title: Phenotypic Heterogeneity Affects Stenotrophomonas maltophilia K279a Colony Morphotypes and β-Lactamase Expression.
abstract: Phenotypic heterogeneity at the cellular level in response to various stresses, e.g., antibiotic treatment has been reported for a number of bacteria. In a clonal population, cell-to-cell variation may result in phenotypic heterogeneity that is a mechanism to survive changing environments including antibiotic therapy. Stenotrophomonas maltophilia has been frequently isolated from cystic fibrosis patients, can cause numerous infections in other organs and tissues, and is difficult to treat due to antibiotic resistances. S. maltophilia K279a produces the L1 and L2 β-lactamases in response to β-lactam treatment. Here we report that the patient isolate S. maltophilia K279a diverges into cellular subpopulations with distinct but reversible morphotypes of small and big colonies when challenged with ampicillin. This observation is consistent with the formation of elongated chains of bacteria during exponential growth phase and the occurrence of mainly rod-shaped cells in liquid media. RNA-seq analysis of small versus big colonies revealed differential regulation of at least seven genes among the colony morphotypes. Among those, bla L1 and bla L2 were transcriptionally the most strongly upregulated genes. Promoter fusions of bla L1 and bla L2 genes indicated that expression of both genes is also subject to high levels of phenotypic heterogeneous expression on a single cell level. Additionally, the comE homolog was found to be differentially expressed in homogenously versus heterogeneously bla L2 expressing cells as identified by RNA-seq analysis. Overexpression of comE in S. maltophilia K279a reduced the level of cells that were in a bla L2-ON mode to 1% or lower. Taken together, our data provide strong evidence that S. maltophilia K279a populations develop phenotypic heterogeneity in an ampicillin challenged model. This cellular variability is triggered by regulation networks including bla L1, bla L2, and comE.
authors.affiliation: Department of Microbiology and Biotechnology, Biocenter Klein Flottbek - University of Hamburg Hamburg, Germany.
authors.forename: Ebrahim M
authors.initials: EM
authors.lastname: Abda
authors.affiliation: Department of Microbiology and Biotechnology, Biocenter Klein Flottbek - University of Hamburg Hamburg, Germany.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Krysciak
authors.affiliation: Department of Microbiology and Biotechnology, Biocenter Klein Flottbek - University of Hamburg Hamburg, Germany.
authors.forename: Ines
authors.initials: I
authors.lastname: Krohn-Molt
authors.affiliation: Priority Program Asthma and Allergy, Leibniz-Center for Medicine and Biosciences - Research Center Borstel Borstel, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Mamat
authors.affiliation: Department of Microbiology and Biotechnology, Biocenter Klein Flottbek - University of Hamburg Hamburg, Germany.
authors.forename: Christel
authors.initials: C
authors.lastname: Schmeisser
authors.affiliation: Core Unit Systems Medicine, University of Würzburg Würzburg, Germany.
authors.forename: Konrad U
authors.initials: KU
authors.lastname: Förstner
authors.affiliation: Priority Program Infections, Leibniz-Center for Medicine and Biosciences - Research Center Borstel Borstel, Germany.
authors.forename: Ulrich E
authors.initials: UE
authors.lastname: Schaible
authors.affiliation: Priority Program Infections, Leibniz-Center for Medicine and Biosciences - Research Center Borstel Borstel, Germany.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Kohl
authors.affiliation: Priority Program Infections, Leibniz-Center for Medicine and Biosciences - Research Center Borstel Borstel, Germany ; German Center for Infection Research Borstel, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Nieman
authors.affiliation: Department of Microbiology and Biotechnology, Biocenter Klein Flottbek - University of Hamburg Hamburg, Germany.
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Streit
keywords: K279a; RNA-seq; Stenotrophomonas maltophilia; antibiotic resistance; colony morphotypes; phenotypic heterogeneity; β-lactamases