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Intelligent Design, the best explanation of Origins » Photosynthesis, Protozoans,Plants and Bacterias » Anammox bacterias

Anammox bacterias

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1 Anammox bacterias on Fri Mar 14, 2014 11:32 am



Mike S. M. Jetten1,2, Laura van Niftrik1, Marc Strous1, Boran Kartal1, Jan T. Keltjens1, and
Huub J. M. Op den Camp1
1Department of Microbiology, IWWR, Faculty of Science, Radboud University of Nijmegen, Toernooiveld 1, NL-6525
ED Nijmegen, The Netherlands, and 2Department of Biotechnology, Delft University of Technology, Julianalaan 67,
NL-2628 BC Delft, The Netherlands

Abstract (Enitre article is available to read)

Anaerobic ammonium-oxidizing (anammox) bacteria are one of the latest additions to the biogeochemical
nitrogen cycle. These bacteria derive their energy for growth from the conversion of ammonium and nitrite
into dinitrogen gas in the complete absence of oxygen. These slowly growing microorganisms belong to
the order Brocadiales and are affiliated to the Planctomycetes. Anammox bacteria are characterized by a
compartmentalized cell architecture featuring a central cell compartment, the “anammoxosome”. Thus far
unique “ladderane” lipid molecules have been identified as part of their membrane systems surrounding
the different cellular compartments. Nitrogen formation seems to involve the intermediary formation of
hydrazine, a very reactive and toxic compound. The genome of the anammox bacterium Kuenenia stuttgartiensis
was assembled from a complex microbial community grown in a sequencing batch reactor (74%
enriched in this bacterium) using a metagenomics approach. The assembled genome allowed the in silico
reconstruction of the anammox metabolism and identification of genes most likely involved in the process.
The present anammox pathway is the only one consistent with the available experimental data, thermodynamically
and biochemically feasible, and consistent with Ockham’s razor: it invokes minimum biochemical
novelty and requires the fewest number of biochemical reactions.
The worldwide presence of anammox
bacteria has now been established in many oxygen-limited marine and freshwater systems, including
oceans, seas, estuaries, marshes, rivers and large lakes. In the marine environment over 50% of the N2 gas
released may be produced by anammox bacteria. Application of the anammox process offers an attractive
alternative to current wastewater treatment systems for the removal of ammonia-nitrogen. Currently, at
least five full scale reactor systems are operational.

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2 Re: Anammox bacterias on Fri Mar 14, 2014 11:33 am


Newly discovered bacterial partnership changes ocean chemistry

In a discovery that further demonstrates just how unexpected and unusual nature can be, scientists have found two strains of bacteria whose symbiotic relationship is unlike anything seen before.

Long, thin, hairlike Thioploca (meaning “sulfur braids” in Spanish) trichomes form chains down into marine sediment, which tiny anammox cells ride down like an elevator. At the bottom, the anammox cells consume nitrite and ammonium, or “fixed” nitrogen, the waste products of the Thioploca.

Nitrogen is a crucial building block of life, a prerequisite for photosynthesis. While nitrogen is present in abundance in the Earth’s atmosphere, to be useful for most living organisms, the nonreactive atmospheric nitrogen that diffuses into the ocean from the air must be converted into the biologically available “fixed” forms ammonium, nitrate and nitrite by specialized organisms called nitrogen fixers. Other organisms use up this fixed nitrogen and convert it back to di-nitrogen gas.

Living together in the mud beneath areas of high plant productivity, Thioploca and anammox intensify this part of the nitrogen cycle.

Gliding down through the mud, Thioploca chains bring down nitrate — a highly desirable resource in the harsh environment of oxygen-free sediments. As Thioploca encounters sulfide (which is a roadblock for most other bacteria) formed from the reaction of organic matter from above and sea water sulfate, it helps react nitrate with sulfide, producing nitrite and ammonium, which the anammox consumes and churns out di-nitrogen gas.

The anammox cells ride on Thioploca, living off its waste, and so both microbes thrive where others perish. Overall, however, they lock up an important resource for life in the ocean, making it unusable by the organisms at the base of the food chain that rely on photosynthesis to survive.

“The symbiotic relationship we discovered is an incredibly elegant chemical tandem between two chemolithotrophs — organisms which derive their metabolic energy purely from inorganic chemistry. We first predicted the symbiosis based on realization that Thioploca’s waste [nitrite and ammonium] are ‘bread and butter’ for anammox,” said Maria Prokopenko, lead author of a paper on the research that appeared in Nature earlier this month. “The prediction was confirmed by our team, proving that the symbiotic pair builds a very efficient natural ‘waste-treatment plant’ — destroying substantial quantities of fixed nitrogen while linking sulfur and nitrogen cycles in oxygen-free sediments.”

Prokopenko is currently a visiting scholar at Pomona College, but completed the research while she was a research assistant professor at USC, working with William Berelson, chair of the Earth Sciences Department at the USC Dornsife College of Letters, Arts and Sciences.

Prokopenko and Berelson collaborated with researchers from the University of California, Davis; the University of Southern Denmark; Pomona College; the University of Connecticut; Princeton University and the University of Cincinnati.

The symbiosis between Thioploca and anammox is not one creating widespread change throughout the ocean, but rather one that creates localized zones where fixed nitrogen is depleted faster than most expected.

Most of the samples collected were found off the coast of Baja California.

“As important as nitrogen is to life on this planet, it is amazing that we can discover new pathways and chemical reactions and biological partnerships involving this compound,” Berelson said.

Prokopenko, Berelson and others are presently studying nitrogen cycling in waters off Chile and Peru and are also investigating the history of nitrate preserved in ancient rocks.

The research was funded by the National Science Foundation (grant number OCE-0727123).

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