Biology subjects

Leveau, J. H. J.

Publications and source records attributed to Leveau, J. H. J..

3 recordsLinked to original sources

bioRxiv2025

Contribution of floral transmission to the assembly and health impact of bacterial communities in watermelon seeds

Flower-sourced assembly of seed microbiota remains an understudied ecological process. Here, we investigated the floral transmission pathway for bacterial acquisition by developing seeds of watermelon (Citrullus lanatus). Comparison of stigma- and seed-associated bacterial communities from field-grown C. lanatus revealed significant overlap: up to 40% of the bacterial diversity that was detected in seed was also found on stigmas. In a field pollinator exclusion experiment, honeybee visitation to flower stigmas had no significant effect on bacterial community composition in seeds. Among a collection of bacterial isolates from stigmas and seeds in the field, more than half (57%) were able to transmit to seeds after inoculation onto stigmas under laboratory conditions. Interestingly, for most bacterial strains, fruit set rates increased after floral inoculation, and in some cases even in the absence of transmission to the seed. We also found that bacterial isolates from watermelon stigmas and seeds had variable (i.e. positive or negative) effects on seed germination and seedling emergence. Our findings highlight the contribution of floral transmission to seed microbiota assembly and its consequences for plant fitness.

ecology↗

bioRxiv2021

Sporulation is dispensable for the vegetable-associated life cycle of the human pathogen Bacillus cereus

Bacillus cereus is a common food-borne pathogen that is responsible for important outbreaks of food poisoning in humans. Diseases caused by B. cereus usually exhibit two major symptoms, emetic or diarrheic, depending on the toxins produced. It is assumed that after the ingestion of contaminated vegetables or processed food, spores of enterotoxigenic B. cereus reach the intestine, where they germinate and produce the enterotoxins that are responsible for food poisoning. In our study, we observed that sporulation is required for the survival of B. cereus in leaves but is dispensable in ready-to-eat vegetables, such as endives. We demonstrate that vegetative cells of B. cereus that are originally impaired in sporulation but not biofilm formation are able to reach the intestine and cause severe disorders in a murine model. We propose that loss of part of the sporulation programme and reinforcement of structural factors related to adhesion, biofilm formation and pathogenic interaction with the host are adaptive traits of B. cereus with a life cycle primarily related to human hosts. Furthermore, our findings emphasise that the number of food poisoning cases associated with B. cereus is underestimated and suggest the need to revise the detection protocols, which are based primarily on spores and toxins.

ecology↗

bioRxiv2018

Persistence of Fusarium oxysporum f. sp. fragariae in soil through asymptomatic colonization of rotation crops

Asymptomatic plant colonization is hypothesized to enhance persistence of pathogenic forms of Fusarium oxysporum in the absence of a susceptible host. However, a correlation between pathogen populations on living plant tissues and soilborne populations after tillage has not been demonstrated. Living and dead tissues of broccoli, lettuce, spinach, wheat, cilantro, raspberry, and strawberry plants inoculated with Fusarium oxysporum f. sp. fragariae (the cause of Fusarium wilt of strawberry) were assayed to quantify the incidence of infection and extent of colonization by this pathogen. All crops could be infected by F. oxysporum f. sp. fragariae, but the extent of colonization varied between plant species. Pathogen population densities on non-living crown tissues incorporated into the soil matrix were typically greater than those observed on living tissues. Crop-dependent differences in the inoculum density of F. oxysporum f. sp. fragariae in soil were only observed after decomposition of crop residue. Forty-four weeks after plants were incorporated into the soil, F. oxysporum f. sp. fragariae soil population densities were positively correlated with population densities on plant tissue fragments recovered at the same timepoint. Results indicate that asymptomatic colonization can have a significant, long-term impact on soilborne populations of Fusarium wilt pathogens. Cultural practices, such as crop rotation, should be leveraged to favor pathogen population decline by planting hosts that do not support extensive population growth on living or decomposing tissues.

microbiology↗