Variation of antibacterial and antioxidant secondary metabolites and volatiles in leaf and callus extracts of Phulai (Acacia Modesta Wall.).

BACKGROUND: Acacia species are economically significant as medicinal plants that have been utilized since ancient times. Acacia modesta has been reported to possess potent antibacterial and antioxidant properties, but its growth rate is slow. In this study, we hypothesized that inducing callus in vitro from A. modesta could enhance the production of antibacterial and antioxidant secondary metabolites, thereby circumventing the issues of slow growth and excessive harvesting of the plant. RESULTS: The callus was induced from axillary buds on MS medium supplemented with 1 mg/L of 2,4-D and 1 mg/L of BAP. The secondary metabolites, volatile compounds, antibacterial activity, and antioxidant activity of the callus and parent plant leaf extracts were evaluated. The results revealed that the content of phenolics and flavonoids, the number of volatile compounds, and the antibacterial and antioxidant activities of the callus extract were significantly enhanced (P ≤ 0.05) compared to the leaf extract. The antibacterial and antioxidant effects were strongly correlated with the total phenolic and flavonoid content in the extracts. CONCLUSIONS: Our findings suggest that in vitro callus culture increases the production of phenolics, flavonoids, and volatile compounds. This subsequently enhances the antibacterial and antioxidant properties of A. modesta.

Production of bioactive ß-carotene by the endophytic bacterium Citricoccus parietis AUCs with multiple in vitro biological potentials.

BACKGROUND: Although microalgae and plants are traditionally used for obtaining natural pigments, overexploitation and overharvesting threaten them. Bacteria represent a superior alternative for the production of pigments due to their ability to produce greater amounts in a short time without seasonal restrictions; furthermore, bacterial pigments have a wide range of uses and are safe and biodegradable. This study is the first on the production of ß-carotene as a promising bioactive agent from endophytic bacteria. RESULTS: The yellow pigment produced by the endophytic bacterium Citricoccus parietis AUCs (NCBI accession number: OQ448507.1) was extracted by methanol and then purified and identified. One band was obtained by TLC analysis, which was identified as ß-carotene based on its spectroscopic and chromatographic characteristics. The pigment exhibited remarkable antibacterial, antioxidant and antidiabetic activities. CONCLUSIONS: This research may serve as a valuable starting point for exploiting C. parietis AUCs as a potent source of ß-carotene for biomedical therapies. To validate the findings of this research, in vivo studies must be performed.

Phytotoxic Interference of Culture Filtrates of Endophytic Bacteria Associated with Nerium oleander Leaf Against Seed Germination of the Invasive Noxious Weed Cenchrus echinatus.

Weeds cause destructive agricultural losses, so weed control is an urgent challenge facing agriculture. The extensive use of synthetic chemical herbicides has detrimental environmental impacts and promotes the emergence of resistant species. Therefore, in this study we tried to find a new natural weed control that can ensure biosafety and eco-sustainability. The phytotoxic potential of culture filtrates of the endophytes Bacillus inaquosorum NL1 and Bacillus safensis NL2 isolated from Nerium oleander leaf against the invasive harmful weed species Cenchrus echinatus was evaluated. Culture filtrates of both bacterial species exhibited potent phytotoxic activity, which resulted in 100% germination inhibition of C. echinatus. The chemical analysis of culture filtrates revealed high contents of total phenolics and n-alkanes that have phytotoxic effects against seed germination. According to the findings of this study the endophytic bacteria associated with N. oleander leaf can be used in the future to develop a sustainable bio-herbicide formulation.

Drought-tolerant Sphingobacterium changzhouense Alv associated with Aloe vera mediates drought tolerance in maize (Zea mays).

Drought severity and duration are expected to increase as a result of ongoing global climate change. Therefore, finding solutions to help plants to deal with drought stress and to improve growth in the face of limited water resources is critical. In this study, a drought tolerant- plant growth promoting endophytic bacterium was isolated from Aloe vera roots. It was identified as Sphingobacterium changzhouense based on 16S rRNA gene sequencing and was deposited into NCBI database with accession number (ON944028). The effect of S. changzhouense inoculation on maize growth under drought stress was investigated. The results revealed that inoculation significantly (p ≤ 0.05) enhanced root and shoot elongation by 205 and 176.19% respectively. Photosynthesis rate, stomatal conductance and water use efficiency were improved in inoculated plants. interestingly, inoculation resulted in significant increase in total chlorophyll, total carbohydrates, proline, total proteins, total phenolics and total flavonoids by 64, 31.5, 25.1, 75.07, 83.7 and 65.4% respectively. Total antioxidant capacity of inoculated plants (51.2 mg/g FW) was higher than that of non-inoculated plants (11.87 mg/g FW), which was found to be positively correlated to the levels of phenolics and flavonoids. Our finding suggests that S. changzhouense could be used to improve crop growth and assist plants to resist drought stress in arid agricultural lands.

Macroalga-associated bacterial endophyte bioactive secondary metabolites twinning: Cystoseira myrica and its associated Catenococcus thiocycli QCm as a model.

Marine ecosystems represent the largest biome on the earth. Until now, the relationships between the marine microbial inhabitants and the macroalgal species unclear, and the previous studies are insufficient. So, more research is required to advance our understanding of macroalgal- microbial interactions. In this study, we tried to investigate the relationship between the brown marine macroalga, Cystoseira myrica and its associated bacterial endophyte, Catenococcus thiocycli, as the first study concerning the production of bioactive secondary metabolites from a macroalgal species comparing with its associated endophytic bacteria. Secondary metabolites were extracted from alga and its bacterial endophyte with ethyl acetate and methanol. All extracts contained significant quantities of phenolics, flavonoids, tannins, and saponins. Strikingly, extracts possess antioxidant, anti-inflammatory and antimicrobial activities which were significantly correlated to phenolic and flavonoid contents.

The endophyte Stenotrophomonas maltophilia EPS modulates endogenous antioxidant defense in safflower (Carthamus tinctorius L.) under cadmium stress.

Cadmium (Cd) pollution in agricultural soils induces oxidative stress in plants that in turn is the foremost limiting factor for agricultural productivity. In past few decades, plant-metal-microbe interaction is of great interest as an emerging environmentally friendly technology that can be exploited to alleviate metal stress in plants. Considering these, in the present study an endophytic bacterium strain EPS has been isolated from the roots of common bean. The present strain was identified as Stenotrophomonas maltophilia based on 16S rRNA gene sequence. The strain showed Cd tolerance and Cd-adsorption potentials. The inoculation of strain EPS in safflower seeds significantly enhanced the antioxidant defense of plants under Cd-stress conditions through increasing the levels of antioxidant molecules like phenolics, flavonoids and carotenoids as well as improving the activities of the antioxidative enzymes including guaiacol peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD). The output of this study is that strain EPS inoculation mitigates Cd-induced oxidative stress and consequently it may be beneficial, especially in Cd-contaminated crop fields.

Antibacterial and cytotoxic potency of thermophilic Streptomyces werraensis MI-S.24-3 isolated from an Egyptian extreme environment.

The need for novel and active antibiotics specially from actinomycetes is essential due to new and drug-resistant pathogens. In this study, 87 actinomycetes were isolated, and 18 strains among them characterized as thermophilic actinomycetes. Further fractionation and preliminary antibacterial activities indicated that one strain, coded as MI-S.24-3, showed good antibacterial activity. Based on the phenotypic, genomic, phylogenetic, and biochemical analyses, MI-S.24-3 was identified as Streptomyces werraensis. Results demonstrated that the ethyl acetate active fraction showed maximum antibacterial activity against Staphylococcus aureus and Escherichia coli with MIC (12.7 ± 0.1 and 18.3 ± 0.2 mg/mL), and MBC (96.5 ± 1.4 and 91.5 ± 0.7 mg/mL), respectively, with determination of time kill kinetics assay. The active fraction showed moderate-to-weak cytotoxic effects against human lung carcinoma (A549 cells), breast cancer cell line (MCF-7), and human cervical carcinoma (HELA cells) with a IC50 of (23.8 ± 1.2, 54 ± 1.8, 96.4 ± 3.2 µg/mL, respectively). Active components were characterised by different chemically volatile, ester, and lactone compounds, determined by GC-MS coupled with daughter ions of (GC-MS/MS). Notably, erucic acid and reynosin identified compounds are rare metabolites produced by Streptomyces werraensis. Our findings demonstrated that the MI-S.24-3 strain could be a potential source for active compounds of biomedical and pharmaceutical interest.