Seed-associated microbiota are believed to play a crucial role in seed germination, seedling establishment, and plant growth and fitness stimulation, due to the vertical transmission of a core microbiota from seeds to the next generations. It might be hypothesized that medicinal and aromatic plants could use the seeds as vectors to vertically transfer beneficial endophytes, providing plants with metabolic pathways that could influence phytochemicals production. Here, we investigated the localization, the structure and the composition of the bacterial endophytic population that resides in Origanum heracleoticum L. seeds. Endocellular bacteria, surrounded by a wall, were localized close to the aleurone layer when using light and transmission electron microscopy. From surface-sterilized seeds, cultivable endophytes were isolated and characterized through RAPD analysis and 16S RNA gene sequencing, which revealed the existence of a high degree of biodiversity at the strain level and the predominance of the genus Pseudomonas. Most of the isolates grew in the presence of six selected antibiotics and were able to inhibit the growth of clinical and environmental strains that belong to the Burkholderia cepacia complex. The endophytes production of antimicrobial compounds could suggest their involvement in plant secondary metabolites production and might pave the way to endophytes exploitation in the pharmaceutical field.

Understanding how microbial communities survive in extreme environmental pressure is critical for interpreting ecological patterns and microbial diversity. Great Gobi A Strictly Protected Area represents an intriguing model for studying the bacterial community since it is a protected and intact wild area of the Mongolian desert. In this work, the composition of a bacterial community of the soil from four oases was characterized by extracting total DNA and sequencing through the Illumina NovaSeq platform. In addition, the soil’s chemical and physical properties were determined, and their influence on shaping the microbial communities was evaluated. The results showed a high variability of bacterial composition among oases. Moreover, combining specific chemical and physical parameters significantly shapes the bacterial community among oases. Data obtained suggested that the oases were highly variable in physiochemical parameters and bacterial communities despite the similar extreme climate conditions. Moreover, core functional microbiome were constituted by aerobic chemoheterotrophy and chemoheterotrophy, mainly contributed by the most abundant bacteria, such as Actinobacteriota, Pseudomonadota, and Firmicutes. This result supposes a metabolic flexibility for sustaining life in deserts. Furthermore, as the inhabitants of the extreme regions are likely to produce new chemical compounds, isolation of key taxa is thus encouraged.

Plant-parasitic nematodes pose a significant threat to agriculture, highlighting the need for control strategies alternative to chemical treatments. Biofumigation relies on the release of toxic glucosinolates into the soil following the incorporation of Brassicaceae plant material or derived products, such as defatted seed meals (DSM). Biofumigation has proven effective against nematodes; however, its impact on soil microbial communities remains poorly understood. In this study, we assessed the effects of biofumigation with DSM from Brassica carinata on soil microbial community and its efficacy against Meloidogyne incognita. Tomato plants were transplanted in pots with naturally infected soil amended with (i) glucosinolate-containing DSM from Brassica carinata (CAR); (ii) non-glucosinolate-containing DSM from sunflower (SUN); (iii) chemical fumigant metham-sodium (VAP); (iv) untreated control (TEST). Root growth parameters and nematode infection were evaluated at the end of the trial, while soil nematicidal effects and microbial community (prokaryotes and eukaryotes) were evaluated 0, 10, 32 and 62 days after trial setup. CAR biofumigation was as effective as VAP in reducing soil nematode population and root infection, additionally promoting root weight. The effects of CAR on prokaryotic community were transient and linked to the nutritional input from plant material, resulting in a general increase in bacterial population. In contrast, VAP induced long-lasting changes in the community and a general reduction in bacterial population. The effects on eukaryotic community, on the contrary, were comparable. Overall, these results underscore the potential of biofumigant DSM amendments as a sustainable alternative to chemical fumigants for the management of soilborne nematode diseases. Graphical Abstract