Attenuation of Las/Rhl quorum sensing regulated virulence and biofilm formation in Pseudomonas aeruginosa PAO1 by Artocarpesin.

The emergence of multidrug resistance and increased pathogenicity in microorganisms is conferred by the presence of highly synchronized cell density dependent signalling pathway known as quorum sensing (QS). The QS hierarchy is accountable for the secretion of virulence phenotypes, biofilm formation and drug resistance. Hence, targeting the QS phenomenon could be a promising strategy to counteract the bacterial virulence and drug resistance. In the present study, artocarpesin (ACN), a 6-prenylated flavone was investigated for its capability to quench the synthesis of QS regulated virulence factors. From the results, ACN showed significant inhibition of secreted virulence phenotypes such as pyocyanin (80%), rhamnolipid (79%), protease (69%), elastase (84%), alginate (88%) and biofilm formation (88%) in opportunistic pathogen, Pseudomonas aeruginosa PAO1. Further, microscopic observation of biofilm confirmed a significant reduction in biofilm matrix when P. aeruginosa PAO1 was supplemented with ACN at its sub-MIC concentration. Quantitative gene expression studies showed the promising aspects of ACN in down regulation of several QS regulatory genes associated with production of virulence phenotypes. Upon treatment with sub-MIC of ACN, the bacterial colonization in the gut of Caenorhabditis elegans was potentially reduced and the survival rate was greatly improved. The promising QS inhibition activities were further validated through in silico studies, which put an insight into the mechanism of QS inhibition. Thus, ACN could be considered as possible drug candidate targeting chronic microbial infections.

Alantolactone modulates the production of quorum sensing mediated virulence factors and biofilm formation in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen in immunocompromised patients and accounts for mortality worldwide. Quorum sensing (QS) and QS mediated biofilm formation of P. aeruginosa increase the severity of infection in the host. New and effective therapeutics are in high demand to eliminate Pseudomonas infections. The current study investigated the quorum quenching and biofilm inhibition properties of alantolactone (ATL) against P. aeruginosa PAO1. The production of key virulence factors and biofilm components were affected in bacteria when treated with sub-MIC of ATL and further validated by qRT-PCR studies. The anti-infective potential of ATL was corroborated in an in vivo model with improved survival of infected Caenorhabditis elegans and reduced bacterial colonization. In silico studies suggested the molecular interactions of ATL to QS proteins as stable. Finally, ATL was explored in the present study to inhibit QS pathways and holds the potential to develop into an effective anti-infective agent against P. aeruginosa.

Sesamin and sesamolin rescues Caenorhabditis elegans from Pseudomonas aeruginosa infection through the attenuation of quorum sensing regulated virulence factors.

Pseudomonas aeruginosa is an opportunistic pathogen emerging as a public health threat owing to their multidrug resistance profiles. The quorum sensing systems of P. aeruginosa play a pivotal role in the regulation of virulence and act as the target for the development of alternative therapeutics. The study discussed about anti-quorum sensing and antibiofilm properties of lignans (sesamin and sesamolin) found in Sesamum indicum (L.) against P. aeruginosa. The effect of lignans, sesamin and sesamolin on LasR/RhlR mediated virulence factor production, biofilm formation and bacterial motility were studied. To elucidate the mechanism of action of lignans on QS pathways, QS gene expression and in depth in silico analysis were performed. Both the lignans exerted anti-quorum sensing activity at 75 µg/ml without affecting the growth of bacteria. SA and SO exhibited decreased production of virulence factors such as pyocyanin, proteases, elastase and chitinase. The important biofilm constituents of P. aeruginosa including alginate, exopolysaccharides and rhamnolipids were strongly affected by the lignans. Likewise, plausible mechanism of action of lignans were determined through the down regulation of QS regulated gene expression, molecular docking and molecular simulation studies. The in vitro analysis was supported by C. elegans infection model. SA and SO rescued pre-infected worms within 8 days of post infection and reduced the colonization of bacteria inside the intestine due to the anti-infective properties of lignans. The lignans exhibited profound action on Las pathway rather than Rhl which was elucidated through in vitro and in silico assays. In silico pharmacokinetic analysis portrayed the opportunities to employ ligands as potential therapeutics for human use. The deep insights into the anti-QS, anti-biofilm and mechanism of action of lignans can contribute to the development of novel anti-infectives against pseuodmonal infections.

Astaxanthin protects oxidative stress mediated DNA damage and enhances longevity in Saccharomyces cerevisiae.

Reactive oxygen species (ROS) have long been found to play an important role in oxidative mediated DNA damage. Fortunately, cells possess an antioxidant system that can neutralize ROS. However, oxidative stress occurs when antioxidants are overwhelmed by ROS or impaired antioxidant pathways. This study was carried out to find the protective effect of astaxanthin on the yeast DNA repair-deficient mutant cells under hydrogen peroxide stress. The results showed that astaxanthin enhances the percent cell growth of rad1∆, rad51∆, apn1∆, apn2∆ and ogg1∆ cells. Further, the spot test and colony-forming unit count results confirmed that astaxanthin protects DNA repair mutant cells from oxidative stress. The DNA binding property of astaxanthin studied by in silico and in vitro methods indicated that astaxanthin binds to the DNA in the major and minor groove, and that might protect DNA against oxidative stress induced by Fenton's reagent. The intracellular ROS, 8-OHdG level and the DNA fragmentation as measured by comet tail was reduced by astaxanthin under oxidative stress. Similarly, reduced nuclear fragmentation and chromatin condensation results suggest that astaxanthin might reduce apoptosis. Finally, we show that astaxanthin decreases the accumulation of mutation rate and enhances the longevity of DNA repair-deficient mutants' cells during a chronological lifespan.

Astaxanthin enhances the longevity of Saccharomyces cerevisiae by decreasing oxidative stress and apoptosis.

The budding yeast, Saccharomyces cerevisiae, is an efficient model for studying oxidative stress, programmed cell death and aging. The present study was carried out to investigate antioxidant, the anti-apoptotic and anti-aging activity of a natural compound, astaxanthin, in S. cerevisiae model. The survivability of yeast antioxidant-deficient strains (sod1Δ, sod2Δ, cta1Δ, ctt1Δ and tsa1Δ) increased by 20%-40% when cells were pre-treated with astaxanthin, compared to hydrogen peroxide alone, as demonstrated in spot and colony forming unit assays. Reduced reactive oxygen species (ROS) levels, increased glutathione, decreased lipid peroxidation and induced superoxide dismutase activity in astaxanthin-treated cells indicate that astaxanthin protected the cells from oxidative-stress-induced cell death. In addition, astaxanthin protected anti-apoptotic-deficient strains (pep4Δ and fis1Δ) against acetic acid and hydrogen peroxide-induced cell death that suggests anti-apoptotic property of astaxanthin, and it was further confirmed by acridine orange/ethidium bromide, annexin V and 4',6-diamidino-2-phenylindole staining. The yeast chronological lifespan assay results showed that astaxanthin extends the lifespan of antioxidant-deficient strains by scavenging ROS, and anti-apoptotic-deficient mutants by protecting from apoptotic cell death compared to their respective untreated cells and wild type. Our results suggest that astaxanthin enhances the longevity of yeast S. cerevisiae by reducing oxidative stress and apoptosis.

Quercetin Protects Yeast Saccharomyces cerevisiae pep4 Mutant from Oxidative and Apoptotic Stress and Extends Chronological Lifespan.

The yeast Saccharomyces cerevisiae PEP4 gene encodes vacuolar endopeptidase proteinase A (Pep4p), which is a homolog of the human CTSD gene that encodes cathepsin D. Mutation of CTSD gene in human resulted in a number of neurodegenerative diseases. In this study, we have shown that yeast pep4 mutant cells are highly sensitive to oxidative and apoptotic stress induced by hydrogen peroxide and acetic acid, respectively. pep4∆ cells also showed accumulation of reactive oxygen species (ROS), apoptotic markers, and reduced chronological lifespan. In contrast, quercetin pretreatment protected the pep4 mutant from oxidative and apoptotic stress-induced sensitivity by scavenging ROS and reducing apoptotic markers. The percentage viability of quercetin-treated pep4∆ cells was more pronounced and increased stress resistance against oxidant, apoptotic, and heat stress during chronological aging. From our experimental results, we concluded that quercetin protects yeast pep4 mutant cells from oxidative stress and apoptosis, thereby increasing viability during chronological aging.

Quercetin enhances stress resistance in Saccharomyces cerevisiae tel1 mutant cells to different stressors.

The Saccharomyces cerevisiae TEL1 gene is an ortholog of the human ATM (Ataxia telangiectasia mutated) gene. S. cerevisiae tel1 mutant (tel1∆) lacking Tel1p, share some of the cellular defects with ATM mutation that includes prevention of oxidative damage repair, premature aging and apoptosis. In the present study, we investigated the protective effects of quercetin on the sensitivity of yeast S. cerevisiae tel1∆ cells exposed to oxidative, apoptotic and DNA damaging stress and viability of tel1∆ cells during chronological aging. Quercetin improved the stress resistance of tel1∆ cells when challenged with oxidants such as hydrogen peroxide (H2O2), menadine bisulphite (MBS) and tertiary butyl hydroperoxide (t-BHP) by scavenging reactive oxygen species (ROS). Quercetin protected the tel1∆ cells from acetic acid-induced apoptotic cell death and sensitivity against hydroxyurea. We found that quercetin attenuated ROS accumulation and apoptotic markers in tel1∆ cells and therefore an increase in cell viability during chronological aging. Our results from the S. cerevisiae model, suggest that use of quercetin as a food supplement might alleviate oxidative stress mediated DNA damage, apoptosis and age related damaging effects in AT patients and also improve health beneficial effects in humans.

Evaluation of in vivo antioxidant potential of Syzygium jambos (L.) Alston and Terminalia citrina Roxb. towards oxidative stress response in Saccharomyces cerevisiae.

Excessive production and restricted elimination of free radicals like superoxide, hydroxyl radical (·OH), anion radical (O2 ·-), and non-radical hydrogen peroxide (H2O2) are related to the development of cancer, arteriosclerosis, arthritis and neurodegenerative diseases. According to a report of World Health Organisation, about 80% of the population living in the developing countries predominantly depends on the traditional medicine for their primary healthcare. Plants possess innate ability to synthesize a wide variety of enzymatic and non-enzymatic antioxidants capable of attenuating ROS-induced oxidative damage. The ethanolic leaf extracts of Syzygium jambos L. and Terminalia citrina Roxb. exhibited a significant in vitro antioxidant activity when compared with natural antioxidant, ascorbic acid. The extracts also provided strong cellular protection against the damaging effects of H2O2 induced oxidative stress in the mutant strains (tsa1Δ and sod1Δ) of Saccharomyces cerevisiae. The GC-MS analysis of the leaf extracts revealed the presence of phytoconstituents majorly constituting of terpenes, vitamin and fatty acids contributing to the antioxidant property. The plant extracts may serve as a potential source of exogenous antioxidants to combat the undesirable effects of oxidative stress.

Determination of antioxidant potential of Acacia nilotica leaf extract in oxidative stress response system of Saccharomyces cerevisiae.

BACKGROUND: From ancient times, plants and plant-derived products have been used as folkloric medicines for a variety of health disorders owing to their tremendous therapeutic potential. The present study aimed to determine the antioxidant efficacy of crude Acacia nilotica extract in the oxidative stress response system of Saccharomyces cerevisiae as a model organism. RESULTS: Acacia nilotica showed significant antioxidant activity, with IC50 values of 75.157 and 159.57 µg mL-1 for 2,2-diphenyl-1-picrylhydrazyl radical and hydroxyl radical scavenging activities respectively at a concentration of 500 µg mL-1 . The total antioxidant activity of A. nilotica showed an ascorbic acid equivalent of 152.79 ± 7.43 µg mL-1 . The presence of phytoconstituents such as phytol and α-tocopherol from gas chromatography/mass spectrometry analysis confirmed the potential of A. nilotica as an antioxidant. The results were validated using the stress response mechanism in S. cerevisiae wild type and its isogenic deletion strains sod1Δ and tsa1Δ. Acacia nilotica substantially neutralized reactive oxygen species generated by hydrogen peroxide in mutant strains, as evident from spot assay and fluorescence assay using fluorescence microscopy and intensity studies. CONCLUSION: The results suggested the efficacy of A. nilotica as a potent antioxidant in the S. cerevisiae system for the first time and its use in neutraceuticals/therapeutics. © 2017 Society of Chemical Industry.

Determination of antioxidant activity of Hibiscus sabdariffa and Croton caudatus in Saccharomyces cerevisiae model system.

From ancient times, plants and plant derived products are exploited as a prominent source of folkloric medicines with tremendous therapeutic potential for an array of health disorders. In the present study, ethanolic leaf extract of Hibiscus sabdariffa and Croton caudatus were evaluated for free radical scavenging activity in Saccharomyces cerevisiae model system. H. sabdariffa and C. caudatus showed tremendous DPPH free radical scavenging potential with an IC50 value of 184.88 and 305.39 µg/mL respectively at a concentration of 500 µg/mL. The ethanolic leaf extract of H. sabdariffa and C. caudatus also showed significant hydoxyl radical scavenging and total antioxidant activity. Ascorbic acid was used as positive control. The in vitro antioxidant activity was further supported by in vivo studies using radical scavenging mechanism in S. cerevisiae wild type and its isogenic deletion strains sod1∆ and tsa1∆. The mutant yeast cells substantially scavenged the stress generated by H2O2 when supplemented with ethanolic leaf extract of H. sabdariffa and C. caudatus as evident from spot assays followed by fluorescence assay (DCF-DA) using fluorescence microscopic and intensity studies. H. sabdariffa and C.caudatus significantly neutralize the ROS level in yeast mutants with concomitant decrease in fluorescence intensity as compared to the untreated yeast cells. The results suggested the efficacy of H. sabdariffa and C. caudatus as potent antioxidants in yeast system and thus their futuristic applications in therapeutics.

Effects of gut microbiome and obesity on the development, progression and prevention of cancer (Review).

Cancer is one of the leading causes of death worldwide and it is estimated that the mortality rate of cancer will increase in the coming years. The etiology of the development and progression of cancer is multifactorial. Insights have been gained on the association between the human microbiome and tumor cell malignancy. A number of commensal microbe species are present in the human gut. They serve pivotal roles in maintaining several health and disease conditions, such as inflammatory bowel disease, irritable bowel syndrome, obesity and diabetes. Known major factors involved in cancer development include age, hormone levels, alcohol consumption, diet, being overweight, obesity, and infections, regardless of the type of cancer. Therefore, the present review aims to discuss the relationship between the gut microbiome and obesity­associated malignancies, including colorectal, gastric and liver cancer. Obesity has been reported to contribute to the development of numerous types of cancer primarily caused by high fatty food intake. In addition, obesity­associated microbiome alterations can lead to cancer and its progression. Dysbiosis of the gut microbiota can alter the metabolite profile, whilst increasing the levels of toxins, such as Bacteroides fragilis toxin and colibactin and cytolethal distending toxin, which are responsible for oncogenesis. The present review provides insights into the impact of gut microbiome dysbiosis on the progression of different types of cancers associated with obesity. It also discusses possible strategies for preserving a healthy gut microbiome. Different pre­clinical and clinical models are available for studying cancer development downstream of gut microbiome dysbiosis. Furthermore, the role of metabolites or drugs employed in colorectal, gastric and liver cancer therapy would be discussed.

A quantitative systems approach reveals dynamic control of tRNA modifications during cellular stress.

Decades of study have revealed more than 100 ribonucleoside structures incorporated as post-transcriptional modifications mainly in tRNA and rRNA, yet the larger functional dynamics of this conserved system are unclear. To this end, we developed a highly precise mass spectrometric method to quantify tRNA modifications in Saccharomyces cerevisiae. Our approach revealed several novel biosynthetic pathways for RNA modifications and led to the discovery of signature changes in the spectrum of tRNA modifications in the damage response to mechanistically different toxicants. This is illustrated with the RNA modifications Cm, m(5)C, and m(2) (2)G, which increase following hydrogen peroxide exposure but decrease or are unaffected by exposure to methylmethane sulfonate, arsenite, and hypochlorite. Cytotoxic hypersensitivity to hydrogen peroxide is conferred by loss of enzymes catalyzing the formation of Cm, m(5)C, and m(2) (2)G, which demonstrates that tRNA modifications are critical features of the cellular stress response. The results of our study support a general model of dynamic control of tRNA modifications in cellular response pathways and add to the growing repertoire of mechanisms controlling translational responses in cells.

Cellular senescence in aging: Molecular basis, implications and therapeutic interventions.

Cellular senescence is an irreversible proliferation arrest in response to cellular damage and stress. Although cellular senescence is a highly stable cell cycle arrest, it can influence many physiological, pathological, and aging processes. Cellular senescence can be triggered by various intrinsic and extrinsic stimuli such as oxidative stress, mitochondrial dysfunction, genotoxic stress, oncogenic activation, irradiation and chemotherapeutic agents. Senescence is associated with several molecular and phenotypic alterations, such as senescence-associated secretory phenotype (SASP), cell cycle arrest, DNA damage response (DDR), senescence-associated ß-galactosidase, morphogenesis, and chromatin remodeling. Cellular senescence is a regular physiological event involved in tissue homeostasis, embryonic development, tissue remodeling, wound healing, and inhibition of tumor progression. Mitochondria are one of the organelles that undergo significant morphological and metabolic changes associated with senescence. Recent evidence unraveled that inter-organelle communication regulates cellular senescence, where mitochondria form a highly complex and dynamic network throughout the cytoplasm with other organelles, like the endoplasmic reticulum. An imbalance in organelle interactions may result in faulty cellular homeostasis, which contributes to cellular senescence and is associated with organ aging. Since mitochondrial dysfunction is a common characteristic of cellular senescence and age-related diseases, mitochondria-targeted senolytic or redox modulator senomorphic strategies help solve the complex problems with the detrimental consequences of cellular senescence. Understanding the regulation of mitochondrial metabolism would provide knowledge on effective therapeutic interventions for aging and age-related pathologies. This chapter focuses on the biochemical and molecular mechanisms of senescence and targeting senescence as a potential strategy to alleviate age-related pathologies and support healthy aging.

Loss of tRNA methyltransferase 9 and DNA damage response genes in yeast confers sensitivity to aminoglycosides.

tRNA methyltransferase 9 (Trm9)-catalysed tRNA modifications have been shown to translationally enhance the DNA damage response (DDR). Here, we show that Saccharomyces cerevisiae trm9Δ, distinct DNA repair and spindle assembly checkpoint (SAC) mutants are differentially sensitive to the aminoglycosides tobramycin, gentamicin and amikacin, indicating DDR and SAC activation might rely on translation fidelity, under aminoglycoside stress. Further, we report that the DNA damage induced by aminoglycosides in the base excision repair mutants ogg1Δ and apn1Δ is mediated by reactive oxygen species, which induce the DNA adduct 8-hydroxy deoxyguanosine. Finally, the synergistic effect of tobramycin and the DNA-damaging agent bleomycin to sensitize trm9Δ and the DDR mutants mlh1Δ, rad51Δ, mre11Δ and sgs1Δ at significantly lower concentrations compared with wild-type suggests that cells with tRNA modification dysregulation and DNA repair gene defects can be selectively sensitized using a combination of translation inhibitors and DNA-damaging agents.

Bioactive molecules from haloarchaea: Scope and prospects for industrial and therapeutic applications.

Marine environments and salty inland ecosystems encompass various environmental conditions, such as extremes of temperature, salinity, pH, pressure, altitude, dry conditions, and nutrient scarcity. The extremely halophilic archaea (also called haloarchaea) are a group of microorganisms requiring high salt concentrations (2-6 M NaCl) for optimal growth. Haloarchaea have different metabolic adaptations to withstand these extreme conditions. Among the adaptations, several vesicles, granules, primary and secondary metabolites are produced that are highly significant in biotechnology, such as carotenoids, halocins, enzymes, and granules of polyhydroxyalkanoates (PHAs). Among halophilic enzymes, reductases play a significant role in the textile industry and the degradation of hydrocarbon compounds. Enzymes like dehydrogenases, glycosyl hydrolases, lipases, esterases, and proteases can also be used in several industrial procedures. More recently, several studies stated that carotenoids, gas vacuoles, and liposomes produced by haloarchaea have specific applications in medicine and pharmacy. Additionally, the production of biodegradable and biocompatible polymers by haloarchaea to store carbon makes them potent candidates to be used as cell factories in the industrial production of bioplastics. Furthermore, some haloarchaeal species can synthesize nanoparticles during heavy metal detoxification, thus shedding light on a new approach to producing nanoparticles on a large scale. Recent studies also highlight that exopolysaccharides from haloarchaea can bind the SARS-CoV-2 spike protein. This review explores the potential of haloarchaea in the industry and biotechnology as cellular factories to upscale the production of diverse bioactive compounds.

Surveillance and mitigation of soil pollution through metagenomic approaches.

Soil pollution is one of the serious global threats causing risk to environment and humans. The major cause of accumulation of pollutants in soil are anthropogenic activities and some natural processes. There are several types of soil pollutants which deteriorate the quality of human life and animal health. They are recalcitrant hydrocarbon compounds, metals, antibiotics, persistent organic compounds, pesticides and different kinds of plastics. Due to the detrimental properties of pollutants present in soil on human life and ecosystem such as carcinogenic, genotoxic and mutagenic effects, alternate and effective methods to degrade the pollutants are recommended. Bioremediation is an effective and inexpensive method of biological degradation of pollutants using plants, microorganisms and fungi. With the advent of new detection methods, the identification and degradation of soil pollutants in different ecosystems were made easy. Metagenomic approaches are a boon for the identification of unculturable microorganisms and to explore the vast bioremediation potential for different pollutants. Metagenomics is a power tool to study the microbial load in polluted or contaminated land and its role in bioremediation. In addition, the negative ecosystem and health effect of pathogens, antibiotic and metal resistant genes found in the polluted area can be studied. Also, the identification of novel compounds/genes/proteins involved in the biotechnology and sustainable agriculture practices can be performed with the integration of metagenomics.

Soil carries diverse microorganisms which maintain plant and soil health.The different types of recalcitrant soil pollutants affect the ecosystem and human health.Complex pollutants can be degraded through bioremediation using microorganisms/plantsMetagenomic approaches help to explore novel organisms and enzymes involved in bioremediation.

Translational infidelity-induced protein stress results from a deficiency in Trm9-catalyzed tRNA modifications.

Correct codon-anticodon pairing promotes translational fidelity, with these interactions greatly facilitated by modified nucleosides found in tRNA. We hypothesized that wobble uridine modifications catalyzed by tRNA methyltransferase 9 (Trm9) are essential for translational fidelity. In support, we have used phenotypic, reporter and protein-based assays to demonstrate increased translational infidelity in trm9Δ Saccharomyces cerevisiae cells. Codon reengineering studies suggest that Trm9-catalyzed tRNA modifications promote fidelity during the translation of specific genes, those rich in arginine and glutamic acid codons from mixed boxes. Using quantitative tRNA modification analysis, we determined that trm9Δ cells are only deficient in 2 of 23 tRNA modifications, with those 2, 5-methoxycarbonylmethyluridine (mcm ( 5) U) and 5-methoxycarbonylmethyl-2-thiouridine (mcm ( 5) s ( 2) U), classified as key determinants of translational fidelity. We also show that in the absence of mcm ( 5) U and mcm ( 5) s ( 2) U, the resulting translational infidelity promotes protein errors and activation of unfolded protein and heat shock responses. These data support a model in which Trm9-catalyzed tRNA modifications promote fidelity during the translation of specific transcripts, with decreased wobble base modification leading to translational infidelity, protein errors and activation of protein stress response pathways.

Metagenomic insights into taxonomic, functional diversity and inhibitors of microbial biofilms.

Microbial cells attached to inert or living surfaces adopt biofilm mode with self-produced exopolysaccharide matrix containing polysaccharides, proteins, and extracellular DNA, for protection from adverse external stimuli. Biofilms in hospitals and industries serve as a breeding ground for drug-resistant pathogens and ARG enrichment that are linked to pathogenicity and also impede industrial production process. Biofilm formation, including virulence and pathogenicity, is regulated through quorum sensing (QS), a means of bacterial cell to cell communication for cooperative physiological processes. Hence, QS inhibition through quorum quenching (QQ) is a feasible approach to inhibit biofilm formation. In contrast, biofilms have beneficial roles in promoting plant growth, biocontrol, and wastewater treatment. Furthermore, polymicrobial biofilms can harbour novel compounds and species of industrial and pharmaceutical interest. Hence, surveillance of biofilm microbiome structure and functional attributes is crucial to determine the extent of the risk it poses and to harness its bioactive potential. One of the most preferred approaches to delineate the microbiome is culture-independent metagenomics. In this context, this review article explores the biofilm microbiome in built and natural settings such as agriculture, household appliances, wastewater treatment plants, hospitals, microplastics, and dental biofilm. We have also discussed the recent reports on discoveries of novel QS and biofilm inhibitors through conventional, metagenomics, and machine learning approaches. Finally, we present biofilm-derived novel metagenome-assembled genomes (MAGs), genomes, and taxa of medical and industrial interest.

Betulinic acid mitigates oxidative stress-mediated apoptosis and enhances longevity in the yeast Saccharomyces cerevisiae model.

Betulinic acid (BA), a pentacyclic triterpenoid found in certain plant species, has been reported to have several health benefits including antioxidant and anti-apoptotic properties. However, the mechanism by which BA confers these properties is currently unknown. Saccharomyces cerevisiae, a budding yeast with a short life cycle and conserved cellular mechanism with high homology to humans, was used as a model for determining the role of BA in aging and programmed cell death (PCD). Treatment with hydrogen peroxide (H2O2) exhibited significantly increased (30-35%) survivability of antioxidant (sod1Δ, sod2Δ, cta1Δ, ctt1Δ, and tsa1Δ) and anti-apoptotic (pep4Δ and fis1Δ) mutant strains when cells were pretreated with BA (30 µM) as demonstrated in spot and CFU (Colony forming units) assays. Measurement of intracellular oxidation level using the ROS-specific dye H2DCF-DA showed that all tested BA-pretreated mutants exhibited decreased ROS than the control when exposed to H2O2. Similarly, when mutant strains were pretreated with BA and then exposed to H2O2, there was reduced lipid peroxidation as revealed by the reduced malondialdehyde content. Furthermore, BA-pretreated mutant cells showed significantly lower apoptotic activity by decreasing DNA/nuclear fragmentation and chromatin condensation under H2O2-induced stress as determined by DAPI and acridine orange/ethidium bromide staining. In addition, BA treatment also extended the life span of antioxidant and anti-apoptotic mutants by ∼10-25% by scavenging ROS and preventing apoptotic cell death. Our overall results suggest that BA extends the chronological life span of mutant strains lacking antioxidant and anti-apoptotic genes by lowering the impact of oxidative stress, ROS levels, and apoptotic activity. These properties of BA could be further explored for its use as a valuable nutraceutical.