title: Reporters for Single-Cell Analysis of Colicin Ib Expression in Salmonella enterica Serovar Typhimurium.
abstract: Colicins are toxins that mediate interference competition in microbial ecosystems. They serve as a "common good" for the entire producer population but are synthesized by only few members which pay the costs of colicin production. We have previously shown that production of colicin Ib (cib), a group B colicin, confers a competitive advantage to Salmonella enterica serovar Typhimurium (S. Tm) over commensal E. coli strains. Here, we studied regulation of S. Tm cib expression at the single cell level. Comparative analysis of a single- and a multicopy gfp-reporter for the colicin Ib promoter (Pcib) revealed that the latter yielded optimal signal intensity for a diverse range of applications. We further validated this reporter and showed that gfp expression correlated well with colicin Ib (ColIb) protein levels in individual cells. Pcib is negatively controlled by two repressors, LexA and Fur. Only a small fraction of S. Tm expressed cib under non-inducing conditions. We studied Pcib activity in response to mitomycin C mediated DNA damage and iron limitation. Both conditions, if applied individually, lead to an increase in the fraction of GFP+ S. Tm, albeit an overall low fluorescence intensity. When both conditions were applied simultaneously, the majority of S. Tm turned GFP+ and displayed high fluorescence intensity. Thus, both repressors individually confine cib expression to a subset of the population. Taken together, we provide the first thorough characterization of a conventional gfp-reporter to study regulation of a group B colicin at the single cell level. This reporter will be useful to further investigate the costs and benefits of ColIb production in human pathogenic S. Tm and analyze cib expression under environmental conditions encountered in the mammalian gut.
authors.affiliation: Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Spriewald
authors.affiliation: Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany.|German Centre for Infection Research (DZIF), partner site LMU Munich, Munich Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Glaser
authors.affiliation: Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Beutler
authors.affiliation: Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany.|German Centre for Infection Research (DZIF), partner site LMU Munich, Munich Germany.
authors.forename: Martin B
authors.initials: MB
authors.lastname: Koeppel
authors.affiliation: Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany.|German Centre for Infection Research (DZIF), partner site LMU Munich, Munich Germany.
authors.forename: Bärbel
authors.initials: B
authors.lastname: Stecher
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003087:Colicins / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D059010:Single-Cell Analysis / Q000379:methods*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D003087:Colicins; D049452:Green Fluorescent Proteins; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C068477:ferric uptake regulating proteins, bacterial