Effectiveness ofCyanothece spp. andCyanospira capsulata exocellular polysaccharides as antiadhesive agents for blocking attachment ofHelicobacter pylori to human gastric cells

Natural anti-adhesive components against pathogenic bacterial adhesion and infection in gastrointestinal tract: case studies of Helicobacter pylori, Salmonella enterica, Clostridium difficile, and diarrheagenic Escherichia coli

Antimicrobial resistance (AMR) poses a global public health concern. Recognizing the critical role of bacterial adhesion in pathogenesis of infection, anti-adhesive therapy emerges as a promising approach to impede initial bacterial attachment, thus preventing pathogenic colonization and infection. Natural anti-adhesive agents derived from food sources are generally safe and have the potential to inhibit the emergence of resistant bacteria. This comprehensive review explored diverse natural dietary components exhibiting anti-adhesive activities against several model enteric pathogens, including Helicobacter pylori, Salmonella enterica, Clostridium difficile, and three key diarrheagenic Escherichia coli (i.e., enterotoxigenic E. coli, enteropathogenic E. coli, and enterohemorrhagic E. coli). Investigating various anti-adhesive products will advance our understanding of current research of the field and inspire further development of these agents as potential nutraceuticals or adjuvants to improve the efficacy of conventional antibiotics.

Silver Nanoparticle Production by the Cyanobacterium Cyanothece sp.: De Novo Manipulation of Nano-Biosynthesis by Phytohormones

Background: Numerous cyanobacteria have the potential to reduce metallic ions to form pure metal nanoparticles in a green biosynthesis process. Aim: To investigate the production capacity of silver nanoparticles by the cyanobacterium Cyanothece sp. and to examine the effect of five different phytohormones, indole acetic acid, kinetin; gibberellic acid; abscisic acid; and methyl jasmonate, on this capacity. Methods: The cyanobacterial strain was grown for 60 days and the harvested cyanobacterium biomass was incubated with 0.1 mM of AgNO₃. Percentage conversion of Ag⁺ to Ag⁰ was calculated to indicate the AgNPs’ production capacity. Different concentrations of the five phytohormones were added to cultures and the AgNP production was monitored throughout different time intervals. Results: Cyanothece sp. biosynthesized spherical AgNPs (diameter range 70 to 140 nm, average diameter 84.37 nm). The addition of indole acetic acid and kinetin provoked the maximum conversion (87.29% and 55.16%, respectively) of Ag⁺ to Ag⁰, exceeding or slightly below that of the control (56%). Gibberellic and abscisic acids failed to elevate the Ag⁺ to Ag⁰ conversion rate (45.23% and 47.95%, respectively) above that of the control. Methyl jasmonate increased the Ag⁺ to Ag⁰ conversion rate to 90.29%, although nearly all the cyanobacterial cultures died at the end. Conclusion: Phytohormones could be used to induce or inhibit the green production of AgNPs with the cyanobacterium Cyanothece sp. This novel manipulation technique may have several applications in agriculture or biomedicine.

[Characteristics of gastric microbiota in children with Helicobacter pylori infection family history]

OBJECTIVE

To explore the characteristics of gastric microbiota in children with and without (Helicobacter pylori, H. pylori) infection who had family history of H. pylori infection.

METHODS

Mucosal biopsy samples of the gastric corpus and gastric antrum were collected during the gastroscope. And the gastric mucosa flora's information of the two groups of children were obtained after sample DNA extraction, PCR amplification of the 16S ribosomal DNA (rDNA) V3-V4 region, high-throughput sequencing and data processing. All the samples with family history of H. pylori infection were divided into two groups, the H. pylori infection group (n=18) and the H. pylori non-infection group (n=24). Then the α-, β-diversity and bacteria abundance of the gastric microbiota were compared between the H. pylori infection and non-infection groups at different taxonomic levels. The differential microbiota was found out by LEfSe analysis, and then the function of microbiota predicted using phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) method.

RESULTS

There was statistically significant difference in α-diversity (P < 0.05) between the two groups, indicating that the H. pylori non-infection group had higher microbial richness than the H. pylori infection group. Moreover, the β-diversity was significantly different as well (P < 0.05), which meant that the microbiota composition of the two groups was different. At the phyla level, Proteobacteria, Firmicutes, Bacteroides, Actinobacteria, and Fusobacteria were dominant in the two groups. At the genus level, Bacteroides, Prevotella, Streptococcus, and Neisseria, etc. were dominant in the H. pylori non-infected group. Meanwhile, Helicobacter and Haemophilus etc. were dominant in the H. pylori infected group. LEfSe analysis showed that the relative abundance of Bacteroides etc. at the genus level in the H. pylori non-infected group was significantly higher than that in the H. pylori infected group. Functional prediction showed that Bacteroides were positively correlated with amino acid and vitamin metabolism, mitogen-activated protein kinase (MAPK), mammalian target of rapamycin (mTOR) signaling pathway and ansamycin synthesis pathway.

CONCLUSION

The gastric microbiota between H. pylori positive and H. pylori negative in children with family history of H. pylori infection is significant different. Some gastric microbiota, such as Bacteroides, may have a potential relationship with H. pylori infection in children.

Surface activation of medical grade polyurethane for the covalent immobilization of an anti-adhesive biopolymeric coating

Hospital-acquired infections are still a major concern worldwide, being frequently related to bacterial biofilm formation on medical devices, and thus difficult to eradicate with conventional antimicrobial treatments. Therefore, infection-preventive solutions based on natural polymers are being investigated. Recently, a marine cyanobacterium-derived polymeric coating (CyanoCoating) has demonstrated great anti-adhesive potential when immobilized onto gold model substrates. In this work, we took this technology a step closer to an industrial application by covalently immobilizing CyanoCoating onto medical grade polyurethane (PU). This immobilization was developed through the introduction of linkable moieties onto a PU inert surface using different pre-treatments. Besides the application of the polydopamine (pDA) linker layer, other processes frequently found in industrial settings, such as atmospheric plasma (using O2 or N2 as reactive gases) and ozone surface activations, were evaluated. From all the pre-treatments tested, the ozone activation was the most promising since the obtained coating not only revealed a homogeneous distribution, but also significantly reduced the adhesion of two relevant etiological bacteria in static conditions (the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli). Moreover, it also impaired E. coli biofilm formation under simulated urinary tract dynamic conditions, reinforcing the potential of CyanoCoating as an antibiotic-free alternative to mitigate medical device-associated infections, particularly in the urinary tract.

Helicobacter pylori antibody and pepsinogen testing for predicting gastric microbiome abundance

Background

Although the high-throughput sequencing technique is useful for evaluating gastric microbiome, it is difficult to use clinically. We aimed to develop a predictive model for gastric microbiome based on serologic testing.

Methods

This study was designed to analyze sequencing data obtained from the Hanyang University Gastric Microbiome Cohort, which was established initially to investigate gastric microbial composition according to the intragastric environment. We evaluated the relationship between the relative abundance of potential gastric cancer-associated bacteria (nitrosating/nitrate-reducing bacteria or type IV secretion system [T4SS] protein gene-contributing bacteria) and serologic markers (IgG anti-Helicobacter pylori [HP] antibody or pepsinogen [PG] levels).

Results

We included 57 and 26 participants without and with HP infection, respectively. The relative abundance of nitrosating/nitrate-reducing bacteria was 4.9% and 3.6% in the HP-negative and HP-positive groups, respectively, while that of T4SS protein gene-contributing bacteria was 20.5% and 6.5% in the HP-negative and HP-positive groups, respectively. The relative abundance of both nitrosating/nitrate-reducing bacteria and T4SS protein gene-contributing bacteria increased exponentially as PG levels decreased. Advanced age (only for nitrosating/nitrate-reducing bacteria), a negative result of IgG anti-HP antibody, low PG levels, and high Charlson comorbidity index were associated with a high relative abundance of nitrosating/nitrate-reducing bacteria and T4SS protein gene-contributing bacteria. The adjusted coefficient of determination (R²) was 53.7% and 70.0% in the model for nitrosating/nitrate-reducing bacteria and T4SS protein gene-contributing bacteria, respectively.

Conclusion

Not only the negative results of IgG anti-HP antibody but also low PG levels were associated with a high abundance of nitrosating/nitrate-reducing bacteria and T4SS protein gene-contributing bacteria.

Cyanobacteria as Nanogold Factories II: Chemical Reactivity and anti-Myocardial Infraction Properties of Customized Gold Nanoparticles Biosynthesized by Cyanothece sp

Cyanothece sp., a coccoid, unicellular, nitrogen-fixing and hydrogen-producing cyanobacterium, has been used in this study to biosynthesize customized gold nanoparticles under certain chemical conditions. The produced gold nanoparticles had a characteristic absorption band at 525–535 nm. Two types of gold nanoparticle, the purple and blue, were formed according to the chemical environment in which the cyanobacterium was grown. Dynamic light scattering was implemented to estimate the size of the purple and blue nanoparticles, which ranged from 80 ± 30 nm and 129 ± 40 nm in diameter, respectively. The highest scattering of laser light was recorded for the blue gold nanoparticles, which was possibly due to their larger size and higher concentration. The appearance of anodic and cathodic peaks in cyclic voltammetric scans of the blue gold nanoparticles reflected the oxidation into gold oxide, followed by the subsequent reduction into the nano metal state. The two produced forms of gold nanoparticles were used to treat isoproterenol-induced myocardial infarction in experimental rats. Both forms of nanoparticles ameliorated myocardial infarction injury, with a slight difference in their curative activity with the purple being more effective. Mechanisms that might explain the curative effect of these nanoparticles on the myocardial infarction were proposed. The morphological, physiological, and biochemical attributes of the Cyanothece sp. cyanobacterium were fundamental for the successful production of “tailored” nanoparticles, and complemented the chemical conditions for the differential biosynthesis process. The present research represents a novel approach to manipulate cyanobacterial cells towards the production of different-sized gold nanoparticles whose curative impacts vary accordingly. This is the first report on that type of manipulated gold nanoparticles biosynthesis which will hopefully open doors for further investigations and biotechnological applications.

Broad-Spectrum Anti-Adhesive Coating Based on an Extracellular Polymer from a Marine Cyanobacterium

Medical device-associated infections are a major health threat, representing about half of all hospital-acquired infections. Current strategies to prevent this problem based on device coatings with antimicrobial compounds (antibiotics or antiseptics) have proven to be insufficient, often toxic, and even promoting bacterial resistance. Herein, we report the development of an infection-preventive coating (CyanoCoating) produced with an extracellular polymer released by the marine cyanobacterium Cyanothece sp. CCY 0110. CyanoCoating was prepared by spin-coating and its bacterial anti-adhesive efficiency was evaluated against relevant etiological agents (Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa and Escherichia coli) and platelets, both in the presence or absence of human plasma proteins. CyanoCoating cytotoxicity was assessed using the L929 fibroblasts cell line. CyanoCoating exhibited a smooth topography, low thickness and high hydrophilic properties with mild negative charge. The non-cytotoxic CyanoCoating prevented adhesion of all the bacteria tested (≤80%) and platelets (<87%), without inducing platelet activation (even in the presence of plasma proteins). The significant reduction in protein adsorption (<77%) confirmed its anti-adhesive properties. The development of this anti-adhesive coating is an important step towards the establishment of a new technological platform capable of preventing medical device-associated infections, without inducing thrombus formation in blood-contacting applications.

Evaluation of gastric microbiome and metagenomic function in patients with intestinal metaplasia using 16S rRNA gene sequencing

BACKGROUND

Despite recent advances in studies on the gastric microbiome, the role of the non-Helicobacter pylori gastric microbiome in gastric carcinogenesis remains unclear. We evaluated the characteristics of the gastric microbiome and metagenomic functions in patients with IM.

METHODS

Participants were classified into six groups according to disease status (chronic superficial gastritis [CSG], intestinal metaplasia [IM], and cancer) and H. pylori- infection status (H. pylori-positive and H. pylori-negative). The gastric microbiome was analyzed in mucosal tissues at the gastric antrum by 16S rRNA gene sequencing. Moreover, we assessed the metagenome including the type IV secretion system (T4SS) gene, as T4SS proteins are essential for transferring CagA from H. pylori- into the human gastric epithelium.

RESULTS

Among the 138 included patients, 48, 9, 23, 14, 12, and 32 were classified into the H. pylori-negative CSG, H. pylori-negative IM, H. pylori-negative cancer, H. pylori-positive CSG, H. pylori-positive IM, and H. pylori-positive cancer groups, respectively. Cyanobacteria were predominant in the H. pylori-negative CSG group compared to in the H. pylori-negative IM and H. pylori-negative cancer groups (H. pylori-negative CSG vs H. pylori-negative IM vs H. pylori-negative cancer: 14.0% vs 4.2% vs 0.04%, P < 0.001). In contrast, Rhizobiales were commonly observed in the H. pylori-negative IM group (H. pylori-negative CSG vs H. pylori-negative IM vs H. pylori-negative cancer: 1.9% vs 15.4% vs 2.8%, P < 0.001). The relative abundance of Rhizobiales increased as H. pylori-infected stomachs progressed from gastritis to IM. In the H. pylori-negative IM group, genes encoding T4SS were prevalent among the metagenome. Additionally, after H. pylori- eradication therapy, the gastric microbiome was similar to the microbiome observed after spontaneous clearance of H. pylori-.

CONCLUSIONS

The relative abundance of Rhizobiales was higher in patients with H. pylori-negative IM than in those with H. pylori-negative CSG or cancer. Additionally, T4SS genes were highly observed in the metagenome of patients with IM. Highly abundant T4SS proteins in these patients may promote gastric carcinogenesis.

Functional ingredients from microalgae

A wide variety of natural sources are under investigation to evaluate their possible use for new functional ingredient formulation. Some records attested the traditional and ancient use of wild harvested microalgae as human food but their cultivation for different purposes started about 40 years ago. The most popular species are Arthrospira (traditional name, Spirulina), Chlorella spp., Dunaliella spp. and Haematococcus spp. Microalgae provide a bewildering array of opportunities to develop healthier food products using innovative approaches and a number of different strategies. Compared to other natural sources of bioactive ingredients, microalgae have many advantages such as their huge biodiversity, the possibility to grow in arid land and with limited fresh water consumption and the flexibility of their metabolism, which could be adapted to produce specific molecules. All these factors led to very sustainable production making microalgae eligible as one of the most promising foods for the future, particularly as source of proteins, lipids and phytochemicals. In this work, a revision of the knowledge about the use of microalgae as food and as a source of functional ingredients has been performed. The most interesting results in the field are presented and commented upon, focusing on the different species of microalgae and the activity of the nutritionally relevant compounds. A summary of the health effects obtained together with pros and cons in the adoption of this natural source as functional food ingredients is also proposed.

Microalgal compounds modulate carcinogenesis in the gastrointestinal tract

Gastrointestinal cancers rank second in overall cancer-related deaths. Carotenoids, sulfated polysaccharides, and polyunsaturated fatty acids (PUFAs) from microalgae exhibit cancer chemopreventive features at different stages of carcinogenesis. For instance, sulfated polysaccharides bear a prophylactic potential via blocking adhesion of pathogens to the gastric surface, whereas carotenoids are effective against Helicobacter pylori infection. This effect is notable because H. pylori has been targeted as the primary cause of gastric cancer. Recent results on antitumor and antibacterial compounds synthesized by microalgae are reviewed here, with an emphasis on their impact upon H. pylori infection and derived pathologies accompanying the progression of gastric carcinogenesis.

Antiadhesive property of microalgal polysaccharide extract on the binding of Helicobacter pylori to gastric mucin

The emergence of antibiotic-resistant Helicobacter pylori is of concern in the treatment of H. pylori-associated gastroduodenal diseases. As the organism was reported to bind gastric mucin, we used porcine gastric mucin as substrate to assess the antiadhesive property of polysaccharides derived from Spirulina (PS), a commercially available microalga, against the binding of H. pylori to gastric mucin. Results show that polysaccharides prevented H. pylori from binding to gastric mucin optimally at pH 2.0, without affecting the viability of either bacteria or gastric epithelial cells, thus favouring its antiadhesive action in a gastric environment. Using ligand overlay analysis, polysaccharide was demonstrated to bind H. pylori alkyl hydroperoxide reductase (AhpC) and urease, which have shown here to possess mucin-binding activity. An in vivo study demonstrated that bacteria load was reduced by >90% in BALB/c mice treated with either Spirulina or polysaccharides. It is thus suggested that polysaccharides may function as a potential antiadhesive agent against H. pylori colonization of gastric mucin.

Stimulation of pigment accumulation in Anabaena azollae strains: effect of light intensity and sugars

The influence of high light intensity on the growth and pigment accumulating ability of Anabaena azollae was investigated. A. azollae responded positively to high light intensity (6 klx) and was further evaluated at higher intensities (10 and 15 klx), in the presence of glucose, sucrose and jaggery +/- DCMU. Significant enhancement in phycobiliproteins and carotenoids was observed in the sugar supplemented cultures at high light intensities. SDS-PAGE profiles of whole cell proteins revealed the presence of unique bands in such treatments. Sucrose supplementation induced a 30-90 % increase in carotenoids, phycocyanin and phycoerythrin content at 10 klx. Molecular analysis of the stimulatory and interactive role of sugars on pigment enhancement at high light intensity may aid in better exploitation of cyanobacteria as a source of pigments.

Metabolites produced by cyanobacteria belonging to several species of the familyNostocaceae

This paper provides a comprehensive overview of metabolites, including lipids and lipid-like compounds, nitrogen metabolites, oligopeptides and amino acid derivatives, produced by cyanobacteria of the genera Anabaenopsis, Aphanizomenon, Aulosira, Cylindrospermopsis, Cylindrospermum, Nodularia, and Richelia of the family Nostocaceae.

Nutrient stress causes akinete differentiation in cyanobacterium Anabaena torulosa with concomitant increase in nitrogen reserve substances

Addition of nitrogen source (nitrate), carbon sources (acetate, citrate and fructose), depletion of nutrients (phosphate-free nitrate medium), dilution of medium (2, 4 and 8 times diluted nitrate medium) under unaerated conditions induced akinete differentiation in Anabaena torulosa. Aerated cultures under the same conditions did not differentiate akinetes. The amounts of reserve metabolites--glycogen and cyanophycin (multi-L-arginyl-poly-L-aspartic acid) granule polypeptide (CGP)--were determined in unaerated and aerated cultures, and at different stages of growth and akinete differentiation. The addition of nitrate, acetate, citrate and fructose under unaerated conditions resulted in the accumulation of glycogen and CGP in higher amounts after 4 d (akinete initiation); the CGP content further changed at mature free akinetes phase. Higher accumulation of reserve products was also observed under nutrient deficiency (phosphate-depleted or diluted media) after 4 d of cultivation. Under aerated conditions reserve product accumulation was considerably lower. Thus a low accumulation of reserve products in aerated cultures showed that aeration probably somehow relieves the organism from a nutritional stress.