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Antibiotic-resistant Pseudomonas aeruginosa infections are usually difficult to treat, and there are limited antibiotics for treating them. Increased antibiotic resistance of this bacterium, especially in a multidrug form, has caused many problems for treatment. Nowadays, metal nanoparticles are considered as appropriate alternatives to antibiotics. The objective of the present study was to investigate the effect of gold nanoparticles on the expression of MexB and MexA genes in Pseudomonas aeruginosa isolates.Pseudomonas aeruginosa isolate was identified using biochemical tests and an API kit. The antibiotic sensitivitytest for different antibiotics was performed withthe Kirby-Bauer test according to the CLSI standard. The presence of MexB and MexA genes was assessed by PCR. The effect of gold nanoparticles was investigated by microdilution to evaluate the minimum inhibitory concentration, and the expression of MexB and MexA treated genes was done with silver nanoparticles by the Real-Time PCR method.40 Pseudomonas aeruginosa isolates were detected and identified. These isolates showed significant resistance to various antibiotics. All strains were carriers of MexB and MexA genes, and finally, in the expression of MexB and MexA genes,a significant decrease in the expression of these genes was observed in the samples treated with gold nanoparticles compared to non-treated samples.One of the mechanisms of antibacterial activity of gold nanoparticles is through reducing the expression of mexA and mexB genes and thus reducing the number of active efflux pumps at the cell surface. [ABSTRACT FROM AUTHOR]

Background: Considering their specific adaption to marine milieus, marine actinomycetes constitute an excellent source for producing unique bioactive substances. They are also important sources of antibiotics and extracellular enzymes, geosmin, and enzymes with potent antibacterial and anticarcinogenic properties and low toxicity. The objective of this study is to isolate actinomycetes producing antitumor substances from the sediments of Hara forests in the Persian Gulf and investigate the positive in vitro effects of these microorganisms through protease production on blood cancer cell lines. Methods: In this study, 30 samples of sediments were collected from Hara forests. After the strains were isolated, the samples were identified using morphologic characteristics. The protease was extracted and its cytocidal activity on the Aacute lymphoblastic leukemia (ALL) was studied. Results: The results indicate that out of the 30 actinomycetal isolates, 15 specimens were capable of producing protease, of which 2 affected the malignant cell line. In addition, statistical analysis revealed that the protease exerted greater cytocidal effect on the blood cancer cell line at higher concentrations. The cytopathic property of the protease was observed as cell rupture. Conclusions: Our findings indicate that sediments of the Hara forests in the Persian Gulf are rich in active actinomycetes producing novel anticarcinogenic substances, warranting identification and purification. These results suggest the need for studies on marine microbes as a new potential for pharmaceutical research. [ABSTRACT FROM AUTHOR]

Bacillus thuringiensis is a bacterium known for producing insecticidal and cytocidal crystal protein during sporulation. One hundred soil samples were analysed which were introduced by seven methods, out of which sixty B. thuringiensis strains were collected to study the distribution and diversity of crystal proteins. The strains were characterized on the basis of microscopic examination of parasporal crystal morphology, biochemical tests, and analysis of parasporal inclusions protein profiles by SDS-PAGE. Majority of strains had bipyramidal crystals. B. thuringiensis subsp. thuringiensis was the most common biochemical type. Overall, according to our finding, it could be concluded that genetic diversity of B. thuringiensis strains is dependant on the geographical areas. It means that the production of crystal protein by different strains of B. thuringiensis probably dependant on the geographical area. [ABSTRACT FROM AUTHOR]