فصلنامه زیست شناسی میکروارگانیسم ها
پیاپی 46 (تابستان 1402)

Today, the treatment has been more difficult because the resistance of human opportunistic pathogens including the urinary tract infections bacteria increased against a wide range of antibiotics.

In this study, Pseudomonas aeruginosa was isolated from environmental surfaces and then the presence of a gene related to pigment biosynthesis was confirmed by PCR. Pyocyanin pigment was extracted by chloroform and its purity was confirmed by the TLC method. Bacteria causing urinary tract infections including Staphylococcus saprophyticus, Escherichia coli, Enterococcus sp. and Klebsiella sp. were collected and the antimicrobial effect of this pigment was investigated by disk placement and well-diffusion methods on each of the above bacteria.

The results of this study showed that the highest sensitivity to pyocyanin pigment extract was related to Staphylococcus saprophyticus and Enterococcus sp. in disk placement and well-diffusion methods. The diameter of the growth inhibition zone without considering the effect of chloroform for both bacteria was 4 and 2 mm in the disk placement method and 4 and 3 mm in the well-diffusion method, respectively. Therefore, pyocyanin pigment had a greater antimicrobial effect on gram-positive bacteria than gram-negative bacteria.

In this study, pigment-producing bacteria were isolated from environmental surfaces due to their lower probability of pathogenicity for humans than strains isolated from clinical samples that have been used in most studies for pigment extraction. Therefore, these strains can be a better option for extracting pyocyanin pigment as an antimicrobial matter that can be replaced with antimicrobial agents and synthetic antibiotics.

Probiotic bacteria, including lactobacilli, are known to prevent many cancers. In this regard, the present study aimed to evaluate the anti-cancer effects of Lactobacillus cytoplasmic extract isolated from dairy products in Guilan province on the HT-29 colon cancer cell line.

In this study, Lactobacillus bacteria were isolated and identified from dairy products based on conventional culture and biochemical methods. Then, using specific primers, the 16S rRNA gene of the bacteria was amplified and the confirmed samples were compared with the sequences in NCBI after sequencing. Different concentrations of 0.5, 0.75, 1, 1.5, and 2 mg/mL were made from the cytoplasmic extract of the selected strain. Finally, the cytotoxicity effects of Lactobacillus cytoplasmic extract on cancer HT-29 and normal HUVEC cell lines were investigated by the MTT method.

The results of the MTT assay showed that the cytoplasmic extract of Lactobacillus dose-dependently reduced the survival and proliferation of colon cancer cells at 24 h, with the highest inhibitory effect at 2 mg/ml. Concentrations of 1, 1.5, and 2 mg/mL decreased cell viability by 50±4.87%, 40±8.61%, and 25±5.80%, respectively. The IC50 value of the cytoplasmic extract was 1.43 mg/mL for the HT29 cells. Also, cytotoxic effects on the normal HUVEC cell line were not observed.

According to the results of the study, the cytoplasmic extract of Lactobacillus isolated from dairy products reduced the growth of HT-29 cancer cells, which with further studies can be used as a biological product in the treatment and prevention of colon cancer.

It has been more than two years since the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China. The SARS-CoV-2 has created an unprecedented pandemic (COVID-19) in the modern era and challenged all the scientific, economic, and social structures of the world. Extensive worldwide research has been conducted to study the structure and function of the SARS-CoV-2 spike protein since the beginning of the pandemic. The role and importance of spike protein in the introduction of SARS-CoV-2 into human cells has been proven. Among the important and effective factors in controlling the Covid-19 pandemic is understanding the structural changes of spike protein in different variants of the virus and the effectiveness of drugs and vaccines against new SARS-CoV-2 variants. Due to the great importance of spike protein SARS-CoV-2, it was tried to study its structure and interaction with cellular receptors using bioinformatics tools in this study. Furthermore, the effects of different SARS-CoV-2 variants on existing drugs and vaccines were reviewed.

The bioinformatics methods and molecular docking was used to study the binding function of spike protein to its various cellular receptors in the human body. HDOCK web server was used to perform the molecular docking process and in the next step, the PDBsum web server was used for post-docking checks and to ensure the accuracy of the obtained data. PyMOL software was also used to study and visualize replacement and deletion mutations in the spike protein.

Extensive mutations in the spike protein in the omicron variant indicate a redesign in the spike protein. These massive mutations cause extensive changes in the structure and function of the spike protein. The data obtained from molecular docking and comparing the energy level (docking score) of spike protein binding of different variants of the virus with different cellular receptors indicate a high tendency of the spike protein to bind, with lower energy levels and more stable, to KREMEN1 receptor than the main ACE2 receptor.  The level of spike protein binding energy levels of different virus variants was almost similar to other receptors (except the KREMEN1 receptor) or slightly different from the spike protein binding energy levels with the main ACE2 receptor.

There is not much difference in the tendency of spike protein binding of emerging and important variants of the virus (main, alpha, delta, and omicron) to ACE2 receptor, but the tendency to bind to KREMEN1 receptor is increasing and has reached its peak in the delta variant. The energy level of the spike protein binding to the KREMEN1 receptor is significantly negative compared to other receptors, indicating greater binding and stability. Also, considering the level of energy received from the HDOCK web server, it can be concluded that although the ACE2 receptor is the main receptor for the spike protein, other receptors can still bind to the spike protein with good stability. Based on the available information, so far there have been no reports of docking between spike protein and other non-main spike protein receptors (AXL, ASGR1, KREMEN1). Therefore, more comprehensive research is needed to confirm or refute these findings.

Today, the production of green silver nanoparticles by cyanobacteria as antimicrobial agents is widely used in medical and therapeutic industries. In this study, considering that so far no study has been conducted to investigate the potency of cyanobacteria Nostoc sp. as aquatic water belonging to the freshwater of Golestan province, we decided to evaluate the potential of this strain in the biosynthesis of silver nanoparticles by performing different techniques.

After the growth and molecular identification of cyanobacteria Nostoc sp. in the BG-110 culture medium in the growth chamber, two wet biomass and boiling methods were used to produce silver nanoparticles. Then, by inoculating wet biomass at concentrations of 1, 2, and 3 mM silver nitrate and comparing color change, UV-Vis spectroscopy peaks, and measuring stability at 0, 12, 24, and 48 hours, the most efficient method of silver nanoparticle biosynthesis was selected. In addition, instrumental analysis of Raman and Fourier Transform Infrared (FTIR) spectroscopy, Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and antimicrobial disk antimicrobial properties for the best and most stable nanoparticle production method was done.

Among the two methods used in the production of silver nanoparticles, by examining the dark brown color and the strong 420 nm peak obtained from UV-Vis spectroscopy, the wet biomass method at a concentration of 1 mM at zero time had the highest adsorption compared to the boiling method. The results of FTIR showed successful production of silver nanoparticles using wet biomass of cyanobacterium Nostoc sp. at a concentration of 1 mM silver nitrate at time zero as a safe and biodegradable method, environmentally friendly, low cost, and in accordance with the principles of green chemistry. In addition, the results of FTIR showed that biosynthesized silver nanoparticles had a protein coating that plays a major role in the reduction and stability of silver nanoparticles. The DLS results showed that the nanoparticles produced were between 28 and 50 nanometers in size and the average size of silver nanoparticles was 16.1 nanometers. The results of SEM microscopy showed that the size of the produced nanoparticles was between 28 and 50 nm in terms of spherical morphology. Also, the results of the one-way analysis of variance and Tukey test showed significant inhibitory power of silver nanoparticles against Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa.

Cyanobacteria Nostoc sp. can be used as a potential factor in the production of silver nanoparticles with unique properties and performance for various applications in medicine, industry, etc.

Staphylococcus aureus, especially Methicillin-Resistant Staphylococcus aureu, (MRSA) is one of the major causes of nosocomial and community-acquired infections. Nowadays, it is known as a health problem in the world due to its resistance to most antibiotics. The present study aimed to determine the prevalence of the vanA gene in MRSA isolated from patients with bedsores.

In the current study, 80 clinical isolates were collected from patients with bedsores at Loghman-e Hakim Hospital, Iranmehr Hospital, and Tehran Wound Center. The samples were identified using standard laboratory tests and resistance to cefoxitin disk (30µg) and evaluating the presence of the mecA gene. The resistance of the MRSA isolates to different antibiotics was checked using the disc diffusion method. The presence of the vanA gene in these isolates was investigated using specific primers and polymerase chain reaction (PCR).

Of the studied isolates, 29 isolates were identified as methicillin-resistant. The highest antibiotic resistance level was observed against erythromycin and clindamycin. The lowest antibiotic resistance level was determined against linezolid with 82.75%, 82.75%, and 13.8% respectively. The vanA gene was detected in all of the MRSA isolates. Also, multidrug resistance (MDR) was observed in almost 72.41% of isolates.

The prevalence of the vanA gene has increased in MRSA isolates. In this regard, high and multiple isolates of Staphylococcus aureus resistant to common antibiotics should be considered a serious matter.

Using efficient and environment-friendly techniques for the remediation of potentially toxic and harmful metals in contaminated soils plays a vital role in public health. The present study was conducted to assess the efficiency of the biosurfactant produced by the tolerant bacteria to cadmium (Cd) for the removal of Cd from contaminated soil as a completely randomized design with three replications.

Three native strains of bacteria including Bacillus pumilus, Alcanivorax dieselolei, Marinobacter hydrocarbonoclasticus were studied in terms of resistance to different levels of Cd contamination. In order to evaluate the production capacity of biosurfactants in the superior strain, 4 tests of emulsification measurement, oil spreading, drop collapsing, and hemolytic activity were used. Then, to investigate the amount of Cd removal from the contaminated soil, three treatments including the superior strain, the biosurfactant produced by it, and the control soil (i.e., without the strain and biosurfactant) were added to the contaminated soil.

By applying Marinobacter hydrocarbonoclasticus as the superior strain and the biosurfactant produced by it to the Cd contaminated soil, it was observed that the biosurfactant treatment significantly had more ability on Cd removal from the soil compared to other treatments. Also, there was no significant difference between the Marinobacter hydrocarbonoclasticus and the control treatment.

In general, it is concluded that after local calibration and also repeating and performing the experiment in natural conditions, the biosurfactant produced by Marinobacter hydrocarbonoclasticus can be more reliably used as a conditioner for the soils contaminated with Cd.

Crude oil pollution in the Persian Gulf is a major problem in this important marine environment. Today, the use of biological degradation methods to remove these pollutants is considered. The purpose of the present study is to compare the two methods of biological stimulation and biological enhancement for the degradation of sediments contaminated with crude oil in the Persian Gulf.

In this research, six types of microcosms were designed to understand the effectiveness of biostimulation and bioaugmentation on the microbial population of Khark Island sediments. Indicators such as the quantity of degrader, heterotrophs, and the rate of crude oil degradation were investigated at different times and finally, the degradation over time was measured by the Gas Chromatography method.

The results of this study showed that the combined microcosm of biostimulation and bio-augmentation (SB) with the amount of heterotrophic bacteria (equal to 3.9 x 106) and degrader (equal to 1 x 106) had the highest quantity. Population dynamics in microcosms were also studied and the lowest quantity of heterotrophic bacteria with a numerical value of 1x104 was related to natural sediments. The statistical results of this research proved that there is a significant relationship between the type of method chosen for biodegradation with the sampling time and the quantity of the dynamic population, and finally, with the increase of incubation time, the biodegradation of oil in all microcosms increased significantly (95%), but the best biodegradation of oil was related to the integrated microcosm of biostimulation and bio-augmentation.

By using the type of biological remediation method according to the nature of the contaminated sediments, oil-contaminated sediments can be rehabilitated with the help of biological methods and contribute to the stability of marine ecosystems.