Antiadhesive activity of the biosurfactant pseudofactin II secreted by the Arctic bacterium Pseudomonas fluorescens BD5

Sophorolipid: An Effective Biomolecule for Targeting Microbial Biofilms

Biofilms are microbial aggregates encased in a matrix that is attached to biological or nonbiological surfaces and constitute serious problems in food, medical, and marine industries and can have major negative effects on both health and the economy. Biofilm's complex microbial community provides a resistant environment that is difficult to eradicate and is extremely resilient to antibiotics and sanitizers. There are various conventional techniques for combating biofilms, including, chemical removal, physical or mechanical removal, use of antibiotics and disinfectants to destroy biofilm producing organisms. In contrast to free living planktonic cells, biofilms are very resistant to these methods. Hence, new strategies that differ from traditional approaches are urgently required. Microbial world offers a wide range of effective "green" compounds such as biosurfactants. They outperform synthetic surfactants in terms of biodegradability, superior stabilization, and reduced toxicity concerns. They also have better antiadhesive and anti-biofilm capabilities which can be used to treat biofilm-related problems. Sophorolipids (SLs) are a major type of biosurfactants that have gained immense interest in the healthcare industries because of their antiadhesive and anti-biofilm properties. Sophorolipids may therefore prove to be attractive substances that can be used in biomedical applications as adjuvant to other antibiotics against some infections through growth inhibition and/or biofilm disruption.

Anti-Biofilm Activity of Assamsaponin A, Theasaponin E1, and Theasaponin E2 against Candida albicans

Biofilm formation plays a crucial role in the pathogenesis of Candida albicans and is significantly associated with resistance to antifungal agents. Tea seed saponins, a class of non-ionic triterpenes, have been proven to have fungicidal effects on planktonic C. albicans. However, their anti-biofilm activity and mechanism of action against C. albicans remain unclear. In this study, the effects of three Camellia sinensis seed saponin monomers, namely, theasaponin E1 (TE1), theasaponin E2 (TE2), and assamsaponin A (ASA), on the metabolism, biofilm development, and expression of the virulence genes of C. albicans were evaluated. The results of the XTT reduction assay and crystal violet (CV) staining assay demonstrated that tea seed saponin monomers concentration-dependently suppressed the adhesion and biofilm formation of C. albicans and were able to eradicate mature biofilms. The compounds were in the following order in terms of their inhibitory effects: ASA > TE1 > TE2. The mechanisms were associated with reductions in multiple crucial virulence factors, including cell surface hydrophobicity (CSH), adhesion ability, hyphal morphology conversion, and phospholipase activity. It was further demonstrated through qRT-PCR analysis that the anti-biofilm activity of ASA and TE1 against C. albicans was attributed to the inhibition of RAS1 activation, which consequently suppressed the cAMP-PKA and MAPK signaling pathways. Conversely, TE2 appeared to regulate the morphological turnover and hyphal growth of C. albicans via a pathway that was independent of RAS1. These findings suggest that tea seed saponin monomers are promising innovative agents against C. albicans.

Microbial lipopeptides: their pharmaceutical and biotechnological potential, applications, and way forward

As lead molecules, cyclic lipopeptides with antibacterial, antifungal, and antiviral properties have garnered a lot of attention in recent years. Because of their potential, cyclic lipopeptides have earned recognition as a significant class of antimicrobial compounds with applications in pharmacology and biotechnology. These lipopeptides, often with biosurfactant properties, are amphiphilic, consisting of a hydrophilic moiety, like a carboxyl group, peptide backbone, or carbohydrates, and a hydrophobic moiety, mostly a fatty acid. Besides, several lipopeptides also have cationic groups that play an important role in biological activities. Antimicrobial lipopeptides can be considered as possible substitutes for antibiotics that are conventional to address the current drug-resistant issues as pharmaceutical industries modify the parent antibiotic molecules to render them more effective against antibiotic-resistant bacteria and fungi, leading to the development of more resistant microbial strains. Bacillus species produce lipopeptides, which are secondary metabolites that are amphiphilic and are typically synthesized by non-ribosomal peptide synthetases (NRPSs). They have been identified as potential biocontrol agents as they exhibit a broad spectrum of antimicrobial activity. A further benefit of lipopeptides is that they can be produced and purified biotechnologically or biochemically in a sustainable manner using readily available, affordable, renewable sources without harming the environment. In this review, we discuss the biochemical and functional characterization of antifungal lipopeptides, as well as their various modes of action, method of production and purification (in brief), and potential applications as novel antibiotic agents.

An insight into the utilization of microbial biosurfactants pertaining to their industrial applications in the food sector

Microbial biosurfactants surpass synthetic alternatives due to their biodegradability, minimal toxicity, selective properties, and efficacy across a wide range of environmental conditions. Owing to their remarkable advantages, biosurfactants employability as effective emulsifiers and stabilizers, antimicrobial and antioxidant attributes, rendering them for integration into food preservation, processing, formulations, and packaging. The biosurfactants can also be derived from various types of food wastes. Biosurfactants are harnessed across multiple sectors within the food industry, ranging from condiments (mayonnaise) to baked goods (bread, muffins, loaves, cookies, and dough), and extending into the dairy industry (cheese, yogurt, and fermented milk). Additionally, their impact reaches the beverage industry, poultry feed, seafood products like tuna, as well as meat processing and instant foods, collectively redefining each sector's landscape. This review thoroughly explores the multifaceted utilization of biosurfactants within the food industry as emulsifiers, antimicrobial, antiadhesive, antibiofilm agents, shelf-life enhancers, texture modifiers, and foaming agents.

Unraveling the mechanistic insights of sophorolipid-capped gold nanoparticle-induced cell death in Vibrio cholerae

IMPORTANCE

Vibrio cholerae, a Gram-negative bacterium, is the causative agent of a fatal disease, "cholera." Prevention of cholera outbreak is possible by eliminating the bacteria from the environment. However, antimicrobial resistance developed in microorganisms has posed a threat and challenges to its treatment. Application of nanoparticles is a useful and effective option for the elimination of such microorganisms. Metal-based nanopaticles exhibit microbial toxicity through non-specific mechanisms. To prevent resistance development and increase antibacterial efficiency, rational designing of nanoparticles is required. Thus, knowledge on the exact mechanism of action of nanoparticles is highly essential. In this study, we explore the possible mechanisms of antibacterial activity of AuNPs-SL against V. cholerae. We show that the interaction of AuNPs-SL with V. cholerae enhances ROS production and membrane depolarization, change in permeability, and leakage of intracellular content. This action leads to the depletion of cellular ATP level, DNA damage, and subsequent cell death.

Do biosurfactants as anti-biofilm agents have a future in industrial water systems?

Biofilms are bacterial communities embedded in exopolymeric substances that form on the surfaces of both man-made and natural structures. Biofilm formation in industrial water systems such as cooling towers results in biofouling and biocorrosion and poses a major health concern as well as an economic burden. Traditionally, biofilms in industrial water systems are treated with alternating doses of oxidizing and non-oxidizing biocides, but as resistance increases, higher biocide concentrations are needed. Using chemically synthesized surfactants in combination with biocides is also not a new idea; however, these surfactants are often not biodegradable and lead to accumulation in natural water reservoirs. Biosurfactants have become an essential bioeconomy product for diverse applications; however, reports of their use in combating biofilm-related problems in water management systems is limited to only a few studies. Biosurfactants are powerful anti-biofilm agents and can act as biocides as well as biodispersants. In laboratory settings, the efficacy of biosurfactants as anti-biofilm agents can range between 26% and 99.8%. For example, long-chain rhamnolipids isolated from Burkholderia thailandensis inhibit biofilm formation between 50% and 90%, while a lipopeptide biosurfactant from Bacillus amyloliquefaciens was able to inhibit biofilms up to 96% and 99%. Additionally, biosurfactants can disperse preformed biofilms up to 95.9%. The efficacy of antibiotics can also be increased by between 25% and 50% when combined with biosurfactants, as seen for the V9T14 biosurfactant co-formulated with ampicillin, cefazolin, and tobramycin. In this review, we discuss how biofilms are formed and if biosurfactants, as anti-biofilm agents, have a future in industrial water systems. We then summarize the reported mode of action for biosurfactant molecules and their functionality as biofilm dispersal agents. Finally, we highlight the application of biosurfactants in industrial water systems as anti-fouling and anti-corrosion agents.

Production and characterization of lipopeptide biosurfactant from a new strain of Pseudomonas antarctica 28E using crude glycerol as a carbon source

Pseudomonas is a cosmopolitan genus of bacteria found in soil, water, organic matter, plants and animals and known for the production of glycolipid and lipopeptide biosurfactants. In this study bacteria (laboratory collection number 28E) isolated from soil collected in Spitsbergen were used for biosurfactant production. 16S rRNA sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) revealed that this isolate belongs to the species Pseudomonas antarctica. In the present study, crude glycerol, a raw material obtained from several industrial processes, was evaluated as a potential low-cost carbon source to reduce the costs of lipopeptide production. Among several tested glycerols, a waste product of stearin production, rich in nitrogen, iron and calcium, ensured optimal conditions for bacterial growth. Biosurfactant production was evidenced by a reduction of surface tension (ST) and an increase in the emulsification index (E24%). According to Fourier-transform infrared spectroscopy (FTIR) and electrospray ionization mass spectrometry (ESI-MS), the biosurfactant was identified as viscosin. The critical micelle concentration (CMC) of lipopeptide was determined to be 20 mg L-1. Interestingly, viscosin production has been reported previously for Pseudomonas viscosa, Pseudomonas fluorescens and Pseudomonas libanensis. To the best of our knowledge, this is the first report on viscosin production by a P. antarctica 28E. The results indicated the potential of crude glycerol as a low-cost substrate to produce a lipopeptide biosurfactant with promising tensioactive and emulsifying properties.

Microbial Lipopeptides: Properties, Mechanics and Engineering for Novel Lipopeptides

Microorganisms produce active surface agents called lipopeptides (LPs) which are amphiphilic in nature. They are cyclic or linear compounds and are predominantly isolated from Bacillus and Pseudomonas species. LPs show antimicrobial activity towards various plant pathogens and act by inhibiting the growth of these organisms. Several mechanisms are exhibited by LPs, such as cell membrane disruption, biofilm production, induced systematic resistance, improving plant growth, inhibition of spores, etc., making them suitable as biocontrol agents and highly advantageous for industrial utilization. The biosynthesis of lipopeptides involves large multimodular enzymes referred to as non-ribosomal peptide synthases. These enzymes unveil a broad range of engineering approaches through which lipopeptides can be overproduced and new LPs can be generated asserting high efficacy. Such approaches involve several synthetic biology systems and metabolic engineering techniques such as promotor engineering, enhanced precursor availability, condensation domain engineering, and adenylation domain engineering. Finally, this review provides an update of the applications of lipopeptides in various fields.

Rhamnolipid-Coated Iron Oxide Nanoparticles as a Novel Multitarget Candidate against Major Foodborne E. coli Serotypes and Methicillin-Resistant S. aureus

Surface-growing antibiotic-resistant pathogenic bacteria such as Escherichia coli and Staphylococcus aureus are emerging as a global health challenge due to dilemmas in clinical treatment. Furthermore, their pathogenesis, including increasingly serious antimicrobial resistance and biofilm formation, makes them challenging to treat by conventional therapy. Therefore, the development of novel antivirulence strategies will undoubtedly provide a path forward in combatting these resistant bacterial infections. In this regard, we developed novel biosurfactant-coated nanoparticles to combine the antiadhesive/antibiofilm properties of rhamnolipid (RHL)-coated Fe3O4 nanoparticles (NPs) with each of the p-coumaric acid (p-CoA) and gallic acid (GA) antimicrobial drugs by using the most available polymer common coatings (PVA) to expand the range of effective antibacterial drugs, as well as a mechanism for their synergistic effect via a simple method of preparation. Mechanistically, the average size of bare Fe3O4 NPs was ~15 nm, while RHL-coated Fe3O4@PVA@p-CoA/GA was about ~254 nm, with a drop in zeta potential from -18.7 mV to -34.3 mV, which helped increase stability. Our data show that RHL-Fe3O4@PVA@p-CoA/GA biosurfactant NPs can remarkably interfere with bacterial growth and significantly inhibited biofilm formation to more than 50% via downregulating IcaABCD and CsgBAC operons, which are responsible for slime layer formation and curli fimbriae production in S. aureus and E. coli, respectively. The novelty regarding the activity of RHL-Fe3O4@PVA@p-CoA/GA biosurfactant NPs reveals their potential effect as an alternative multitarget antivirulence candidate to minimize infection severity by inhibiting biofilm development. Therefore, they could be used in antibacterial coatings and wound dressings in the future. IMPORTANCE Antimicrobial resistance poses a great threat and challenge to humanity. Therefore, the search for alternative ways to target and eliminate microbes from plant, animal, and marine microorganisms is one of the world's concerns today. Furthermore, the extraordinary capacity of S. aureus and E. coli to resist standard antibacterial drugs is the dilemma of all currently used remedies. Methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) have become widespread, leading to no remedies being able to treat these threatening pathogens. The most widely recognized serotypes that cause severe foodborne illness are E. coli O157:H7, O26:H11, and O78:H10, and they display increasing antimicrobial resistance rates. Therefore, there is an urgent need for an effective therapy that has dual action to inhibit biofilm formation and decrease bacterial growth. In this study, the synthesized RHL-Fe3O4@PVA@p-CoA/GA biosurfactant NPs have interesting properties, making them excellent candidates for targeted drug delivery by inhibiting bacterial growth and downregulating biofilm-associated IcaABCD and CsgBAC gene loci.

The First Comprehensive Biodiversity Study of Culturable Fungal Communities Inhabiting Cryoconite Holes in the Werenskiold Glacier on Spitsbergen (Svalbard Archipelago, Arctic)

Cryoconite holes on glacier surfaces are a source of cold-adapted microorganisms, but little is known about their fungal inhabitants. Here, we provide the first report of distinctive fungal communities in cryoconite holes in the Werenskiold Glacier on Spitsbergen (Svalbard Archipelago, Arctic). Due to a combination of two incubation temperatures (7 °C and 24 ± 0.5 °C) and two media during isolation (PDA, YPG), as well as classical and molecular identification approaches, we were able to identify 23 different fungi (21 species and 2 unassigned species). Most of the fungi cultured from cryoconite sediment were ascomycetous filamentous micromycetes. However, four representatives of macromycetes were also identified (Bjerkandera adusta, Holwaya mucida, Orbiliaceae sp., and Trametes versicolor). Some of the described fungi possess biotechnological potential (Aspergillus pseudoglaucus, A. sydowii, Penicillium expansum, P. velutinum, B. adusta, and T. versicolor), thus, we propose the Arctic region as a source of new strains for industrial applications. In addition, two phytopathogenic representatives were present (P. sumatraense, Botrytis cinerea), as well as one potentially harmful to humans (Cladosporium cladosporioides). To the best of our knowledge, we are the first to report the occurrence of A. pseudoglaucus, C. allicinum, C. ramotenellum, P. sumatraense, P. velutinum, P. cumulodentata, B. adusta, and T. versicolor in polar regions. In all likelihood, two unassigned fungus species (Orbiliaceae and Dothideomycetes spp.) might also be newly described in such environments. Additionally, due to experimenting with 10 sampling sites located at different latitudes, we were able to conclude that the number of fungal spores decreases as one moves down the glacier. Considering the prevalence and endangerment of glacial environments worldwide, such findings suggest their potential as reservoirs of fungal diversity, which should not be overlooked.

Application of Levan-Rich Digestate Extract in the Production of Safe-to-Use and Functional Natural Body Wash Cosmetics

The study focused on the evaluation of the possibility of using a levan-rich digestate extract in the production of safe and functional body wash cosmetics. Model shower gels were designed and formulated on the basis of raw materials of natural origin. Prepared prototypes contained various extract concentrations (16.7; 33; 50%). A gel without extract was used as a reference. The samples were evaluated for their safety in use and functionality. The results showed that the use of high-concentration levan-rich digestate extract in a shower gel resulted in a significant reduction in the negative impact on the skin. For example, the zein value decreased by over 50% in relation to the preparation without the extract. An over 40% reduction in the emulsifying capacity of hydrophobic substances was also demonstrated, which reduces skin dryness after the washing process. However, the presence of the extract did not significantly affect the parameters related to functionality. Overall, it was indicated that levan-rich digestate extract can be successfully used as a valuable ingredient in natural cleansing cosmetics.

Bacillus amyloliquefaciens-Derived Lipopeptide Biosurfactants Inhibit Biofilm Formation and Expression of Biofilm-Related Genes of Staphylococcus aureus

Biosurfactants (BSs) are surface-active compounds produced by diverse microorganisms, including the genus Bacillus. These bioactive compounds possess biological activities such as antiadhesive, antimicrobial and antibiofilm effects that can lead to important applications in combating many infections. Based on these findings, we decided to investigate the antibiofilm activity of BSs from the marine Bacillus amyloliquefaciens against Staphylococcus aureus CCM 4223. Expression of biofilm-related genes was also evaluated using qRT-PCR. Isolated and partially purified BSs were identified and characterized by molecular tools and by UHPLC-DAD and MALDI-TOF/MS. Bacillus amyloliquefaciens 3/22, that exhibited surfactant activity evaluated by oil spreading assay, was characterized using the 16S rRNA sequencing method. Screening by PCR detected the presence of the sfp, srfAA, fenD and ituD genes, suggesting production of the lipopeptides (LPs) surfactin, fengycin and iturin. The above findings were further supported by the results of UHPLC-DAD and MALDI-TOF/MS. As quantified by the crystal violet method, the LPs significantly (p < 0.001) reduced biofilm formation of S. aureus in a dose-dependent manner and decreased expression of biofilm-related genes fnbA, fnbB, sortaseA and icaADBC operon. Data from our investigation indicate a promising therapeutic application for LPs isolated from B. amyloliquefaciens toward prevention of S. aureus biofilm infections.

Microbial Biosurfactant: A New Frontier for Sustainable Agriculture and Pharmaceutical Industries

In the current scenario of changing climatic conditions and the rising global population, there is an urgent need to explore novel, efficient, and economical natural products for the benefit of humankind. Biosurfactants are one of the latest explored microbial synthesized biomolecules that have been used in numerous fields, including agriculture, pharmaceuticals, cosmetics, food processing, and environment-cleaning industries, as a source of raw materials, for the lubrication, wetting, foaming, emulsions formulations, and as stabilizing dispersions. The amphiphilic nature of biosurfactants have shown to be a great advantage, distributing themselves into two immiscible surfaces by reducing the interfacial surface tension and increasing the solubility of hydrophobic compounds. Furthermore, their eco-friendly nature, low or even no toxic nature, durability at higher temperatures, and ability to withstand a wide range of pH fluctuations make microbial surfactants preferable compared to their chemical counterparts. Additionally, biosurfactants can obviate the oxidation flow by eliciting antioxidant properties, antimicrobial and anticancer activities, and drug delivery systems, further broadening their applicability in the food and pharmaceutical industries. Nowadays, biosurfactants have been broadly utilized to improve the soil quality by improving the concentration of trace elements and have either been mixed with pesticides or applied singly on the plant surfaces for plant disease management. In the present review, we summarize the latest research on microbial synthesized biosurfactant compounds, the limiting factors of biosurfactant production, their application in improving soil quality and plant disease management, and their use as antioxidant or antimicrobial compounds in the pharmaceutical industries.

Effect of Lipopeptide-Loaded Chitosan Nanoparticles on Candida albicans Adhesion and on the Growth of Leishmania major

Cyclic lipopeptides produced by Bacillus species exhibit interesting therapeutic potential. However, their clinical use remains limited due to their low stability, undesirable interactions with host macromolecules, and their potential toxicity to mammalian cells. The present work aims to develop suitable lipopeptide-loaded chitosan nanoparticles with improved biological properties and reduced toxicity. Surfactin and bacillomycin D lipopeptides produced by Bacillus amyloliquefaciens B84 strain were loaded onto chitosan nanoparticles by ionotropic gelation process. Nanoformulated lipopeptides exhibit an average size of 569 nm, a zeta potential range of 38.8 mV, and encapsulation efficiency (EE) of 85.58%. Treatment of Candida (C.) albicans cells with encapsulated lipopeptides induced anti-adhesive activity of 81.17% and decreased cell surface hydrophobicity (CSH) by 25.53% at 2000 µg/mL. Nanoformulated lipopeptides also induced antileishmanial activity against Leishmania (L.) major promastigote and amastigote forms at respective IC₅₀ values of 14.37 µg/mL and 22.45 µg/mL. Nanoencapsulated lipopeptides exerted low cytotoxicity towards human erythrocytes and Raw 264.7 macrophage cell line with respective HC₅₀ and LC₅₀ values of 770 µg/mL and 234.56 µg/mL. Nanoencapsulated lipopeptides could be used as a potential delivery system of lipopeptides to improve their anti-adhesive effect against C. albicans cells colonizing medical devices and their anti-infectious activity against leishmania.

Candida albicans Biofilm Inhibition by Two Vaccinium macrocarpon (Cranberry) Urinary Metabolites: 5-(3',4'-DihydroxyPhenyl)-γ-Valerolactone and 4-Hydroxybenzoic Acid

Candida spp. are pathobionts, as they can switch from commensals to pathogens, responsible for a variety of pathological processes. Adhesion to surfaces, morphological switch and biofilm-forming ability are the recognized virulence factors promoting yeast virulence. Sessile lifestyle also favors fungal persistence and antifungal tolerance. In this study, we investigated, in vitro, the efficacy of two urinary cranberry metabolites, 5-(3′,4′-dihydroxy phenyl)-γ-valerolactone (VAL) and 4-hydroxybenzoic acid (4-HBA), in inhibiting C. albicans adhesion and biofilm formation. Both the reference strain SC5314 and clinical isolates were used. We evaluated biomass reduction, by confocal microscopy and crystal violet assay, and the possible mechanisms mediating their inhibitory effects. Both VAL and 4-HBA were able to interfere with the yeast adhesion, by modulating the expression of key genes, HWP1 and ALS3. A significant dose-dependent reduction in biofilm biomass and metabolic activity was also recorded. Our data showed that the two cranberry metabolites VAL and 4-HBA could pave the way for drug development, for targeting the very early phases of biofilm formation and for preventing genitourinary Candida infections.

Surfactants of microbial origin as antibiofilm agents

The microbial world provides new energy sources and many various 'green' chemicals. One type of chemicals produced by microorganisms is the biosurfactant group. Biosurfactants are universal molecules, exhibiting surface properties often accompanied by desired biological activity. Biosurfactants are considered to be environmentally 'friendly' due to their low toxicity and biodegradable nature. These compounds have unique features and therefore they can find potential applications in many different industries, ranging from biotechnology to environmental remediation technologies. Antibacterial and antifungal activities make them relevant for applications as inhibitory agents against microbial biofilm. This review covers the current knowledge and the recent advances in the field of biosurfactants as antibiofilm agents.

Bibliometric Analysis of Hydrocarbon Bioremediation in Cold Regions and a Review on Enhanced Soil Bioremediation

Simple Summary

Anthropogenic activities in cold regions require petroleum oils to support various purposes. With the increased demand of petroleum, accidental oil spills are generated during transportation or refuelling processes. Soil is one of the major victims in petroleum pollution, hence studies have been devoted to find solutions to remove these petroleum hydrocarbons. However, the remote and low-temperature conditions in cold regions hindered the implementation of physical and chemical removal treatments. On the other hand, biological treatments in general have been proposed as an innovative approach to attenuate these hydrocarbon pollutants in soils. To understand the relevancy of biological treatments for cold regions specifically, bibliometric analysis has been applied to systematically analyse studies focused on hydrocarbon removal treatment in a biological way. To expedite the understanding of this analysis, we have summarised these biological treatments and suggested other biological applications in the context of cold conditions.

Abstract

The increased usage of petroleum oils in cold regions has led to widespread oil pollutants in soils. The harsh environmental conditions in cold environments allow the persistence of these oil pollutants in soils for more than 20 years, raising adverse threats to the ecosystem. Microbial bioremediation was proposed and employed as a cost-effective tool to remediate petroleum hydrocarbons present in soils without significantly posing harmful side effects. However, the conventional hydrocarbon bioremediation requires a longer time to achieve the clean-up standard due to various environmental factors in cold regions. Recent biotechnological improvements using biostimulation and/or bioaugmentation strategies are reported and implemented to enhance the hydrocarbon removal efficiency under cold conditions. Thus, this review focuses on the enhanced bioremediation for hydrocarbon-polluted soils in cold regions, highlighting in situ and ex situ approaches and few potential enhancements via the exploitation of molecular and microbial technology in response to the cold condition. The bibliometric analysis of the hydrocarbon bioremediation research in cold regions is also presented.

Lipopeptides production by a newly Halomonas venusta strain: Characterization and biotechnological properties

A halotolerant marine strain PHKT of Halomonas venusta was isolated from contaminated seawater as an efficient biosurfactant producer candidate, on low-value substrate (glycerol). The produced biosurfactants (Bios-PHKT) were characterized as lipopeptides molecules, belonging to surfactin and pumilacidin families, by using Thin Layer Chromatography (TLC), Fourier Transform Infrared Spectroscopy (FT-IR) and Tandem Mass Spectrometry (MALDI-TOF/MS-MS). Bios-PHKT has a critical micelle concentration (CMC) of 125 mg/L, and showed a high steadiness against a wide spectrum of salinity (0-120 g/L NaCl), temperature (4-121 °C) and pH (2-12), supporting its powerful tensioactive properties under various environmental conditions. Likewise, the cytotoxic test revealed that the biosurfactant Bios-PHKT, at concentrations lower than 125 µg/mL, was not cytotoxic for human HEK-293 cells since the cell survival is over than 80%. Furthermore, Bios-PHKT lipopeptides showed excellent anti-adhesive and anti-biofilm activities, being able to avoid and disrupt the biofilm formation by certain pathogenic microorganisms. In addition, the biosurfactant Bios-PHKT showed a remarkable anti-proliferative activity towards tumor B16 melanoma cell line. Besides, Bios-PHKT exhibited an excellent in vitro and in vivo wound healing process. In light of these promising findings, Bios-PHKT could be successfully used in different biotechnological applications.

Impact of Bacillus licheniformis SV1 Derived Glycolipid on Candida glabrata Biofilm

In the present investigation, we have evaluated the antibiofilm potential of Bacillus licheniformis SV1 derived glycolipid against C. glabrata biofilm. Impact of isolated glycolipid on the viability of C. glabrata and on inhibiting as well as eradicating ability of its biofilm were studied. Further, morphological alterations, reactive oxygen species generation (ROS) production and transcriptional expression of selected genes (RT-PCR) of C. glabrata in response with isolated glycolipid were studied. The isolated glycolipid (1.0 mg ml^-1) inhibited and eradicated C. glabrata biofilm approximately 80% and 60%, respectively. FE-SEM images revealed glycolipid exposure results in architectural alteration and eradication of C. glabrata biofilm and ROS generation. Transcriptional studies of selected genes showed that the expression of AUS1, FKS1 and KRE1 were down-regulated, while that of ergosterol biosynthesis pathway and multidrug transporter increased, in the presence of glycolipid.

Nanotechnology-Based Antimicrobial and Antiviral Surface Coating Strategies

Biocontamination of medical devices and implants is a growing issue that causes medical complications and increased expenses. In the fight against biocontamination, developing synthetic surfaces, which reduce the adhesion of microbes and provide biocidal activity or combinatory effects, has emerged as a major global strategy. Advances in nanotechnology and biological sciences have made it possible to design smart surfaces for decreasing infections. Nevertheless, the clinical performance of these surfaces is highly depending on the choice of material. This review focuses on the antimicrobial surfaces with functional material coatings, such as cationic polymers, metal coatings and antifouling micro-/nanostructures. One of the highlights of the review is providing insights into the virus-inactivating surface development, which might particularly be useful for controlling the currently confronted pandemic coronavirus disease 2019 (COVID-19). The nanotechnology-based strategies presented here might be beneficial to produce materials that reduce or prevent the transmission of airborne viral droplets, once applied to biomedical devices and protective equipment of medical workers. Overall, this review compiles existing studies in this broad field by focusing on the recent related developments, draws attention to the possible activity mechanisms, discusses the key challenges and provides future recommendations for developing new, efficient antimicrobial and antiviral surface coatings.

Antiadhesive, antibiofilm and dispersion activity of biosurfactants isolated from Bacillus amyloliquefaciens 3/22

The aim of this work was to monitor the potential antibiofilm properties of biosurfactants (BS) isolated from Bacillus amyloliquefaciens 3/22 against biofilm formation of the indicator strain Staphylococcus aureus CCM 4223. In this work, the effect of BS 3/22 on biofilm growth during co-incubation, inhibition of biofilm-forming cell adhesion and biofilm dispersion was studied. BS 3/22 inhibited biofilm formation, with its formation decreasing significantly (p &lt; 0.05; p &lt; 0.01; p &lt; 0.001) with increasing BS 3/22 concentration. BS 3/22 also showed antiadhesive activity, which correlated with the concentration used. The dispersing effect of isolated BS 3/22 on a 24-hour biofilm was also detected. BS 3/22 were effective in biofilm dispersion even at lower concentrations compared to antiadhesive activity and inhibition of biofilm formation.

Specific nature of medicines and value of medicines

Medicines are not ordinary consumer or industrial goods but goods of a specific nature. The article provides an overview of the fundamental characteristics that distinguish medicines from common consumer goods. Another essential attribute of the term medicine is its values (clinical, economic, human), which form a crucial concept of the medicine category.

The use of low-cost brewery waste product for the production of surfactin as a natural microbial biocide

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For the first time Bacillus subtilis was able to grow in a culture medium containing Brewery waste (Trub) and produced surfactin.

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Surfactin showed bactericidal effect against Pseudomonas aeruginosa.

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P. aeruginosa biofilm was inhibited (79.8%) when co-incubated with surfactin.

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Surfactin showed anti-adhesive activity on polystyrene surfaces.

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P. aeruginosa biofilm was disrupted (44.9%) when treated with surfactin (700 μg/mL).

Surfactin has potential as next generation antibiofilm agent to combat antimicrobial resistance against emerging pathogens. However, the widespread industrial applications of surfactin is hampered by its high production cost. In this work, surfactin was produced from Bacillus subtilis using a low-cost brewery waste as a carbon source. The strain produced 210.11 mg L−1 after 28 h. The antimicrobial activity was observed against all tested strains, achieving complete inhibition for Pseudomonas aeruginosa, at 500 μg mL−1. A growth log reduction of 3.91 was achieved for P. aeruginosa while, Staphylococcus aureus and Staphylococcus epidermidis showed between 1 and 2 log reductions. In the anti-biofilm assays against P. aeruginosa, the co-incubation, anti-adhesive and disruption showed inhibition, where the greatest inhibition was observed in the co-incubation assay (79.80%). This study provides evidence that surfactin produced from a low-cost substrate can be a promising biocide due to its antimicrobial and anti-biofilm abilities against pathogens.

Development of a Bioprocess for the Production of Cyclic Lipopeptides Pseudofactins With Efficient Purification From Collected Foam

Microbial surfactants (biosurfactants) have gained interest as promising substitutes of synthetic surface-active compounds. However, their production and purification are still challenging, with significant room for efficiency and costs optimization. In this work, we introduce a method for the enhanced production and purification of cyclic lipopeptides pseudofactins (PFs) from Pseudomonas fluorescens BD5 cultures. The method is directly applicable in a technical scale with the possibility of further upscaling. Comparing to the original protocol for production of PFs (cultures in mineral salt medium in shaken flasks followed by solvent-solvent extraction of PFs), our process offers not only ∼24-fold increased productivity, but also easier and more efficient purification. The new process combines high yield of PFs (∼7.2 grams of PFs per 30 L of working volume), with recovery levels of 80–90% and purity of raw PFs up to 60–70%. These were achieved with an innovative, single-step thermal co-precipitation and extraction of PFs directly from collected foam, as a large amount of PF-enriched foam was produced during the bioprocess. Besides we present a protocol for the selective production of PF structural analogs and their separation with high-performance liquid chromatography. Our approach can be potentially utilized in the efficient production and purification of other lipopeptides of Pseudomonas and Bacillus origin.

Effect of Disulfide Cyclization of Ultrashort Cationic Lipopeptides on Antimicrobial Activity and Cytotoxicity

Ultrashort cationic lipopeptides (USCLs) are considered to be a promising class of antimicrobials with high activity against a broad-spectrum of microorganisms. However, the majority of these compounds are characterized by significant toxicity toward human cells, which hinders their potential application. To overcome those limitations, several approaches have been advanced. One of these is disulfide cyclization that has been shown to improve drug-like characteristics of peptides. In this article the effect of disulfide cyclization of the polar head of N-palmitoylated USCLs on in vitro biological activity has been studied. Lipopeptides used in this study consisted of three or four basic amino acids (lysine and arginine) and cystine in a cyclic peptide. In general, disulfide cyclization of the lipopeptides resulted in peptides with reduced cytotoxicity. Disulfide-cyclized USCLs exhibited improved selectivity between Candida sp., Gram-positive strains and normal cells in contrast to their linear counterparts. Interactions between selected USCLs and membranes were studied by molecular dynamics simulations using a coarse-grained force field. Moreover, membrane permeabilization properties and kinetics were examined. Fluorescence and transmission electron microscopy revealed damage to Candida cell membrane and organelles. Concluding, USCLs are strong membrane disruptors and disulfide cyclization of polar head can have a beneficial effect on its in vitro selectivity between Candida sp. and normal human cells.

Diversity of Bacteria and Bacterial Products as Antibiofilm and Antiquorum Sensing Drugs Against Pathogenic Bacteria

The increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites. Similarly, non-pathogenic bacteria also take advantages of the QS signaling molecule as a sole carbon source for their growth through catabolism with enzymes. Several enzymes are produced by bacteria which disrupt the biofilm architecture by degrading the composition of extracellular polymeric substances (EPS) such as exopolysaccharide, extracellular- DNA and protein. Thus, the interference of QS system by bacterial metabolic products and enzymatic catalysis, modification of the QS signaling molecules as well as enzymatic disruption of biofilm architecture have been considered as the alternative therapeutic approaches. This review article elaborates on the diversity of different bacterial species with respect to their metabolic products as well as enzymes and their molecular modes of action. The bacterial enzymes and metabolic products will open new and promising perspectives for the development of strategies against the pathogenic bacterial infections.

Antibiofilm activity in the culture supernatant of a marine Pseudomonas sp. bacterium

In the marine environment, most solid surfaces are covered by microbial biofilms, mainly composed of bacteria and diatoms. The negative effects of biofilms on materials and equipment are numerous and pose a major problem for industry and human activities. Since marine micro-organisms are an important source of bioactive metabolites, it is possible that they synthesize natural ecofriendly molecules that inhibit the adhesion of organisms. In this work, the antibiofilm potential of marine bacteria was investigated using Flavobacterium sp. II2003 as a target. This strain is potentially a pioneer strain of bacteria that was previously selected from marine biofilms for its strong biofilm-forming ability. The culture supernatants of 86 marine heterotrophic bacteria were tested for their ability to inhibit Flavobacterium sp. II2003 biofilm formation and the Pseudomonas sp. IV2006 strain was identified as producing a strong antibiofilm activity. The Pseudomonas sp. IV2006 culture supernatant (SNIV2006) inhibited Flavobacterium sp. II2003 adhesion without killing the bacteria or inhibiting its growth. Moreover, SNIV2006 had no effect on the Flavobacterium sp. II2003 cell surface hydrophilic/hydrophobic and general Lewis acid–base characteristics, but modified the surface properties of glass, making it on the whole more hydrophilic and more alkaline and significantly reducing bacterial cell adhesion. The glass-coating molecules produced by Pseudomonas sp. IV2006 were found to probably be polysaccharides, whereas the antibiofilm molecules contained in SNIV2006 and acting during the 2 h adhesion step on glass and polystyrene surfaces would be proteinaceous. Finally, SNIV2006 exhibited a broad spectrum of antibiofilm activity on other marine bacteria such as Flavobacterium species that are pathogenic for fish, and human pathogens in both the medical environment, such as Staphylococcus aureus and Pseudomonas aeruginosa , and in the food industry, such as Yersinia enterocolitica . Thus, a wide range of applications could be envisaged for the SNIV2006 compounds, both in aquaculture and human health.

Lesson from Ecotoxicity: Revisiting the Microbial Lipopeptides for the Management of Emerging Diseases for Crop Protection

Microorganisms area treasure in terms of theproduction of various bioactive compounds which are being explored in different arenas of applied sciences. In agriculture, microbes and their bioactive compounds are being utilized in growth promotion and health promotion withnutrient fortification and its acquisition. Exhaustive explorations are unraveling the vast diversity of microbialcompounds with their potential usage in solving multiferous problems incrop production. Lipopeptides are one of such microbial compounds which havestrong antimicrobial properties against different plant pathogens. These compounds are reported to be produced by bacteria, cyanobacteria, fungi, and few other microorganisms; however, genus Bacillus alone produces a majority of diverse lipopeptides. Lipopeptides are low molecular weight compounds which havemultiple industrial roles apart from being usedas biosurfactants and antimicrobials. In plant protection, lipopeptides have wide prospects owing totheirpore-forming ability in pathogens, siderophore activity, biofilm inhibition, and dislodging activity, preventing colonization bypathogens, antiviral activity, etc. Microbes with lipopeptides that haveall these actions are good biocontrol agents. Exploring these antimicrobial compounds could widen the vistasof biological pest control for existing and emerging plant pathogens. The broader diversity and strong antimicrobial behavior of lipopeptides could be a boon for dealing withcomplex pathosystems and controlling diseases of greater economic importance. Understanding which and how these compounds modulate the synthesis and production of defense-related biomolecules in the plants is a key question—the answer of whichneeds in-depth investigation. The present reviewprovides a comprehensive picture of important lipopeptides produced by plant microbiome, their isolation, characterization, mechanisms of disease control, behavior against phytopathogens to understand different aspects of antagonism, and potential prospects for future explorations as antimicrobial agents. Understanding and exploring the antimicrobial lipopeptides from bacteria and fungi could also open upan entire new arena of biopesticides for effective control of devastating plant diseases.

In vitro efficacy of the lipopeptide biosurfactant surfactin-C15 and its complexes with divalent counterions to inhibit Candida albicans biofilm and hyphal formation

Surfactin is a type of cyclic lipopeptide biosurfactant implicated in a wide range of applications. Although its antimicrobial activity has been characterized, its effect on Candida albicans physiology remains to be elucidated. The present study evaluated the influence of surfactin-C₁₅ (SF) and its complexes with divalent counterions on C. albicans biofilm formation and preformed biofilms. The SF and metal(II)-SF complexes inhibited biofilm formation and reduced the metabolic activity of mature biofilms in a concentration-dependent manner. The same concentrations of the compounds studied dislodged preexisting biofilms grown on polystyrene plates. Moreover, SF and its metal(II) complexes reduced the mRNA expression of hypha-specific genes HWP1, ALS1, ALS3, ECE1 and SAP4 without exhibiting significant growth inhibition. Further research showed that the compounds tested reduced cellular surface hydrophobicity (CSH). These results suggest that SF and metal(II)-SF complexes could be used as anti-biofilm agents against C. albicans hypha-related infections in clinical practice.

Structure, properties, and biological functions of nonribosomal lipopeptides from pseudomonads

Bacteria of the genusPseudomonasdisplay a fascinating metabolic diversity. In this review, we focus our attention on the natural product class of nonribosomal lipopeptides, which help pseudomonads to colonize a wide range of ecological niches.

Design, synthesis and valued properties of surfactin oversimplified analogues

Surfactins are important lipopeptides produced by Bacillus subtilis that present strong surface activity. These biosurfactants find applications in various fields, from environmental remediation to medicine. The use of surfactins in remediation is hampered by production costs; the medical applications are also reframed because of the hemolytic activity of the cyclic peptide. To reduce costs and working time, the present work focused on the design, chemical synthesis and characterization of simple linear variants of surfactins having only L-amino acids and lauric acid at the N-terminal. Carboxyl-free and amidated analogues with negative, null and positive net charges at physiological pH were successfully obtained. The synthetic isoforms of surfactins showed high surface activity and ability to inhibit both growth and adhesion of Streptococcus mutans cells. Therefore, these properties make these low-cost synthetic peptides relevant and promising new compounds for science, industry and, mainly, dental care.

Cold-adapted bacterial extracts as a source of anti-infective and antimicrobial compounds against Staphylococcus aureus

Aim: The dramatic emergence of antibiotic resistance has directed the interest of research toward the discovery of novel antimicrobial molecules. In this context, cold-adapted marine bacteria living in polar regions represent an untapped reservoir of biodiversity endowed with an interesting chemical repertoire. The aim of this work was to identify new antimicrobials and/or antibiofilm molecules produced by cold-adapted bacteria. Materials & methods: Organic extracts obtained from polar marine bacteria were tested against Staphylococcus aureus. Most promising samples were subjected to suitable purification strategies. Results: Results obtained led to the identification of a novel lipopeptide able to effectively inhibit the biofilm formation of S. aureus. Conclusion: New lipopeptide may be potentially useful in a wide variety of biotechnological and medical applications.

Recent Patents on Impact of Lipopeptide on the Biofilm Formation onto Titanium and Stainless Steel Surfaces

BACKGROUND

Numerous causes of infection in arthroplasties are related to biofilm formation on implant surfaces. In order to circumvent this problem, new alternatives to prevent bacterial adhesion biosurfactants-based are emerging due to low toxicity, biodegradability and antimicrobial activity of several biosurfactants. We revised all patents relating to biosurfactants of applicability in orthopedic implants.

METHODS

This work aims to evaluate the capability of a lipopeptide produced by Bacillus subtilis ATCC 19659 isolates acting as inhibitors of the adhesion of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 onto titanium and stainless steel surfaces and its antimicrobial activity.

RESULTS

The adhesion of the strains to the stainless-steel surface was higher than that of titanium. Preconditioning of titanium and stainless-steel surfaces with 10 mg mL-1 lipopeptide reduced the adhesion of E. coli by up to 93% and the adhesion of S. aureus by up to 99.9%, suggesting the strong potential of lipopeptides in the control of orthopedic infections. The minimal inhibitory concentration and minimum bactericidal concentration were 10 and 240 µg mL-1 for E. coli and S. aureus, respectively.

CONCLUSION

The lipopeptide produced by Bacillus subtilis ATCC 19659 presented high biotechnological application in human health against orthopedic implants infections.

Metal-Biosurfactant Complexes Characterization: Binding, Self-Assembly and Interaction with Bovine Serum Albumin

Studies on the specific and nonspecific interactions of biosurfactants with proteins are broadly relevant given the potential applications of biosurfactant/protein systems in pharmaceutics and cosmetics. The aim of this study was to evaluate the interactions of divalent counterions with the biomolecular anionic biosurfactant surfactin-C₁₅ through molecular modeling, surface tension and dynamic light scattering (DLS), with a specific focus on its effects on biotherapeutic formulations. The conformational analysis based on a semi-empirical approach revealed that Cu²⁺ ions can be coordinated by three amide nitrogens belonging to the surfactin-C₁₅ cycle and one oxygen atom of the aspartic acid from the side chain of the lipopeptide. Backbone oxygen atoms mainly involve Zn²⁺, Ca²⁺ and Mg²⁺. Subsequently, the interactions between metal-coordinated lipopeptide complexes and bovine serum albumin (BSA) were extensively investigated by fluorescence spectroscopy and molecular docking analysis. Fluorescence results showed that metal-lipopeptide complexes interact with BSA through a static quenching mechanism. Molecular docking results indicate that the metal-lipopeptide complexes are stabilized by hydrogen bonding and van der Waals forces. The biosurfactant-protein interaction properties herein described are of significance for metal-based drug discovery hypothesizing that the association of divalent metal ions with surfactin allows its interaction with bacteria, fungi and cancer cell membranes with effects that are similar to those of the cationic peptide antibiotics.

Microbial biosurfactants: current trends and applications in agricultural and biomedical industries

Synthetic surfactants are becoming increasingly unpopular in many applications due to previously disregarded effects on biological systems and this has led to a new focus on replacing such products with biosurfactants that are biodegradable and produced from renewal resources. Microbially derived biosurfactants have been investigated in numerous studies in areas including: increasing feed digestibility in an agricultural context, improving seed protection and fertility, plant pathogen control, antimicrobial activity, antibiofilm activity, wound healing and dermatological care, improved oral cavity care, drug delivery systems and anticancer treatments. The development of the potential of biosurfactants has been hindered somewhat by the myriad of approaches taken in their investigations, the focus on pathogens as source species and the costs associated with large-scale production. Here, we focus on various microbial sources of biosurfactants and the current trends in terms of agricultural and biomedical applications.

Biosurfactant coated silver and iron oxide nanoparticles with enhanced anti-biofilm and anti-adhesive properties

Pseudomonas aeruginosa and Staphylococcus aureus are among the hazardous biofilm forming bacteria ubiquitous in industrial/clinical wastes. Serious efforts are required to develop effective strategies to control surface-growing antibiotic resistant pathogenic bacterial communities which they are emerging as a global health issue. Blocking hazardous biofilms would be a useful aspect of biosurfactant coated nanoparticles (NPs). In this regard, we report a facile method for the synthesis of rhamnolipid (RL) coated silver (Ag) and iron oxide (Fe₃O₄) NPs and propose the mechanism of their synergistic antibacterial and anti-adhesive properties against biofilms formed by P. aeruginosa and S. aureus. These NPs demonstrated excellent anti-biofilm activity not only during the biofilms formation but also on the pre-formed biofilms. Mechanistically, RL coated silver (35 nm) and Fe₃O₄ NPs (48 nm) generate reactive oxygen species, which contribute to the antimicrobial activity. The presence of RLs shell on the nanoparticles significantly reduces the cell adhesion by modifying the surface hydrophobicity and hence enhancing the anti-biofilm property of NPs against both mentioned strains. These findings suggest that RL coated Ag and Fe₃O₄ NPs may be used as potent alternate to reduce the infection severity by inhibiting the biofilm formation and, therefore, they possess potential biomedical applications for antibacterial coatings and wound dressings.

Bacteriocins: Classification, synthesis, mechanism of action and resistance development in food spoilage causing bacteria

Huge demand of safe and natural preservatives has opened new area for intensive research on bacteriocins to unravel the novel range of antimicrobial compounds that could efficiently fight off the food-borne pathogens. Since food safety has become an increasingly important international concern, the application of bacteriocins from lactic acid bacteria that target food spoilage/pathogenic bacteria without major adverse effects has received great attention. Different modes of actions of these bacteriocins have been suggested and identified, like pore-forming, inhibition of cell-wall/nucleic acid/protein synthesis. However, development of resistance in the food spoilage and pathogenic bacteria against these bacteriocins is a rising concern. Emergence and spread of mutant strains resistant to bacteriocins is hampering food safety. It has spurred an interest to understand the bacteriocin resistance phenomenon displayed by the food pathogens, which will be helpful in mitigating the resistance problem. Therefore, present review is focused on the different resistance mechanisms adopted by food pathogens to overcome bacteriocin.

Antimicrobial strategies for urinary catheters

Over 75% of hospital-acquired or nosocomial urinary tract infections are initiated by urinary catheters, which are used during the treatment of 16% of hospitalized patients. Taking the United States as an example, the costs of catheter-associated urinary tract infections (CAUTI) are in excess of $451 million dollars/year. The biofilm formation by pathogenic microbes that protects pathogens from host immune defense and antimicrobial agents is the leading cause for CAUTI. Thus, tremendous efforts have been devoted to antimicrobial coating for urinary catheters in the past few decades, and it has been demonstrated to be one of the most direct and efficient strategies to reduce infections. In this article, we briefly summarize the current methods for preparation of antimicrobial coatings based on different stages in the biofilm formation, highlight recent progress in the urinary catheter coating material design and selection, discuss approaches to improving their long-term antimicrobial efficacy, biocompatibility, multidrug resistance and recurrent infections, and finally outline future requirements and prospects in antimicrobial coating material design. The scope of the works surveyed is confined to antimicrobial urinary catheters. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 445-467, 2019.

Trehalose Lipid Biosurfactant Reduces Adhesion of Microbial Pathogens to Polystyrene and Silicone Surfaces: An Experimental and Computational Approach

Rhodococcus fascians BD8, isolated from Arctic soil, was found to produce biosurfactant when grown on n-hexadecane as the sole carbon source. The glycolipid product was identified as the trehalose lipid with a molecular mass of 848 g mol^-1. The purified biosurfactant reduced the surface tension of water from 72 to 34 mN m^-1. The critical micelle concentration of trehalose lipid was 0.140 mg mL^-1. To examine its potential for biomedical applications, the antimicrobial and antiadhesive activity of the biosurfactant was evaluated against several pathogenic microorganisms. Trehalose lipid showed antimicrobial activity against resistant pathogens. The largest antimicrobial activities of trehalose lipid were observed against Vibrio harveyi and Proteus vulgaris. The highest concentration tested (0.5 mg mL^-1) caused a partial (11-34%) inhibition of other Gram-positive and Gram-negative bacteria and 30% inhibition of Candida albicans growth. The trehalose lipid also showed significant antiadhesive properties against all of the tested microorganisms to polystyrene surface and silicone urethral catheters. The biosurfactant showed 95 and 70% antiadhesive activity against C. albicans and Escherichia coli, respectively. Finally, the role and application of trehalose lipid as an antiadhesive compound was investigated by the modification of the polystyrene and silicone surfaces. The intermolecular interaction energy calculations were performed for investigated complexes at the density functional level of theory. The results indicate that the presence of aromatic moieties can be substantial in the stabilization of trehalose lipid-surface complexes. The antimicrobial and antiadhesive activities of trehalose lipid make them promising alternatives to synthetic surfactants in a wide range of medical applications. Based on our findings, we propose that, because of its ability to inhibit microbial colonization of polystyrene and silicone surfaces, trehalose lipid can be used as a surface coating agent.

Cyclic Lipodepsipeptides From Pseudomonas spp. - Biological Swiss-Army Knives

Cyclic lipodepsipeptides produced by Pseudomonas spp. (Ps-CLPs) are biosurfactants that constitute a diverse class of versatile bioactive natural compounds with promising application potential. While chemically diverse, they obey a common structural blue-print, allowing the definition of 14 distinct groups with multiple structurally homologous members. In addition to antibacterial and antifungal properties the reported activity profile of Ps-CLPs includes their effect on bacterial motility, biofilm formation, induced defense responses in plants, their insecticidal activity and anti-proliferation effects on human cancer cell-lines. To further validate their status of potential bioactive substances, we assessed the results of 775 biological tests on 51 Ps-CLPs available from literature. From this, a fragmented view emerges. Taken as a group, Ps-CLPs present a broad activity profile. However, reports on individual Ps-CLPs are often much more limited in the scope of organisms that are challenged or activities that are explored. As a result, our analysis shows that the available data is currently too sparse to allow biological function to be correlated to a particular group of Ps-CLPs. Consequently, certain generalizations that appear in literature with respect to the biological activities of Ps-CLPs should be nuanced. This notwithstanding, the data for the two most extensively studied Ps-CLPs does indicate they can display activities against various biological targets. As the discovery of novel Ps-CLPs accelerates, current challenges to complete and maintain a useful overview of biological activity are discussed.

High-throughput optimization of medium components and culture conditions for the efficient production of a lipopeptide pseudofactin by Pseudomonas fluorescens BD5

Background

Lipopeptides are a promising group of surface-active compounds of microbial origin (biosurfactants). These diverse molecules are produced mainly by Bacillus and Pseudomonas strains. Because of their attractive physiochemical and biological properties, biosurfactants are considered to be “green and versatile molecules of the future”. The main obstacles in widespread use of biosurfactants are mainly their low yields and high production costs. Pseudofactin (PF) is a lipopeptide produced by Pseudomonas fluorescens BD5. Recently, we identified two analogues, PF1 (C₁₆-Val) and PF2 (C₁₆-Leu), and reported that PF2 has good emulsification and foaming activities, as well as antibacterial, antifungal, anticancer, and antiadhesive properties. Reported production of PF in a mineral salt medium was approximately 10 mg/L.

Results

Here, we report successful high-throughput optimization of culture medium and conditions for efficient PF production using P. fluorescens BD5. Compared with production in minimal medium, PF yield increased almost 120-fold, up to 1187 ± 13.0 mg/L. Using Plackett–Burman and central composite design methodologies we identified critical factors that are important for efficient PF production, mainly high glycerol concentration, supplementation with amino acids (leucine or valine) and complex additives (e.g. tryptone), as well as high culture aeration. We also detected the shift in a ratio of produced PF analogues in response to supplementation with different amino acids. Leucine strongly induces PF2 production, while valine addition supports PF1 production. We also reported the identification of two new PF analogues: PF3 (C₁₈-Val) and PF4 (C₁₈-Leu).

Conclusions

Identification of critical culture parameters that are important for lipopeptide production and their high yields can result in reduction of the production costs of these molecules. This may lead to the industrial-scale production of biosurfactants and their widespread use. Moreover, we produced new lipopeptide pure analogues that can be used to investigate the relationship between the structure and biological activity of lipopeptides.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0968-x) contains supplementary material, which is available to authorized users.

Gram-negative bacilli-derived peptide antibiotics developed since 2000

Gram-negative bacilli such as Pseudomonas spp., Pseudoalteromonas sp., Angiococcus sp., Archangium sp., Burkholderia spp., Chromobacterium sp., Chondromyces sp., Cystobacter sp., Jahnella sp., Janthinobacterium sp., Lysobacter spp., Paraliomyxa sp., Photobacterium spp., Photorhabdus sp., Pontibacter sp., Ruegeria sp., Serratia sp., Sorangium sp., Sphingomonas sp., and Xenorhabdus spp. produce an enormous array of short peptides of 30 residues or fewer that are potential pharmaceutical drugs and/or biocontrol agents. The need for novel lead antibiotic compounds is urgent due to increasing drug resistance, and this review summarises 150 Gram-negative bacilli-derived compounds reported since 2000, including 40 cyclic lipopeptides from Pseudomonas spp.; nine aromatic peptides; eight glycopeptides; 45 different cyclic lipopeptides; 24 linear lipopeptides; eight thiopeptides; one lasso peptide; ten typical cyclic peptides; and five standard linear peptides. The current and potential therapeutic applications of these peptides, including structures and antituberculotic, anti-cyanobacterial, antifungal, antibacterial, antiviral, insecticidal, and antiprotozoal activities are discussed.

Biosurfactant from a marine bacterium disrupts biofilms of pathogenic bacteria in a tropical aquaculture system

Bacterial infections are major constraints in aquaculture farming. These pathogens often adapt to the biofilm mode of growth and resist antibiotic treatments. We have used a non-toxic glycolipid biosurfactant (BS-SLSZ2) derived from a marine epizootic bacterium Staphylococcus lentus to treat aquaculture associated infections in an eco-friendly manner. We found that BS-SLSZ2 contained threose, a four-carbon sugar as the glycone component, and hexadecanoic and octadecanoic acids as the aglycone components. The critical micelle concentration of the purified glycolipid was 18 mg mL-1. This biosurfactant displayed anti-adhesive activity and inhibited biofilm formation by preventing initial attachment of cells onto surfaces. The biosurfactant (at a concentration of 20 μg) was able to inhibit Vibrio harveyi and Pseudomonas aeruginosa biofilms by 80.33 ± 2.16 and 82 ± 2.03%, respectively. At this concentration, it was also able to disrupt mature biofilms of V. harveyi (78.7 ± 1.93%) and P. aeruginosa (81.7 ± 0.59%). The biosurfactant was non-toxic towards Artemia salina. In vivo challenge experiments showed that the glycolipid was effective in protecting A. salina nauplii against V. harveyi and P. aeruginosa infections. This study highlights the significance of marine natural products in providing alternative biofilm controlling agents and decreasing the usage of antibiotics in aquaculture settings.