Investigating the cryoprotective efficacy of fructans in mammalian cell systems via a structure-functional perspective

Fructans have long been known with their role in protecting organisms against various stress factors due to their ability to induce controlled dehydration and support membrane stability. Considering the vital importance of such features in cryo-technologies, this study aimed to explore the cryoprotective efficacy of fructans in mammalian cell systems where structurally different fructan polymers were examined on in vitro cell models derived from organs such as the liver, frequently used in transplantation, osteoblast, and cord cells, commonly employed in cell banking, as well as human seminal fluids that are of vital importance in assisted reproductive technology. To gain insights into the fructan/membrane interplay, structural differences were linked to rheological properties as well as to lipid membrane interactions where both fluorescein leakage from unilamellar liposomes and membrane integrity of osteoblast cells were monitored. High survival rates obtained with human endothelial, osteoblast and liver cells for up to two months clearly showed that fructans could be considered as effective non-permeating cryoprotectants, especially for extended periods of cryopreservation. In trials with human seminal fluid, short chained levan in combination with human serum albumin and glycerol proved very effective in preserving semen samples across multiple patients without any morphological abnormalities.

Extremophilic Natrinema versiforme Against Pseudomonas aeruginosa Quorum Sensing and Biofilm

Pseudomonas aeruginosa is an opportunistic pathogen that causes high morbidity and mortality rates due to its biofilm form. Biofilm formation is regulated via quorum sensing (QS) mechanism and provides up to 1000 times more resistance against conventional antibiotics. QS related genes are expressed according to bacterial population density via signal molecules. QS inhibitors (QSIs) from natural sources are widely studied evaluating various extracts from extreme environments. It is suggested that extremely halophilic Archaea may also produce QSI compounds. For this purpose, we tested QS inhibitory potentials of ethyl acetate extracts from cell free supernatants and cells of Natrinema versiforme against QS and biofilm formation of P. aeruginosa. To observe QS inhibition, all extracts were tested on P. aeruginosa lasB-gfp, rhlA-gfp, and pqsA-gfp biosensor strains and biofilm inhibition was studied using P. aeruginosa PAO1. According to our results, QS inhibition ratios of cell free supernatant extract (CFSE) were higher than cell extract (CE) on las system, whereas CE was more effective on rhl system. In addition, anti-biofilm effect of CFSE was higher than CE. Structural analysis revealed that the most abundant compound in the extracts was trans 4-(2-carboxy-vinyl) benzoic acid.

Anti-quorum sensing and anti-biofilm activities of Hypericum perforatum extracts against Pseudomonas aeruginosa

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum perforatum L. (Hypericaceae) has been used as a traditional therapeutic for skin wounds, burns, cuts and stomach ailments including stomach ache, ulcers for a long time in many societies. Although many studies about its antibacterial properties can be found, there is a lack of studies about its quorum sensing inhibition properties, which effects bacterial vulnerability directly, on Pseudomonas aeruginosa.

AIM OF THE STUDY

Evaluation of anti-quorum sensing (anti-QS) and anti-biofilm activity of ethanol, methanol, acetone and ultra-sonicated extracts of Hypericum perforatum L. (HP) which is a well-known wound healer, against P. aeruginosa.

MATERIALS AND METHODS

Aerial parts of HP were extracted with ethanol, methanol and acetone. In addition, separate extractions with ultrasonication were carried out with same solvents. Anti-QS activity tests with different doses of HP extracts were performed by employing biomonitor strains, of which the promoter of QS regulating and green fluorescent protein (GFP) genes were fusioned. For anti-biofilm activity, HP extracts were applied to wild type PAO1 strains and biofilm inhibition was quantified via crystal violet staining method.

RESULTS

HP's ethanol, methanol and acetone extracts (250 µg/ml doses) inhibited LasIR signalling pathway up to 65.43%, 59.60%, 55.95% and same solvent extracts obtained with ultrasonication inhibited 71.33%, 64.47%, 57.35% respectively. Moreover, inhibition rates of RhlIR pathway were 28.80%, 50.83%, 45.84% for ethanol, methanol, acetone extracts (250 µg/ml doses) and 51.43%, 57.41%, 50.02% for ultrasonication extracts (250 µg/ml doses), compared to untreated controls. In the experiments, ethanol, methanol, acetone and ultra-sonicated extracts of HP did not inhibit biofilm formation.

CONCLUSIONS

This study shows that HP plant is capable for blocking of las and rhl QS systems of P. aeruginosa. However, it was observed that ethanol, methanol and acetone extract of the plant samples did not show anti-biofilm activity against P. aeruginosa. This led us to thinking that biofilm formation was caused via another pathway such as IQS or PQS. Further studies with isolated active compounds of HP might give a better understanding of the effects on biofilm formation of P. aeruginosa.

Reducing Virulence and Biofilm of Pseudomonas aeruginosa by Potential Quorum Sensing Inhibitor Carotenoid: Zeaxanthin

Pseudomonas aeruginosa can regulate its virulence gene expressions by using a signal system called quorum sensing. It is known that inhibition of quorum sensing can block biofilm formation and leave the bacteria defenseless. Therefore, it is necessary to determine natural sources to obtain potential quorum sensing inhibitors. This study aims to investigate an alternative treatment approach by utilizing the carotenoid zeaxanthin to reduce the expressions of P. aeruginosa virulence factors through quorum sensing inhibition. The inhibition potential of zeaxanthin was determined by in silico screening from a library of 638 lichen metabolites. Fluorescent monitor strains were utilized for quorum sensing inhibitor screens, and quantitative reverse-transcriptase PCR assay was performed for evaluating gene expression. Results indicate that zeaxanthin is a better inhibitor than the lichen secondary metabolite evernic acid, which was previously shown to be capable of inhibiting P. aeruginosa quorum sensing systems.

Effects of Chlorine Stress on Pseudomonas aeruginosa Biofilm and Analysis of Related Gene Expressions

Chlorine is deployed worldwide to clean waters and prevent water-originated illnesses. However, chlorine has a limited disinfection capacity against biofilms. Microorganisms form biofilms to protect themselves from biological threats such as disinfectant chemicals. Pseudomonas aeruginosa is an opportunistic pathogen and its biofilm form attaches to surfaces, living buried into exopolysaccharides, can be present in all watery environments including tap water and drinking water. This research aimed to study the biofilm trigger mechanism of the opportunistic pathogen P. aeruginosa PAO1 strain, which is known to form biofilm in water supply systems and human body, under chlorine stress levels. In addition to biofilm staining, certain genes that are relevant to the stress condition were selected for gene expression analysis. The bacteria cultures were grown under chlorine stress with concentrations of 0.5, 0.7 and 1 mg/l. Six gene regions were determined related to biofilm and stress response: rpoS, bifA, migA, katB, soxR, and algC. Biofilm formation was analyzed by basic fuchsin staining, and gene expressions were quantified by quantitative real-time PCR. According to the results, highest biofilm production was observed in P. aeruginosa PAO1 wild strain under no stress conditions. Higher biofilm amounts were observed for bacteria under 0.5 and 0.7 mg/l chlorine stress compared to 1 mg/l chlorine stress.