Advanced Research in Microbial Metabolite and Technology
Volume:3 Issue: 2, Summer-Autumn 2020

Due to the development and increasing cultivation of genetically engineered plants as an integral part of modern agriculture, the biosafety of soil microorganisms, essential elements of soil fertility, quality, and stability, has been discussed. To reveal the effect of transgenic plants on soil bio-diversity, it is necessary to compare the microflora of transgenic and parental plants. In this study, second-generation GM sugar beet seeds rendered resistant to the propagation of Necrotic yellow vein virus of beets (BNYVV) via gene silencing in a field trial were compared to their parental plant by analyzing 16S rDNA metagenomes with the use of the Illumina MiSeq platform. Analysis of the alpha and beta diversity found some influence on bacterial communication of rhizosphere between non-transgenic and transgenic (including 211S3, 219S3, 228S3, and 231S6 cultivars) sugar beets. Based on the results of the research on alpha diversity, the transgenic 211S3 and 219 S3 cultivars showed a lower average than the control sample in the Cho, phylogenetic diversity, Cho1 bias correction, and the number of OTUs indexes; The transgenic 231S6 cultivar showed a significantly higher mean than the control sample in the Simpsons index. Also, in the study of beta diversity based on the Bray-Curtis distance algorithm, all 211S3, 219S3, 228S3, and 231S6 cultivars and control samples were positioned in one group. According to the Unweighted UniFrac distance algorithm, 219S3 and 231S6 cultivars were put together in one group, and 211S3 and 228S3 cultivars were classified into one group. A comparison of the bacterial genera showed a noteworthy reduction in relative abundance. While a few genera showed a significant decrease in terms of overall abundance, other genera that stabilize molecular nitrogen and motivate plant growth, such as Agrobacterium, Devosia, Mesorhizobium, Burkholderia, and Bradyrhizobium, showed a significant decrease compared to the control cultivar in all transgenic beets.

Yeast extract obtained by hydrolysis of Saccharomyces cerevisiae as a baker yeast provides a high nutritional value for pharmaceuticals, food industries, microbial substrates, and biofuels. Two methods are typical to produce yeast extract, autolysis and hydrolysis. In this study, the rapid and cost-effective process of the hydrolysis method, including the mechanical methods of high temperature and pressure, was utilized to produce the yeast extract. The purpose of this study was to compare three methods, the Spray dryer, freeze dryer, and oven dryer methods, of preparing powder from bakery yeast extract. The effects of the produced yeast extracts were measured on gram-negative and gram-positive bacteria that were given as a bacteria feed to test the quality of products. The extract obtained from the freeze and spray dryer methods accelerated the growth rate of microorganisms. The bacteria Staphylococcus aureus and Escherichia coli showed better overall growth on the yeast extract attained from the spray dryer method. Hence, the produced spray dryer yeast extracts significantly improved the soluble expression and purification of the protein compared to the commercial extract. Results revealed that the spray dryer method preserves the properties of the yeast extract better than the other methods, and due to low moisture, this method can be used in industry. Nevertheless, all methods are applicable for yeast extract production.

Green methods are environmentally friendly methods for the synthesis of nanoparticles. These methods use a wide range of biological and reducing agents produced by bacteria, fungi, yeasts, algae, and plants for making metal nanoparticles. The object of this study was the extracellular synthesis of silver nanoparticles using rice bran by Isoptericola variabilis and the subsequent comparison of the antibacterial activity of the synthesized optimized and non-optimized silver nanoparticles. Optimal conditions for producing silver nanoparticles were obtained using an experimental response surface methodology (RSM) design. Nanoparticles were characterized by SEM, FT-IR, and UV-visible spectroscopy. Antibacterial activity of the silver nanoparticles (AgNPs) was investigated using the disk diffusion method against E.coli on Mueller Hinton agar medium. The SEM images of the optimized AgNPs showed an increase in uniform generated spherical nanoparticles. In addition, optimizing the production conditions of nanoparticles not only developed their antibacterial activity but reduced their sensitivity threshold compared with synthetic nanoparticles in the initial conditions. The effective concentration of nanoparticles against E. coli decreased from 500 μg/mL to 100 μg/mL (a 5-fold reduction). In conclusion, silver nanoparticles can be produced by Isoptericola variabilis, and its optimization process not only led to increased productivity but also improved the antibacterial efficiency against E. coli.

The selection of putative antagonists for the biological control of plant diseases usually involves collecting and screening large numbers of microbial isolates so as to increase the probability of discovering highly effective strains. Different strains of Bacillus velezensis produce secondary antifungal metabolites that could control plant diseases. The ability to form spores makes this bacterium an ideal candidate for biological control. Isolation, characterization, and identification of B. velezensis (native to Iran) from soil and its antifungal activity against Fusarium sp. have been reported in the present study. Eight out of 75 isolates showed antifungal activity against three main species of Fusarium under standard conditions. The morphological and biochemical characteristics, along with the 16S rRNA and gyrB genes sequences of the selected isolate, indicated that it belongs to the B. velezensis species. The results showed that sucrose as a carbon source and peptone as a nitrogen source in a culture medium at pH 7 and an agitation speed of 200 rpm led to the maximal growth rate and antifungal activity in the B. velezensis sp.RTS-M11 selected strain. This isolate seems potentially useful as a biological agent against a few Fusarium sp. but needs more study in the future.

S. platensis has received much recent attention because of its potential application in the prevention and/or managing of cancer, and many other diseases. However, little is known about the effects of S. platensis on the antioxidant defense system, therefore this study aimed to investigate the effects of this microalga on the function and structure of the antioxidant enzyme catalase. The catalase activity was measured under steady-state kinetic conditions. The spectrophotometric methods including ultraviolet-visible absorption, circular dichroism spectroscopy, and fluorescence spectroscopy executed to understand the S. platensis-induced alterations in catalase. The results showed that S. platensis extracts at low concentrations stimulated catalase activity, whereas at higher concentrations inhibited catalase activity in a non-competitive manner. Catalase activity was inhibited by 27% and 80% using the aqueous and methanol extract, respectively. The Stern-Volmer plots indicated that S. platensis methanolic extract quenched catalase fluorescence emission with both static and dynamic mechanisms. The values of thermodynamic parameters for the S. platensis extract-catalase complex indicated that the binding reaction is a spontaneous and exothermic process and hydrogen bonds and van der Waals forces play a major role in the binding of compounds in S. platensis extract to catalase. The number of binding sites was obtained ~2. Circular dichroism spectroscopy data represented that high concentrations of S. platensis extract lead to a significant decrease in the content of α-helix and ß-sheet (p < 0.05) accompanied an increase in random coil content of the enzyme. According to the results, it can be concluded that the application of S. platensis extract has a dual effect on the structure and function of catalase, stimulatory or inhibitory, depending on its concentration. Therefore, it may have potential benefits as an antioxidant or tumor suppressor.

Halobacterium salinarum as a model organism has been used for archeal genomics studies in many investigations. This well-known microorganism loves hyper saline habitat and transformation of DNA for genetic manipulation of the halophile by conventional methods eg. electroporation is impossible and current specific procedure is time consuming, sensitive and difficult. Therefore the development of easy and efficient methods for genetic manipulation especially transformation of this species are important. In this study we introduced a simple method for H. salinarum transformation with high efficiency. This method is based on the controlled short time swelling- deswelling of this halobacterium. Exposure of the halophile to hypo-osmotic shock was done by adding deionized water containing the desired plasmid to the cell suspension that decreased NaCl concentration to around 2.5 M. After 60 seconds the shock removed by the re-increasing salt concentration of suspension to 3.3M. During the osmotic shock plasmids from low concentrated fluid gets sucked in through the cell membrane. Transformation confirmed by PCR and colony count. In comparison with conventional PEG mediated method the frequency of 105 transformants/µg of DNA revealed that osmotic shock is an efficient transformation method in H. salinarum. Consequently this easy and fast transformation method could be used instead of other laborious methods in this microorganism and probably to transform other halophiles