فصلنامه دنیای میکروب ها
سال شانزدهم شماره 2 (پیاپی 55، تابستان 1402)

Pyocyanin is a blue pigment with oxidation and reduction potential and metabolically active, which has medicinal effects on eukaryotic and prokaryotic cells. Trichomonas vaginalis is the causative agent of trichomoniasis, the most important non-viral    sexually transmitted disease in the world. The aim of this study was to evaluate the effect of  pyocyanin extracted from Pseudomonas aeruginosa on Trichomonas vaginalis and PC12cell line.

This study was carried out by an interventional  method. First, pyocyanin was extracted from Pseudomonas aeruginosa strain RTCC1474 with the help of chloroform. The relative purity of the pigment was determined by thin-layer chromatography, spectrophotometry UV-Vis and FTIR. Its effect in different concentrations were investigated on Trichomonas vaginalis and PC12 cell line.

Pyocyanin at a concentration of 10,000µg/ml in 24 hours and concentrations of 5,000 and 2,500µg/ml in 48 hours caused 100% inhibition of the parasite growth. Its IC50 (Inhibitory Concentration of 50%) level in 48 hours was 17.44µg/ml and the CC50 of this pigment on the cell line was 930 µg/ml, so pyocyanin is effective against the Trichomonas vaginalis and its toxicity on the cell line is 53 times higher than of the parasite (SI=53/32).

Considering the inhibitory effect of pyocyanin on the growth of Trichomonas    vaginalis  based on the results, it is possible that with further research on the extraction and purification of this pigment from various isolates of Pseudomonas aeruginosa, and with additional tests in vitro and in vivo, a more accurate judgment regarding the antiparasitic power of this      pigment can be expressed.

 Heavy metal pollution has increased worldwide. Bioremediation of toxic heavy metals in saline environments with conventional microbiological treatment processes is not feasible. Therefore, the use of halophilic and halotolerant bacteria need to be considered for the remediation of saline ecosystems. This study aimed to isolate and characterize toxic heavy metal-resistant and halophilic/halotolerant bacteria from the Lut desert.

 After sampling, halophilic/halotolerant bacteria were isolated on Moderate Halophilic media. Morphological and biochemical characterizations of isolates were carried out. Each isolate's heavy metal resistance was identified by an agar dilution method and the Minimum Inhibitory Concentrations (MIC ) of each heavy metal was determined. Then, sixteen strains were randomly selected and subjected to 16S rRNA gene identification.

 The least toxicities were found with selenite and arsenate on 74 selected isolates, while mercury exhibited the highest toxicity. The maximum MIC values of cadmium, copper, and  chromium were the same. Although, the MIC value of zinc was significantly less. The remarkable resistance toward lead, selenite, and arsenate was reported. Phylogenetic analysis revealed that most strains belong to the Bacillaceae family and Bacillus genus. 

Selected halophilic/halotolerant bacteria from the Lut desert had considerable  resistance to heavy metals. Therefore, these strains could be considered for further investigations of the mechanisms involved in heavy metal resistance of halophilic and halotolerant bacteria or for bioremediation of polluted saline environments.

Quorum sensing system plays an important role in regulating pathogenic propertise and biofilm formation of Pseudomonas aeruginosa. Therefore, inhibiting the quorum sensing system can be a suitable solution in the treatment of infections related to Pseudomonas aeruginosa biofilm. This study was conducted to investigate the effects of sub-inhibitory concentretions of tomatidine on the expression of quorum sensing genes and biofilm formation in Pseudomonas aeruginosa.

The present study was a laboratory interventional study. Biofilm formation was evaluated by microtiter plate method. The RNA of all bacteria was extracted using a column RNA isolation kit and the expression of lasI, lasR, rhlI, rhlR and algD genes in both    normal conditions and after treatment with tomatidine was analyzed. Antibiotic resistance was evaluated by the disk diffusion method.

 The highest and least antibiotic resistance was detected against ticarcillin (80%) and colistin (5%), respectively. Tomatidine up to a concentration of 2 mg/ml had no inhibitory effect on Pseudomonas aeruginosa. 55% of the strains were weak biofilm producers and 45% were strong biofilm producers. The expression of all genes and biofilm formation increased after treatment with tomatidine. The lasI and rhlR genes were respectively the most and least affected genes. Among the five genes examined, only rhlR is significantly more expressed in weak biofilm producers.

The results showed, contrary to expectation, the sub-MIC concentrations of tomatidine increase the expression of quorum sensing genes and biofilm formation in Pseudomonas aeruginosa.

Aflatoxins are produced as toxic secondary metabolites by some  Aspergillus species. Since these fungal species can contaminate food and animal feed, microbial contamination monitoring and control is important. In the current study, the correlation between expression of two aflatoxin biosynthetic pathway genes aflO and aflQ and was investigated.

Sixty-seven different isolates of aflatoxin-producing Aspergillus species selected and the presence. expression of aflO and aflQ gene sequences were assayed by PCR and quantitative Real-Time RT-PCR methods, respectively. In addition, the amount of aflatoxin B1 by high-performance reverse chromatography (RP-HPLC) using a fluorescent detector.

Forthy one, out of 67 isolated species had both aflO and aflQ genes. Seventeen samples out of 26 (65%) had aflatoxin B1 levels higher than 5 ng/g and 6 samples (23%) produced high levels of this toxin (more than 100 ng / g) as well.

Considering the relative correlation between the expression of selected aflatoxin genes and AFB1 produced in feedstuffs, it seems that the investigation of other aflatoxin-producing genes can lead to a better correlation and complete the results of this study.

Aflatoxin in pistachios and some other foods and feeeds causes diseases in human and animals. Aspergillus flavus has been reported as an important producer of aflatoxin. In this research, antagonistic bacterial agents were isolated from pistachio orchards in Yazd province, Iran, and their antagonistic properties were investigated on A. flavus isolates.

Different isolates of Bacillus sp. and Aspergillus sp. were isolated from different pistachio orchards in Yazd. A. flavus species were identified and various biochemical and molecular characteristics of bacterial isolates were investigated. Also, the antibiosis properties and production of antibiotics and effect of extracellular secretion, antifungal volatile substances and siderophore of the isolates were evaluated on A. flavus.

According to the results of biochemical and molecular tests, all isolates were identified as Bacillus. Strain Pr3 had the most effect with 95% and strains Pr5 and Pr7 had the least effect on A. flavus with 50%. The results of the antibiotic production test using chloroform method showed that isolates Pr3 and Pr7 had the highest and lowest antibiotic production with 84.35 and 38%, respectively. In this study, isolates Pr1, Pr2, Pr3 and Pr9 significantly produced extracellular     secretion, siderophore and antifungal volatile substances and showed different amounts of effect on A. flavus.

According to the results obtained from this research and the findings of other related researches, different Bacillus species and their metabolites have high antagonistic properties against A. flavus, which can be used as an effective and promising method to inhibit the growth of the fungus and to prevent the production of aflatoxin.

Silver nanoparticles have been widely used due to their anti-bacterial activities and anticancer properties. The aim of this study was to investigate the antimicrobial effects and cell toxicity of silver nanoparticles synthesized using extracts of chamomile on three neoplastic cell lines (A549, MCF-7 and HeLa).

Silver nanoparticles were biologically synthesized using extracts of chamomile. After physical and chemical evaluation of the synthesized nanoparticles, their antimicrobial properties were estimated on Escherichia coli and Staphylococcus aureus. Finally, the inhibitory effect of synthesized nanoparticles evaluated by using MTT technique on 3 neoplastic cell lines.

  The average size of nanoparticles synthesized by the extract of chamomile were 19 nm. The synthesized nanoparticles could have a significant inhibitory and lethal effect on the two named bacteria. silver nanoparticles were able to show a 50% inhibitory effect on different cell lines at a concentration of 50 μg/ml.

Based on the results, it can be stated that medicinal plants can be used in the successful biosynthesis of silver nanoparticles. After human studies and tests, chamomile-based silver nanoparticles can be used as effective therapeutic agent in the treatment of some cancers due to their coating of effective secondary metabolites and the release of silver ions (Ag+).