Biology subjects

Rastrojo, A.

Publications and source records attributed to Rastrojo, A..

7 recordsLinked to original sources

bioRxiv2026

Drift-driven microbiome simplification generates reconstructable and ecologically cohesive microbial communities

Engineering simplified microbial communities that retain function and ecological cohesiveness remains a major challenge because the taxa and interactions required for community establishment are rarely known a priori. Here, we experimentally evaluated drift-driven microbiome simplification as an alternative strategy for generating reduced and reconstructable microbial consortia. Using the tomato rhizosphere as a model system, three source microbial communities were subjected to different dilution bottlenecks and serial propagation. Increasing dilution was the main determinant of community composition and simplification, while repeated passage produced additional reductions in ASV richness, phylogenetic diversity, and evenness. Importantly, diversity loss was not accompanied by a uniform deterioration in bacterial colonization or plant performance, indicating that substantial simplification can occur without a parallel collapse in these system-level properties. Candidate Minimal Microbiome prototypes were selected from endpoint communities, reconstructed as synthetic communities, and their ecological cohesiveness was evaluated through invasion experiments. The reconstructed communities strongly restricted the establishment of the original complex microbial fractions, although invasion success depended markedly on invader identity. The drift-derived communities were at least as resistant to invasion as an independently designed bottom-up synthetic community. Together, these results provide experimental support for drift-driven simplification as a strategy to generate reduced microbial communities whose dominant members can be isolated, reconstructed, and experimentally evaluated. By allowing ecological assembly to generate candidate community configurations before cultivation and reconstruction, this approach provides a complementary route to rational bottom-up design and function-directed top-down microbiome engineering.

microbiology↗

bioRxiv2026

Combinatorial community coalescence in early tomato assembly reveals a rhizosphere attractor in composition and abundance architecture

The rhizosphere microbiome plays fundamental roles in plant health and productivity, yet the ecological rules governing microbiome assembly remain poorly understood. Here, we investigated early rhizosphere community assembly in tomato using a replicated combinatorial community coalescence framework, in which seven distinct natural bacterial communities were inoculated individually and in all possible pairwise and triplet combinations. Single-inoculum communities clustered according to inoculum identity, indicating a strong effect of source community composition on assembly trajectories. However, when all communities were analyzed jointly, samples formed a continuous compositional landscape with no clear evidence of discrete community states. Despite major differences in source community composition, rhizosphere communities consistently converged toward a highly similar uneven rank-abundance structure, with two ASVs accounting for 50% and a median of nineteen ASVs for 90% of total abundance. While assembly was dominated by a very small number of Pseudomonas ASVs, limited evidence of alternative dominant states was observed. Increasing inoculum complexity did not increase stochasticity but instead promoted stronger convergence toward a global rhizosphere compositional centroid. Moreover, dominance hierarchies emerging from community coalescence closely mirrored the distance of source communities to this centroid. The two most dominant communities originated from orchard soils, suggesting that historical contingency and prior adaptation to horticultural crop rhizospheres may influence competitive success. Together, these results are consistent with the existence of a canonical rhizosphere attractor in composition and abundance architecture, with patterns consistent with assembly occurring under a limited number of dominant ecological niches imposed by the tomato rhizosphere.

microbiology↗

bioRxiv2026

Early rhizosphere assembly during the onset of photosynthesis reveals inoculum-constrained succession with increased phylogenetic clustering, filtering and diversity

The rhizosphere microbiome, one of the most diverse and metabolically active microbial ecosystems known, plays fundamental roles in plant health and productivity. However, the ecological dynamics occurring during the transition between germination and the establishment of the first true leaves, a developmental window associated with the onset of active photosynthesis and rapid root expansion, remain poorly understood. Here, we investigated rhizosphere microbiome assembly during the first four weeks of tomato development by sampling communities arising from seven distinct natural soil inocula twice weekly to obtain fine-scale temporal resolution. Bacterial load, richness, evenness and phylogenetic diversity all increased significantly during plant development, indicating progressive increases in rhizosphere ecosystem complexity. In addition, diverse initial microbial communities differentially influenced both host plant development and the bacterial carrying capacity of the resulting rhizosphere ecosystem. Although temporal effects on rhizosphere microbiome composition were significant, assembly trajectories remained strongly constrained by the initial inoculum. Temporal analysis nevertheless revealed significant taxonomic turnover despite limited global compositional restructuring. In particular, Proteobacteria and Pseudomonadaceae decreased over time, whereas Actinobacteria, Acidobacteria and Streptomycetaceae increased. However, communities did not become progressively more similar or divergent over time. Altogether, our results indicate that early rhizosphere microbiome assembly involves rapid ecological succession within inoculum-constrained compositional trajectories, with early copiotrophic Proteobacteria progressively giving rise to more diverse and phylogenetically structured communities. These findings suggest that the first weeks of plant development may represent a critical ecological window for microbiome-based manipulation strategies in agriculture.

microbiology↗

bioRxiv2025

Modular automated high-throughput isolation and phylogenetic identification of bacteria from complex microbiomes

Metagenomic analysis can generate hypotheses about microbiome interactions and function, yet mechanistic understanding is only possible through precise experimentation manipulating its microbiota composition. The high-throughput isolation of microbiome members thus represents a core resource in this field of research. Here, we present and test a culturomics pipeline based on the use of the limiting dilution method with multi-well plates, an optical plate reader, and barcoded sequencing for phylogenetic identification, and offer modularity by proposing different protocols and possibilities along the pipeline. Most importantly, we provide all scripts required for process automation using an affordable pipetting robot, along with associated estimates of financial and labor costs.

microbiology↗

bioRxiv2024

Coupled phylogenetic and functional enrichment in the tomato rhizosphere microbiome

Plant-microbe interactions occur mainly in the rhizosphere, a hot spot of microbial activity and diversity. Given that the outcome of such interactions can significantly impact plant productivity, we require a better understanding of the rhizosphere microbiome if knowledge-based microbiome modification strategies are to be successfully deployed in the future. Here, we aimed to gain a better understanding of the assembly process of the tomato rhizosphere microbiome and its potential composition-function relationships. Among other things, we studied community assembly through the lens of a conceptual framework for the phylogenetically constrained assembly of microbial communities, while assessing community function based on the predicted minimal metagenome of the microbial ecosystem. We observed a systematic enrichment in terms of phylogeny and predicted functional content in the rhizosphere and were able to delimit phylogenetic signal in the ecosystem with 12 functionally coherent phylogenetic groups present in all samples which together accounted for a large fraction of the total community. Our analyses indicated that these groups included a significantly larger content of the ecosystems minimal metagenome than expected by chance. Thus, our study suggests that community assembly followed coupled phylo-functional selection independent of host genetics, and we expect the same phenomenon to occur in other rhizosphere microbiomes. This knowledge provides a thrust in our understanding of how community composition-phylogeny-function relationships drive the assembly process of the rhizosphere microbiome and should help guide the design of synthetic rhizosphere microbiomes for both research and commercial purposes.

microbiology↗

bioRxiv2022

High-throughput engineering of cytoplasmic- and nuclear-replicating large dsDNA viruses by CRISPR/Cas9

The application of CRISPR/Cas9 to improve genome engineering efficiency of large dsDNA viruses has been extensively described, but a robust and versatile method for high-throughput generation of marker-free recombinants for a desire locus has not been reported yet. Cytoplasmic-replicating viruses use their own repair enzymes for homologous recombination, while nuclear-replicating viruses use the host repair machinery. This is translated into a wide range of Cas9-induced homologous recombination efficiency depending on the virus replication compartment and viral/host repair machinery characteristics and accessibility. However, the use of Cas9 as a selection agent to target parental virus genomes robustly improves the selection of desired recombinants across large dsDNA viruses. We used ectromelia virus (ECTV) and herpes simplex viruses (HSV) type 1 and 2, to optimize a CRISPR/Cas9 method that can be versatilely used for efficient genome editing and selection of both cytoplasmic- and nuclear-replicating viruses. We performed a genome-wide genetic variant analysis of mutations located at predicted off-target sequences for 20 different recombinants, showing off-target-free accuracy by deep-sequencing. Our results support this optimized method as an efficient, accurate and versatile approach to enhance the two critical factors of high-throughput viral genome engineering: generation and color-based selection of recombinants. This application of CRISPR/Cas9 reduces time and labor of screening of desired recombinants, allowing for high-throughput generation of large collections of mutant dsDNA viruses for a desire locus in less than two weeks. DATA SUMMARYRaw sequence reads are available at the European Bioinformatics Institute (EMBL-EBI) European Nucleotide Archive (ENA) as Bioproject ID PRJEB32151 and PRJEB32152. Six supplementary figures, eleven supplementary tables and supplementary methods are available with the online version of this article. The authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.

microbiology↗

bioRxiv2021

Herpes simpex virus 2 (HSV-2) evolves faster in cell culture than HSV-1 by generating greater genetic diversity

Herpes simplex virus type 1 and 2 (HSV-1 and HSV-2, respectively) are prevalent human pathogens of clinical relevance that establish long-life latency in the nervous system. They have been considered, along with the Herpesviridae family, to exhibit a low level of genetic diversity during viral replication. However, the high ability shown by these viruses to rapidly evolve under different selective pressures does not correlates with that presumed genetic stability. High-throughput sequencing has revealed that heterogeneous or plaque-purified populations of both serotypes contain a broad range of genetic diversity, in terms of number and frequency of minor genetic variants, both in vivo and in vitro. This is reminiscent of the quasispecies phenomenon traditionally associated with RNA viruses. Here, by plaque-purification of two selected viral clones of each viral subtype, we reduced the high level of genetic variability found in the original viral stocks, to more genetically homogeneous populations. After having deeply characterized the genetic diversity present in the purified viral clones as a high confidence baseline, we examined the generation of de novo genetic diversity under culture conditions. We found that both serotypes gradually increased the number of de novo minor variants, as well as their frequency, in two different cell types after just five and ten passages. Remarkably, HSV-2 populations displayed a much higher raise of nonconservative de novo minor variants than the HSV-1 counterparts. Most of these minor variants exhibited a very low frequency in the population, increasing their frequency over sequential passages. These new appeared minor variants largely impacted the coding diversity of HSV-2, and we found some genes more prone to harbor higher variability. These data show that herpesviruses generate de novo genetic diversity differentially under equal in vitro culture conditions. This might have contributed to the evolutionary divergence of HSV-1 and HSV-2 adapting to different anatomical niche, boosted by selective pressures found at each epithelial and neuronal tissue. AUTHOR SUMMARYHerpesviruses are highly human pathogens that establish latency in neurons of the peripheral nervous system. Colonization of nerve endings is required for herpes simplex virus (HSV) persistence and pathogenesis. HSV-1 global prevalence is much higher than HSV-2, in addition to their preferential tendency to infect the oronasal and genital areas, respectively. How these closely related viruses have been adapting and evolving to replicate and colonize these two different anatomical areas remains unclear. Herpesviruses were presumed to mutate much less than viruses with RNA genomes, due to the higher fidelity of the DNA polymerase and proofreading mechanisms when replicating. However, the worldwide accessibility and development of high-throughput sequencing technologies have revealed the heterogenicity and high diversity present in viral populations clinically isolated. Here we show that HSV-2 mutates much faster than HSV-1, when compared under similar and controlled cell culture conditions. This high mutation rate is translated into an increase in coding diversity, since the great majority of these new mutations lead to nonconservative changes in viral proteins. Understanding how herpesviruses differentially mutate under similar selective pressures is critical to prevent resistance to anti-viral drugs.

microbiology↗