فصلنامه زیست شناسی میکروارگانیسم ها
پیاپی 2 (تابستان 1391)

Actinomycetes are well-known phytotoxin producing microorganisms. Nowadays the use of microbial herbicides versus traditional chemicals draws a great deal of attention as they do not cause any environmental problems. Actbacterial strains of 40 rhizospheric and phyllospheric samples were isolated. Primary screening was implemented on radish and cress seeds on GAP‌Agar. Then, bioassay of cell‌free broth of strains with more than 70% inhibitory effect on the seed growth was performed using GPM and SCD liquid media. Finally, compounds were extracted by organic solvents. The dry‌weight, production time and effectiveness of the superior isolate products were examined and three superior products were examined for their product effect spectrum by 10 resistant weeds. Among 457 screened isolates, 11 strains showed 70% or more inhibitory effect on GAP ‌medium. In secondary screening, seed growth inhibitions of 11 strains were more than 70% using cell‌free broth. These strains belonged to Streptomyces genus. According to dry weight products, production time and effectiveness PM2-2, TM14-5 and KB2-21 strains were selected for next steps and PM2-2 was the superior strain. Discussion and Streptomyces species are amog the best phytotoxins producers and the only phytotoxins introduced to the market are produced by the members of this genus. The growth inhibition of the most plant seeds examined by the isolated strains in this experiment showed an excellent potential for these phytotoxins. phytotoxins produced by some of the strains in the present study had high inhibitory effect and broad effect spectrum like commercial ones, so they seem to be economical.

Staphylococcus aureus exoproteins are known to have potent effects on cells of the immune system in human infections and their primary inhibitory effects in vivo on innate immune responses. The objective of this study was to determine the effects of bacterial extractions on viability of neutrophils and monocytes in the healthy and the infected cattle (mastitis). In order to isolate of neutrophils and monocytes, heparinized blood samples were taken from the healthy (n=5) and the infected cattles (n=5). Neutrophil and monocyte isolation was carried out using meglumine and histopaque compounds respectively. Secretory factors from Staphylococcus aureus ATCC23219 were extracted and its concentration assayed by Bradford method and were determined to be 400 μg/ml. The effect of different concentrations of the extract on viability of neutrophils and monocytes was determined by flowcytometery and immunoflorcent respectively. The results showed that in the healthy and the infected cattles, extract containing 800 and 400 μg/ml protein, respectively caused the most death in monocytes and neutrophils. It also seemed that in the infected cattles, monocytes were more sensitive to cell death than the neutrophils. Discussion and The extract of Staphylococcus aureus induces apoptosis and necrosis in both neutrophils and monocytes of both the healthy and the infected cattle but the cells in the cattle with mastitis are more sensitive to apoptosis than in the non- infected cattles. In the case of mastitis due to Staphylococcus aureus, the bacterial extracts effects on monocytes and not the neutrophils. However, determination of bacterial extraction fractions and their effect on immune system cells are strongly recommended.

Organic solvent-tolerant bacteria are relatively novel extermophilic microorganisms, which can produce organic tolerant protease with capacity of being used in industrial biotechnology for producing high-value compounds. Therefore, finding of these bacteria has drawn much researchers attention nowadays. In this project, samples were collected from a hot spring, located in Jiroft. Samples were incubated in medium supplemented with cyclohexane and toluene for 3 days. Screening of protease producing bacteria was performed on the specific media, SKM (Skim milk agar), based on clear area diameter. The best bacterium was identified based on 16s rDNA gene. Protease activity was considered in different temperatures, pH and organic solvents. Sequence alignment and phylogenetic tree results showed that this bacteria was closely related to Bacillus niacini, with 97% homology. Enzymatic studies showed that, this enzyme was active at a wide range of temperatures, 20-90 °C and it,s optimal activity was in 60 °C. In addition, maximum protease activity was obtained in the 8-9 range of pH, and optimal stability was also at pH 9.0. Protease activity in the presence of methanol, toluene, isopropanol, cyclohexane and DMF ‏showed that, remaining activity was at least 80% compared to the control (without organic solvent) Discussion and Thermopilic capacity, being active in alkaline protease and high protease stability in the presence of organic solvents all herald a remarkable application for using in different industries.

Urmia Lake, located in the northwest of Iran, is the largest permanent lake in Iran and one of the three permanent hypersaline lakes in the world. Microbial sampling from four western different regions of the lake was done and then, biodiversity of the samples were studied by culture dependent and culture independent methods. In culture dependent methods, halophilic and halotolerant bacteria were isolated under aerobic condition on four growth media, MH, SWN, MHLN and SWNLN. Differentiation of bacterial isolates was performed based on colony features, Gram staining and primary biochemical tests. In culture independent method, environmental DNA from water and soil samples were extracted. After 16S rRNA PCR amplification 16S rRNA library was constructed and 20% of clones were sequenced. Within 217 purified isolates in culture dependent methods, 52 strains were selected for 16S rRNA gene sequencing and representatives of Halobacillus, Halomonas, Planococcus, Gracilibacillus, Bacillus, Pontibacillus, Paracoccus, Marinobacter, Providencia, Staphylococcus, Alkalibacterium, Sanguibacter, Lysobacter, Kocuria, Pontibacter, Salicola, Micrococcus, Oceanobacillus, Brevundimonas, Thalassobacillus, Microbacterium and Piscibacillus genera were identified. In culture independent method, selected clones belonged to Salinibacter، Adhaeribacter and Cesiribacter genera. Discussion and In culture dependent selected strains 18 strains showed less than 98. 7% sequence similarity to the closest known strains and were representatives as new taxa of Urmia lake. In culture independent method selected clones belonged to Bacteroidetes category. Data obtained from this study were similar to other scientific reports from hypersaline lakes.

Mastitis is one of the most prevalent and important diseases in dairy cow herds. It is an inflammatory disease of mammary gland which is caused by many infectious agents. Streptococcus uberis and Streptococcus agalactiae have been frequently isolated from bovine mastitic milk. This research was carried out to study the prevalence of Streptococcus uberis and Streptococcus agalactiae in the milk of cows with clinical mastitis in industrial dairy farms around the province of Isfahan. In total, 123 milk samples were collected from cows with clinical mastitis and then, were immediately transferred to the laboratory. Mastitic milks were confirmed using California Mastitis Test and then, all samples were tested using microbial and biochemical tests. Finally, all 123 samples were tested using PCR. Culture results showed that 16% and 7.31% of the milk samples were positive for Streptococcus agalactiae and Streptococcus uberis, respectively. The PCR showed that 19.51% and 10.56% of the samples were infected with Streptococcus agalactiae and Streptococcus uberis, respectively. Discussion and This study showed that the Polymerase Chain Reaction has a higher accuracy and safety than the culture method. Therefore, we recommend the use of Polymerase Chain Reaction for inspection of microbial quality of milk samples.

Environmental contamination with petroleum is an important issue. Diesel oil is a common pollutant. Bioremediation is a new technology to clean up soils. This study was aimed to achieve microorganisms with power of soil cleaning. The bacteria of the contaminated soil with diesel oil were isolated based on morphological and biochemical characteristics. The degradation ability of the isolated bacteria was checked for the consumption of diesel fuel in the minimal salt medium containing different concentrations of diesel fuel (0.1, 0.5, 1 and 3%). Through the checking process, the turbidity due to the bacterial growth with the control tubes was compared. In the study, 10 different bacterial strains were found. Turbidity measurement results showed that the factors of time, concentration of the pollutant, bacterial strains and interactions between them were significant in all treated samples. In a particular pollutant concentration, as the time passed, the turbidity of the samples was exceeded. The increase rate of turbidity in the concentrations 0.1-1% was more dramatic than the 1-3% concentrations. 3 of the isolated strains in all concentrations caused a higher turbidity than other strains. Discussion and In the treated samples, the maximum turbidity was caused by the bacterium number 3, which late on, was identified as Pseudomonas aerogenesis. This bacterium was chosen as the best diesel oil degrader of the polluted soils with respect to the climatic conditions of as Hamedan’s.