Rhizoremediation of hydrocarbon contaminated soil using Luffa aegyptiaca (Mill) and associated fungi

Revealing culturable fungal microbiome communities from the Arabian Peninsula desert representing a unique source of biochemicals for drug discovery and biotechnology

Background

Microbes living at extremes evolve unique survival strategies to adapt to challenging environmental conditions. Among these strategies is their distinctive metabolic potential and ability to produce specialized metabolites enabling them to compete for limited resources and defend against predators. These metabolites have significant potential in pharmaceutical and industrial applications, particularly in the development of drugs and biochemicals.

Objectives

This study aimed to investigate the culturable fungal communities associated with four desert plants and their surrounding soils in the Arabian Peninsula desert to identify their bioactive properties.

Methods

A total of 12 distinct fungal species were isolated from the plants and soils. Each plant hosted a unique set of fungi, demonstrating the diversity of desert-adapted fungal communities. Biological activities of the fungal extracts were evaluated through various assays, including antimicrobial, antifungal, anticancer, and antioxidant properties.

Results

Panicum turgidum harbors the most diverse fungal community, dominated by genera such as Mucor, Aspergillus, Colletotrichum, Alternaria, and Chaetomium. Aspergillus species comprise 33% of the total isolates, followed by Fusarium at 16%. All extracts exhibit diverse activities, with Aspergillus species demonstrating the highest antioxidant activities and total phenolic and flavonoid content. Fungi from P. turgidum, particularly Mucor sp., Aspergillus sp., and Curvularia sp., display potent activity against Staphylococcus aureus, while Mucor sp., Chaetomium sp., and Curvularia sp. exhibit moderate inhibition against Pseudomonas aeruginosa.

Conclusion

This study highlights the importance of exploring extremophilic microorganisms, such as those found in desert ecosystems, as they offer a wealth of compounds that could address current challenges in drug discovery and biotechnology.

Bacteria associated with Zn-hyperaccumulators Arabidopsis halleri and Arabidopsis arenosa from Zn-Pb-Cd waste heaps in Poland as promising tools for bioremediation

To identify metal adapted bacteria equipped with traits positively influencing the growth of two hyperaccumulator plant species Arabidopsis arenosa and Arabidopsis halleri, we isolated bacteria inhabiting rhizosphere and vegetative tissues (roots, basal and stem leaves) of plants growing on two old Zn-Pb-Cd waste heaps in Bolesław and Bukowno (S. Poland), and characterized their potential plant growth promoting (PGP) traits as well as determined metal concentrations in rhizosphere and plant tissues. To determine taxonomic position of 144 bacterial isolates, 16S rDNA Sanger sequencing was used. A metabolic characterization of isolated strains was performed in vitro using PGP tests. A. arenosa and A. halleri accumulate high amounts of Zn in their tissues, especially in stem leaves. Among in total 22 identified bacterial taxa, the highest level of the taxonomical diversity (H' = 2.01) was revealed in A. halleri basal leaf endophytes originating from Bukowno waste heap area. The 96, 98, 99, and 98% of investigated strains showed tolerant to Cd, Zn, Pb and Cu, respectively. Generally, higher percentages of bacteria could synthesize auxins, siderophores, and acetoin as well as could solubilize phosphate. Nine of waste heap origin bacterial strains were tolerant to toxic metals, showed in vitro PGP traits and are potential candidates for bioremediation.

The combined rhizoremediation by a triad: plant-microorganism-functional materials

The article describes new strategies for the remediation of soils contaminated with organic and inorganic pollutants. The aim of this study is to investigate the synergistic effects of combining plant-microorganism-functional materials for a more effective reduction of soil contamination with toxic chemicals. The innovative triad involves functional materials as a habitat for microorganisms, which helps to control the release of pollutants into the soil solution from the adsorbed form. This, in turn, reduces the toxic effect on microorganisms and plants. Microorganisms play a complex role, consisting of partial biodegradation of pollutants, stimulation of plant growth, and support for nutrient supply. Plants synthesize root exudates that facilitate microorganisms in biodegrading organic pollutants and stimulate their growth. The plant takes up pollutants through the root system, which can be further supported by endophytic microorganisms. The cooperation of the three players produces a synergistic effect that enhances the effectiveness of rhizodegradation supported by functional materials, which is more effective than using microorganisms, phytoremediation, or functional materials alone. The combination of physicochemical methods (functional materials) and microbiological methods (bacteria and fungi, rhizosphere, symbiotic and non-symbiotic) supported by plants (hyperaccumulators) is a promising approach for reducing chemicals from soil. Key examples of the synergistic effects of combining plant-microorganism-functional materials have been provided in this article.

Abundant fungi dominate the complexity of microbial networks in soil of contaminated site: High-precision community analysis by full-length sequencing

During the past decade, the characterization of microbial community in soil of contaminated sites was primarily done by high-throughput short-read amplicon sequencing. However, due to the similarity of 16S rRNA and ITS genes amplicon sequences, the short-read approach often limits the microbial composition analysis at the species level. Here, we simultaneously performed full-length and short-read amplicon sequencing to clarify the community composition and ecological status of different microbial taxa in contaminated soil from a high-resolution perspective. We found that (1) full-length 16S rRNA gene sequencing gave better resolution for bacterial identification at all levels, while there were no significant differences between the two sequencing platforms for fungal identification in some samples. (2) Abundant taxa were vital for microbial co-occurrences network constructed by both full-length and short-read sequencing data, and abundant fungal species such as Mortierella alpine, Fusarium solani, Mrakia frigida, and Chaetomium homopilatum served as the keystone species. (3) Heavy metal correlated with the microbial community significantly, and bacterial community and its abundant taxa were assembled by deterministic process, while the other taxa were dominated by stochastic process. These findings contribute to the understanding of the ecological mechanisms and microbial interactions in site soil ecosystems and demonstrate that full-length sequencing has the potential to provide more details of microbial community.

Bioactive compounds of Curvularia species as a source of various biological activities and biotechnological applications

Many filamentous fungi are known to produce several secondary metabolites or bioactive compounds during their growth and reproduction with sort of various biological activities. Genus Curvularia (Pleosporaceae) is a dematiaceous filamentous fungus that exhibits a facultative pathogenic and endophytic lifestyle. It contains ~213 species among which Curvularia lunata, C. geniculata, C. clavata, C. pallescens, and C. andropogonis are well-known. Among them, C. lunata is a major pathogenic species of various economical important crops especially cereals of tropical regions while other species like C. geniculata is of endophytic nature with numerous bioactive compounds. Curvularia species contain several diverse groups of secondary metabolites including alkaloids, terpenes, polyketides, and quinones. Which possess various biological activities including anti-cancer, anti-inflammatory, anti-microbial, anti-oxidant, and phytotoxicity. Several genes and gene factors are involved to carry and regulate the expression of these activities which are influenced by environmental signals. Some species of Curvularia also show negative impacts on humans and animals. Apart from their negative effects, there are some beneficial implications like production of enzymes of industrial value, bioherbicides, and source of nanoparticles is reported. Many researchers are working on these aspects all over the world but there is no review in literature which provides significant understanding about these all aspects. Thus, this review will provide significant information about secondary metabolic diversity, their biological activities and biotechnological implications of Curvularia species.

Tendril Anatomy: A Tool for Correct Identification among Cucurbitaceous Taxa

This research examined the histological micro-structure of tendril vasculature in cucurbitaceous taxa. In this research, the tendril anatomy of 17 taxa of Cucurbitaceae categorized into seven genera, including Cucumis (five species), Cucurbita and Luffa (three species each), Citrullus and Momordica (two species each) while Lagenaria and Praecitrullus (one species each), collected from different areas of the Thal desert were examined via microscopic imaging to explore its taxonomic significance. Tendril transverse sections were cut with a Shandon Microtome to prepare slides. The distinctive characteristics of taxonomic value (qualitative and quantitative) include tendril and vascular bundle shape, variation in the number of vascular bundles, tendril diameter length, layers of sclerenchyma, and shape of collenchyma and epidermal cells. Tendril shapes observed are irregular, slightly oval-shaped, slightly C shaped, angular (4-angled, 6-angled, or polygonal), and star shaped. Quantitative measurements were taken to analyze the data statistically using SPSS software. Cucurbita pepo had a maximum tendril diameter length of 656.1 µm and a minimum in Momordica balsamina of 123.05 µm. The highest number of vascular bundles (12) were noticed in Luffa acutangula var.amara. Angular type was prominent in collenchyma, and irregular shape was dominant in sclerenchyma cells. A maximum of seven to nine sclerenchyma layers were present in Lagenaria siceraria and a minimum of two or three layers in Cucumis melo subsp. agrestis, Cucumis melo var. flexuosus, and Cucumis melo var.cantalupensis. Epidermis cells also show great variations with a rectangular shape being dominant. Statistical UPGMA dendrogram clustering of tendril vasculature traits shows that histological sections studied with microscopic techniques can be used to identify species and will play a vital role in future taxonomic and phylogenic linkages.