Interrelationships of Food Safety and Plant Pathology: The Life Cycle of Human Pathogens on Plants

Barak, Jeri D.; Schroeder, Brenda K.

doi:10.1146/annurev-phyto-081211-172936

Cited by 112 publications

(98 citation statements)

References 162 publications

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“…Early colonization facilitates microbial establishment and persistence in this niche and has human health implications. Colonization of the spermosphere and rhizosphere can lead to contamination of the entire plant (41)(42)(43), and attached S. enterica bacteria cannot be removed from crop surfaces, which are then consumed raw by humans (12).…”

Section: Discussionmentioning

confidence: 99%

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De Novo Amino Acid Biosynthesis Contributes to Salmonella enterica Growth in Alfalfa Seedling Exudates

Kwan

Pisithkul

Amador‐Noguez

et al. 2015

Appl Environ Microbiol

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Salmonella enterica is a member of the plant microbiome. Growth of S. enterica in sprouting-seed exudates is rapid; however, the active metabolic networks essential in this environment are unknown. To examine the metabolic requirements of S. enterica during growth in sprouting-seed exudates, we inoculated alfalfa seeds and identified 305 S. enterica proteins extracted 24 h postinoculation from planktonic cells. Over half the proteins had known metabolic functions, and they are involved in over onequarter of the known metabolic reactions. Ion and metabolite transport accounted for the majority of detected reactions. Proteins involved in amino acid transport and metabolism were highly represented, suggesting that amino acid metabolic networks may be important for S. enterica growth in association with roots. Amino acid auxotroph growth phenotypes agreed with the proteomic data; auxotrophs in amino acid-biosynthetic pathways that were detected in our screen developed growth defects by 48 h. When the perceived sufficiency of each amino acid was expressed as a ratio of the calculated biomass requirement to the available concentration and compared to growth of each amino acid auxotroph, a correlation between nutrient availability and bacterial growth was found. Furthermore, glutamate transport acted as a fitness factor during S. enterica growth in association with roots. Collectively, these data suggest that S. enterica metabolism is robust in the germinating-alfalfa environment; that single-amino-acid metabolic pathways are important but not essential; and that targeting central metabolic networks, rather than dedicated pathways, may be necessary to achieve dramatic impacts on bacterial growth. P lants can influence both the number and species of bacteria that colonize their surfaces. The availability and types of nutrients, secretion of chemoattractants or repellents, and production of antimicrobial compounds all impact the composition of the plant-associated bacterial community. In particular, germinating seeds and roots release exudates containing complex mixtures of amino acids, sugars, organic acids, and other plant metabolites that support the growth of microbial colonists in the spermosphere and rhizosphere (1-5). Successful colonization of and persistence in these plant niches requires that bacteria acquire and metabolize these plant-derived nutrients and biosynthesize any required metabolites not sufficiently available from the plant.The compositions of seed and root exudates are dynamic and vary based on seed and plant age, soil type, temperature, nutritional status, and crop (6, 7). The identity and quantity of nutrients in plant exudates have a profound impact on bacterial growth and metabolic activity (8). Seeds that released larger quantities of carbohydrates and amino acids supported higher Enterobacter cloacae populations, rates of bacterial growth, and metabolic activity (3,4,8). Nutrient identity (e.g., alanine, arginine, and aspartate), not just type (e.g., amino acids, sugars, and lipids), influen...

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Section: Discussionmentioning

confidence: 99%

“…Salmonella enterica is an enteric human pathogen that colonizes crop plants as secondary hosts (12). S. enterica has been isolated from the seeds, leaves, and fruit of a variety of fresh produce crops (13) and is the leading bacterial cause of food-borne illness linked to fresh produce consumption (14).…”

mentioning

confidence: 99%

De Novo Amino Acid Biosynthesis Contributes to Salmonella enterica Growth in Alfalfa Seedling Exudates

Kwan

Pisithkul

Amador‐Noguez

et al. 2015

Appl Environ Microbiol

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“…Therefore, there is a great interest in understanding the interaction between Salmonella and plants. The role of plants in the life cycle of Salmonella and the ability of these bacteria to use plants as alternative hosts to human and other animals have been recently reviewed [164,165]. Salmonella usually enters agricultural environments via animal feces.…”

Section: Salmonella In Plantsmentioning

confidence: 99%

Impact ofSalmonella entericaType III Secretion System Effectors on the Eukaryotic Host Cell

Ramos‐Morales

2012

ISRN Cell Biology

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Type III secretion systems are molecular machines used by many Gram-negative bacterial pathogens to inject proteins, known as effectors, directly into eukaryotic host cells. These proteins manipulate host signal transduction pathways and cellular processes to the pathogen's advantage. Salmonella enterica possesses two virulence-related type III secretion systems that deliver more than forty effectors. This paper reviews our current knowledge about the functions, biochemical activities, host targets, and impact on host cells of these effectors. First, the concerted action of effectors at the cellular level in relevant aspects of the interaction between Salmonella and its hosts is analyzed. Then, particular issues that will drive research in the field in the near future are discussed. Finally, detailed information about each individual effector is provided.

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“…Even though some studies demonstrated that Salmonella involves its virulence genes in the interactions with plants, and that under some conditions it can elicit disease-like signs in plants (Schikora et al, 2011), it is not commonly considered a phytopathogen (Barak and Schroeder, 2012). Therefore, for the purpose of this article, we broadly define "susceptibility" of tomatoes as being conducive to proliferation of Salmonella following an infection into a shallow wound in the fruit epidermis.…”

Section: Resultsmentioning

confidence: 99%

Effects of nitrogen and potassium fertilization on the susceptibility of tomatoes to post-harvest proliferation of Salmonella enterica

Marvasi¹,

George²,

Giurcanu³

et al. 2014

Food Microbiology

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a b s t r a c tFresh fruits and vegetables are increasingly recognized as vehicles of salmonellosis. Pre-and post-harvest environmental conditions, and physiological, and genetic factors are thought to contribute to the ability of human pathogens to persist in the production environment, attach to, colonize and proliferate in and on raw produce. How field production conditions affect the post-harvest food safety outcomes is not entirely understood. This study tested how varying nitrogen and potassium fertilization levels affected the "susceptibility" of tomatoes to Salmonella infections following the harvest of fruits. Two tomato varieties grown over three seasons under high, medium, and low levels of nitrogen and potassium fertilization in two locations were inoculated with seven strains of Salmonella. Even though the main effects of nitrogen and potassium fertilization on the susceptibility of tomatoes to infections with Salmonella enterica were not statistically significant overall, differences in nitrogen concentrations in plant tissues correlated with the susceptibility of partially ripe tomatoes (cv. Solar Fire) to Salmonella. Tomato maturity and the season in which tomatoes were produced had the strongest effect on the ability of Salmonella to multiply in tomatoes. Tomato phenolics, accumulation of which is known to correlate with rates of the N fertilization, did not inhibit growth of Salmonella in vitro.

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Interrelationships of Food Safety and Plant Pathology: The Life Cycle of Human Pathogens on Plants

Cited by 112 publications

References 162 publications

De Novo Amino Acid Biosynthesis Contributes to Salmonella enterica Growth in Alfalfa Seedling Exudates

De Novo Amino Acid Biosynthesis Contributes to Salmonella enterica Growth in Alfalfa Seedling Exudates

Impact ofSalmonella entericaType III Secretion System Effectors on the Eukaryotic Host Cell

Effects of nitrogen and potassium fertilization on the susceptibility of tomatoes to post-harvest proliferation of Salmonella enterica

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