Study of exopolysaccharide produced by Streptomyces rochie strain OF1 and its effect as ameliorative on osteoarthritis in rats via inhibiting TNF-α/COX2 pathway

BACKGROUND

Carbohydrates are known as the main natural products of life activities.

RESULTS

Streptomyces rochie strain OF1 isolated from a mangrove tree produced exopolysaccharide S5 (EPSS5) (14.2 gl^-1) containing uronic acid 21.98% sulfate content of 11.65 mg/ml, and a viscosity of 1.35 mm²/s. while total hexose amine content was 24.72%. The high performance liquid chromatography (HPLC) analysis of mono sugars revealed that EPS was composed of manouronic acid, glucuronic acid, xylose, and fructose at a molar ratio of 1.0:0.5:1.0:2.0, respectively. It showed that the whole antioxidant activity was 92.06%. It showed antibacterial activity against Staphylococcus aureus, and E. coli, MRSA and Klebsiella pneumoniae. But, EPSS5 displayed low antifungal activity against Candida albicans. While no antifungal activity has been detected against Aspergillus niger. EPSS5 has antibiofilm action that is noticeable toward S. aureus with an inhibition ratio of biofilm up to 50%. Effect of EPS on serum levels of TNF-α and COX2 by 2 fold and 1.9 fold of EPS reduced serum levels of Tumor necrosis factor-α (TNF-α) by 38%, 12%, 49%, and Cyclooxygenase-2 (COX2) by 61%, 34%, and 62%, respectively. By affected of EPSS5 on arthritis in rats stimulated by carrageenan.

CONCLUSIONS

Administration of EPS ameliorated carrageen-induced elevation in inflammatory mediators; TNF-α/COX and suppressed the expressions of metalloproteinase 9 (MMP9) by 68%, 86%, and 75% correspondingly in comparison to the group of carrageenans. Then again, therapy involving a high dose only reduced MMP9 level by 57%, compared to free drug suggesting that EPSS5 is a good inhibitor of the MMP9, as it brought MMP9 back to normal levels via the signaling pathway.

Characterization of Pathway-Specific Regulator NigR for High Yield Production of Nigericin in Streptomyces malaysiensis F913

Nigericin is a polyether antibiotic with potent antibacterial, antifungal, antimalarial and anticancer activity. NigR, the only regulator in the nigericin biosynthetic gene cluster in Streptomyces malaysiensis F913, was identified as a SARP family regulator. Disruption of nigR abolished nigericin biosynthesis, while complementation of nigR restored nigericin production, suggesting that NigR is an essential positive regulator for nigericin biosynthesis. Overexpression of nigR in Streptomyces malaysiensis led to significant increase in nigericin production compared to the wild-type strain. Nigericin production in the overexpression strain was found to reach 0.56 g/L, which may be the highest nigericin titer reported to date. Transcriptional analysis suggested that nigR is required for the transcription of structural genes in the nig gene cluster; quantitative RT-PCR analysis revealed that the expression of structural genes was upregulated in the nigR overexpression strain. Our study suggested that NigR acts in a positive manner to modulate nigericin production by activating transcription of structural genes and provides an effective strategy for scaling up nigericin production.

Comparative Transcriptome-Based Mining of Genes Involved in the Export of Polyether Antibiotics for Titer Improvement

The anti-coccidiosis agent salinomycin is a polyether antibiotic produced by Streptomyces albus BK3-25 with a remarkable titer of 18 g/L at flask scale, suggesting a highly efficient export system. It is worth identifying the involved exporter genes for further titer improvement. In this study, a titer gradient was achieved by varying soybean oil concentrations in a fermentation medium, and the corresponding transcriptomes were studied. Comparative transcriptomic analysis identified eight putative transporter genes, whose transcription increased when the oil content was increased and ranked top among up-regulated genes at higher oil concentrations. All eight genes were proved to be positively involved in salinomycin export through gene deletion and trans-complementation in the mutants, and they showed constitutive expression in the early growth stage, whose overexpression in BK3-25 led to a 7.20–69.75% titer increase in salinomycin. Furthermore, the heterologous expression of SLNHY_0929 or SLNHY_1893 rendered the host Streptomyces lividans with improved resistance to salinomycin. Interestingly, SLNHY_0929 was found to be a polyether-specific transporter because the titers of monensin, lasalocid, and nigericin were also increased by 124.6%, 60.4%, and 77.5%, respectively, through its overexpression in the corresponding producing strains. In conclusion, a transcriptome-based strategy was developed to mine genes involved in salinomycin export, which may pave the way for further salinomycin titer improvement and the identification of transporter genes involved in the biosynthesis of other antibiotics.

Isolation, characterization, anti-MRSA evaluation, and in-silico multi-target anti-microbial validations of actinomycin X2 and actinomycin D produced by novel Streptomyces smyrnaeus UKAQ_23

Streptomyces smyrnaeus UKAQ_23, isolated from the mangrove-sediment, collected from Jubail,Saudi Arabia, exhibited substantial antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA), including non-MRSA Gram-positive test bacteria. The novel isolate, under laboratory-scale conditions, produced the highest yield (561.3 ± 0.3 mg/kg fermented agar) of antimicrobial compounds in modified ISP-4 agar at pH 6.5, temperature 35 °C, inoculum 5% v/w, agar 1.5% w/v, and an incubation period of 7 days. The two major compounds, K₁ and K₂, were isolated from fermented medium and identified as Actinomycin X₂ and Actinomycin D, respectively, based on their structural analysis. The antimicrobial screening showed that Actinomycin X₂ had the highest antimicrobial activity compared to Actinomycin D, and the actinomycins-mixture (X₂:D, 1:1, w/w) against MRSA and non-MRSA Gram-positive test bacteria, at 5 µg/disc concentrations. The MIC of Actinomycin X₂ ranged from 1.56–12.5 µg/ml for non-MRSA and 3.125–12.5 µg/ml for MRSA test bacteria. An in-silico molecular docking demonstrated isoleucyl tRNA synthetase as the most-favored antimicrobial protein target for both actinomycins, X₂ and D, while the penicillin-binding protein-1a, was the least-favorable target-protein. In conclusion, Streptomyces smyrnaeus UKAQ_23 emerged as a promising source of Actinomycin X₂ with the potential to be scaled up for industrial production, which could benefit the pharmaceutical industry.

Enhancement of undecylprodigiosin production from marine endophytic recombinant strain Streptomyces sp. ALAA-R20 through low-cost induction strategy

Genetic manipulation of the undecylprodigiosin-producing strains and engineered culture medium approaches were applied as the most economical induction strategy for improving production. The hyper-producing recombinant strain ALAA-R20 was obtained after applying protoplast fusion strategy between the potent producer marine endophytic strains Streptomyces sp. ESRAA-10 (P1) and Streptomyces sp. ESRAA-31 (P2) of Dendronephthya hemprichi. Recombinant strain ALAA-R20 produced undecylprodigiosin yield higher than its parental strains ESRAA-10 and ESRAA-31 by 82.45% and 105.52% under submerged fermentation using modified R2YE medium. In order to reduce the costs of producing undecylprodigiosin, a solid-state fermentation (SSF) was applied. Scaled-up of optimized SSF parameters consisting of groundnut oil cake (GOC) sized to 3 mm, initial moisture content 80% with a mixture of dairy mill and fruit processing wastewaters (1:1), pH 7.0, inoculum size equal to 3 × 10⁵ spores/g dry substrate (gds), incubation temperature 30 °C, and 7-day incubation period yielded the highest yield of 181.78 mg/gds of undecylprodigiosin by the recombinant strain Streptomyces sp. ALAA-R20. Extraction and purification of the pigment using the chromatographic techniques as well as mass spectral analysis exhibited maximum absorbance at 539 nm which is physiological property of the undecylprodigiosin. Undecylprodigiosin was stable over a wide temperature ranged from - 20 to 35 °C even after storage for 6 months. The maximum yield and stability of pigment was obtained at the acidic pH (acidified methanol, pH 4.0). Undecylprodigiosin obtained from the recombinant strain Streptomyces sp. ALAA-R20 demonstrated strong antimicrobial activity against all multidrug-resistant bacterial and fungal strains tested with minimum inhibitory, minimum bactericidal, and minimum fungicidal concentrations ranged between 0.5 and 4.0, 0.5 to 4.0, and 1.0 to 8.0 μg/mL, respectively. It also showed complete inhibition of cancer cells; HCT-116, HepG-2, MCF-7 and A-549 at 5, 8, 4, and 7 μM with IC₅₀ equal to 2.0, 4.7, 1.2, and 2.8 μM, respectively.

Approach to nigericin derivatives and their therapeutic potential

A new nigericin analogue that has been chemically modified was synthesized through a fluorination process from the parent nigericin, produced from a novel Streptomyces strain DASNCL-29. Fermentation strategies were designed for the optimised production of nigericin molecule and subjected for purification and structural analysis. The fermentation process resulted in the highest yield of nigericin (33% (w/w)). Initially, nigericin produced from the strain DASNCL-29 demonstrated polymorphism in its crystal structure, i.e., monoclinic and orthorhombic crystal lattices when crystallised with methanol and hexane, respectively. Furthermore, nigericin produced has been subjected to chemical modification by fluorination to enhance its efficacy. Two fluorinated analogues revealed that they possess a very potent antibacterial activity against Gram positive and Gram negative bacteria. To date, the nigericin molecule has not been reported for any reaction against Gram-negative bacteria, which are increasingly becoming resistant to antibiotics. For the first time, fluorinated analogues of nigericin have shown promising activity. In vitro cytotoxicity analysis of fluorinated analogues demonstrated tenfold lesser toxicity than the parent nigericin. This is the first type of study where the fluorinated analogues of nigericin showed very encouraging activity against Gram-negative organisms; moreover, they can be used as a candidate for treating many serious infections.

Actinobacteria Derived from Algerian Ecosystems as a Prominent Source of Antimicrobial Molecules

Actinobacteria, in particular "rare actinobacteria" isolated from extreme ecosystems, remain the most inexhaustible source of novel antimicrobials, offering a chance to discover new bioactive metabolites. This is the first overview on actinobacteria isolated in Algeria since 2002 to date with the aim to present their potential in producing bioactive secondary metabolites. Twenty-nine new species and one novel genus have been isolated, mainly from the Saharan soil and palm groves, where 37.93% of the most abundant genera belong to Saccharothrix and Actinopolyspora. Several of these strains were found to produce antibiotics and antifungal metabolites, including 17 new molecules among the 50 structures reported, and some of these antibacterial metabolites have shown interesting antitumor activities. A series of approaches used to enhance the production of bioactive compounds is also presented as the manipulation of culture media by both classical methods and modeling designs through statistical strategies and the associations with diverse organisms and strains. Focusing on the Algerian natural sources of antimicrobial metabolites, this work is a representative example of the potential of a closely combined study on biology and chemistry of natural products.