Ecological Niche-Inspired Genome Mining Leads to the Discovery of Crop-Protecting Nonribosomal Lipopeptides Featuring a Transient Amino Acid Building Block.

Investigating the ecological context of microbial predator-prey interactions enables the identification of microorganisms, which produce multiple secondary metabolites to evade predation or to kill the predator. In addition, genome mining combined with molecular biology methods can be used to identify further biosynthetic gene clusters that yield new antimicrobials to fight the antimicrobial crisis. In contrast, classical screening-based approaches have limitations since they do not aim to unlock the entire biosynthetic potential of a given organism. Here, we describe the genomics-based identification of keanumycins A-C. These nonribosomal peptides enable bacteria of the genus Pseudomonas to evade amoebal predation. While being amoebicidal at a nanomolar level, these compounds also exhibit a strong antimycotic activity in particular against the devastating plant pathogen Botrytis cinerea and they drastically inhibit the infection of Hydrangea macrophylla leaves using only supernatants of Pseudomonas cultures. The structures of the keanumycins were fully elucidated through a combination of nuclear magnetic resonance, tandem mass spectrometry, and degradation experiments revealing an unprecedented terminal imine motif in keanumycin C extending the family of nonribosomal amino acids by a highly reactive building block. In addition, chemical synthesis unveiled the absolute configuration of the unusual dihydroxylated fatty acid of keanumycin A, which has not yet been reported for this lipodepsipeptide class. Finally, a detailed genome-wide microarray analysis of Candida albicans exposed to keanumycin A shed light on the mode-of-action of this potential natural product lead, which will aid the development of new pharmaceutical and agrochemical antifungals.

Efficient Gene Delivery of Tailored Amphiphilic Polypeptides by Polyplex Surfing.

Within this study, an amphiphilic and potentially biodegradable polypeptide library based on poly[(4-aminobutyl)-l-glutamine-stat-hexyl-l-glutamine] [P(AB-l-Gln-stat-Hex-l-Gln)] was investigated for gene delivery. The influence of varying proportions of aliphatic and cationic side chains affecting the physicochemical properties of the polypeptides on transfection efficiency was investigated. A composition of 40 mol% Hex-l-Gln and 60 mol % AB-l-Gln (P3) was identified as best performer over polypeptides with higher proportions of protonatable monomers. Detailed studies of the transfection mechanism revealed the strongest interaction of P3 with cell membranes, promoting efficient endocytic cell uptake and high endosomal release. Spectrally, time-, and z-resolved fluorescence microscopy further revealed the crucial role of filopodia surfing in polyplex-cell interaction and particle internalization in lamellipodia regions, followed by rapid particle transport into cells. This study demonstrates the great potential of polypeptides for gene delivery. The amphiphilic character improves performance over cationic homopolypeptides, and the potential biodegradability is advantageous toward other synthetic polymeric delivery systems.

Enzyme-Primed Native Chemical Ligation Produces Autoinducing Cyclopeptides in Clostridia.

Clostridia coordinate many important processes such as toxin production, infection, and survival by density-dependent communication (quorum sensing) using autoinducing peptides (AIPs). Although clostridial AIPs have been proposed to be (thio)lactone-containing peptides, their true structures remain elusive. Here, we report the genome-guided discovery of an AIP that controls endospore formation in Ruminiclostridium cellulolyticum. Through a combination of chemical synthesis and chemical complementation assays with a mutant strain, we reveal that the genuine chemical mediator is a homodetic cyclopeptide (cAIP). Kinetic analyses indicate that the mature cAIP is produced via a cryptic thiolactone intermediate that undergoes a rapid S→N acyl shift, in a manner similar to intramolecular native chemical ligation (NCL). Finally, by implementing a chemical probe in a targeted screen, we show that this novel enzyme-primed, intramolecular NCL is a widespread feature of clostridial AIP biosynthesis.

Citizen science shows that small agricultural streams in Germany are in a poor ecological status.

Agricultural pesticides, nutrients, and habitat degradation are major causes of insect declines in lowland streams. To effectively conserve and restore stream habitats, standardized stream monitoring data and societal support for freshwater protection are needed. Here, we sampled 137 small stream monitoring sites across Germany, 83 % of which were located in agricultural catchments, with >900 citizen scientists in 96 monitoring groups. Sampling was carried out according to Water Framework Directive standards as part of the citizen science freshwater monitoring program FLOW in spring and summer 2021, 2022 and 2023. The biological indicator SPEARpesticides was used to assess pesticide exposure and effects based on macroinvertebrate community composition. Overall, 58 % of the agricultural monitoring sites failed to achieve a good ecological status in terms of macroinvertebrate community composition and indicated high pesticide exposure (SPEARpesticides status class: 29 % "moderate", 19 % "poor", 11 % "bad"). The indicated pesticide pressure in streams was related to the proportion of arable land in the catchment areas (R2 = 0.23, p < 0.001). Also with regards to hydromorphology, monitoring results revealed that 65 % of the agricultural monitoring sites failed to reach a good status. The database produced by citizen science groups was characterized by a high degree of accuracy, as results obtained by citizen scientists and professionals were highly correlated for SPEARpesticides index (R2 = 0.79, p < 0.001) and hydromorphology index values (R2 = 0.72, p < 0.001). Such citizen-driven monitoring of the status of watercourses could play a crucial role in monitoring and implementing the objectives of the European Water Framework Directive, thus contributing to restoring and protecting freshwater ecosystems.

Moonlighting Arabidopsis molybdate transporter 2 family and GSH-complex formation facilitate molybdenum homeostasis.

Molybdenum (Mo) as essential micronutrient for plants, acts as active component of molybdenum cofactor (Moco). Core metabolic processes like nitrate assimilation or abscisic-acid biosynthesis rely on Moco-dependent enzymes. Although a family of molybdate transport proteins (MOT1) is known to date in Arabidopsis, molybdate homeostasis remained unclear. Here we report a second family of molybdate transporters (MOT2) playing key roles in molybdate distribution and usage. KO phenotype-analyses, cellular and organ-specific localization, and connection to Moco-biosynthesis enzymes via protein-protein interaction suggest involvement in cellular import of molybdate in leaves and reproductive organs. Furthermore, we detected a glutathione-molybdate complex, which reveals how vacuolar storage is maintained. A putative Golgi S-adenosyl-methionine transport function was reported recently for the MOT2-family. Here, we propose a moonlighting function, since clear evidence of molybdate transport was found in a yeast-system. Our characterization of the MOT2-family and the detection of a glutathione-molybdate complex unveil the plant-wide way of molybdate.