فصلنامه دنیای میکروب ها
سال پانزدهم شماره 2 (پیاپی 51، تابستان 1401)

The high incidence of drug-resistant bacteria is currently a major global health concern, which, of course, calls for an immediate search for new antimicrobial mechanisms. Halocins synthesized by haloarchaea are usually stable at extremophile conditions and these features have given them great potential in the field of biotechnology. In the present study, literature search was performed based on search of antimicrobial peptides derived from archaea, in several online research tools, such as Pubmed Medline, Scopus, Google scholar, Elsevier databases, Irandoc, Iranmedex, Magiran, SID and MEDLIB limited to the articles published between 1992 to 2021.The reason for the use of   archaea antimicrobial compounds can be due to the mechanism of action and accuracy in identifying the target molecule, which has been proven in studies. But the production of pure halocin is very difficult due to the difficult techniques for culturing archaea and purification the active compounds produced.Antimicrobial peptides are attractive targets for drug development. Among the important uses of halocins, we can mention antimicrobial activity, preservative for salty food products, protection of tanned skin, prevention of heart damage, anti-cancer activity and as a tool for DNA absorption.

Helicobacter pylori (H. pylori) infection is accepted of chronic gastritis. Among the diagnostic methods, serological tests are widely available and relatively sensitive to detect H. pylori infection. However, the low specificity limits its application. The present study was aimed for designing, cloning and expression of UreB - Omp18 protein from Iranian H. pylori  strain as a promising diagnostic candidate with high specificity.

After extraction of genomic DNA from focal Helicobacter pylori strain, ureB and omp18 genes were amplified by primers designed for these genes by PCR reaction and cloned into pET-22b expression vector after enzymatic cleavage. The expression of the resulting recombinant protein was induced by IPTG and purified with high purity by affinity chromatography. The antigenic properties of the purified recombinant protein were confirmed by Western blotting.

In this study, two ureB and omp18 gene fragments were amplified by PCR as 597 and 479 bp fragments, respectively, and cloned as a hybrid fragment in the pET-22b vector. The expression of the recombinant protein in E. coli BL21 (DE3) appeared as a fragment of about 60 kDa on SDS-PAGE and was purified by Ni-NTA column. Western blot results of purified chimeric antigen with sera of H. pylori infected patients showed the antigenic properties of the recombinant protein.

In the present study, for the first time, the recombinant UreB-Omp18 protein was produced from the native strain of Helicobacter pylori, which can be a suitable candidate for designing a Helicobacter pylori diagnostic kit in the region.

Diphtheria and tetanus vaccine contains a high quantity of aluminum as an adjuvant potential to affect the nervous system, particularly in infants with kidney disease. Thus, the focus of this study was on in vitro preparation and evaluation to co-deliver DT toxoids by loading on alginate nanoparticles (NPs) as a non-toxic substance without antigenicity.

Using the gel-ionization method, alginate NPs samples were prepared and characterized in respect of size, zeta potential, and polydispersity index (PDI). The effects of alginate concentrations, calcium chloride, and Poly Lysine and the stirring time and speed in addition to the loading efficiency, loading capacity, and in vitro release profile were assessed.

The optimized NPs were prepared at a concentration of 0.02 %w/v sodium alginate, 0.1 %w/v calcium chloride, and 0.04% w/v Poly L-Lysine during 45 minutes of stirring at 1300 rpm. They also had a mean particle size <150 nm with a mean PDI of around 0.5. The appropriate  loading efficiency was obtained at a concentration of loaded toxoids similar to a conventional DT vaccine, which resulted in the prolonged release of about 85% of loaded toxoids over 120 hours. The SDS-PAGE and dot-blot confirmed the stability and antigenic activity of the released toxoids.

These results can significantly contribute to further developing alginate NPs containing DT toxoids in optimized in vitro conditions as a platform for in vivo evaluation to achieve a promising vehicle for immunization of infants and children against diphtheria and   tetanus.

Intestinal microbiota plays a key role in the overall function of the host, including host metabolism and obesity. In addition, due to their high fiber content, seaweed can regulate the intestinal microbial flora by stimulating the growth of beneficial bacteria and    inhibiting the growth of harmful species. The aim of this study was to evaluate the effect of Sargassum muticum on the intestinal microbial flora in obese rats.

Rats were fed with hot water (HW) and ethanolic(E) extracts of  Sargassum muticum for 8 weeks, then intestinal microorganisms were analyzed through 16S) rRNA sequencing in all groups.

The distribution ratio of intestinal microorganisms showed that Bacteroides and  Firmicutes are the dominant phyla in the intestine of rats. Analysis of microorganisms showed that obesity-related bacteria decreased and slimming-related genus increased in all treated groups. Clostridium was the predominant genus with pathogenic potential and Lactobacillus was the    predominant genus in the lactic acid group. In addition, seaweed-extracts-feeding obese mice had weight loss and reduced food intake compared with the obese control group.

Our results show that the consumption of  Sargassum muticum seaweed in the daily diet can balance the intestinal microbiota and also due to its high fiber, these seaweeds can cause weight loss in mice.

Plant growth-promoting bacteria in rhizosphere improve plants’ growth in different ways. In this study, the effects of five growth promoting bacteria, in the form of three biofertilizers were investigated on the chlorophyll a fluorescence changes of tomato seedlings.

The experiments were conducted as factorial based on a completely     randomized design. The bacteria were Azotobacter chroococcum, Azospirillum lipoferum,  Bacillus lentus, Pseudomonas putida and Acidithiobacillus thiooxidans; and biofertilizers were nitroxin, biosporphosphate and biosulfur. Chlorophyll a fluorescence changes were recorded using a Handy PEA device and analyzed by the JIP-test method.

The results showed that the use of Azotobacter chroococcum and Azospirillum ipoferum caused L band formation about 15 microseconds after light exposure, which revealed an improvement in the grouping and connectivity of antenna chlorophylls with photosynthetic reaction centers. Besides, the formation of the K band about 0.3 milliseconds after light exposure showed that the performance of the water-splitting complex was increased under the influence of Azotobacter chroococcum and Azospirillum lipoferum. The increase in electron transfer efficiency and the rate of reduction of the end electron acceptors in photosystem I were confirmed by the formation of J, H, and G bands in the presence of plant growth-promoting bacteria. 

The results of this study proved that the best photosynthetic performance in tomato plants including electron transfer between carriers of the photosynthetic electron transport chain occurred in the nitroxin bio-fertilizer containing Azotobacter chroococcum and Azospirillum lipoferum.

The coronavirus-19 pandemic is a major global health crisis. Covid-19 is a complex disease with diverse clinical features, from asymptomatic infection to acute respiratory distress syndrome (ARDS) and dysfunction of a number of organs. Prognostic  biomarkers are needed to quickly detect the severity of Covid-19, early in the course of the disease. The purpose of this study is to explain the amount of DNA break as a biomarker for disease prognosis in patients with covid-19.

The comet assay was used to compare the damage caused in the DNA of mononuclear lymphocytes in patients with covid-19 in 4 groups; control, hospitalized in the normal ward, hospitalized in the ICU and not intubated, hospitalized in the ICU and intubated.

The results of examining DNA damage in lymphocytes showed that covid-19 leads to cell damage and especially long-term intubation of covid-19 patients in the ICU, caused more DNA damage and caused more tails increase.

The comparison of tails in 4 groups shows that: in people hospitalized in the normal ward, cell damage was less, which could be due to the activation of DNA damage repair systems. As a result, DNA break of lymphocytes has a significant relationship with the prognosis of the disease in patients with Covid-19.  In this study, the comet assay was used to compare the damage caused in the DNA of mononuclear lymphocytes in patients with covid-19 in 4 groups; control, hospitalized in the normal ward, hospitalized in the ICU and not intubated, hospitalized in the ICU and intubated.