Team:Brown-Stanford/PowerCell/Cyanobacteria

From 2011.igem.org

(Difference between revisions)
(Created page with "{{:Team:Brown-Stanford/Templates/Main}} == '''Introduction''' == Mars is a hostile, desolate environment. In order to live there, humans will have to deal with extreme cold, u...")
(→Anabaena 7120)
 
(62 intermediate revisions not shown)
Line 1: Line 1:
{{:Team:Brown-Stanford/Templates/Main}}
{{:Team:Brown-Stanford/Templates/Main}}
 +
<html>
 +
<div id="subHeader">
 +
<ul id="subHeaderList">
 +
<li><a href="/Team:Brown-Stanford/PowerCell/Introduction">Introduction</a></li>
 +
<li id="active"><a href="#" id="current">Cyanobacteria</a></li>
 +
<li><a href="/Team:Brown-Stanford/PowerCell/Background">Photosynthesis on Mars</a></li>
 +
<li><a href="/Team:Brown-Stanford/PowerCell/NutrientSecretion">Nutrient Secretion and Utilization</a></li>
 +
</ul>
 +
</div>
 +
</html>
 +
{{:Team:Brown-Stanford/Templates/Content}}
 +
== '''Cyanobacteria''' ==
-
== '''Introduction''' ==
+
The search for a suitable chassis on which to build the PowerCell project turned up several promising contenders: algae are very efficient solar powerhouses, and ''E. coli'' has been engineered to express rubisco and perform a rudimentary form of carbon sequestration, among others.  After carefully weighing our options, we hit upon cyanobacteria, commonly (and slightly inaccurately) called blue-green algae. 
 +
<center>[[File:Brown-Stanford cyanobacteria bloom.JPG|300px|none|thumb|Cyanobacteria proliferate in bodies of water and are an important primary producer in the Earth ecosystem]][[File:Brown-Stanford Nitrogen cycle.JPG|300px|none|thumb|Bacteria that fix atmospheric nitrogen are part of the terrestrial nitrogen cycle (photo courtesy the EPA)]]</center>
-
Mars is a hostile, desolate environment.  In order to live there, humans will have to deal with extreme cold, unfiltered solar radiation, low oxygen, and little water{{:Team:Brown-Stanford/Templates/FootnoteNumber|1}}. Cellular engineering will solve these problems in time, but that raises a new problem--the extra burden of providing these requirements raises the already considerable needs of these microbes{{:Team:Brown-Stanford/Templates/FootnoteNumber|2}}. It may be possible to feed them from a stored cache of growth nutrients for some time, but these basic requirements will have to be extracted from local resources if a self-sustaining colony is to exist.
+
==='''Anabaena 7120'''===
 +
To host PowerCell, we chose a [http://en.wikipedia.org/wiki/Diazotroph diazotropic] cyanobacterium, ''Anabaena'' 7120. ''Anabaena'' 7120 has several characteristics that make it a good choice of host - most importantly its ability to fix atmospheric nitrogen into biologically useful forms.  
-
PowerCell is our solution to this problem; by engineering cyanobacteria to excrete sugar compounds photosynthesized from atmospheric carbon dioxide{{:Team:Brown-Stanford/Templates/FootnoteNumber|3}}, PowerCell will provide other bacterial cultures with a rich carbon source, a basic requirement for producing biomass and other compounds. In addition, PowerCell able to fix atmospheric N2 and release it in a form accessible to bacteria, providing a basic requirement for protein synthesis and other crucial biological functions{{:Team:Brown-Stanford/Templates/FootnoteNumber|4}}. 
+
[[File:Brown-Stanford Anabeana.jpg|500px|center|thumb|''Anabaena'' 7120 is a filamentous bacterium capable of both photosynthesis and nitrogen fixation. Light micrograph of one of our Anabaena, 630x bright field]]
-
+
-
By producing two of the macromolecules essential to bacterial growth, PowerCell will form a metabolic foundation for the biological systems which will eventually enable a settlement on Mars.  Other microbes producing oxygen, heat, food, light, and other necessities will follow, and in time, a complete biogenic life support system will be put together, all fueled by PowerCell.
+
-
[[File:Brown-Stanford PowerCellEnergyFlowDiagram.jpg|700px|center]]
+
----
-
===References===
+
=== '''Nitrogen and Oxygen''' ===
-
{{:Team:Brown-Stanford/Templates/Footnote|1|R. Hanel, B. Conrath, W. Hovis, V. Kunde, P. Lowman, W. Maguire, J. Pearl, J. Pirraglia, C. Prabhakara, B. Schlachman, G. Levin, P. Straat, T. Burke, Investigation of the Martian environment by infrared spectroscopy on Mariner 9, Icarus, Volume 17, Issue 2, October 1972, Pages 423-442, ISSN 0019-1035, DOI: 10.1016/0019-1035(72)90009-7. (http://www.sciencedirect.com/science/article/pii/0019103572900097)}}
+
-
{{:Team:Brown-Stanford/Templates/Footnote|2|Weeks, Amy M, and Michelle C Y Chang. 2011. “Constructing de novo biosynthetic pathways for chemical synthesis inside living cells.” Biochemistry 50 (24) (June 21): 5404-5418. doi:10.1021/bi200416g.}}
+
''Anaebaena'' is a diazotroph, or “N<sub>2</sub> eater.” The organism has evolved a nitrogenase which is capable of overcoming the triple covalent bond between the two nitrogen atoms, although the reaction is oxygen-sensitive and can only take place in an anaerobic environment.
-
{{:Team:Brown-Stanford/Templates/Footnote|3|Niederholtmeyer, Henrike, Bernd T Wolfstädter, David F Savage, Pamela A Silver, and Jeffrey C Way. 2010. “Engineering cyanobacteria to synthesize and export hydrophilic products.” Applied and Environmental Microbiology 76 (11) (June): 3462-3466. doi:10.1128/AEM.00202-10.}}
 
-
{{:Team:Brown-Stanford/Templates/Footnote|4|Chaurasia, Akhilesh Kumar, and Shree Kumar Apte. 2011. “Improved eco-friendly recombinant Anabaena sp. strain PCC7120 with enhanced nitrogen biofertilizer potential.” Applied and Environmental Microbiology 77 (2) (January): 395-399. doi:10.1128/AEM.01714-10.}}
+
[[File:Brown-Stanford nitrogenase diagram.png|200px|left|thumb|Nitrogenase {{:Team:Brown-Stanford/Templates/FootnoteNumber|1}}]]
 +
[[File:Brown-Stanford Heterocysts.JPG|300px|right|thumb|Heterocysts on an Anabaena filament (http://www.uniprot.org/taxonomy/103690)]]
 +
For this reason, most diazotrophs separate the processes of photosynthesis and nitrogen fixation temporally – that is, they photosynthesize in the day and fix nitrogen at night. Anabaena 7120 has a different way around this problem. It forms long filaments of cells containing two different cell types, normal (vegetative) cells, and heterocysts.
 +
 +
Heterocysts are specialized cells, visibly larger and darker than the rest, and form thick cell walls which house an anaerobic intracellular microenvironment where the nitrogenase can perform nitrogen fixation.  The nitrogen-containing products are exported to adjacent vegetative cells via plasmodesmata, through which photosynthesized carbon products return. Normal (vegetative) cells carry on with photosynthesis. The two cell types then share nutrients up and down the filament, thus providing each cell with all the nutrients it needs.
 +
 +
 +
''Anabaena'' can live in aerobic conditions, fix nitrogen and photosynthesize sugars.  They are able to produce almost everything they need, making them capable of living on very minimal media—clear water with a few trace minerals.  It follows that we can harness their self-sufficiency to provide for more dependent organisms, such as ''E. coli''.  All we have to do is enforce some compulsory generosity, and although ''Anabaena'' won’t be as well-fed as it was as a selfish microbe, the ''E. coli'' it is supporting will have a food source where it otherwise would have gone hungry.
 +
 +
----
 +
 +
===References===
 +
{{:Team:Brown-Stanford/Templates/Footnote|1|http://chemwiki.ucdavis.edu/Wikitexts/UC_Davis/UCD_Chem_124A:_Berben/Nitrogenase/Nitrogenase_2}}
{{:Team:Brown-Stanford/Templates/Foot}}
{{:Team:Brown-Stanford/Templates/Foot}}

Latest revision as of 01:32, 29 October 2011

Brown-Stanford
iGEM
Back to
iGEM HQ

Cyanobacteria

The search for a suitable chassis on which to build the PowerCell project turned up several promising contenders: algae are very efficient solar powerhouses, and E. coli has been engineered to express rubisco and perform a rudimentary form of carbon sequestration, among others. After carefully weighing our options, we hit upon cyanobacteria, commonly (and slightly inaccurately) called blue-green algae.

Cyanobacteria proliferate in bodies of water and are an important primary producer in the Earth ecosystem
Bacteria that fix atmospheric nitrogen are part of the terrestrial nitrogen cycle (photo courtesy the EPA)

Anabaena 7120

To host PowerCell, we chose a diazotropic cyanobacterium, Anabaena 7120. Anabaena 7120 has several characteristics that make it a good choice of host - most importantly its ability to fix atmospheric nitrogen into biologically useful forms.

Anabaena 7120 is a filamentous bacterium capable of both photosynthesis and nitrogen fixation. Light micrograph of one of our Anabaena, 630x bright field

Nitrogen and Oxygen

Anaebaena is a diazotroph, or “N2 eater.” The organism has evolved a nitrogenase which is capable of overcoming the triple covalent bond between the two nitrogen atoms, although the reaction is oxygen-sensitive and can only take place in an anaerobic environment.


Nitrogenase 1
Heterocysts on an Anabaena filament (http://www.uniprot.org/taxonomy/103690)

For this reason, most diazotrophs separate the processes of photosynthesis and nitrogen fixation temporally – that is, they photosynthesize in the day and fix nitrogen at night. Anabaena 7120 has a different way around this problem. It forms long filaments of cells containing two different cell types, normal (vegetative) cells, and heterocysts.

Heterocysts are specialized cells, visibly larger and darker than the rest, and form thick cell walls which house an anaerobic intracellular microenvironment where the nitrogenase can perform nitrogen fixation. The nitrogen-containing products are exported to adjacent vegetative cells via plasmodesmata, through which photosynthesized carbon products return. Normal (vegetative) cells carry on with photosynthesis. The two cell types then share nutrients up and down the filament, thus providing each cell with all the nutrients it needs.


Anabaena can live in aerobic conditions, fix nitrogen and photosynthesize sugars. They are able to produce almost everything they need, making them capable of living on very minimal media—clear water with a few trace minerals. It follows that we can harness their self-sufficiency to provide for more dependent organisms, such as E. coli. All we have to do is enforce some compulsory generosity, and although Anabaena won’t be as well-fed as it was as a selfish microbe, the E. coli it is supporting will have a food source where it otherwise would have gone hungry.

References

1 http://chemwiki.ucdavis.edu/Wikitexts/UC_Davis/UCD_Chem_124A:_Berben/Nitrogenase/Nitrogenase_2

Retrieved from "http://2011.igem.org/Team:Brown-Stanford/PowerCell/Cyanobacteria"