TY  - JOUR
A1  - Grote, Jessica
A1  - Krysciak, Dagmar
A1  - Petersen, Katrin
A1  - Güllert, Simon
A1  - Schmeisser, Christel
A1  - Förstner, Konrad U.
A1  - Krishnan, Hari B.
A1  - Schwalbe, Harald
A1  - Kubatova, Nina
A1  - Streit, Wolfgang R.
T1  - The Absence of the N-acyl-homoserine-lactone Autoinducer Synthase Genes tral and ngrl Increases the Copy Number of the Symbiotic Plasmid in Sinorhizobium fredii NGR234
JF  - Frontiers in Microbiology
N2  - Plant-released flavonoids induce the transcription of symbiotic genes in rhizobia and one of the first bacterial responses is the synthesis of so called Nod factors. They are responsible for the initial root hair curling during onset of root nodule development. This signal exchange is believed to be essential for initiating the plant symbiosis with rhizobia affiliated with the Alphaproteobacteria. Here, we provide evidence that in the broad host range strain Sinorhizobium fredii NGR234 the complete lack of quorum sensing molecules results in an elevated copy number of its symbiotic plasmid (pNGR234a). This in turn triggers the expression of symbiotic genes and the production of Nod factors in the absence of plant signals. Therefore, increasing the copy number of specific plasmids could be a widespread mechanism of specialized bacterial populations to bridge gaps in signaling cascades.
KW  - Sinorhizobium fredii
KW  - plasmid copy number
KW  - plant symbioses
KW  - quorum sensing (QS)
KW  - RNA sequencing (RNA-Seq)
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-165185
VL  - 7
IS  - 1858
ER  - 
TY  - JOUR
A1  - Abda, Ebrahim M.
A1  - Krysciak, Dagmar
A1  - Krohn-Molt, Ines
A1  - Mamat, Uwe
A1  - Schmeisser, Christel
A1  - Förstner, Konrad U.
A1  - Schaible, Ulrich E.
A1  - Kohi, Thomas A.
A1  - Nieman, Stefan
A1  - Streit, Wolfgang R.
T1  - Phenotypic Heterogeneity Affects Stenotrophomonas maltophilia K279a Colony Morphotypes and \(\beta\)-Lactamase Expression
JF  - Frontiers in Microbiology
N2  - 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 rnaltophilia 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 Li and L2 beta-lactamases in response to beta-lactam treatment. Here we report that the patient isolate S. rnaltophilia 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, bleu and bla(L2) were transcriptionally the most strongly upregulated genes. Promoter fusions of b/a(L1) and b/a(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 cornE 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 b/a(L1), b/a(L2), and comE.
KW  - xanthomonas maltophilia
KW  - gram-negative bacteria
KW  - RNA-seq
KW  - pseudomas aeruginosa
KW  - antibiotic resistance
KW  - colony morphotypes
KW  - beta-lactamases
KW  - K279a
KW  - Stenotrophomonas maltophilia
KW  - phenotypic heterogeneity
KW  - persister cells
KW  - streptococcus pneumoniae
KW  - nosocomial pathogen
KW  - membrane vesicles
KW  - sinorhizobium fredii NGR234
KW  - red fluorescent protein
KW  - escherichia coli
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-136446
VL  - 6
IS  - 1373
ER  -