biostudies-literatureKlein JANIAID NIH HHSNIGMS NIH HHSe0031424https://www.ebi.ac.uk/biostudies/studies/S-EPMC11477908biostudies-literatureUnknown92(10)<i>Providencia alcalifaciens</i> is a Gram-negative bacterium found in various water and land environments and organisms, including insects and mammals. Some <i>P. alcalifaciens</i> strains encode gene homologs of virulence factors found in pathogenic Enterobacterales members, such as <i>Salmonella enterica</i> serovar Typhimurium and <i>Shigella flexneri</i>. Whether these genes are pathogenic determinants in <i>P. alcalifaciens</i> is not known. In this study, we investigated <i>P. alcalifaciens</i>-host interactions at the cellular level, focusing on the role of two type III secretion systems (T3SS) belonging to the Inv-Mxi/Spa family. T3SS_1b is widespread in <i>Providencia</i> spp. and encoded on the chromosome. A large plasmid that is present in a subset of <i>P. alcalifaciInfection and immunityPathogenic diversification of the gut commensal <i>Providencia alcalifaciens</i> via acquisition of a second type III secretion system.PMC11477908R21 AI130645T32 GM140936R01 AI134766Lele AKlein JAPredeus AVGreen NMCruz EMejia AGoodman AGElfenbein JRClark-Herrera MMGreissl ARWright SJHaeberle ALHowell MKnodler LAWrande MWesterman TLMcClelland MVallance BACundiff JARobinson DJfalsePathogenic diversification of the gut commensal <i>Providencia alcalifaciens</i> via acquisition of a second type III secretion system.<i>Providencia alcalifaciens</i> is a Gram-negative bacterium found in various water and land environments and organisms, including insects and mammals. Some <i>P. alcalifaciens</i> strains encode gene homologs of virulence factors found in pathogenic Enterobacterales members, such as <i>Salmonella enterica</i> serovar Typhimurium and <i>Shigella flexneri</i>. Whether these genes are pathogenic determinants in <i>P. alcalifaciens</i> is not known. In this study, we investigated <i>P. alcalifaciens</i>-host interactions at the cellular level, focusing on the role of two type III secretion systems (T3SS) belonging to the Inv-Mxi/Spa family. T3SS_1b is widespread in <i>Providencia</i> spp. and encoded on the chromosome. A large plasmid that is present in a subset of <i>P. alcalifaci2024-01-01T00:00:00Z2024 Oct2026-07-15T12:57:34.424Z2025-04-04T23:49:56.592ZS-EPMC114779083925434610.1128/iai.00314-24