The order Mucorales is an ancient group of fungi classified in the subphylum Mucoromycotina. Mucorales are mainly fast-growing saprotrophs that belong to the first colonizers of diverse organic ...materials and represent a permanent part of the human environment. Several species are able to cause human infections (mucormycoses) predominantly in patients with impaired immune system, diabetes, or deep trauma. In this review, we compiled 32 reports on community- and hospital-acquired outbreaks caused by Mucorales. The most common source of mucoralean outbreaks was contaminated medical devices that are responsible for 40.7% of the outbreaks followed by contaminated air (31.3%), traumatic inoculation of soil or foreign bodies (9.4%), and the contact (6.2%) or the ingestion (6.2%) of contaminated plant material. The most prevalent species were
Rhizopus arrhizus
and
R.
microsporus
causing 57% of the outbreaks. The genus
Rhizomucor
was dominating in outbreaks related to contaminated air while outbreaks of
Lichtheimia
species and
Mucor circinelloides
were transmitted by direct contact. Outbreaks with the involvement of several species are reported. Subtyping of strains revealed clonality in two outbreaks and no close relation in two other outbreaks. Based on the existing data, outbreaks of Mucorales can be caused by heterogeneous sources consisting of different strains or different species. Person-to-person transmission cannot be excluded because Mucorales can sporulate on wounds. For a better understanding and prevention of outbreaks, we need to increase our knowledge on the physiology, ecology, and population structure of outbreak causing species and more subtyping data.
Pathogenesis of Mucormycosis Ibrahim, Ashraf S.; Spellberg, Brad; Walsh, Thomas J. ...
Clinical infectious diseases,
02/2012, Letnik:
54, Številka:
suppl_1
Journal Article
Recenzirano
Odprti dostop
Mucormycosis is a life-threatening infection that occurs in patients who are immunocompromised because of diabetic ketoacidosis, neutropenia, organ transplantation, and/or increased serum levels of ...available iron. Because of the increasing prevalence of diabetes mellitus, cancer, and organ transplantation, the number of patients at risk for this deadly infection is increasing. Despite aggressive therapy, which includes disfiguring surgical debridement and frequently adjunctive toxic antifungal therapy, the overall mortality rate is high. New strategies to prevent and treat mucormycosis are urgently needed. Understanding the pathogenesis of mucormycosis and the host response to invading hyphae ultimately will provide targets for novel therapeutic interventions. In this supplement, we review the current knowledge about the virulence traits used by the most common etiologic agent of mucormycosis, Rhizopus oryzae. Because patients with elevated serum levels of available iron are uniquely susceptible to mucormycosis and these infections are highly angioinvasive, emphasis is placed on the ability of the organism to acquire iron from the host and on its interactions with endothelial cells lining blood vessels. Several promising therapeutic strategies in preciinical stages are identified.
lipase (ROL) is one of the most important enzymes used in the food, biofuel, and pharmaceutical industries. However, the highly demanding conditions of industrial processes can reduce its stability ...and activity. To seek a feasible method to improve both the catalytic activity and the thermostability of this lipase, first, the structure of ROL was divided into catalytic and noncatalytic regions by identifying critical amino acids in the crevice-like binding pocket. Second, a mutant screening library aimed at improvement of ROL catalytic performance by virtual saturation mutagenesis of residues in the catalytic region was constructed based on Rosetta's Cartesian_ddg protocol. A double mutant, E265V/S267W (with an E-to-V change at residue 265 and an S-to-W change at residue 267), with markedly improved catalytic activity toward diverse chain-length fatty acid esters was identified. Then, computational design of disulfide bonds was conducted for the noncatalytic amino acids of E265V/S267W, and two potential disulfide bonds, S61C-S115C and E190C-E238C, were identified as candidates. Experimental data validated that the variant E265V/S267W/S61C-S115C/E190C-E238C had superior stability, with an increase of 8.5°C in the melting temperature and a half-life of 31.7 min at 60°C, 4.2-fold longer than that of the wild-type enzyme. Moreover, the variant improved the lipase activity toward five 4-nitrophenyl esters by 1.5 to 3.8 times, exhibiting a potential to modify the catalytic efficiency.
Rhizopus oryzae lipase (ROL) is very attractive in biotechnology and industry as a safe and environmentally friendly biocatalyst. Functional expression of ROL in Escherichia coli facilitates effective high-throughput screening for positive variants. This work highlights a method to improve both selectivity and thermostability based on a combination of virtual saturation mutagenesis in the substrate pocket and disulfide bond prediction in the noncatalytic region. Using the method, ROL thermostability and activity to diverse 4-nitrophenyl esters could be substantially improved. The strategy of rational introduction of multiple mutations in different functional domains of the enzyme is a great prospect in the modification of biocatalysts.
Rhizopus oryzae is the primary cause of mucormycosis, an emerging, life-threatening infection characterized by rapid angioinvasive growth with an overall mortality rate that exceeds 50%. As a ...representative of the paraphyletic basal group of the fungal kingdom called "zygomycetes," R. oryzae is also used as a model to study fungal evolution. Here we report the genome sequence of R. oryzae strain 99-880, isolated from a fatal case of mucormycosis. The highly repetitive 45.3 Mb genome assembly contains abundant transposable elements (TEs), comprising approximately 20% of the genome. We predicted 13,895 protein-coding genes not overlapping TEs, many of which are paralogous gene pairs. The order and genomic arrangement of the duplicated gene pairs and their common phylogenetic origin provide evidence for an ancestral whole-genome duplication (WGD) event. The WGD resulted in the duplication of nearly all subunits of the protein complexes associated with respiratory electron transport chains, the V-ATPase, and the ubiquitin-proteasome systems. The WGD, together with recent gene duplications, resulted in the expansion of multiple gene families related to cell growth and signal transduction, as well as secreted aspartic protease and subtilase protein families, which are known fungal virulence factors. The duplication of the ergosterol biosynthetic pathway, especially the major azole target, lanosterol 14alpha-demethylase (ERG11), could contribute to the variable responses of R. oryzae to different azole drugs, including voriconazole and posaconazole. Expanded families of cell-wall synthesis enzymes, essential for fungal cell integrity but absent in mammalian hosts, reveal potential targets for novel and R. oryzae-specific diagnostic and therapeutic treatments.
To identify which solid-state typical environmental factors are involved in the induction of a solid-state special lipase (Lip1), western blot and Elisa based on Lip1 antibody were used. A low water ...activity played a significant role in the induction of Lip1, as evidenced by the increased expression level (20-46 is a subset of g/g dry cell) along with the decrease of water activity (0.927-0.969). Physical barrier against hyphal extension was found to be another required factor, since the expression of Lip1 was significantly enhanced by 3-fold using a membrane with smaller pore size (0.45 and 0.22 is a subset of m) covered on top of surface culture.
Solid‐state fermentation (SSF) at 30°C for 72 h with four generally recognized as safe (GRAS) filamentous fungi (Aspergillus oryzae NCIM 1212, Aspergillus awamori MTCC No. 548, Rhizopus oligosporus ...NCIM 1215 and Rhizopus oryzae RCK2012) showed high efficiency for the improvement of water‐soluble total phenolic content (TPC) and antioxidant properties including ABTS●⁺ 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulphonic acid) and DPPH● (2,2′‐diphenyl‐1‐picrylhydrazyl) scavenging capacities of four whole grain cereals, namely wheat, brown rice, maize and oat. A maximum 14‐fold improvement in TPC (11·61 mg gallic acid equivalent g⁻¹ grain) was observed in A. oryzae fermented wheat, while extract of R. oryzae fermented wheat (ROFW) showed maximum of 6·6‐fold and fivefold enhancement of DPPH● scavenging property (8·54 μmol Trolox equivalent g⁻¹ grain) and ABTS●⁺ scavenging activity (19·5 μmol Trolox equivalent g⁻¹ grain), respectively. The study demonstrates that SSF is an efficient method for the improvement of antioxidant potentials of cereals and R. oryzae RCK2012 fermented wheat can be a powerful source of natural antioxidants. SIGNIFICANCE AND IMPACT OF THE STUDY: Antioxidant‐rich food products are getting popularity day by day. In this study, potential of solid‐state fermentation (SSF) has been studied for the improvement of antioxidant potential of different cereals by GRAS micro‐organisms. The comparative evaluation of the antioxidant potential of various fungal fermented products derived from whole grain cereals, such as wheat, brown rice, oat and maize, has been carried out. Among these, Rhizopus oryzae RCK2012‐fermented wheat was observed as a potent source of natural antioxidants. A diet containing fermented cereals would be useful for the prevention of free radical‐mediated diseases.
Background
Due to a delay in diagnosis by conventional techniques and high mortality, the development of a standardised and rapid non‐culture‐based technique is an unmet need in pulmonary, ...gastrointestinal, and disseminated forms of mucormycosis. Though limited studies have been conducted for molecular diagnosis, there are no established serologic tests for this highly fatal infection.
Objective
To develop and evaluate an indirect in‐house enzyme‐linked immunosorbent assay (ELISA) utilising antigens of Rhizopus arrhizus for detecting anti‐Rhizopus antibodies (IgG and IgM) in sera of patients with mucormycosis.
Methods
We extracted both secretory and mycelial Rhizopus antigens using standardised protocols. Bradford assay was used for protein quantification. We then standardised an indirect ELISA using R. arrhizus mycelial and secretory antigens (10.0 μg/mL in bicarbonate buffer pH 9.2) for detecting anti‐Rhizopus IgG and IgM antibodies in patient sera. We included patients with mucormycosis, other fungal infections, and healthy controls. Antibody index value (E‐value) was calculated for each patient sample.
Results
Asparagine broth culture filtrate utilising 85% ammonium sulphate salt fractionation and mycelial homogenate grown in yeast extract peptone dextrose (YPD) broth precipitated with trichloroacetic acid (TCA) yielded a large amount of good‐quality protein for the assay. We included 55 patients with mucormycosis (rhino‐orbito‐cerebral mucormycosis ROCM, n = 39, pulmonary n = 15, gastrointestinal n = 1), 24 with other fungal infections (probable aspergillosis n = 14, candidiasis n = 10), and healthy controls (n = 16). The sensitivity of the antibody test for diagnosing mucormycosis ranged from 83.6–92.7% for IgG and 72.7–87.3% for IgM, with a specificity of 91.7–92.5% for IgG and 80–82.5% for IgM. The sera from patients with other fungal infections and healthy individuals did not show significant cross‐reactivity.
Conclusion
The detection of anti‐Rhizopus IgG antibody performed significantly better in comparison to IgM‐based ELISA for diagnosing both ROCM (sensitivity of 84.6% vs. 69.2%) and pulmonary cases (86.6% vs. 80.0%). More extensive studies are required to confirm our findings.
A number of plant pathogenic fungi belonging to the genus Rhizopus are infamous for causing rice seedling blight. This plant disease is typically initiated by an abnormal swelling of the seedling ...roots without any sign of infection by the pathogen. This characteristic symptom is in fact caused by the macrocyclic polyketide metabolite rhizoxin that has been isolated from cultures of Rhizopus sp. The phytotoxin exerts its destructive effect by binding to rice β-tubulin, which results in inhibition of mitosis and cell cycle arrest. Owing to its remarkably strong antimitotic activity in most eukaryotic cells, including various human cancer cell lines, rhizoxin has attracted considerable interest as a potential antitumour drug. Here we show that rhizoxin is not biosynthesized by the fungus itself, but by endosymbiotic, that is, intracellular living, bacteria of the genus Burkholderia. Our unexpected findings unveil a remarkably complex symbiotic-pathogenic relationship that extends the fungus-plant interaction to a third, bacterial, key-player, and opens new perspectives for pest control.
•Solid-state fermentation (SSF) of plum by-products with A. niger and R. oligosporus.•Phenolic compounds and antioxidant levels increased significantly by SSF.•Plum kernel oil yield increased by ...21.90% for SSF with A. niger.•Polar lipids were enriched with n-3 polyunsaturated fatty acids.
Evolutions of phenolic contents and antioxidant activities during solid-state fermentation (SSF) of plum pomaces (from the juice industry) and brandy distillery wastes with Aspergillus niger and Rhizopus oligosporus were investigated. The effect of fermentation time on the oil content and major lipid classes in the plum kernels was also studied. Results showed that total phenolic (TP) amounts increased by over 30% for SSF with Rhizopus oligosporus and by >21% for SSF with A. niger. The total flavonoid contents presented similar tendencies to those of the TPs. The free radical scavenging activities of methanolic extracts were also significantly enhanced. The HPLC-MS analysis showed that quercetin-3-glucoside was the major phenolic compound in both fermented plum by-products. The results also demonstrated that SSF not only helped to achieve higher lipid recovery from plum kernels, but also resulted in oils with better quality attributes (high sterol ester and n-3 PUFA-rich polar lipid contents).
A spider‐transmitted fungus (Rhizopus microsporus) that was isolated from necrotic human tissue was found to harbor endofungal bacteria (Burkholderia sp.). Metabolic profiling of the symbionts ...revealed a complex of cytotoxic agents (necroximes). Their structures were characterized as oxime‐substituted benzolactone enamides with a peptidic side chain. The potently cytotoxic necroximes are also formed in symbiosis with the fungal host and could have contributed to the necrosis. Genome sequencing and computational analyses revealed a novel modular PKS/NRPS assembly line equipped with several non‐canonical domains. Based on gene‐deletion mutants, we propose a biosynthetic model for bacterial benzolactones. We identified specific traits that serve as genetic handles to find related salicylate macrolide pathways (lobatamide, oximidine, apicularen) in various other bacterial genera. Knowledge of the biosynthetic pathway enables biosynthetic engineering and genome‐mining approaches.
Spider sense: The fungus Rhizopus microsporus, isolated from necrotic tissue resulting from a spider bite, was found to contain bacteria (Burkholderia sp.) that produce a complex of highly cytotoxic compounds (necroximes). Analysis of the PKS/NRPS hybrid assembly line and genome mining revealed the molecular basis of the biosynthesis of V‐ATPase‐inhibiting antitumor agents from diverse biological origins.
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