The olive knot disease as a model to study the role of interspecies bacterial communities in plant disease

Abstract

There is an increasing interest in studying interspecies bacterial interactions in diseases of animals and plants as it is believed that the great majority of bacteria found in nature live in complex communities. Plant pathologists have thus far mainly focused on studies involving single species or on their interactions with antagonistic competitors. A bacterial disease used as model to study multispecies interactions is the olive knot disease, caused by Pseudomonas savastanoi pv. savastanoi (Psv). Knots caused by Psv in branches and other aerial parts of the olive trees are an ideal niche not only for the pathogen but also for many other plant-associated bacterial species, mainly belonging to the genera Pantoea, Pectobacterium, Erwinia, and Curtobacterium. The non-pathogenic bacterial species Erwinia toletana, Pantoea agglomerans, and Erwinia oleae, which are frequently isolated inside the olive knots, cooperate with Psv in modulating the disease severity. Co-inoculations of these species with Psv result in bigger knots and better bacterial colonization when compared to single inoculations. Moreover, harmless bacteria co-localize with the pathogen inside the knots, indicating the formation of stable bacterial consortia that may facilitate the exchange of quorum sensing signals and metabolites. Here we discuss the possible role of bacterial communities in the establishment and development of olive knot disease, which we believe could be taking place in many other bacterial plant diseases.

Brenneria spp. and Rahnella victoriana associated with acute oak decline symptoms on oak and hornbeam in Iran

“…(e) However, the most likely explanation for lack of disease development in these pathogenicity tests is that B. goodwinii is not a primary pathogen solely responsible for the symptoms on oak and hornbeam in Iran and may work in concert with other species to form a pathobiome. This point is consistent with reports on AOD (Broberg et al, ; Denman et al, ) and other pathosystems (e.g., olive knot disease Buonaurio et al, ) and supports the idea of the combined pathogenic potential of organisms and polybacterial pathobiomes (Doonan et al, ; Gilbert et al, ). In Iran, ideally further testing of field samples using metabarcoding, metagenomics and metatranscriptomic methods would be carried out as recommended by Broberg et al (), Denman et al () and Doonan et al () to fully profile the pathobiome and compare it with the microbiome of non‐symptomatic trees to identify putative disease contributing members for further testing and to elucidate important functional genes and gene products in the pathobiome.…”

“…The other Brenneria species and R. victoriana also caused a HR but it took longer. The strong positive HR tests from B. goodwinii support the discovery that these bacteria have a functional type III secretion system (TTSS) (Doonan et al, 2019), which delivers elicitor proteins such as harpin that represents a key phytopathogenic virulence factor when introduced into host tissue (Alfano & Collmer, 1997;Wei et al, 1992), which could be one of the factors responsible for inducing the HR response in the geranium (Choi, Kim, Lee, & Oh, 2013 Denman et al, 2018) and other pathosystems (e.g., olive knot disease Buonaurio et al, 2015) and supports the idea of the combined pathogenic potential of organisms and polybacterial pathobiomes (Doonan et al, 2019;Gilbert et al, 2016). In Iran, ideally further testing of field samples using metabarcoding, metagenomics and metatranscriptomic methods would These trees exist in pure and mixed plantation stands amounting to about 6.5% of the forests (Panahi, 2011), but also occur throughout the natural reserves in the area.…”

Grapevine (Vitis vinifera) Crown Galls Host Distinct Microbiota

“…Interactions of nonpathogenic with pathogenic bacteria are known for tumors of olive trees, induced by Pseudomonas savastanoi (pv. savastanoi), which host a nonpathogenic Erwinia species (74). An Erwinia species (OTU_7832) was enriched in graft unions with a crown gall, and it seems to profit from the crown gall environment.…”

Bacterial Diseases of Crops

“…Indeed, a recent study reviewed a large number of plant diseases due to polymicrobial infections that are increasingly reported in the literature (Lamichhane and Venturi, 2015). Such polymicrobial diseases occur through a complex interaction between pathogenecommensal (Buonaurio et al, 2015) and pathogenepathogen (Lamichhane and Venturi, 2015) thereby leading not only to disease occurrence but also to increased disease severity. For this reason, a fifth and perhaps one of the most important factors should be included to the disease triangle, which can be called as "cooperation among microorganisms.…”