1
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Meyer KM, Muscettola IE, Vasconcelos ALS, Sherman JK, Metcalf CJE, Lindow SE, Koskella B. Conspecific versus heterospecific transmission shapes host specialization of the phyllosphere microbiome. Cell Host Microbe 2023; 31:2067-2079.e5. [PMID: 38029741 DOI: 10.1016/j.chom.2023.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 09/09/2023] [Accepted: 11/01/2023] [Indexed: 12/01/2023]
Abstract
In disease ecology, pathogen transmission among conspecific versus heterospecific hosts is known to shape pathogen specialization and virulence, but we do not yet know if similar effects occur at the microbiome level. We tested this idea by experimentally passaging leaf-associated microbiomes either within conspecific or across heterospecific plant hosts. Although conspecific transmission results in persistent host-filtering effects and more within-microbiome network connections, heterospecific transmission results in weaker host-filtering effects but higher levels of interconnectivity. When transplanted onto novel plants, heterospecific lines are less differentiated by host species than conspecific lines, suggesting a shift toward microbiome generalism. Finally, conspecific lines from tomato exhibit a competitive advantage on tomato hosts against those passaged on bean or pepper, suggesting microbiome-level host specialization. Overall, we find that transmission mode and previous host history shape microbiome diversity, with repeated conspecific transmission driving microbiome specialization and repeated heterospecific transmission promoting microbiome generalism.
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Affiliation(s)
- Kyle M Meyer
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA.
| | - Isabella E Muscettola
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Ana Luisa S Vasconcelos
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Soil Science, College of Agriculture "Luiz de Queiroz", Universidade de São Paulo, Piracicaba 13418-900, Brazil
| | - Julia K Sherman
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - C Jessica E Metcalf
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Steven E Lindow
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Britt Koskella
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Chan Zuckerberg Biohub, San Francisco, San Francisco, CA 94158, USA
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2
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Lindow S. History of Discovery and Environmental Role of Ice Nucleating Bacteria. PHYTOPATHOLOGY 2023; 113:605-615. [PMID: 36122194 DOI: 10.1094/phyto-07-22-0256-ia] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The phenomenon of biological ice nucleation that is exhibited by a variety of bacteria is a fascinating phenotype, which has been shown to incite frost damage to frost-sensitive plants and has been proposed to contribute to atmospheric processes that affect the water cycle and earth's radiation balance. This review explores the several possible drivers for the evolutionary origin of the ice nucleation phenotype. These bacteria and the gene required for this phenotype have also been exploited in processes as diverse as reporter gene assays to assess environmentally responsive gene expression in various plant pathogenic and environmental bacteria and in the detection of foodborne human pathogens when coupled with host-specific bacteriophage, whereas ice nucleating bacteria themselves have been exploited in the production of artificial snow for recreation and oil exploration and in the process of freezing of various food products. This review also examines the historical development of our understanding of ice nucleating bacteria, details of the genetic determinants of ice nucleation, and features of the aggregates of membrane-bound ice nucleation protein necessary for catalyzing ice. Lastly, this review also explores the role of these bacteria in limiting the supercooling ability of plants and the strategies and limitations of avoiding plant frost damage by managing these bacterial populations by bactericides, antagonistic bacteria, or cultural control strategies.
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Affiliation(s)
- Steven Lindow
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720
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3
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Mansour A, Mannaa M, Hewedy O, Ali MG, Jung H, Seo YS. Versatile Roles of Microbes and Small RNAs in Rice and Planthopper Interactions. THE PLANT PATHOLOGY JOURNAL 2022; 38:432-448. [PMID: 36221916 PMCID: PMC9561162 DOI: 10.5423/ppj.rw.07.2022.0090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 06/16/2023]
Abstract
Planthopper infestation in rice causes direct and indirect damage through feeding and viral transmission. Host microbes and small RNAs (sRNAs) play essential roles in regulating biological processes, such as metabolism, development, immunity, and stress responses in eukaryotic organisms, including plants and insects. Recently, advanced metagenomic approaches have facilitated investigations on microbial diversity and its function in insects and plants, highlighting the significance of microbiota in sustaining host life and regulating their interactions with the environment. Recent research has also suggested significant roles for sRNA-regulated genes during rice-planthopper interactions. The response and behavior of the rice plant to planthopper feeding are determined by changes in the host transcriptome, which might be regulated by sRNAs. In addition, the roles of microbial symbionts and sRNAs in the host response to viral infection are complex and involve defense-related changes in the host transcriptomic profile. This review reviews the structure and potential functions of microbes and sRNAs in rice and the associated planthopper species. In addition, the involvement of the microbiota and sRNAs in the rice-planthopper-virus interactions during planthopper infestation and viral infection are discussed.
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Affiliation(s)
- Abdelaziz Mansour
- Department of Integrated Biological Science, Pusan National University, Busan 46241,
Korea
- Department of Economic Entomology and Pesticides, Faculty of Agriculture, Cairo University, Giza 12613,
Egypt
| | - Mohamed Mannaa
- Department of Integrated Biological Science, Pusan National University, Busan 46241,
Korea
- Department of Plant Pathology, Cairo University, Giza 12613,
Egypt
| | - Omar Hewedy
- Department of Plant Agriculture, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1,
Canada
- Department of Genetics, Faculty of Agriculture, Menoufia University, Shibin El-Kom 32514,
Egypt
| | - Mostafa G. Ali
- Department of Botany and Microbiology, Faculty of Science, Benha University, Benha 13518,
Egypt
| | - Hyejung Jung
- Department of Integrated Biological Science, Pusan National University, Busan 46241,
Korea
| | - Young-Su Seo
- Department of Integrated Biological Science, Pusan National University, Busan 46241,
Korea
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4
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Burgess EC, Schaeffer RN. The Floral Microbiome and Its Management in Agroecosystems: A Perspective. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:9819-9825. [PMID: 35917340 DOI: 10.1021/acs.jafc.2c02037] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Disease management is critical to ensuring healthy crop yields and is often targeted at flowers because of their susceptibility to pathogens and direct link to reproduction. Many disease management strategies are unsustainable however because of the potential for pathogens to evolve resistance, or nontarget effects on beneficial insects. Manipulating the floral microbiome holds some promise as a sustainable alternative to chemical means of disease control. In this perspective, we discuss the current state of research concerning floral microbiome assembly and management in agroecosystems as well as future directions aimed at improving the sustainability of disease control and insect-mediated ecosystem services.
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Affiliation(s)
- Emily C Burgess
- Department of Biology, Utah State University, Logan, Utah 84322, United States
| | - Robert N Schaeffer
- Department of Biology, Utah State University, Logan, Utah 84322, United States
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5
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Fessia A, Barra P, Barros G, Nesci A. Could Bacillus biofilms enhance the effectivity of biocontrol strategies in the phyllosphere? J Appl Microbiol 2022; 133:2148-2166. [PMID: 35476896 DOI: 10.1111/jam.15596] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 04/13/2022] [Accepted: 04/21/2022] [Indexed: 11/30/2022]
Abstract
Maize (Zea mays L.), a major crop in Argentina and a staple food around the world, is affected by the emergence and re-emergence of foliar diseases. Agrochemicals are the main control strategy nowadays, but they can cause resistance in insects and microbial pathogens and have negative effects on the environment and human health. An emerging alternative is the use of living organisms, i.e. microbial biocontrol agents, to suppress plant pathogen populations. This is a risk-free approach when the organisms acting as biocontrol agents come from the same ecosystem as the foliar pathogens they are meant to antagonize. Some epiphytic microorganisms may form biofilm by becoming aggregated and attached to a surface, as is the case of spore-forming bacteria from the genus Bacillus. Their ability to sporulate and their tolerance to long storage periods make them a frequently used biocontrol agent. Moreover, the biofilm that they create protects them against different abiotic and biotic factors and helps them to acquire nutrients, which ensures their survival on the plants they protect. This review analyzes the interactions that the phyllosphere-inhabiting Bacillus genus establishes with its environment through biofilm, and how this lifestyle could serve to design effective biological control strategies.
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Affiliation(s)
- Aluminé Fessia
- Laboratorio de Ecología Microbiana, Departamento de Microbiología e Inmunología, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ruta Nacional 36, Km 601, X5804ZAB Río Cuarto, Córdoba, Argentina
| | - Paula Barra
- Laboratorio de Ecología Microbiana, Departamento de Microbiología e Inmunología, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ruta Nacional 36, Km 601, X5804ZAB Río Cuarto, Córdoba, Argentina
| | - Germán Barros
- Laboratorio de Ecología Microbiana, Departamento de Microbiología e Inmunología, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ruta Nacional 36, Km 601, X5804ZAB Río Cuarto, Córdoba, Argentina
| | - Andrea Nesci
- Laboratorio de Ecología Microbiana, Departamento de Microbiología e Inmunología, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ruta Nacional 36, Km 601, X5804ZAB Río Cuarto, Córdoba, Argentina
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6
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Plant neighborhood shapes diversity and reduces interspecific variation of the phyllosphere microbiome. THE ISME JOURNAL 2022; 16:1376-1387. [PMID: 35022514 PMCID: PMC9038669 DOI: 10.1038/s41396-021-01184-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 12/15/2021] [Accepted: 12/23/2021] [Indexed: 01/04/2023]
Abstract
Microbial communities associated with plant leaf surfaces (i.e., the phyllosphere) are increasingly recognized for their role in plant health. While accumulating evidence suggests a role for host filtering of its microbiota, far less is known about how community composition is shaped by dispersal, including from neighboring plants. We experimentally manipulated the local plant neighborhood within which tomato, pepper, or bean plants were grown in a 3-month field trial. Focal plants were grown in the presence of con- or hetero-specific neighbors (or no neighbors) in a fully factorial combination. At 30-day intervals, focal plants were harvested and replaced with a new age- and species-matched cohort while allowing neighborhood plants to continue growing. Bacterial community profiling revealed that the strength of host filtering effects (i.e., interspecific differences in composition) decreased over time. In contrast, the strength of neighborhood effects increased over time, suggesting dispersal from neighboring plants becomes more important as neighboring plant biomass increases. We next implemented a cross-inoculation study in the greenhouse using inoculum generated from the field plants to directly test host filtering of microbiomes while controlling for directionality and source of dispersal. This experiment further demonstrated that focal host species, the host from which the microbiome came, and in one case the donor hosts' neighbors, contribute to variation in phyllosphere bacterial composition. Overall, our results suggest that local dispersal is a key factor in phyllosphere assembly, and that demographic factors such as nearby neighbor identity and biomass or age are important determinants of phyllosphere microbiome diversity.
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7
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Vannette RL, McMunn MS, Hall GW, Mueller TG, Munkres I, Perry D. Culturable bacteria are more common than fungi in floral nectar and are more easily dispersed by thrips, a ubiquitous flower visitor. FEMS Microbiol Ecol 2021; 97:6430164. [PMID: 34791198 DOI: 10.1093/femsec/fiab150] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 11/15/2021] [Indexed: 01/04/2023] Open
Abstract
Variation in dispersal ability among taxa affects community assembly and biodiversity maintenance within metacommunities. Although fungi and bacteria frequently coexist, their relative dispersal abilities are poorly understood. Nectar-inhabiting microbial communities affect plant reproduction and pollinator behavior, and are excellent models for studying dispersal of bacteria and fungi in a metacommunity framework. Here, we assay dispersal ability of common nectar bacteria and fungi in an insect-based dispersal experiment. We then compare these results with the incidence and abundance of culturable flower-inhabiting bacteria and fungi within naturally occurring flowers across two coflowering communities in California across two flowering seasons. Our microbial dispersal experiment demonstrates that bacteria disperse via thrips among artificial habitat patches more readily than fungi. In the field, incidence and abundance of culturable bacteria and fungi were positively correlated, but bacteria were much more widespread. These patterns suggest shared dispersal routes or habitat requirements among culturable bacteria and fungi, but differences in dispersal or colonization frequency by thrips, common flower visitors. The finding that culturable bacteria are more common among nectar sampled here, in part due to superior thrips-mediated dispersal, may have relevance for microbial life history, community assembly of microbes, and plant-pollinator interactions.
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Affiliation(s)
- Rachel L Vannette
- Department of Entomology and Nematology, University of California Davis, Davis, CA 95616, USA
| | - Marshall S McMunn
- Department of Entomology and Nematology, University of California Davis, Davis, CA 95616, USA
| | - Griffin W Hall
- Department of Entomology and Nematology, University of California Davis, Davis, CA 95616, USA
| | - Tobias G Mueller
- Department of Entomology and Nematology, University of California Davis, Davis, CA 95616, USA
| | - Ivan Munkres
- Department of Entomology and Nematology, University of California Davis, Davis, CA 95616, USA
| | - Douglas Perry
- Department of Entomology and Nematology, University of California Davis, Davis, CA 95616, USA
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8
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Mango Endophyte and Epiphyte Microbiome Composition during Fruit Development and Post-Harvest Stages. HORTICULTURAE 2021. [DOI: 10.3390/horticulturae7110495] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The influence of the development stage and post-harvest handling on the microbial composition of mango fruit plays a central role in fruit health. Hence, the composition of fungal and bacterial microbiota on the anthoplane, fructoplane, stems and stem-end pulp of mango during fruit development and post-harvest handling were determined using next-generation sequencing of the internal transcribed spacer and 16S rRNA regions. At full bloom, the inflorescence had the richest fungal and bacterial communities. The young developing fruit exhibited lower fungal richness and diversities in comparison to the intermediate and fully developed fruit stages on the fructoplane. At the post-harvest stage, lower fungal and bacterial diversities were observed following prochloraz treatment both on the fructoplane and stem-end pulp. Ascomycota (52.8%) and Basidiomycota (43.2%) were the most dominant fungal phyla, while Penicillium, Botryosphaeria, Alternaria and Mucor were detected as the known post-harvest decay-causing fungal genera. The Cyanobacteria (35.6%), Firmicutes (26.1%) and Proteobacteria (23.1%) were the most dominant bacterial phyla. Changes in the presence of Bacillus subtilis following post-harvest interventions such as prochloraz suggested a non-target effect of the fungicide. The present study, therefore, provides the primary baseline data on mango fungal and bacterial diversity and composition, which can be foundational in the development of effective disease (stem-end rot) management strategies.
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9
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Orchard Management and Landscape Context Mediate the Pear Floral Microbiome. Appl Environ Microbiol 2021; 87:e0004821. [PMID: 34020936 DOI: 10.1128/aem.00048-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Crop-associated microbiota are a key factor affecting host health and productivity. Most crops are grown within heterogeneous landscapes, and interactions between management practices and landscape context often affect plant and animal biodiversity in agroecosystems. However, whether these same factors typically affect crop-associated microbiota is less clear. Here, we assessed whether orchard management strategies and landscape context affected bacterial and fungal communities in pear (Pyrus communis) flowers. We found that bacteria and fungi responded differently to management schemes. Organically certified orchards had higher fungal diversity in flowers than conventional or bio-based integrated pest management (IPM) orchards, but organic orchards had the lowest bacterial diversity. Orchard management scheme also best predicted the distribution of several important bacterial and fungal genera that either cause or suppress disease; organic and bio-based IPM best explained the distributions of bacterial and fungal genera, respectively. Moreover, patterns of bacterial and fungal diversity were affected by interactions between management, landscape context, and climate. When examining the similarity of bacterial and fungal communities across sites, both abundance- and taxon-related turnovers were mediated primarily by orchard management scheme and landscape context and, specifically, the amount of land in cultivation. Our study reveals local- and landscape-level drivers of floral microbiome structure in a major fruit crop, providing insights that can inform microbiome management to promote host health and high-yielding quality fruit. IMPORTANCE Proper crop management during bloom is essential for producing disease-free tree fruit. Tree fruits are often grown in heterogeneous landscapes; however, few studies have assessed whether landscape context and crop management affect the floral microbiome, which plays a critical role in shaping plant health and disease tolerance. Such work is key for identification of tactics and/or contexts where beneficial microbes proliferate and pathogenic microbes are limited. Here, we characterize the floral microbiome of pear crops in Washington State, where major production occurs in intermountain valleys and basins with variable elevation and microclimates. Our results show that both local-level (crop management) and landscape-level (habitat types and climate) factors affect floral microbiota but in disparate ways for each kingdom. More broadly, these findings can potentially inform microbiome management in orchards for promotion of host health and high-quality yields.
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10
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Distinct Microbial Community of Phyllosphere Associated with Five Tropical Plants on Yongxing Island, South China Sea. Microorganisms 2019; 7:microorganisms7110525. [PMID: 31689928 PMCID: PMC6920945 DOI: 10.3390/microorganisms7110525] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 10/15/2019] [Accepted: 10/31/2019] [Indexed: 11/23/2022] Open
Abstract
The surfaces of a leaf are unique and wide habitats for a microbial community. These microorganisms play a key role in plant growth and adaptation to adverse conditions, such as producing growth factors to promote plant growth and inhibiting pathogens to protect host plants. The composition of microbial communities very greatly amongst different plant species, yet there is little data on the composition of the microbiome of the host plants on the coral island in the South China Sea. In this study, we investigated the abundances and members of a major microbial community (fungi, bacteria, and diazotrophs) on the leaves of five dominant plant species (Ipomoea pes-caprae, Wedelia chinensis, Scaevola sericea, Cocos nucifera, and Sesuvium portulacastrum) on the island using real-time quantitative polymerase chain reaction (PCR) and high-throughput amplicon sequencing. Quantitative PCR results showed that fungi and bacteria were ubiquitous and variable among different host plants. Scaevola sericea showed the lowest absolute abundance and highest diversity of fungi and bacteria, while Cocos nucifera had the lowest abundance and the highest diversity of diazotrophs compare to the other four plants. There was a small proportion of shared microorganisms among the five different plants, while unique fungi, bacteria and diazotrophs were significantly enriched for different host plant species in this study (p < 0.05). Some of the most abundant organisms found in the communities of these different host plants are involved in important biogeochemical cycles that can benefit their host, including carbon and nitrogen cycles.
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11
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Jia T, Wang RH, Chai BF. Various Phyllosphere and Soil Bacterial Communities of Natural Grasses and the Impact Factors in a Copper Tailings Dam. Curr Microbiol 2018; 76:7-14. [PMID: 30310969 DOI: 10.1007/s00284-018-1575-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/26/2018] [Indexed: 10/28/2022]
Abstract
Copper mining caused severe damage to the ecological environment of mining areas. The combination of microbe and plant remediation has an application potential in improving the absorption and transformation efficiency of heavy metals. The phyllosphere is the largest biointerface on the planet, and bacteria are the dominant microbial inhabitants of the phyllosphere, believed to be critical to plant growth and health. This study investigated the phyllospheric and soil bacteria communities using high-throughput sequencing, and endophyte infection statuses of four natural grasses by toluidine blue heparin assay. Results showed variation in phyllospheric bacterial community structure. Gammaproteobacteria were the most abundant bacterial population. Bacilli were found in the phyllosphere of Bothriochloa ischaemum and Imperata cylindrica, while Clostridia were only found in Calamagrostis epigejos. Alphaproteobacteria were the dominant bacteria in soil. In addition, bacterial communities were influenced by endophytic infection statuses. Oxalobacteraceae was associated with soil carbon and sulfur. Enterobacteriaceae had negative correlation with the ratio of soil carbon and nitrogen, and had positive correlation with Cd content. These results offer useful insights into phyllospheric bacterial community variance in four different natural grasses in a copper tailings dam.
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Affiliation(s)
- Tong Jia
- Institute of Loess Plateau, Shanxi University, Taiyuan, 030006, Shanxi, China.
| | - Rui-Hong Wang
- Institute of Loess Plateau, Shanxi University, Taiyuan, 030006, Shanxi, China
| | - Bao-Feng Chai
- Institute of Loess Plateau, Shanxi University, Taiyuan, 030006, Shanxi, China
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12
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Alborzi S, Bastarrachea LJ, Ding Q, Tikekar RV. Inactivation of Escherichia Coli O157:H7 and Listeria Innocua by Benzoic Acid, Ethylenediaminetetraacetic Acid and Their Combination in Model Wash Water and Simulated Spinach Washing. J Food Sci 2018; 83:1032-1040. [PMID: 29488632 DOI: 10.1111/1750-3841.14077] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/09/2018] [Accepted: 01/15/2018] [Indexed: 11/27/2022]
Abstract
An antimicrobial effect of benzoic acid (BA) and ethylenediaminetetraacetic acid (EDTA) was evaluated as a potential antimicrobial treatment against Escherichia coli O157:H7 and Listeria innocua. A 30 min exposure to the combination of 15 mM BA and 1 mM EDTA at 22 °C resulted in approximately 3 logarithmic reductions in stationary phase E. coli O157:H7. Logarithmic phase E. coli O157:H7 was more sensitive (P < 0.05) to the treatment and 1 mM EDTA alone caused more than 5 logarithmic reductions. L. innocua was also sensitive to a treatment with 15 mM BA alone, which induced 5 logarithmic reductions. By increasing the temperature of the solution containing 15 mM BA and 1 mM EDTA to 40 °C, more than 5 logarithmic reductions in stationary phase E. coli O157:H7 was observed after 5 min of treatment. However, the antimicrobial effect was attenuated (reaching less than 1 logarithmic reductions) at 4 °C. In addition, the combined BA and EDTA treatment retained its antimicrobial effect against E. coli O157:H7 for at least 6 cycles of treatment over 6 days at room temperature (22 °C). In a simulated spinach washing study, 15 mM BA and 1 mM EDTA together were able to prevent cross-contamination of E. coli O157:H7. The results highlight the potential use of combination of BA (15 mM) and EDTA (1 mM) to address microbial risk from E. coli O157:H7 and L. innocua in fresh produce industry. PRACTICAL APPLICATION This study demonstrates the effectiveness of benzoic acid (BA) and EDTA mixture in inactivating bacteria in the water used for produce washing and reducing the incidence of cross-contamination during washing of fresh produce. Use of BA + EDTA mixture has significant benefits such as: (a) ability to be reused, (b) effectiveness in the presence of organic matter, and (c) reduced need of monitoring wash water conditions such as pH, concentration and organic matter.
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Affiliation(s)
- Solmaz Alborzi
- Dept. of Nutrition and Food Science, Univ. of Maryland, College Park, MD 20742, U.S.A
| | - Luis J Bastarrachea
- Dept. of Nutrition, Dietetics, and Food Sciences, Utah State Univ., Logan, UT 84322, U.S.A
| | - Qiao Ding
- Dept. of Nutrition and Food Science, Univ. of Maryland, College Park, MD 20742, U.S.A
| | - Rohan V Tikekar
- Dept. of Nutrition and Food Science, Univ. of Maryland, College Park, MD 20742, U.S.A
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13
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Lymperopoulou DS, Adams RI, Lindow SE. Contribution of Vegetation to the Microbial Composition of Nearby Outdoor Air. Appl Environ Microbiol 2016; 82:3822-33. [PMID: 27107117 PMCID: PMC4907200 DOI: 10.1128/aem.00610-16] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 04/12/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Given that epiphytic microbes are often found in large population sizes on plants, we tested the hypothesis that plants are quantitatively important local sources of airborne microorganisms. The abundance of microbial communities, determined by quantifying bacterial 16S RNA genes and the fungal internal transcribed spacer (ITS) region, in air collected directly above vegetation was 2- to 10-fold higher than that in air collected simultaneously in an adjacent nonvegetated area 50 m upwind. Nonmetric multidimensional scaling revealed that the composition of airborne bacteria in upwind air samples grouped separately from that of downwind air samples, while communities on plants and downwind air could not be distinguished. In contrast, fungal taxa in air samples were more similar to each other than to the fungal epiphytes. A source-tracking algorithm revealed that up to 50% of airborne bacteria in downwind air samples were presumably of local plant origin. The difference in the proportional abundances of a given operational taxonomic unit (OTU) between downwind and upwind air when regressed against the proportional representation of this OTU on the plant yielded a positive slope for both bacteria and fungi, indicating that those taxa that were most abundant on plants proportionally contributed more to downwind air. Epiphytic fungi were less of a determinant of the microbiological distinctiveness of downwind air and upwind air than epiphytic bacteria. Emigration of epiphytic bacteria and, to a lesser extent, fungi, from plants can thus influence the microbial composition of nearby air, a finding that has important implications for surrounding ecosystems, including the built environment into which outdoor air can penetrate. IMPORTANCE This paper addresses the poorly understood role of bacterial and fungal epiphytes, the inhabitants of the aboveground plant parts, in the composition of airborne microbes in outdoor air. It is widely held that epiphytes contribute to atmospheric microbial assemblages, but much of what we know is limited to qualitative assessments. Elucidating the sources of microbes in outdoor air can inform basic biological processes seen in airborne communities (e.g., dispersal and biogeographical patterns). Furthermore, given the considerable contribution of outdoor air to microbial communities found within indoor environments, the understanding of plants as sources of airborne microbes in outdoor air might contribute to our understanding of indoor air quality. With an experimental design developed to minimize the likelihood of other-than-local plant sources contributing to the composition of airborne microbes, we provide direct evidence that plants are quantitatively important local sources of airborne microorganisms, with implications for the surrounding ecosystems.
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MESH Headings
- Air Microbiology
- Bacteria/classification
- Bacteria/genetics
- Bacteria/isolation & purification
- Cluster Analysis
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Fungal/chemistry
- DNA, Fungal/genetics
- DNA, Ribosomal/chemistry
- DNA, Ribosomal/genetics
- DNA, Ribosomal Spacer/chemistry
- DNA, Ribosomal Spacer/genetics
- Fungi/classification
- Fungi/genetics
- Fungi/isolation & purification
- Phylogeny
- Plants/microbiology
- RNA, Ribosomal, 16S/genetics
- Sequence Analysis, DNA
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Affiliation(s)
- Despoina S Lymperopoulou
- Department of Plant & Microbial Biology, University of California, Berkeley, California, USAUniversity of Tennessee and Oak Ridge National Laboratory
| | - Rachel I Adams
- Department of Plant & Microbial Biology, University of California, Berkeley, California, USAUniversity of Tennessee and Oak Ridge National Laboratory
| | - Steven E Lindow
- Department of Plant & Microbial Biology, University of California, Berkeley, California, USAUniversity of Tennessee and Oak Ridge National Laboratory
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Moderate halophilic bacteria colonizing the phylloplane of halophytes of the subfamily Salicornioideae (Amaranthaceae). Syst Appl Microbiol 2015; 38:406-16. [DOI: 10.1016/j.syapm.2015.05.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 05/25/2015] [Accepted: 05/27/2015] [Indexed: 11/30/2022]
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15
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Pérez-Velázquez J, Schlicht R, Dulla G, Hense BA, Kuttler C, Lindow SE. Stochastic modeling of Pseudomonas syringae growth in the phyllosphere. Math Biosci 2012; 239:106-16. [PMID: 22659411 DOI: 10.1016/j.mbs.2012.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 04/20/2012] [Accepted: 04/30/2012] [Indexed: 11/25/2022]
Abstract
Pseudomonas syringae is a gram-negative bacterium which lives on leaf surfaces. Its growth has been described using epifluorescence microscopy and image analysis; it was found to be growing in aggregates of a wide range of sizes. We develop a stochastic model to describe aggregate distribution and determine the mechanisms generating experimental observations. We found that a logistic birth-death model with migration (time-homogeneous Markov process) provides the best description of the observed data. We discuss how to analyze the joint distribution of the numbers of aggregates of different sizes at a given time and explore how to account for new aggregates being created, that is, the joint distribution of the family size statistics conditional on the total number of aggregates. We compute the first two moments. Through simulations we examine how the model's parameters affect the aggregate size distribution and successfully explain the quantitative experimental data available. Aggregation formation is thought to be the first step towards pathogenic behavior of this bacterium; understanding aggregate size distribution would prove useful to understand the switch from epiphytic to pathogenic behavior.
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Affiliation(s)
- J Pérez-Velázquez
- Institute of Biomathematics and Biometry, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
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16
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Kim M, Singh D, Lai-Hoe A, Go R, Abdul Rahim R, Ainuddin AN, Chun J, Adams JM. Distinctive phyllosphere bacterial communities in tropical trees. MICROBIAL ECOLOGY 2012; 63:674-681. [PMID: 21990015 DOI: 10.1007/s00248-011-9953-1] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 09/23/2011] [Indexed: 05/27/2023]
Abstract
Recent work has suggested that in temperate and subtropical trees, leaf surface bacterial communities are distinctive to each individual tree species and dominated by Alpha- and Gammaproteobacteria. In order to understand how general this pattern is, we studied the phyllosphere bacterial community on leaves of six species of tropical trees at a rainforest arboretum in Malaysia. This represents the first detailed study of 'true' tropical lowland tree phyllosphere communities. Leaf surface DNA was extracted and pyrosequenced targeting the V1-V3 region of 16S rRNA gene. As was previously found in temperate and subtropical trees, each tree species had a distinctive bacterial community on its leaves, clustering separately from other tree species in an ordination analysis. Bacterial communities in the phyllosphere were unique to plant leaves in that very few operational taxonomic units (0.5%) co-occurred in the surrounding soil environment. A novel and distinctive aspect of tropical phyllosphere communities is that Acidobacteria were one of the most abundant phyla across all samples (on average, 17%), a pattern not previously recognized. Sequences belonging to Acidobacteria were classified into subgroups 1-6 among known 24 subdivisions, and subgroup 1 (84%) was the most abundant group, followed by subgroup 3 (15%). The high abundance of Acidobacteria on leaves of tropical trees indicates that there is a strong relationship between host plants and Acidobacteria in tropical rain forest, which needs to be investigated further. The similarity of phyllosphere bacterial communities amongst the tree species sampled shows a significant tendency to follow host plant phylogeny, with more similar communities on more closely related hosts.
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Affiliation(s)
- Mincheol Kim
- School of Biological Sciences, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-747, Republic of Korea
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17
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Wellner S, Lodders N, Kämpfer P. Diversity and biogeography of selected phyllosphere bacteria with special emphasis on Methylobacterium spp. Syst Appl Microbiol 2011; 34:621-30. [PMID: 22000032 DOI: 10.1016/j.syapm.2011.08.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/17/2011] [Accepted: 08/23/2011] [Indexed: 11/26/2022]
Abstract
On the basis of cultivation-dependent (isolation on mineral salt medium supplemented with 0.5% methanol) and -independent (DGGE analysis) methods, we investigated the influence of the host plant species Trifolium repens and Cerastium holosteoides, three geographic locations and the land-use types meadow, mown pasture and pasture on the abundance and community composition of selected phyllosphere bacteria with emphasis on Methylobacterium species. Methylobacterium abundance was significantly higher on leaves of T. repens (mean value 2.0×10(7) CFU PPFM per g leaf) than on leaves of C. holosteoides (mean value 2.0×10(6) CFU per g leaf). Leaves from the sampling site Schorfheide-Chorin showed slightly lower Methylobacterium numbers than leaves of the other sampling sites. Land-use and sampling period had no consistent influence on Methylobacterium community size. Methylobacterium community composition was very similar over both sampling periods, all three sampling sites, all land-use types and both plant species. Moreover, no relationship between geographic and genetic distance was observed. Community composition of selected Proteobacteria was influenced by plant species, geographic location and land-use. Often, differences in community composition could be observed between meadows, mown pastures and pastures but not between different kinds of meadows (cutted once versus three times) and mown pastures (fertilized versus non-fertilized). The results also indicate, that whether there are differences between land-use types or not strongly depends on the investigated host plant species and ecosystem. Besides Methylobacterium, representatives of Methylophilus were detected. The results indicate that Methylobacterium species are generally abundant and stable members of the phyllosphere community whereas other genera occur more occasionally, and that Methylobacterium clearly dominates the methylotrophic phyllosphere community.
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Affiliation(s)
- S Wellner
- Institut für Angewandte Mikrobiologie, Justus-Liebig-Universität Giessen, D-35392 Giessen, Germany
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18
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Maksimova IA, Yurkov AM, Chernov IY. Spatial structure of epiphytic yeast communities on fruits of Sorbus aucuparia L. BIOL BULL+ 2009. [DOI: 10.1134/s1062359009060107] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Whipps J, Hand P, Pink D, Bending G. Phyllosphere microbiology with special reference to diversity and plant genotype. J Appl Microbiol 2008; 105:1744-55. [DOI: 10.1111/j.1365-2672.2008.03906.x] [Citation(s) in RCA: 332] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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20
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Jones SE, Newton RJ, McMahon KD. Potential for atmospheric deposition of bacteria to influence bacterioplankton communities. FEMS Microbiol Ecol 2008; 64:388-94. [PMID: 18393990 DOI: 10.1111/j.1574-6941.2008.00476.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Biogeographic patterns in microbial communities are an exciting but controversial topic in microbial ecology. Advances in theory pertaining to assembly of microbial communities have made strong assumptions about dispersal of bacteria without exploration. For this reason, we investigated rates of atmospheric bacterial deposition and compared the taxonomic composition of bacteria in rain with that of common freshwater bacterial communities. Our findings suggest that it is not appropriate to take for granted that atmospheric deposition of bacteria is a significant vector of immigration to freshwater ecosystems.
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Affiliation(s)
- Stuart E Jones
- Limnology and Marine Sciences Program, University of Wisconsin-Madison, Madison, WI, USA
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Maduell P, Armengol G, Llagostera M, Orduz S, Lindow S. B. thuringiensis is a poor colonist of leaf surfaces. MICROBIAL ECOLOGY 2008; 55:212-9. [PMID: 17587074 DOI: 10.1007/s00248-007-9268-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2006] [Accepted: 02/13/2007] [Indexed: 05/15/2023]
Abstract
The ability of several Bacillus thuringiensis strains to colonize plant surfaces was assessed and compared with that of more common epiphytic bacteria. While all B. thuringiensis strains multiplied to some extent after inoculation on bean plants, their maximum epiphytic population sizes of 10(6) cfu/g of leaf were always much less than that achieved by other resident epiphytic bacteria or an epiphytically fit Pseudomonas fluorescens strain, which attained population sizes of about 10(7) cfu/g of leaf. However B. thuringiensis strains exhibited much less decline in culturable populations upon imposition of desiccation stress than did other resident bacteria or an inoculated P. fluorescens strain, and most cells were in a spore form soon after inoculation onto plants. B. thuringiensis strains produced commercially for insect control were not less epiphytically fit than strains recently isolated from leaf surfaces. The growth of B. thuringiensis was not affected by the presence of Pseudomonas syringae when co-inoculated, and vice versa. B. thuringiensis strains harboring a green fluorescent protein marker gene did not form large cell aggregates, were not associated with other epiphytic bacteria, and were not found associated with leaf structures, such as stomata, trichomes, or veins when directly observed on bean leaves by epifluorescent microscopy. Thus, B. thuringiensis appears unable to grow extensively on leaves and its common isolation from plants may reflect immigration from more abundant reservoirs elsewhere.
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Affiliation(s)
- Pau Maduell
- Biotechnology and Biological Control Unit, Corporación para Investigaciones Biológicas, Medellín, Colombia
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Maduell P, Armengol G, Llagostera M, Lindow S, Orduz S. Immigration of Bacillus thuringiensis to bean leaves from soil inoculum or distal plant parts. J Appl Microbiol 2007; 103:2593-600. [DOI: 10.1111/j.1365-2672.2007.03509.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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23
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Brandl MT. Fitness of human enteric pathogens on plants and implications for food safety. ANNUAL REVIEW OF PHYTOPATHOLOGY 2006; 44:367-92. [PMID: 16704355 DOI: 10.1146/annurev.phyto.44.070505.143359] [Citation(s) in RCA: 342] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The continuous rise in the number of outbreaks of foodborne illness linked to fresh fruit and vegetables challenges the notion that enteric pathogens are defined mostly by their ability to colonize the intestinal habitat. This review describes the epidemiology of produce-associated outbreaks of foodborne disease and presents recently acquired knowledge about the behavior of enteric pathogens on plants, with an emphasis on Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes. The growth and survival of enteric pathogens on plants are discussed in the light of knowledge and concepts in plant microbial ecology, including epiphytic fitness, the physicochemical nature of plant surfaces, biofilm formation, and microbe-microbe and plant-microbe interactions. Information regarding the various stresses that affect the survival of enteric pathogens and the molecular events that underlie their interactions in the plant environment provides a good foundation for assessing their role in the infectious dose of the pathogens when contaminated fresh produce is the vehicle of illness.
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Affiliation(s)
- Maria T Brandl
- Produce Safety and Microbiology Research Unit, Agricultural Research Services, U.S. Department of Agriculture, Albany, California 94710, USA.
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Upper CD, Hirano SS, Dodd KK, Clayton MK. Factors that Affect Spread of Pseudomonas syringae in the Phyllosphere. PHYTOPATHOLOGY 2003; 93:1082-1092. [PMID: 18944091 DOI: 10.1094/phyto.2003.93.9.1082] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Successful spread of an organism to a new habitat requires both immigration to and growth on that habitat. Field experiments were conducted to determine the relative roles of dispersal (i.e., immigration) and bacterial multiplication in spread of Pseudomonas syringae pv. syringae in the phyllosphere. To study spread, individual plots consisted of three nested concentric squares with the inner 6 m(2) planted to snap beans serving as the sink. Each sink, in turn, was surrounded by a barrier zone, usually 6 m wide, which was surrounded by a 6-m-wide source area. The source areas were planted with snap bean seeds inoculated with doubly marked strains derived from wild-type P. syringae pv. syringae B728a. The treatments were designed to test the effects of the nature and width of the barrier zone and suitability of the habitat in the sinks on spread of P. syringae pv. syringae. The marked strains introduced into the source areas at the time of planting were consistently detected in sink areas within a day or two after emergence of bean seedlings in the sources as assessed by leaf imprinting and dilution plating. The amounts of spread (population sizes of the marked strain in sinks) across barrier zones planted to snap bean (a suitable habitat for growth of P. syringae pv. syringae), soybean (not a favorable habitat for P. syringae pv. syringae), and bare ground were not significantly different. Thus, the nature of the barrier had no measurable effect on spread. Similarly, spread across bare-ground barriers 20 m wide was not significantly different from that across barriers 6 m wide, indicating that distance on this scale was not a major factor in determining the amount of spread. The suitability of the sink for colonization by P. syringae pv. syringae had a measurable effect on spread. Spread to sinks planted to clean seed was greater than that to sinks planted with bean seeds inoculated with a slurry of pulverized brown spot diseased bean leaves, sinks planted 3 weeks before sources, and sinks planted to a snap bean cultivar that does not support large numbers of P. syringae pv. syringae. Based of these results, we conclude that the small amount of dispersal that occurred on the scale studied was sufficient to support extensive spread, and suitability of the habitat for multiplication of P. syringae pv. syringae strongly influenced the amount of spread.
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Gagnevin L, Pruvost O. Epidemiology and Control of Mango Bacterial Black Spot. PLANT DISEASE 2001; 85:928-935. [PMID: 30823104 DOI: 10.1094/pdis.2001.85.9.928] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
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Jurkevitch EJ, Shapira G. Structure and Colonization Dynamics of Epiphytic Bacterial Communities and of Selected Component Strains on Tomato (Lycopersicon esculentum) Leaves. MICROBIAL ECOLOGY 2000; 40:300-308. [PMID: 12035088 DOI: 10.1007/s002480000023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/1999] [Accepted: 01/06/2000] [Indexed: 05/23/2023]
Abstract
The sizes and compositions of bacterial populations found on leaves of greenhouse and field grown tomato plants were studied by dilution plating, fatty acid methyl ester analysis (FAME), and BIOLOG plates of isolates in pure cultures. In the greenhouse, overhead-irrigated plants sustained higher microbial populations (up to 105 cfu g-1) than soil-irrigated plants (103 cfu g-1). Strains isolated from overhead-irrigated plants grown in a vegetable garden (n = 216) and from greenhouse-grown plants (n = 114) were subjected to FAME analysis. Similarly, strains from soil-irrigated field-grown plants (n = 83) were identified using BIOLOG plates. In each case, populations were dominated by a few genera. When concentrated phyllosphere washes (CPW) were sprayed on greenhouse-grown, soil-irrigated plants, leaf bacterial populations of more than 105 CFU g-1 were sustained for 4 days; sterile buffer-sprayed leaves sustained less than 104 CFU g-1. No significant enrichment of any strain isolated from the sprayed leaves could be detected by FAME identification of randomly selected colonies. However, when recurring leaf saprophytic species (both Gram-positive and Gram-negative) isolated from these experiments and from plants grown outdoors were tested for epiphytic colonization under stressful conditions, all could still be detected at various levels up to 4 days after inoculation, indicating differential epiphytic fitness. The non-epiphytic bacteria Escherichia coli and Azospirillum brasilense disappeared from the leaf surface within the same experimental period.
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Affiliation(s)
- Edouard J. Jurkevitch
- Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O.B. 12, Rehovot 76100, Israel
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Andrews JH, Harris RF. The Ecology and Biogeography of Microorganisms on Plant Surfaces. ANNUAL REVIEW OF PHYTOPATHOLOGY 2000; 38:145-180. [PMID: 11701840 DOI: 10.1146/annurev.phyto.38.1.145] [Citation(s) in RCA: 295] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The vast surface of the plant axis, stretching from root tips occasionally buried deeply in anoxic sediment, to apical meristems held far aloft, provides an extraordinarily diverse habitat for microorganisms. Each zone has to a greater or lesser extent its own cohort of microorganisms, in aggregate comprising representatives from all three primary domains of life-Bacteria, Archaea, and Eucarya. While the plant sets the stage for its microbial inhabitants, they, in turn, have established varied relationships with their large partner. These associations range from relatively inconsequential (transient epiphytic saprophytes) to substantial (epiphytic commensals, mutualistic symbionts, endophytes, or pathogens). Through recent technological breakthroughs, a much better perspective is beginning to emerge on the nature of these relationships, but still relatively little is known about the role of epiphytic microbial associations in the life of the plant.
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Affiliation(s)
- John H Andrews
- Department of Plant Pathology and 2Department of Soil Science, University of Wisconsin, Madison, Wisconsin 53706-1598; e-mail: ,
| | - Robin F Harris
- Department of Plant Pathology and 2Department of Soil Science, University of Wisconsin, Madison, Wisconsin 53706-1598; e-mail: ,
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Hirano SS, Upper CD. Bacteria in the leaf ecosystem with emphasis on Pseudomonas syringae-a pathogen, ice nucleus, and epiphyte. Microbiol Mol Biol Rev 2000; 64:624-53. [PMID: 10974129 PMCID: PMC99007 DOI: 10.1128/mmbr.64.3.624-653.2000] [Citation(s) in RCA: 477] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The extremely large number of leaves produced by terrestrial and aquatic plants provide habitats for colonization by a diversity of microorganisms. This review focuses on the bacterial component of leaf microbial communities, with emphasis on Pseudomonas syringae-a species that participates in leaf ecosystems as a pathogen, ice nucleus, and epiphyte. Among the diversity of bacteria that colonize leaves, none has received wider attention than P. syringae, as it gained notoriety for being the first recombinant organism (Ice(-) P. syringae) to be deliberately introduced into the environment. We focus on P. syringae to illustrate the attractiveness and somewhat unique opportunities provided by leaf ecosystems for addressing fundamental questions of microbial population dynamics and mechanisms of plant-bacterium interactions. Leaf ecosystems are dynamic and ephemeral. The physical environment surrounding phyllosphere microbes changes continuously with daily cycles in temperature, radiation, relative humidity, wind velocity, and leaf wetness. Slightly longer-term changes occur as weather systems pass. Seasonal climatic changes impose still a longer cycle. The physical and physiological characteristics of leaves change as they expand, mature, and senesce and as host phenology changes. Many of these factors influence the development of populations of P. syringae upon populations of leaves. P. syringae was first studied for its ability to cause disease on plants. However, disease causation is but one aspect of its life strategy. The bacterium can be found in association with healthy leaves, growing and surviving for many generations on the surfaces of leaves as an epiphyte. A number of genes and traits have been identified that contribute to the fitness of P. syringae in the phyllosphere. While still in their infancy, such research efforts demonstrate that the P. syringae-leaf ecosystem is a particularly attractive system with which to bridge the gap between what is known about the molecular biology of genes linked to pathogenicity and the ecology and epidemiology of associated diseases as they occur in natural settings, the field.
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Affiliation(s)
- S S Hirano
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Mercier J, Lindow SE. Role of leaf surface sugars in colonization of plants by bacterial epiphytes. Appl Environ Microbiol 2000; 66:369-74. [PMID: 10618250 PMCID: PMC91832 DOI: 10.1128/aem.66.1.369-374.2000] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The relationship between nutrients leached onto the leaf surface and the colonization of plants by bacteria was studied by measuring both the abundance of simple sugars and the growth of Pseudomonas fluorescens on individual bean leaves. Data obtained in this study indicate that the population size of epiphytic bacteria on plants under environmentally favorable conditions is limited by the abundance of carbon sources on the leaf surface. Sugars were depleted during the course of bacterial colonization of the leaf surface. However, about 20% of readily utilizable sugar, such as glucose, present initially remained on fully colonized leaves. The amounts of sugars on a population of apparently identical individual bean leaves before and after microbial colonization exhibited a similar right-hand-skewed distribution and varied by about 25-fold from leaf to leaf. Total bacterial population sizes on inoculated leaves under conditions favorable for bacterial growth also varied by about 29-fold and exhibited a right-hand-skewed distribution. The amounts of sugars on leaves of different plant species were directly correlated with the maximum bacterial population sizes that could be attained on those species. The capacity of bacteria to deplete leaf surface sugars varied greatly among plant species. Plants capable of supporting high bacterial population sizes were proportionally more depleted of leaf surface nutrients than plants with low epiphytic populations. Even in species with a high epiphytic bacterial population, a substantial amount of sugar remained after bacterial colonization. It is hypothesized that residual sugars on colonized leaves may not be physically accessible to the bacteria due to limitations in wettability and/or diffusion of nutrients across the leaf surface.
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Affiliation(s)
- J Mercier
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA.
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Watanabe K, Hara W, Sato M. Evidence for growth of strains of the plant epiphytic bacterium Erwinia herbicola and transconjugation among the bacterial strains in guts of the silkworm Bombyx mori. J Invertebr Pathol 1998; 72:104-11. [PMID: 9709009 DOI: 10.1006/jipa.1998.4764] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Growth of plant epiphytic bacteria Erwinia herbicola and Pseudomonas syringae in guts of the silkworm, Bombyx mori, was studied. Fifth instar silkworm larvae were fed artificial diets supplemented with these bacteria for 6 to 12 h followed by uncontaminated diets. At 1, 3, and 6 days after feeding, bacteria were isolated from insect guts and feces. A much larger population of E. herbicola was detected in the samples collected 3 and 6 days after the inoculation than in samples collected after 1 day, indicating that these bacteria grew in the insect gut, while P. syringae was unable to survive. Transconjugation between E. herbicola strains in the insect gut was also examined. First, either a donor or a recipient strain was fed to the insects in artificial diets containing the bacteria during 12 h, and then pairing strains were fed during 12 h after starvation for 12 h. The conjugative plasmid pBPW1::Tn7 was transferred into recipient cells at very high frequencies (10(-1)/recipient after 3 days and 10(-3) after 6 days) in insect guts. Indigenous plasmids of E. herbicola mobilized RSF1010 plasmid into recipient cells at frequencies of 10(-4) in insect guts. These transconjugants were detected in the feces of the insects. Thus, plasmid-mediated gene transfer among the epiphytic bacteria in insect guts was demonstrated. The results obtained suggest that in insecta gene transfer may play an important role in the evolution of plant epiphytic bacteria.
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Affiliation(s)
- K Watanabe
- National Institute of Sericultural and Entomological Science, Tsukuba, Ibaraki, 305, Japan
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Abstract
Microbial population dynamics on leaves in time and space are a function of immigration, emigration, growth, and death. Insight into the relative significance of each population process to the generation of specific dynamics for individual microorganisms is necessary to understanding the ecology and life history strategy of the microorganism and to developing effective control strategies. Additionally, information on the significance of within-leaf versus extra-leaf processes to the generation of phyllosphere dynamics is important to determining the range of spatial scales over which a population should be studied. Unfortunately, such information is difficult to obtain due to the lack of effective methodologies for distinguishing these processes within phyllosphere populations. Future research efforts should focus on the quantification of immigration, emigration, growth, and death relative to the population dynamics of phyllosphere microorganisms.
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Affiliation(s)
- L L Kinkel
- Department of Plant Pathology, University of Minnesota, Saint Paul, Minnesota 55108, USA.
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