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Dixon MH, Nellore D, Zaacks SC, Barak JD. Time of arrival during plant disease progression and humidity additively influence Salmonella enterica colonization of lettuce. Appl Environ Microbiol 2024; 90:e0131124. [PMID: 39207142 PMCID: PMC11409676 DOI: 10.1128/aem.01311-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2024] [Accepted: 08/01/2024] [Indexed: 09/04/2024] Open
Abstract
The interplay between plant hosts, phytopathogenic bacteria, and enteric human pathogens in the phyllosphere has consequences for human health. Salmonella enterica has been known to take advantage of phytobacterial infection to increase its success on plants, but there is little knowledge of additional factors that may influence the relationship between enteric pathogens and plant disease. In this study, we investigated the role of humidity and the extent of plant disease progression on S. enterica colonization of plants. We found that high humidity was necessary for the replication of S. enterica on diseased lettuce, but not required for S. enterica ingress into the UV-protected apoplast. Additionally, the Xanthomonas hortorum pv. vitians (hereafter, X. vitians)-infected lettuce host was found to be a relatively hostile environment for S. enterica when it arrived prior to the development of watersoaking or following necrosis onset, supporting the existence of an ideal window during X. vitians infection progress that maximizes S. enterica survival. In vitro growth studies in sucrose media suggest that X. vitians may allow S. enterica to benefit from cross-feeding during plant infection. Overall, this study emphasizes the role of phytobacterial disease as a driver of S. enterica success in the phyllosphere, demonstrates how the time of arrival during disease progress can influence S. enterica's fate in the apoplast, and highlights the potential for humidity to transform an infected apoplast into a growth-promoting environment for bacterial colonizers. IMPORTANCE Bacterial leaf spot of lettuce caused by Xanthomonas hortorum pv. vitians is a common threat to leafy green production. The global impact caused by phytopathogens, including X. vitians, is likely to increase with climate change. We found that even under a scenario where increased humidity did not enhance plant disease, high humidity had a substantial effect on facilitating Salmonella enterica growth on Xanthomonas-infected plants. High humidity climates may directly contribute to the survival of human enteric pathogens in crop fields or indirectly affect bacterial survival via changes to the phyllosphere brought on by phytopathogen disease.
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Affiliation(s)
- Megan H. Dixon
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin, Madison, Wisconsin, USA
| | - Dharshita Nellore
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin, USA
| | - Sonia C. Zaacks
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin, USA
| | - Jeri D. Barak
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin, USA
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Xanthomonas
Infection Transforms the Apoplast into an Accessible and Habitable Niche for Salmonella enterica. Appl Environ Microbiol 2022; 88:e0133022. [PMID: 36314834 PMCID: PMC9680631 DOI: 10.1128/aem.01330-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial spot disease caused by
Xanthomonas
species devastates tomato production worldwide. Salmonellosis outbreaks from consumption of raw produce have been linked to the arrival of
Salmonella enterica
on crop plants in the field via contaminated irrigation water.
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Salmonella enterica changes Macrosteles quadrilineatus feeding behaviors resulting in altered S. enterica distribution on leaves and increased populations. Sci Rep 2022; 12:8544. [PMID: 35595751 PMCID: PMC9122940 DOI: 10.1038/s41598-022-11750-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 04/28/2022] [Indexed: 11/08/2022] Open
Abstract
Hemipteran insects are ubiquitous inhabitants of the phyllosphere. Changes in microbial phyllosphere communities have recently been demonstrated following infestation by Macrosteles quadrilineatus (Aster Leafhopper). Although epiphytic Salmonella enterica populations naturally decline in the phyllosphere of plants, M. quadrilineatus infestation facilitated the growth of the bacterial pathogen populations. Here, we demonstrate that cellular damage by insect stylet penetration results in a localized beneficial niche on the leaf surface, leading to enhanced S. enterica populations. We measured S. enterica populations and colonization patterns on plants infested with Hemipterans with distinct feeding behaviors. M. quadrilineatus infestation resulted in higher solute leakage and significantly greater bacterial populations than plants absent of insects. Following immigration via contaminated irrigation water, the highest populations of S. enterica are naturally found on the tips of tomato leaflets. We discovered M. quadrilineatus feeding preference altered the natural distribution of S. enterica populations, and that the presence of S. enterica altered the distribution of probing attempts. These findings elucidate how cellular damage resulting from insect feeding drives changes in bacterial colonization of the phyllosphere.
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Cowles KN, Block AK, Barak JD. Xanthomonas hortorum pv. gardneri TAL effector AvrHah1 is necessary and sufficient for increased persistence of Salmonella enterica on tomato leaves. Sci Rep 2022; 12:7313. [PMID: 35508535 PMCID: PMC9068798 DOI: 10.1038/s41598-022-11456-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 04/25/2022] [Indexed: 01/16/2023] Open
Abstract
Salmonella enterica is ubiquitous in the plant environment, persisting in the face of UV stress, plant defense responses, desiccation, and nutrient limitation. These fluctuating conditions of the leaf surface result in S. enterica population decline. Biomultipliers, such as the phytopathogenic bacterium Xanthomonas hortorum pv. gardneri (Xhg), alter the phyllosphere to the benefit of S. enterica. Specific Xhg-dependent changes to this niche that promote S. enterica persistence remain unclear, and this work focuses on identifying factors that lead to increased S. enterica survival on leaves. Here, we show that the Xhg transcription activator-like effector AvrHah1 is both necessary and sufficient for increased survival of S. enterica on tomato leaves. An Xhg avrHah1 mutant fails to influence S. enterica survival while addition of avrHah1 to X. vesicatoria provides a gain of function. Our results indicate that although Xhg stimulates a robust immune response from the plant, AvrHah1 is not required for these effects. In addition, we demonstrate that cellular leakage that occurs during disease is independent of AvrHah1. Investigation of the interaction between S. enterica, Xhg, and the plant host provides information regarding how an inhospitable environment changes during infection and can be transformed into a habitable niche.
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Affiliation(s)
- Kimberly N Cowles
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA
| | - Anna K Block
- Center for Medical, Agricultural, and Veterinary Entomology, U.S. Department of Agriculture-Agricultural Research Service, Gainesville, FL, USA
| | - Jeri D Barak
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA.
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5
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Al-Subhi AM, Al-Sadi AM, Al-Yahyai RA, Chen Y, Mathers T, Orlovskis Z, Moro G, Mugford S, Al-Hashmi KS, Hogenhout SA. Witches' Broom Disease of Lime Contributes to Phytoplasma Epidemics and Attracts Insect Vectors. PLANT DISEASE 2021; 105:2637-2648. [PMID: 33349007 DOI: 10.1094/pdis-10-20-2112-re] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
An insect-transmitted phytoplasma causing Witches' Broom Disease of Lime (WBDL) is responsible for the drastic decline in lime production in several countries. However, it is unclear how WBDL phytoplasma (WBDLp) induces witches' broom symptoms and if these symptoms contribute to the spread of phytoplasma. Here we show that the gene encoding SAP11 of WBDLp (SAP11WBDL) is present in all WBDLp isolates collected from diseased trees. SAP11WBDL interacts with acid lime (Citrus aurantifolia) TCP transcription factors, specifically members of the TB1/CYC class that have a role in suppressing axillary branching in plants. Sampling of WBDLp-infected lime trees revealed that WBDLp titers and SAP11WBDL expression levels were higher in symptomatic leaves compared with asymptomatic sections of the same trees. Moreover, the witches' brooms were found to attract the vector leafhopper. Defense genes that have a role in plant defense responses to bacteria and insects are more downregulated in witches' brooms compared with asymptomatic sections of trees. These findings suggest that witches' broom-affected parts of the trees contribute to WBDL epidemics by supporting higher phytoplasma titers and attracting insect vectors.
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Affiliation(s)
- A M Al-Subhi
- Department of Plant Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khod 123, Oman
| | - A M Al-Sadi
- Department of Plant Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khod 123, Oman
| | - R A Al-Yahyai
- Department of Plant Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khod 123, Oman
| | - Y Chen
- John Innes Centre, Department of Crop Genetics, Norwich NR4 7UH, United Kingdom
| | - T Mathers
- John Innes Centre, Department of Crop Genetics, Norwich NR4 7UH, United Kingdom
| | - Z Orlovskis
- John Innes Centre, Department of Crop Genetics, Norwich NR4 7UH, United Kingdom
| | - G Moro
- John Innes Centre, Department of Crop Genetics, Norwich NR4 7UH, United Kingdom
| | - S Mugford
- John Innes Centre, Department of Crop Genetics, Norwich NR4 7UH, United Kingdom
| | - K S Al-Hashmi
- Department of Plant Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khod 123, Oman
| | - S A Hogenhout
- John Innes Centre, Department of Crop Genetics, Norwich NR4 7UH, United Kingdom
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Frankliniella occidentalis facilitate Salmonella enterica survival in the phyllosphere. PLoS One 2021; 16:e0247325. [PMID: 33606799 PMCID: PMC7895381 DOI: 10.1371/journal.pone.0247325] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 02/04/2021] [Indexed: 11/19/2022] Open
Abstract
The human enteric bacterial pathogen Salmonella enterica causes approximately 1.35 million cases of food borne illnesses annually in the United States. Of these salmonellosis cases, almost half are derived from the consumption of fresh, raw produce. Although epiphytic S. enterica populations naturally decline in the phyllosphere, a subset of phytophagous insects have recently been identified as biological multipliers, consequently facilitating the growth of bacterial populations. We investigated whether tomato leaves with macroscopic feeding damage, caused by infestation of adult Western flower thrips (Frankliniella occidentalis), support higher S. enterica populations. To explore this hypothesis, we assessed S. enterica populations in response to thrips feeding by varying insect density, plant age, and the gender of the insect. As a reference control, direct leaf damage analogous to thrips feeding was also evaluated using directed, hydraulic pressure. In a supplementary set series of experiments, groups of F. occidentalis infested tomato plants were later inoculated with S. enterica to determine how prior insect infestation might influence bacterial survival and persistence. Following an infestation period, leaves visibly damaged by adult F. occidentalis supported significantly higher S. enterica populations and resulted in greater amounts of electrolyte leakage (measured as electrical conductivity) than leaves lacking visible feeding damage. Plant age did not significantly influence S. enterica populations or estimates of electrolyte leakage, independent of initial infestation. Additionally, the gender of the insect did not uniquely influence S. enterica population dynamics. Finally, applications of aggressive water bombardment resulted in more electrolyte leakage than leaves damaged by F. occidentalis, yet supported comparable S. enterica populations. Together, this study indicates that F. occidentalis feeding is one of the many potential biological mechanisms creating a more habitable environment for S. enterica.
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Schierstaedt J, Grosch R, Schikora A. Agricultural production systems can serve as reservoir for human pathogens. FEMS Microbiol Lett 2020; 366:5715908. [PMID: 31981360 DOI: 10.1093/femsle/fnaa016] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 01/21/2020] [Indexed: 12/31/2022] Open
Abstract
Food-borne diseases are a threat to human health and can cause severe economic losses. Nowadays, in a growing and increasingly interconnected world, food-borne diseases need to be dealt with in a global manner. In order to tackle this issue, it is essential to consider all possible entry routes of human pathogens into the production chain. Besides the post-harvest handling of the fresh produce itself, also the prevention of contamination in livestock and agricultural soils are of particular importance. While the monitoring of human pathogens and intervening measures are relatively easy to apply in livestock and post-harvest, the investigation of the prevention strategies in crop fields is a challenging task. Furthermore, crop fields are interconnected with livestock via fertilizers and feed; therefore, a poor hygiene management can cause cross-contamination. In this review, we highlight the possible contamination of crop plants by bacterial human pathogens via the rhizosphere, their interaction with the plant and possible intervention strategies. Furthermore, we discuss critical issues and questions that are still open.
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Affiliation(s)
- Jasper Schierstaedt
- Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops, 14979 Großbeeren, Germany
| | - Rita Grosch
- Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops, 14979 Großbeeren, Germany
| | - Adam Schikora
- Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, 38104 Braunschweig, Germany
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