{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T20:04:25Z","timestamp":1785355465428,"version":"3.55.0"},"posted":{"date-parts":[[2026,7,27]]},"group-title":"Microbiology","reference-count":67,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T00:00:00Z","timestamp":1785110400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,7,27]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  One of the best studied quorum sensing (QS) molecules, autoinducer-2 (AI-2), regulates processes in numerous bacteria. LuxS is an enzyme of the activated methyl cycle which, along with MtnN, converts\n                  <jats:italic>S<\/jats:italic>\n                  -adenosyl-homocysteine to homocysteine, releasing DPD (4,5-dihydroxy-2,3-pentanedione) which is spontaneously converted to AI-2. Many bacteria do not encode MtnN-LuxS and instead encode SahH, which directly converts\n                  <jats:italic>S<\/jats:italic>\n                  -adenosyl-homocysteine to homocysteine without AI-2 production. The genomes of some gut Bacteroidales were shown to contain\n                  <jats:italic>luxS<\/jats:italic>\n                  , however, these reports, as well as reports of the production of AI-2 by gut Bactereoidales have been inconsistent. We performed a comprehensive analysis of the distribution of\n                  <jats:italic>luxS<\/jats:italic>\n                  and\n                  <jats:italic>sahH<\/jats:italic>\n                  in Bacteroidota with an in-depth exploration of gut Bacteroidales. The data suggest that the ancestral Bacteroidota contained\n                  <jats:italic>sahH<\/jats:italic>\n                  , with numerous independent replacements with\n                  <jats:italic>mtnN-luxS<\/jats:italic>\n                  during diversification. In Bacteroidaceae,\n                  <jats:italic>Parabacteroides<\/jats:italic>\n                  , and many Prevotellaceae,\n                  <jats:italic>mtnN<\/jats:italic>\n                  -\n                  <jats:italic>luxS<\/jats:italic>\n                  or\n                  <jats:italic>sahH<\/jats:italic>\n                  are present in the same genetic region, adjacent to\n                  <jats:italic>yfhO<\/jats:italic>\n                  . Using\n                  <jats:italic>Bacteroides fragilis<\/jats:italic>\n                  , which contains\n                  <jats:italic>sahH,<\/jats:italic>\n                  and\n                  <jats:italic>Bacteroides uniformis<\/jats:italic>\n                  and\n                  <jats:italic>Phocaeicola vulgatus,<\/jats:italic>\n                  whose genomes contain\n                  <jats:italic>mtnN-luxS<\/jats:italic>\n                  , we show that\n                  <jats:italic>luxS<\/jats:italic>\n                  -containing strains produce AI-2. Transcriptomic analyses and gnotobiotic mouse experiments using wild-type strains and\n                  <jats:italic>mtnN-luxS<\/jats:italic>\n                  and\n                  <jats:italic>sahH<\/jats:italic>\n                  genetic swaps showed that Bacteroidaceae species do not respond to AI-2 under the conditions tested. However, analyses of 15 human gut metagenomic datasets show that\n                  <jats:italic>mtnN-luxS<\/jats:italic>\n                  containing Bacteroidales species average between 5.1 \u2013 33% of the total bacteria in these various human gut microbiome datasets, and therefore, likely produce substantial amounts of AI-2 sensed by responsive gut symbionts and pathogens.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>Importance<\/jats:title>\n                  <jats:p>\n                    Here, we show that gut Bacteroidales possess one of two pathways to complete the activated methyl cycle, one that produces the QS molecule AI-2. We clarify conflicting data regarding AI-2 production in gut Bacteroidales and show that\n                    <jats:italic>luxS<\/jats:italic>\n                    is present in many gut Bacteroidales species, but lacking in species such as\n                    <jats:italic>Bacteroides thetaiotaomicron<\/jats:italic>\n                    and\n                    <jats:italic>Bacteroides fragilis<\/jats:italic>\n                    . We find that prevalent and abundant human gut Bacteroidales species including\n                    <jats:italic>Bacteroides uniformis<\/jats:italic>\n                    and\n                    <jats:italic>Phocaeicola vulgatus<\/jats:italic>\n                    produce substantial amounts of AI-2. While our data do not show that Bacteroidales sense or respond to AI-2 under the conditions tested, analyses of human gut metagenomic data reveal that AI-2 producing Bacteroidales comprise a large proportion of the gut bacteria of both industrialized and non-industrialized human populations.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.07.27.740950","type":"posted-content","created":{"date-parts":[[2026,7,28]],"date-time":"2026-07-28T04:05:12Z","timestamp":1785211512000},"source":"Crossref","is-referenced-by-count":0,"title":["Distribution of\n                  <i>luxS<\/i>\n                  and production of autoinducer-2 among gut Bacteroidales"],"prefix":"10.64898","author":[{"given":"Nolan W.","family":"Kennedy","sequence":"first","affiliation":[{"name":"Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA"},{"name":"Department of Microbiology, University of Chicago, Chicago, Illinois, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rebecca H.","family":"Gellman","sequence":"additional","affiliation":[{"name":"Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA"},{"name":"Department of Microbiology, University of Chicago, Chicago, Illinois, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael J.","family":"Coyne","sequence":"additional","affiliation":[{"name":"Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA"},{"name":"Department of Microbiology, University of Chicago, Chicago, Illinois, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jessica C.","family":"Little","sequence":"additional","affiliation":[{"name":"Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ashley M.","family":"Sidebottom","sequence":"additional","affiliation":[{"name":"Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-6368-8351","authenticated-orcid":false,"given":"Laurie E.","family":"Comstock","sequence":"additional","affiliation":[{"name":"Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA"},{"name":"Department of Microbiology, University of Chicago, Chicago, Illinois, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026072912201589000_2026.07.27.740950v1.1","doi-asserted-by":"publisher","DOI":"10.1126\/science.1237439"},{"key":"2026072912201589000_2026.07.27.740950v1.2","doi-asserted-by":"publisher","DOI":"10.1128\/IAI.01348-10"},{"key":"2026072912201589000_2026.07.27.740950v1.3","doi-asserted-by":"crossref","unstructured":"Coyne MJ , Comstock LE . 2019. 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