Inhibition of Bacterial and Fungal Biofilm Formation by 675 Extracts from Microalgae and Cyanobacteria

Integrated Biological and Chemical Investigation of Indonesian Marine Organisms Targeting Anti-Quorum-Sensing, Anti-Biofilm, Anti-Biofouling, and Anti-Biocorrosion Activities

Microorganisms play a significant role in biofouling and biocorrosion within the maritime industry. Addressing these challenges requires an innovative and integrated approach utilizing marine natural products with beneficial properties. A comprehensive screening of 173 non-toxic EtOAc and H₂O extracts derived from diverse marine organisms collected in Indonesian waters was conducted using a robust panel of assays. These included antimicrobial tests and classical biosurfactant assays (drop collapse and oil displacement), as well as anti-quorum-sensing (QS) and anti-biofilm assays. These screening efforts identified five active extracts with promising activities. Among these, EtOAc extracts of the marine tunicate Sigilina cf. signifera (0159-22e) and the marine sponge Lamellodysidea herbacea (0194-24c) demonstrated significant anti-biofouling activity against Perna indica and anti-biocorrosion performance (mpy 10.70 ± 0.70 for S. cf. signifera; 7.87 ± 0.86 for L. herbacea; 13.60 ± 1.70 for positive control Tetracorr CI-2915). Further chemical analyses of the active extracts, including LC-HR-MS/MS, MS-based molecular networking, and chemoinformatics, revealed the presence of both known and new bioactive compounds. These included tambjamines and polybrominated diphenyl ethers (PBDEs), which are likely contributors to the observed bioactivities. Subsequent investigations uncovered new anti-QS and anti-biofilm properties in synthetic and natural PBDEs 1-12 previously derived from L. herbacea. Among these, 8 exhibited the most potent anti-QS activity, with an IC50 value of 15 µM, while 4 significantly reduced biofilm formation at a concentration of 1 µM. This study highlights the potential of marine-derived compounds in addressing biofouling and biocorrosion challenges in a sustainable and effective manner.

Antibacterial Potential of Crude Extracts from Cylindrospermum alatosporum NR125682 and Loriellopsis cavernicola NR117881

The challenges of antimicrobial resistance (AMR) to human health have pushed for the discovery of a new antibiotics agent from natural products. Cyanobacteria are oxygen-producing photosynthetic prokaryotes found in a variety of water habitats. Secondary metabolites are produced by cyanobacteria to survive extreme environmental stress factors, including microbial competition. This study presents the antibacterial activity and mechanism of the crude extracts from Cylindrospermum alatosporum NR125682 (A) and Loriellopsis cavernicola NR117881 (B) isolated from freshwater. The cyanobacteria were identified through 16S rRNA sequencing. Crude extracts were sequentially prepared using hexane, dichloromethane, and ethanol consistently. The minimum inhibition concentration (MIC), minimum bactericidal concentration (MBC) using the CSLI microdilution test protocol, and crude extract potential to inhibit the growth of the tested clinical bacteria strains were evaluated. The mechanism of action of the extracts including membrane damage, efflux pump, β-lactamase activity, DNA degradation, and extract-drug interaction was investigated using standard procedures. The hexane extract of B performed the best with a MIC (0.7-1.41 mg/mL) and MBC (1.41-2.81 mg/mL) range. All the crude extracts inhibited efflux pump activity against the bacteria tested. However, the extracts poorly inhibited β-lactamase. The ethanol extract of B exhibited the most appreciable antibacterial activity. The dichloromethane extract of B showed the highest significant DNA degradation potential, when compared with other samples. The extracts exhibited synergism when combined with erythromycin against some test bacteria, indicating primary microbial activity through membrane interactions. Hence, this study demonstrates the significance of cyanobacteria for antibiotic development.

Investigation of Photodynamic and Rhamnolipid Inhibition on the Dermatophyte Biofilm

The failure to successfully treat dermatophyte-related diseases is often due to the formation of biofilms, which makes dermatophytes resistant to antifungals. Here, an attempt has been made to assess inhibition of dermatophyte biofilm production using photodynamic therapy and rhamnolipid biosurfactant. Two methods were used to inhibit biofilm formation by dermophytes Trichophyton mentagrophytes, Trichophyton rubrum and Trichophyton verrucosum, Microsporum canis and Microsporum gypseum. The first method was the use of rhamnolipid with concentrations of 39 to 1000 ppm and the second was the use of photodynamic method with concentrations of 8, 16 and 32 µg/ml of methylene blue. In addition, these two methods were evaluated simultaneously. The biofilm formation was evaluated using spectrophotometry and scanning electron microscopy. Biosurfactant has been shown to have an improved ability to inhibit the formation of biofilm by the strains. Although photodynamic therapy has not been successful, but in combination with biosurfactant, it may have a synergistic effect. By investigating the effect of rhamnolipid on the formation of biofilm, it was found that Microsporum species has a relatively stronger attachment to the surfaces of the wells compared to trichophyton species. The biofilms were evaluated with electron microscope in the simultaneous treatment of rhamnolipid and photodynamics. The results showed that after the treatment, the biofilms became discrete and their structural integrity was reduced. Even in Microsporum species, which were among the most resistant dermatophytes, the changes in the fungal biofilm after treatment were significant.

A unique combination of natural fatty acids from Hermetia illucens fly larvae fat effectively combats virulence factors and biofilms of MDR hypervirulent mucoviscus Klebsiella pneumoniae strains by increasing Lewis acid-base/van der Waals interactions in bacterial wall membranes

Introduction

Hypervirulent Klebsiella pneumoniae (hvKp) and carbapenem-resistant K. pneumoniae (CR-Kp) are rapidly emerging as opportunistic pathogens that have a global impact leading to a significant increase in mortality rates among clinical patients. Anti-virulence strategies that target bacterial behavior, such as adhesion and biofilm formation, have been proposed as alternatives to biocidal antibiotic treatments to reduce the rapid emergence of bacterial resistance. The main objective of this study was to examine the efficacy of fatty acid-enriched extract (AWME3) derived from the fat of Black Soldier Fly larvae (Hermetia illucens) in fighting against biofilms of multi-drug resistant (MDR) and highly virulent Klebsiella pneumoniae (hvKp) pathogens. Additionally, the study also aimed to investigate the potential mechanisms underlying this effect.

Methods

Crystal violet (CV) and ethidium bromide (EtBr) assays show how AWME3 affects the formation of mixed and mature biofilms by the KP ATCC BAA-2473, KPi1627, and KPM9 strains. AWME3 has shown exceptional efficacy in combating the hypermucoviscosity (HMV) virulent factors of KPi1627 and KPM9 strains when tested using the string assay. The rudimentary motility of MDR KPM9 and KP ATCC BAA-2473 strains was detected through swimming, swarming, and twitching assays. The cell wall membrane disturbances induced by AWME3 were detected by light and scanning electron microscopy and further validated by an increase in the bacterial cell wall permeability and Lewis acid-base/van der Waals characteristics of K. pneumoniae strains tested by MATS (microbial adhesion to solvents) method.

Results

After being exposed to 0.5 MIC (0.125 mg/ml) of AWME3, a significant reduction in the rudimentary motility of MDR KPM9 and KP ATCC BAA-2473 strains, whereas the treated bacterial strains exhibited motility between 4.23 ± 0.25 and 4.47 ± 0.25 mm, while the non-treated control groups showed significantly higher motility ranging from 8.5 ± 0.5 to 10.5 ± 0.5 mm.

Conclusion

In conclusion, this study demonstrates the exceptional capability of the natural AWME3 extract enriched with a unique combination of fatty acids to effectively eliminate the biofilms formed by the highly drug-resistant and highly virulent K. pneumoniae (hvKp) pathogens. Our results highlight the opportunity to control and minimize the rapid emergence of bacterial resistance through the treatment using AWME3 of biofilm-associated infections caused by hvKp and CRKp pathogens.

Anti-biofilm activity of marine algae-derived bioactive compounds

A large number of microbial species tend to communicate and produce biofilm which causes numerous microbial infections, antibiotic resistance, and economic problems across different industries. Therefore, advanced anti-biofilms are required with novel attributes and targets, such as quorum sensing communication system. Meanwhile, quorum sensing inhibitors as promising anti-biofilm molecules result in the inhibition of particular phenotype expression blocking of cell-to-cell communication, which would be more acceptable than conventional strategies. Many natural products are identified as anti-biofilm agents from different plants, microorganisms, and marine extracts. Marine algae are promising sources of broadly novel compounds with anti-biofilm activity. Algae extracts and their metabolites such as sulfated polysaccharides (fucoidan), carotenoids (zeaxanthin and lutein), lipid and fatty acids (γ-linolenic acid and linoleic acid), and phlorotannins can inhibit the cell attachment, reduce the cell growth, interfere in quorum sensing pathway by blocking related enzymes, and disrupt extracellular polymeric substances. In this review, the mechanisms of biofilm formation, quorum sensing pathway, and recently identified marine algae natural products as anti-biofilm agents will be discussed.

Marine Microalgae Schizochytrium sp. S31: Potential Source for New Antimicrobial and Antibiofilm Agent

BACKGROUND

The rise of antibiotic-resistant bacteria necessitates the discovery of new, safe, and bioactive antimicrobial compounds. The antibacterial and antibiofilm activity of microalgae makes them a potential candidate for developing natural antibiotics to limit microbial infection in various fields.

OBJECTIVE

This study aimed to analyze the antibacterial effect of the methanolic extract of Schizochytrium sp. S31 microalgae by broth microdilution and spot plate assays.

METHODS

The antibacterial effects of Schizochytrium sp. S31 extract was studied on gramnegative pathogens, Pseudomonas aeruginosa, Escherichia coli 35218, Klebsiella pneumonia, which cause many different human infections, and the gram-positive pathogen Streptococcus mutans. At the same time, the antibiofilm activity of the Schizochytrium sp. S31 extract on Pseudomonas aeruginosa and Escherichia coli 35218 bacteria were investigated by crystal violet staining method.

RESULTS

Schizochytrium sp. S31 extract at a 60% concentration for 8 hours displayed the highest antibacterial activity against P. aeruginosa, E. coli 35218, and K. pneumonia, with a decrease of 87%, 92%, and 98% in cell viability, respectively. The experiment with Streptococcus mutans revealed a remarkable antibacterial effect at a 60% extract concentration for 24 hours, leading to a notable 93% reduction in cell viability. Furthermore, the extract exhibited a dose-dependent inhibition of biofilm formation in P. aeruginosa and E. coli 35218. The concentration of 60% extract was identified as the most effective dosage in terms of inhibition.

CONCLUSION

This research emphasizes the potential of Schizochytrium sp. S31 as a natural antibacterial and antibiofilm agent with promising applications in the pharmaceutical sectors. This is the first study to examine the antibacterial activity of Schizochytrium sp. S31 microalgae using broth microdilution, spot plate assays, and the antibiofilm activity by a crystal staining method. The findings of this study show that Schizochytrium sp. S31 has antibacterial and antibiofilm activities against critical bacterial pathogens.

Prospect of nanomaterials as antimicrobial and antiviral regimen

In recent years studies of nanomaterials have been explored in the field of microbiology due to the increasing evidence of antibiotic resistance. Nanomaterials could be inorganic or organic, and they may be synthesized from natural products from plant or animal origin. The therapeutic applications of nano-materials are wide, from diagnosis of disease to targeted delivery of drugs. Broad-spectrum antiviral and antimicrobial activities of nanoparticles are also well evident. The ratio of nanoparticles surface area to their volume is high and that allows them to be an advantageous vehicle of drugs in many respects. Effective uses of various materials for the synthesis of nanoparticles impart much specificity in them to meet the requirements of specific therapeutic strategies. The potential therapeutic use of nanoparticles and their mechanisms of action against infections from bacteria, fungi and viruses were the focus of this review. Further, their potential advantages, drawbacks, limitations and side effects are also included here. Researchers are characterizing the exposure pathways of nano-medicines that may cause serious toxicity to the subjects or the environment. Indeed, societal ethical issues in using nano-medicines pose a serious question to scientists beyond anything.

Effect of culture conditions at lab-scale on metabolite composition and antibacterial and antibiofilm activities of Dunaliella tertiolecta

Dunaliella tertiolecta RCC6 was cultivated indoors in glass bubble column photobioreactors operated under batch and semi-continuous regimens and using two different conditions of light and temperature. Biomass was harvested by centrifugation, frozen, and then lyophilized. The soluble material was obtained by sequential extraction of the lyophilized biomass with solvents with a gradient of polarity (hexane, ethyl acetate, and methanol) and its metabolic composition was investigated through nuclear magnetic resonance (NMR) spectroscopy. The effect of light on chlorophyll biosynthesis was clearly shown through the relative intensities of the ¹ H NMR signals due to pheophytins. The highest signal intensity was observed for the biomasses obtained at lower light intensity, resulting in a lower light availability per cell. Under high temperature and light conditions, the ¹ H NMR spectra of the hexane extracts showed an incipient accumulation of triacylglycerols. In these conditions and under semi-continuous regimen, an enhancement of β-carotene and sterols production was observed. The antibacterial and antibiofilm activities of the extracts were also tested. Antibacterial activity was not detected, regardless of culture conditions. In contrast, the minimal biofilm inhibitory concentrations (MBICs) against Escherichia coli for the hexane extract obtained under semi-continuous regimen using high temperature and irradiance conditions was promising.

Using inorganic nanoparticles to fight fungal infections in the antimicrobial resistant era

Fungal infections pose a serious threat to human health and livelihoods. The number and variety of clinically approved antifungal drugs is very limited, and the emergence and rapid spread of resistance to these drugs means the impact of fungal infections will increase in the future unless alternatives are found. Despite the significance and major challenges associated with fungal infections, this topic receives significantly less attention than bacterial infections. A major challenge in the development of fungi-specific drugs is that both fungi and mammalian cells are eukaryotic and have significant overlap in their cellular machinery. This lack of fungi-specific drug targets makes human cells vulnerable to toxic side effects from many antifungal agents. Furthermore, antifungal drug resistance necessitates higher doses of the drugs, leading to significant human toxicity. There is an urgent need for new antifungal agents, specifically those that can limit the emergence of new resistant species. Non-drug nanomaterials have primarily been explored as antibacterial agents in recent years; however, they are also a promising source of new antifungal candidates. Thus, this article reviews current research on the use of inorganic nanoparticles as antifungal agents. We also highlight challenges facing antifungal nanoparticles and discuss possible future research opportunities in this field. STATEMENT OF SIGNIFICANCE: Fungal infections pose a growing threat to human health and livelihood. The rapid spread of resistance to current antifungal drugs has led to an urgent need to develop alternative antifungals. Nanoparticles have many properties that could make them useful antimycotic agents. To the authors' knowledge, there is no published review so far that has comprehensively summarized the current development status of antifungal inorganic nanomaterials, so we decided to fill this gap. In this review, we discussed the state-of-the-art research on antifungal inorganic nanoparticles including metal, metal oxide, transition-metal dichalcogenides, and inorganic non-metallic particle systems. Future directions for the design of inorganic nanoparticles with higher antifungal efficacy and lower toxicity are described as a guide for further development in this important area.

Innovative Strategies to Overcome Antimicrobial Resistance and Tolerance

Antimicrobial resistance and tolerance are natural phenomena that arose due to evolutionary adaptation of microorganisms against various xenobiotic agents. These adaptation mechanisms make the current treatment options challenging as it is increasingly difficult to treat a broad range of infections, associated biofilm formation, intracellular and host adapted microbes, as well as persister cells and microbes in protected niches. Therefore, novel strategies are needed to identify the most promising drug targets to overcome the existing hurdles in the treatment of infectious diseases. Furthermore, discovery of novel drug candidates is also much needed, as few novel antimicrobial drugs have been introduced in the last two decades. In this review, we focus on the strategies that may help in the development of innovative small molecules which can interfere with microbial resistance mechanisms. We also highlight the recent advances in optimization of growth media which mimic host conditions and genome scale molecular analyses of microbial response against antimicrobial agents. Furthermore, we discuss the identification of antibiofilm molecules and their mechanisms of action in the light of the distinct physiology and metabolism of biofilm cells. This review thus provides the most recent advances in host mimicking growth media for effective drug discovery and development of antimicrobial and antibiofilm agents.

Microalgae and Cyanobacteria Strains as Producers of Lipids with Antibacterial and Antibiofilm Activity

Lipids are one of the primary metabolites of microalgae and cyanobacteria, which enrich their utility in the pharmaceutical, feed, cosmetic, and chemistry sectors. This work describes the isolation, structural elucidation, and the antibiotic and antibiofilm activities of diverse lipids produced by different microalgae and cyanobacteria strains from two European collections (ACOI and LEGE-CC). Three microalgae strains and one cyanobacteria strain were selected for their antibacterial and/or antibiofilm activity after the screening of about 600 strains carried out under the NoMorFilm European project. The total organic extracts were firstly fractionated using solid phase extraction methods, and the minimum inhibitory concentration and minimal biofilm inhibitory concentration against an array of human pathogens were determined. The isolation was carried out by bioassay-guided HPLC-DAD purification, and the structure of the isolated molecules responsible for the observed activities was determined by HPLC-HRESIMS and NMR methods. Sulfoquinovosyldiacylglycerol, monogalactosylmonoacylglycerol, sulfoquinovosylmonoacylglycerol, α-linolenic acid, hexadeca-4,7,10,13-tetraenoic acid (HDTA), palmitoleic acid, and lysophosphatidylcholine were found among the different active sub-fractions selected. In conclusion, cyanobacteria and microalgae produce a great variety of lipids with antibiotic and antibiofilm activity against the most important pathogens causing severe infections in humans. The use of these lipids in clinical treatments alone or in combination with antibiotics may provide an alternative to the current treatments.

Recent Advances in Photodynamic Therapy against Fungal Keratitis

Fungal keratitis is a serious clinical infection on the cornea caused by fungi and is one of the leading causes of blindness in Asian countries. The treatment options are currently limited to a few antifungal agents. With the increasing incidence of drug-resistant infections, many patients fail to respond to antibiotics. Riboflavin-mediated corneal crosslinking (similar to photodynamic therapy (PDT)) for corneal ectasia was approved in the US in the early 2000s. Current evidence suggests that PDT could have the potential to inhibit fungal biofilm formation and overcome drug resistance by using riboflavin and rose bengal as photosensitizers. However, only a few clinical trials have been initiated in anti-fungal keratitis PDT treatment. Moreover, the removal of the corneal epithelium and repeated application of riboflavin and rose bengal are required to improve drug penetration before and during PDT. Thus, an improvement in trans-corneal drug delivery is mandatory for a successful and efficient treatment. In this article, we review the studies published to date using PDT against fungal keratitis and aim to enhance the understanding and awareness of this research area. The potential of modifying photosensitizers using nanotechnology to improve the efficacy of PDT on fungal keratitis is also briefly reviewed.

Antibacterial Activity and Amphidinol Profiling of the Marine Dinoflagellate Amphidinium carterae (Subclade III)

Microalgae have received growing interest for their capacity to produce bioactive metabolites. This study aimed at characterising the antimicrobial potential of the marine dinoflagellate Amphidinium carterae strain LACW11, isolated from the west of Ireland. Amphidinolides have been identified as cytotoxic polyoxygenated polyketides produced by several Amphidinium species. Phylogenetic inference assigned our strain to Amphidinium carterae subclade III, along with isolates interspersed in different geographic regions. A two-stage extraction and fractionation process of the biomass was carried out. Extracts obtained after stage-1 were tested for bioactivity against bacterial ATCC strains of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa. The stage-2 solid phase extraction provided 16 fractions, which were tested against S. aureus and E. faecalis. Fractions I, J and K yielded minimum inhibitory concentrations between 16 μg/mL and 256 μg/mL for both Gram-positive. A targeted metabolomic approach using UHPLC-HRMS/MS analysis applied on fractions G to J evidenced the presence of amphidinol type compounds AM-A, AM-B, AM-22 and a new derivative dehydroAM-A, with characteristic masses of m/z 1361, 1463, 1667 and 1343, respectively. Combining the results of the biological assays with the targeted metabolomic approach, we could conclude that AM-A and the new derivative dehydroAM-A are responsible for the detected antimicrobial bioactivity.

Microalgae produced during phycoremediation of swine wastewater contains effective bacteriostatic compounds against antibiotic-resistant bacteria

Studies on the antimicrobial effects of microalgae extracts are commonly reported using algae biomass grown in sterile synthetic mineral medium and controlled laboratory conditions. However, variations in environmental conditions and culture medium composition are known to alter microalgae biochemical structure possibly affecting the type and concentrations of bioactive compounds with antimicrobial properties. In this work, solvent extracts of the microalgae Chlorella spp. were tested for antimicrobial effects against gram-positive and multidrug resistant pathogenic bacteria Staphylococcus hyicus, Enterococcus faecalis and Streptococcus suis. Microalgae was cultivated at field scale open pond reactor using raw swine wastewater as growth substrate. Dichloromethane or methanol were used to obtain the microalgae extracts. Characterization of the extracts by ultra-high performance liquid chromatography-quadrupole mass spectrometry revealed the presence of 23 phytochemicals with recognized antimicrobial properties. Bacteriostatic activity was observed in plating assays by formation of inhibition zones ranging from 7 to 18 mm in diameter. Only dichloromethane extracts were inhibitory to all three model bacteria. The minimum inhibitory concentration assessed for dichloromethane extracts were 0.5 mg mL^-1 for Staphylococcus hyicus and Enterococcus faecalis and 0.2 mg mL^-1 for Streptococcus suis. Bactericidal effects were not observed using solvent-extracts at 2 or 5 mg L^-1. To the best of authors knowledge, this is the first report on the antimicrobial effects of Chlorella spp. extracts against Staphylococcus hyicus and Streptococcus suis. Overall, Chlorella spp. grown on swine wastewater contains several phytochemicals that could be further explored for the treatment of infections caused by antibiotic-resistant bacteria pathogens.

Antibiofilm and Anti-Candidal Activities of the Extract of the Marine Sponge Agelas dispar

This study aimed to determine the antifungal and antibiofilm activities of Agelas dispar on biofilm-producing Candida species. The methanolic extract of A. dispar was obtained and the fraction Ag2 showed inhibitory activity for all 13 Candida strains tested, in concentrations ranging from 2.5 to 0.15625 mg/mL. Antifungal activity of fungicidal nature was seen between 5.0 and 0.3125 mg/mL of extract against the strains. All the strains were classified as biofilm producers. The methanolic extract Ag2 was tested at concentrations of 2.5 and 1.25 mg/mL for antibiofilm activity against the biofilm formation and maturation in all the strains of the genus Candida. Treated and untreated biofilm samples were selected for visualization using scanning electron microscopy (SEM). SEM allowed the visualization of the quantitative decrease in the microbial community, alterations of structural morphology, and destruction of both the formation and maturation of biofilms, at the cellular level. The mechanism of action of this fraction is suggested to be at the plasma membrane and/or cell wall alteration level. Therefore, the use of the methanolic extract of A. dispar may be a promising antifungal and antibiofilm therapeutic strategy against different species of the genus Candida.

Fungal Biofilms as a Valuable Target for the Discovery of Natural Products That Cope with the Resistance of Medically Important Fungi-Latest Findings

The development of new antifungal agents that target biofilms is an urgent need. Natural products, mainly from the plant kingdom, represent an invaluable source of these entities. The present review provides an update (2017-May 2021) on the available information on essential oils, propolis, extracts from plants, algae, lichens and microorganisms, compounds from different natural sources and nanosystems containing natural products with the capacity to in vitro or in vivo modulate fungal biofilms. The search yielded 42 articles; seven involved essential oils, two Brazilian propolis, six plant extracts and one of each, extracts from lichens and algae/cyanobacteria. Twenty articles deal with the antibiofilm effect of pure natural compounds, with 10 of them including studies of the mechanism of action and five dealing with natural compounds included in nanosystems. Thirty-seven manuscripts evaluated Candida spp. biofilms and two tested Fusarium and Cryptococcus spp. Only one manuscript involved Aspergillus fumigatus. From the data presented here, it is clear that the search of natural products with activity against fungal biofilms has been a highly active area of research in recent years. However, it also reveals the necessity of deepening the studies by (i) evaluating the effect of natural products on biofilms formed by the newly emerged and worrisome health-care associated fungi, C. auris, as well as on other non-albicans Candida spp., Cryptococcus sp. and filamentous fungi; (ii) elucidating the mechanisms of action of the most active natural products; (iii) increasing the in vivo testing.

Eustigmatophyte strains with potential interest in cancer prevention and treatment: partial chemical characterization and evaluation of cytotoxic and antioxidant activity

The interest in bioactive compounds from microalgae is increasing since they have medicinal and nutritional areas. The present work aims to evaluate the potential pharmaceutical interest of extracts from three eustigmatophyte strains from the Coimbra Collection of Algae (ACOI): Chlorobotrys gloeothece, Chlorobotrys regularis and Characiopsis aquilonaris. Antioxidant and antiproliferative activities were determined as well as chlorophyll a, carotenoid and phenolic total contents. In addition, major pigments and sterols were identified and quantified. The three strains were grown until the stationary phase and then the biomass was extracted. Antioxidant activity was measured by TEAC, DPPH and FRAP assays and antiproliferative effect was assessed by the MTT method on MCF-7, PC-3 and NHDF cells. The pigment and phenolic total contents were determined by spectrophotometry. Of these strains, C. aquilonaris showed the highest antioxidant activity measured by TEAC and FRAP assays (23.98 ± 0.01 μmol TE eq g^-1 DW and 42.57 ± 0.04 μmol TE eq g^-1 DW, respectively), a selective effect in reduting MCF-7 cells proliferation and a larger amount of chlorophyll a, carotenoids and phenolic content (18.40 ± 0.00 μg chlorophyll a mg^-1 DW, 2.27 ± 0.00 mg carotenoids g^-1 DW and 6.23 ± 0.01 mg GAE g^-1 DW, respectively). A positive correlation between chlorophyll a and TEAC assay was observed, as well as between carotenoids and TEAC and FRAP assays, suggesting these compounds as important contributors to significant antioxidant activity. Violaxanthin, cholesterol and stigmasterol were present in larger amount in C. aquilonaris while C. regularis showed a higher amount of β-carotene. These results suggest that these three ACOI eustigmatophytes are promising for applications in the improvement of human health, particularly in cancer prevention and treatment.

Transpicuous-Cum-Fouling Resistant Copolymers of 3-Sulfopropyl Methacrylate and Methyl Methacrylate for Optronics Applications in Aquatic Medium and Healthcare

The scope of optical sensors and scanners in aquatic media, fluids, and medical diagnostics has been limited by paucity of transparent shielding materials with antifouling potential. In this research endeavor, facile synthesis, characterization, and bioassay of antifouling transparent functional copolymers are reported. Copolymers of 3-sulfopropyl methacrylate (SPMA) and methyl methacrylate (MMA) were synthesized by free radical polymerization in various proportions. Samples PSM20, PSM30, PSM40, PSM50, and PSM60 contain 20%, 30%, 40%, 50%, and 60% SPMA by weight, respectively. Resultant products were characterized by FTIR and 1H-NMR spectroscopy. The synthesized copolymers have exhibited excellent transparency, i.e., 75% to 88%, as determined by the UV-Vis spectroscopic analysis. Transmittance was decreased from 6% to 2% in these copolymers upon changing the concentration of 3-sulfopropyl methacrylate from 20% to 50% owing to bacterial and algal biofilm formation. Water contact angle values were ranged from 18° to 63° and decreased with the increase in the polarity of copolymers. The surface energy lowest value 58 mJ/m2 and highest value 72 mJ/m2 were calculated for PSM20 and PSM50, respectively, by the Chibowski approach and Young equation. Sample PSM50 has exhibited the highest antibacterial activities, i.e., 18 mm and 19 mm, against Escherichia coli and Staphylococcus aureus, respectively, by the disk diffusion method. Copolymer PSM50 has shown minimum algal adhesion for Dictyosphaerium algae as observed by optical microscopy. This lower bacterial and algal adhesion is attributed to higher concentrations of anionic SPMA monomer that cause electrostatic repulsion between functional groups of the polymer and microorganisms. Thus, the resultant PSM50 product has exhibited good potential for optronics shielding application in aquatic medium and medical diagnostics.

Transposon Insertion in the purL Gene Induces Biofilm Depletion in Escherichia coli ATCC 25922

Current Escherichia coli antibiofilm treatments comprise a combination of antibiotics commonly used against planktonic cells, leading to treatment failure. A better understanding of the genes involved in biofilm formation could facilitate the development of efficient and specific new antibiofilm treatments. A total of 2578 E. coli mutants were generated by transposon insertion, of which 536 were analysed in this study. After sequencing, Tn263 mutant, classified as low biofilm-former (LF) compared to the wild-type (wt) strain (ATCC 25922), showed an interruption in the purL gene, involved in the de novo purine biosynthesis pathway. To elucidate the role of purL in biofilm formation, a knockout was generated showing reduced production of curli fibres, leading to an impaired biofilm formation. These conditions were restored by complementation of the strain or addition of exogenous inosine. Proteomic and transcriptional analyses were performed to characterise the differences caused by purL alterations. Thirteen proteins were altered compared to wt. The corresponding genes were analysed by qRT-PCR not only in the Tn263 and wt, but also in clinical strains with different biofilm activity. Overall, this study suggests that purL is essential for biofilm formation in E. coli and can be considered as a potential antibiofilm target.

Enterococcus faecalis inhibits Klebsiella pneumoniae growth in polymicrobial biofilms in a glucose-enriched medium

Catheter-related urinary tract infections are one of the most common biofilm-associated diseases. Within biofilms, bacteria cooperate, compete, or have neutral interactions. This study aimed to investigate the interactions in polymicrobial biofilms of Klebsiella pneumoniae and Enterococcus faecalis, two of the most common uropathogens. Although K. pneumoniae was the most adherent strain, it could not maintain dominance in the polymicrobial biofilm due to the lactic acid produced by E. faecalis in a glucose-enriched medium. This result was supported by the use of E. faecalis V583 ldh-1/ldh-2 double mutant (non-producer of lactic acid), which did not inhibit the growth of K. pneumoniae. Lyophilized cell-free supernatants obtained from E. faecalis biofilms also showed antimicrobial/anti-biofilm activity against K. pneumoniae. Conversely, there were no significant differences in planktonic polymicrobial cultures. In summary, E. faecalis modifies the pH by lactic acid production in polymicrobial biofilms, which impairs the growth of K. pneumoniae.

Chlorosphaerolactylates A-D: Natural Lactylates of Chlorinated Fatty Acids Isolated from the Cyanobacterium Sphaerospermopsis sp. LEGE 00249

Four natural lactylates of chlorinated fatty acids, chlorosphaerolactylates A-D (1-4), were isolated from the methanolic extract of the cyanobacterium Sphaerospermopsis sp. LEGE 00249 through a combination of bioassay-guided and MS-guided approaches. Compounds 1-4 are esters of (mono-, di-, or tri)chlorinated lauric acid and lactic acid, whose structures were assigned on the basis of spectrometric and spectroscopic methods inclusive of 1D and 2D NMR experiments. High-resolution mass-spectrometry data sets also demonstrated the existence of other minor components that were identified as chlorosphaero(bis)lactylate analogues. The chlorosphaerolactylates were tested for potential antibacterial, antifungal, and antibiofilm properties using bacterial and fungal clinical isolates. Compounds 1-4 showed a weak inhibitory effect on the growth of Staphylococcus aureus S54F9 and Candida parapsilosis SMI416, as well as on the biofilm formation of coagulase-negative Staphylococcus hominis FI31.

Biofouling and me: My Stockholm syndrome with biofilms

Biofouling is the undesired deposition and growth of microorganisms on surfaces, forming biofilms. The definition is subjective and operational: not every biofilm causes biofouling - only if a given a subjective "threshold of interference" is exceeded, biofilms cause technical or medical problems. These range from the formation of slime layers on ship hulls or in pipelines, which increase friction resistance, to separation membranes, on which biofilms increase hydraulic resistance, to heat exchangers where they interfere with heat transport to contamination of treated water by eroded biofilm cells which may comprise hygienically relevant microorganisms, and, most dangerous, to biofilms on implants and catheters which can cause persistent infections. The largest fraction of anti-fouling research, usually in short-term experiments, is focused on prevention or limiting primary microbial adhesion. Intuitively, this appears only logical, but turns out mostly hopeless. This is because in technical systems with open access for microorganisms, all surfaces are colonized sooner or later which explains the very limited success of that research. As a result, the use of biocides remains the major tool to fight persistent biofilms. However, this is costly in terms of biocides, it stresses working materials, causes off-time and environmental damage and it usually leaves large parts of biofilms in place, ready for regrowth. In order to really solve biofouling problems, it is necessary to learn how to live with biofilms and mitigate their detrimental effects. This requires rather an integrated strategy than aiming to invent "one-shot" solutions. In this context, it helps to understand the biofilm way of life as a natural phenomenon. Biofilms are the oldest, most successful and most widely distributed form of life on earth, existing even in extreme environments and being highly resilient. Microorganisms in biofilms live in a self-produced matrix of extracellular polymeric substances (EPS) which allows them to develop emerging properties such as enhanced nutrient acquisition, synergistic microconsortia, enhanced tolerance to biocides and antibiotics, intense intercellular communication and cooperation. Transiently immobilized, biofilm organisms turn their matrix into an external digestion system by retaining complexed exoenzymes in the matrix. Biofilms grow even on traces of any biodegradable material, therefore, an effective anti-fouling strategy comprises to keep the system low in nutrients (good housekeeping), employing low-fouling, easy-to-clean surfaces, monitoring of biofilm development, allowing for early intervention, and acknowledging that cleaning can be more important than trying to kill biofilms, because cleaning does not cut the nutrient supply of survivors and dead biomass serves as an additional carbon source for "cannibalizing" survivors, supporting rapid after growth. An integrated concept is presented as the result of a long journey of the author through biofouling problems.

The Usefulness of Microalgae Compounds for Preventing Biofilm Infections

Biofilms play an important role in infectious diseases. It has been estimated that most medical infections are due to bacterial biofilms, and about 60-70% of nosocomial infections are also caused by the formation of a biofilm. Historically, microalgae are an important source of bioactive compounds, having novel structures and potential biological functions that make them attractive for different industries such as food, animal feed, aquaculture, cosmetics, and pharmaceutical. Several studies have described compounds produced by microalgae and cyanobacteria species with antimicrobial activity. However, studies on the antibiofilm activity of extracts and/or molecules produced by these microorganisms are scarce. Quorum-sensing inhibitor and anti-adherent agents have, among others, been isolated from microalgae and cyanobacteria species. The use of tools such as nanotechnology increase their power of action and can be used for preventing and treating biofilm-related infections.

The origin and evolution of cell-intrinsic antibacterial defenses in eukaryotes

To survive in a world dominated by bacteria, eukaryotes have evolved numerous self-defense strategies. While some defenses are recent evolutionary innovations, others are ancient, with roots early in eukaryotic history. With a focus on antibacterial immunity, we highlight the evolution of pattern recognition receptors that detect bacteria, where diverse functional classes have been formed from the repeated use and reuse of a small set of protein domains. Next, we discuss core microbicidal strategies shared across eukaryotes, and how these systems may have been co-opted from ancient cellular mechanisms. We propose that studying antibacterial responses across diverse eukaryotes can reveal novel modes of defense, while highlighting the critical innovations that occurred early in the evolution of our own immune systems.

Lutein: A potential antibiofilm and antiquorum sensing molecule from green microalga Chlorella pyrenoidosa

The increasing resistance of Pseudomonas aeruginosa towards antimicrobial agents has been a major cause for the escalation of untreatable diabetic foot ulcer cases around the globe. This demands research towards alternative natural products that inhibit biofilm formation by P. aeruginosa. The study focuses on enhancing as well as understanding the anti-biofilm property of lutein from Chlorella pyrenoidosa against MTCC strain of P. aeruginosa PAO1. C. pyrenoidosa was subjected to nutrient starvation (N^-, S^- and P^-) and their growth, biomass, chlorophyll pigments and total carotenoids were estimated. Lutein extracted from nutrient starved C. pyrenoidosa were quantified using High Performance Liquid Chromatography (HPLC) and also used for quantification of biofilm formation, cell surface hydrophobicity (CSH), extracellular polymeric substances (EPS) and pyocyanin degradation. The results showed 20 μg/mL concentration of lutein showed maximum inhibition and degradation of biofilm formation, pyocyanin production, Cell Surface Hydrophobicity Extracellular Polymeric Substances, when compared to other concentrations. Azithromycin was used as a standard drug to compare the efficiency of lutein as a potential antibiofilm compound. Docking studies confirmed the interaction of lutein with the four proteins - LasI, LasR, RhlI and RhlR, involved in the quorum sensing mechanism during biofilm formation. Among them, RhlI protein was found to strongly interact and LasI exhibiting the least interaction with lutein. Gene expression analyses of las and rhl genes in P. aeruginosa PAO1 revealed a significant down regulation of both the genes in the cultures treated with different concentrations of lutein. Therefore, it can be understood that lutein is an effective antibiofilm agent and can be used in combination with generic drugs that are used for treating diseases such as diabetic foot ulcers, which are ineffective due to high biofilm forming capability of P. aeruginosa and other bacterial species.