فصلنامه دنیای میکروب ها
سال دهم شماره 3 (پیاپی 32، پاییز 1396)

Zarshuran gold mine as the largest gold mine in Iran is located in Takab, West Azarbayjan. In this study, for the first time, the ability to isolate the gold element was examined by providing optimal conditions for the growth of natural microorganisms in Zarshuran gold ores and investigating the effect of different factors including pH, leaching time and the ratio of the ore volume to leachate.
The study was designed using the Taguchi method in three levels to evaluate the effect of each of the pH, leaching time and the ratio of the ore volume to leachate. The effect of each factor and the appropriate level for bioleaching refractory gold was investigated using the Qulitek-4 software.
The most effective factor was the ratio of the ore volume to leachate which was 17.20% and the least effective factor was the leaching time which was 7.84%. The level 3 was the most appropriate pH level which was assessed as 59.46%. The most appropriate level for the ratio of the ore volume to leachate was level 1, with the amount of 66.14% and a ratio of 1/1. The most appropriate level for the time was level 1, as well, with the amount of 56.78% and duration of 30 days.
Considering the three functional environmental factors, much gold can be separated from ore at an industrial scale without spending too much money.

Efflux pumps are one of the mechanisms for antibiotic resistance in Acinetobacter baumannii isolates. The aim of the present study was to investigate the green synthesis of silver nanoparticles using Acroptilon repens extract and evaluation of its anti- efflux activity in antibiotic-resistant A. baumannii isolates.
In this experimental study, the silver nanoparticles were synthesized using A. repens alcoholic extract and the structure of the synthesized silver nanoparticles was confirmed by spectrophotometry (UV-Vis), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Subsequently, the adeAC efflux pump was detected in 21 A. baumannii clinical isolates using Cartwheel and Polymerase Chain Reaction (PCR) methods. Finally, the anti-efflux pump activity of silver nanoparticles was evaluated by Minimum Inhibition Concentration (MIC) technique.
The synthesized silver nanoparticle was confirmed by maximum absorbance at 420 nm wavelength, using UV-Vis method. The SEM and TEM micrographs showed that nanoparticles are spherical and have an average size of 38.89 nm. Moreover, the XRD results confirmed the cubic structure of silver nanoparticles. The results of Cartwheel and PCR methods revealed that the 12 out of 21 isolates have active efflux pumps. Furthermore, the MIC of ethidium bromide in resistant strains with silver nanoparticles was decreased.
Based on anti-efflux pump activity of silver nanoparticles against A. bumannii strains, it seems that silver nanoparticles have potential uses for pharmaceutical industries, though further studies are required to confirm the results of this study.

Curcumin as a natural phenolic compound derived from Curcuma longa plant has shown an antifungal property. Candida albicans is the most common opportunistic fungal pathogen. Continuous deployment of antifungals against this pathogen has led to the emergence and increasing of the multi-drug resistance. In this study, the effect of nanoparticle-encapsulated curcumin on CDR1 gene expression was evaluated in fluconazole-resistant isolates of C. albicans.
In this study, 6 fluconazole-resistant isolates of C. albicans were treated just by fluconazole (1/2MIC) as the control sample and in the combination with nanoparticle-encapsulated curcumin as the test sample. After 24h, two cell groups were cultured in Sabouraud Dextrose Agar to estimate cell death percentage. Following RNA extraction and cDNA synthesis, CDR1 gene expression was investigated quantitatively by real-time PCR method in both curcumin-treated and untreated cells.
Our findings showed that the combination of fluconazole (1/2MIC) and nanoparticle-encapsulated curcumin treatment reduces the fungal growth by 50% after 24 h. Moreover, quantitative real-time PCR analysis revealed that nanoparticle-encapsulated curcumin decreases the expression level of CDR1.
Our findings suggested that curcumin can inhibit fungal growth through different mechanisms such as decreasing the number of ABC efflux pumps at the cell surface and synergically increases the antifungal effect of fluconazole in resistant isolates of C. albicans.

Feather is one of the environmental pollutants that about 90% of its weight is made of highly resistant creatine plates. A number of bacteria are able to produce a keratinase enzyme in the presence of keratin substrate. The purpose of this study was isolation and molecular identification of keratin- degrading bacteria from the soil of poultry farms around Marvdasht city in order to measure keratinase activity in superior creatine-degrading strains.
Material & In this study, 15 soil samples from poultry farms around Marvdasht city was collected. Seven bacterial isolates were cultured on a feather meal medium. Five isolates that showed clear degradation zone, were chosen for further chemical and molecular identification. The bacteria were sequenced, and a specific accession number in the gene bank was allocated to each of them as a new strain Then, all five isolates were assessed for the level of keratinase enzyme production.
All isolates belonged to Bacillus species. All five isolates were able to completely degrade keratine. The most keratinase activity was reported 17.12 (ml/min) for Bacillus cereus SKH1.
Different species of Bacillus in this study showed the ability to produce a keratinase enzyme in the presence of keratin substrate. Investigating the level of keratinase activity in bacterial isolates showed that all have the potential treat feather waste.

Deep bark canker is a disease which is caused by Brenneria rubrifaciens, and reduces the quality and quantity of Walnut fruits. This study was performed to identify the bacterial agent of deep bark canker based on morphological characteristics, pathogenicity and using specific primers for the genes involved in rubrifacien pigment production.
This cross-sectional- descriptive study was performed on walnut trees with canker symptoms in Lorestan Province. Following purification, bacterial identification was performed using the phenotypic characteristics of the bacterial isolates. Further evaluation of the canker agent was carried out using 2BrIF/2BrIFR and GSP2F/GSP2R primers. Also, the virulence properties of the bacteria were tested on walnut seedling and fruits.
Based on the phenotypic characteristics, 14 isolates were identified as B. rubrifaciens. 671 and 280 bp fragments were amplified in the isolates the during PCR test. In pathogenicity test, symptoms of a rotted and blackened tissue were observed at the site of inoculation. In the phylogenetic analysis, two isolates showed 97% and 98% homology with the bacterial isolates identified in the Genbank.
Comparing other methods, PCR using specific primers is a fast, functional and highly sensitive method to detect B. rubrifaciens. Based on our results on the pathogenicity potential of the strains and the occurrence of the symptoms on walnut seedlings, the pathogen under favorable conditions suffers severe damage to the trees.

Yersinia enterocolitica is a Gram-negative intestinal pathogen that is transmitted to humans through water and food. Milk is one of the main sources of the infection transmission to humans and its contamination with bacteria such as Y. enterocolitica can cause serious damages. The present study aimed to isolate Y. enterocolitica and its virulence genes from small ruminant milk in Shahrekord, Iran using microbial culture and PCR method. In this cross-sectional descriptive study, 100 raw milk samples were collected randomly from different parts of Shahrekord, and cultured on a CIN agar medium. In order to detect Y. enterocolitica O:3 serotype and toinvestigate the presence of virulence genes, positive- culture samples were further assessed by PCR method using specific primers. According to the results, 9% of total sheep and goat milk samples were positive after microbial culture. Notably, all positive samples were sheep milk samples. Five percent of the positive samples were confirmed as O:3-positive serotypes using PCR method. The ail gene was found in four isolates, the yadA gene was reported in three isolates, and the virF and ystA genes were identified in two isolates. Isolation of Y. enterocolitica from raw milk was indicated high risks of yersiniosis associated with raw sheep milk. Based on our results, sheep's milk can be considered as a potential cause of human infection to Y. enterocolitica.

Lactic acid bacteria are essential factors for obtaining optimum sensory aspects in fermented meat. The aim of this study was the enhancement of cow meat quality by optimization of acid production using Lactobacillus sakei and Lactobacillus plantrum in batch fermentation.
In this cross-sectional descriptive study, L. sakei subsp. sakei PTCC1712 and L. plantrum PTCC1058 were grown in MRS medium and confirmed by molecular identification. Using Taguchi software (16 version), trials were designed to optimize three factors including temperature, bacterial inoculation, and glucose supplementation. The results were analyzed based on detection of acid production and compared by ANOVA program. Total product bacteria, lactic acid bacteria, Enterobacteriaceae, and yeasts/molds were counted by standard microbial methods.
Maximum acid production for L. sakei was detected at 36 ºC, 10% glucose and 8000 CFU.g-1 inoculated bacteria; and for L. plantarum was detected at 37 ºC, 10% glucose, and 9000 CFU. g-1 inoculated bacteria. The best factor affecting pH decline was a carbon source for both bacterial strains. Lactic acid bacteria showed a fourfold increase after fermentation and maintained 60% of their viability following heating stage. No Enterobacteriaceae was found in the product, and other pathogens showed a great decrease. Using both strains simultaneously, 6.9% improvement in acid production was observed.
Both Lactobacillus strains had similar conditions for cow meat fermentation and showed synergistic activity for acid production when used simultaneously.

The effect of different levels of potassium fertilizers on sorghum inoculated with mycorrhizal fungi (Glumus mossea) was evaluated under water stress condition in a split-plot experiment, based on randomized complete block design in four replicates.
Materials & MethodsTreatments were carried out in three different levels of stress including irrigation after 40, 80 and 120 mm evaporation from pan evaporation class A (S1, S2, and S3, respectively); three different levels of potassium chloride fertilizer treatments including without fertilizers, 75 kg and 150 kg/hec of potassium chloride (K1, K2 and, K3, respectively). The studied parameters were plant height, number of tiller per plant, flag leaf length, panicle length, and fresh and dry forage yield.
Our results indicated that the maximum value of all measured parameters obtained from S1. Increasing water stress resulted in a decrease in both yield and growth rate. Furthermore, among K treatments, maximum panicle length and fresh and dry forage yield obtained from K3. Correlation study showed a positive correlation between forage yield of sorghum and height and diameter of the stem.
Among the applied treatments, the optimal amount of potassium chloride fertilizer was 150 kg/hec along with irrigation after 40 mm evaporation from the evaporation pan.