Molecular Keys to the Janthinobacterium and Duganella spp. Interaction with the Plant Pathogen Fusarium graminearum

Abstract

Janthinobacterium and Duganella are well-known for their antifungal effects. Surprisingly, almost nothing is known on molecular aspects involved in the close bacterium-fungus interaction. To better understand this interaction, we established the genomes of 11 Janthinobacterium and Duganella isolates in combination with phylogenetic and functional analyses of all publicly available genomes. Thereby, we identified a core and pan genome of 1058 and 23,628 genes. All strains encoded secondary metabolite gene clusters and chitinases, both possibly involved in fungal growth suppression. All but one strain carried a single gene cluster involved in the biosynthesis of alpha-hydroxyketone-like autoinducer molecules, designated JAI-1. Genome-wide RNA-seq studies employing the background of two isolates and the corresponding JAI-1 deficient strains identified a set of 45 QS-regulated genes in both isolates. Most regulated genes are characterized by a conserved sequence motif within the promoter region. Among the most strongly regulated genes were secondary metabolite and type VI secretion system gene clusters. Most intriguing, co-incubation studies of J. sp. HH102 or its corresponding JAI-1 synthase deletion mutant with the plant pathogen Fusarium graminearum provided first evidence of a QS-dependent interaction with this pathogen.

Bacterial endophyte communities in Pinus flexilis are structured by host age, tissue type, and environmental factors

“…Alternatively, the high proportion of Oxalobacteraceae could reflect some beneficial function like protection against fungal and oomycete pathogens. The top OTUs in the Oxalobacteraceae belong to the genus Janthinobacterium, which is recognized for antifungal activity (Haack et al 2016;Kueneman et al 2016). The most common shoot OTU 42 is similar to strains with antifungal activity, while OTU252, the second most common in shoots, was similar to a potato rhizosphere strain antagonistic against the oomycete Phytophthora infestans (Hunziker et al 2015), and to a strain from the disease-protective newt skin microbiome (Vences et al 2015).…”

Draft Genome Sequences of Two Janthinobacterium lividum Strains, Isolated from Pristine Groundwater Collected from the Oak Ridge Field Research Center

“…We also identified three genes known to regulate violacein biosynthesis (2): the sensor kinase jqsS , the response regulator jqsR , and the autoinducer synthase jqsA . Upstream regions of the vioABCDE operons in both strains contain the inverted repeat TTGATATTTATCAA, which coincides with the published JqsR binding motif (21). Thus, we propose that the expression of violacein biosynthesis operons in strains GW456P and GW458P is dependent on quorum sensing.…”

Biosynthesis and function of simple amides in Xenorhabdus doucetiae

“…Phenylethylamides extracted from the marine bacterium Halobacillus salinus exhibited quorum quenching activity against Chromobacterium violaceum and other reporter strains (Teasdale et al ., ). Selected amides from X. doucetiae with short, middle and long acyl chains were tested against Chromobacterium violaceum Bergonzini ATCC 12472 (Morohoshi et al ., ), C. violaceum CV026 (McClean et al ., ) and Janthinobacterium HH102 (Haack et al ., ) that all produce the pigment violacein in a quorum sensing (QS) dependent manner. C. violaceum uses acyl homoserine lactone (AHL) with acyl chain lengths from C 4 to C 6 (McClean et al ., ) as QS signal and, therefore, can function as reporter strain for quorum quenching activity.…”

“…Strain CV026 has a deletion of the genes involved in AHL biosynthesis and, therefore, is a reporter for QS activity of compounds. Strain HH102 produces JAI-1, a derivative of the a-hydroxyketone compounds CAI-1 and LAI-1 from Vibrio cholera and Legionella pneumophila, respectively (Hornung et al, 2013;Haack et al, 2016). Especially short chain acyl phenylethylamides (most similar to the natural AHLs in C. violaceum) were active in quorum quenching (Table 1, compounds 1-3, 50 and 51 Fig.…”