD iron mats. Scale bars are 10 cm, 10 µm, 10 µm and 10 µm, respectively (doi:10.1371/journal.pone.0017769.g001). © 2011 Fleming et al.
People who come across L. ochracea populations in nature often mistakenly conclude that they are looking at water polluted by industrial runoff, when, in fact, they are seeing the infrastructure of L. ochracea dwellings. Surprisingly, over 90% of these sheaths are empty, so what appears to be an abundant population of iron-oxidizing bacteria turns out to be relatively few cells industriously manufacturing sheaths as an everyday part of their metabolic lives.
Besides playing an important role in the iron cycle, FeOB mats can decrease water flow and absorb nutrients from the environment. FeOB are considered nuisance organisms when they cause biofouling of water distribution pipelines or contribute to biocorrosion, but are also recognized as having a beneficial role in water filtration systems.
Unlike its relatives, L.ochracea cannot be successfully grown in laboratory cultures. Before the resources of the Single Cell Genomics Center became available, L. ochracea could only be identified by the presence of sheaths. Understanding its biology and behavior had not been possible. Now Bigelow scientists have managed to determine its true position on the FeOB family tree.
“I’m hoping the single amplified genome that’s currently being sequenced will begin to reveal hints about L. ochracea’s nutritional requirements and determine what controls the growth of this microbe,” Fleming said.
The paper’s second author is Amy Langdon, a Swarthmore College student, and a member of the Laboratory’s Research Experience for Undergraduates program, sponsored by the National Science Foundation.
“Langdon’s work was a major part of this project,” Fleming notes. “Her contribution highlights the importance that direct research experience can have for undergraduate students.”
An independent, nonprofit research institution based in midcoast Maine, Bigelow Laboratory for Ocean Sciences is a center for global ocean research. The Laboratory’s research ranges from microbial oceanography -- examining biological productivity in the world’s oceans at the molecular level -- to the large-scale biogeochemical processes that drive interactions between ocean ecosystems and global environmental conditions. These programs have taken Bigelow scientists around the world to every ocean and the polar seas. The Laboratory is a recognized leader in Maine's emerging innovation economy, and is spurring significant economic growth in the state through construction of a major Ocean Science and Education Campus in East Boothbay. ####