فصلنامه دنیای میکروب ها
سال پانزدهم شماره 4 (پیاپی 53، زمستان 1401)

Oils extracted from microorganisms (SCO) are preferable to vegetable oils due to containing more gamma-linolenic acid, more stability against oxidation, and less content of residual pesticides. The oils can be used as dietary supplements. The aim of this study was molecular identification of lipid-producing yeasts and molds in soil and optimization of fat production by Candida glabrata using the Taguchi design.

Several yeasts and molds were isolated from the soil samples of groves and near oil change shops and restaurants. Molecular identification was performed by polymerase chain reaction (PCR). Among them, the highest lipid producers were selected and using the Taguchi design. The best conditions in terms of carbon and nitrogen sources as well as pH for maximum lipid production were determined. The fat obtained was examined by gas chromatography with a mass spectrometer detector (GC-MS).

Among the identified species, C. glabrata had the highest lipid production. Production of palmitoleic, palmitic, linoleic, linolenic, and stearic acid was proven in this study. Lipid production in C. glabrata and Mortierella alpina was 6.9 and10.8 grams per litre, respectively.

Due to the rapid reproduction in yeasts and their ability to produce fatty acids, C. glabrata is a suitable option for fat production.

Bacteria are one of the most important sources of L-asparaginase (ASNase) production which is used as an anticancer agent in the treatment of acute lymphoblastic leukemia worldwide. This study aimed to optimize the ASNase production by bacteria isolated from the soil in northern Iran, and to determine its anti-cancer activity. 

ASNase production by bacterial strains isolated from forest soil samples in Guilan Province, northern Iran was investigated. The optimized condition of enzyme production, kinetics, effect of activators and inhibitors and anticancer activity of the partially purified L-asparaginase against MCF-7 cell lines were studied.

A promising ASNase producing isolate, was identified by 16S rRNA gene sequencing as Bacillus sp. The glutaminase activity of the enzyme was found to be 5.9 times lower than its asparaginase activity and the enzyme showed affinity for L-asparagine with a Km value and Vmax of 0.055M and 35.71 µM/mL/min, respectively. The current ASNase enzyme was stable from pH 6.5 to 8.5 and stable up to 55°C. ASNase activity was not significantly affected by the presence of two metal ions Na+, K+; Mg2+ showed enhancement in enzyme activity, while Ca2+ decreased it. Anticancer activity of the purified L-asparaginase was detected against MCF-7 cell lines with IC50 of 21µg/ml.

The soil isolate Bacillus sp. was identified as a candidate for L-asparaginase production. The future prospect of this enzyme recommends its utility in pharmaceutical and food industry.

Considering the critical conditions of Lake Urmia, identifying bacteria with the ability to live in extreme environments is valuable in terms of microbial applications and tolerance of the existing biological conditions, and it helps us to better understand the surrounding environment. In this study, the most abundant microbial branch in the soil samples obtained from three different heights of 10, 150 and 250 meters of Qale Kazem Khan Mountain, which is located on the shore of a very salty lake in Urmia, has been investigated.

The soil samples were collected to identify and classify Proteobacteria    subgroups using 16S rRNA sequencing using Next Generation Sequencing (NGS) as well as FLASH genetic software and UCHIME algorithm to identify the obtained sequences.

Altitude change affects the abundance of Alphaproteobacteria and Betaproteobacteria. The abundance percentage of Alphaproteobacteria has a direct relationship with altitude, while the abundance percentage of Betaproteobacteria increased with the decrease in altitude.

in the overview the percentage of Proteobacteria abundance the samples has an inverse relationship with the increase in height, whereas in the separate examination of the microbial groups, a significant relationship between the increase and decrease in abundance and the height of sampling is observed. Also, two unknown and unclassified genera in the  Deltaproteobacteria order were also identified which a very high frequency percentage (18-27%) among the data had related to the three samples.

Escherichia coli O157:H7 is one of the main foodborne pathogen that cause severe gastrointestinal issues and death. Cattle are the major reservoir for E. coli O157:H7. During the slaughtering process, E. coli O157:H7 enter to food chain. Identifying the source of contamination plays important role in the control of bacteria. The purpose of this study is molecular typing and determining of genetic relationships among E.coli O157:H7 isolates using RAPD-PCR technique and investigating the relationship between their genetic and antibiotic  resistance patterns.

The Random amplified polymorphic DNA (RAPD) analysis was used to evaluate genetic relationship among the isolates and the results was analyzed by NTSYSpc software. Antibiotic susceptibility of the isolates was examined through disc diffusion method.

The most isolates showed sensitivity to seven antibiotics and resistance were observed in six strains. DNA fingerprinting showed 10 genetic patterns. The isolates from different sources were clustered based on the similarity in RAPD pattern. The strains contain different DNA pattern and high genetic distance, showed different patterns of antibiotic susceptibility.

The genomic diversity showed distinct profiles of DNA in strains with the same clonal relationships and different patterns of antibiotic resistance were revealed. Therefor determining the clonal relationships of isolates with RAPD PCR technique, simultaneous using of antibiotic resistance patterns and molecular typing can be effective in detecting isolates and infection control.

The ability of Klebsiella pneumoniae as an opportunistic bacterium in hospital infections, by producing biofilm on food utensils and hospital surfaces, has adverse effects on the treatment and survival of hospitalized patients. The present study was conducted with the aim of investigating the effect of TiO2 nanoparticles on Klebsiella pneumoniae biofilm formation.

TiO2 nanoparticles were produced using sol-gel method. 62 strains of Klebsiella pneumoniae were isolated from three hospitals in Tehran. Antimicrobial activity of TiO2 nanoparticles against biofilm-producing and antibiotic-resistant strains was determined by disk diffusion method. Definitive identification of the isolates was done through common biochemical tests and 16S rRNA sequencing, and the expression of treC, mrkD, sugE, luxS and 16SrRNA genes was investigated by real time PCR.

The data showed that the ability to form biofilm among isolates obtained from sputum was higher than other isolates. TiO2 nanoparticles with a concentration of 256 μg/ml inhibited biofilm production in fourteen isolated strains. Comparison of LuxS gene expression in Klebsiella pneumoniae untreated and treated with TiO2 showed that the level of gene expression decreased by 3.85 times (p = 0.002).

This study showed that the synthesized TiO2 nanoparticles are effective against the formation of biofilm in Klebsiella pneumoniae strains resistant to several drugs and can be reliable and useful as inorganic antimicrobial agents.

Nowadays, research on nanoparticles as antimicrobial compounds is increasing.Staphylococcus aureus is an important nosocomial pathogen that produces a wide range of exotoxins that are involved in causing disease in the host.The aim of this study was to             investigate the effect of silver nanoparticles (AgNPs) on the expression of pathogenic genes of pvl and tsst genes in Staphylococcus aureus. 

In this experimental study, the minimum growth inhibition concentration of silver nanoparticles was determined by  Broth microdilution method. First, the lowest  concentration of silver nanoparticles that inhibits bacterial growth was determined and then at a concentration lower than that, the expression of pvl and tsst genes in Staphylococcus aureus was studied by Real-Time PCR method. Data were analyzed using one-way ANOVA, Tukey test and P-value < 0.05.

Silver nanoparticles with concentration 62.5μg/ml had growth effect on Staphylococcus aureus bacteria. Also at concentration 31.25 μg/ml, the expression of pvl and tsst genes inStaphylococcus aureus was significantly reduced compared to the reference gene (rpo) (P <0.001).

According to the results of the present study, silver nanoparticles can inhibit the growth of Staphylococcus aureus bacteria and reduce the expression of virulence genes pvl and tsst.