Microbe Profile: : an enemy at the door.

is part of a larger family of soft rot bacteria () that cause disease on a wide range of crops worldwide. They are closely related to members of the and, as the plant pathogens and plant associated members of the group, form part of a continuum towards opportunistic and more devastating animal and human pathogens. Many of the horizontally acquired islands present in the genome of are directly responsible for life on plants.

Expansin-like Exl1 from Pectobacterium is a virulence factor required for host infection, and induces a defence plant response involving ROS, and jasmonate, ethylene and salicylic acid signalling pathways in Arabidopsis thaliana.

Expansins are encoded by some phytopathogenic bacteria and evidence indicates that they act as virulence factors for host infection. Here we analysed the expression of exl1 by Pectobacterium brasiliense and Pectobacterium atrosepticum. In both, exl1 gene appears to be under quorum sensing control, and protein Exl1 can be observed in culture medium and during plant infection.

The rsmS (ybaM) mutation causes bypass suppression of the RsmAB post-transcriptional virulence regulation system in enterobacterial phytopathogens.

Plant cell wall degrading enzymes (PCWDEs) are the primary virulence determinants of soft rotting bacteria such as the potato pathogen, Pectobacterium atrosepticum. The regulation of secondary metabolite (Rsm) system controls production of PCWDEs in response to changing nutrient conditions. This work identified a new suppressor of an rsmB mutation - ECA1172 or rsmS (rsmB suppressor).

Threat of establishment of non-indigenous potato blackleg and tuber soft rot pathogens in Great Britain under climate change.

Potato blackleg and soft rot caused by Pectobacterium and Dickeya species are among the most significant bacterial diseases affecting potato production globally. In this study we estimate the impact of future temperatures on establishment of non-indigenous but confirmed Pectobacterium and Dickeya species in Great Britain (GB). The calculations are based on probabilistic climate change data and a model fitted to disease severity data from a controlled environment tuber assay with the dominant potato blackleg and soft rot-causing species in GB (P.

Mobilization of horizontally acquired island 2 is induced in planta in the phytopathogen Pectobacterium atrosepticum SCRI1043 and involves the putative relaxase ECA0613 and quorum sensing.

Integrative and conjugative elements (ICEs) contribute to the rapid evolution of bacterial pathogens via horizontal gene transfer of virulence determinants. ICEs have common mechanisms for transmission, yet the cues triggering this process under natural environmental or physiological conditions are largely unknown. In this study, mobilization of the putative ICE horizontally acquired island 2 (HAI2), present in the chromosome of the phytopathogen Pectobacterium atrosepticum SCRI1043, was examined during infection of the host plant potato.

Detection of the Bacterial Potato Pathogens Pectobacterium and Dickeya spp. Using Conventional and Real-Time PCR.

Blackleg and soft rot of potato, caused by Pectobacterium and Dickeya spp., are major production constraints in many potato-growing regions of the world. Despite advances in our understanding of the causative organisms, disease epidemiology, and control, blackleg remains the principal cause of down-grading and rejection of potato seed in classification schemes across Northern Europe and many other parts of the world.

Pantoea ananatis Utilizes a Type VI Secretion System for Pathogenesis and Bacterial Competition.

Type VI secretion systems (T6SSs) are a class of macromolecular machines that are recognized as an important virulence mechanism in several gram-negative bacteria. The genome of Pantoea ananatis LMG 2665(T), a pathogen of pineapple fruit and onion plants, carries two gene clusters whose predicted products have homology with T6SS-associated gene products from other bacteria. Nothing is known regarding the role of these T6SS-1 and T6SS-3 gene clusters in the biology of P.

Escherichia coli common pilus (ECP) targets arabinosyl residues in plant cell walls to mediate adhesion to fresh produce plants.

Outbreaks of verotoxigenic Escherichia coli are often associated with fresh produce. However, the molecular basis to adherence is unknown beyond ionic lipid-flagellum interactions in plant cell membranes. We demonstrate that arabinans present in different constituents of plant cell walls are targeted for adherence by E.

Analysis of the Pantoea ananatis pan-genome reveals factors underlying its ability to colonize and interact with plant, insect and vertebrate hosts.

Background: Pantoea ananatis is found in a wide range of natural environments, including water, soil, as part of the epi- and endophytic flora of various plant hosts, and in the insect gut. Some strains have proven effective as biological control agents and plant-growth promoters, while other strains have been implicated in diseases of a broad range of plant hosts and humans. By analysing the pan-genome of eight sequenced P.

Draft genome sequences of 17 isolates of the plant pathogenic bacterium dickeya.

Dickeya (formerly Erwinia chrysanthemi) species cause diseases on a wide range of crops and ornamental plants worldwide. Here we present the draft sequences of 17 Dickeya isolates spanning four Dickeya species, including five isolates that are currently unassigned to a species.

Dickeya solani sp. nov., a pectinolytic plant-pathogenic bacterium isolated from potato (Solanum tuberosum).

Pectinolytic bacteria have been recently isolated from diseased potato plants exhibiting blackleg and slow wilt symptoms found in a number of European countries and Israel. These Gram-reaction-negative, motile, rods were identified as belonging to the genus Dickeya, previously the Pectobacterium chrysanthemi complex (Erwinia chrysanthemi), on the basis of production of a PCR product with the pelADE primers, 16S rRNA gene sequence analysis, fatty acid methyl esterase analysis, the production of phosphatases and the ability to produce indole and acids from α-methylglucoside. Differential physiological assays used previously to differentiate between strains of E.

Flagella interact with ionic plant lipids to mediate adherence of pathogenic Escherichia coli to fresh produce plants.

Bacterial attachment to plant and animal surfaces is generally thought to constitute the initial step in colonization, requiring adherence factors such as flagella and fimbriae. We describe the molecular mechanism underpinning flagella-mediated adherence to plant tissue for the foodborne pathogen, enterohaemorrhagic Escherichia coli. Escherichia coli H7 flagella interacted with a sulphated carbohydrate (carrageenan) on a glycan array, which occurred in a dose-dependent manner.

The endophytic lifestyle of Escherichia coli O157:H7: quantification and internal localization in roots.

The foodborne pathogen Escherichia coli O157:H7 is increasingly associated with fresh produce (fruit and vegetables). Bacterial colonization of fresh produce plants can occur to high levels on the external tissue but bacteria have also been detected within plant tissue. However, questions remain about the extent of internalization, its molecular basis, and internal location of the bacteria.

A metabolic regulator modulates virulence and quorum sensing signal production in Pectobacterium atrosepticum.

Plant cell wall-degrading enzymes (PCWDE) are key virulence determinants in the pathogenesis of the potato pathogen Pectobacterium atrosepticum. In this study, we report the impact on virulence of a transposon insertion mutation in the metJ gene that codes for the repressor of the methionine biosynthesis regulon. In a mutant strain defective for the small regulatory RNA rsmB, PCWDE are not produced and virulence in potato tubers is almost totally abolished.

Climate Change and Defense against Pathogens in Plants.

Most reviews of climate change are epidemiological, focusing on impact assessment and risk mapping. However, there are many reports of the effects of environmental stress factors on defense mechanisms in plants against pathogens. We review those representative of key climate change-related stresses to determine whether there are any patterns or trends in adaptation responses.

Inactivation of PbTopo IIIβ causes hyper-excision of the Pathogenicity Island HAI2 resulting in reduced virulence of Pectobacterium atrosepticum.

Topoisomerase III enzymes are present only in a limited set of bacteria and their physiological role remains unclear. Here, we show that PbTopo IIIβ, a homologue of topoisomerase III encoded on the chromosome of Pectobacterium atrosepticum strain SCRI1043 (Pba SCRI1043), is involved in excision of HAI2, a discrete ~100 kb region, from the Pba SCRI1043 chromosome. HAI2 is a Pathogenicity Island (PAI) that encodes coronafacic acid (Cfa), a major virulence determinant required for infection of potato.

Alignment-free design of highly discriminatory diagnostic primer sets for Escherichia coli O104:H4 outbreak strains.

Background: An Escherichia coli O104:H4 outbreak in Germany in summer 2011 caused 53 deaths, over 4000 individual infections across Europe, and considerable economic, social and political impact. This outbreak was the first in a position to exploit rapid, benchtop high-throughput sequencing (HTS) technologies and crowdsourced data analysis early in its investigation, establishing a new paradigm for rapid response to disease threats. We describe a novel strategy for design of diagnostic PCR primers that exploited this rapid draft bacterial genome sequencing to distinguish between E.

A multi-repeat adhesin of the phytopathogen, Pectobacterium atrosepticum, is secreted by a Type I pathway and is subject to complex regulation involving a non-canonical diguanylate cyclase.

Cyclic diguanylate (c-di-GMP) is a second messenger controlling many important bacterial processes. The phytopathogen Pectobacterium atrosepticum SCRI1043 (Pba1043) possesses a Type I secretion system (T1SS) essential for the secretion of a proteinaceous multi-repeat adhesin (MRP) required for binding to the host plant. The genes encoding the MRP and the T1SS are tightly linked to genes encoding several putative c-di-GMP regulatory components.

Genetic characterization of the HrpL regulon of the fire blight pathogen Erwinia amylovora reveals novel virulence factors.

The bacterial pathogen Erwinia amylovora is the causal agent of fire blight, an economically significant disease of apple and pear. Disease initiation by E. amylovora requires the translocation of effector proteins into host cells via the hypersensitive response and pathogenicity (hrp) type III secretion system (T3SS).

Genome-wide identification of HrpL-regulated genes in the necrotrophic phytopathogen Dickeya dadantii 3937.

Background: Dickeya dadantii is a necrotrophic pathogen causing disease in many plants. Previous studies have demonstrated that the type III secretion system (T3SS) of D. dadantii is required for full virulence.

Reverse engineering gene regulatory networks related to quorum sensing in the plant pathogen Pectobacterium atrosepticum.

The objective of the project reported in the present chapter was the reverse engineering of gene regulatory networks related to quorum sensing in the plant pathogen Pectobacterium atrosepticum from micorarray gene expression profiles, obtained from the wild-type and eight knockout strains. To this end, we have applied various recent methods from multivariate statistics and machine learning: graphical Gaussian models, sparse Bayesian regression, LASSO (least absolute shrinkage and selection operator), Bayesian networks, and nested effects models. We have investigated the degree of similarity between the predictions obtained with the different approaches, and we have assessed the consistency of the reconstructed networks in terms of global topological network properties, based on the node degree distribution.

Genome sequence of Pantoea ananatis LMG20103, the causative agent of Eucalyptus blight and dieback.

Pantoea ananatis is a Gram-negative plant pathogen that causes disease on a broad range of host plants, including pineapple, maize, rice, onion, melons, and Eucalyptus, and has been implicated in several cases of human disease. Here, we report the genome sequence of P. ananatis LMG20103 isolated from diseased Eucalyptus in South Africa.

Microarray comparative genomic hybridisation analysis incorporating genomic organisation, and application to enterobacterial plant pathogens.

Microarray comparative genomic hybridisation (aCGH) provides an estimate of the relative abundance of genomic DNA (gDNA) taken from comparator and reference organisms by hybridisation to a microarray containing probes that represent sequences from the reference organism. The experimental method is used in a number of biological applications, including the detection of human chromosomal aberrations, and in comparative genomic analysis of bacterial strains, but optimisation of the analysis is desirable in each problem domain.We present a method for analysis of bacterial aCGH data that encodes spatial information from the reference genome in a hidden Markov model.

Quorum sensing coordinates brute force and stealth modes of infection in the plant pathogen Pectobacterium atrosepticum.

Quorum sensing (QS) in vitro controls production of plant cell wall degrading enzymes (PCWDEs) and other virulence factors in the soft rotting enterobacterial plant pathogen Pectobacterium atrosepticum (Pba). Here, we demonstrate the genome-wide regulatory role of QS in vivo during the Pba-potato interaction, using a Pba-specific microarray. We show that 26% of the Pba genome exhibited differential transcription in a QS (expI-) mutant, compared to the wild-type, suggesting that QS may make a greater contribution to pathogenesis than previously thought.

DsbA plays a critical and multifaceted role in the production of secreted virulence factors by the phytopathogen Erwinia carotovora subsp. atroseptica.

Erwinia carotovora subsp. atroseptica is an enterobacterial phytopathogen causing economically significant soft rot disease. Pathogenesis is mediated by multiple secreted virulence factors, many of which are secreted by the type II (Out) secretion system.