Bacterial Growth Research Articles

Successful pregnancy with intracytoplasmic sperm injection after bacterial contamination of embryo culture in in vitro fertilization: a case report

BackgroundBacterial infection of embryo culture medium is rare but may be detrimental. The main source of embryo culture contamination is semen. Assisted reproduction centers currently lack consensus regarding the methods for preventing and managing embryo culture infection. In our recent case, a successful pregnancy was achieved with intracytoplasmic sperm injection after failed conventional in vitro fertilization owing to bacterial contamination.Case presentationWe present a case report of two consecutive in vitro fertilization–intracytoplasmic sperm injection cycles with photo and video documentation of the bacterial growth. A 36-year-old Hungarian woman and her 37-year-old Hungarian partner came to our department. They had two normal births followed by 2 years of infertility. The major causes of infertility were a closed fallopian tube and asthenozoospermia. Bacterial infection of the embryo culture medium was observed during in vitro fertilization and all oocytes degenerated. The source was found to be the semen. To prevent contamination, intracytoplasmic sperm injection was used for fertilization in the subsequent cycle. Intracytoplasmic bacterial proliferation was observed in one of the three fertilized eggs, but two good-quality embryos were successfully obtained. The transfer of one embryo resulted in a successful pregnancy and a healthy newborn was delivered.ConclusionIntracytoplasmic sperm injection may be offered to couples who fail conventional in vitro fertilization treatment owing to bacteriospermia, as it seems to prevent infection of the embryo culture. Even if bacterial contamination appears, our case encourages us to continue treatment. Nevertheless, the development of new management guidelines for the prevention and management of bacterial contamination is essential.

Polydopamine Nanocarriers with Cascade-Activated Nitric Oxide Release Combined Photothermal Activity for the Therapy of Drug-Resistant Bacterial Infections.

Antibiotic abuse leads to increased bacterial resistance, and the surviving planktonic bacteria aggregate and secrete extracellular polymers to form biofilms. Conventional antibacterial agents find it difficult to penetrate the biofilm, remove the bacteria wrapped in it, and produce an excellent therapeutic effect. In this study, a dual pH- and NIR-responsive nanocomposite (A-Ca@PDA) was developed to remove drug-resistant bacteria through a cascade of catalytic nitric oxide (NO) release and photothermal clearance. NO can melt in the outer package of the biofilm, facilitating the nanocomposites to have better permeability. Thermal therapy further inhibits the growth of planktonic bacteria. The locally generated high temperature and the burst release of NO together aggravate the biofilm collapse and bacterial death after NIR irradiation. The nanocomposites achieved a remarkable photothermal conversion efficiency of 47.5%, thereby exhibiting significant advancements in energy conversion. The nanocomposites exhibited remarkable efficacy in inhibiting multidrug-resistant (MDR) Escherichia coli and MDR Staphylococcus aureus, thus achieving an inhibition rate of >90%. Moreover, these nanocomposites significantly improved the wound-healing process in the MDR S. aureus-infected mice. Thus, this novel nanocomposite offers a novel strategy to combat drug-resistant bacterial infections.

Unraveling the mechanism of interaction: accelerated phenanthrene degradation and rhizosphere biofilm/iron plaque formation influenced by phenolic root exudates.

Phenolic root exudates (PREs) secreted by wetland plants facilitate the accumulation of iron in the rhizosphere, potentially providing the essential active iron required for the generation of enzymes that degrade polycyclic aromatic hydrocarbon, thereby enhancing their biodegradation. However, the underlying mechanisms involved are yet to be elucidated. This study focuses on phenanthrene (PHE), a typical polycyclic aromatic hydrocarbon pollutant, utilizing representative PREs from wetland plants, including p-hydroxybenzoic, p-coumaric, caffeic, and ferulic acids. Using hydroponic experiments, 16S rRNA sequencing, and multiple characterization techniques, we aimed to elucidate the interaction mechanism between the accelerated degradation of PHE and the formation of rhizosphere biofilm/iron plaque influenced by PREs. Although all four types of PREs altered the biofilm composition and promoted the formation of iron plaque on the root surface, only caffeic acid, possessing a similar structure to the intermediate metabolite of PHE (catechol), could accelerate the PHE degradation rate. Caffeic acid, notable for its catechol structure, plays a significant role in enhancing PHE degradation through two main mechanisms: (a) it directly boosts PHE co-metabolism by fostering the growth of PHE-degrading bacteria, specifically Burkholderiaceae, and by facilitating the production of the key metabolic enzyme catechol 1,2-dioxygenase (C12O) and (b) it indirectly supports PHE biodegradation by promoting iron plaque formation on root surfaces, thereby enriching free iron for efficient microbial synthesis of C12O, a crucial factor in PHE decomposition.

Targeted protein degradation in mycobacteria uncovers antibacterial effects and potentiates antibiotic efficacy

Proteolysis-targeting chimeras (PROTACs) represent a new therapeutic modality involving selectively directing disease-causing proteins for degradation through proteolytic systems. Our ability to exploit targeted protein degradation (TPD) for antibiotic development remains nascent due to our limited understanding of which bacterial proteins are amenable to a TPD strategy. Here, we use a genetic system to model chemically-induced proximity and degradation to screen essential proteins in Mycobacterium smegmatis (Msm), a model for the human pathogen M. tuberculosis (Mtb). By integrating experimental screening of 72 protein candidates and machine learning, we find that drug-induced proximity to the bacterial ClpC1P1P2 proteolytic complex leads to the degradation of many endogenous proteins, especially those with disordered termini. Additionally, TPD of essential Msm proteins inhibits bacterial growth and potentiates the effects of existing antimicrobial compounds. Together, our results provide biological principles to select and evaluate attractive targets for future Mtb PROTAC development, as both standalone antibiotics and potentiators of existing antibiotic efficacy.

Lack of the IFN-γ signal leads to lethal Orientia tsutsugamushi infection in mice with skin eschar lesions.

Scrub typhus is an acute febrile disease due to Orientia tsutsugamushi (Ot) infection and can be life-threatening with organ failure, hemorrhage, and fatality. Yet, little is known as to how the host reacts to Ot bacteria at early stages of infection; no reports have addressed the functional roles of type I versus type II interferon (IFN) responses in scrub typhus. In this study, we used comprehensive intradermal (i.d.) inoculation models and two clinically predominant Ot strains (Karp and Gilliam) to uncover early immune events. Karp infection induced sequential expression of Ifnb and Ifng in inflamed skin and draining lymph nodes at days 1 and 3 post-infection. Using double Ifnar1-/-Ifngr1-/- and Stat1-/- mice, we found that deficiency in IFN/STAT1 signaling resulted in lethal infection with profound pathology and skin eschar lesions, which resembled to human scrub typhus. Further analyses demonstrated that deficiency in IFN-γ, but not IFN-I, resulted in impaired NK cell and macrophage activation and uncontrolled bacterial growth and dissemination, leading to metabolic dysregulation, excessive inflammatory cell infiltration, and exacerbated tissue damage. NK cells were found to be the major cellular source of innate IFN-γ, contributing to the initial Ot control in the draining lymph nodes. In vitro studies with dendritic cell cultures revealed a superior antibacterial effect offered by IFN-γ than IFN-β. Comparative in vivo studies with Karp- and Gilliam-infection revealed a crucial role of IFN-γ signaling in protection against progression of eschar lesions and Ot infection lethality. Additionally, our i.d. mouse models of lethal infection with eschar lesions are promising tools for immunological study and vaccine development for scrub typhus.

Propionate prevents loss of the PDIM virulence lipid in Mycobacterium tuberculosis.

Phthiocerol dimycocerosate (PDIM) is an essential virulence lipid of Mycobacterium tuberculosis. In vitro culturing rapidly selects for spontaneous PDIM-negative mutants that have attenuated virulence and increased cell wall permeability, thus impacting the relevance of experimental findings. PDIM loss can also reduce the efficacy of the BCG Pasteur vaccine. Here we show that vancomycin susceptibility can rapidly screen for M. tuberculosis PDIM production. We find that metabolic deficiency of methylmalonyl-CoA impedes the growth of PDIM-producing bacilli, selecting for PDIM-negative variants. Supplementation with odd-chain fatty acids, cholesterol or vitamin B12 restores PDIM-positive bacterial growth. Specifically, we show that propionate supplementation enhances PDIM-producing bacterial growth and selects against PDIM-negative mutants, analogous to in vivo conditions. Our study provides a simple approach to screen for and maintain PDIM production, and reveals how discrepancies between the host and in vitro nutrient environments can attenuate bacterial pathogenicity.

Positive effects of Moringa oleifera and Moringa stenopetala seed and leaf extracts against selected bacteria

Moringa oleifera is hailed as the “miracle tree” for its impressive catalog of nutritional, medicinal, and water purification benefits. A (sub)tropical plant with a rapid growth rate (3–5 m in a single season), Moringa has proven beneficial in multiple ways in developing regions around the world. In addition to its high nutrient content and water clarifying properties, Moringa seed and leaf extracts have shown potential as natural antibacterial agents. Based on this, we anticipated that extracts from multiple species of Moringa would exhibit potentially useful antibacterial properties against a range of bacterial species. To explore this, both disk diffusion and minimum inhibitory concentration (MIC) culture techniques were employed to assess the inhibitory effects of seed and leaf extracts from M. oleifera and M. stenopetala against species of bacteria commonly used in research and teaching laboratories. Aqueous seed extracts from both Moringa species showed broad-spectrum activity but were especially effective at inhibiting the growth of Gram-positive bacteria, including species of Staphylococcus, Streptococcus, and Bacillus. Moringa leaf extracts also exhibited antibacterial activity, with ethanolic leaf extracts showing greater efficacy than aqueous leaf extracts in disk-diffusion assays. Temporary acidification (1 h at pH 2) of Moringa seed and leaf extracts had a detrimental effect on their antibacterial activity. MIC assays using Moringa leaf extracts also showed more pronounced inhibition of Gram-positive bacteria (MIC = 12.5% v/v) versus Gram-negative species (MIC = 25% v/v). These results are of particular relevance in tropical areas where pharmaceutical drugs are scarce but Moringa is widely available and often used as a nutritional supplement. Moreover, the rising threat of multi-drug resistant pathogens lends greater importance to the study of antibacterial plant products that ultimately may find application in the clinical setting.

Widespread horizontal gene transfer between plants and bacteria

Abstract Plants host a large array of commensal bacteria that interact with the host. The growth of both bacteria and plants is often dependent on nutrients derived from the cognate partners, and the bacteria fine-tune host immunity against pathogens. This ancient interaction is common in all studied land plants and is critical for proper plant health and development. We hypothesized that the spatial vicinity and the long-term relationships between plants and their microbiota may promote cross-kingdom horizontal gene transfer (HGT), a phenomenon that is relatively rare in nature. To test this hypothesis we analyzed the Arabidopsis thaliana genome and its extensively sequenced microbiome to detect events of horizontal transfer of full length genes that transferred between plants and bacteria. Interestingly, we detected 75 unique genes that were horizontally transferred between plants and bacteria. Plants and bacteria exchange in both directions genes that are enriched in carbohydrate metabolism functions, and bacteria transferred to plants genes that are enriched in auxin biosynthesis genes. Next we provided a proof of concept for the functional similarity between a horizontally transferred bacterial gene and its Arabidopsis homologue in planta. The Arabidopsis DET2 gene is essential for biosynthesis of the brassinosteroid phytohormones and loss-of-function of the gene leads to dwarfism. We found that expression of the DET2 homologue from Leifsonia bacteria of the Actinobacteria phylum in the Arabidopsis det2 background complements the mutant, and leads to normal plant growth. Together, these data suggest that cross-kingdom horizontal gene transfer events shape the metabolic capabilities and interactions between plants and bacteria.

Transcriptomic and metabolomic correlation analysis: effect of initial SO2 addition on higher alcohol synthesis in Saccharomyces cerevisiae and identification of key regulatory genes

IntroductionHigher alcohols are volatile compounds produced during alcoholic fermentation that affect the quality and safety of the final product. This study used a correlation analysis of transcriptomics and metabolomics to study the impact of the initial addition of SO2 (30, 60, and 90 mg/L) on the synthesis of higher alcohols in Saccharomyces cerevisiae EC1118a and to identify key genes and metabolic pathways involved in their metabolism.MethodsTranscriptomics and metabolomics correlation analyses were performed and differentially expressed genes (DEGs) and differential metabolites were identified. Single-gene knockouts for targeting genes of important pathways were generated to study the roles of key genes involved in the regulation of higher alcohol production.ResultsWe found that, as the SO2 concentration increased, the production of total higher alcohols showed an overall trend of first increasing and then decreasing. Multi-omics correlation analysis revealed that the addition of SO2 affected carbon metabolism (ko01200), pyruvate metabolism (ko00620), glycolysis/gluconeogenesis (ko00010), the pentose phosphate pathway (ko00030), and other metabolic pathways, thereby changing the precursor substances. The availability of SO2 indirectly affects the formation of higher alcohols. In addition, excessive SO2 affected the growth of the strain, leading to the emergence of a lag phase. We screened the ten most likely genes and constructed recombinant strains to evaluate the impact of each gene on the formation of higher alcohols. The results showed that ADH4, SER33, and GDH2 are important genes of alcohol metabolism in S. cerevisiae. The isoamyl alcohol content of the EC1118a-ADH4 strain decreased by 21.003%; The isobutanol content of the EC1118a-SER33 strain was reduced by 71.346%; and the 2-phenylethanol content of EC1118a-GDH2 strain was reduced by 25.198%.ConclusionThis study lays a theoretical foundation for investigating the mechanism of initial addition of SO2 in the synthesis of higher alcohols in S. cerevisiae, uncovering DEGs and key metabolic pathways related to the synthesis of higher alcohols, and provides guidance for regulating these mechanisms.

Structural, bacteriostatic and antioxidant profiling of zinc oxide nanoparticles

The bacterial infection and generation of free radicals inside the body are serious threats to human health globally and researchers show their serious concern for these issues. Thus, in this study, an attempt has been made to control bacterial growth and scavenge the ABTs free radicals. ZnO-NPs were synthesized by an economical method, and the characteristics were investigated using a range of analytical techniques. These methods included FTIR, SEM, EDX, XRD, and TEM. The agar-well diffusion process has been followed to control the growth of selected bacteria and the ABTs free radicals have been scavenged using a standard protocol. The effect of the dose on both activities has been studied where the results has explore that the effectiveness of the ZnO-NPs gradually increases with increasing concentration.

Unveiling antibiofilm potential: proteins from Priestia sp. targeting Staphylococcus aureus biofilm formation.

Staphylococcus aureus is the etiologic agent of many nosocomial infections, and its biofilm is frequently isolated from medical devices. Moreover, the dissemination of multidrug-resistant (MDR) strains from this pathogen, such as methicillin-resistant S. aureus (MRSA) strains, is a worldwide public health issue. The inhibition of biofilm formation can be used as a strategy to weaken bacterial resistance. Taking that into account, we analysed the ability of marine sponge-associated bacteria to produce antibiofilm molecules, and we found that marine Priestia sp., isolated from marine sponge Scopalina sp. collected on the Brazilian coast, secretes proteins that impair biofilm development from S. aureus. Partially purified proteins (PPP) secreted after 24 hours of bacterial growth promoted a 92% biofilm mass reduction and 4.0 µg/dL was the minimum concentration to significantly inhibit biofilm formation. This reduction was visually confirmed by light microscopy and Scanning Electron Microscopy (SEM). Furthermore, biochemical assays showed that the antibiofilm activity of PPP was reduced by ethylenediaminetetraacetic acid (EDTA) and 1,10 phenanthroline (PHEN), while it was stimulated by zinc ions, suggesting an active metallopeptidase in PPP. This result agrees with mass spectrometry (MS) identification, which indicated the presence of a metallopeptidase from the M28 family. Additionally, whole-genome sequencing analysis of Priestia sp. shows that gene ywad, a metallopeptidase-encoding gene, was present. Therefore, the results presented herein indicate that PPP secreted by the marine Priestia sp. can be explored as a potential antibiofilm agent and help to treat chronic infections.

The antimicrobial synergy of polymer based nanofiber mats reinforced with antioxidants intercalated layered double hydroxides as a potential active packaging material

Abstract Perishable food post-harvest loss is a major global concern, and research is currently concentrated on creating active packaging materials. This research is focused in multiple antioxidants intercalated Layered Double Hydroxides (LDH) that are combined in one matrix, and their overall effect that defines as synergism, which successfully preserves perishable food by releasing antioxidants slowly. For this purpose, a hybrid LDH material of ascorbic-LDH, salicylic-LDH, and citric-LDH was synthesized, characterized and incorporate into electrospun nanofiber mat to be used as a potential active packaging material. Antioxidants intercalated Mg/Al LDH was synthesized and successfully characterized by PXRD, FTIR, XPS, Raman, SEM and EDS. The shifts in the LDHs' peaks in PXRD indicated the successful incorporation of antioxidants into LDH. FTIR, Raman and XPS data clearly indicated the establishment of metal-oxygen bonds by observing the characteristic peaks. Morphological features and layered structure were clearly observed by SEM images. Antioxidants were slowly released from LDHs, and it was evaluated for time intervals up to 24 hrs. The hybrid LDH material exhibited the highest antioxidant activity with an IC50 value of 132.5µg/mL, where 234.1, 354.5, and 402.2µg/mL were reported for ascorbic-LDH, salicylic-LDH, and citric-LDH respectively. The hybrid LDH material incorporated electrospun mats showed the best antibacterial activity against the tested bacteria and clearly evidenced the synergistic activity of the combination of the nanohybrids. It has showed a minimal bacterial growth compared to other control samples (∼2.41 log CFU/mL). The shelf life of cherry tomatoes was studied at different physiochemical parameters with and without hybrid LDH material incorporated electrospun mats. The mat showed an extended shelf life of 42 days for cherry tomatoes, whereas the control sample showed a shelf life of 17 days. It is concluded that hybrid LDH material exhibited synergistic performance and the best antioxidant activity when comparing with mono LDH materials.

Screening of enhanced biohydrogen production from anaerobic fermentation amended with nano-sized barium ferrite supported by aluminum oxide

Anaerobic fermentation has attracted wide attention to effectively reduce carbon footprint and alleviate potential energy shortages, which is being regarded as a sustainable and promising technology to obtain high biohydrogen production from widespread organic wastes. However, biohydrogen commercial uptake is now dominantly inhibited by the low hydrogen yield and process instability. In this work, Al2O3/BaFe2O4 nanoparticles (NPs) are successfully applied to anaerobic fermentation for investigating their effects on hydrogen yield, activity of bacteria and microbial community structure. The benefits of Al2O3/BaFe2O4 NPs with respect to microbial metabolism, reactivity of enzymes and process optimization are systematically researched through batch experiments. In addition, various characterizations are used to verify the physical and chemical properties of Al2O3/BaFe2O4 NPs. The results show that the activity of hydrogenases and microbe metabolism can be significantly inhibited by excess addition of Al2O3/BaFe2O4 NPs (150 mg/L and 200 mg/L) while the optimum addition 100 mg/L of Al2O3/BaFe2O4 NPs can boost the biohydrogen yield by 49% via facilitating microorganism growth and enhancing key enzymatic activities, which indicate that the Al2O3/BaFe2O4 NPs display a beneficial influence on electron transfer efficiency and process stability. The existence of Fe3+, Al3+and Ba2+ derived from the corrosion of Al2O3/BaFe2O4 NPs by organic acids synergistically improve the microbial transmembrane transportation and substrate utilization, which contribute to higher conversion rate of glucose into acetate, butyrate and H2. Meanwhile, the complementary functions of Fe3+ and Al3+ can powerfully shorten the lag phase and promote the glycolysis, which finally accelerate the dark fermentation process. Compared with the control group, Clostridium_sensu_stricto_1 is selectively enriched by the addition of Al2O3/BaFe2O4 NPs, which keep heavily involved in the synthesis of H2. On balance, this study provides an effective strategy to enhance hydrogen productivity and maintain process stability, which offer the valuable information for the sustainable utilization of sewage sludge.

OPTIMIZATION OF PHYSIOLOGICAL PARAMETERS FOR EXOPOLYSACCHARIDE PRODUCTION USING Pseudomonas aeruginosa MSSRFV42

Exopolysaccharides (EPS) are long-chain polysaccharides containing branched, repeating units of sugars or sugar derivatives such as glucose, fructose, mannose and galactose etc, which are secreted into their surrounding environment during the bacterial growth. Due to their unique properties and vast array of application, isolation and study of new EPS producing microbes is highly concerned issue. In the present study potent exopolysaccharide producing AB4 bacteria (Pseudomonas aeruginosa MSSRFV42) which was previously isolated and screened from marine sample was used. To increase the yield of exopolysaccharide significant physiological parameter were determined Submerged fermentation at pH 10 and temperature of 300C gave maximum yield of EPS after 72 hrs incubation using 1% inoculums in media containing 3.5% NaCl. Outcome of this study will definitely contribute in the elucidation components of AB4 EPS in various industries . Keywords: EPS, Pseudomonas aeruginosa, Optimization

A Continuous Plug-Flow Anaerobic-Multistage Anoxic/Aerobic Process Treating Low-C/N Domestic Sewage: Nutrient Removal, Greenhouse Gas Emissions, and Microbial Community Analysis

The anaerobic-multistage anoxic/aerobic (A-MAO) process has shown good potential for advanced nitrogen removal in recent years, but its greenhouse gas emissions still need to be fully explored. The effects of the influent distribution and external carbon source sodium acetate on nutrient removal, greenhouse gas emissions, and the microbial community structure in a continuous plug-flow A-MAO reactor fed with real low C/N ratio domestic sewage were investigated. The results showed that altering the allocation of carbon source resulted in average chemical oxygen demand (COD) and total nitrogen (TN) concentration in effluent reduced to 26.10 ± 4.86 and 6.65 ± 1.73 mg/L, respectively. Both operations reduced the emission rate of greenhouse gas. While the addition of external car-bon sources leaded to lower N2O emission rates and higher CO2 and CH4 emission rates. The addition of sodium acetate facilitated nitrification and denitrification processes, thereby leading to a reduction in N2O production. Meanwhile, it spurred the growth of methanogenic bacteria and heterotrophic microorganisms, thus boosting the production of CO2 and CH4. Influent distribution promoted the increase of Bacteroidota, Chloroflexi and Acidobacteriota of the reactor. The enrichment of typical hydrolytic bacteria and glycogen accumulating organisms (GAOs) increased the utilization efficiency of carbon sources in the system after the addition of sodium acetate. The significant increase of typical denitrifying bacteria (DNBs) Azospira reduced the N2O emission during heterotrophic denitrification process, which was considered to be an important functional genus for increasing nitrogen loss in this system. The rational utilization of carbon source makes the difference in metabolism function. The study provides a valuable strategy for comprehensively evaluating the pollutant removal and greenhouse gas emission reduction from the A-MAO process.

Antibacterial Activity by Diffusion and Dilution Methods of Liquid Smoke Cocos nucifera L.

Introduction: Liquid smoke is a product that obtained industrially from coconut shell through pyrolysis process at 400°C for 2,5 hours and redestillation to obtain grade 1 liquid smoke. Coconut shell liquid smoke contains chemical compounds, namely phenol, which has been researched to act as a disinfectant that has broad spectrum antibacterial activity against gram positive and gram negative bacteria. Method: This study aims to determine the potential of cocos nucifera L. liquid smoke as an antibacterial against Staphylococcus aureus and Methicillin-resistant staphylococcus aureus (MRSA) bacteria using diffusion and dilution methods. The concentrations used were 100%, 80%, 60%, 40%, 35%, 30%, 15%, 10%, 7%, 5%. As positive control was used Tetracycline 25 ppm. Results: Liquid smoke has the potential to inhibit the growth of both bacteria. The effective concentration to inhibit the growth of S. aureus at 40% concentration and MRSA at 80% concentration. The MIC value of liquid smoke against S. aureus is 0,78%, while on MRSA 3,12%. The MBC of S. aureus and MRSA bacteria at concentrations 1,56% and 6,25%. Staphylococcus aureus has higher sensitivity to Cocos nucifera L. grade 1 liquid smoke than MRSA bacteria. Conclusion: Cocos nucifera L. liquid smoke has antibacterial activity against Staphylococcus aureus and MRSA at effective concentrations of 40% and 80%. The MIC value of S. aureus is 0,78%, while MRSA is 3,12%. The MBC of S. aureus and MRSA bacteria at concentrations 1,56% and 6,25%. Keywords: antibacterial, liquid smoke, phenol, Cocos nucifera L.

Investigation of a novel biofilm model close to the original oral microbiome

A more optimized culture medium used in vitro to mimic the bacterial composition of original oral flora as similar as possible remains difficult at present, and the goal of this study is to develop a novel oral biofilm medium to restore the original oral microbiome. Firstly, we conducted a systematic literature review by searching PubMed and summarized the current reported culture media in vitro. Seven culture media were found. We used mixed saliva as the origin of oral species to compare the effects of the above media in culturing oral multispecies biofilms. Results indicated that among the seven media brain heart infusion containing 1% sucrose (BHIs) medium, PG medium, artificial saliva (AS) medium, and SHI medium could obviously gain large oral biofilm in vitro. The nutrients contained in different culture media may be suitable for the growth of different oral bacteria; therefore, we optimized several novel media accordingly. Notably, results of crystal violet staining showed that the biofilm cultured in our modified artificial saliva (MAS) medium had the highest amount of biofilm biomass. 16S rRNA gene sequencing showed that the operational taxonomic units (OTUs) and Shannon index of biofilm cultured in MAS medium were also the highest among all the tested media. More importantly, the 16S rRNA gene sequencing analysis indicated that the biofilm cultured in MAS medium was closer to the original saliva species. Besides, biofilm cultured by MAS was denser and produced more exopolysaccharides. MAS supported stable biofilm formation on different substrata. In conclusion, this study demonstrated a novel MAS medium that could culture oral biofilm in vitro closer to the original oral microbiome, showing a good application prospect.Key points• We compare the effects of different media in culturing oral biofilms• A novel modified artificial saliva (MAS) medium was obtained in our study• The MAS medium could culture biofilm that was closer to oral microbiome

Aquaculture and Aeromonas hydrophila: a complex interplay of environmental factors and virulence

AbstractAquaculture faces significant challenges due to bacterial pathogens like Aeromonas hydrophila, which can severely impact production and fish health. Understanding the relationship between environmental factors, host susceptibility, and bacterial virulence is crucial for effectively managing and mitigating the risks associated with A. hydrophila in aquaculture systems. A. hydrophila, found ubiquitously in aquatic environments, possesses various virulence factors that enhance its pathogenicity. These factors are closely linked to environmental conditions, such as temperature and pH, which play pivotal roles in bacterial growth, survival, and pathogenic potential. Fluctuations in temperature and pH significantly influence A. hydrophila’s metabolic activity and growth rate, thereby modulating its virulence and overall pathogenicity. Ammonia, a byproduct of aquatic organism metabolism and organic matter decomposition, can accumulate to toxic levels in aquaculture settings, compromising fish health and immune function. Elevated ammonia concentrations worsen A. hydrophila infections by compromising host immunity and creating favorable conditions for bacterial proliferation. Oxygen concentration, host signals, and diet formulation are significantly impacting the susceptibility of aquatic organisms to infection. These factors are the most crucial in shaping the ecology, physiology, and pathogenicity of A. hydrophila in aquaculture. There is limited information on how these environmental factors modulate the virulence genes of such important fish pathogens. The knowledge of A. hydrophila virulence and its interplay with environmental factors paves the way for developing strategies to prevent and control diseases in aquaculture.

Highly effective removal of nitrate from saline wastewater by glucose-enhanced sulfur autotrophic system

The denitrification performance of the elemental sulfur autotrophic denitrification (S0AD) system requires improvements to broaden its applicability for treating nitrate (NO3−-N) wastewater contaminated with high salinity. Therefore, this work investigated the denitrification performance and mechanism of the glucose-enhanced (C:N ratio = 1) S0AD system with saline wastewater (0–15 g/L). The results showed that by adding glucose, our research successfully constructed the elemental sulfur autotrophic/heterotrophic denitrification (HS0AD) system, which showed a stable NO3−-N removal efficiency above 95 % and lower effluent sulfate generation. The NO3−-N removal efficiency of the HS0AD system was over 95.62 % with wastewater containing different salinity levels. With increasing salinity, the glucose utilization efficiency increased from 65.23 % to 74.35 %. Microbial community analysis showed that adding glucose promoted the growth of the Proteobacteria phylum and stimulated its activity under salt stress. High salinity (≥10 g/L) reduced the microbial diversity at the genus level. However, the growth of salt-tolerant denitrifying bacteria (Thiobacillus and Vitellibacter) still enabled efficient denitrification performance with the system. These microorganisms can resist high salinity stresses by releasing proteins. All results indicated that the glucose-enhanced system shows great nitrate removal potential, even under salt stress. These conclusions provide a theoretical basis for applying a synergistic system to treat saline wastewater contaminated with NO3−-N.

Immunoenhancing and antioxidant potentials of kimchi, an ethnic food from Korea, as a probiotic and postbiotic food

Kimchi, the traditional lactic fermented vegetables from Korea, is globally praised for its potential as a functional food owing to the presence of beneficial microorganisms known as probiotics. However, the serving of kimchi in traditional Korean dishes often involves cooking at high temperature, thus killing the probiotics. Recently, non-viable or inactivated microorganisms and their metabolites, known as postbiotics, were shown to confer health benefits when consumed, thus giving rise to a novel potential of kimchi as a postbiotic food with health functionalities. The present study aimed to explore the potential of uncooked and cooked kimchi, both as a probiotic and postbiotic food, respectively, using an animal model. Mice were fed by AIN-76 diet enriched in 10% freeze-dried uncooked or cooked kimchi for 28 days prior to kill. Several parameters related to immune system and antioxidant were evaluated. Exposure of kimchi toward heat in steaming process killed the microorganisms in kimchi, but did not alter its antioxidant activity. Interestingly, the consumption of uncooked and cooked kimchi stimulated the growth of lactic acid bacteria in the intestine indifferently, as shown in the fecal matter. In addition, kimchi supplementation, either uncooked or cooked, increased the number of splenic lymphocytes and intestinal IgA, supporting the role of kimchi in the immune system. Furthermore, kimchi supplementation reduced the level of lipid peroxidation in the fecal matter, indicating its antioxidant activity in vivo. Taken together, the findings in this study suggest the potential of kimchi both as a probiotic and postbiotic food with antioxidant and immunoenhancing properties.