Microbes have developed a quick and effective way to exchangegenetic information coding for antibiotic resistance, other functions. Just as the digital age allows people to exchange informationinstantly, bacteria linked to humans and their livestock also seemsto freely and rapidly exchange genetic material related to humandisease and antibiotic resistance through a mechanism calledhorizontal gene transfer (HGT). Research leader Eric Alm of MIT’s Department of Civil andEnvironmental Engineering and Department of Biological Engineeringsays in a paper published in Nature online that he and his teamhave found evidence of an enormous network of recent gene exchangethat connects bacteria from around the world: 10,000 unique genesflowing via HGT among 2,235 bacterial genomes. Scientists have long known about HGT, an ancient method forbacteria from different lineages to acquire and share usefulgenetic information that they did not inherit from their parents.They know, that when a transferred gene is bestowed with adesirable trait, for example antibiotic resistance orpathogenicity, it may undergo positive selection and be passed onto a bacterium’s own descendant. This can be detrimental to humans,as seen in the proliferation of antibiotic-resistant bacteriastrains in so-called “super bugs.” Until now, scientists did no know how much or how rapidly thisinformation was being exchanged, however, MIT researchers havemanaged to illustrate the vast scale and rapid speed with whichgenes can proliferate across bacterial lineages.
Alm, the Karl Van Tassel Associate Professor explains: “We are finding [completely] identical genes in bacteria that areas divergent from each other as a human is to a yeast. This showsthat the transfer is recent; the gene hasn’t had time to mutate.” Computational systems biology graduate student Chris Smillie, oneof the lead authors of the paper says: “We were surprised to find that 60% of transfers amonghuman-associated bacteria include a gene for antibioticresistance.” These resistance genes might be associated with using antibioticsin industrial agriculture because researchers discovered 42antibiotic-resistance genes that were shared between livestock- andhuman-associated bacteria. This demonstrates a crucial link thatconnects pools of drug resistance in human and agriculturalpopulations. Alm comments: “Somehow, even though a billion years of genome evolution separatea bacterium living on a cow and a bacterium living on a human, bothare accessing the same gene library.
It’s powerful circumstantialevidence that genes are being transferred between food animals andhumans.” The researchers furthermore identified 43 independent cases ofantibiotic-resistance genes crossing between nations. Mark Smith,microbiology graduate student and also a lead author of the studywarns: “This is a real international problem. Once a trait enters thehuman-associated gene pool, it spreads quickly without regard fornational borders.” The U.S. has a widespread practice of adding prophylacticantibiotics to animal feed to promote growth and prevent the spreadof disease in densely housed herds and flocks. This is banned inmany European countries. Clean Room Sticky Mat
The Federal Drug Administration statesthat over 80% of the 33 million pounds of antibiotics, includingpenicillins and tetracyclines commonly used as human medicines,were sold in the U.S. in 2009 for agricultural use, with 90% beingadministered sub therapeutically through food and water. The researchers discovered that HGT occurs more frequently amongstbacteria occupying the same body site, share the same oxygentolerance or have the same pathogenicity. This leads to theconclusion that ecology, or environmental places, are moreimportant to whether a transferred gene will be incorporated into abacterium’s DNA and passed on to its descendants than eitherlineage or geographical proximity in determining. Kapton Polyimide Tape Manufacturer
Alm explains: “This gives us a rulebook for understanding the forces that governgene exchange.” By applying these rules in order to discover genes that are linkedto the ability to cause meningitis and other diseases, the team hopes that transferred traits and thegenes encoding those traits might pave the way for especiallypromising targets for future drug therapies. They are continuing their work and are currently comparing exchangerates amongst bacteria living in separate sites on the same personand amongst bacteria living on or in people who suffer from thesame disease. They are also studying an environmentallycontaminated site to establish which swapped genes might facilitatemicrobial cleanup by metal-reducing bacteria. Co-authors of the Nature paper are graduate student JonathanFriedman, postdoc Otto Cordero and former graduate student LawrenceDavid, now at Harvard University. The research is part of the National Institutes of Health’s HumanMicrobiome Project and was funded by the Department of Energy’sENIGMA Scientific Focus Area and the National Science Foundation. Anti Static Safety Shoes
Written by: Petra Rattue Copyright: Medical News Today Not to be reproduced without permission of Medical News Today Additional References Citations.