Biology subjects

Gilhar, O.

Publications and source records attributed to Gilhar, O..

3 recordsLinked to original sources

bioRxiv2022

Context-dependent differences in the functional responses of Lactobacillaeca strains to fermentable sugars

Lactobacillaceae are Gram-positive rods, facultative anaerobes, and belong to the lactic acid bacteria (LAB) that frequently serve as probiotics. We systematically compared five LAB strains for the effects of different carbohydrates on their free-living and biofilm lifestyles. We found that fermentable sugars triggered a heterogeneous response in LAB strains, frequently manifested specifically in altered carrying capacity during planktonic growth and colony development. The fermentation capacities of the strains were compatible and could not account for heterogeneity in their differential carrying capacity in liquid and on a solid medium. Among tested LAB strains, L. paracasei, and L. rhamanosus GG survived self-imposed acid stress while L. acidophilus was extremely sensitive to its own glucose utilization acidic products. The addition of a buffering system during growth on a solid medium significantly improved the survival of most tested probiotic strains during fermentation. We suggest that the optimal performance of the beneficial microbiota members belonging to lactobacilli is heterogeneous and varies as a function of the growth model and the dependency on a buffering system.

microbiology↗

bioRxiv2022

Arabidopsis thaliana induces multigenerational stress tolerance against biotic and abiotic stressors and memorization of host colonization in Bacillus subtilis

Bacillus subtilis is a beneficial bacterium that supports plant growth and protects it from bacterial, fungal, and viral infections. Here using a simplified system of B. subtilis, and Arabidopsis thaliana interactions, we found that history-dependent behavior is a potentially important manifestation of host colonization, worth classifying and quantifying. To study history-dependent adaptation to plant hosts, we develop a simple framework for measuring the physiological memory of B. subtilis following its interaction with Arabidopsis thaliana. We found that A. thaliana secretions reduce the lag time in pre-exposed bacteria compared with naive B. subtilis cells, even after their complete removal. Pre-exposed B. subtilis cells colonized plant roots more efficiently than naive bacteria, and were more resistant to biotic and abiotic stressors such as salicylic acid, and high salinity. Descendants of bacteria treated with plant secretions had an advantage in the competition against unexposed bacteria for root colonization. The effect of plant secretions was independent of their roles as nitrogen and carbon sources. Transcriptome analysis of both ancestors and descendants revealed that a specific set of plant-induced processes, among them c-di-AMP homeostasis, and the general stress response, maintain the signature of association with the plant in descendants of pre-exposed bacteria. Consistently, plant secretions compensated for the loss of c-di-AMP cyclases but required the general stress response and the master regulator Spo0A to exert their short and long-term effects. Overall, our work demonstrates that bacterial memory manifested by multigenerational reversible adaptation to plant hosts confirms an advantage to symbiotic bacteria during competition.

microbiology↗

bioRxiv2021

Quantifying the effects of the plant root on antibiotic production in the beneficial bacterium B. subtilis

Beneficial and probiotic bacteria play an important role in conferring the immunity of their hosts against a wide range of bacterial, viral and fungal diseases. B. subtilis is a bacterium that protects the plant from various pathogens due to its capacity to produce an extensive repertoire of antibiotics. At the same time, the plant microbiome is a highly competitive niche, with multiple microbial species competing for space and resources, a competition that can be determined by the antagonistic potential of each microbiome member. Therefore, regulating antibiotic production in the rhizosphere is of great significance to eliminate pathogens and to establish beneficial host-associated communities. In this work, we used Bacillus subtilis as a model to investigate the role of plant colonization in antibiotic production. Flow cytometry and Image-stream cytometry analysis supported the notion that A. thaliana specifically induced the transcription of the biosynthetic clusters for the non-ribosomal peptides surfactin, bacilysin and plipastatin and the polyketide bacillaene. This induction could be beneficial for the root as all clusters were shown to antagonize plant pathogens. Consistently, the root failed to induce PenP, a {beta}-lactamase that increases only the fitness of the bacteria. Our results can be translated to improve the performance and competitiveness of beneficial members of the plant microbiome.

microbiology↗