Noninnocent effect of axial ligand on the heme degradation process: a theoretical approach to hydrolysis pathway of verdoheme to biliverdin

Conversion of iron(II) verdoheme to iron(II) biliverdin in the presence of hydroxyl ion as a nucleophile and imidazole, pyridine, water, hydroxyl, cyanide, phenolate, chloride, thiolate and imidazolate as axial ligands was investigated using the B3LYP method and the 6-31G basis set. In the five-coordinated pathway the reactants and products are in the ground triplet state. In this path, hydroxyl ion directly attacks the macrocycle. The exothermic energy for addition of hydroxyl ion to iron(II) verdoheme with various ligands is 169.55, 166.34 and 164 kcal mol⁻¹ for water, pyridine and imidazole, energies which are around 30–60 kcal mol⁻¹ more exothermic than those for the other axial ligands used in this study. Therefore, imidazole, water and pyridine axial ligands can facilitate hydrolytic cleavage of iron(II) verdoheme to form open-chained helical iron(II) biliverdin complexes. The activation barrier for the conversion of iron(II) verdoheme hydroxyl species to the iron(II) biliverdin complex is estimated to be 5.2, 4.2, 4.35, 13.76 and 14.05 kcal mol⁻¹ for imidazole, water, cyanide, thiolate and imidazolate, respectively. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Discovery of single nucleotide polymorphisms and mutations by pyrosequencing

Comparative genomics, analyzing variation among individual genomes, is an area of intense investigation. DNA sequencing is usually employed to look for polymorphisms and mutations. Pyrosequencing, a real-time DNA sequencing method, is emerging as a popular platform for comparative genomics. Here we review the use of this technology for mutation scanning, polymorphism discovery and chemical haplotyping. We describe the methodology and accuracy of this technique and discuss how to reduce the cost for large-scale analysis.     

Prevalence of ESBL and MBL encoding genes in Acinetobacter baumannii strains isolated from patients of intensive care units (ICU)

The aim of this study was to investigate the prevalence of ESBL and MBL encoding genes among A. baumannii isolates. In this cross sectional study, 100 A. baumannii strains were isolated from ICU wards of 3 educational hospitals of Hamadan City, Iran in 2011. Phenotypic identification of the production of ESBLs and MBLs has been carried out by using E-test and DDST methods, respectively. PCR technique was used for amplification of the ESBL and MBL encoding genes, namely: CTX-M, SHV, TEM, OXA-51, VIM-Family, IMP-Family, SPM-1, SIM-1, and GIM-1. Eighty seven (87%), 95 (95%), 98 (98%) and 95 (95%) out of 100 A. baumannii isolates were resistant to imipenem, meropenem, ceftazidime and cefotaxime, respectively. Also, 99% and 7% of the isolates were MBLs and ESBLs produced phenotypically. Thirty (30%), 20 (20%) and 58 (58%) out of 100 A. baumannii isolates have been confirmed to harbor the bla_VIM-family, TEM and SHV genes, respectively. Our results show no significant relationship between the detected gens with production of MBLs and ESBLs in spite of high prevalence of MBL encoding and drug resistant A. baumannii. Probably some other genes rather than what we studied are involved in phenotypic production of MBLs and ESBLs and subsequent drug resistance in Hamadan area, Iran.     

The possible role of bacteria,viruses, and parasites in initiation and exacerbation of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a prolonged and disabling functional gastrointestinal disorder with the incidence rate of 18% in the world. IBS could seriously affect lifetime of patients and cause high economic burden on the community. The pathophysiology of the IBS is hardly understood, whereas several possible mechanisms, such as visceral hypersensitivity, irregular gut motility, abnormal brain–gut relations, and the role of infectious agents, are implicated in initiation and development of this syndrome. Different studies demonstrated an alteration in B-lymphocytes, mast cells (MC), T-lymphocytes, and cytokine concentrations in intestinal mucosa or systemic circulation that are likely to contribute to the formation of the IBS. Therefore, IBS could be developed in those with genetic predisposition. Infections’ role in initiation and exacerbation of IBS has been investigated by quite several clinical studies; moreover, the possible role of some pathogens in development and exacerbation of this disease has been described. It appears that the main obligatory pathogens correspond with the IBS disease, Clostridium difficile, Escherichia coli, Mycobacterium avium subspecies paratuberculosis, Campylobacter concisus, Campylobacter jejuni, Chlamydia trachomatis, Helicobacter pylori, Pseudomonas aeruginosa, Salmonella spp, Shigella spp, and viruses, particularly noroviruses. A number of pathogenic parasites (Blastocystis, Dientamoeba fragilis, and Giardia lamblia) may also be involved in the progression and exacerbation of the disease. Based on the current knowledge, the current study concludes that the most common bacterial, viral, and parasitic pathogens may be involved in the development and progression of IBS.     

A Chronic Autochthonous Fifth Clade Case of Candida auris Otomycosis in Iran

Candida auris, a multidrug-resistant nosocomial pathogen, has emerged globally with high morbidity and mortality among immunocompromised individuals and COVID19 hospitalized patients. Five major clades of C. auris have been previously described. The fifth clade is exclusively found in Iran where C. auris isolates are genetically distinct from other clades by?>?200,000 single-nucleotide polymorphisms. The origin of C. auris remains unclear, and limited clinical data are available at present regarding clade V infection or colonization. Herein, another case of otomycosis in Iran caused by an isolate of C. auris belonging to the fifth clade is reported. Genotyping revealed that the obtained C. auris isolate from Isfahan clustered with earlier clade V isolates from Babol, cities around 600 km separated, which indicates that C. auris clade V is established in Iran. C. auris is thought to exist more commonly in Iran, given that limited diagnostic capacity in the country has probably curbed the identification of more C. auris cases. Therefore, surveillance of the environment, patients and healthcare facilities in different geographical regions in Iran is urgently required.

     

Contribution of Fdh3 and Glr1 to Glutathione Redox State,Stress Adaptation and Virulence in Candida albicans

The major fungal pathogen of humans, Candida albicans, is exposed to reactive nitrogen and oxygen species following phagocytosis by host immune cells. In response to these toxins, this fungus activates potent anti-stress responses that include scavenging of reactive nitrosative and oxidative species via the glutathione system. Here we examine the differential roles of two glutathione recycling enzymes in redox homeostasis, stress adaptation and virulence in C. albicans: glutathione reductase (Glr1) and the S-nitrosoglutathione reductase (GSNOR), Fdh3. We show that the NADPH-dependent Glr1 recycles GSSG to GSH, is induced in response to oxidative stress and is required for resistance to macrophage killing. GLR1 deletion increases the sensitivity of C. albicans cells to H₂O₂, but not to formaldehyde or NO. In contrast, Fdh3 detoxifies GSNO to GSSG and NH₃, and FDH3 inactivation delays NO adaptation and increases NO sensitivity. C. albicans fdh3⎔ cells are also sensitive to formaldehyde, suggesting that Fdh3 also contributes to formaldehyde detoxification. FDH3 is induced in response to nitrosative, oxidative and formaldehyde stress, and fdh3Δ cells are more sensitive to killing by macrophages. Both Glr1 and Fdh3 contribute to virulence in the Galleria mellonella and mouse models of systemic infection. We conclude that Glr1 and Fdh3 play differential roles during the adaptation of C. albicans cells to oxidative, nitrosative and formaldehyde stress, and hence during the colonisation of the host. Our findings emphasise the importance of the glutathione system and the maintenance of intracellular redox homeostasis in this major pathogen.