{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T09:34:46Z","timestamp":1791279286296,"version":"4.1.0"},"reference-count":31,"publisher":"Springer Science and Business Media LLC","issue":"1","content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["BMC Microbiol"],"published-print":{"date-parts":[[2013,12]]},"abstract":"<jats:title>Abstract<\/jats:title>\n          <jats:sec>\n            <jats:title>Background<\/jats:title>\n            <jats:p>The <jats:italic>Salmonella enterica<\/jats:italic> serovar Typhimurium PhoPQ two component system (TCS) is activated by low Mg<jats:sup>2+<\/jats:sup> levels, low pH and by antimicrobial peptides (AP). Under Mg<jats:sup>2+<\/jats:sup> limitation, the PhoPQ system induces <jats:italic>pmrD<\/jats:italic> expression, which post-translationally activates the PmrAB TCS. PhoPQ and PmrAB control many genes required for intracellular survival and pathogenesis. These include the polymyxin resistance (<jats:italic>pmr)<\/jats:italic> operon, which is required for aminoarabinose modification of LPS and protecting the outer membrane from antimicrobial peptide disruption and killing. Extracellular DNA is a ubiquitous polymer in the matrix of biofilms and accumulates in some infection sites. Extracellular DNA chelates cations and thus activates the <jats:italic>Pseudomonas aeruginosa<\/jats:italic> PhoPQ\/PmrAB systems, leading to expression of the orthologous <jats:italic>arn<\/jats:italic> (<jats:italic>pmr<\/jats:italic>) operon.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results<\/jats:title>\n            <jats:p>Here we show that extracellular DNA induces expression of the <jats:italic>S<\/jats:italic>. Typhimurium <jats:italic>pmr<\/jats:italic> antimicrobial peptide resistance operon in a PhoPQ and PmrAB-dependent manner. Induction of the <jats:italic>pmr<\/jats:italic> genes by DNA was blocked when present with excess Mg<jats:sup>2+<\/jats:sup>. Exogenous DNA led to increased resistance of planktonic cultures to aminoglycosides, antimicrobial peptides (AP) and ciprofloxacin, but only AP resistance was PhoPQ\/PmrAB-dependent. Extracellular DNA was shown to be a matrix component of <jats:italic>S<\/jats:italic>. Typhimurium biofilms cultivated in flow chambers and on glass surfaces. A <jats:italic>pmrH-gfp<\/jats:italic> fusion was highly expressed in flow chamber biofilms cultivated in medium with repressing levels of 10\u00a0mM\u00a0Mg<jats:sup>2+<\/jats:sup> and co-localized with eDNA. Expression of <jats:italic>pmrH-lux<\/jats:italic> was monitored in plastic peg biofilms and shown to require PhoPQ and PmrAB. Biofilms had higher levels of <jats:italic>pmrH<\/jats:italic> expression compared to planktonic cultures. We propose that DNA accumulation in biofilms contributes to the increased <jats:italic>pmrH-lux<\/jats:italic> expression in biofilms.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusions<\/jats:title>\n            <jats:p>The <jats:italic>Salmonella<\/jats:italic> PhoPQ\/PmrAB systems and antimicrobial peptide resistance are activated by the cation chelating properties of extracellular DNA. DNA-induced AP resistance may allow immune evasion and increased survival of <jats:italic>S.<\/jats:italic> Typhimurium biofilms formed during extracellular growth stages of an infection or outside the host.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1186\/1471-2180-13-115","type":"journal-article","created":{"date-parts":[[2013,5,25]],"date-time":"2013-05-25T00:14:29Z","timestamp":1369440869000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":80,"title":["Extracellular DNA-induced antimicrobial peptide resistance in Salmonella enterica serovar Typhimurium"],"prefix":"10.1186","volume":"13","author":[{"given":"Lori","family":"Johnson","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shawn R","family":"Horsman","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laetitia","family":"Charron-Mazenod","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amy L","family":"Turnbull","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Heidi","family":"Mulcahy","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael G","family":"Surette","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shawn","family":"Lewenza","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2013,5,24]]},"reference":[{"issue":"11","key":"1983_CR1","doi-asserted-by":"publisher","first-page":"1579","DOI":"10.1111\/j.1462-5822.2009.01368.x","volume":"11","author":"JA Ibarra","year":"2009","unstructured":"Ibarra JA, Steele-Mortimer O: Salmonella\u2013the ultimate insider. 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