TY  - JOUR
A1  - Liaimer, Anton
A1  - Jenke-Kodama, Holger
A1  - Ishida, Keishi
A1  - Hinrichs, Katrin
A1  - Stangeland, Janne
A1  - Hertweck, Christian
A1  - Dittmann-Thünemann, Elke
T1  - A polyketide interferes with cellular differentiation in the symbiotic cyanobacterium Nostoc punctiforme
JF  - Environmental microbiology reports
N2  - Nostoc punctiforme is a filamentous cyanobacterium capable of forming symbiotic associations with a wide range of plants. The strain exhibits extensive phenotypic characteristics and can differentiate three mutually exclusive cell types: nitrogen-fixing heterocysts, motile hormogonia and spore-like akinetes. Here, we provide evidence for a crucial role of an extracellular metabolite in balancing cellular differentiation. Insertional mutagenesis of a gene of the polyketide synthase gene cluster pks2 led to the accumulation of short filaments carrying mostly terminal heterocysts under diazotrophic conditions. The mutant has a strong tendency to form biofilms on solid surfaces as well as in liquid culture. The pks2-strain keeps forming hormogonia over the entire growth curve and shows an early onset of akinete formation. We could isolate two fractions of the wildtype supernatant that could restore the capability to form long filaments with intercalary heterocysts. Growth of the mutant cells in the neighbourhood of wild-type cells on plates led to a reciprocal influence and a partial reconstruction of wild-type and mutant phenotype respectively. We postulate that extracellular metabolites of Nostoc punctiforme act as life cycle governing factors (LCGFs) and that the ratio between distinct factors may guide the differentiation into different life stages.
Y1  - 2011
U6  - https://doi.org/10.1111/j.1758-2229.2011.00258.x
SN  - 1758-2229
VL  - 3
IS  - 5
SP  - 550
EP  - 558
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Weiz, Annika R.
A1  - Ishida, Keishi
A1  - Makower, Katharina
A1  - Ziemert, Nadine
A1  - Hertweck, Christian
A1  - Dittmann-Thünemann, Elke
T1  - Leader Peptide and a Membrane Protein Scaffold Guide the Biosynthesis of the Tricyclic Peptide Microviridin
JF  - Chemistry & biology
N2  - Microviridins are unique protease inhibitors from bloom-forming cyanobacteria that have both ecological and pharmacological relevance. Their peptide backbones are produced ribosomally, and ATP grasp ligases introduce omega-ester and omega-amide bonds to yield rare cage-like structures. Bioinformatic analysis of the microviridin biosynthesis gene cluster suggests a novel type of processing machinery, which could rationalize the challenging in vivo/in vitro reconstitution of the pathway. In this work, we report the establishment of a minimal expression system for microviridins. Through bioinformatics and mutational analysis of the MdnA leader peptide we identified and characterized a strictly conserved binding motif that is specific for microviridin ligases. Furthermore, we showed that the ABC transporter MdnE is crucial for cyclization and processing of microviridins and demonstrated that MdnE is essential for stability of the microviridin biosynthesis complex.
Y1  - 2011
U6  - https://doi.org/10.1016/j.chembiol.2011.09.011
SN  - 1074-5521
VL  - 18
IS  - 11
SP  - 1413
EP  - 1421
PB  - Cell Press
CY  - Cambridge
ER  -