Metabolomics; high-resolution mass spectrometry; secondary metabolite induction; culture conditionsPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.1. Introduction Cyanobacteria are Gram-negative photosynthetic prokaryotes which will be found in all environments and habitats like extreme circumstances. They play an crucial part inside the functioning of a variety of ecosystems because of their involvement in primary production via oxygenic photosynthesis. They have been shown to include the pigments phycocyanin and phycoerythrin, also to chlorophyll a [1]. Cyanobacteria make a wide wide variety of bioactive metabolites, extra than 1100 of which happen to be described to date [2]. This array of metabolites seems to assistance the remarkable ecological capacities of cyanobacteria [3]. As a consequence, cyanobacteria would be the organisms of option for researching procedures for production of important bioactive molecules. Scientific fields such asCopyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This short article is definitely an open access post distributed below the terms and circumstances of the Inventive Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ four.0/).Metabolites 2021, 11, 745. https://doi.org/10.3390/metabohttps://www.mdpi.com/journal/metabolitesMetabolites 2021, 11,2 ofpharmacology, the meals sector, and biotechnology are actively exploring their properties for potential commercialization [4,5]. Cyanobacteria also present promising applications inside the field of cosmetics due to their production of many Polmacoxib custom synthesis molecules with photo-protective, antioxidant, or anti-inflammatory properties, including carotenoids, mycosporine-like amino acids (MAAs), and scytonemins [5]. Several of your diverse cyanobacterial secondary metabolites are peptides or exhibit peptide-like structures [8]. They are synthesized by way of precise enzymatic pathways [2] through either ribosomal (ribosomally synthesized and post-translationally modified peptides: RiPPs) or non-ribosomal (non-ribosomal peptide synthase, NRPS, or polyketide synthase, PKS) pathways [9]. Other vital secondary metabolites can present various structural organizations that belong to chemical classes for example alkaloids, terpenes, 2-Bromo-6-nitrophenol Epigenetics polysaccharides, or even lipids [10]. Regardless of lots of decades of operate, the biological roles of the vast majority of those cyanobacterial secondary metabolites remain unknown [11]. Many hypotheses regarding their respective potential biological functions (e.g., allelopathy, defense, parasitism/symbiosis, chemical communication, etc.) happen to be proposed [12]. There have already been a somewhat large number of studies performed around the effects of physiological status or development phase on the production of targeted molecules in vitro [13], but only a couple of of those have been focused on the entire cyanobacterial metabolome and its dynamics over time and beneath distinctive culture situations [14]. Interestingly, a pilot study performed on diatoms [15] demonstrated a clear dependence of metabolic profiles on distinctive development phases: exponential, stationary, and senescent. Various components are believed to influence the growth of cyanobacteria, like temperature, light, and nutrient availability. Some researchers have shown that a temperature of 25 C enhanced the growth of bloom-forming Microcystis strains though a lack of light or nutrients negatively impacted the development of cyanobacteria [1.