فصلنامه دنیای میکروب ها
سال یازدهم شماره 2 (پیاپی 35، تابستان 1397)

Iran continues to hold one of the most currently active world foci of agalaxy in ruminants. The three local strains of Taliqan, Lorestan, and Shiraz have been used for many years in preparation of the only commercially available killed vaccine against agalaxy in the Iranian market. This study was conducted to determine the genetic link between these strains.

All three strains of Taleghan, Lorestan, and Shiraz were cultivated freshly on PPLO agar media. The genetic material was extracted by boiling method. In order to investigate the genomic relations between these strains, a Multi-Locus Variable Number Tandem Repeat Analysis (MLVA) strategy concentrating on 4 VNTR loci of 5, 9, 17, and 19 was employed. The nucleotide sequences of all PCR products were determined, as well.

Nucleotide sequence analysis showed an identical MLVA pattern by all the three strains. When compared to the Mycoplasma agalactiae PG2 laboratory strain, the only VNTR19 locus was different between Iranians and the PG2 strain, with respect to a 3bps addition at this locus in Iranian strain.

The identical genetic pattern of the three Iranian strains is likely an indication of the activity of one or more indigenous ancestral clone in the geography of Iran that has been appeared and evolved throughout its livestock history and became homogeneous and predominant due to the absence of efficient disease control policies. The similarity between three Iranian and the PG2 strains might be due to homoplasy or human intervention through animal husbandry activities such as livestock importation. Applying standard genotyping methods to a larger number of local isolates help to better assess this observation

Leishmaniasis is an infectious disease that is caused by an obligate intracellular parasite which belongs to genus Leishmania, order Kinetoplastida. Using bio-microbial control agents as one of the alternative therapies for leishmaniasis infections has been developed. The aim of this study was to assess Bacillus thuringiensis crystal protein effects against Leishmania tropica parasite.

In this cross-sectional descriptive study, 47 B. thuringiensis isolates from soil samples in different regions of Fars province were collected based on the phenotypic characteristic, crystal toxin staining, and molecular identification. After enzyme digestion of toxin isolates using Proteinase K, their cytocidal effects on L. tropica were analyzed. The isolates with the most toxicity effect were identified by PCR.

Our results identified one isolate with the most cytocidal effect on L. tropica. The sb35 isolate crystalline toxin (Cry1) was the most effective toxin on Leishmania, showing the highest cytocidal effect (about 40%) at the concentration of 10-1 mg/ml. Cytopathic effects of promastigote treatment with crystallized toxins were observed as shrinking and inflammation.

Considering the results obtained in this study, using crystallized proteins of B. thuringiensis can be considered as an appropriate candidate for treating leishmaniasis by performing complementary studies

The prevalence of infection, along with the spread of antibiotic-resistant bacteria has caused the antibacterial peptide, bacteriocins, to be considered. The purpose of this study was to compare the antibacterial effect of bacteriocin-producing bacteria. The inhibitory activity of bacteria isolated from different regions of Semnan soil, Dasht Desert (Semnan University Bacterial Culture Collection; DDBCC) was studied against the indicators by agar diffusion method. Candidate strains were identified by biochemical and molecular tests. Concentrating the selected bacteriocins by ammonium sulfate saturation, the effects of biofilm destruction were studied. Then, using a thin layer chromatography the selected bacteriocins were purified and their antimicrobial activity was confirmed. The 16s rRNA sequencing results showed 98% similarity of DDBCC38 and DDBCC51 isolates to E. coli and 96% similarity of the DDBCC46 isolate to Bacillus subtilis. Concentrated DDBCC51 and DDBCC38 bacteriocins inhibited the growth of Bacillus cereus, Bacillus anthracis, and Klebsiella pneumonia after 52 hours. Pseudomonas aeruginosa and Staphylococcus aureus biofilms were destructed by DDBCC51 and DDBCC38 bacteriocins 12.0% and 40.0%, and 19.6% and 40%, respectively. In contrast, concentrated DDBCC46 bacteriocin was effective on K. pneumonia and P. aeruginosa in 72 hours but had no effect on biofilm destruction. The purification of DDBCC38 and DDBCC51 bacteriocins by thin layer chromatography resulted in 2 mm increasing of inhibition zone diameter against K. pneumoniae. However, purified DDBCC46 bacteriocin reduced it by 4 mm. Considering the anti-biofilm and antagonistic properties of the respective isolates, further studies for optimization of the production conditions and molecular identification of the produced
bacteriocin are proposed

Salmonella enteritidis causes a number of infections in humans and other animals. Though different antibiotics are used to eliminate bacterial infections, due to the development of antibiotic resistance after a while, the use of nanoparticles has been considered as suitable alternatives. Chitosan nanoparticles are appropriate options for the intended strategy due to some properties including low molecular weight and biodegradability. Therefore, the aim of this study was to evaluate the antibacterial effect of chitosan nanoparticles against S. enteritidis. Standard bacterial strain was prepared and subsequently confirmed by PCR technique. Ionic gelation method was used to fabricate chitosan nanoparticles and Hole-Plate and tube dilution methods were used to check the chitosan nanoparticles anti-microbial properties with antibiotics. At last Zeta's analysis techniques, dynamic optical scanning, and electron microscopy were used to evaluate nanoparticles. A 214 base pair band confirmed the presence of bacteria. Chitosan nanoparticles with low molecular weight were produced by analyzing the results of optical dynamics scattering (111.7 nm), zeta analysis (20.8 mV) and microscopy ( There is a significant relationship between the chitosan nanoparticles resistance and antibiotics against bacteria. In other words, the nanoparticles antibacterial properties were higher than antibiotics. It is deduced that chitosan nanoparticles can be used to control diseases and to destroy resistant bacterial species

The use of biological processes and optimizing them in order to produce biofuels such as ethanol is very important due to economic and environmental issues. Therefore, this study was conducted to investigate the kinetic model of starch enzymatic hydrolysis by Aspergillus niger and ethanol production using Saccharomyces cerevisiae. The study was performed on a laboratory scale. The effect of different parameters such as pH and temperature on starch enzyme hydrolysis by A. niger was investigated. Also, the Michaelis-Menten’s model was used to assess the Kinetic model of the enzymatic hydrolysis process. In order to produce ethanol from the hydrolyzed starch, S. cerevisiae (yeast) was used at the temperature of 25 °C and pH of 4.5. The results showed that the pH of 5 and the temperature of 35 °C have the highest effect on glucose production by A. niger. In addition, assessment of the kinetics and the constants of the model measured Vmax and Km as 10.41 and 73.23, respectively. Comparison between the experimental data and those predicted from the rate model indicated good agreement (R2= 0.93). The results of ethanol production by S. cerevisiae on hydrolyzed medium with glucose initial concentration of 32 g/l showed the maximum ethanol production and cell dry weight as 10.04 g/l and 3.08 g/l, respectively. According to the results of this study Michaelis–Menten kinetics model is able to predict enzymatic hydrolysis of starch. Furthermore, hydrolyzed starch can be used as an appropriate substrate for ethanol production.

Today, soils and waters polluted by petroleum compounds are major environmental problems. A major part of the harmful effects of oil is due to thiophenic compounds such as dibenzothiophene and other sulfur derivatives, with increasing evidence of toxicity, carcinogenicity and their relative sustainability in nature. The purpose of this study was to investigate the possibility of biodegradation of these pollutants by microorganisms that have spread over the years in the presence of gas oil. In order to study the feasibility of dibenzothiophene usage by isolated microbial consortia, firstly, appropriate growth medium with dibenzothiophene as the sole sulfur source was made and the biomass of the microorganisms was chased for 10 days. In order to estimate the metabolic degenerative pathway of this compound, 2-Hydroxybiphenyl was tracked in the selective consortium growth medium. Finally, the effect of the consortium on thiophene, 2-methylthiophene and thiophene-2-carboxylic acid was investigated, as well. Increasing biomass and eliminating dibenzothiophene in the presence of a microbial consortium and the absence of 2-Hydroxybiphenyl showed the consortium's ability to degrade this compound, but with a biochemical pathway other than 4S. The consortium was able to take thiophene and 2-methylthiophene, as well. The biodegradation activity and the scope of the substrates in comparison with conventional microorganisms suggest this consortium as a valuable biocatalyst for the decontamination of thiophenic contaminants

Today, crude oil products are one of the most widely used chemicals in the world. Daily, large volumes of crude oil and their derivatives are poured into the environment. The aim of this study was to isolate and evaluate Iranian indigenous yeast strains for the purpose of bioremediation of crude oil pollutants. Soil samples were collected from different oil-contaminated areas of Iran. The samples were cultured for 14 days on Bushnell Hass medium containing 0.5 % crude oil and 100 mg l-1 tetracycline. The crude oil degradation was measured by TPH assay at 420 nm. Removal of 100 ppm of phenanthrene, anthracene, and pyrene as model polycyclic aromatic hydrocarbons (PAHs) was studied using HPLC method. The superior yeast strain was identified by ITS gene sequencing and alignment in the NCBI database. Totally, 47 yeast strains were isolated. TPH assay showed that FA14 isolate with 89% degradation rate within 14 days was the most powerful isolate in the removal of PAHs. ITS gene sequencing followed by alignment in NCBI indicated that FA14 belongs to the genus Exophiala sp., showing 99% similarity. Furthermore, the results indicated that within 14 days phenanthrene, anthracene, and pyrene were degraded by FA14 with the rate of 97.67 %, 57.0 %, and 95.38 %, respectively. Our results showed that Exophiala sp. has a high ability for biodegradation of crude oil and PAHs. Therefore, it could be introduced as a potent strain for bioremediation of oil-contaminated soil samples

Shigella sonnei is the main agent associated with shigellosis in developed as well as developing countries. Finding alternative methods to control Shigella transmission (foods, drinking water and person to person contact) seems necessary due to the appearance of multidrug-resistant strains among Shigella spp. This study aimed to evaluate the potential of vB_SsoS-ISF002 phage in bio-controlling of S. sonnei in food products. Changes in the S. sonnei (ATCC 9290) count, as well as the propagation of its specific bacteriophage (vB_SsoS-ISF002), were measured in two trial treatment and prevention phases for a period of 144 hours. The phage (108 PFU/g) was added to raw or cooked chicken breast after (in treatment phase) or before (in prevention phase) inoculation with S. sonnei at 2, 24 or 48 h. vB_SsoS-ISF002 phage was capable to reduce S. sonnei growth by at least two logs of viable in both treatment and prevention phases. It was shown that vB_SflS-ISF001 phage has a high potential to be used as a non-chemical preservative and the bio-controlling agent against S. sonnei contamination in the food industry