Colonization Of Microorganisms Research Articles

Stratification of microbial communities and their functions in mossy biofilms colonizing the giant monolithic statue of buddha

Moss-microbial biofilm is an important topic for the biodeterioration of sandstone heritages. However, the processes that biofilms colonize and erode sandstone heritages should be better defined. We divided mosses into three strata perpendicular to the sandstone face in the direction from the atmosphere to the sandstone surface (the upper layer, the middle layer, and the lower layer) to explore the mechanisms involved. The results showed that the bacteria in various layers of moss exhibited a distinct layered pattern of nutrient strategies. The bacteria in the upper layer were mostly photoautotrophic (e.g., Cyanobacteria, WPS-2, etc.) and methylotrophic bacteria (e.g., Methylobacterium-Methylorubrum, Sphingomonas, etc.). The bacteria in the lower layer were primarily heterotrophic as special Actinobacteria with the ability of weathering (e.g., Actinomycetospora, Nocardioides, etc.). Particularly, the potential acid condition in the lower layer would promote the growth of acidophilic bacteria (e.g., Acidipila, Acidiphilium, etc.) and acidophilic iron-reducing bacteria (e.g., Acidiphilium, Acidicaldus, etc.), which deteriorate the alkaline cement and ferric oxides. Furthermore, nucleotide sequences associated with the Calvin-Benson-Bassham cycle, methanol utilization (methanol dehydrogenase), nitrogen fixation (nitrogenase), and ammonia oxidation (ammonia monooxygenase) were more prevalent in the upper layer of bacterial communities. The nucleotide sequences related to the reductive tricarboxylic acid cycle, reduced acetyl-CoA pathway, decomposition of organic carbon (β-1,4-glucosidase), and organic nitrogen (β-N-acetyl glucosaminidase) were more abundant in the lower layer. Therefore, in addition to the damage to the moss itself, we should pay more attention to the microorganisms that live in symbiosis with it. Our study shows that the strategy of stratified colonization of microorganisms would supply the nutrients available for moss-microbial biofilm, the formation of which would in turn deteriorate sandstone heritages.

The influence of smoking on the periodontal biome. A review.

Abstract Periodontal disease is believed to be an opportunistic infection due to the interaction of bacterial plaque and the patient’s response that may be influenced by environmental, genetic, and other risk factors. In addition to the fact that smoking is considered a risk factor in many systemic diseases, it has also been associated with the initiation of periodontal disease. Smoking is one of the modifiable risk factors and has a significant influence on the development, progress, and results of the treatment of periodontal disease. The current state in the field of study suggests that smoking aids the colonization of periodontal microorganisms, accelerating the onset of periodontal disease. Biological modifications in pathogens, such as Porphyromonas gingivalis, along with poor immune response, influence the variations of subgingival flora in smoking patients. Only with an individual approach can the risk factors of each patient be identified and satisfactory results obtained. The aim of this paper is to present a comprehensive review of the influence of smoking on periodontal microbiome and the importance of adopting the appropriate treatment method according to the influence of this risk factor on healing.

Denture Base PMMA Resin Containing Vanillin Inhibits Biofilm Formation of Bacteria Associated with Malodor

Dentures are prosthetic device made of polymethyl methacrylate acrylic (PMMA) resin generally used by elderly people to replace their real teeth. However, the porosity and surface irregularities of acrylic resin are undesirable aspects of the denture base that can support colonization of oral microorganisms on the denture surface, particularly those associated with malodor. Oral malodor is a common and upsetting situation frequently found in denture wearers due to inadequate denture cleaning. A large number of strategies had been employed to minimize the potential bacterial pathogens, including mechanical brushing and using chemical agents. Therefore, we have developed denture PMMA resin containing vanillin and evaluated antimicrobial potential against four species of bacteria related to oral malodor. Denture base resin samples were prepared with dimensions of 10 mm x 10 mm x 1 mm. according to the amount of incorporating vanillin concentrations (0.1%, 0.5% and 1.0% w/w) and coated with saliva. Then, the biofilm formation of four species of bacteria (Porphyromonas gingivalis ATCC 33277, Aggregatibacter actinomycetemcomitans ATCC 33384, Fusobacterium nucleatum ATCC 25586, and Actinomyces viscosus ATCC 19246) was performed on resin samples in anaerobically condition for 48-72 h. Denture resin sample without vanillin was prepared in the same way and used as a control. The quantity of vital biofilm was assessed by WST Microbial Cell Counting Kit (Dojindo Molecular Technologies, USA). Kruskal-Wallis test followed by Dunn’s method were applied for statistical analysis. The results showed that in the groups of 0.5% and 1.0% w/w vanillin, significant decreases of biofilm mass were observed in all tested bacteria (P. gingivalis, A. actinomycetemcomitans, and F. nucleatum) compared with controls, except for A. viscosus. Approximately 30% to 38% bacterial biofilm reduction was demonstrated at 1.0% w/w vanillin on three species of bacteria, whereas 7% to 27% biofilm decreases were observed at 0.5% vanillin. No significant biofilm reduction was observed in A. viscosus. This conforms to our previous studies which revealed the antimicrobial properties of denture PMMA resin containing vanillin on respiratory pathogens and oral yeast. Denture base resin consisting of vanillin may be considered as a promising dental appliance for the use to prevent or solve the problem of oral malodor in patients who wear dentures.

Morpho-anatomical responses of Catharanthus roseus due to combined heavy metal stress observed under Scanning Electron Microscope

Heavy metals trigger various plant responses that basically vary with the intensity as well as duration of stress. Comprehension of the morphological and anatomical responses to such stress is essential for a holistic perception of plant resistance mechanisms to metal-excess conditions in higher plants. In the present study, the effects of heavy metals on morpho-anatomy of Catharanthus roseus based on its potential to tolerate metal stress has been studied in industrially polluted environments. The tissue samples of these plants grown in contaminated and uncontaminated soils were processed for analysis under Scanning Electron Microscope (SEM). Briefly, harvested tissues were pre-fixed using glutaraldehyde and paraformaldehyde in sodium cacodylate (CAC) buffer, followed by post fixation in osmium tetroxide. Further, the digital micrographs of critically dried samples were captured. The analysis of micrographs revealed structural changes like cell wall thickening, increased stele diameter, increased root and shoot diameter, variations in stomatal number, enlargement of trichomes and salt glands of plants grown in contaminated soil when compared to those grown in uncontaminated soil. The study also provided microscopic evidence of endophytic colonization of microorganisms within surface-disinfected plant tissues. Based on the varied morpho-anatomical responses due to heavy metal stress, several physiological and metabolic mechanisms of plants were deciphered.

REVIEW OF EVALUATION METHODS FOR BIODEGRADABILITY OF POLYMERIC MATERIALS

Development and further use of biodegradable polymeric materials requires prior assessment the degree of their biodegradation. There are a large number of methods developed taking into account the specifics of the destruction of polymeric materials. The purpose of this review is to systematize scientific and technical information regarding methods for assessing the biodegradation of polymeric materials. Laboratory methods of researches, including the following: influence of abiotic factors (temperature, moisture, UV irradiation), impact of microorganisms (fungi, bacteria, yeast), respiratory methods (Sturm, Zahn-Wellness, etc.), conditions of composting, enzyme analysis methods, ecotoxicity tests are given. Test methods in both aqueous and solid media are also presented. The parameters of biodegradability, which determine the degree of destruction (mass, strain strength, molecular weight distribution, temperature characteristics, macro-and microstructure of samples, etc.) or the composition and properties of the biological system in which biodegradation takes place (acidity, respiratory activity, chemical and microbiological composition of soil or other biological environment, etc.) are considered as well. Advantages of laboratory methods for studying the biodegradation of polymeric materials could be realized in the given directions: varying of the experimental conditions (temperature, humidity, UV and IR radiation, the presence of aggressive media, etc.), biochemical compositions of the environment; study of the ability of individual strains of microorganisms to dispose of polymer composites and targeted selection of the most active microbial associations (in particular, for the manufacture of special biocomposts); utilize of simple and fast methodical approaches and modern devices for evaluation experiments. However, laboratory methods do not always allow modeling a set of endogenous and exogenous factors that define the process of biodegradation in the natural environment. Therefore, this review also considers methods for assessing biodegradation in the environment. So, the essence of the test regarding the samples’ burial in the ground is given. International standards governing methods for assessing the biodegradability of organic substances and polymeric materials are summarized. Applying different test methods, one can evaluate the whole process of biodegradation of polymeric materials, consisting of several stages, which occur regardless the type of microorganisms and accompanying abiotic factors, and can be represented as follows: adhesion → colonization → biodeterioration → biofragmentation → assimilation → mineralization. Thus, the adhesion and colonization of microorganisms can be estimated by visual, bioindicator and spectral methods. Abiotic degradation and biodeterioration are associated with physical tests (e.g., thermal and physico-mechanical). Biofragmentation is detected by identifying fragments of lower molecular weight (i.e. by chromatographic methods). In turn, assimilation is assessed by the amount of metabolites produced using, for example, respirometric methods or involving analysis of microbial biomass (e.g., macroscopic and microscopic observations). The most productive should be considered a comprehensive approach to the study of biodegradation of polymers. To determine the reliable kinetic parameters and link the mechanism of this process, it is necessary to carry out a comparative analysis of the results of physical, chemical, microbiological experiments, which are carried out in both laboratory and natural conditions.

In-Situ Comparative Study of Eucalyptus, Basil, Cloves, Thyme, Pine Tree, and Tea Tree Essential Oil Biocide Efficacy.

Bio-colonization is a dynamic and multiphasic process headed by microorganisms. Conventional treatments to process affected stone materials include chemical biocides, whose formulations are mainly composed of quaternary ammonium salts(QAs), reported to be toxic for human health, dangerous for the environment, and not biodegradable. Accordingly, novel green and eco-friendly products are a promising alternative to treat stone materials deteriorated by microorganism colonization. In this study, the efficacy of pure essential oils (EOs) and a mix of EOs was assessed in situ and compared to a conventional biocide based on QAs, and two commercially green products based on EOs, which were taken as references, through application on a mosaic located at the Archaeological Park of Ostia Antica (Rome). The EO biocide efficacy was analyzed by ultraviolet induced luminescence, spectro-colorimetry and bio-luminometry analyses while the possibility of their permanence on simulated substrate was studied by FTIR spectroscopy. It was observed by FTIR analysis, that EOs considered volatile can leave a residue after the application; typical fingerprint bands at about 2926, 1510, and 1455 cm−1 were recorded in the EO spectra. Every tested oil was confirmed to have a biocide action although minimal in relation to the most conventional products based on QAs. The synergy of the essential oils revealed positive results, showing a stronger biocide efficacy. Further investigation should be carried out to develop the method of application and study of essential oils on cultural heritage.

Variations in microbial community on different materials in Sanya Marine Environment Experimental Station, China.

Marine biofouling occurs through the colonization of undesired microorganisms on the surfaces of structures. In this study, four immersion cycles (2, 5, 15, and 25 days) of total immersion in seawater were carried out at the Sanya Marine Environmental Test Station using three materials: industrial pure titanium (Ti), hot-dip zinc (Zn), and glass slide (GS). Three phyla, four classes, and nine bacterial genera were identified. The dominant genera were Pseudomonas, Alteromonas, and Pseudoalteromonas. The number of bacteria increased with soaking time. Sixty-one species of diatoms belonging to 30 genera, 24 families, and 16 orders were detected, among which the dominant genera were Amphora, Nitzschia, and Navicula. Four genera of ciliates belonged to two classes, three orders, and four families, among which the dominant species were Euplotes sp. and Uronema marinum. Tubular polychaetes was the dominant metazoans. Species diversity increased over time. The highest biofilm diversity was observed on the GS surface. The diversity of biofilms on the Ti surface was higher than that on the Zn surface. This study provides basic data for marine material research, marine corrosion, and national defence construction.

Long-term pruning modulates microbial community structure and their functional potential in Tea (Camellia sinensis L.) soils

Tea tree pruning, an essential agronomic practice for maintaining the plant's table height, leads to the gradual accumulation of allelochemicals and accompanying changes in the physicochemical and biological properties of tea garden soils. The accumulated allelochemicals coupled with disturbance in the soil properties including soil microbiota gradually lead to ‘soil-sickness’ impeding the establishment of newly-planted tea saplings (replanting) and tea crop productivity. Although pruning is an essential and regular practice in tea management, its effect on the soil properties and the microbial populations is less understood. We used a metagenomics approach to decipher and compare the microbial community structure and functional characteristics in tea soils under pruning and non-pruning practices. Principal component analysis indicated the metagenomes of the two sample plots to be unique with key microbial taxa and metabolic pathways. The plot with pruned crops had significantly lesser microbial abundances and richness, but it harbored a relatively higher proportion of biologically important soil bacteria such as Pseudomonas, Candidatus Solibacter, Rhodopseudomonas and Nitrobacter. This indicated that a specific population and its associated soil functions play a significant role in plant growth and survival under stress conditions. The metabolic functions related to microbial growth and reproduction were prevalent in both metagenomes as revealed through the Kyoto Encyclopedia of Genes and Genomes (KEGGs) and Cluster of Orthologous Groups (COGs) analyses. The pruned-plot-metagenome contained six metabolic pathways linked to different stress-responsive metabolisms (starch, arginine and proline, pyrimidine, ribosome, and peroxisome). Although long-term pruning in tea plantations can decrease the microbial abundance, richness, and functions in soil, plants under these stress conditions may selectively encourage the growth and colonization of functionally-important microorganisms to aid in their survivability.

Multikingdom interactions govern the microbiome in subterranean cultural heritage sites

SignificanceThe conservation of historical relics against microbial biodeterioration is critical to preserving cultural heritages. One major challenge is our limited understanding of microorganisms' dispersal, colonization, and persistence on relics after excavation and opening to external environments. Here, we investigate the ecological and physiological profiles of the microbiome within and outside the Dahuting Han Dynasty Tomb with a 1,800-y history. Actinobacteria dominate the microbiome in this tomb. Via interkingdom signaling mutualism, springtails carry Actinobacteria as one possible source into the tomb from surrounding environments. Subsequently, Actinobacteria produce cellulases combined with antimicrobial substances, which helps them to colonize and thrive in the tomb via intrakingdom competition. Our findings unravel the ecology of the microbiomes colonizing historical relics and provide help for conservation practices.

Crosslinking as a treatment for infectious crystalline keratopathy

Infectious crystalline keratopathy (ICK) is a rare cornea disease, manifested by gray-and-white tree-like or needle-like stromal opacities with minimal signs of inflammation. The disease is caused by the colonization of microorganisms on the corneal stroma and their formation of biofilms, making them extremely resistant to treatment with antibiotics and to the immune response of the patient. Typically, the most important risk factor for ICK development is the presence of an immunodeficiency cornea condition with long-term topical steroid therapy, which is normally prescribed after keratoplasty. Two clinical cases of ICK are discussed in which the reduction of topical glucocorticoids and the intensive use of antibiotics did not result in positive clinical changes. Only after an accelerated crosslinking procedure (PACK-CXL), needlelike opacities disappeared in the area of microbial invasion and signs of infiltration appeared, indicating the restoration of the local immune response. This phenomenon is likely due to the destruction of the biofilm and the microbial agents themselves, which afterwards contributed to a more effective impact of the antibacterial drug. This combined treatment led to resorption of the inflammatory focus with the formation of local opacification. The effectiveness of PACK-CXL in infectious processes is explained by the effects of both riboflavin and ultraviolet radiation. No literature references on the use of cross-linking in the treatment of ICK are available. In our opinion, cross-linking in early ICK patients after keratoplasty is justified by the inability, in some cases, to completely discontinue glucocorticosteroid therapy, as this will greatly increase the chances of rejection and graft jailure. PACK-CXL can be an effective way of destroying the biofilm in the corneal stroma.

Disinfection Procedures and Their Effect on the Microorganism Colonization of Dental Impression Materials: A Systematic Review and Meta-Analysis of In Vitro Studies.

Dental impressions are contaminated with potentially pathogenic microorganisms when they come into contact with patient blood, saliva, and plaque. Numerous disinfectants are used; however, no sole disinfectant can be designated as universal for all the impression materials. Thus, the aim of this study is to systemically review the literature to evaluate the effect of the existing disinfection procedures on the bacterial colonization of dental impression materials. This systematic review and meta-analysis was conducted according to the PRISMA statement. PubMed (MEDLINE), Web of Science, Scopus, EMBASE, and SciELO databases were screened up to April 2021. Eligibility criteria included in vitro studies reporting the antibacterial activity of disinfectant solutions in dental impression materials. The meta-analysis was performed using Review Manager (version 5.3.5). A global comparison was performed with the standardized mean difference based on random-effect models at a significance level of α = 0.05. A total of seven studies were included in the meta-analysis. The included studies described the effect of disinfection processes with chlorhexidine gluconate, alcohol, sodium hypochlorite, glutaraldehyde, and hydrogen peroxide in alginate, polyvinyl siloxane, and polyether impression materials. The meta-analyses showed that the use of chlorhexidine, alcohol, glutaraldehyde, and sodium hypochlorite reduced the colony-forming units by a milliliter (CFU/mL) in alginate (p < 0.001). On the other hand, glutaraldehyde, sodium hypochlorite, and alcohol reduced the CFU/mL in polyvinyl siloxane (p < 0.001). Finally, alcohol and glutaraldehyde reduced the CFU/mL in polyether material (p < 0.001). High heterogenicity was observed for the alginate and polyvinyl siloxane materials (I2 = 74%; I2 = 90%). Based on these in vitro studies, the disinfection of impression materials with several disinfection agents reduces the CFU/mL count.

Impact of pattern recognition receptor on the homeostasis of gut microbiota

<p indent="0mm">Tremendous amount of symbiotic microorganisms colonize the mucosal and barrier organs such as the intestinal tract, lung, skin and reproductive tract. These bugs consistently interact with the host immune system and epithelial barrier in a dynamic way, which is essential for maintaining homeostasis and health. Symbiotic flora affects the development and function of the immune system through its various components and metabolites, and the immune system regulates the development, colonization and function of the symbiotic microorganisms through various immune cells and host factors. The immune system consists of the innate and adaptive immune systems, and the innate immune system is at the forefront of interacting with symbiotic microorganisms or responding to infection by pathogens. This paper reviewed the impact of functional loss or abnormality of pattern recognition receptors (PRRs) in the host innate immune system on intestinal microbiota, mainly including the regulation of gut microbiota by the inflammosomes, NOD-like receptors (NLRs), Toll-like receptors (TLRs), C-type lectin receptors (CLRs) and RIG-I-like receptors (RLRs). The synergistic effect of genetic and environmental factors in shaping the microbiota was also pointed out.

Development of a thermosensitive hydrogel loaded with DTT and SDF-1 facilitating in situ periodontal bone regeneration

• P. gingivalis infection causes increased ROS level and inhibits osteoblast activity. • A multifunctional thermosensitive hydrogel was prepared with PEG-DA, DTT and SDF-1. • The hydrogel achieved co-therapy effect by combined application of DTT and SDF-1. • The hydrogel facilitated in situ periodontal bone regeneration in periodontitis rat. • The co-therapy strategy and the hydrogel are promising for regenerative medicine. Periodontitis is characterized by local inflammatory response and alveolar bone resorption induced by pathogenic microorganisms colonization. The increase in reactive oxygen species (ROS) levels not only aggravates the local inflammation, but also inhibits the process of osteogenesis. The coupled process of reducing ROS level and reshaping the activity of osteoblasts is prerequisite to facilitate in situ periodontal tissue regeneration. In this study, we developed a thermosensitive hydrogel loaded with dithiothreitol (DTT) and stromal cell-derived factor-1 (SDF-1) and explored its effect on reshaping osteoblasts activity and facilitating periodontal bone regeneration. In vitro , the hydrogel PEGD@SDF-1 significantly reduced cellular ROS levels, reactivated the Wnt/β-catenin pathway of osteoblasts and restored their osteogenic ability in an inflammatory state. In vivo , the hydrogel PEGD@SDF-1 was applied in rat periodontitis models and showed satisfactory effects on reducing the level of ROS damage, reactivating the Wnt/β-catenin pathway, alleviating the inflammation level, and promoting the periodontal bone regeneration, simultaneously. Taken together, these results suggest that the combined application of DTT and SDF-1 facilitates in situ periodontal tissue regeneration and the thermosensitive hydrogel PEGD@SDF-1 is a promising candidate for periodontal therapy.

Microplastics benefit bacteria colonization and induce microcystin degradation

Microplastics (MPs) can sorb toxic substances and be colonized by microorganisms. However, the interactions between the adsorbed toxic substances and the MPs biofilm remains inadequately understood. Here, a 37-days microcosm experiment was conducted to investigate the influence of polystyrene microplastics (PS-MPs) on microcystin (MC-LR) behavior in turbulent scenarios. The results revealed that adsorption by PS-MPs was the primary process that led to a quick reduction of aquatic MC-LR concentrations. With the colonization of microorganisms on the PS-MPs, the attached biofilm altered the surface properties of PS-MPs, which enhanced the bio-adsorption of MC-LR. Meanwhile, microcystins degrading bacteria, such as Sphingomonadaceae and Methylophilaceae, inhabited in the biofilm, which facilitated the MC-LR biodegradation; this was also demonstrated by the identified MC-LR degradation products. Thus, the MC-LR concentration in water was constantly decreased, with a maximum removal capability of 35.8% in PS-MPs added groups. In addition, a 25% reduction of MC-LR was recorded in PS-MPs added static water. This suggested that the interaction between PS-MPs, biofilm, and MC-LR may be prevalent in natural waters. Our results indicate MPs as vectors for toxic substances could be a double-edged sword (adsorption and biodegradation), which provides new insights for understanding the ecological risks of microplastics.

The effect of oral care using honey as an additional topical agent on oral health status of intubated patients in the intensive care unit

BackgroundPatients using endotracheal tubes are at high risk of oral health status dysfunction due to impaired natural airway defence, oral flora composition changes and protective substances of the teeth, medication causing xerostomia. Oral care has not been enough to manage oral mucosal dryness, so an additional topical agent is needed to protect oral mucosa to maintain oral health. Honey is one of the recommended topical agents. ObjectiveThis study aims to identify the effect of oral care with honey as topical agents on the oral health status of patients using endotracheal tube in the Intensive Care Unit. MethodsThis was an experimental study with a randomized pretest and posttest design. The sample was adult intubated patients, consisting of 36 patients. The data were analysed using the parametric test, and dependent and independent t-test. ResultsThe oral health score in the control group was found to be pre & post mean score11.94 and 13.28 (p=.004) respectively, while in the intervention group 11.89 and 8.33 (p<.001). Mean differences in both groups were 4.95 (p<.001) and the BOAS subscale differences were seen on the lips, gums & mucosa, and tongue (p<.05). ConclusionOral care with honey as a topical agent can improve the oral health status of intubated patients on the lips, gum, mucosa, and tongue subscale. Therefore, honey as an additional topical agent can be a moisturizer to maintain the oral mucosa for intubated patients in the Intensive Care Unit. Furthermore, good mucosal health will help prevent the infection and colonization of microorganisms.

Thermal Spray Coatings for Protection Against Microbiologically Induced Corrosion: Recent Advances and Future Perspectives

Corrosion has been persisting as the most severe concern for steel structures in the marine environment. Due to the widespread occurrence of biofouling, apart from the electrochemical corrosion, microbiologically induced corrosion (MIC) is an important factor that triggers the deterioration of marine steel infrastructures. Traditional anti-corrosion coatings usually lack the antifouling function, attachment and colonization of marine microorganisms therefore in most cases accelerate the existing corrosion damage. Anti-corrosive coating fabricated by thermal spray has been extensively applied for the marine corrosion prevention, yet the anti-MIC coatings deposited by thermal spray technical route still keep elusive. Developing thermal-sprayed coatings with dual anti-corrosion and antifouling performances is the key to combating MIC. In this review, most recent advances in understanding biofouling and developing antifouling and anti-MIC techniques are surveyed. The formation and evolution of MIC and biofouling, and the effect of microbial biofilm on their occurrence are addressed briefly. Strategies involving the use of chemical methods, physical methods and biological methods to prevent MIC and biofouling are discussed. Selection and design of thermal spray coating materials with desired corrosion resistance and antifouling performances are reviewed. Current perspectives and future possibilities of thermal-sprayed marine coatings for long-term anti-MIC applications are also discussed.

Armed to the Teeth-The Oral Mucosa Immunity System and Microbiota.

The oral cavity is inhabited by a wide spectrum of microbial species, and their colonization is mostly based on commensalism. These microbes are part of the normal oral flora, but there are also opportunistic species that can cause oral and systemic diseases. Although there is a strong exposure to various microorganisms, the oral mucosa reduces the colonization of microorganisms with high rotation and secretion of various types of cytokines and antimicrobial proteins such as defensins. In some circumstances, the imbalance between normal oral flora and pathogenic flora may lead to a change in the ratio of commensalism to parasitism. Healthy oral mucosa has many important functions. Thanks to its integrity, it is impermeable to most microorganisms and constitutes a mechanical barrier against their penetration into tissues. Our study aims to present the role and composition of the oral cavity microbiota as well as defense mechanisms within the oral mucosa which allow for maintaining a balance between such numerous species of microorganisms. We highlight the specific aspects of the oral mucosa protecting barrier and discuss up-to-date information on the immune cell system that ensures microbiota balance. This study presents the latest data on specific tissue stimuli in the regulation of the immune system with particular emphasis on the resistance of the gingival barrier. Despite advances in understanding the mechanisms regulating the balance on the microorganism/host axis, more research is still needed on how the combination of these diverse signals is involved in the regulation of immunity at the oral mucosa barrier.

Piezoelectric Disinfection of Water Co-Polluted by Bacteria and Microplastics Energized by Water Flow

The presence of microplastics in the aquatic environment, as a vector for colonization and proliferation of harmful microorganisms, brings a great challenge for water disinfection. This study investigates piezoelectric inactivation of Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Enterococcus faecalis (E. faecalis) on the surface of microplastics under water flow by using molybdenum disulfide as piezoelectric material. The piezoelectric sterilization capacity was evaluated by comparing different polymer types and sizes of microplastics, in which 4.5 log10 CFU mL–1 E. coli cells were reduced for 50 μm PVC particles at a water flow speed of 80 rpm in 20 min. Piezoelectric disinfection was dependent on water flow rates and treatment time and was feasible in riverine water containing authentic microplastics and in a spiral reactor that simulated natural water flow. Reactive oxygen species were generated via water flowing over the piezoelectric material, resulting in the inactivation of bacteria on the surface of microplastics. This study highlighted the great potential of water flow as a “green” source of energy and elucidated a new opportunity of piezoelectric disinfection in aqueous media containing microplastics.

Functionalization of surgical meshes with antibacterial hybrid Ag@crown nanoparticles

We report here on functionalization of surgical meshes (PVDF) with novel hybrid material, consisting of Ag@crown nanoparticles, embedded on CaCO3/PEG nanosheets. Nanosheets of PEG 4000 with average thickness of 25 nm enclosing CaCO3 nanoparticles with average sizes of 150 nm were applied for sustained release of Ag@crown nanoparticles that in turn serve as antibacterial agent. The characterization of obtained hybrid nanostructures was carried out by microscopic and spectroscopic methods. Microbiological tests confirmed the effectiveness of hybrid material, consisting of Ag@crown nanoparticles, embedded in CaCO3/PEG nanostructure, as an antibacterial coating for surgical meshes. This coating was applied to insure antibacterial properties of meshes against microorganism colonization, in order to significantly improve their action in typical applications.

The effects of functional microbial agents on the soil microbial communities of high-frigid grassland under desertification in Northwest Sichuan

Grassland desertification seriously destroys the structure of the soil microbial communities and further accelerates the deterioration of grassland. In this study, functional microbial agents were sprayed on degraded grasslands and studied by means of real-time fluorescence quantitative PCR and high-throughput sequencing methods. The aim was to investigate the effects of microbial agents on the soil microbial community structure and soil remediation functions in different degraded grasslands (LDG: light desertification grassland, MDG: medium desertification grassland, and HDG: heavy desertification grassland). The results showed that after treatment with the microbial agents, bacterial abundance increased by 96.24% (LDG), 95.19% (MDG), and 93.47% (HDG), respectively, and fungal abundance increased by 85.77% (LDG), 95.85% (MDG) and 22.49% (HDG), respectively. Further, with the colonisation and acclimatisation of foreign functional microorganisms, the microbial agents greatly influenced the structure of the soil microbial community, increased the microbial diversity index, and significantly changed the microbial community composition. The application of the microbial agents did not only improve the forage yield and quality, but also guided the soil restoration, improved the soil water content of sandy grassland, adjusted the soil pH, significantly increased the content of soil organic matter, total nitrogen, and total phosphorus, and also inhibited the growth of soil-borne pathogens. Our findings provide new ideas and guidance for the management of degraded grassland.