title: Conditioned medium from Listeria innocua stimulates emergence from a resting state: not a response to E. coli quorum sensing autoinducer AI-2.
abstract: The lag phase of the bacterial growth curve is an important determinant in speeding the detection of pathogens. It is affected by many factors including the prevailing growth environment and inoculum size, as well as specific signal molecules. The elucidation of growth-regulating signal molecules is further facilitated by culturing cells in defined growth media. In this study, a defined medium capable of supporting growth of Listeria innocua at similar levels as obtained using a complex brain heart infusion (BHI) media was developed. Further, the effects of conditioned medium (CM) on population lag time of L. innocua was investigated using a rapid parallel approach (with an automated microtiter plate reader). Importantly, the lag phase was shortened by up to approximately 50% by the addition of CM from L. innocua cultures obtained late in the exponential phase. Finally, while L. innocua were found to secrete bacterial signaling autoinducer, AI-2, tests using Escherichia coli based CM having a 90-fold difference in AI-2 level suggested that the observed decrease in lag phase was not due to E. coli-derived AI-2 and was instead due to elements specific to L. innocua. These findings indicate secreted signal molecules may be found in CM that speed detection of L. innocua.
authors.affiliation: Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Sciences Building, College Park, 20742, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.forename: Frank
authors.initials: F
authors.lastname: Portugal
authors.forename: William E
authors.initials: WE
authors.lastname: Bentley
mesh_terms: D002455:Cell Division / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000378:metabolism / Q000494:pharmacology*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism / Q000494:pharmacology*; D008087:Listeria / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D017077:Culture Media, Conditioned; D029968:Escherichia coli Proteins