Chlorflavonin Targets Acetohydroxyacid Synthase Catalytic Subunit IlvB1 for Synergistic Killing of Mycobacterium tuberculosis

The anti-tubercular callyaerins target the Mycobacterium tuberculosis-specific non-essential membrane protein Rv2113

Spread of antimicrobial resistances urges a need for new drugs against Mycobacterium tuberculosis (Mtb) with mechanisms differing from current antibiotics. Previously, callyaerins were identified as promising anti-tubercular agents, representing a class of hydrophobic cyclopeptides with an unusual (Z)-2,3-di-aminoacrylamide unit. Here, we investigated the molecular mechanisms underlying their antimycobacterial properties. Structure-activity relationship studies enabled the identification of structural determinants relevant for antibacterial activity. Callyaerins are bacteriostatics selectively active against Mtb, including extensively drug-resistant strains, with minimal cytotoxicity against human cells and promising intracellular activity. By combining mutant screens and various chemical proteomics approaches, we showed that callyaerins target the non-essential, Mtb-specific membrane protein Rv2113, triggering a complex dysregulation of the proteome, characterized by global downregulation of lipid biosynthesis, cell division, DNA repair, and replication. Our study thus identifies Rv2113 as a previously undescribed Mtb-specific drug target and demonstrates that also non-essential proteins may represent efficacious targets for antimycobacterial drugs.

Amino Acid Biosynthesis Inhibitors in Tuberculosis Drug Discovery

According to the latest World Health Organization (WHO) report, an estimated 10.6 million people were diagnosed with tuberculosis (TB) in 2022, and 1.30 million died. A major concern is the emergence of multi-drug-resistant (MDR) and extensively drug-resistant (XDR) strains, fueled by the length of anti-TB treatment and HIV comorbidity. Innovative anti-TB agents acting with new modes of action are the only solution to counteract the spread of resistant infections. To escape starvation and survive inside macrophages, Mtb has evolved to become independent of the host by synthesizing its own amino acids. Therefore, targeting amino acid biosynthesis could subvert the ability of the mycobacterium to evade the host immune system, providing innovative avenues for drug discovery. The aim of this review is to give an overview of the most recent progress in the discovery of amino acid biosynthesis inhibitors. Among the hits discovered over the past five years, tryptophan (Trp) inhibitors stand out as the most advanced and have significantly contributed to demonstrating the feasibility of this approach for future TB drug discovery. Future efforts should be directed at prioritizing the chemical optimization of these hits to enrich the TB drug pipeline with high-quality leads.

AflaILVB/G/I and AflaILVD are involved in mycelial production, aflatoxin biosynthesis, and fungal virulence in Aspergillus flavus

Aflatoxins (AFs) are produced by fungi such as Aspergillus flavus and A. parasiticus and are one of the most toxic mycotoxins found in agricultural products and food. Aflatoxin contamination, which requires the control of A. flavus, remains problematic because of the lack of effective strategies and the exploration of new compounds that can inhibit A. flavus growth and mycotoxin production is urgently required to alleviate potential deleterious effects. Acetohydroxy acid synthase (AHAS) and dihydroxy acid dehydratase are important enzymes in the biosynthetic pathways of branched-chain amino acids (BCAAs), including isoleucine, leucine, and valine. Enzymes involved in BCAA biosynthesis are present in bacteria, plants, and fungi, but not in mammals, and are therefore, attractive targets for antimicrobial and herbicide development. In this study, we characterized AflaILVB/G/I and AflaILVD, which encode the catalytic and regulatory subunits of AHAS and dihydroxy acid dehydratase, from the pathogenic fungus Aspergillus flavus. The AflaILVB/G/I and AflaILVD deletion mutant grew slower and produced smaller colonies than the wild-type strain when grown on glucose minimal medium, potato dextrose agar, and yeast extract medium for three days at 28°C, and disruption of AflaILVB/G/I caused a significant reduction in conidia production when grown on all kinds of media. Cellular stress assays determined that all strains were sensitive to H2O2. Importantly, the pathogenicity and aflatoxin production were affected when AflaILVB/G/I and AflaILVD were knocked out, particularly AflaILVB/G/I. A series of genes that encoded enzymes involved in aflatoxin synthesis were downregulated, meaning that the knockout of AflaILVB/G/I influenced aflatoxin synthesis in A. flavus strain WT. Collectively, our results demonstrate the potential value of antifungals targeting AflaILVB/G/I in A. flavus.

Antimicrobial Action Mechanisms of Natural Compounds Isolated from Endophytic Microorganisms

Infectious diseases are a significant challenge to global healthcare, especially in the face of increasing antibiotic resistance. This urgent issue requires the continuous exploration and development of new antimicrobial drugs. In this regard, the secondary metabolites derived from endophytic microorganisms stand out as promising sources for finding antimicrobials. Endophytic microorganisms, residing within the internal tissues of plants, have demonstrated the capacity to produce diverse bioactive compounds with substantial pharmacological potential. Therefore, numerous new antimicrobial compounds have been isolated from endophytes, particularly from endophytic fungi and actinomycetes. However, only a limited number of these compounds have been subjected to comprehensive studies regarding their mechanisms of action against bacterial cells. Furthermore, the investigation of their effects on antibiotic-resistant bacteria and the identification of biosynthetic gene clusters responsible for synthesizing these secondary metabolites have been conducted for only a subset of these promising compounds. Through a comprehensive analysis of current research findings, this review describes the mechanisms of action of antimicrobial drugs and secondary metabolites isolated from endophytes, antibacterial activities of the natural compounds derived from endophytes against antibiotic-resistant bacteria, and biosynthetic gene clusters of endophytic fungi responsible for the synthesis of bioactive secondary metabolites.

New Meroterpenoid Derivatives from the Pomegranate-Derived Endophytic Fungus Talaromyces purpureogenus

In this study, we report the isolation of two new meroterpenoids, miniolutelide D (1) and miniolutelide E (13-epi-miniolutelide C) (2), along with two meroterpenoidal analogues (3 and 4) and two phenolic compounds (5 and 6) from the endophytic fungus Talaromyces purpureogenus derived from Punica granatum fruits. Their structures were elucidated using extensive MS, 1D, and 2D NMR spectroscopic analyses as well as by comparing with data in the literature. The absolute configurations of 1 and 2 were determined using TDDFT-ECD calculations. Antimicrobial activity was evaluated. Compound 5 displayed significant activity against methicillin-resistant Staphylococcus aureus strain ATCC 700699 and moderate activity against S. aureus strain ATCC 29213.

Microbial glycosylation of antitubercular agent chlorflavonin

Flavonoids have shown health-benefiting properties, such as antioxidative and anti-inflammatory activities, and are commonly used as nutraceuticals and pharmaceuticals. Although flavonoids are predominantly identified from plants, several filamentous fungal species have also been reported to produce bioactive flavonoids, including chlorflavonin from Aspergillus candidus, a novel halogenated flavonoid with potent antifungal and antitubercular (anti-TB) activities. Unfortunately, the low water-solubility of this molecule may hinder its bioavailability. Glycosylation is an effective method to enhance the polarity of natural products and alter their physicochemical properties. This work focuses on the development of novel water-soluble chlorflavonin derivatives to combat the threat of drug-resistant tuberculosis. In this study, we first increased the production titer of chlorflavonin in A. candidus NRRL 5214 by optimizing the fermentation and purification processes. Next, chlorflavonin-5-O-β-d-glucuronopyranoside (1) and chlorflavonin-7-O-4″-O-methyl-β-d-glucopyranoside (2) were produced from chlorflavonin using Streptomyces chromofuscus ATCC 49982 and Beauveria bassiana ATCC 7159, respectively. Compared to chlorflavonin (4.38 ± 0.54 mg/L in water), the water solubility of the two new glycosides was determined to be 117.86 ± 4.81 mg/L (1) and 124.34 ± 9.13 mg/L (2), respectively. This study provides a promising method to create water-soluble glycosides of chlorflavonin for the development of novel anti-TB drugs.

Natural products and their analogues acting against Mycobacterium tuberculosis: A recent update

Tuberculosis (TB) remains one of the deadliest infectious diseases caused by Mycobacterium tuberculosis (M.tb). It is responsible for significant causes of mortality and morbidity worldwide. M.tb possesses robust defense mechanisms against most antibiotic drugs and host responses due to their complex cell membranes with unique lipid molecules. Thus, the efficacy of existing front-line drugs is diminishing, and new and recurring cases of TB arising from multidrug-resistant M.tb are increasing. TB begs the scientific community to explore novel therapeutic avenues. A precise knowledge of the compounds with their mode of action could aid in developing new anti-TB agents that can kill latent and actively multiplying M.tb. This can help in the shortening of the anti-TB regimen and can improve the outcome of treatment strategies. Natural products have contributed several antibiotics for TB treatment. The sources of anti-TB drugs/inhibitors discussed in this work are target-based identification/cell-based and phenotypic screening from natural products. Some of the recently identified natural products derived leads have reached clinical stages of TB drug development, which include rifapentine, CPZEN-45, spectinamide-1599 and 1810. We believe these anti-TB agents could emerge as superior therapeutic compounds to treat TB over known Food and Drug Administration drugs.

Clp-targeting BacPROTACs impair mycobacterial proteostasis and survival

The ClpC1:ClpP1P2 protease is a core component of the proteostasis system in mycobacteria. To improve the efficacy of antitubercular agents targeting the Clp protease, we characterized the mechanism of the antibiotics cyclomarin A and ecumicin. Quantitative proteomics revealed that the antibiotics cause massive proteome imbalances, including upregulation of two unannotated yet conserved stress response factors, ClpC2 and ClpC3. These proteins likely protect the Clp protease from excessive amounts of misfolded proteins or from cyclomarin A, which we show to mimic damaged proteins. To overcome the Clp security system, we developed a BacPROTAC that induces degradation of ClpC1 together with its ClpC2 caretaker. The dual Clp degrader, built from linked cyclomarin A heads, was highly efficient in killing pathogenic Mycobacterium tuberculosis, with >100-fold increased potency over the parent antibiotic. Together, our data reveal Clp scavenger proteins as important proteostasis safeguards and highlight the potential of BacPROTACs as future antibiotics.

Engineered production of bioactive polyphenolic O-glycosides

Polyphenolic compounds (such as quercetin and resveratrol) possess potential medicinal values due to their various bioactivities, but poor water solubility hinders their health benefits to humankind. Glycosylation is a well-known post-modification method to biosynthesize natural product glycosides with improved hydrophilicity. Glycosylation has profound effects on decreasing toxicity, increasing bioavailability and stability, together with changing bioactivity of polyphenolic compounds. Therefore, polyphenolic glycosides can be used as food additives, therapeutics, and nutraceuticals. Engineered biosynthesis provides an environmentally friendly and cost-effective approach to generate polyphenolic glycosides through the use of various glycosyltransferases (GTs) and sugar biosynthetic enzymes. GTs transfer the sugar moieties from nucleotide-activated diphosphate sugar (NDP-sugar) donors to sugar acceptors such as polyphenolic compounds. In this review, we systematically review and summarize the representative polyphenolic O-glycosides with various bioactivities and their engineered biosynthesis in microbes with different biotechnological strategies. We also review the major routes towards NDP-sugar formation in microbes, which is significant for producing unusual or novel glycosides. Finally, we discuss the trends in NDP-sugar based glycosylation research to promote the development of prodrugs that positively impact human health and wellness.

Discovery of a Unique Flavonoid Biosynthesis Mechanism in Fungi by Genome Mining

Flavonoids are important plant natural products with variable structures and bioactivities. All known plant flavonoids are generated under the catalysis of a type III polyketide synthase (PKS) followed by a chalcone isomerase (CHI) and a flavone synthase (FNS). In this study, the biosynthetic gene cluster of chlorflavonin, a fungal flavonoid with acetolactate synthase inhibitory activity, was discovered using a self-resistance-gene-directed strategy. A novel flavonoid biosynthetic pathway in fungi was revealed. A core nonribosomal peptide synthetase-polyketide synthase (NRPS-PKS) is responsible for the generation of the key precursor chalcone. Then, a new type of CHI catalyzes the conversion of a chalcone into a flavanone by a histidine-mediated oxa-Michael addition mechanism. Finally, the desaturation of flavanone to flavone is catalyzed by a new type of FNS, a flavin mononucleotide (FMN)-dependent oxidoreductase.

In Vitro Biological Activity of Natural Products from the Endophytic Fungus Paraboeremia selaginellae against Toxoplasma gondii

Toxoplasma gondii is an apicomplexan pathogen able to infect a wide range of warm-blooded animals, including humans, leading to toxoplasmosis. Current treatments for toxoplasmosis are associated with severe side-effects and a lack efficacy to eradicate chronic infection. Thus, there is an urgent need for developing novel, highly efficient agents against toxoplasmosis with low toxicity. For decades, natural products have been a useful source of novel bioactive compounds for the treatment of infectious pathogens. In the present study, we isolated eight natural products from the crude extract of the endophytic fungus Paraboeremia selaginellae obtained from the leaves of the plant Philodendron monstera. The natural products were tested for inhibiting Toxoplasma gondii proliferation, and their cytotoxicity was evaluated in different human cell lines. Six natural products showed antitoxoplasma activity with low or no cytotoxicity in human cell lines. Together, these findings indicate that biphenyl ethers, bioxanthracenes, and 5S,6S-phomalactone from P. selaginellae are potential candidates for novel anti-toxoplasma drugs.

Total Synthesis of the Antimycobacterial Natural Product Chlorflavonin and Analogs via a Late-Stage Ruthenium(II)-Catalyzed ortho-C(sp2)-H-Hydroxylation

The continuous, worldwide spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) endanger the World Health Organization’s (WHO) goal to end the global TB pandemic by the year 2035. During the past 50 years, very few new drugs have been approved by medical agencies to treat drug-resistant TB. Therefore, the development of novel antimycobacterial drug candidates to combat the threat of drug-resistant TB is urgent. In this work, we developed and optimized a total synthesis of the antimycobacterial natural flavonoid chlorflavonin by selective ruthenium(II)-catalyzed ortho-C(sp²)-H-hydroxylation of a substituted 3′-methoxyflavonoid skeleton. We extended our methodology to synthesize a small compound library of 14 structural analogs. The new analogs were tested for their antimycobacterial in vitro activity against Mycobacterium tuberculosis (Mtb) and their cytotoxicity against various human cell lines. The most promising new analog bromflavonin exhibited improved antimycobacterial in vitro activity against the virulent H37Rv strain of Mtb (Minimal Inhibitory Concentrations (MIC₉₀) = 0.78 μm). In addition, we determined the chemical and metabolic stability as well as the pK_a values of chlorflavonin and bromflavonin. Furthermore, we established a quantitative structure–activity relationship model using a thermodynamic integration approach. Our computations may be used for suggesting further structural changes to develop improved derivatives.

Fungal Endophytes: A Potential Source of Antibacterial Compounds

Antibiotic resistance is becoming a burning issue due to the frequent use of antibiotics for curing common bacterial infections, indicating that we are running out of effective antibiotics. This has been more obvious during recent corona pandemics. Similarly, enhancement of antimicrobial resistance (AMR) is strengthening the pathogenicity and virulence of infectious microbes. Endophytes have shown expression of various new many bioactive compounds with significant biological activities. Specifically, in endophytic fungi, bioactive metabolites with unique skeletons have been identified which could be helpful in the prevention of increasing antimicrobial resistance. The major classes of metabolites reported include anthraquinone, sesquiterpenoid, chromone, xanthone, phenols, quinones, quinolone, piperazine, coumarins and cyclic peptides. In the present review, we reported 451 bioactive metabolites isolated from various groups of endophytic fungi from January 2015 to April 2021 along with their antibacterial profiling, chemical structures and mode of action. In addition, we also discussed various methods including epigenetic modifications, co-culture, and OSMAC to induce silent gene clusters for the production of noble bioactive compounds in endophytic fungi.

Natural products against key Mycobacterium tuberculosis enzymatic targets: Emerging opportunities for drug discovery

For centuries, natural products (NPs) have served as powerful therapeutics against a variety of human ailments. Nowadays, they still represent invaluable resources for the treatment of many diseases, including bacterial infections. After nearly three decades since the World Health Organization's (WHO) declaration of tuberculosis (TB) as a global health emergency, Mycobacterium tuberculosis (Mtb) continues to claim millions of lives, remaining among the leading causes of death worldwide. In the last years, several efforts have been devoted to shortening and improving treatment outcomes, and to overcoming the increasing resistance phenomenon. Nature has always provided a virtually unlimited source of bioactive molecules, which have inspired the development of new drugs. NPs are characterized by an exceptional chemical and structural diversity, the result of millennia of evolutionary responses to various stimuli. Thanks to their favorable structural features and their enzymatic origin, they are naturally prone to bind proteins and exhibit bioactivities. Furthermore, their worldwide distribution and ease of accessibility has contributed to promote investigations on their activity. Overall, these characteristics make NPs excellent models for the design of novel therapeutics. This review offers a critical and comprehensive overview of the most promising NPs, isolated from plants, fungi, marine species, and bacteria, endowed with inhibitory properties against traditional and emerging mycobacterial enzymatic targets. A selection of 86 compounds is here discussed, with a special emphasis on their biological activity, structure-activity relationships, and mechanism of action. Our study corroborates the antimycobacterial potential of NPs, substantiating their relevance in future drug discovery and development efforts.

Induction of New Lactam Derivatives From the Endophytic Fungus Aplosporella javeedii Through an OSMAC Approach

Fermentation of the endophytic fungus Aplosporella javeedii on solid rice medium in presence of either 3.5% NaNO3 or 3.5% monosodium glutamate caused a significant change of the fungal metabolite pattern compared to fungal controls grown only on rice. Chemical investigation of the former fungal extracts yielded 11 new lactam derivatives, aplosporellins A-K (2-12), in addition to the known compound, pramanicin A (1). All of these compounds were not detected when the fungus was grown on rice medium without these activators thereby indicating the power of this OSMAC approach. The structures of the new compounds were elucidated by one- and two- dimensional NMR spectroscopy, DFT-NMR calculations and by mass spectrometry as well as by comparison with the literature whereas the absolute configuration of the lactam core was determined by TDDFT-ECD and OR calculations. Pramanicin A (1) showed strong cytotoxicity against human lymphoma (Ramos) and leukemia (Jurkat J16) cells with IC50 values of 4.7 and 4.4 μM, respectively. Mechanistic studies indicated that 1 activates caspase-3 and induces apoptotic cell death.

Nature-Inspired (di)Azine-Bridged Bisindole Alkaloids with Potent Antibacterial In Vitro and In Vivo Efficacy against Methicillin-Resistant Staphylococcus aureus

Natural bisindole alkaloids such as Hyrtinadine A and Alocasin A, which are known to exhibit diverse bioactivities, provide promising chemical scaffolds for drug development. By optimizing the Masuda borylation-Suzuki coupling sequence, a library of various natural product-derived and non-natural (di)azine-bridged bisindoles was created. While unsubstituted bisindoles were devoid of antibacterial activity, 5,5'-chloro derivatives were highly active against methicillin-resistant Staphylococcus aureus (MRSA) and further Gram-positive pathogens at minimal inhibitory concentrations ranging from 0.20 to 0.78 μM. These compounds showed strong bactericidal killing effects but only moderate cytotoxicity against human cell lines. Furthermore, the two front-runner compounds 4j and 4n exhibited potent in vivo efficacy against MRSA in a mouse wound infection model. Although structurally related bisindoles were reported to specifically target pyruvate kinase in MRSA, antibacterial activity of 4j and 4n is independent of pyruvate kinase. Rather, these compounds lead to bacterial membrane permeabilization and cellular efflux of low-molecular-weight molecules.

Endophytic Fungi in the Fight Against Neglected Tropical Diseases

Neglected tropical diseases are a serious global public health problem and they are one of the main causes of mortality and morbidity, especially in underdeveloped countries. These diseases have several implications for health and they are considered a priority in global eradication programs for disease control. The aim of this mini-review is to report recent studies on the fight against neglected diseases, namely dengue fever, chikungunya, zika, malaria protozoa, Chagas disease, leishmaniasis, schistosomiasis helminths, filariasis, and tuberculosis bacteria using extracts and isolated substances of endophytic fungi based on their bioactivity profiles in relation to these diseases.

Sesterterpenes and macrolide derivatives from the endophytic fungus Aplosporella javeedii

Five sesterterpenes (1-5) including two new compounds (1 and 2), as well as a new (6) and a known macrolide (7) were isolated from the endophytic fungus Aplosporella javeedii. The structures of the new compounds were elucidated by analysis of their 1D and 2D NMR and HRMS data as well as by comparison with the literature. Compound 4 and its acetyl derivatives 4a, 4b, 4c which were prepared by acetylation of 4 exhibited moderate cytotoxicity against the mouse lymphoma cell line L5178Y with IC₅₀ values ranging from 6.2 to 12.8 μM, respectively. Moreover, 4a and 4c exhibited also cytotoxicity against human leukemia (Jurkat J16) and lymphoma (Ramos) cell lines. Compound 7 showed strong cytotoxicity against the L5178Y cell line, as well as against human Jurkat J16 and Ramos cells with IC₅₀ values of 0.4, 5.8, and 4.4 μM, respectively. Mechanistic studies indicated that 7 induces apoptotic cell death. In addition, compounds 3, 4 and 7 showed low antibacterial activities against Mycobacterium tuberculosis H37Rv and compound 6 against Staphylococcus aureus, respectively, with MICs of 100 μM. Preliminary structure-activity relationships are discussed.

Bioactive Secondary Metabolites from Endophytic Fungi

Background:

Endophytes represent a complex community of microorganisms colonizing asymptomatically internal tissues of higher plants. Several reports have shown that endophytes enhance the fitness of their host plants by direct production of bioactive secondary metabolites, which are involved in protecting the host against herbivores and pathogenic microbes. In addition, it is increasingly apparent that endophytes are able to biosynthesize medicinally important “phytochemicals”, originally believed to be produced only by their host plants.

Objective:

The present review provides an overview of secondary metabolites from endophytic fungi with pronounced biological activities covering the literature between 2010 and 2017. Special focus is given on studies aiming at exploration of the mode of action of these metabolites towards the discovery of leads from endophytic fungi. Moreover, this review critically evaluates the potential of endophytic fungi as alternative sources of bioactive “plant metabolites”.

Results:

Over the past few years, several promising lead structures from endophytic fungi have been described in the literature. In this review, 65 metabolites are outlined with pronounced biological activities, primarily as antimicrobial and cytotoxic agents. Some of these metabolites have shown to be highly selective or to possess novel mechanisms of action, which hold great promises as potential drug candidates.

Conclusion:

Endophytes represent an inexhaustible reservoir of pharmacologically important compounds. Moreover, endophytic fungi could be exploited for the sustainable production of bioactive “plant metabolites” in the future. Towards this aim, further insights into the dynamic endophyte - host plant interactions and origin of endophytic fungal genes would be of utmost importance.

3-O-Methyl-Alkylgallates Inhibit Fatty Acid Desaturation in Mycobacterium tuberculosis

In the quest for new antibacterial lead structures, activity screening against Mycobacterium tuberculosis identified antitubercular effects of gallic acid derivatives isolated from the Nigerian mistletoe Loranthus micranthus Structure-activity relationship studies indicated that 3-O-methyl-alkylgallates comprising aliphatic ester chains with four to eight carbon atoms showed the strongest growth inhibition in vitro against M. tuberculosis, with a MIC of 6.25 μM. Furthermore, the most active compounds (3-O-methyl-butyl-, 3-O-methyl-hexylgallate, and 3-O-methyl-octylgallate) were devoid of cytotoxicity against various human cell lines. Furthermore, 3-O-methyl-butylgallate showed favorable absorption, distribution, metabolism, and excretion (ADME) criteria, with a Papp of 6.2 × 10-6 cm/s, and it did not inhibit P-glycoprotein (P-gp), CYP1A2, CYP2B6 or CYP3A4. Whole-genome sequencing of spontaneous resistant mutants indicated that the compounds target the stearoyl-coenzyme A (stearoyl-CoA) delta-9 desaturase DesA3 and thereby inhibit oleic acid synthesis. Supplementation assays demonstrated that oleic acid addition to the culture medium antagonizes the inhibitory properties of gallic acid derivatives and that sodium salts of saturated palmitic and stearic acid did not show compensatory effects. The moderate bactericidal effect of 3-O-methyl-butylgallate in monotreatment was synergistically enhanced in combination treatment with isoniazid, leading to sterilization in liquid culture.

(Some) current concepts in antibacterial drug discovery

The rise of multidrug resistance in bacteria rendering pathogens unresponsive to many clinical drugs is widely acknowledged and considered a critical global healthcare issue. There is broad consensus that novel antibacterial chemotherapeutic options are extremely urgently needed. However, the development pipeline of new antibacterial drug lead structures is poorly filled and not commensurate with the scale of the problem since the pharmaceutical industry has shown reduced interest in antibiotic development in the past decades due to high economic risks and low profit expectations. Therefore, academic research institutions have a special responsibility in finding novel treatment options for the future. In this mini review, we want to provide a broad overview of the different approaches and concepts that are currently pursued in this research field.