Erwinia persicina Causing Chlorosis and Necrotic Spots in Leaves and Tendrils of Pisum sativum in Southeastern Spain

Genome analysis of Erwinia persicina reveals implications for soft rot pathogenicity in plants

Soft rot disease causes devastating losses to crop plants all over the world, with up to 90% loss in tropical climates. To better understand this economically important disease, we isolated four soft rot-causing Erwinia persicina strains from rotted vegetables. Notably, E. persicina has only recently been identified as a soft rot pathogen and a comprehensive genomic analysis and comparison has yet to be conducted. Here, we provide the first genomic analysis of E. persicina, compared to Pectobacterium carotovorum, P. carotovorum, and associated Erwinia plant pathogens. We found that E. persicina shares common genomic features with other Erwinia species and P. carotovorum, while having its own unique characteristics as well. The E. persicina strains examined here lack Type II and Type III secretion systems, commonly used to secrete pectolytic enzymes and evade the host immune response, respectively. E. persicina contains fewer putative pectolytic enzymes than P. carotovorum and lacks the Out cluster of the Type II secretion system while harboring a siderophore that causes a unique pink pigmentation during soft rot infections. Interestingly, a putative phenolic acid decarboxylase is present in the E. persicina strains and some soft rot pathogens, but absent in other Erwinia species, thus potentially providing an important factor for soft rot. All four E. persicina isolates obtained here and many other E. persicina genomes contain plasmids larger than 100 kbp that encode proteins likely important for adaptation to plant hosts. This research provides new insights into the possible mechanisms of soft rot disease by E. persicina and potential targets for diagnostic tools and control measures.

Seed-Borne Erwinia persicina Affects the Growth and Physiology of Alfalfa (Medicago sativa L.)

Seed-borne Erwinia persicina can be transmitted globally via alfalfa (Medicago sativa L.) seed trade, but there is limited information about the impact of this plant-pathogenic bacterium on alfalfa plants. In this study, strain Cp2, isolated from alfalfa seeds, was confirmed by whole-genome sequencing to belong to E. persicina. Subsequently, the effects of Cp2 on alfalfa growth and physiology were evaluated by constructing a rhizosphere infection model. Strain Cp2 had a strong inhibitory effect on the elongation and growth of alfalfa roots, which was very unfavorable to these perennial plants. Furthermore, an increased number of leaf spots and yellowing symptoms were observed in plants of the Cp2 group from day 10 to day 21 and the strain Cp2 was re-isolated from these leaves. Correlation between growth and photosynthetic parameters was analyzed and the significant decreases in fresh weight and root and plant lengths in the Cp2 group were related to the marked reduction of chlorophyll b, carotenoid, transpiration rate, and stomatal conductance of leaves (r > 0.75). In addition, nine physiological indicators of root, stem, and leaf were measured in the plants 21 days after treatment with Cp2. The physiological response of root and leaf to Cp2 treatment was stronger than that of stem. The physiological indicators with the greatest response to Cp2 infection were further explored through principal component analysis, and superoxide dismutase, peroxidase, ascorbate peroxidase, and soluble protein showed the greatest changes in roots, stems, and leaves (P < 0.001). Among tissues, the commonality was the change of soluble protein. Therefore, soluble protein is speculated to be a physiological marker during alfalfa–E. persicina interactions. These findings indicate that once E. persicina spreads from alfalfa seeds to the rhizosphere, it can invade alfalfa roots and cause disease. This study demonstrates that this plant pathogenic bacterium may be a potential threat to new environment when they spread via seed trade and these “dangerous hitchhikers” warrant further attention, especially in the study of bacterial diseases in pasture-based production systems.

Bioprospecting the Solar Panel Microbiome: High-Throughput Screening for Antioxidant Bacteria in a Caenorhabditis elegans Model

Microbial communities that are exposed to sunlight typically share a series of adaptations to deal with the radiation they are exposed to, including efficient DNA repair systems, pigment production and protection against oxidative stress, which makes these environments good candidates for the search of novel antioxidant microorganisms. In this research project, we isolated potential antioxidant pigmented bacteria from a dry and highly-irradiated extreme environment: solar panels. High-throughput in vivo assays using Caenorhabditis elegans as an experimental model demonstrated the high antioxidant and ultraviolet-protection properties of these bacterial isolates that proved to be rich in carotenoids. Our results suggest that solar panels harbor a microbial community that includes strains with potential applications as antioxidants.

A genome-wide analysis of desferrioxamine mediated iron uptake in Erwinia spp. reveals genes exclusive of the Rosaceae infecting strains

Erwinia amylovora is the etiological agent of fire blight, a devastating disease which is a global threat to commercial apple and pear production. The Erwinia genus includes a wide range of different species belonging to plant pathogens, epiphytes and even opportunistic human pathogens. The aim of the present study is to understand, within the Erwinia genus, the genetic differences between phytopathogenic strains and those strains not reported to be phytopathogenic. The genes related to the hydroxamate siderophores iron uptake have been considered due to their potential druggability. In E. amylovora siderophore-mediated iron acquisition plays a relevant role in the progression of Fire blight. Here we analyzed the taxonomic relations within Erwinia genus and the relevance of the genes related to the siderophore-mediated iron uptake pathway. The results of this study highlight the presence of a well-defined sub-group of Rosaceae infecting species taxonomically and genetically related with a high number of conserved core genes. The analysis of the complete ferrioxamine transport system has led to the identification of two genes exclusively present in the Rosaceae infecting strains.

Whole-Genome Sequence of Erwinia persicina B64, Which Causes Pink Soft Rot in Onions

Erwinia persicina B64 was isolated from rotten onions in cold-storage facilities. Here, we report the complete genome sequence of E. persicina B64, which contains 5,070,450 bp with 55.17% GC content. The genome of this isolate is composed of one chromosome and two plasmids.

Conservation of Erwinia amylovora pathogenicity-relevant genes among Erwinia genomes

The Erwinia genus comprises species that are plant pathogens, non-pathogen, epiphytes, and opportunistic human pathogens. Within the genus, Erwinia amylovora ranks among the top 10 plant pathogenic bacteria. It causes the fire blight disease and is a global threat to commercial apple and pear production. We analyzed the presence/absence of the E. amylovora genes reported to be important for pathogenicity towards Rosaceae within various Erwinia strains genomes. This simple bottom-up approach, allowed us to correlate the analyzed genes to pathogenicity, host specificity, and make useful considerations to drive targeted studies.

Bacteria Associated With Piezodorus guildinii (Hemiptera: Pentatomidae), With Special Reference to Those Transmitted by Feeding

The redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Heteroptera: Pentatomidae), is a rapidly growing pest damaging southern US agriculture. Pentatomid stink bugs are known to vector bacterial, fungal, and viral plant diseases. However, bacteria associated with redbanded stink bugs and their vector potential have not yet been assessed. In this study, we 1) cultured and identified bacteria transmitted by feeding of redbanded stink bug and 2) described bacteria from guts of redbanded stink bug individuals using next-generation sequencing of 16S rRNA genes. Nineteen bacteria transmitted by feeding of redbanded stink bug on soybean agar were isolated and identified via Sanger sequencing of near full length 16S RNA genes. The transmitted bacteria belonged to at least a dozen species in eight genera and included potential plant pathogens (Phaseolibacter flectens), plant beneficials (Bacillus atropheus), and possible insect beneficials (Acinetobacter sp. and Citrobacter farmeri). A total of 284,448 reads were captured from Illumina MiSeq sequencing of the uncultured gut bacteria community. Fifty-one putative bacteria species (74% of the estimated total species richness) were identified via matches to NCBI databases. The bacteria metagenome contained potential plant and insect pathogens (Erwinia persicina, E. rhaponici, Brenneria nigrifluens, Ralstonia picketti, and Serratia marcescens) and beneficials (Pantoea dispersa, Klebsiella oxytoca, Clostridium butyricum, and Citrobacter farmeri).