An endophytic fungus isolated from Vernonia amygdalina, a medicinal plant from Sudan, was taxonomically characterized as Curvularia papendorfii. Ethyl acetate crude extract of C. papendorfii revealed an important antiviral effect against two viral pathogens, the human coronavirus HCoV 229E and a norovirus surrogate, the feline coronavirus FCV F9. For the last one, 40% of the reduction of the virus-induced cytopathogenic effect at lower multiplicity of infection (MOI) 0.0001 was observed. Selective antibacterial activity was obtained against Staphylococcus sp. (312 µg/mL), and interesting antiproliferative activity with half maximal inhibitory concentration (IC₅₀) value of 21.5 ± 5.9 µg/mL was observed against human breast carcinoma MCF7 cell line. Therefore, C. papendorfii crude extract was further investigated and fractionated. Twenty-two metabolites were identified by gas chromatography coupled to mass spectrometry (GC–MS), and two pure compounds, mannitol and a new polyhydroxyacid, called kheiric acid, were characterized. A combination of spectroscopic methods was used to elucidate the structure of the new aliphatic carboxylic acid: kheiric acid (3,7,11,15-tetrahydroxy-18-hydroxymethyl-14,16,20,22,24-pentamethyl-hexacosa-4E,8E,12E,16,18-pentaenoic acid). Kheiric acid showed an interesting result with a minimum inhibitory concentration (MIC) value of 62.5 µg/mL against meticillin-resistant Staphylococcus aureus (MRSA). Hence, endophytes associated with medicinal plants from Sudan merit more attention, as they could be a treasure of new bioactive compounds.

The exploration of certain microbial resources such as beneficial endophytic microorganisms is considered a promising strategy for the discovery of new antimicrobial compounds for the pharmaceutical industries and agriculture. Thirty-one endophytic bacterial strains affiliated with Bacillus, Janthinobacterium, Yokenella, Enterobacter, Pseudomonas, Serratia, and Microbacterium were previously isolated from vetiver (Chrysopogon zizanioides (L.) Roberty) roots. These endophytes showed antifungal activity against Fusarium graminearum and could be a source of antimicrobial metabolites. In this study, in particular, using high-throughput screening, we analyzed their antagonistic activities and those of their cell-free culture supernatants against three species of Fusarium plant pathogens, a bacterial strain of Escherichia coli, and a yeast strain of Saccharomyces cerevisiae, as well as their capacity to produce lipopeptides. The results showed that the culture supernatants of four strains close to B. subtilis species exhibited antimicrobial activities against Fusarium species and E. coli. Using mass spectrometry analyses, we identified two groups of lipopeptides (surfactins and plipastatins) in their culture supernatants. Whole-genome sequencing confirmed that these bacteria possess NRPS gene clusters for surfactin and plipastatin. In vitro tests confirmed the inhibitory effect of plipastatin alone or in combination with surfactin against the three Fusarium species.

Leucojum aestivum is a medicinal plant belonging to the Amaryllidaceae family well known as a producer of alkaloids such as galanthamine and lycorine. However, the endophytic microbes that colonize different plant tissues without causing any damage have not been reported in this plant. Here, we explored the different endophytic bacterial communities isolated from different surface disinfected tissues of L. aestivum ‘Gravety giant’ and screened bacterial isolates producing alkaloids and their potential use as biocontrol agent against wheat pathogens. For that purpose, endophytic bacteria were isolated from bulbs, roots and shoots of L. aestivum. After taxonomical characterization, these microorganisms were screened for their ability to produce alkaloids using high-performance thin-layer chromatography (HPTLC) and untargeted liquid chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) strategies. We isolated 138 bacteria belonging to four phyla and 42 genera, mainly from roots and shoots. The most abundant genera were Rahnella in shoot, Patulibacter in bulb and Bacillus in roots. Among the different bacterial isolates, the methanolic extracts of Luteibacter rhizovicinus (LaBFB3301) and Commamonas denitrificans (LaBFS2103) slightly delayed the growth of F. graminearum colonies in in vitro dual tests against F. graminearum and M. nivale strains with 15.5% and 19.9% inhibition rates, respectively. These isolates are able to produce an indolic alkaloid tryptophol (C₁₀H₁₁NO, [M + H]⁺ 162.0913). These endophytic bacteria might be investigated to characterize the plant protection effect and the plant growth promotion effect.

Proteases, catalysing protein hydrolysis, and arylsulfatases, catalysing sulfate-ester hydrolysis, are key microbial enzymes for N and S mineralization in soil. However, knowledge gaps remain regarding the effect of crop successions and seasonal and interannual meteorological variations on microbial communities responsible for those activities. Here, we compared the effect of six cropping sequences on the abundance and activity of microbial communities involved in proteolysis and sulfate-ester hydrolysis in northern France over four years, with two sampling dates per year. Crop sequences impacted soil microbial communities involved in proteolysis but not those involved in sulfate-ester hydrolysis. Oilseed rape following wheat presented a higher abundance of fungal 18S rDNA, culturable bacteria and alkaline metalloprotease genes and higher protease activity than other crop sequences (wheat following oilseed rape or pea, barley following wheat and pea following barley). Net N and S mineralization was not impacted by the cropping sequence. However, interannual variability of microbial parameters was large, and largely overcame the effect of crop sequences. Precipitation variability between years was the likely cause of this effect. In conclusion, the interaction between current crop, previous crops and yearly meteorology can strongly impact the soil microbial communities in agroecosystems.

The present study aims to assess the respective efficiency of Biochars (BCs) and activated carbons (ACs) to limit PCB 101, 138, 153 and 180 transfer to plants. A set of 6 high carbon materials comprising 3 BCs and 3 ACs was tested and used to amend a soil at 2% rate. Then, the two most efficient carbonaceous materials were used as an amendment of an historically contaminated soil sampled in the St Cyprien vicinity (Loire, France). An environmental availability assessment was performed using the ISO/DIS 16751 Part A assay (n = 3). For the in vivo part, Cucurbita pepo were grown for 12 weeks. Significant decreases of transfer were found for both assays notably for powdered ACs (up to 98%). By contrast, significantly lower levels of transfer reduction were observed when BCs amendments were performed, ranging from 27 to 80% for environmental availability assessment and 0 to 36% for C. pepo. Reduction factors above 90% for the 2 selected materials were found from amended historically contaminated soils. Present results led to consider such a sequestering strategy as valuable to ensure plant production on non-dioxin-like polychlorobiphenyls (NDL-PCBs) contaminated soils.