{"id":115047,"date":"2016-08-02T09:14:53","date_gmt":"2016-08-02T13:14:53","guid":{"rendered":"https:\/\/today.uconn.edu\/?p=115047"},"modified":"2016-08-02T10:13:26","modified_gmt":"2016-08-02T14:13:26","slug":"tiniest-parasites","status":"publish","type":"post","link":"https:\/\/today.uconn.edu\/2016\/08\/tiniest-parasites\/","title":{"rendered":"The Tiniest Parasites"},"content":{"rendered":"

Bacteria are the smallest organisms that scientists agree are\u00a0alive. But there are even smaller things that parasitize bacteria. UConn microbiologists have been studying a single gene that is a parasite of bacteria, and in the July 26 issue of the\u00a0Proceedings of the National Academy of Sciences<\/a>,<\/em> they report that while it can hamper individual bacteria, it may\u00a0help a\u00a0bacterial population as a whole.<\/p>\n

Inteins are parasitic genes that actively invade single-celled organisms, including bacteria, archaea, and yeasts. Once an intein is inside a cell, it deploys a special chemical ‘sword’ that homes in on the cell\u2019s DNA, finds exactly the right spot, and slices it open. Then the intein slips inside and cellular DNA repair machinery stitches the DNA back together as if it was supposed to be there in the first place. The intein doesn\u2019t perform any useful function, at least initially. It just lurks there, getting replicated by the cell\u2019s DNA machinery and passed on when the organism reproduces.<\/p>\n

UConn microbiologists Peter Gogarten and Shannon Soucy, a recent Ph.D. in molecular and cell biology, were curious to find out whether inteins took a toll on the host cells they hijack, or whether they provide any benefit.<\/p>\n

\u201cYou can have a selfish gene, or a domesticated gene. But what happens in between? How does that transition from selfish to domesticated happen?\u201d asks Soucy.<\/p>\n

Soucy and Gogarten, along with former UConn undergraduate Anna Green ’13 (CLAS) and colleagues at Tel Aviv University in Israel, decided to look at a specific intein that commonly infects salt-tolerant archaea. The intein is common in salt-tolerant archaea, but not ubiquitous \u2013 only 10 percent of salt-tolerant archaea carry it. Which is odd, because one of this intein\u2019s parasitical tricks is super-Mendelian inheritance. It manages to sneak itself into the DNA of its archaea hosts\u2019 offspring about 80 percent of the time. A normal gene\u2019s inheritance rate is 50 percent.<\/p>\n

The researchers wondered, if the intein is really so successful at getting inherited, why isn\u2019t it everywhere? Perhaps it is a selfish gene that costs the host, making it less likely to reproduce. But if the intein makes its host less likely to reproduce, why is it still so common?<\/p>\n

To figure out why, the researchers decided to break the problem into pieces. First they tried to find out whether the intein actually incurs a cost on the archaea it infects, making them less likely to reproduce.<\/p>\n

They created two almost identical strains of Haloferax volcanii<\/i>, a salt-tolerant archaeon native to warm, salty waters such as the Israeli Mediterranean coast and the Dead Sea. One was infected with the intein, the other was not. And they found that in the laboratory, with plenty of room and resources, the uninfected H. Volcanii<\/i> without the intein had the advantage and grew about 7 percent faster. Models the researchers made showed that in environments with more limited resources where the archaea couldn\u2019t grow actively, they would still continue to trade genes (archaea, like bacteria, play genetic \u2018telephone,\u2019 passing packets of genes around) and after several generations all the archaea would be infected.<\/p>\n

The researchers also noticed something else. In these mixed populations, where some archaea were infected with the intein and some were not, the archaea engaged in sexual recombination \u2013 in which two archaea fuse, mix up\u00a0their chromosomes, and then split into two organisms again \u2013 more often than they did in intein-free groups. This is obviously good for the intein, as more sexual recombination increases its opportunities to spread. But it\u2019s also good for the archaea, as more recombination\u00a0leads to faster evolution and a more diverse population that can potentially handle more diverse, and more stressful, environments.<\/p>\n

But it still doesn\u2019t explain exactly why, if the intein is so good at getting inherited, and it encourages sexual reproduction, why doesn\u2019t every single salt-tolerant archaeon end up infected within a few generations?<\/p>\n

It\u2019s a complicated dynamic, even in the limited ecosystem of a single species\u2019 genome. Gogarten is philosophical about the process.<\/p>\n

\u201cThings happen in nature that are not really beneficial for the organism. Humans are full of remnants of genetic invaders we still carry around. Sometimes they pick up a function like the introns [pieces of DNA] that disrupt our genes and have to be removed when the gene is expressed into a protein. Some of these introns have become important in regulation and allow for alternative splicing, increasing the number of different proteins our genome encodes,\u201d he says.<\/p>\n

By investigating this smallest of parasites in our smallest of cousins, we might better understand how a few of our ancient enemies, encoded into our genes, became our friends.<\/p>\n","protected":false},"excerpt":{"rendered":"

A UConn study of bacterial parasites may shed light on how the human genome grew.<\/p>\n","protected":false},"author":79,"featured_media":115092,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_crdt_document":"","wds_primary_category":0,"wds_primary_series":0,"wds_primary_attribution":0,"footnotes":""},"categories":[2226,2459,2076,1875,2225,2458],"tags":[],"magazine-issues":[],"coauthors":[1899],"class_list":["post-115047","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-clas","category-graduate-students","category-research","category-grad-school","category-uconn-storrs","category-undergraduates"],"pp_statuses_selecting_workflow":false,"pp_workflow_action":"current","pp_status_selection":"publish","acf":[],"publishpress_future_action":{"enabled":false,"date":"2026-05-09 04:41:37","action":"change-status","newStatus":"draft","terms":[],"taxonomy":"category","extraData":[]},"publishpress_future_workflow_manual_trigger":{"enabledWorkflows":[]},"_links":{"self":[{"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/posts\/115047","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/users\/79"}],"replies":[{"embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/comments?post=115047"}],"version-history":[{"count":11,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/posts\/115047\/revisions"}],"predecessor-version":[{"id":115147,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/posts\/115047\/revisions\/115147"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/media\/115092"}],"wp:attachment":[{"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/media?parent=115047"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/categories?post=115047"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/tags?post=115047"},{"taxonomy":"magazine-issue","embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/magazine-issues?post=115047"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/today.uconn.edu\/wp-rest\/wp\/v2\/coauthors?post=115047"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}