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The human pathogenic bacterium Pseudomonas aeruginosa produces rhamnolipids, glycolipids with functions for bacterial motility, biofilm formation, and uptake of hydrophobic substrates. Rhamnolipids represent a chemically heterogeneous group of secondary metabolites composed of one or two rhamnose molecules linked to one or mostly two 3-hydroxyfatty acids of various chain lengths. The biosynthetic pathway involves rhamnosyltransferase I encoded by the rhlAB operon, which synthesizes 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) followed by their coupling to one rhamnose moiety. The resulting mono-rhamnolipids are converted to di-rhamnolipids in a third reaction catalyzed by the rhamnosyltransferase II RhlC. However, the mechanism behind the biosynthesis of rhamnolipids containing only a single fatty acid is still unknown. To understand the role of proteins involved in rhamnolipid biosynthesis the heterologous expression of rhl -genes in non-pathogenic Pseudomonas putida KT2440 strains was used in this study to circumvent the complex quorum sensing regulation in P . aeruginosa . Our results reveal that RhlA and RhlB are independently involved in rhamnolipid biosynthesis and not in the form of a RhlAB heterodimer complex as it has been previously postulated. Furthermore, we demonstrate that mono-rhamnolipids provided extracellularly as well as HAAs as their precursors are generally taken up into the cell and are subsequently converted to di-rhamnolipids by P . putida and the native host P . aeruginosa . Finally, our results throw light on the biosynthesis of rhamnolipids containing one fatty acid, which occurs by hydrolyzation of typical rhamnolipids containing two fatty acids, valuable for the production of designer rhamnolipids with desired physicochemical properties.

Rhamnolipids are glycolipidic biosurfactants produced by various bacterial species. They were initially found as exoproducts of the opportunistic pathogen Pseudomonas aeruginosa and described as a mixture of four congeners: α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-Rha-C₁₀-C₁₀), α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoate (Rha-Rha-C₁₀), as well as their mono-rhamnolipid congeners Rha-C₁₀-C₁₀ and Rha-C₁₀. The development of more sensitive analytical techniques has lead to the further discovery of a wide diversity of rhamnolipid congeners and homologues (about 60) that are produced at different concentrations by various Pseudomonas species and by bacteria belonging to other families, classes, or even phyla. For example, various Burkholderia species have been shown to produce rhamnolipids that have longer alkyl chains than those produced by P. aeruginosa. In P. aeruginosa, three genes, carried on two distinct operons, code for the enzymes responsible for the final steps of rhamnolipid synthesis: one operon carries the rhlAB genes and the other rhlC. Genes highly similar to rhlA, rhlB, and rhlC have also been found in various Burkholderia species but grouped within one putative operon, and they have been shown to be required for rhamnolipid production as well. The exact physiological function of these secondary metabolites is still unclear. Most identified activities are derived from the surface activity, wetting ability, detergency, and other amphipathic-related properties of these molecules. Indeed, rhamnolipids promote the uptake and biodegradation of poorly soluble substrates, act as immune modulators and virulence factors, have antimicrobial activities, and are involved in surface motility and in bacterial biofilm development.

Phosphorus supply is a major factor responsible for reduced crop yields. As a result, plants utilize various adaptive mechanisms against phosphorus depletion, including lipid remodelling. Here we report the involvement of a novel plant lipid, glucuronosyldiacylglycerol, against phosphorus depletion. Lipidomic analysis of Arabidopsis plants cultured in phosphorus-depleted conditions revealed inducible accumulation of glucuronosyldiacylglycerol. Investigation using a series of sulfolipid sulfoquinovosyldiacylglycerol synthesis-deficient mutants of Arabidopsis determined that the biosynthesis of glucuronosyldiacylglycerol shares the pathway of sulfoquinovosyldiacylglycerol synthesis in chloroplasts. Under phosphorus-depleted conditions, the Arabidopsis sqd2 mutant, which does not accumulate either sulfoquinovosyldiacylglycerol or glucuronosyldiacylglycerol, was the most severely damaged of three sulfoquinovosyldiacylglycerol-deficient mutants. As glucuronosyldiacylglycerol is still present in the other two mutants, this result indicates that glucuronosyldiacylglycerol has a role in the protection of plants against phosphorus limitation stress. Glucuronosyldiacylglycerol was also found in rice, and its concentration increased significantly following phosphorus limitation, suggesting a shared physiological significance of this novel lipid against phosphorus depletion in plants. Phosphorus supply is one of the major factors responsible for reduced crop yields. Here Okazaki et al. use untargeted lipidomics to elucidate the biosynthetic pathway of a novel plant lipid, glucuronosyldiacylglycerol, which is essential for the protection of plants against phosphorus depletion.

Approximately 80% of the Earth’s biosphere is cold, at an average temperature of 5°C, and is populated by a diversity of microorganisms that are a precious source of molecules with high biotechnological potential. Biosurfactants from cold-adapted organisms can interact with multiple physical phases – water, ice, hydrophobic compounds, and gases – at low and freezing temperatures and be used in sustainable (green) and low-energy-impact (cold) products and processes. We review the biodiversity of microbial biosurfactants produced in cold habitats and provide a perspective on the most promising future applications in environmental and industrial technologies. Finally, we encourage exploring the cryosphere for novel types of biosurfactants via both culture screening and functional metagenomics. ‘Cold’ is becoming ‘cool’ in microbiology. The cryosphere is becoming more easily accessible to scientific expeditions and is predicted to fuel the discovery of novel natural products. Research on biosurfactants from psychrophilic microorganisms is just beginning but is expected to contribute to the development of sustainable (green) and energy-saving (cold) biotechnologies. New formulations of washing products containing biosurfactants are being developed, which can enable effective detergency at lower temperatures and will help laundry practices to reduce the environmental impact. Advances in unconventional experimental approaches such as functional metagenomics hold great promise for future discovery of entirely new biosurfactant types and producing organisms from cold and extreme environments.

Biosurfactants offer good advantages over synthetic counterparts, including biodegradability, environmentally friendly and low toxicity. This study employed a yeast Meyerozyma guilliermondii MX strain for bioconversion of lignocellulosic xylose and palm oil to valuable glycolipid biosurfactant with desirable properties. The objective was to elucidate metabolic pathways related to production of glycolipids and its functional properties. To enhance de novo glycolipid production, manipulation of responsible enzymatic genes was conducted using media and environmental means in comparison to the industrial glycolipid producer, Candida bombicola . Proteomic profiles of yeast cells grown with or without palm oil uncovered novel key metabolic enzymes, namely fatty acid biosynthetic enzymes, leading to formation of glycolipid precursors. qRT-PCR identified some cluster genes responsible for biosynthesis of desirable glycolipids. Finally, LC-MS-based lipidomics of glycolipid fraction identified 15-(2′- O -β- d -glucopyranosyl-β- d -glucopyranosyloxy)hexadecanoic acid 1′,4″-lactone 6′,6″-diacetate (663.4525 m/z) as a major product. Using co-carbon substrates in the presence of salt and zinc, maximum glycolipid yield was achieved (55.72 g/L) with 55.30% emulsification activity and 10 mg/L of CMCs. Mixed glycolipids demonstrated antibiofilm activity against Candida albicans shown by reduction of metabolic activity. The novel biosurfactant-producing yeast M. guilliermondii MX is a promising cell factory of new antibiofilm glycolipids with potential for industrial-scale up.

Tuberculosis (TB), a leading cause of death among infectious diseases globally, is caused by Mycobacterium tuberculosis (Mtb). The pathogenicity of Mtb is largely attributed to its complex cell envelope, which includes a class of glycolipids called phosphatidyl- myo -inositol mannosides (PIMs). These glycolipids maintain the integrity of the cell envelope, regulate permeability, and mediate host-pathogen interactions. PIMs comprise a phosphatidyl- myo -inositol core decorated with one to six mannose residues and up to four acyl chains. The mannosyltransferase PimE catalyzes the transfer of the fifth PIM mannose residue from a polyprenyl phosphate-mannose (PPM) donor. This step contributes to the proper assembly and function of the mycobacterial cell envelope; however, the structural basis for substrate recognition and the catalytic mechanism of PimE remain poorly understood. Here, we present the cryo-electron microscopy (cryo-EM) structures of PimE from Mycobacterium abscessus in its apo and product-bound form. The structures reveal a distinctive binding cavity that accommodates both donor and acceptor substrates/products. Key residues involved in substrate coordination and catalysis were identified and validated via in vitro assays and in vivo complementation, while molecular dynamics simulations delineated access pathways and binding dynamics. Our integrated approach provides comprehensive insights into PimE function and informs potential strategies for anti-TB therapeutics. Here the authors investigate of the structural basis of substrate recognition and the catalytic mechanism of the mannosyltransferase PimE, which is crucial for the biosynthesis of phosphatidyl-myo-inositol mannosides (PIMs) in Mycobacterium tuberculosis .

Cellobiose lipids (CBLs) are glycolipid biosurfactants that are widely applicable across diverse industries.CBLs have remarkable gelling, surface-active, and antifungal properties, making them ideal compounds for developing novel biotechnologies (e.g., biomaterials, detergents, and emulsifiers) with commercial potential.Various production methodologies have been developed via an interplay between producing organisms, media, and production approaches, each with its unique advantages and limitations toward scalability.Significant exploration is still required regarding downstream processing of CBLs because an optimised and scalable downstream technique is needed to complete the biotechnological cycle of CBL production.Finally, the industrialisation of CBL production requires the implementation of techno-economic and life-cycle assessments, which are currently understudied. Cellobiose lipids (CBLs) are glycolipid biosurfactants that have garnered attention due to their potential applications in diverse industries. Here, we review the current state of CBL research, from production and purification, to the potential applications of CBLs. We elucidate CBL functionality and consider some commercial applications, as well as how operating conditions (e.g., media and organism, or production approaches) impact productivity. Methodologies based on enzymatic synthesis or postproduction chemical modification of CBL variants are also presented. Given the importance of purity in current CBL applications, we discuss CBL separation and purification techniques. Finally, we highlight the importance of techno-economic and life-cycle assessments for the industrialisation of CBLs, while suggesting potential future routes for investigation. Cellobiose lipids (CBLs) are glycolipid biosurfactants that have garnered attention due to their potential applications in diverse industries. Here, we review the current state of CBL research, from production and purification, to the potential applications of CBLs. We elucidate CBL functionality and consider some commercial applications, as well as how operating conditions (e.g., media and organism, or production approaches) impact productivity. Methodologies based on enzymatic synthesis or postproduction chemical modification of CBL variants are also presented. Given the importance of purity in current CBL applications, we discuss CBL separation and purification techniques. Finally, we highlight the importance of techno-economic and life-cycle assessments for the industrialisation of CBLs, while suggesting potential future routes for investigation.

Acylsugars are defensive glycolipids in Solanaceae glandular trichomes, and their biosynthesis offers an exemplary system for understanding the evolutionary mechanisms of plant chemical defense, yet their transcriptional regulation is poorly understood. Here, we identified and characterized WRINKLED3 (WRI3), which is critical for acylsugar biosynthesis in tomato. SlWRI3 is specifically expressed in trichome tip cells, and its knockout reduces acylsugar accumulation. Using transcriptomics, DNA-protein interaction assays, and metabolomics, we demonstrate that SlWRI3 acts via a dual regulatory mechanism: directly activating the acyltransferase gene SlASAT1 for the initial acylation of sucrose core and upregulating multiple acetyl-CoA carboxylase (ACCase) subunits to provide acyl chain precursors. Silencing these ACCase genes similarly decreased acylsugar levels. Phylogenetic analysis indicates that the function of WRI3 in acylsugar biosynthesis is evolutionarily conserved in Solanaceae. These findings elucidate how a primary metabolism-associated regulator was repurposed to coordinate precursor supply and specialized metabolite production, deepening our understanding of plant metabolic evolution, providing a target for engineering pest-resistance in Solanaceae crops. The transcription factor SlWRI3 integrates fatty acid metabolism with acylsugar biosynthesis in tomato trichomes, coordinating precursor supply and assembly of these natural insect defensive chemicals.

This study aimed to identify and characterise biosurfactant compounds produced by bacteria associated with a marine eukaryotic phytoplankton bloom. One strain, designated MCTG214(3b1), was isolated by enrichment with polycyclic aromatic hydrocarbons and based on 16S rDNA, and gyrB sequencing was found to belong to the genus Pseudomonas, however not related to P. aeruginosa. Cell-free supernatant samples of strain MCTG214(3b1) at stationary phase showed significant reductions in surface tension. HPLC-MS and NMR analysis of these samples indicated the presence of five different rhamnolipid (RL) congeners. Di-rhamnolipids accounted for 87% relative abundance and all congeners possessed fatty acid moieties consisting of 8–12 carbons. PCR screening of strain MCTG214(3b1) DNA revealed homologues to the P. aeruginosa RL synthesis genes rhlA and rhlB; however, no rhlC homologue was identified. Using the Galleria mellonella larvae model, strain MCTG214(3b1) was demonstrated to be far less pathogenic than P. aeruginosa. This study identifies for the first time a significantly high level of synthesis of short chain di-rhamnolipids by a non-pathogenic marine Pseudomonas species. We postulate that RL synthesis in Pseudomonas sp. MCTG214(3b1) is carried out by enzymes expressed from rhlA/B homologues similar to those of P. aeruginosa; however, a lack of rhlC potentially indicates the presence of a second novel rhamnosyltransferase responsible for the di-rhamnolipid congeners identified by HPLC-MS.

Sophorolipids are surface-active compounds synthesized by a selected number of yeast species. They have been known for over 40 years, but because of growing environmental awareness, they recently regained attention as biosurfactants due to their biodegradability, low ecotoxicity, and production based on renewable resources. In this paper, an overview is given of the producing yeast strains and various aspects of fermentative sophorolipid production. Also, the biochemical pathways and regulatory mechanisms involved in sophorolipid biosynthesis are outlined. To conclude, a summary is given on possible applications of sophorolipids, either as native or modified molecules.