Serratia marcescens and several other bacteria produce the red-colored pigment prodigiosin which possesses bioactivities as an antimicrobial, anticancer, and immunosuppressive agent. Therefore, there is a great interest to produce this natural compound. Efforts aiming at its biotechnological production have so far largely focused on the original producer and opportunistic human pathogen S. marcescens. Here, we demonstrate efficient prodigiosin production in the heterologous host Pseudomonas putida. Random chromosomal integration of the 21 kb prodigiosin biosynthesis gene cluster of S. marcescens in P. putida KT2440 was employed to construct constitutive prodigiosin production strains. Standard cultivation parameters were optimized such that titers of 94 mg/L culture were obtained upon growth of P. putida at 20°C using rich medium under high aeration conditions. Subsequently, a novel, fast and effective protocol for prodigiosin extraction and purification was established enabling the straightforward isolation of prodigiosin from P. putida growth medium. In summary, we describe here a highly efficient method for the heterologous biosynthetic production of prodigiosin which may serve as a basis to produce large amounts of this bioactive natural compound and may provide a platform for further in-depth studies of prodiginine biosynthesis.

Metal-organic coordination networks (MOCNs) formed by coordination bonding between metallic centers and organic ligands can be efficiently engineered to exhibit specific magnetic, electronic, or catalytic properties [1]. Instead of depositing prefabricated MOCNs onto surfaces, it has been recently shown that two-dimensional (2D) MOCNs can be directly grown at metal surfaces under ultrahigh vacuum (UHV), thus creating highly regular 2D networks of metal atoms [2]. We show here [3] that this approach allows to predefine the geometry of the MOCN by using the substrate as a template to direct the formation of novel 1D metal-organic coordination chains (MOCCs).The templating role of substrates is well known in the field of surface epitaxial growth. Among the highly anisotropic substrates, the Cu(110) surface is one of the most commonly used. To demonstrate its strong 1D templating effect on organic molecules, a ligand with a triangular symmetry was selected, namely 1,3,5-benzenetri-carboxylic acid (trimesic acid, TMA). The three-fold rotation symmetry of TMA supports the formation of hexagonal 2D and 3D architectures, therefore strongly disfavoring the linear geometry.The deposition of TMA on Cu(110) under UHV at 300 K results in the formation of 1D chains along the <1bar10> direction, as observed by scanning tunneling microscopy (STM). This deposition temperature is high enough to provide mobile Cu adatoms through evaporation from kinks and steps onto the terraces. Analysis of similar systems by X-ray photoelectron spectroscopy showed that these adatoms catalyze the deprotonation of molecular carboxylate groups and are necessary for the formation of copper carboxylate complexes. The chains formed at 300 K typically show irregular kinks and poor long-range order. These inhomogeneities are removed by postannealing to 380-410 K to yield straight and highly periodic chains, referred to as MOCC-I hereafter.

The adsorption of trimesic acid (TMA) on Cu(110) has been studied in the temperature range between 130 and 550 K and for coverages up to one monolayer. We combine scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), reflection absorption infrared spectroscopy (RAIRS), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations to produce a detailed adsorption phase diagram for the TMA/Cu(110) system as a function of the molecular coverage and the substrate temperature. We identify a quite complex set of adsorption phases, which are determined by the interplay between the extent of deprotonation, the intermolecular bonding, and the overall energy minimization. For temperatures up to 280 K, TMA molecules are only partly deprotonated and form hydrogen-bonded structures, which locally exhibit organizational chirality. Above this threshold, the molecules deprotonate completely and form supramolecular metal-organic structures with Cu substrate adatoms. These structures exist in the form of single and double coordination chains, with the molecular coverage driving distinct phase transitions.

Understanding the deactivation mechanism of 2-deoxy-d-ribose-5-phosphate aldolase by its natural substrate leads to a single mutant showing complete acetaldehyde resistance.