نشریه زیست شناسی میکروبی
پیاپی 51 (پاییز 1403)

One of the major environmental problems, especially in oil-rich countries, is the increase in pollutants caused by hydrocarbon compounds. Recently the use of white rot fungi for bioremediation of pollutants has shown valuable results. In this study, the synergistic effect of two native white rot fungi on the activity of the enzymes laccase and manganese peroxidase and on the degradation of 400 mg/l anthracene over 28 days was evaluated. The anthracene degradation and enzymatic activity of the fungi were evaluated by GC-FID gas chromatography and spectrophotometric assay, respectively. The results of the mixed cultivation were compared with the individual cultivation of each of the two fungi. Based on the results of gas chromatographic analysis with flame ionization detector (GC-FID), the percentages of anthracene degradation by Trametes versicolor v21te and T. hirsuta and the mixed culture of the two fungi were 60, 34 and 70%, respectively. In addition, laccase enzyme activity increased by 23% and 16% in the mixed culture compared to the pure culture of T. versicolor v21te and T. hirsuta , respectively. The results show that cultivating this group of fungi together resulted in enzyme stimulation and has increased their bioremediation capacity. The results of this research can be a potential step in the removal of   pollutants in industries related to petroleum products. In addition, the importance of ligninolytic enzymes in industries such as textile and paper bleaching further highlights the importance of such studies.

Alzheimer's is the most common age-related neurodegenerative disease, characterized by amyloid plaques and intraneuronal neurofibrillary tangles. Nowadays, researchers are considering the use of nanoparticles in the treatment of skin diseases, various injuries and burns, bacterial and fungal infections, and digestive diseases. This research aims to biosynthesis of gold nanoparticles using Bacillus cereus PTCC 1015 and investigate their antioxidant and anti-amyloid effects on bovine serum albumin as a model protein. The properties of the synthesized nanoparticles were investigated using UV-vis, FTIR, XRD, TEM, SEM and EDX analyses.  The antioxidant and anti-amyloid activities of the synthesized nanoparticles were also evaluated using DPPH and Congo red tests, respectively. Based on electron microscopy images, the synthesized nanoparticles had a spherical morphology with sizes ranging from 20 to 70 nm. The DPPH assay results showed that the synthesized nanoparticles effectively inhibited DPPH free radicals in a concentration-dependent manner, with an IC50 value of 0.8 μg/ml. Furthermore, the anti-amyloid activity results showed that the synthesized nanoparticles have significant potential to inhibit  amyloid fibrils, and the highest percentage of inhibition was observed at a concentration of 3.2 μg/ml. The present study demonstrated that B. cereus PTCC 1015 is an effective option for the synthesis of gold nanoparticles. Considering the antioxidant and anti-amyloid activities of the synthesized gold nanoparticles, this study represents an important step for further in vivo research.

Pseudomonas aeruginosa is one of the most common opportunistic microorganisms causing infections in a wide variety of patients. Increasing intrinsic and acquired resistance to antibiotics is a global challenge for the treatment of infections. The aim of this study is to evaluate the extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase activity of Pseudomonas anrogenase isolated from clinical specimens. In this research 55 strains of Pseudomonas aeruginosa isolated from clinical patients were identified by biochemical methods and then their antibiotic resistance pattern was determined by diffusion method. The strains producing ESBLs were evaluated by combined test and AmpC by the double synergism phenotypic method. Molecular methods were also used to detect strains carrying ACC, FOX, MOX, DHA, MIR, CMY, TEM, SHV and CTX genes. In this study, the highest resistance was to the antibiotic meropenem (52.7%) and the lowest resistance was to the antibiotic colistin (1.8%). When the synergism of the double discs was examined, 61.8% of the strains were found to produce AmpC. None of the strains in this study were ESBLs. The frequencies of DHA, MOX, FOX, ACC, SHV and CTX genes were 30.9%, 12.7%, 81.8%, 27.3%, 5.5% and 5.5%, respectively. MIR, CMY and TEM genes were not observed in any of the strains in this study. The results showed the frequency of the FOX gene among the strains and the greater resistance of these strains to the antibiotic meropenem, and AmpC β-lactamase activity was evaluated as an important factor in the occurrence of antibiotic resistance.

Cyanobacteria are prokaryotes found in many heavy metal polluted environments. Since their photosynthetic system has an urgent need for metals, the homeostasis of these micronutrients in cyanobacteria has been widely studied. The aim of this article is to compare the ability of two single-celled and filamentous strains of Alborzia kermanshahica and Desmonostoc alborizicum to remove heavy metals and different concentrations of sodium chloride salt. In this study, after the cultivation of two cyanobacterial strains, the morphology of the strains, determination of dry weight, protein and extracellular polysaccharides were studied in different environments, then atomic absorption spectroscopy was used to estimate the removal rate of heavy metals. Volatile compounds were identified using an atomic absorption spectrometer. The results showed that the soil single-cell strain had a greater ability to remove heavy metals than the aquatic filamentous strain and the ability to grow at different salt concentrations. In the control cultures, the amount of dry cell weight, exopolysaccharides and protein in the single-cell strain was 1.70, 1.32 and 1.5 times higher than in the filamentous strain, respectively. This caused the single-cell strain to remove the three metals nickel, chromium and copper in the first ten minutes in control cultures without sodium chloride. However, the amount of protein in both strains decreased in the presence of heavy metals. Although the absorption of heavy metals decreases with time, the results of statistical analyses show that the single-cell strain of Alborzia kermanshahica is resistant to salt, in fact there is a significant increase in exopolysaccharides and cell dry weight at a salt concentration of 0.5%. Sodium chloride compared to the control culture demonstrates this. In addition, the highest levels of exopolysaccharide, protein and carbohydrate were observed in the nickel-containing culture medium for both strains studied. The results of volatile compound analysis using GC-MS showed an increase in ester, ketone, alcohol, benzene and aldehyde compounds, which may play an important role in salinity stress management and heavy metal removal . The results of this study show that A. kermanshahica strain can be a good candidate for heavy metal removal in saline environments.

One of the major problems in treating infections caused by Acinetobacter baumannii is the significant increase in antibiotic resistance. Several factors play a role in the resistance of bacteria to drugs and their pathogenicity, one of which is the beta-lactamase protein. Therefore, in this study, the multidrug resistance (MDR) and the distribution of the blaPER، blaOXA-51 and blaOXA-23 genes in A. baumannii were evaluated. Initially, 150 clinical samples were collected from patients admitted to Qochan Hospital in 1400. A. baumannii isolates were identified using specific biochemical tests. The phenotype of antibiotic susceptibility of A. baumannii isolates to cefepime, ceftriaxone, meropenem and colistin was studied by disc diffusion method. PCR was used to test for the presence of the blaPER، blaOXA-5  and blaOXA-23 genes in resistant isolates. The results showed that 33.3% of the samples were associated with A. baumannii infections, and A. baumannii was most commonly isolated from blood samples. In the antibiotic resistance study, 16% of A. baumannii isolates were sensitive to cefepime and 17% to ceftriaxone and meropenem antibiotics. No colistin resistant  isolates were detected. 75% of the isolates had the MDR phenotype. PCR showed that all resistant isolates tested carried all three genes blaPER، blaOXA-51  and blaOXA-23. The results showed that a high percentage of A. baumannii isolates tested were resistant to carbapenem antibiotics and a high percentage of carbapenem-resistant isolates produced beta-lactamase genes. The increase in the hospital prevalence of A. baumannii highlights the need to develop protective programmes such as the prevention and control of ICU-acquired infections. Molecular methods can also be used to identify these bacteria, determine their antibiotic resistance and prescribe antibiotics accordingly.

The use of microencapsulated probiotic bacteria, by maintaining the survival of probiotic bacteria during the production and storage process, produces high quality and long-lasting products. Lentinula edodes polysaccharide is a prebiotic that causes the growth and better performance of probiotics and helps to preserve the product for a long time. For this purpose, 20 samples were prepared from the wastewater of dairy factories around Tehran and 10 bacterial isolates and 10 yeast isolates were isolated from the samples based on biochemical, macroscopic and microscopic tests. Heat tolerance test, acid tolerance and resistance to bile salts and antibiogram were performed to measure the probiotic properties. The polysaccharides of Lentinula edodes were then extracted using a diethylaminoethyl Sephadex-25A ion exchange chromatography column and the amount of polysaccharide was determined using the phenol-sulphuric acid method. Fourier spectroscopy was used to detect biochemical compounds. Superior probiotic isolates were identified by PCR. The microencapsulation effect of superior isolates was investigated using sodium alginate and lentinula edodes polysaccharides on orange juice, apple juice and kombucha drink. Kluyveromyces lactis strain CBS 683 and Lactobacillus brevis strain 123-20 were identified and encapsulated with relative probiotic properties, growing more than in the free state. The shelf life and sensory characteristics of drinks containing bacteria and yeast encapsulated with sodium alginate and polysaccharide were also improved compared to the control group, and during 60 days of storage at 4°C, the bacteria and yeast survived and maintained their performance. The best protection was provided by encapsulated Lactobacillus brevis strain 123-20 in orange juice and apple juice. The use of native strains encapsulated with biocompatible compounds preserves the sensory characteristics of food, prevents food spoilage during storage by producing postbiotics and improves the function of the digestive system.

Pollution of living organisms' ecosystems by crude oil and its products has harmful effects. The use of approaches such as bioremediation has received much attention due to their cost-effectiveness and being eco-friendly. In the present study, different types of Gobiiformes were collected from four regions in the north of the Persian Gulf, and then their intestinal bacterial flora was identified by biochemical and molecular polymerase chain reaction (PCR) methods. The ability of these bacteria to degrade crude oil was investigated using the gas chromatography (GC) technique. The obtained results showed the isolation of bacteria Thalassospira permensis, Pseudomonas aestusnigri, Cobetia marina, and Halomonas beimenensis from the intestines of Scartelaos tenuis, Periophthalmus waltoni, Istigobius ornatus, and P. waltoni, respectively. Also, two strains of T. permensis and H. beimenensis with growth rates of 1.09 and 1.43 (OD600nm) had the highest crude oil decomposition with 85.17 and 88.13%, respectively. The results of this study revealed that the microbial flora of these fishes is effective in removing oil pollution. This process needs more investigation and optimization of bioremediation conditions.