Marc Ongena

Bio: Marc Ongena is an academic researcher from Gembloux Agro-Bio Tech. The author has contributed to research in topics: Surfactin & Bacillus amyloliquefaciens. The author has an hindex of 37, co-authored 154 publications receiving 4222 citations. Previous affiliations of Marc Ongena include University of Agricultural Sciences, Dharwad & University of Liège.

Beneficial effect of the rhizosphere microbial community for plant growth and health

Abstract: Effet benefique de la communaute microbienne de la rhizosphere sur la croissance et la sante des plantes. La rhizosphere est le volume du sol situe au voisinage immediat des racines des plantes et qui se caracterise par la presence d’exsudats racinaires (rhizodepots). Ces exsudats sont utilises par la microflore endemique en tant que signaux chimiques en plus d’etre un substrat nutritif disponible pour la croissance et le developpement de ces microorganismes dans la rhizosphere. Certaines de ces bacteries du sol, appelees PGPRs (Plant Growth Promoting Rhizobacteria), sont capables de coloniser les racines ou bien encore la rhizosphere, mais a la difference des autres bacteries rhizospheriques elles ont, en retour, un effet benefique sur la plante. Cet effet benefique peut etre direct, ou indirect. La promotion directe de la croissance est le resultat du pouvoir d’acquisition des nutriments ou de la stimulation des hormones de la plante. D’autres mecanismes indirects, mais le plus souvent lies a la croissance des plantes, sont impliques dans la reduction/suppression des pathogenes des plantes. Cet article decrit les differents mecanismes mis en jeu par les PGPRs dans leur environnement naturel pour influencer favorablement la croissance et la sante des plantes.

Lipopeptides as main ingredients for inhibition of fungal phytopathogens by Bacillus subtilis/amyloliquefaciens.

Abstract: Some isolates of the Bacillus subtilis/amyloliquefaciens species are known for their plant protective activity against fungal phytopathogens. It is notably due to their genetic potential to form an impressive array of antibiotics including non-ribosomal lipopeptides (LPs). In the work presented here, we wanted to gain further insights into the relative role of these LPs in the global antifungal activity of B. subtilis/amyloliquefaciens. To that end, a comparative study was conducted involving multiple strains that were tested against four different phytopathogens. We combined various approaches to further exemplify that secretion of those LPs is a crucial trait in direct pathogen ward off and this can actually be generalized to all members of these species. Our data illustrate that for each LP family, the fungitoxic activity varies in function of the target species and that the production of iturins and fengycins is modulated by the presence of pathogens. Our data on the relative involvement of these LPs in the biocontrol activity and modulation of their production are discussed in the context of natural conditions in the rhizosphere.

Insights into the defense-related events occurring in plant cells following perception of surfactin-type lipopeptide from Bacillus subtilis.

Abstract: Multiple strains of Bacillus subtilis were demonstrated to stimulate plant defense responses, and cyclic lipopeptides may be involved in the elicitation of this induced systemic resistance phenomenon. Here, we further investigated molecular events underlying the interaction between such lipopeptides and plant cells. Addition of surfactin but not fengycin or iturin in the micromolar range to tobacco cell suspensions induced defense-related early events such as extracellular medium alkalinization coupled with ion fluxes and reactive oxygen species production. Surfactin also stimulated the defense enzymes phenylalanine ammonia lyase and lipoxygenase and modified the pattern of phenolics produced by the elicited cells. The occurrence of these surfactin-elicited early events is closely related to Ca 2+ influx and dynamic changes in protein phosphorylation but is not associated with any marked phytotoxicity or adverse effect on the integrity and growth potential of the treated tobacco cells. Reduced activity of some homologues also indicates that surfactin perception is dictated by structural clues in both the acyl moiety and cyclic peptide part. Our results suggest that these molecules could interact without irreversible pore formation but in a way sufficient to induce disturbance or transient channeling in the plasma membrane that can, in turn, activate a biochemical cascade of molecular events leading to defensive responses. The present study sheds new light not only on defenserelated events induced following recognition of amphiphilic lipopeptides from Bacillus spp. but also more globally on the way elicitors from beneficial bacteria can be perceived by host plant cells.

Bacillus-based biological control of plant diseases

Abstract: Plant diseases cause considerable losses in crop production and storage. Nowadays, growers still rely heavily on chemical pesticides to prevent, or control these diseases. However, the high effectiveness and ease of utilization of these chemicals can result in environmental contamination and the presence of pesticide residues on food, in addition to social and economic problems. Consequently, there is an increasing demand from consumers and officials to reduce the use of chemical pesticides. In this context, biological control through the use of natural antagonistic microorganisms has emerged as a promising alternative. Indeed, these biopesticides present many advantages in term of sustainability, mode of action and toxicity compared to chemical pesticides. Here, we focus in details on the versatile utilization of Bacillus based products as biopesticides. More precisely, a special emphasis is given to the three main specific mechanisms involved in biocontrol of plant diseases by this bacterial genus: competition for ecological niche/substrate in the rhizosphere, production of inhibitory chemicals and induction of so-called systemic resistance in host plants. Beside this, strategies for enhancing the efficacy of Bacillus-based biopesticides are also discussed.

Plant Defense Stimulation by Natural Isolates of Bacillus Depends on Efficient Surfactin Production

Abstract: Some plant-associated Bacillus strains produce induced systemic resistance (ISR) in the host, which contributes to their protective effect against phytopathogens. Little is known about the variety of elicitors responsible for ISR that are produced by Bacillus strains. Working with a particular strain, we have previously identified the surfactin lipopeptide as a main compound stimulating plant immune-related responses. However, with the perspective of developing Bacillus strains as biocontrol agents, it is important to establish whether a central role of surfactin is generally true for isolates belonging to the B. subtilis/amyloliquefaciens complex. To that end, we set up a comparative study involving a range of natural strains. Their secretomes were first tested for triggering early defense events in cultured tobacco cells. Six isolates with contrasting activities were further evaluated for ISR in plants, based both on macroscopic disease reduction and on stimulation of the oxylipin pathway as defense mechanism. A strong correlation was found between defense-inducing activity and the amount of surfactin produced by the isolates. These results support the idea of a widespread role for surfactin as a nonvolatile elicitor formed by B. subtilis/amyloliquefaciens, and screening for strong surfactin producers among strains naturally secreting multiple antibiotics could be an efficient approach to select good candidates as biopesticides.

SPAdes, a new genome assembly algorithm and its applications to single-cell sequencing ( 7th Annual SFAF Meeting, 2012)

Abstract: The lion's share of bacteria in various environments cannot be cloned in the laboratory and thus cannot be sequenced using existing technologies. A major goal of single-cell genomics is to complement gene-centric metagenomic data with whole-genome assemblies of uncultivated organisms. Assembly of single-cell data is challenging because of highly non-uniform read coverage as well as elevated levels of sequencing errors and chimeric reads. We describe SPAdes, a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V-SC assembler (specialized for single-cell data) and on popular assemblers Velvet and SoapDeNovo (for multicell data). SPAdes generates single-cell assemblies, providing information about genomes of uncultivatable bacteria that vastly exceeds what may be obtained via traditional metagenomics studies. SPAdes is available online ( http://bioinf.spbau.ru/spades ). It is distributed as open source software.

Biological control of soil-borne pathogens by fluorescent pseudomonads

Abstract: Particular bacterial strains in certain natural environments prevent infectious diseases of plant roots. How these bacteria achieve this protection from pathogenic fungi has been analysed in detail in biocontrol strains of fluorescent pseudomonads. During root colonization, these bacteria produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors. Before engaging in these activities, biocontrol bacteria go through several regulatory processes at the transcriptional and post-transcriptional levels.

Use of Plant Growth-Promoting Bacteria for Biocontrol of Plant Diseases: Principles, Mechanisms of Action, and Future Prospects

Abstract: Pathogenic microorganisms affecting plant health are a major and chronic threat to food production and ecosystem stability worldwide As agricultural production intensified over the past few decades, producers became more and more dependent on agrochemicals as a relatively reliable method of crop

Microbial interactions and biocontrol in the rhizosphere

Abstract: The loss of organic material from the roots provides the energy for the development of active microbial populations in the rhizosphere around the root. Generally, saproptrophs or biotrophs such as mycorrhizal fungi grow in the rhizosphere in response to this carbon loss, but plant pathogens may also develop and infect a susceptible host, resulting in disease. This review examines the microbial interactions that can take place in the rhizosphere and that are involved in biological disease control. The interactions of bacteria used as biocontrol agents of bacterial and fungal plant pathogens, and fungi used as biocontrol agents of protozoan, bacterial and fungal plant pathogens are considered. Whenever possible, modes of action involved in each type of interaction are assessed with particular emphasis on antibiosis, competition, parasitism, and induced resistance. The significance of plant growth promotion and rhizosphere competence in biocontrol is also considered. Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced biocontrol in many cases in comparison with biocontrol agents used singly. The extreme complexity of interactions that can occur in the rhizosphere is highlighted and some potential areas for future research in this area are discussed briefly.