Difference between revisions of "Team:CIEI-BJ/Background"

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<li><a href="#a1">Background</a>
 
<li><a href="#a1">Background</a>
 
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<li><a href="#a2">Inspiration</a>
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<li><a href="#a2">What Is Aflatoxin</a>
 
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<li><a href="#a3">Objective</a>
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<li><a href="#a3">Aflatoxin Contamination</a>
 
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<li><a href="#a4">Parallel detection and degradation in yeast</a>
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<li><a href="#a4">Aflatoxin and Our Health</a>
 
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<li><a href="#a5">Detection system</a>
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<li><a href="#a5">Aflatoxin impact on a global scale</a>
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<div class="first-level" id="a1"  >Background</div>
 
<div class="first-level" id="a1"  >Background</div>
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<div class="second-level" id="a2" >Inspiration</div>
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<div class="second-level" id="a2" >What Is Aflatoxin</div>
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<p class="my-content" >Our project is inspired by the possible contamination of the carcinogenic aflatoxin (AFT) in Pu’er, a Chinese traditional fermented tea.</p>
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<p class="my-content" >Aflatoxin is toxic secondary metabolites produced by Aspergillus fungi and Aspergillus parasiticus. AFB1 is the most potent and potentially lethal metabolite and is a known human carcinogen. Aflatoxin are abundant in warm and humid regions, consequently contaminating crops at harvest and during storage. Once the crops were contaminated, the aflatoxin cannot be removed through normal process of cooking.</p>
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<div class="second-level" id="a3" >Objective</div>
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<p class="my-content" >Our project aims to find a system for detection and degradation of AFT-B1, the most potent and potentially lethal human type of AFT.</p>
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<img class="my-img" src="https://static.igem.org/mediawiki/2018/c/cd/T--CIEI-BJ--Project--Background--fig1.png" style="height: 200px"/>
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<div class="second-level" id="a4" >Parallel detection and degradation in yeast</div>
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<img class="my-img" src="https://static.igem.org/mediawiki/2018/2/24/T--CIEI-BJ--Project--Background--fig2.png" style="height: 200px"/>
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<p class="my-content" >Concerning the safety issue to use our product on food product, we used Saccharomyces cerevisiae, the baker’s yeast as the vector</p>
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<p class="my-content" >We used the yeast two-hybrid system based on a pair of single chain antibody variable fragments (ScFv1 and ScFv2) against aflatoxin. Once aflatoxin exists, it mediates the interactions of the two antibody fragments, and then bring the transcription activation domain and the DNA binding domain, fused to ScFv1 and ScFv2, respectively, together, to facilitate the expression of downstream genes, include those for yellow fluorescent protein and candidate AFT-B1-degrading enzymes.</p>
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<div class="second-level" id="a3" >Aflatoxin Contamination</div>
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<p class="my-content" >This parallel detection and degradation also provide an efficient screening system for identifying AFTB1-degrading enzymes.</p>
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<p class="my-content" >Aflatoxin are abundant especially in warm and humid regions. They can contaminate crops at harvest and during storage. Once the crops are contaminated, the aflatoxin in those crops can not be removed by cooking or degraded by our body.</p>
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<div class="second-level" id="a5" >Detection system</div>
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<p class="my-content" >Our everyday commodities such as corn, peanut, pistachio, coconut, soybean, rice etc. are all prone to aflatoxin contamination. Aflatoxin in those products will then be ingested by us, after directly eating the products. Since animal body cannot degrade aflatoxin, the aflatoxin in animals will be transferred to us if we consume any product from those animals.</p>
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<p class="my-content" >The detection module utilizes enhanced yellow fluorescent protein to indicate the presence of aflatoxin, the induction of enzyme proteins and the degradation process.</p>
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<img class="my-img" src="https://static.igem.org/mediawiki/2018/6/6f/T--CIEI-BJ--Project--Background--fig4.png" />
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<div class="second-level" id="a6" >Degradation system</div>
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<div class="second-level" id="a4" >Aflatoxin and Our Health</div>
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<p class="my-content" >We incorporated genes for four enzymes previously identified as AFT-B1-degrading enzymes in our system and  tested whether they can actively degrade aflatoxin.</p>
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<p class="my-content" >Furthermore, ingesting small amount of aflatoxin not enough to cause aflatoxicosis would also bring life threatening risks for a long period of time. The consequence of chronic aflatoxin exposure will lead to a deadly disease, hepatocellular carcinoma (liver cancer). Pregnant woman who suffer from chronic aflatoxin exposure might pass on the toxic aflatoxin to their babies. These new born babies will suffer from stunted growth and immune suppression.</p>
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<div class="third-level" >bacC</div>
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<p class="my-content" >bacC is a bacilysin biosynthesis oxidoreductase gene from Bacillus subtilis subsp. subtilis str. 168. As a new report stated, bacC may contribute to aflatoxin degradation in some degree. The BLAST results showed that bacC has some similarities and identities to reductase with nine reductase enzymes of Mycobacteria smegmatis, which have been proven to clean aflatoxin. Some other experiments were also completed by the author to support this result. As a good candidate to us, we designed experiments to express bacC and tested its functions. Finally, it may be in use as part of our Degradation Subsystem.</p>
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<div class="third-level" >ADTZ</div>
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<img class="my-img" src="https://static.igem.org/mediawiki/2018/e/e0/T--CIEI-BJ--Project--Background--fig5.png" />
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<p class="my-content" >ADTZ, which is also called aflatoxin oxidase (AFO), is the first enzyme identified to bed able to degrade AFB1. It can be isolated from intracellular extracts and show a strong affinity with AFB1. As a potential degradation enzyme candidate in our project, we  induced it by our Detection Subsystem and regulated its expression.</p>
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<p class="my-content" >A causative role in 4.6–28.2% of all global HCC cases</p>
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<div class="third-level" >MNP</div>
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</div>
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<p class="my-content" >Manganese peroxidase (MnP) was produced from white rot edible mushroom Pleurotus ostreatus on the culture filtrate. According to the report, approximately 70% of AFTB1 were removed after treatment of  MnP from Phanerochaete sordida Yk-624 for  24h and reach to complete detoxification by multi-treatment with MnP.</p>
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<div class="third-level" >MSMEG_5998</div>
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<p class="my-content" >Toxicity of aflatoxin mainly targets our liver, causing substantial damage to the liver. Ingesting large amount of aflatoxin will lead to aflatoxin poisoning called aflatoxicosis, and the case fatality rate of aflatoxicosis is 25%. Related symptoms could be: vomiting, abdominal pain, pulmonary edema, convulsions and coma. Severe aflatoxicosis might lead to death with cerebral edema and fatty involvement of the liver, kidneys and heart. It was estimated that approximately 10 to 20 mg of aflatoxin will kill an adult.</p>
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<p class="my-content" >Thioredoxing-MSMEG_5998 is a specially designed aflatoxin degrading enzyme. As reported, MSMEG5998 can alleviate aflatoxin-induced p53 activation in HepG2. It was also proven that this enzyme was safe and non-toxic to cells.</p>
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<div class="second-level" id="a5" >Aflatoxin impact on a global scale</div>
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<p class="my-content" >Aflatoxin are slowly affecting people from all around the world, especially developing and underdeveloped countries which haven’t enforce regulations on aflatoxin in crops due to financial reasons.</p>
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<p class="my-content" >In 2004, the aflatoxicosis outbreak in Kenya was one of the most severe episodes of human aflatoxin poisoning in history. Total cases reported was 317 and the fatality rate was 39%.</p>
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<img class="my-img" src="https://static.igem.org/mediawiki/2018/c/c0/T--CIEI-BJ--Project--Background--fig6.png" />
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<p class="my-content" >However, chronic exposure to aflatoxin might bring risks to people on a larger scale. Over 55 billion people worldwide are at risk of uncontrolled exposure to aflatoxin.</p>
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<img class="my-img" src="https://static.igem.org/mediawiki/2018/c/cf/T--CIEI-BJ--Project--Background--fig7.png" />
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<p class="my-content" >Of the 550,000–600,000 new HCC cases worldwide each year, about 25,200–155,000 may be attributable to aflatoxin exposure.</p>
 
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Revision as of 07:34, 12 October 2018

Top
Background
What Is Aflatoxin

Aflatoxin is toxic secondary metabolites produced by Aspergillus fungi and Aspergillus parasiticus. AFB1 is the most potent and potentially lethal metabolite and is a known human carcinogen. Aflatoxin are abundant in warm and humid regions, consequently contaminating crops at harvest and during storage. Once the crops were contaminated, the aflatoxin cannot be removed through normal process of cooking.

Aflatoxin Contamination

Aflatoxin are abundant especially in warm and humid regions. They can contaminate crops at harvest and during storage. Once the crops are contaminated, the aflatoxin in those crops can not be removed by cooking or degraded by our body.

Our everyday commodities such as corn, peanut, pistachio, coconut, soybean, rice etc. are all prone to aflatoxin contamination. Aflatoxin in those products will then be ingested by us, after directly eating the products. Since animal body cannot degrade aflatoxin, the aflatoxin in animals will be transferred to us if we consume any product from those animals.

Aflatoxin and Our Health

Furthermore, ingesting small amount of aflatoxin not enough to cause aflatoxicosis would also bring life threatening risks for a long period of time. The consequence of chronic aflatoxin exposure will lead to a deadly disease, hepatocellular carcinoma (liver cancer). Pregnant woman who suffer from chronic aflatoxin exposure might pass on the toxic aflatoxin to their babies. These new born babies will suffer from stunted growth and immune suppression.

A causative role in 4.6–28.2% of all global HCC cases

Toxicity of aflatoxin mainly targets our liver, causing substantial damage to the liver. Ingesting large amount of aflatoxin will lead to aflatoxin poisoning called aflatoxicosis, and the case fatality rate of aflatoxicosis is 25%. Related symptoms could be: vomiting, abdominal pain, pulmonary edema, convulsions and coma. Severe aflatoxicosis might lead to death with cerebral edema and fatty involvement of the liver, kidneys and heart. It was estimated that approximately 10 to 20 mg of aflatoxin will kill an adult.

Aflatoxin impact on a global scale

Aflatoxin are slowly affecting people from all around the world, especially developing and underdeveloped countries which haven’t enforce regulations on aflatoxin in crops due to financial reasons.

In 2004, the aflatoxicosis outbreak in Kenya was one of the most severe episodes of human aflatoxin poisoning in history. Total cases reported was 317 and the fatality rate was 39%.

However, chronic exposure to aflatoxin might bring risks to people on a larger scale. Over 55 billion people worldwide are at risk of uncontrolled exposure to aflatoxin.

Of the 550,000–600,000 new HCC cases worldwide each year, about 25,200–155,000 may be attributable to aflatoxin exposure.