The Effect of Leaf Age and Position on the Dynamics of Microbial Populations on Aerial Plant Surfaces

Jacques, Marie‐Agnès

doi:10.1007/978-0-585-34164-4_15

Cited by 13 publications

(8 citation statements)

References 68 publications

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“…Numerous studies have demonstrated the role of leaf age in the composition and population size of epiphytic microbial communities (19). Gradients of decreasing densities of epiphytic bacteria from the outer to the inner leaves have been reported for rosette-type leafy vegetables at harvest (10,12,20,31).…”

Section: Discussionmentioning

confidence: 99%

Leaf Age as a Risk Factor in Contamination of Lettuce withEscherichia coliO157:H7 andSalmonella enterica

Brandl

Amundson

2008

Appl Environ Microbiol

194

113

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Outbreaks of Escherichia coli O157:H7 infections have been linked increasingly to leafy greens, particularly to lettuce. We present here the first evidence that this enteric pathogen can multiply on the leaves of romaine lettuce plants. The increases in population size of E. coli O157:H7 in the phyllosphere of young lettuce plants ranged from 16-to 100-fold under conditions of warm temperature and the presence of free water on the leaves and varied significantly with leaf age. The population size was consistently ca. 10-fold higher on the young (inner) leaves than on the middle leaves. The growth rates of Salmonella enterica and of the natural bacterial microflora were similarly leaf age dependent. Both enteric pathogens also achieved higher population sizes on young leaves than on middle leaves harvested from mature lettuce heads, suggesting that leaf age affects preharvest as well as postharvest colonization. Elemental analysis of the exudates collected from the surfaces of leaves of different ages revealed that young-leaf exudates were 2.9 and 1.5 times richer in total nitrogen and carbon, respectively, than middle-leaf exudates. This trend mirrored the nitrogen and carbon content of the leaf tissue. Application of ammonium nitrate, but not glucose, to middle leaves enhanced the growth of E. coli O157:H7 significantly, suggesting that low nitrogen limits its growth on these leaves. Our results indicate that leaf age and nitrogen content contribute to shaping the bacterial communities of preharvest and postharvest lettuce and that young lettuce leaves may be associated with a greater risk of contamination with E. coli O157:H7.

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Section: Discussionmentioning

confidence: 99%

Leaf Age as a Risk Factor in Contamination of Lettuce withEscherichia coliO157:H7 andSalmonella enterica

Brandl

Amundson

2008

Appl Environ Microbiol

194

113

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“…In addition, other parameters of the physical environment (temperature, relative humidity, etc.) and other factors such as community composition and abundance and interactions among all of the biotic and abiotic factors likely influence the numbers of P. syringae at any given time and on any given leaf (70,71,85,135,148,210,218,309,310). The system is dynamic and only slightly understood.…”

Section: To Grow or Not To Growmentioning

confidence: 99%

Bacteria in the Leaf Ecosystem with Emphasis onPseudomonas syringae—a Pathogen, Ice Nucleus, and Epiphyte

Hirano

Upper

2000

Microbiol Mol Biol Rev

826

610

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SUMMARY 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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“…phaseolicola and to P. savastanoi pv. savastanoi at any age of the plant (Jacques, 1996). It seems that among the highlighted abiotic factors, water plays a key role in symptom expression.…”

Section: Resultsmentioning

confidence: 99%

Population dynamics of Pseudomonas savastanoi pv. phaseolicola in bean, throughout the epiphytic and pathogenic phases

Marques

Samson

2016

Pesq. agropec. bras.

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-The objective of this work was to monitor traits of the life cycle of Pseudomonas savastanoi pv. phaseolicola, in order to better understand the outbreak of bean halo blight, originating from a bacterial population in asymptomatic plants. Five experiments were conducted in the field, in greenhouses, and in humidity chambers. Changes in population size were evaluated in three field plantings, by introducing the bacteria in contamination focal points and observing the weather conditions favoring an outbreak. The dispersion of the bacteria in the field was followed by isolation and Bio-PCR analysis. Two assays were conducted in greenhouses and humidity chambers to evaluate the effect of leaf age on disease expression and the relationship between population level and number of leaf spots. The bacteria multiply intensively when in contact with a compatible host and reach high population sizes, with or without symptoms. The most favorable factor for bacterial multiplication and symptom triggering was water, and its role in the changeover from the epiphytic to the pathogenic phase might be linked to rainfall volume and intensity. Bacterial asymptomatic dispersion in the field is greater than disease emergence. In Brazil, the bacteria should be categorized as a present quarantine pest.Index terms: Phaseolus vulgaris, Bio-PCR, epidemiology, halo blight, plant quarantine, weather conditions. Dinâmica populacional de Pseudomonas savastanoi pv. phaseolicola em feijoeiro, durante as fases epifítica e patogênicaResumo -O objetivo deste trabalho foi monitorar características do ciclo de vida de Pseudomonas savastanoi pv. phaseolicola, para melhor compreender a manifestação do crestamento aureolado do feijoeiro, originada de uma população bacteriana em plantas assintomáticas. Cinco experimentos foram conduzidos em campo, casas de vegetação e câmaras de cultura. Alterações no tamanho da população foram avaliadas em três plantios no campo, por meio da introdução da bactéria em focos de contaminação e da observação das condições climáticas que favoreceram a manifestação da doença. A dispersão da bactéria no campo foi acompanhada por isolamento e análise Bio-PCR. Dois ensaios foram conduzidos em casas de vegetação e câmaras de cultura, para avaliar o efeito da idade das folhas na expressão da doença e a relação entre o nível populacional e o número de manchas foliares. A bactéria multiplica-se intensamente logo que entra em contato com hospedeiro compatível e atinge níveis populacionais elevados, com a presença ou não de sintomas. O fator que mais favoreceu a multiplicação bacteriana e o surgimento dos sintomas foi a água, e seu papel na passagem da fase epifítica à patogênica pode estar associado ao volume e à intensidade das chuvas. A dispersão não sintomática da bactéria no campo é maior que o aparecimento da doença. No Brasil, a bactéria deve ser categorizada como praga quarentenária presente.Termos para indexação: Phaseolus vulgaris, Bio-PCR, epidemiologia, crestamento aureolado, quarentena vegetal, condições climáti...

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The Effect of Leaf Age and Position on the Dynamics of Microbial Populations on Aerial Plant Surfaces

Cited by 13 publications

References 68 publications

Leaf Age as a Risk Factor in Contamination of Lettuce withEscherichia coliO157:H7 andSalmonella enterica

Leaf Age as a Risk Factor in Contamination of Lettuce withEscherichia coliO157:H7 andSalmonella enterica

Bacteria in the Leaf Ecosystem with Emphasis onPseudomonas syringae—a Pathogen, Ice Nucleus, and Epiphyte

Population dynamics of Pseudomonas savastanoi pv. phaseolicola in bean, throughout the epiphytic and pathogenic phases

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