The plant pathogenic fungus Gaeumannomyces graminis var. tritici improves bacterial growth and triggers early gene regulations in the biocontrol strain Pseudomonas fluorescens Pf29Arp

Abstract

Summary• In soil, some antagonistic rhizobacteria contribute to reduce root diseases caused by phytopathogenic fungi. Direct modes of action of these bacteria have been largely explored; however, commensal interaction also takes place between these microorganisms and little is known about the influence of filamentous fungi on bacteria.• An in vitro confrontation bioassay between the pathogenic fungus Gaeumannomyces graminis var. tritici (Ggt) and the biocontrol bacterial strain Pseudomonas fluorescens Pf29Arp was set up to analyse bacterial transcriptional changes induced by the fungal mycelium at three time-points of the interaction before cell contact and up until contact. For this, a Pf29Arp shotgun DNA microarray was constructed. Specifity of Ggt effect was assessed in comparison with one of two other filamentous fungi, Laccaria bicolor and Magnaporthe grisea.• During a commensal interaction, Ggt increased the growth rate of Pf29Arp. Before contact, Ggt induced bacterial genes involved in mycelium colonization. At contact, genes encoding protein of stress response and a patatin-like protein were up-regulated. Among all the bacterial genes identified, xseB was specifically upregulated at contact by Ggt but down-regulated by the other fungi.• Data showed that the bacterium sensed the presence of the fungus early, but the main gene alteration occurred during bacterial-fungal cell contact.

Fluorescent Pseudomonas Strains with only Few Plant-Beneficial Properties Are Favored in the Maize Rhizosphere

“…The fluorescent Pseudomonas are key models to assess beneficial plant–bacteria interactions, because they display a wide range of plant-beneficial properties and play an important role in the rhizosphere, including in disease-suppressive soils (Weller and Cook, 1983; Lemanceau and Alabouvette, 1991; O’Sullivan and O’Gara, 1992; Bakker et al, 2007; Barret et al, 2009; Almario et al, 2014b). A given Pseudomonas PGPR strain generally displays many different modes of action on the plant, which is thought to be important to maximize plant benefits.…”

Transcriptomic responses of a simplified soil microcosm to a plant pathogen and its biocontrol agent reveal a complex reaction to harsh habitat

“…have been extensively studied using several approaches, including transcriptomics [17]. Most transcriptomic studies of microbial biocontrol mechanisms have focused on molecular responses of the biocontrol agent and the target plant pathogen in dual cultures [2, 7, 8, 10, 18]. However, microbial properties in complex consortia often differ from those of their single components [19].…”

Bacterial-Fungal Interactions: Hyphens between Agricultural, Clinical, Environmental, and Food Microbiologists

“…Indeed, various studies have used "omics" techniques to probe the changes that occur during BFIs at the subcellular level (25,94,167,231,235,259,281,352); for example, a recent study of the arbuscular mycorrhizal fungus Gigaspora margarita using combined proteomic and lipid metabolite profiling revealed that the presence of endobacteria had a significant impact on fungal physiology (331). Targeted approaches assessing the proteomic or transcriptomic responses of one BFI partner to molecules produced by the other also allow the testing of specific hypotheses relating to BFIs, such as responses to antibiotics (245,246).…”