Mechanisms of membrane toxicity of hydrocarbons

Microbial remediation of petroleum-contaminated soil focused on the mechanism and microbial response: a review

The environmental pollution caused by petroleum hydrocarbons has received considerable attention in recent years. Microbial remediation has emerged as the preferred method for the degradation of petroleum hydrocarbons, which is experiencing rapid development driven by advancements in molecular biology. Herein, the capacity of different microorganisms used for crude oil bioremediation was reviewed. Moreover, factors influencing the effectiveness of microbial remediation were discussed. Microbial remediation methods, such as bioaugmentation, biostimulation, and bioventilation, are summarized in this review. Aerobic and anaerobic degradation mechanisms were reviewed to elucidate the metabolic pathways involved. The impacts of petroleum hydrocarbons on microorganisms and the environment were also revealed. A brief overview of synthetic biology and a unique perspective of technique combinations were presented to provide insight into research trends. The challenges and future outlook were also presented to stimulate contemplation of the mechanisms involved and the development of innovative techniques.

Anticoccidial and jejunum-protective effects of Krameria lappacea roots extract on experimental Eimeria papillata infection

Coccidiosis is a protozoan parasitic disease caused by Eimeria species and affects wild and domestic animals. Coccidiostats are currently available to control this disease, although drug resistance has been confirmed for all of them. As a result, there is an urgent need to identify eco-friendly agents to control and treat this disease. This study aimed to investigate the ameliorative role of the Krameria lappacea roots extract (KLRE) on the outcome of coccidiosis induced by Eimeria papillata. Male C57BL/6 mice were divided into seven groups (5 mice/group), as follows: Group 1: noninfected-nontreated (control group), Group 2: noninfected-treated group with KLRE (200 mg/kg), Group 3: infected-nontreated group, Group 4: infected-treated group with KLRE (50 mg/kg), Group 5: infected-treated group with KLRE (100 mg/kg), Group 6: infected-treated group with KLRE (200 mg/kg), and Group 7: infected-treated group with amprolium (120 mg/kg). Groups (3-7) were inoculated orally with 1 × 103 sporulated E. papillata oocysts. One hour after infection, groups (4-6) were daily treated for 5 days with KLRE and amprolium. On day 5 postinfection, oocyst output was determined, and mice were euthanized for the collection of jejuna then preparation of histological sections and jejunal homogenate was used for the determination of biochemical and oxidative damage markers. The coccidial infection induced weight loss of mice by 3.971%, which improved after KLRE to -1.512%. After KLRE treatment, the rate of feed intake was improved to be 52.21 ± 2.30 than those in infected group (40.47 ± 2.25). Oocyst output was significantly reduced in mice treated with KLRE (1.308 × 106 oocysts/g.feces) compared with those in the infected group (5.387 × 106 oocysts/g.feces). E. papillata infection induced marked histological alterations within jejunum tissue. After treatment, KLRE was able to impair the development of parasite stages (meronts, gamonts, and developing oocysts) in the jejunum through a significant reduction of number and size in comparison with the infected group. Infection with E. papillata induced a disturbance in the nutrient absorption in the jejunal mice tissue, which improved after the treatment with KLRE and amprolium. Also, KLRE counteracted significantly the E. papillata-induced loss of reduced glutathione and total antioxidant capacity. Our findings indicate that KLRE could be used as an alternative to the available coccidiostats currently available. RESEARCH HIGHLIGHTS: Krameria lappacea exhibit significant anticoccidial and antioxidant activities induced by E. papillata infection. Krameria lappacea exhibit significant improvement in the pathological alterations of the jejunal tissue induced by E. papillata infection.

A Membrane Biophysics Perspective on the Mechanism of Alcohol Toxicity

Motivations for understanding the underlying mechanisms of alcohol toxicity range from economical to toxicological and clinical. On the one hand, acute alcohol toxicity limits biofuel yields, and on the other hand, acute alcohol toxicity provides a vital defense mechanism to prevent the spread of disease. Herein the role that stored curvature elastic energy (SCE) in biological membranes might play in alcohol toxicity is discussed, for both short and long-chain alcohols. Structure-toxicity relationships for alcohols ranging from methanol to hexadecanol are collated, and estimates of alcohol toxicity per alcohol molecule in the cell membrane are made. The latter reveal a minimum toxicity value per molecule around butanol before alcohol toxicity per molecule increases to a maximum around decanol and subsequently decreases again. The impact of alcohol molecules on the lamellar to inverse hexagonal phase transition temperature (T_H) is then presented and used as a metric to assess the impact of alcohol molecules on SCE. This approach suggests the nonmonotonic relationship between alcohol toxicity and chain length is consistent with SCE being a target of alcohol toxicity. Finally, in vivo evidence for SCE-driven adaptations to alcohol toxicity in the literature are discussed.

Relation of xylitol formation and lignocellulose degradation in yeast

One of the critical steps of the biotechnological production of xylitol from lignocellulosic biomass is the deconstruction of the plant cell wall. This step is crucial to the bioprocess once the solubilization of xylose from hemicellulose is allowed, which can be easily converted to xylitol by pentose-assimilating yeasts in a microaerobic environment. However, lignocellulosic toxic compounds formed/released during plant cell wall pretreatment, such as aliphatic acids, furans, and phenolic compounds, inhibit xylitol production during fermentation, reducing the fermentative performance of yeasts and impairing the bioprocess productivity. Although the toxicity of lignocellulosic inhibitors is one of the biggest bottlenecks of the biotechnological production of xylitol, most of the studies focus on how much xylitol production is inhibited but not how and where cells are affected. Understanding this mechanism is important in order to develop strategies to overcome lignocellulosic inhibitor toxicity. In this mini-review, we addressed how these inhibitors affect both yeast physiology and metabolism and consequently xylose-to-xylitol bioconversion. In addition, this work also addresses about cellular adaptation, one of the most relevant strategies to overcome lignocellulosic inhibitors toxicity, once it allows the development of robust and tolerant strains, contributing to the improvement of the microbial performance against hemicellulosic hydrolysates toxicity. KEY POINTS: • Impact of lignocellulosic inhibitors on the xylitol production by yeasts • Physiological and metabolic alterations provoked by lignocellulosic inhibitors • Cell adaptation as an efficient strategy to improve yeast's robustness.

Separation and Qualitative Study of Mentha asiatica Boriss. Essential Oil Components by prep-GC, GC-QTOF-MS, NMR and Prediction of Bioactive Compounds

In order to understand the material basis of wild Mentha asiatica Boris. in Xinjiang, the chemical constituents of essential oil extracted from aerial parts of this plant were studied. A total 52 components were detected and 45 compounds were identified. First of all, the essential oil was separated by silica gel column chromatography, and divided into several parts according to the results of thin layer chromatography. Eight fractions were obtained, and then each fragment was preliminarily screened for antibacterial activity. It was found that all eight fragments had certain antibacterial activity in different level. Then the fractions were subjected to preparative gas chromatography (prep-GC) for further isolation. Ten compounds were identified by ¹³ C-NMR, ¹ H-NMR and gas chromatography-quadrupole time of flight-Mass spectrometry (GC-QTOF-MS). They are sabinene, limonene and β-caryophyllene, (1R*,3S*,5R*)-sabinyl acetate, piperitone oxide, rotundifolone, thymol, piperitone, 4-hydroxypiperiditone, cedrol. After screened by bioautography, 4-hydroxypiperone and thymol were showed best antibacterial activity. The inhibitory effects of the two isolated compounds on Candida albicans and their related mechanisms were studied. The results showed that, 4-hydroxypiperone and thymol significantly reduced ergosterol content on the surface of Candida albicans cell membrane in a dose-dependent manner. This work has accumulated experience for the development and utilization of Xinjiang characteristic medicinal plant resources and new drug research and development, and provided scientific basis and support for the later research and development of Mentha asiatica Boris.

Effects of trehalose and ergosterol on pinene stress of Candida glycerinogenes

Pinene is a commercially important monoterpene that can be prepared using engineered bacterial and yeast species; however, high pinene levels can adversely affect the stability and permeability of microbial membranes leading to significantly reduced growth yields. This study reports that the fluidities and permeabilities of cell membranes of Candida glycerinogenes decrease as pinene levels increase resulting in adverse effects on cell growth. Exposure of cells to pinene results in upregulation of the genes encoding ergosterol and trehalose whose production helps stabilize their cell membranes. Exogenous addition of ergosterol and trehalose to pinene-treated cells also reduces the fluidity and permeability of the cell membrane, whilst also reducing production of intracellular reactive oxygen species. This led to the finding that the biomass of yeast cells cultivated in shake flask systems are improved by exogenous addition of trehalose and ergosterol. Overexpression of genes that encode trehalose and ergosterol produced a recombinant C. glycerinogenes strain that was found to tolerate higher concentrations of  pinene.

Surfaces with instant and persistent antimicrobial efficacy against bacteria and SARS-CoV-2

Surfaces contaminated with bacteria and viruses contribute to the transmission of infectious diseases and pose a significant threat to global public health. Modern day disinfection either relies on fast-acting (>3-log reduction within a few minutes), yet impermanent, liquid-, vapor-, or radiation-based disinfection techniques, or long-lasting, but slower-acting, passive antimicrobial surfaces based on heavy metal surfaces, or metallic nanoparticles. There is currently no surface that provides instant and persistent antimicrobial efficacy against a broad spectrum of bacteria and viruses. In this work, we describe a class of extremely durable antimicrobial surfaces incorporating different plant secondary metabolites that are capable of rapid disinfection (>4-log reduction) of current and emerging pathogens within minutes, while maintaining persistent efficacy over several months and under significant environmental duress. We also show that these surfaces can be readily applied onto a variety of desired substrates or devices via simple application techniques such as spray, flow, or brush coating.

Assessment of the toxicity of weathered petroleum hydrocarbon impacted soils to native plants from a site in the Canadian Subarctic

Remedial guidelines for petroleum hydrocarbons (PHCs) in soil aid in the mitigation of risks to human health and the environmental. However, some remediation guidelines may overestimate the potential for adverse effects to native plant species, contributing to unnecessary remedial efforts in attempts to meet the guidelines. At sites where PHC-contaminated soils undergo weathering, some PHCs may persist but with decreased bioavailability to organisms. In this study, the toxicity of both coarse and fine-grained subarctic soils, contaminated with weathered PHCs were assessed using five native plant species (Picea mariana, Achillea millefolium, Alnus viridis, Elymus trachycaulus and Salix bebbiana). Soil toxicity tests were conducted in a growth chamber with parameters set to simulate the site's subarctic climate conditions. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results for the PHC-contaminated soils, and also provide new information on the sensitivities of the four boreal species to boric acid. All plants exhibited reduced growth and germination rates as boric acid concentrations increased. Despite exceeding the Canada-wide standard guidelines for Fraction 3 PHCs, field-collected contaminated soils had no significant negative impacts on the growth (i.e., length, dry weight and emergence) of any of the plant species tested.

Complex and flexible catabolism in Aromatoleum aromaticum pCyN1

Large quantities of organic matter are continuously deposited, and (a)biotic gradients intersect in the soil-rhizosphere, where biodegradation contributes to the global cycles of elements. The betaproteobacterial genus Aromatoleum comprises cosmopolitan, facultative denitrifying degradation specialists. A. aromaticum pCyN1 stands out for anaerobically decomposing plant-derived monoterpenes in addition to monoaromatic hydrocarbons, polar aromatics and aliphatics. The catabolic network's structure and flexibility in A. aromaticum pCyN1 was studied across 34 growth conditions by superimposing proteome profiles onto the manually annotated 4.37 Mbp genome. Strain pCyN1 employs three fundamentally different enzymes for C-H-bond cleavage at the methyl groups of p-cymene/4-ethyltoluene, toluene and p-cresol, respectively. Regulation of degradation modules displayed substrate specificities ranging from narrow (toluene and cyclohexane carboxylate) via medium-wide (one module shared by p-cymene, 4-ethyltoluene, α-phellandrene, α-terpinene, γ-terpinene and limonene) to broad (central benzoyl-CoA pathway serving 16 aromatic substrates). Remarkably, three variants of ATP-dependent (class I) benzoyl-CoA reductase and four different β-oxidation routes establish a degradation hub that accommodates the substrate diversity. The respiratory system displayed several conspicuous profiles, e.g., the presence of nitrous oxide reductase under oxic and of low-affinity oxidase under anoxic conditions. Overall, nutritional versatility in conjunction with network regulation endow A. aromaticum pCyN1 with broad adaptability. This article is protected by copyright. All rights reserved.

Valorization of Small Alkanes by Biocatalytic Oxyfunctionalization

The oxidation of alkanes into valuable chemical products is a vital reaction in organic synthesis. This reaction, however, is challenging, owing to the inertness of C-H bonds. Transition metal catalysts for C-H functionalization are frequently explored. Despite chemical alternatives, nature has also evolved powerful oxidative enzymes (e. g., methane monooxygenases, cytochrome P450 oxygenases, peroxygenases) that are capable of transforming C-H bonds under very mild conditions, with only the use of molecular oxygen or hydrogen peroxide as electron acceptors. Although progress in alkane oxidation has been reviewed extensively, little attention has been paid to small alkane oxidation. The latter holds great potential for the manufacture of chemicals. This Minireview provides a concise overview of the most relevant enzyme classes capable of small alkanes (C_<6 ) oxyfunctionalization, describes the essentials of the catalytic mechanisms, and critically outlines the current state-of-the-art in preparative applications.

Chemical Constituents of the Essential oil from Cuminum cyminum L. and Its Antifungal Activity against Panax notoginseng Pathogens

Cuminum cyminum L. (Cumin) is a flavoring agent that is commonly used worldwide, and is rich in essential oil. Essential oils (Eos) have been intensively investigated in regard to their potential for disease control in plants, which is provided a chance for the blossom of green pesticides. The chemical components of Cumin essential oil (CEO) were revealed by GC/MS, such as cuminaldehyde (44.53 %), p-cymene (12.14 %), (-)-β-pinene (10.47 %) and γ-terpinene (8.40 %), and found they can inhibit the growth of P. notoginseng-associated pathogenic fungi in vitro and the inhibitory effect of cuminaldehyde was similar to that of hymexazol. SEM and TEM images demonstrated that cuminaldehyde and CEO increased cell permeability and disrupted membrane integrity. The expression of disease-related genes of Fusarium oxysporum showed that CEO induced the expression of most genes, which disrupted biosynthesis, metabolism and signaling pathways. These studies verified the potential of CEO as a plant fungicide that is environmentally friendly and provided ideas for developing new products for controlling root diseases that affect P. notoginseng.

Biodegradation of p-nitrophenol by engineered strain

p-Nitrophenol (PNP) is an important environmental pollutant and can causes significant environmental and health risks. Compared with the traditional methods, biodegradation is a useful one to completely remove the harmful pollutants from the environment. Here, an engineered strain was first constructed by introducing PNP biodegradation pathway via the hydroquinone (HQ) pathway into Escherichia coli. In the engineered strain BL-PNP, PNP was completely degraded to β-ketoadipate and subsequently enter the metabolites of multiple anabolic pathways. The high tolerance and rapid degradation ability to PNP enable the engineered strain to have the potential to degrade toxic substances. The engineered strain created in this study can be used as a functional strain for bioremediation of PNP and potential toxic intermediates, and the method of assembling aromatic hydrocarbons metabolic pathway can be used to eradicate nitroaromatic pollutants in the environment.

Efficacy and Safety Curcuma zadoaria L. to Inactivate the Hydatid Cyst Protoscoleces

BACKGROUND

The present work aimed to evaluate the chemical composition of Curcuma zadoaria essential oil and to investigate its efficacy and safety against hydatid cyst protoscoleces.

METHODS

Collected protoscoleces from liver fertile hydatid cysts of infected sheep were exposed to different concentrations of the essential oil (75, 150, 300 μl/mL) for 5-30 min in vitro and ex vivo. Then, by using the eosin exclusion assay, the viability of protoscoleces was studied. In the next step, 24 male NMRI mice were examined to assess the toxicity of C. zadoaria essential oil by measuring the biochemical and hematological parameters.

RESULTS

Based on the obtained results, the LD50 value of intraperitoneal injection of the C. zadoaria essential oil was 1.76 mL/kg of body weight and the maximum non-fatal dose was 0.96 mL/kg of body weight. C. zadoaria essential oil had a strong proto scolicidal activity in vitro so that at the 300 and 150 μl/ml entirely eliminates the parasite after 5 and 10 minutes; whereas, weak proto scolicidal activity was observed at lower doses. Ex vivo assay, no similar effect with in vitro was observed, therefore, more time is required to show a potent proto scolicidal activity. C. zadoaria essential oil at the concentrations of 300 and 150 μl/mL after an exposure time of 7 and 12 min, killed 100% of protoscoleces within the hydatid cyst, respectively. After intraperitoneal injection of the C. zadoaria essential oil for 2 weeks, no significant difference (p > 0.05) was observed in the clinical chemistry and hematologic parameters at the doses of 0.15, 0.3, 0.6 mL/kg.

CONCLUSION

The obtained results in vitro and ex vivo exhibited that C. zadoaria essential oil had a favorable proto scolicidal activity on hydatid cyst protoscoleces. However, more supplementary works are required to verify these findings by assessing clinical subjects.

Development of antifungal biopolymers based on dynamic imines as responsive release systems for the postharvest preservation of blackberry fruit

This study describes the synthesis and reversibility of Schiff bases from chitosan and bioactive compounds, and their application in the antifungal packaging of fruit. Imine bonds between primary amine groups of chitosan and carbonyl groups of antifungal aldehydes were synthesised and their reversibility was assayed in an aqueous medium under different acidic conditions. The mechanism of action of the dynamers is based on the hydrolysis of imine bond and the release of the active agent. The new films were effective at inhibiting the growth of Penicillium expansum and Botrytis cinerea, and their effectivity depended on the degree of hydrolysis achieved which was greater when the bonds were hydrolysed in a mild acidic medium. A double bottom cylindrical tray was used for the responsive antimicrobial packaging of blackberries. The package extended shelf-life of berries from 3 to 12 days without causing phytotoxic effects on the fruit being safe for human consumption.

Biological nitrification inhibition in the rhizosphere: determining interactions and impact on microbially mediated processes and potential applications

Nitrification is the microbial conversion of reduced forms of nitrogen (N) to nitrate (NO3-), and in fertilized soils it can lead to substantial N losses via NO3- leaching or nitrous oxide (N2O) production. To limit such problems, synthetic nitrification inhibitors have been applied but their performance differs between soils. In recent years, there has been an increasing interest in the occurrence of biological nitrification inhibition (BNI), a natural phenomenon according to which certain plants can inhibit nitrification through the release of active compounds in root exudates. Here, we synthesize the current state of research but also unravel knowledge gaps in the field. The nitrification process is discussed considering recent discoveries in genomics, biochemistry and ecology of nitrifiers. Secondly, we focus on the 'where' and 'how' of BNI. The N transformations and their interconnections as they occur in, and are affected by, the rhizosphere, are also discussed. The NH4+ and NO3- retention pathways alternative to BNI are reviewed as well. We also provide hypotheses on how plant compounds with putative BNI ability can reach their targets inside the cell and inhibit ammonia oxidation. Finally, we discuss a set of techniques that can be successfully applied to solve unresearched questions in BNI studies.

Response of soil bacterial communities to high petroleum content in the absence of remediation procedures

Oil spills are events that frequently lead to petroleum pollution. This pollution may cause stress to microbial communities, which require long adaption periods. Soil petroleum pollution is currently considered one of the most serious environmental problems. In the present work, processes occurring in the bacterial communities of three soil samples with different physicochemical characteristics, artificially polluted with 12% of crude oil, were investigated in 120-day laboratory experiment. It was found that the total petroleum hydrocarbon content did not decrease during this time; however, the proportion of petroleum fractions was altered. Petroleum pollution led to a short-term decrease in the bacterial 16S rRNA gene copy number. On the basis of amplicon sequencing analysis, it was concluded that bacterial community successions were similar in the three soils investigated. Thus, the phyla Actinobacteria and Proteobacteria and candidate TM7 phylum (Saccaribacteria) were predominant with relative abundances ranging from 35 to 58%, 25 to 30%, and 15 to 35% in different samples, respectively. The predominant operational taxonomic units (OTUs) after pollution belonged to the genera Rhodococcus and Mycobacterium, families Nocardioidaceae and Sinobacteraceae, and candidate class ТМ7-3. Genes from the alkIII group encoding monoxygenases were the most abundant compared with other catabolic genes from the alkI, alkII, GN-PAH, and GP-PAH groups, and their copy number significantly increased after pollution. The copy numbers of expressed genes involved in the horizontal transfer of catabolic genes, FlgC, TraG, and OmpF, also increased after pollution by 11-33, 16-63, and 11-71 times, respectively. The bacterial community structure after a high level of petroleum pollution changed because of proliferation of the cells that initially were able to decompose hydrocarbons, and in the second place, because proliferation of the cells that received these catabolic genes through horizontal transfer.

Complete Genomes of the Anaerobic Degradation Specialists Aromatoleum petrolei ToN1T and Aromatoleum bremense PbN1T

The betaproteobacterial genus Aromatoleum comprises facultative denitrifiers specialized in the anaerobic degradation of recalcitrant organic compounds (aromatic and terpenoid). This study reports on the complete and manually annotated genomes of Ar. petrolei ToN1T (5.41 Mbp) and Ar. bremense PbN1T (4.38 Mbp), which cover the phylogenetic breadth of the genus Aromatoleum together with previously genome sequenced Ar. aromaticum EbN1T [Rabus et al., Arch Microbiol. 2005 Jan;183(1):27-36]. The gene clusters for the anaerobic degradation of aromatic and terpenoid (strain ToN1T only) compounds are scattered across the genomes of strains ToN1T and PbN1T. The richness in mobile genetic elements is shared with other Aromatoleum spp., substantiating that horizontal gene transfer should have been a major driver in shaping the genomes of this genus. The composite catabolic network of strains ToN1T and PbN1T comprises 88 proteins, the coding genes of which occupy 86.1 and 76.4 kbp (1.59 and 1.75%) of the respective genome. The strain-specific gene clusters for anaerobic degradation of ethyl-/propylbenzene (strain PbN1T) and toluene/monoterpenes (strain ToN1T) share high similarity with their counterparts in Ar. aromaticum strains EbN1T and pCyN1, respectively. Glucose is degraded via the ED-pathway in strain ToN1T, while gluconeogenesis proceeds via the reverse EMP-pathway in strains ToN1T, PbN1T, and EbN1T. The diazotrophic, endophytic lifestyle of closest related genus Azoarcus is known to be associated with nitrogenase and type-6 secretion system (T6SS). By contrast, strains ToN1T, PbN1T, and EbN1T lack nif genes for nitrogenase (including cofactor synthesis and enzyme maturation). Moreover, strains PbN1T and EbN1T do not possess tss genes for T6SS, while strain ToN1T does and facultative endophytic "Aromatoleum" sp. CIB is known to even have both. These findings underpin the functional heterogeneity among Aromatoleum members, correlating with the high plasticity of their genomes.

Essential Oils as Alternative Biocides for the Preservation of Waterlogged Archaeological Wood

Waterlogged archaeological wood is exposed to a high risk of biological degradation during the post-excavation phases of storage and restoration. For this reason, often biocides must be used to preserve wooden remains. In the present work three essential oils (cinnamon, wild thyme, and common thyme) were tested as possible alternative biocides to use in the preservation of waterlogged archaeological wood. The oils were first tested in vitro to establish the minimum inhibitory concentration (MIC) and to evaluate the biocidal activity on selected fungal strains. Then, the established MIC was applied on waterlogged archaeological wood samples and during an actual restoration treatment. The effectiveness of the oils was evaluated through cultural analyses, ATP quantification, and next-generation sequencing. The results showed that the oils caused a significant decrease in the vitality of fungal mycelia grown in vitro and of the microbiota present in treated wood and storage water. Furthermore, an influence on the composition of the bacterial communities of treated wood samples was observed. Although further tests are needed to evaluate interferences with the materials used during restoration procedures, essential oils could be considered as a possible alternative to the currently used biocide.

Deeper below the surface-transcriptional changes in selected genes of Clostridium beijerinckii in response to butanol shock

The main bottleneck in the return of industrial butanol production from renewable feedstock through acetone–butanol–ethanol (ABE) fermentation by clostridia, such as Clostridium beijerinckii, is the low final butanol concentration. The problem is caused by the high toxicity of butanol to the production cells, and therefore, understanding the mechanisms by which clostridia react to butanol shock is of key importance. Detailed analyses of transcriptome data that were obtained after butanol shock and their comparison with data from standard ABE fermentation have resulted in new findings, while confirmed expected population responses. Although butanol shock resulted in upregulation of heat shock protein genes, their regulation is different than was assumed based on standard ABE fermentation transcriptome data. While glucose uptake, glycolysis, and acidogenesis genes were downregulated after butanol shock, solventogenesis genes were upregulated. Cyclopropanation of fatty acids and formation of plasmalogens seem to be significant processes involved in cell membrane stabilization in the presence of butanol. Surprisingly, one of the three identified Agr quorum‐sensing system genes was upregulated. Upregulation of several putative butanol efflux pumps was described after butanol addition and a large putative polyketide gene cluster was found, the transcription of which seemed to depend on the concentration of butanol.

The Promising Role of Antioxidant Phytochemicals in the Prevention and Treatment of Periodontal Disease via the Inhibition of Oxidative Stress Pathways: Updated Insights

There is growing evidence on the involvement of oxidative stress, which is simply described as the imbalance between oxidants and antioxidants in favor of the former, in the development of periodontal disease that is the most common inflammatory disease in the oral cavity. Thus, the potential of antioxidant phytochemicals as adjunctively preventive and therapeutic agents against the initiation and progression of periodontal disease is a topic of great interest. The current review firstly aims to provide updated insights about the immuno-inflammatory pathway regulated by oxidative stress in periodontal pathology. Then, this work further presents the systemic knowledge of antioxidant phytochemicals, particularly the pharmacological activities, which can be utilized in the prevention and treatment of periodontal disease. Additionally, the challenges and future prospects regarding such a scope are figured out.

Potential Application of Essential Oils for Mitigation of Listeria monocytogenes in Meat and Poultry Products

One of the most important challenges in the food industry is to provide healthy and safe food. Therefore, it is not possible to achieve this without different processes and the use of various additives. In order to improve safety and extend the shelf life of food products, various synthetic preservatives have been widely utilized by the food industry to prevent growth of spoilage and pathogenic microorganisms. On the other hand, consumers' preference to consume food products with natural additives induced food industries to use natural-based preservatives in their production. It has been observed that herbal extracts and their essential oils could be potentially considered as a replacement for chemical antimicrobials. Antimicrobial properties of plant essential oils are derived from some main bioactive components such as phenolic acids, terpenes, aldehydes, and flavonoids that are present in essential oils. Various mechanisms such as changing the fatty acid profile and structure of cell membranes and increasing the cell permeability as well as affecting membrane proteins and inhibition of functional properties of the cell wall are effective in antimicrobial activity of essential oils. Therefore, our objective is to revise the effect of various essential oils and their bioactive components against Listeria monocytogenes in meat and poultry products.

Proteomic Characterization of the Pseudomonas sp. Strain phDV1 Response to Monocyclic Aromatic Compounds

The degradation of aromatic compounds comprises an important step in the removal of pollutants and re-utilization of plastics and other non-biological polymers. Here, Pseudomonas sp. strain phDV1, a gram-negative bacterium that is selected for its ability to degrade aromatic compounds is studied. In order to understand how the aromatic compounds and their degradation products are reintroduced in the metabolism of the bacteria and the systematic/metabolic response of the bacterium to the new carbon source, the proteome of this strain is analyzed in the presence of succinate, phenol, and o-, m-, and p-cresol as the sole carbon source. As a reference proteome, the bacteria are grown in succinate and then compared with the respective proteomes of bacteria grown on phenol and different cresols. In total, 2295 proteins are identified; 1908 proteins are used for quantification between different growth conditions. The carbon source affects the synthesis of enzymes related to aromatic compound degradation and in particular the enzyme involved in the meta-pathway of monocyclic aromatic compounds degradation. In addition, proteins involved in the production of polyhydroxyalkanoate (PHA), an attractive biomaterial, show higher abundance in the presence of monocyclic aromatic compounds. The results provide, for the first time, comprehensive information on the proteome response of this strain to monocyclic aromatic compounds.

Dioxin impacts on lipid metabolism of soil microbes: towards effective detection and bioassessment strategies

Dioxins are the most toxic known environmental pollutants and are mainly formed by human activities. Due to their structural stability, dioxins persist for extended periods and can be transported over long distances from their emission sources. Thus, dioxins can be accumulated to considerable levels in both human and animal food chains. Along with sediments, soils are considered the most important reservoirs of dioxins. Soil microorganisms are therefore highly exposed to dioxins, leading to a range of biological responses that can impact the diversity, genetics and functional of such microbial communities. Dioxins are very hydrophobic with a high affinity to lipidic macromolecules in exposed organisms, including microbes. This review summarizes the genetic, molecular and biochemical impacts of dioxins on the lipid metabolism of soil microbial communities and especially examines modifications in the composition and architecture of cell membranes. This will provide a useful scientific benchmark for future attempts at soil ecological risk assessment, as well as in identifying potential dioxin-specific-responsive lipid biomarkers. Finally, potential uses of lipid-sequestering microorganisms as a part of biotechnological approaches to the bio-management of environmental contamination with dioxins are discussed.

A Novel Butanol Tolerance-Promoting Function of the Transcription Factor Rob in Escherichia coli

Producing high concentrations of biobutanol is challenging, primarily because of the toxicity of butanol toward cells. In our previous study, several butanol tolerance-promoting genes were identified from butanol-tolerant Escherichia coli mutants and inactivation of the transcriptional regulator factor Rob was shown to improve butanol tolerance. Here, the butanol tolerance characteristics and mechanism regulated by inactivated Rob are investigated. Comparative transcriptome analysis of strain DTrob, with a truncated rob in the genome, and the control BW25113 revealed 285 differentially expressed genes (DEGs) to be associated with butanol tolerance and categorized as having transport, localization, and oxidoreductase activities. Expression of 25 DEGs representing different functional categories was analyzed by quantitative reverse transcription PCR (qRT-PCR) to assess the reliability of the RNA-Seq data, and 92% of the genes showed the same expression trend. Based on functional complementation experiments of key DEGs, deletions of glgS and yibT increased the butanol tolerance of E. coli, whereas overexpression of fadB resulted in increased cell density and a slight increase in butanol tolerance. A metabolic network analysis of these DEGs revealed that six genes (fadA, fadB, fadD, fadL, poxB, and acs) associated with acetyl-CoA production were significantly upregulated in DTrob, suggesting that Rob inactivation might enhance butanol tolerance by increasing acetyl-CoA. Interestingly, DTrob produced more acetate in response to butanol stress than the wild-type strain, resulting in the upregulation expression of some genes involved in acetate metabolism. Altogether, the results of this study reveal the mechanism underlying increased butanol tolerance in E. coli regulated by Rob inactivation.

Antibacterial Activity of Endostemon tereticaulis (Poir.) M. Ashby Essential Oil and Ethanolic Extract Against Resistant Pathogenic Bacteria

Endostemon tereticaulis (poir.) M.Ashby is a species of the Lamiaceae family present in Niger. This plant is used in traditional medicine due to its various biological potentialities. The present study investigated the chemical composition of the essential oil and the antibacterial activity of the essential oil and ethanolic extract of Endostemon tereticaulis against resistant pathogenic bacteria. Gas chromatography-mass spectrometry analysis of the essential oil led to the identification of 43 compounds representing 99.55% of the total essential oil. The major components were caryophyllene oxide (15.17%) followed by α-humulene (13.96%), α-copaene (11.75%), ( E)-β-caryophyllene (8.44%), and δ-cadinene (6.78%). The antibacterial activity was tested against multiresistant Acinetobacter baumannii P1483, Salmonella spp. H1548, extended-spectrum β-lactamase- Escherichia coli Bu8566, Enterobacter cloacae Bu147, Proteus mirabilis Bu190 , Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (ATCC 700603), Escherichia coli (ATCC 25922), Enterococcus faecium H3434, methicillin-resistant Staphylococcus aureus P1123, and Staphylococcus aureus (ATCC 25923). The antibacterial assays revealed that the essential oil was more active than the ethanolic extract against the studied bacteria with minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values ranging from 0.06 to 2 mg/mL. Also, the ethanolic extract was effective against the bacteria tested with MIC and MBC values ranging from 0.12 to 3 mg/mL. This study showed that Endostemon tereticaulis essential oil is rich in bioactive compounds. Ethanolic extract and essential oil exhibited potential antibacterial activity. These results provide a scientific basis for the use of this plant in traditional medicine. The current study described for the first time the antibacterial activity of Endostemon tereticaulis.

A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL⁻¹. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL⁻¹ biopolymer concentration affording complete killing of the bacterial cells. Insights into the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance since citrus IntegroPectin biomaterials are also devoid of cytotoxic activity, as already shown for lemon IntegroPectin, opening the route to the development of new medical treatments of polymicrobial infections unlikely to develop drug resistance.

Microbial community responses to different volatile petroleum hydrocarbon class mixtures in an aerobic sandy soil

Volatile Petroleum Hydrocarbon (VPH) class effects on soil microbial composition were investigated using two next-generation sequencing (NGS) techniques - 454 pyrosequencing and ion torrent sequencing. Microbial activity was stimulated by adding different VPH compound classes to the sandy soil in comparison with live controls without VPH addition. Microbial community structure was significantly affected by the various VPH classes. At the genus level, Rhodococcus, Desulfosporosinus, Polaromonas, Mesorhizobium and Methylibium had the highest relative abundances in the straight-chain alkane (str-alk) treated soil as compared to the control (p < 0.05, 2 sample t-tests) while Pseudomonas was more dominant in the cyclic alkane (cyc-alk) contaminated soil. Pseudonocardia was significantly higher in relative abundance in the aromatic hydrocarbon (aro-H) treated batches as compared to the control (p < 0.05, 2 sample t-tests). A non-metric multidimensional scaling (NMDS) of the Bray Curtis similarity between microbial communities in the batches revealed at least 60% similarity for each treatment and also showed that VPH class was a statistically significant factor in shaping the bacterial communities in the soil treatments (Global R = 0.861, p < 0.01). The NGS platforms (454 GS Junior and Ion torrent) compared in this study did not appear to affect the outcomes of the microbial community structure and composition analysis.

Bacterial growth and biological properties of Cymbopogon schoenanthus and Ziziphus lotus are modulated by extraction conditions

The present study aims to evaluate the antibacterial activity and biological properties of two traditional Saharian plants (Cymbopogon schoenanthus and Ziziphus lotus). The plant extracts were obtained by using a different combination of extraction methods (conventional vs. ultrasound-assisted) and solvents (water vs. ethanol:water (50:50, v/v)). The antioxidant profile, anti-inflammatory activity and impact on bacterial growth (foodborne and probiotic bacteria) of the obtained extracts were assessed. The plant species showed the hierarchically more important role in determining the biological properties of the extracts, followed by extraction solvent and extraction conditions. Conventional Z. lotus hydroethanolic extracts showed the highest total phenolic content (20.4 mg GAE/g), while Z. lotus ethanol extracts from ultrasound-assisted process presented the highest content of carotenoids (0.15 mg/g). In addition, ultrasound-assisted Z. lotus hydroethanolic extracts presented the highest in vitro radical scavenging activity, being 7.93 mmol Trolox/g. Multivariate analysis statistics (PCA) showed that both the extraction methodology and the solvent used strongly affected the bacterial growth. Z. lotus mainly decreased the growth rate of S. aureus and L. innocua. Interestingly, the aqueous extracts of this plant as well as those from C. schoenanthus, obtained by conventional extraction, significantly increased the growth rate and the maximal optical density of L. casei. Aqueous extracts of both Z. lotus and C. schoenanthus slightly influenced the growth of Bifidobacterium. Overall, the extracts of these plants showed selective activities with respect to pathogens and probiotic bacteria and may provide an advantage both in terms of antimicrobial and prebiotic activity.

The Effects of Halogenated Compounds on the Anaerobic Digestion of Macroalgae

The urgent need to replace fossil fuels has seen macroalgae advancing as a potential feedstock for anaerobic digestion. The natural methane productivity (dry weight per hectare) of seaweeds is greater than in many terrestrial plant systems. As part of their defence systems, seaweeds, unlike terrestrial plants, produce a range of halogenated secondary metabolites, especially chlorinated and brominated compounds. Some orders of brown seaweeds also accumulate iodine, up to 1.2% of their dry weight. Fluorine remains rather unusual within the chemical structure. Halogenated hydrocarbons have moderate to high toxicities. In addition, halogenated organic compounds constitute a large group of environmental chemicals due to their extensive use in industry and agriculture. In recent years, concerns over the environmental fate and release of these halogenated organic compounds have resulted in research into their biodegradation and the evidence emerging shows that many of these compounds are more easily degraded under strictly anaerobic conditions compared to aerobic biodegradation. Biosorption via seaweed has become an alternative to the existing technologies in removing these pollutants. Halogenated compounds are known inhibitors of methane production from ruminants and humanmade anaerobic digesters. The focus of this paper is reviewing the available information on the effects of halogenated organic compounds on anaerobic digestion.

Saturated Fatty Acid-Based In Situ Forming Matrices for Localized Antimicrobial Delivery

In recent years, the world has faced the issue of antibiotic resistance. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant problem in various treatments and control of infections. Biocompatible materials with saturated fatty acids of different chain lengths (C₈-C₁₈) were studied as matrix formers of localized injectable vancomycin HCl (VCM)-loaded antisolvent-induced in situ forming matrices. The series of fatty acid-based in situ forming matrices showed a low viscosity (5.47-13.97 cPs) and pH value in the range of 5.16-6.78, with high injectability through a 27-G needle (1.55-3.12 N). The preparations exhibited low tolerance to high concentrations of KH₂PO₄ solution (1.88-5.42% v/v) and depicted an electrical potential change during phase transformation. Their phase transition and matrix formation at the microscopic and macroscopic levels depended on the chain length of fatty acids and solvent characteristics. The VCM release pattern depended on the nucleation/crystallization and solvent exchange behaviors of the delivery system. The 35% w/v of C₁₂-C₁₆ fatty acid-based in situ forming matrix prolonged the VCM release over seven days in which C₁₂, C₁₄, C₁₆ -based formulation reached 56, 84, and 85% cumulative drug release at 7^th day. The release data fitted well with Higuchi's model. The developed formulations presented efficient antimicrobial activities against standard S. aureus, MRSA, Escherichia coli, and Candida albicans. Hence, VCM-loaded antisolvent-induced fatty acid-based in situ forming matrix is a potential local delivery system for the treatment of local Gram-positive infection sites, such as joints, eyes, dermis of surgery sites, etc., in the future.

Membrane Stability in the Presence of Methacrylate Esters

Bioproduction of poly(methyl methacrylate) is a fast growing global industry that is limited by cellular toxicity of monomeric methacrylate intermediates to the producer strains. Maintaining high methacrylate concentrations during biofermentation, required by economically viable technologies, challenges bacterial membrane stability and cellular viability. Studying the stability of model lipid membranes in the presence of methacrylates offers unique molecular insights into the mechanisms of methacrylate toxicity, as well as into the fundamental structural bases of membrane assembly. We investigate the structure and stability of model membranes in the presence of high levels of methacrylate esters using solid-state nuclear magnetic resonance (NMR) and small-angle X-ray scattering (SAXS). Wide-line ³¹P NMR spectroscopy shows that butyl methacrylate (BMA) can be incorporated into the lipid bilayer at concentrations as high as 75 mol % without significantly disrupting membrane integrity and that lipid acyl chain composition can influence membrane tolerance and ability to accommodate BMA. Using high resolution ¹³C magic angle spinning (MAS) NMR, we show that the presence of 75 mol % BMA lowers the lipid main transition temperature by over 12 degrees, which suggests that BMA intercalates between the lipid chains, causing uncoupling of collective lipid motions that are typically dominated by chain trans-gauche isomerization. Potential uncoupling of the bilayer leaflets to accommodate a separate BMA subphase was not supported by the SAXS experiments, which showed that membrane thickness remained unchanged even at 80% BMA. Reduced X-ray scattering contrast at the polar/apolar interface suggests BMA localization in that region between the lipid molecules.

Preparation and Characterization of Antibacterial Porcine Acellular Dermal Matrices with High Performance

Infection is a common complication in the process of wound management. An ideal wound dressing is supposed to reduce or even prevent the infection while promoting wound healing. A porcine acellular dermal matrix (pADM) has been already used as a wound dressing in clinic due to its capacity to accelerate wound healing. However, not only is pure pADM not antibacterial, its mechanical properties are poor. In this study, an antibacterial pADM with good performance was prepared by adding two natural products as modifiers, quercetin (QCT) and tea tree oil (TTO). The result of Fourier-transform infrared (FTIR) proved that the addition of modifiers did not break the natural triple-helical structure of collagen. Meanwhile, the results of differential scanning calorimetry (DSC), thermogravimetric analysis (TG), mechanic experiment, and enzymatic degradation demonstrated that pADM handled with QCT and TTO (termed QCT-TTO-pADM) had better thermal stability, mechanical strength, and resistance to enzymatic degradation than pADM. Meanwhile, QCT-TTO-pADM had excellent antibacterial activity and showed an antibacterial rate of over 80%. Furthermore, in the cytocompatibility analysis, QCT-TTO-pADM had no side effects on the adhesion, growth, and proliferation of fibroblasts. QCT-TTO-pADM could even accelerate wound healing more efficiently than pADM and glutaraldehyde-modified pADM (GA-pADM). In conclusion, QCT-TTO-pADM was a potential antibacterial wound dressing with good performance.

Cinnamaldehyde is a biologically active compound for the disinfection of removable denture: blinded randomized crossover clinical study

BACKGROUND

Fungal infections associated with the use of dentures, like denture stomatitis, are difficult to prevent and treat. This in situ study aimed to investigate the efficacy of cinnamaldehyde for the disinfection of complete removable dentures, and the effect on the physical and mechanical properties (Vickers microhardness, color, and surface roughness) of the acrylic resin.

METHODS

Acrylic resin disks were inserted into the dentures of a probabilistic sample of 33 complete denture users, that used cinnamaldehyde (27 μg/mL) and 0.5% sodium hypochlorite solutions in a 20 min/7-days protocol of dentures immersion in each solution, with a wash-out period of 7 days, to constitute a crossover-study. The disks were analyzed before and after the immersion, for the presence of microorganisms (CFU/mL) and by scanning electron microscope (SEM). Also, the surface roughness (Ra) and Vickers microhardness were measured, and color parameters were analyzed using the National Bureau of Standards (NBS) method. Data was analyzed by Wilcoxon and Friedman (microbiological evaluation), paired t-test (color and roughness) and independent t-test (Vickers hardness) (α = 0.05).

RESULTS

A significant reduction (P < 0.05) in the number of microorganisms was observed for each species (total microorganisms, Streptococcus mutans, and Candida spp.), with no significant differences (P > 0.05) between hypochlorite and cinnamaldehyde. There was an increase in the roughness and a decrease in the hardness of the test specimens, with no difference between the two disinfectant substances (P > 0.05). Both hypochlorite and cinnamaldehyde also caused changes in color, considered as "perceptible" by the NBS classification, but with no significant difference between disinfectant substances (P < 0.05), and under the clinically acceptable limit (ΔE ≤ 3.7).

CONCLUSION

The 27 μg/mL cinnamaldehyde solution was effective against all evaluated microorganisms and caused minor alterations in hardness, surface roughness, and color parameters, with no clinical relevance.

Multilevel changes in bacterial properties on long-term exposure to hydrocarbons and impact of these cells on fresh-water communities

To handle the impact of habitat transformations, the microbial cells developed mechanisms aimed at adjustment of their biological processes in response to signals indicating environmental changes. One of the first changes in their properties is observed on their surface, which has direct contact with the dynamically varying surroundings. In this study, we present results of changes in the cell surface properties which may have a decisive impact on the xenobiotics' bioavailability and microbial cell survival. These changes influence their ability to remove xenobiotics by accelerating and empowering this process. Moreover, the application of microorganisms exposed for long-term to hydrocarbons in bioremediation processes might have positive impact on biodegradation of the latter in the natural environment as well as natural microbial community diversity. This study demonstrates a variety of microbial cell mechanisms of adaptation to long-term exposure to hydrocarbons and their potential as the bioremediation tools.

Octylphenol facilitates fermentative volatile fatty acids recovery from waste activated sludge

The presence of endocrine disruptor compounds (EDCs) in wastewater treatment plants has attracted widespread attention, but their potential impact on anaerobic fermentation of waste activated sludge (WAS) remains unclear. Therefore, this study aims to reveal the effect of typical EDC octylphenol (OP) on the recovery of volatile fatty acids (VFAs) in anaerobic fermentation. The results show that OP has a positive effect on the recovery of VFAs from WAS. The presence of 200 mg/kg dry sludge of OP increased the cumulative amount of VFAs from 3245 in the control (without OP) to 6828 mg COD/L. The increase in VFA production was mainly attributed to the accumulation of acetic acid, which rose from 1511 to 4425 mg COD/L, almost tripled. Further research found that OP promoted solubilization and hydrolysis by improving the biodegradability of WAS, and severely inhibited the methanogenesis process by inhibiting the activity of coenzyme F420, thereby significantly increasing the accumulation of acetic acid. These findings are of great significance to clarify the role of OP in anaerobic fermentation, and provide theoretical basis and guidance for the selection of target products in anaerobic fermentation of WAS containing OP.

Vaginitis: Review on Drug Resistance

Female genital tract infections have a high incidence among different age groups and represent an important impact on public health. Among them, vaginitis refers to inflammation of the vulva and/or vagina due to the presence of pathogens that cause trichomoniasis, bacterial vaginosis, and vulvovaginal candidiasis. Several discomforts are associated with these infections, as well as pregnancy complications and the facilitation of HIV transmission and acquisition. The increasing resistance of microorganisms to drugs used in therapy is remarkable, since women report the recurrence of these infections and associated comorbidities. Different resistant mechanisms already described for the drugs used in the therapy against Trichomonas vaginalis, Candida spp., and Gardnerella vaginalis, as well as aspects related to pathogenesis and treatment, are discussed in this review. This study aims to contribute to drug design, avoiding therapy ineffectiveness due to drug resistance. Effective alternative therapies to treat vaginitis will reduce the recurrence of infections and, consequently, the high costs generated in the health system, improving women's well-being.

In vitro and in silico inhibitory effects of synthetic and natural eugenol derivatives against the NorA efflux pump in Staphylococcus aureus

Staphylococcus aureus is a Gram-positive bacterium responsible for a number of diseases and has demonstrated resistance to conventional antibiotics. This study aimed to evaluate the antibacterial activity of eugenol and its derivatives allylbenzene, 4-allylanisole, isoeugenol and 4-allyl-2,6-dimethoxyphenol against the S. aureus NorA efflux pump (EP) in association with norfloxacin and ethidium bromide. The antibacterial activity of the compounds was assessed using the broth microdilution method to determine the minimum inhibitory concentration (MIC). A reduction in the MIC of ethidium bromide (a substrate for several efflux pumps) or norfloxacin was used as a parameter of EP inhibition. Molecular modeling studies were used to predict the 3D structure and analyze the interaction of selected compounds with the binding pocket of the NorA efflux pump. Except for 4-allylanisole and allylbenzene, the compounds presented clinically effective antibacterial activity. When associated with norfloxacin against the SA 1199B strain, 4-allyl-2,6-dimethoxyphenol eugenol and isoeugenol caused significant reduction in the MIC of the antibiotic, demonstrating synergistic effects. Similar effects were observed when 4-allyl-2,6-dimethoxyphenol, allylbenzene and isoeugenol were associated with ethidium bromide. Together, these findings indicate a potential inhibition of the NorA pump by eugenol and its derivatives. This in vitro evidence was corroborated by docking results demonstrating favorable interactions between 4-allyl-2,6-dimetoxypheno and the NorA pump mediated by hydrogen bonds and hydrophobic interactions. In conclusion, eugenol derivatives have the potential to be used in antibacterial drug development in strains carrying the NorA efflux pump.

Redox-Active Polymers Connecting Living Microbial Cells to an Extracellular Electrical Circuit

Microbial electrochemical systems in which metabolic electrons in living microbes have been extracted to or injected from an extracellular electrical circuit have attracted considerable attention as environmentally-friendly energy conversion systems. Since general microbes cannot exchange electrons with extracellular solids, electron mediators are needed to connect living cells to an extracellular electrode. Although hydrophobic small molecules that can penetrate cell membranes are commonly used as electron mediators, they cannot be dissolved at high concentrations in aqueous media. The use of hydrophobic mediators in combination with small hydrophilic redox molecules can substantially increase the efficiency of the extracellular electron transfer process, but this method has side effects, in some cases, such as cytotoxicity and environmental pollution. In this Review, recently-developed redox-active polymers are highlighted as a new type of electron mediator that has less cytotoxicity than many conventional electron mediators. Owing to the design flexibility of polymer structures, important parameters that affect electron transport properties, such as redox potential, the balance of hydrophobicity and hydrophilicity, and electron conductivity, can be systematically regulated.

In vitro Anticoccidial Study of Oregano and Garlic Essential Oils and Effects on Growth Performance, Fecal Oocyst Output, and Intestinal Microbiota in vivo

This study investigated the in vitro effects of Greek oregano and garlic essential oils on inhibition of Eimeria parasites and their in vivo effects on production performance, intestinal bacteria counts, and oocyst output. An inhibition assay was performed in vitro using Eimeria tenella Wisconsin strain sporozoites and Madin-Darby bovine kidney (MDBK) cells. Intracellular sporozoite invasion was quantified by detection of E. tenella DNA using qPCR from cell monolayers harvested at 2 and 24 h post-infection. Parasite invasion was inhibited by the oregano essential oil at the concentration of 100 μg/ml by 83 or 93% after 2 or 24 h, respectively. Garlic essential oil reached a maximum inhibition of 70% after 24 h with the 50 μg/ml concentration. Normal morphology was observed in MDBK cells exposed to concentrations of 100 μl/ml of garlic or oregano for over 24 h. In the in vivo trial, 180 male broiler chicks (45.3 ± 0.7 g) were allocated into two treatments (6 pens of 15 chicks per treatment). Control treatment was fed commercial diets without antibiotics or anticoccidials. The ORE-GAR treatment was fed the same control diets, further supplemented with a premix (1 g/kg feed) containing the oregano (50 g/kg premix) and garlic (5 g/kg premix) essential oils. At day 37, all birds were slaughtered under commercial conditions, and intestinal samples were collected. ORE-GAR treatment had improved final body weight (1833.9 vs. 1.685.9 g; p < 0.01), improved feed conversion ratio (1.489 vs. 1.569; p < 0.01), and reduced fecal oocyst excretion (day 28: 3.672 vs. 3.989 log oocysts/g, p < 0.01; day 37: 3.475 vs. 4.007 log oocysts/g, p < 0.001). In the caecal digesta, ORE-GAR treatment had lower total anaerobe counts (8.216 vs. 8.824 CFU/g; p < 0.01), whereas in the jejunum digesta the ORE-GAR treatment had higher counts of E. coli (5.030 vs. 3.530 CFU/g; p = 0.01) and Enterobacteriaceae (5.341 vs. 3.829 CFU/g; p < 0.01), and lower counts of Clostridium perfringens (2.555 vs. 2.882 CFU/g; p < 0.01). In conclusion, the combined supplementation of oregano and garlic essential oils had a potent anticoccidial effect in vitro and a growth-promoting effect in broilers reared in the absence of anticoccidial drugs.

Antiproliferative Effect and Cell Cycle Alterations Induced by Salvia officinalis Essential Oil and Its Three Main Components in Human Colon Cancer Cell Lines

Colon cancer is one of the most common human malignancies, and chemotherapy cannot yet prevent recurrence in all patients. Essential oils are phytocomplexes with antiproliferative properties. In this study, we elucidated the antiproliferative properties and the effect on cell cycle progression of Sicilian Salvia officinalis essential oil and its three main compounds, α-thujone, 1,8-cineole (eucalyptol) and camphor, on three human colon cancer cell lines. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography. Cell proliferation was evaluated by MTT assay, and the cell cycle distribution was determined by flow cytometry. Thirty-four compounds were identified in the tested essential oil. Growth inhibition was observed after 72 h, with an impact on cell cycle progression and no effect on the viability of normal colonic epithelial cells. The study shows that S. officinalis essential oil and its three main components have an in vitro antiproliferative effect on colon cancer cells.

Specific localisation of ions in bacterial membranes unravels physical mechanism of effective bacteria killing by sanitiser

Antimicrobial resistance is a major threat to public health. Although many commercial sanitisers contain a combination of cationic surfactants and aromatic alcohols, the physical mechanisms where these two substances bind to or how they disturb bacterial membranes are still largely unknown. In this study, we designed a well-defined model of Gram-negative bacteria surfaces based on the monolayer of lipopolysaccharides with uniform saccharide head groups. Since commonly used X-ray reflectivity is sensitive to changes in the thickness, roughness and electron density but is not sensitive to elements, we employed grazing incidence X-ray fluorescence. In the absence of Ca²⁺, cationic surfactants can penetrate into the membrane core with no extra support by disturbing the layer of K⁺ coupled to negatively charged saccharide head group at z = 17 Å from the air/chain interface. On the other hand, Ca²⁺ confined at z = 19 Å crosslink charged saccharides and prevent the incorporation of cationic surfactants. We found that the addition of nonlethal aromatic alcohols facilitate the incorporation of cationic surfactants by the significant roughening of the chain/saccharide interface. Combination of precise localisation of ions and molecular-level structural analysis quantitatively demonstrated the synegtestic interplay of ingredients to achieve a high antibacterial activity.

Anti-Candida Activity of Essential Oils from Lamiaceae Plants from the Mediterranean Area and the Middle East

Extensive documentation is available on plant essential oils as a potential source of antimicrobials, including natural drugs against Candida spp. Yeasts of the genus Candida are responsible for various clinical manifestations, from mucocutaneous overgrowth to bloodstream infections, whose incidence and mortality rates are increasing because of the expanding population of immunocompromised patients. In the last decade, although C. albicans is still regarded as the most common species, epidemiological data reveal that the global distribution of Candida spp. has changed, and non-albicans species of Candida are being increasingly isolated worldwide. The present study aimed to review the anti-Candida activity of essential oils collected from 100 species of the Lamiaceae family growing in the Mediterranean area and the Middle East. An overview is given on the most promising essential oils and constituents inhibiting Candida spp. growth, with a particular focus for those natural products able to reduce the expression of virulence factors, such as yeast-hyphal transition and biofilm formation. Based on current knowledge on members of the Lamiaceae family, future recommendations to strengthen the value of these essential oils as antimicrobial agents include pathogen selection, with an extension towards the new emerging Candida spp. and toxicological screening, as it cannot be taken for granted that plant-derived products are void of potential toxic and/or carcinogenic properties.

Common Plant-Derived Terpenoids Present Increased Anti-Biofilm Potential against Staphylococcus Bacteria Compared to a Quaternary Ammonium Biocide

The antimicrobial actions of three common plant-derived terpenoids (i.e., carvacrol, thymol and eugenol) were compared to those of a typical quaternary ammonium biocide (i.e., benzalkonium chloride; BAC), against both planktonic and biofilm cells of two widespread Staphylococcus species (i.e., S. aureus and S. epidermidis). The minimum inhibitory and bactericidal concentrations (MICs, MBCs) of each compound against the planktonic cells of each species were initially determined, together with their minimum biofilm eradication concentrations (MBECs). Various concentrations of each compound were subsequently applied, for 6 min, against each type of cell, and survivors were enumerated by agar plating to calculate log reductions and determine the resistance coefficients (Rc) for each compound, as anti-biofilm effectiveness indicators. Sessile communities were always more resistant than planktonic ones, depending on the biocide and species. Although lower BAC concentrations were always needed to kill a specified population of either cell type compared to the terpenoids, for the latter, the required increases in their concentrations, to be equally effective against the biofilm cells with respect to the planktonic ones, were not as intense as those observed in the case of BAC, presenting thus significantly lower Rc. This indicates their significant anti-biofilm potential and advocate for their further promising use as anti-biofilm agents.

New Synthetic Nitro-Pyrrolomycins as Promising Antibacterial and Anticancer Agents

Pyrrolomycins (PMs) are polyhalogenated antibiotics known as powerful biologically active compounds, yet featuring high cytotoxicity. The present study reports the antibacterial and antitumoral properties of new chemically synthesized PMs, where the three positions of the pyrrolic nucleus were replaced by nitro groups, aiming to reduce their cytotoxicity while maintaining or even enhancing the biological activity. Indeed, the presence of the nitro substituent in diverse positions of the pyrrole determined an improvement of the minimal bactericidal concentration (MBC) against Gram-positive (i.e., Staphylococcus aureus) or -negative (i.e., Pseudomonas aeruginosa) pathogen strains as compared to the natural PM-C. Moreover, some new nitro-PMs were as active as or more than PM-C in inhibiting the proliferation of colon (HCT116) and breast (MCF 7) cancer cell lines and were less toxic towards normal epithelial (hTERT RPE-1) cells. Altogether, our findings contribute to increase the knowledge of the mode of action of these promising molecules and provide a basis for their rationale chemical or biological manipulation.

Antimicrobial Terpenoids as a Potential Substitute in Overcoming Antimicrobial Resistance

There was a golden era where everyone thought that microbes can no longer establish threat to humans but the time has come where microbes are proposing strong resistance against the majority of antimicrobials. Over the years, the inappropriate use and easy availability of antimicrobials have made antimicrobial resistance (AMR) to emerge as the world's third leading cause of death. Microorganisms over the time span have acquired resistance through various mechanisms such as efflux pump, transfer through plasmids causing mutation, changing antimicrobial site of action, or modifying the antimicrobial which will lead to become AMR as the main cause of death worldwide by 2030. In order to overcome the emerging resistance against majority of antimicrobials, there is a need to uncover drugs from plants because they have proved to be effective antimicrobials due to the presence of secondary metabolites such as terpenoids. Terpenoids abundant in nature are produced in response to microbial attack have huge potential against various microorganisms through diverse mechanisms such as membrane disruption, anti-quorum sensing, inhibition of protein synthesis and ATP. New approaches like combination therapy of terpenoids and antimicrobials have increased the potency of treatment against various multidrug resistant microorganisms by showing synergism to each other.