فصلنامه دنیای میکروب ها
سال دهم شماره 2 (پیاپی 31، تابستان 1396)

Acinetobacter baumannii is a Gram-negative coccobacillus that is widely distributed in nature and considered as one of the important causes of hospital infections. The present study was conducted to genotype Acinetobacter baumannii strains isolated from blood infections using Multi Locus Sequence Typing (MLST) method.
A total of 36 Acinetobacter baumannii strains were isolated from blood infection samples collected from Baqiatalah and Payambaran hospitals, Tehran, Iran. The PCR products obtained from amplification of seven housekeeping genes were sequenced. The nucleotide sequences of each gene in each isolate were queried against the reference sequence in the MLST database. In addition to characterization of the alleles specific to each gene, the
sequence types (ST) of all isolates were determined.
A total of 5 clones including ST25, ST136, ST307, ST327, and ST328 were identified in 36 isolates. ST of 2 isolates were not identified in MLST database. The identified STs were placed into 5 genetic clusters including A, B, C, D, and E.
Identifying an acceptable level of genetic diversity among the isolates using MLST technique shows that this method is useful for studying and typing of Acinetobacter baumannii isolates. Therefore, it is possible to cluster isolates with diverse origins in different groups.

One of the major problems in bio-ethanol production is formation of toxic compounds such as furfural and hydroxymethyl furfural from acidic hydrolysis of lignocellulosic materials. Cells immobilization is a useful method for protecting microorganisms against direct physicochemical tensions and reusing them. This study was conducted to assess the effect of alginate-chitosan complex carrier on immobilizing Saccharomyces cerevisiae in order to enhance the yield of ethanol production in the presence of furfural.
Methods & Materials: In this study, S. cerevisiae AT-1350 were immobilized in alginate-chitosan complex carrier. Then, 3 g/L of furfural was added to the fermentation medium as the stressor. Glucose consumption was determined using glucose sensing kit. High performance liquid chromatography was used to measure the amount of ethanol production.
The results showed that the ethanol yield was decreased 21% by non-immobilized autochthonous yeast, in the medium containing 3 g/L furfural as compared to the control (furfural-free medium). On the other hand, in the presence of furfural, using yeast immobilized in alginate-chitosan complex increased the ethanol yield 6.9% and 14.4% in comparison with yeasts immobilized in alginate and non-immobilized yeasts, respectively.
The alginate-chitosan complex can be used as a suitable carrier to immobilize and protect yeast cells against tensions and thusto enhance the ethanol yield obtained from lignocellulosic wastes.

Iron magnetic nanoparticles have been widely studied for biological, medical as well as industrial applications. The physical and chemical synthesis methods currently used to produce nanoparticles cause environmental contamination. Certain bacteria are capable of synthesizing significant amounts of iron nanoparticles, quite in conformity with the principles of green chemistry. The objective of this study was to isolate and identify iron nanoparticle-producing bacteria from soils of Hormuz Island, Iran.
This cross-sectional study was carried out with soil sampling from the Hormuz Island. Following serial dilution, culturing and purification in a combined solid agar culture medium, biochemical and molecular tests were used to identify bacteria. The properties of nanoparticles produced by bacteria were studied using UV-Vis spectroscopy, X-ray crystallography (XRD) and scanning electron microscope (SEM).
The presence of Pseudomonas sp. was confirmed using biochemical characteristics, sequencing, and blasting the obtained sequences in NCBI database in the Hormuz Island soil. UV-Vis spectrometry and XRD graphs proved the presence of iron nanoparticles produced by bacteria. Furthermore, SEM images showed the size of nanoparticles as less than 50 nm.
The results of this study highlighted the adequacy of Pseudomonas isolated from the Hormuz Island soil in iron nanoparticle bio-synthesis as a cost-effective method, without any need for high energy expenditure. Therefore, the use of this bacterium as a useful biological source for large scale synthesis of iron nanoparticles is recommended through further studies.

Chemolithotrophic bacteria have an important role in the biogeochemical cycle in natural ecosystems. For instance, the oxidative part of the sulfur cycle is handled by sulfur-oxidizing bacteria. Moreover, these bacteria have an important role in various industrial fields including bioleaching. The aim of this study was isolation and identification of chemolithotrophic sulfur-oxidizing bacteria from the Namakdan cave Qeshm, Iran.
In this cross-sectional study, after sampling from the Namakdan cave in Qeshm and transferring the samples (salt, water, and sediment) to the lab, sample inoculation into enrichment media was carried out with three concentrations of NaCl. Following pH and temperature measurement, samples were transferred into solid and two-phase media. Further characterization of the isolates was performed using 16S rRNA gene amplification. Further analysis was performed to characterize the autotrophic or heterotrophic features of the isolates. Biomass was examined using classical turbidity method.
Totally, 39 strains were isolated from samples, based on differences in primary features such as colony form or growth rate. A total of 5 isolates were selected for further studies. Phylogenetic analysis showed that these isolates belong to Halothiobacillus genus.
Due to 30% salinity and neutral pH of this cave, isolation of chemolithotrophic sulfur-oxidizing bacteria was limited to few genera. Chemolithotrophic bacteria have longer growth time in comparison to heterotrophic ones, increasing generation time to 30 days.

Industrial activities in the world release large amounts of pollutants including heavy metals. This study was aimed to assess heavy metal removal by phosphate-solubilizing bacteria and evaluation the effects of extracellular factors including phosphatase in removing the metal.
Material & In this experimental study, phosphate-solubilizing bacteria were isolated from Amaranth rhizosphere on Pikovskaya medium, and subsequently identified using molecular methods. Acid phosphatase level was measured by colorimetric method. MIC50 and MBC of nickel, cadmium, chromium, and lead were detected by microplate test. Heavy metal removal through cells or culture supernatant was assessed by atomic absorption spectroscopy. Changes in the level of bacterial cells exposed to heavy metals were evaluated by FTIR method.
The acid phosphatase-producing strain was identified as Enterobacter xiangfangensis. The highest MIC50 (3mM) and MBC (100mM) were obtained for nickel, and the highest metal removal percentage (75.89%) was obtained for the lead. Both nickel and lead were removed by the cells and secreted products. FTIR results showed Ni3(PO4)2 wavelength of 915.058cm-1 in cells treated with 3mM nickel.
Due to the high ability of the isolate in removing nickel and lead by cell surface and secreted materials, this isolate can be used in metal bioremediation. Though the phosphatase enzyme isolated from Enterobacter did not have any considerable effect on lead removal, it was able to remove nickel. Therefore, metal removal can be optimized by enzyme purification.

Infectious diseases are major economic losses in fish production facilities. Aeromonas hydrophila is considered as an important pathogen causing primary infection in wounds or the secondary problem following stress raised from temperature changes, handling, or poor water quality. This study was aimed to isolate A. hydrophila from crayfish Astacus Leptodactylus and to determine its virulence genes. Ten infected crayfish were investigated in this descriptive study. Samples were cultivated on Brain Heart Infusion (BHI) Agar medium. Bacterial identification was performed using both biochemical and molecular tests. Also, the presence of three virulence genes (lipase, elastase, and aerolysin) was investigated in the isolates. Two A. hydrophila strains were isolated from 10 infected crayfish with symptoms including black plaque, abscess, soft shell, corrosion appendages, and lethargy. One of the isolated strains had lipase and elastase genes, and the other one contained lipase, elastase, and aerolysin virulence genes. Our results showed the presence of different virulence genes in different A. hydrophila strains isolated from infected crayfish. Further studies are required to clarify the role of these genes in pathogenicity and virulence-related symptoms in the aquatic species.

Boxwood tree is one of the Iranian endemic trees expanded throughout Hyrcanian forests. They are of particular importance among the world's forest reserves. Recently, Calonectria pseudonaviculata has been considered as one of the most important causes of blight and leaf defoliation of the boxwood in Iran. For the first time, the present study was aimed to evaluate the genetic variation of Hyrcanian C. pseudonaviculata isolates using RAPD and ISSR markers.
Material & In this study, 75 fungal isolates were collected from the infected boxwoods throughout Hyrcanian forests in the North of Iran. The isolates were assessed based on morphology and colony color. Genetic diversity of the isolates was studied using RAPD and ISSR markers. A part of the beta-tubulin gene was sequenced and deposited at NCBI. Phylogenetic analysis was carried out using PAUP* v. 4.0b10.
The colony color of isolates on potato dextrose agar (PDA) medium was brown with pale hale, conidia were cylindrical, rounded at both ends, 1-septate, 48- 68 µm. Stipe was long (90-14 µm) and hyaline, with the extension terminating in a broadly ellipsoid papillate vesicle, the widest part above the middle. Phylogenetic tree based on the β-tubulin gene showed that all isolates are placed into the same group. Our results indicated that the population of this fungus has a low genetic diversity in Iran.
It seems that the variation of this pathogen is started to change genetically in some areas due to selection pressure phenomenon.

Thermophilic alpha-amylase can be used in different industries such as starch processing and detergents. This study was performed to isolate alpha-amylase-producing bacteria and characterization of the enzyme.
After sample collection from Gorooh hot spring in Kerman province, Iran, thermophilic alpha-amylase- producing bacteria were isolated using the starch-agar medium. 16S rDNA sequencing was used to identify the bacterial strain. Characterization of the thermophilic alpha-amylase was performed in the presence of various factors such as pH, temperature, metal ions, chemical compounds, and organic solvents. Also, kinetic parameters of the enzyme were determined in different concentrations of starch.
Anoxybacillus gonensis AT23 was identified as the best thermophilic alpha-amylase- producing strain. The alpha-amylase enzyme showed the optimal activity at pH 5 to 6. Sevenfold increase in the enzyme activity was observed in the presence of NaCl (3M). Mn2 and Zn2 increased the enzyme activity about 95% and 31%, respectively. Kinetic parameters including Km and Vmax were estimated about 1.657 mg/ml and 0.0059 mg/ml/min, respectively. Also, enzyme activity was also improved about 2 folds in the presence of organic solvents including n-butanol and 10% cyclohexane.
Our results indicated that AT23 alpha-amylase is a halophile and organic solvent-tolerant enzyme. Therefore, it can be used in different industries.