The effect of successive summer drought periods on bacterial diversity along a plant species richness gradient.

Drought is a major stressor to soil microbial communities, and the intensification of climate change is predicted to increase hydric stress worldwide in the coming decades. As a possible mitigating factor for the consequences of prolonged drought periods, above and belowground biodiversity can increase ecosystem resistance and resilience by improving metabolic redundancy and complementarity as biodiversity increases. Here, we investigated the interaction effect between plant richness and successive, simulated summer drought on soil microbial communities during a period of 9 years.To do that, we made use of a well-established biodiversity experiment (The Jena Experiment) to investigate the response of microbial richness and community composition to successive drought periods alongside a plant richness gradient, which covers 1-, 2-, 4-, 8-, 16- and 60-species plant communities. Plots were covered from natural precipitation by installing rain shelters 6 weeks every summer. Bulk soil samples were collected 1 year after the last summer drought was simulated. Our data indicate that bacterial richness increased after successive exposure to drought, with the increase being stable along the plant richness gradient. We identified a significant effect of plant species richness on the soil microbial community composition and determined the taxa significantly impacted by drought at each plant richness level. Our data successfully demonstrates that summer drought might have a legacy effect on soil bacterial communities.

The seeds of Plantago lanceolata comprise a stable core microbiome along a plant richness gradient.

BACKGROUND: Seed endophytic bacteria are beneficial to plants. They improve seedling growth by enhancing plant nutrient uptake, modulating stress-related phytohormone production, and targeting pests and pathogens with antibiotics. Seed endophyte composition can be influenced by pollination, plant cultivar, and soil physicochemical conditions. However, the effects of plant community richness on seed endophytes are unknown. To investigate the effects of increasing plant species richness on the diversity and composition of the seed microbiome, we made use of a well-established long-term biodiversity experiment in Germany (The Jena Experiment). We sampled seeds from different Plantago lanceolata blossoms in a plant diversity gradient ranging from monoculture to 16 species mixtures. The seeds were surface sterilized to remove seed surface-associated bacteria and subjected to a metabarcoding approach to assess bacterial community structure. RESULTS: Our data indicate a very stable core microbiome, which accounted for more than 90% of the reads and was present in all seeds independent of the plant richness level the seeds originated from. It consisted mainly of reads linked to Pseudomonas rhizosphaerae, Sphingomonas faeni and Pirellulla spp. 9% of the obtained reads were not part of the core microbiome and were only present in plots of specific diversity levels. The number of unique ASVs was positively correlated with plant richness. Interestingly, most reads described as non-core members belonged to the same genera described as the core microbiome, indicating the presence of different strains or species with possibly different functional properties important for seed performance. CONCLUSION: Our data indicate that Plantago lanceolata maintains a large seeds core microbiome across the plant richness gradient. However, the number of unique ASVs increases alongside the plant community richness, indicating that ecosystem biodiversity also mitigates diversity loss in seed endophytes.

Draft Genome Sequence of Geobacillus sp. LEMMY01, a Thermophilic Bacterium Isolated from the Site of a Burning Grass Pile.

We report here the 3,586,065-bp draft genome of Geobacillus sp. LEMMY01, which was isolated (axenic culture) from a thermophilic chemolitoautotrophic consortium obtained from the site of a burning grass pile. The genome contains biosynthetic gene clusters coding for secondary metabolites, such as terpene and lantipeptide, confirming the biotechnological potential of this strain.