Metabolic Activity Of Bacteria Research Articles

Anodization as a scalable nanofabrication method to engineer mechanobactericidal nanostructures on complex geometries.

Bacterial contamination of implant surfaces is one of the primary causes of their failure, and this threat has been further exacerbated due to the emergence of drug-resistant bacteria. Nanostructured mechanobactericidal surfaces that neutralize bacteria via biophysical forces instead of traditional biochemical routes have emerged as a potential remedy against this issue. Here, we report on the bactericidal activity of titania nanotubes (TNTs) prepared by anodization, a well-established and scalable method. We investigate the differences in bacterial behavior between three different topographies and demonstrate the applicability of this technique on complex three-dimensional (3D) geometries. It was found that the metabolic activity of bacteria on such surfaces was lower, indicative of disturbed intracellular processes. The differences in deformations of the cell wall of Gram-negative and positive bacteria were investigated from electron micrographs Finally, nanoindentation experiments show that the nanotubular topography was durable enough against forces typically experienced in daily life and had minimal deformation under forces exerted by bacteria. Our observations highlight the potential of the anodization technique for fabricating mechanobactericidal surfaces for implants, devices, surgical instruments, and other surfaces in a healthcare setting in a cheap, scalable way.

Inhibitory potential of turmeric extract (Curcuma domestica Val.) toward the growth of Streptococcus gordonii bacteria

Introduction: Dental caries is a disease caused by damage to the hard tissue of the teeth by the metabolic activity of bacteria, one of which is the cariogenic bacteria Streptococcus gordonii. Turmeric is one of the most popular spices in Asia with good antibacterial capabilities. Turmeric content such as curcumin can inhibit bacterial growth. Objective: To determine the potential inhibitory power of turmeric extract on the growth of Streptococcus gordonii. Method: The research is carried out using in vitro laboratory experimental analytical research with a posttest only control group design. The research determined the effect of turmeric extract concentrations of 50%, 12.5%, 3.125%, 0.78% against Streptococcus gordonii bacteria on agar media. Statistical data analysis is carried out to determine whether there was a significant effect of turmeric extract on the inhibition of the growth of Streptococcus gordonii bacteria in each treatment. Results: There was a significant influence on the test results between groups of turmeric extract concentration on the inhibitory power of Streptococcus gordonii bacteria. Conclusion: Turmeric extract can inhibit the growth of Streptococcus gordonii. Higher concentration of turmeric rhizome extract which can inhibit the growth of Streptococcus gordonii bacteria more effectively.

Silver coating on dental implant-abutment connection screws as potential strategy to prevent loosening and minimizing bacteria adhesion.

Introduction: One of the main problems for the long-term behavior of dental implants are loosening of the implant-abutment connection screws and bacterial infiltration. The aim of this work is to increase the screw fixation by silver coating, providing superior mechanical retaining and antibacterial effect. Methods: Eighty dental implants with their abutments and screws have been studied. Twenty screws were not coated and were used as a control while the rest of screws were silver coated by sputtering, with three different thickness: 10, 20 and 40μm and 20 screws per each thickness. Coating morphology and thickness were determined by scanning electron microscopy using image analysis systems. The screws were tightened for each of the thicknesses and the control with two torques 15 Ncm and 20 Ncm and tested under mechanical fatigue simulating oral stresses up to a maximum of 500,000 cycles. The remaining torques at different cycles were determined with a high-sensitivity torquemeter. Cell viability assays were performed with SaOs-2 osteoblasts and microbiological studies were performed against Streptococcus gordonii and Enterococcus faecalis bacteria strains, determining their metabolic activity and viability using live/dead staining. Results: It was observed a decrease in torque as cycles increase. For a preload of 15 Ncm at 100,000 cycles, the loosening was complete and, for 20 Ncm at 500,000 cycles, 85% of torque was lost. The silver coatings retained the torque, especially the one with a thickness of 40μm, retaining 90% of the initial torque at 500,000 cycles. It was observed that osteoblastic viability values did not reach 70%, which could indicate a slight cytotoxic effect in contact with cells or tissues; however, the screw should not be in direct contact with tissue or living cells. Silver coating induced a significant reduction of the bacteria metabolic activity for Streptococcus gordonii and Enterococcus faecalis, around 90% and 85% respectively. Discussion: Therefore, this coating may be of interest to prevent loosening of implant systems with a worthy antibacterial response.

Fe-loaded biochar thin-layer capping for the remediation of sediment polluted with nitrate and bisphenol A: Insight into interdomain microbial interactions

The information on the collaborative removal of nitrate and trace organic contaminants in the thin-layer capping system covered with Fe-loaded biochar (FeBC) is limited. The community changes of bacteria, archaea and fungi, and their co-occurrence patterns during the remediation processes are also unknown. In this study, the optimized biochar (BC) and FeBC were selected as the capping materials in a batch experiment for the remediation of overlying water and sediment polluted with nitrate and bisphenol A (BPA). The community structure and metabolic activities of bacteria, archaea and fungi were investigated. During the incubation (28 d), the nitrate in overlying water decreased from 29.6 to 11.0 mg L−1 in the FeBC group, 2.9 and 1.8 times higher than the removal efficiencies in Control and BC group. The nitrate in the sediment declined from 5.03 to 0.75 mg kg−1 in the FeBC group, 1.3 and 1.1 times higher than those in Control and BC group. The BPA content in the overlying water in BC group and FeBC group maintained below 0.4 mg L−1 during incubation, signally lower than in the Control group. After capping with FeBC, a series of species in bacteria, archaea and fungi could collaboratively contribute to the removal of nitrate and BPA. In the FeBC group, more metabolism pathways related to nitrogen metabolism (KO00910) and Bisphenol degradation (KO00363) were generated. The co-occurrence network analysis manifested a more intense interaction within bacteria communities than archaea and fungi. Proteobacteria, Firmicutes, Actinobacteria in bacteria, and Crenarchaeota in archaea are verified keystone species in co-occurrence network construction. The information demonstrated the improved pollutant attenuation by optimizing biochar properties, improving microbial diversity and upgrading microbial metabolic activities. Our results are of significance in providing theoretical guidance on the remediation of sediments polluted with nitrate and trace organic contaminants.

Application of electric fields to improve cementation homogeneity of biogrouted sands

AbstractThe inhomogeneity of cementation is a common problem in soil improvement with microbially induced carbonate precipitation process (MICP), which is caused by uneven spatial distribution of bio‐induced calcium carbonate precipitation. Electric field adjustment method was developed and adopted for improving cementation homogeneity of bio‐grouted sands in this research. Horizontal one‐dimensional biogrouting experiments were conducted in sand columns under 0.1 V/cm of direct current (DC) electric field. The column treated with DC electric field showed a significant improvement in homogeneity of calcium carbonate precipitation as compared to the control (without DC electric field). Spatial distribution of calcium carbonate in columns were affected by the properties of bacteria, whether suspended or attached. In general, the attached bacteria with uneven spatial distribution played an important role in the calcium carbonate precipitation when flow rate was regulated at 0.54 cm/min, while the suspended bacteria could also be attached upon times with consumption of cations during biogrouting. With the influence of electric field, suspended bacterial transport in porous media occurred in one direction to the target locations because of the electrophoresis at an average speed of 0.14 cm/h, while sodium ion was found to be moved from anode to cathode by electromigration approach. Electrolysis of water, on the other hand, resulted a slight fluctuation in pH, even though this variation did not show any significant effect on the metabolic activity of bacteria and microbial‐induced carbonate precipitation process. The redistribution of suspended bacteria and sodium ion in porous media provided a possible for attached bacteria to distribute uniformly, which could be considered as the key factor to influence spatial distribution of the bio‐induced calcium carbonate in application of electric field adjustment method.

Biochar enhanced the stability and microbial metabolic activity of aerobic denitrification system under long-term oxytetracycline stress

Reactors were established to study the feasibility of the direct addition of modified biochar to alleviate the long-term stress of oxytetracycline (OTC) on aerobic denitrification (AD) and improve the stability of the system. The results showed that OTC stimulated at μg/L, and inhibited at mg/L. The higher the concentration of OTC, the longer the system was affected. The addition of biochar, without immobilization, improved the tolerance of community, alleviated the irreversible inhibition effect of OTC, and maintained a high denitrification efficiency. Overall, the main mechanisms of AD enhancement by biochar under OTC stress were: enhancing the bacteria metabolic activity, strengthening sludge structure and substrate transport, and improving the community stability and diversity. This study confirmed that direct addition of biochar could effectively alleviate the negative effect of antibiotics on the microorganisms, strengthen the AD, which provided a new idea to broaden the application of AD technology in livestock wastewater.

Microbial Composition, Bioactive Compounds, Potential Benefits and Risks Associated with Kombucha: A Concise Review

Kombucha is a fermented tea beverage containing bioactive compounds from tea and vital compounds such as acetic acid, D-saccharic acid-1,4-lactone, and glucuronic and gluconic acids produced from the metabolic activities of bacteria and yeasts, which benefit human health. Kombucha contains a symbiotic culture of bacteria and yeast (SCOBY), which actively ferments sugar. Kombucha microbial compositions vary due to environmental conditions and the starter culture. Saccharomyces sp., Schizosaccharomyces pombe, Schizosaccharomyces sp., and Brettanomyces sp. (yeasts) and Acetobacter aceti, Komagataeibacter xylinum (formerly known as Gluconacetobacter xylinum), Gluconobacter oxydans, and Acetobacter pasteurianus (acetic acid-producing bacteria) are commonly found in kombucha. This review focused on the microbial compositions of kombucha and their functionality. Aspects discussed include: (i). developments in kombucha, (ii). microbial compositions of kombucha, (ii). microbial production of kombucha cellulose, (iv). factors influencing kombucha microbial compositions, (v). tea type and kombucha bioactive compounds, (vi). kombucha health benefits, and (v). potential risk factors of kombucha consumption. Current gaps, recommendations, and prospects were also discussed. Kombucha production using rooibos as the tea base is recommended, as rooibos is caffeine-free. Upcycling kombucha wastes, mainly SCOBY, for producing cellulose filters, improving food flavors and as a substrate in food fermentations is touched on.

The effect of amino acids and zinc salts on the growth kinetics of bacteria of the genus Escherichia and Staphylococcus

Biologically active substances (BAS) (tryptophan, zinc aspartate, arginine, tatipacin, taurine) have modulating effects on the metabolism of microorganisms in vitro. The study found that biologically active substances have dose-dependent effects on the metabolic activity of bacteria in planktonic form. Daily incubation of bacteria in the presence of a high concentration of biologically active substances (1200–20 000 μg/ml) led to a decrease in the number of planktonic forms. BAS concentrations in the range of 600–150 μg/ml did not have an inhibitory effect on microorganisms. All test substances at a concentration of 150 μg/ml promoted the growth of E. coli strains. Dose-dependent effects of biologically active substances were also observed in relation to bacteria in biofilms. Zinc aspartate at a concentration of 2500 µg/ml has a bactericidal effect on S. aureus and E. coli in monobiofilms. The identity of metabolic flows leads to competition between body cells and microorganisms for nutrient substrates, which is important in the development of the infectious process, and also indicates the need to study the effects of biologically active substances in animal models.

Divergent gene expression responses in two Baltic Sea heterotrophic model bacteria to dinoflagellate dissolved organic matter.

Phytoplankton release massive amounts of dissolved organic matter (DOM) into the water column during recurring blooms in coastal waters and inland seas. The released DOM encompasses a complex mixture of both known and unknown compounds, and is a rich nutrient source for heterotrophic bacteria. The metabolic activity of bacteria during and after phytoplankton blooms can hence be expected to reflect the characteristics of the released DOM. We therefore investigated if bacterioplankton could be used as "living sensors" of phytoplankton DOM quantity and/or quality, by applying gene expression analyses to identify bacterial metabolisms induced by DOM. We used transcriptional analysis of two Baltic Sea bacterial isolates (Polaribacter sp. BAL334 [Flavobacteriia] and Brevundimonas sp. BAL450 [Alphaproteobacteria]) growing with DOM from axenic cultures of the dinoflagellate Prorocentrum minimum. We observed pronounced differences between the two bacteria both in growth and the expressed metabolic pathways in cultures exposed to dinoflagellate DOM compared with controls. Differences in metabolic responses between the two isolates were caused both by differences in gene repertoire between them (e.g. in the SEED categories for membrane transport, motility and photoheterotrophy) and the regulation of expression (e.g. fatty acid metabolism), emphasizing the importance of separating the responses of different taxa in analyses of community sequence data. Similarities between the bacteria included substantially increased expression of genes for Ton and Tol transport systems in both isolates, which are commonly associated with uptake of complex organic molecules. Polaribacter sp. BAL334 showed stronger metabolic responses to DOM harvested from exponential than stationary phase dinoflagellates (128 compared to 26 differentially expressed genes), whereas Brevundimonas sp. BAL450 responded more to the DOM from stationary than exponential phase dinoflagellates (33 compared to 6 differentially expressed genes). These findings suggest that shifts in bacterial metabolisms during different phases of phytoplankton blooms can be detected in individual bacterial species and can provide insights into their involvement in DOM transformations.

Differential bacterial ammonia oxidation patterns in soil particles from two contrasting forests: The importance of interfacial interactions

Soil inorganic nitrogen (N) deficiency limits forest productivity in subalpine regions. The traditional view holds that subalpine coniferous forests are characterized by lower soil inorganic N availability, and such differences are greatly affected by the diversity and abundance of ammonia-oxidizing bacteria. It is known that interfacial interactions between bacteria and solid particles in agricultural and aquatic ecosystems can alter bacterial metabolic activity and biogeochemical processes. However, whether bacteria-soil interfacial interactions induce different ammonia oxidation processes in distinct soil particles remain unknown. Herein, we collected soil particles of different sizes from two contrasting forest sites (a spruce-dominated natural forest and spruce plantation) and examined the effect of soil-Nitrosomonas europaea (a model ammonia-oxidizing bacteria) interfacial interactions on the oxidation of ammonium (NH4+-N) using batch adsorption and semipermeable membrane experiments. The metabolic activity of bacteria was also examined using an isothermal microcalorimetric method. Upon adsorption on soil particles, the ammonia oxidation rate and bacterial metabolism activity were slower than those of free bacteria. The inhibition effect ceased when the bacteria were physically isolated from the soil particles by a membrane, indicating the importance of interfacial interactions in the ammonia oxidation process. Additionally, clay particles were more effective than silts and sands in binding cells and greatly reduced the ammonia oxidation reaction. Across the two forests, natural forest soils exhibited a higher bacterial adsorption capacity but lower bacterial metabolic activity, resulting in a fewer loss of NH4+-N. Our results suggested that stronger bacteria-soil interfacial interactions (especially for clay fractions) were responsible for maintaining high soil inorganic N availability in forests, highlighting the need to incorporate interfacial interactions into biogeochemical models of N cycling in forest ecosystems.

Digital image processing for precise evaluation of concrete crack repair using bio-inspired strategies

• Bacillus pumilus was analyzed in retrofitting of mortar for the very first time. • Digital image processing is employed in monitoring crack healing. • Bio-Consortia significantly reduced the permeability of repaired mortar specimens. • Microbial repair is the potential and sustainable alternative to conventional repairs. Inadequacy of surface coatings and deleterious action to the environment by epoxy-based solution for surface treatment have received the attention for more sustainable techniques of concrete repair. This paper investigated the adequacy of Microbially induced calcite precipitate for mortar crack repair by using a non-ureolytic (avoid the production of ammonia), alkaliphilic bacterial strain with calcium source. The biological metabolic activity of Bacillus pumilus with Calcium lactate was used for crack repair. As Bacillus pumilus was first time reported for concrete repair, germination and growth characteristics were evaluated in the control microbiology laboratory before application to repair. The healing potency by bacterially mediated calcium carbonate was precisely investigated by Digital image processing using the OTSU method of thresholding. Crack healing of 99 – 100 % was achieved by biological repair for mortar samples having average crack width varying from 0.29 to 1.55 mm. The efficacy of crack repair by both bacterial repair and conventional treatments were evaluated through water permeability, water tightness, ultra-sonic measurement, and compressive strength recovery. The samples treated with bacterial treatments exhibited enhanced permeability and water tightness comparable to any other conventional treatments. The bacterial repaired mortar samples showed enhanced values of ultra-sonic measurement and recovered compressive strength equivalent to conventional repair. The enhanced durability of bacterially repaired mortar samples is due to the presence of dense precipitated CaCO 3 by the metabolic activity of bacteria. Further, forensic evaluation confirmed the formation of CaCO 3 in bio-precipitate as a result of metabolic activity triggered by inoculated bacterial consortia.

Climate warming-driven changes in the flux of dissolved organic matter and its effects on bacterial communities in the Arctic Ocean: A review

The warming of the Arctic Ocean impacts the dissolved organic matter (DOM) imports into the Arctic region, which affects the local bacterial communities. This review addressed the current status of DOM inputs and their potential influences on bacteria data (e.g., population, production, and metabolic activity of bacteria), as well as the projected changes of DOM inputs and bacterial communities as a result of climate warming. Microbial communities are likely affected by the warming climate and the transport of DOM to the Arctic Ocean. Imported DOM can alter Arctic bacterial abundance, cell size, metabolism, and composition. DOM fluxes from Arctic River runoff and adjacent oceans have been enhanced, with warming increasing the contribution of many emerging DOM sources, such as phytoplankton production, melted sea ice, thawed permafrost soil, thawed subsea permafrost, melted glaciers/ice sheets, atmospheric deposition, groundwater discharge, and sediment efflux. Imported DOM contains both allochthonous and autochthonous components; a large quantity of labile DOM comes from emerging sources. As a result, the Arctic sea water DOM composition is transformed to include a wider range of various organic constituents such as carbohydrates (i.e., glucose), proteinaceous compounds (i.e., amino acid and protein-like components) and those with terrigenous origins (i.e., humic-like components). Changes to DOM imports can alter Arctic bacterial abundance, cell size, metabolism, and composition. Under current global warming projections, increased inflow of DOM and more diverse DOM composition would eventually lead to enhanced CO2 emissions and frequent emergence of replacement bacterial communities in the Arctic Ocean. Understanding the changes in DOM fluxes and responses of bacteria in the Arctic broadens our current knowledge of the Arctic Ocean’s responses to global warming.

Recent Methods for the Viability Assessment of Bacterial Pathogens: Advances, Challenges, and Future Perspectives

Viability assessment is a critical step in evaluating bacterial pathogens to determine infectious risks to public health. Based on three accepted viable criteria (culturability, metabolic activity, and membrane integrity), current viability assessments are categorized into three main strategies. The first strategy relies on the culturability of bacteria. The major limitation of this strategy is that it cannot detect viable but nonculturable (VBNC) bacteria. As the second strategy, based on the metabolic activity of bacteria, VBNC bacteria can be detected. However, VBNC bacteria sometimes can enter a dormant state that allows them to silence reproduction and metabolism; therefore, they cannot be detected based on culturability and metabolic activity. In order to overcome this drawback, viability assessments based on membrane integrity (third strategy) have been developed. However, these techniques generally require multiple steps, bulky machines, and laboratory technicians to conduct the tests, making them less attractive and popular applications. With significant advances in microfluidic technology, these limitations of current technologies for viability assessment can be improved. This review summarized and discussed the advances, challenges, and future perspectives of current methods for the viability assessment of bacterial pathogens.

Functionalization of Multi-Walled Carbon Nanotubes Changes Their Antibiofilm and Probiofilm Effects on Environmental Bacteria.

Releasing multi-walled carbon nanotubes (MWCNTs) into ecosystems affects the biofilm formation and metabolic activity of bacteria in aquatic and soil environments. Pristine (pMWCNTs), oleophilic (oMWCNTs), hydrophilic (hMWCNTs), and carboxylated (cMWCNTs) carbon nanotubes were used to investigate their effects on bacterial biofilm. A pronounced probiofilm effect of modified MWCNTs was observed on the Gram-negative bacteria of Pseudomonas fluorescens C2, Acinetobacter guillouiae 11 h, and Alcaligenes faecalis 2. None of the studied nanomaterials resulted in the complete inhibition of biofilm formation. The complete eradication of biofilms exposed to MWCNTs was not observed. The functionalization of carbon nanotubes was shown to change their probiofilm and antibiofilm effects. Gram-negative bacteria were the most susceptible to destruction, and among the modified MWCNTs, oMWCNTs had the greatest effect on biofilm destruction. The number of living cells in the biofilms was assessed by the reduction of XTT, and metabolic activity was assessed by the reduction of resazurin to fluorescent resorufin. The biofilms formed in the presence of MWCNTs reduced tetrozolium to formazan more actively than the control biofilms. When mature biofilms were exposed to MWCNTs, dehydrogenase activity decreased in Rhodococcus erythropolis 4-1, A. guillouiae 11 h, and A. faecalis 2 in the presence of pMWCNTs and hMWCNTs, as well as in A. guillouiae 11 h exposed to cMWCNTs. When mature biofilms were exposed to pMWCNTs, hMWCNTs, and cMWCNTs, the metabolism of cells decreased in most strains, and oMWCNTs did not have a pronounced inhibitory effect. The antibiofilm and probiofilm effects of MWCNTs were strain-dependent.

A Combination of Novel Nucleic Acid Cross-Linking Dye and Recombinase-Aided Amplification for the Rapid Detection of Viable Salmonella in Milk.

Salmonella, as an important foodborne pathogen, can cause various diseases, such as severe enteritis. In recent years, various types of nucleicacid-intercalating dyes have been utilized to detect viable Salmonella. However, in principle, the performance of existing nucleic acid dyes is limited because they depend on the integrity of cell membrane. Herein, based on the metabolic activity of bacteria, a novel DNA dye called thiazole orange monoazide (TOMA) was introduced to block the DNA from dead bacteria. Recombinase-aided amplification (RAA) was then performed to detect viable Salmonella in samples. In this study, the permeability of TOMA to the cell membrane of Salmonella was evaluated via confocal laser scanning microscopy and fluorescence emission spectrometry. The limit of detection (LOD) of the TOMA–RAA method was 2.0 × 104 CFU/mL in pure culture. The feasibility of the TOMA–RAA method in detecting Salmonella was assessed in spiked milk. The LOD for Salmonella was 3.5 × 102 CFU/mL after 3 h of enrichment and 3.5 × 100 CFU/mL after 5 h of enrichment. The proposed TOMA–RAA assay has great potential to be applied to accurately detect and monitor foodborne pathogens in milk and its byproducts.

Activation Energy, Temperature Coefficient and Q10 Value Estimations of the Growth of 2,4-dinitrophenol-degrading Bacterium on 2,4-dinitrophenol

In addition to its use as a pesticide, the chemical compound known as 2,4-dinitrophenol (2,4-DNP) is also utilized in the creation of wood preservatives and colors. Symptoms of acute (short-term) exposure to 2,4-DNP in humans include nausea or vomiting, sweating, headaches, disorientation, and a loss of weight. This type of exposure occurs when the substance is consumed orally. There are a few different models that may be used to simulate the growth rate of microorganisms on a variety of different medium at a range of temperatures. These models can be found online. One of the models that is employed the most frequently is the Arrhenius model, in part because it has a limited number of parameters. The development and metabolic activities of bacteria on the substrates they are grown on are commonly influenced by temperature. Temperature can also affect the growth of germs. Microbes are extremely sensitive to changes in temperature because of their small size. A discontinuous apparent activation energy with a chevron-like graph was used in order to describe the growth of a 2,4-dinitrophenol-degrading bacterium on 2,4-dinitrophenol. The break point of the graph was set at 28.05 °C. This was done so that the development of the bacterium could be described. Following the conclusion of the regression analysis, two temperature ranges for activation were determined. These temperature ranges were 20-27 °C and 30-42 °C, and their associated activation energies were 41.72 and 84.72 kilojoules per mole, respectively. It was anticipated that the Q10 value would be 2.905 and that the theta value would be 1.11 when considering the temperature range that was considered (30-42 °C). Due to the all-encompassing scope of this study, it is particularly useful for forecasting the effect of temperature on the breakdown and fate of 2,4-dinitrophenol during bioremediation.

Nitrogen removal performance, and microbial community structure of water and its association with nitrogen metabolism of an ecological engineering pond aquaculture system

The ecological engineering pond aquaculture system was promoted in China in recent years as it can save water and reduce pollution. In the present study, an ecological engineering pond aquaculture system was established, consisting of a drainage ditch, a settling pond, an aeration pond, a filter dam, eco-ponds, and fish ponds for tilapia farming. Water from different ponds were sampled and sequenced by Illumina sequencing, and then the microbial communities were analyzed. The metabolic activity of bacteria in the water samples was tested using Biolog EcoPlates. The concentrations of total nitrogen (TN), ammonia-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), and total phosphorus (TP) in water after treatment by the system were 0.71 ± 0.19, 0.48 ± 0.15, 0.51 ± 0.21, 0.03 ± 0.01, and 0.04 ± 0.01 mg/L, respectively. All the units of the system could remove TN in water. Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, and Planctomycetes were the dominant phyla in the water of the system. The genera Candidatus Aquiluna and Dechloromonas positively correlated with the microbial metabolic activity of organic nitrogen and NH4-N concentrations in water, which could be the functional bacteria for nitrogen removal. Several genera showed positive correlation with the TN and NH4-N concentrations of water and were probably involved in nitrogen cycling of the system. Our data indicated that the ecological engineering pond aquaculture system notably improves water quality and alters the microbial populations. The results supply substantial information on the functional microbiota for nitrogen removal from freshwater aquaculture ecosystems.

Self-Healing of Cementitious Materials via Bacteria: A Theoretical Study

Cracks on the surface of cementitious composites represent an entrance gate for harmful substances—particularly water—to devastate the bulk of material, which results in lower durability. Autogenous crack-sealing is a significantly limited mechanism due to a combination of the hydration process and calcite nucleation, and self-healing cementitious composites are a research area that require a great deal of scientific effort. In contrast to time-consuming experiments (e.g., only the preparation of an applicable bare concrete sample itself requires more than 28 days), appropriately selected mathematical models may assist in the deeper understanding of self-healing processes via bacteria. This paper presents theoretically oriented research dealing with the application of specific bacteria (B. pseudofirmus) capable of transforming available nutrients into calcite, allowing for the cracks on the surfaces of cementitious materials to be repaired. One of the principal objectives of this study is to analyze the sensitivity of the bacterial growth curves to the system parameters within the context of the logistic model in the Monod approach. Analytically calculated growth curves for various parameters (initial inoculation concentration, initial nutrition content, and metabolic activity of bacteria) are compared with experimental data. The proposed methodology may also be applied to analyze the growth of microorganisms of nonbacterial origin (e.g., molds, yeasts).

The oral microbiome, nitric oxide and exercise performance

The human microbiome comprises ∼1013–1014 microbial cells which form a symbiotic relationship with the host and play a critical role in the regulation of human metabolism. In the oral cavity, several species of bacteria are capable of reducing nitrate to nitrite; a key precursor of the signaling molecule nitric oxide. Nitric oxide has myriad physiological functions, which include the maintenance of cardiovascular homeostasis and the regulation of acute and chronic responses to exercise. This article provides a brief narrative review of the research that has explored how diversity and plasticity of the oral microbiome influences nitric oxide bioavailability and related physiological outcomes. There is unequivocal evidence that dysbiosis (e.g. through disease) or disruption (e.g. by use of antiseptic mouthwash or antibiotics) of the oral microbiota will suppress nitric oxide production via the nitrate-nitrite-nitric oxide pathway and negatively impact blood pressure. Conversely, there is preliminary evidence to suggest that proliferation of nitrate-reducing bacteria via the diet or targeted probiotics can augment nitric oxide production and improve markers of oral health. Despite this, it is yet to be established whether purposefully altering the oral microbiome can have a meaningful impact on exercise performance. Future research should determine whether alterations to the composition and metabolic activity of bacteria in the mouth influence the acute responses to exercise and the physiological adaptations to exercise training.

Intercropping Pinto Peanut in Litchi Orchard Effectively Improved Soil Available Potassium Content, Optimized Soil Bacterial Community Structure, and Advanced Bacterial Community Diversity

Intercropping is widely used in agricultural production due to its capability of raising land productivity and providing an opportunity to achieve sustainable intensification of agriculture. In this study, soil samples from 10 to 20 cm depth of intercropping Pinto peanut in litchi orchard and litchi monoculture mode were established to determine soil attributes, enzyme activities, as well as the effect on soil bacterial diversity. On this basis, 16S rRNA V4-V5 region of soil bacterial communities in litchi/Pinto peanut intercropping (LP) mode and litchi monoculture mode (CK) was detected by the Illumina MiSeq sequencing platform. The results showed that the content of available potassium (AK) in LP was significantly higher than that in CK by 138.9%, and the content of available nitrogen (AN) in LP was significantly lower than that in CK by 19.6%. The soil enzyme activities were higher in LP as a whole, especially sucrase (SC) and acid protease (PT) were significantly higher by 154.4 and 76.5%, respectively. The absolute abundance and alpha diversity of soil microbiota were significantly higher in the intercropping group. Most importantly, endemic species with a significant difference in LP was higher by ~60 times compared to CK treatment. In the aspect of soil bacterial community structure, the dominant phyla of the two groups were Acidobacteria, Proteobacteria, Chloroflexi, and Actinobacteria. At the genus level, the absolute abundance of Flavobacterium and Nitrososphaera was significantly higher by 79.20 and 72.93%, respectively, while that of Candidatus_Koribacter was significantly lower with an amplitude of 62.24% in LP than in CK. Furthermore, the redundancy analysis (RDA) suggested that AK, which was highly associated with the dominant genera and phyla, is the vitally dominating environmental factors in LP groups, while in CK groups, it is AN and pH. In addition, PICRUSt2 analysis indicated that intercropping improved the metabolic activity of bacteria which can be correlated to the resistance of litchi root systems to soil-borne diseases. Overall, this study is expected to provide a theoretical basis and technical support for the healthy intercropping cultivation of litchi.