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Darlison J, Mogren L, Rosberg AK, Grudén M, Minet A, Liné C, Mieli M, Bengtsson T, Håkansson Å, Uhlig E, Becher PG, Karlsson M, Alsanius BW. Leaf mineral content govern microbial community structure in the phyllosphere of spinach (Spinacia oleracea) and rocket (Diplotaxis tenuifolia). THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 675:501-512. [PMID: 31030156 DOI: 10.1016/j.scitotenv.2019.04.254] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 06/09/2023]
Abstract
The plant microbiome is an important factor for plant health and productivity. While the impact of nitrogen (N) availability for plant growth and development is well established, its influence on the microbial phyllosphere community structure is unknown. We hypothesize that nitrogen impacts the growth and abundance of several microorganisms on the leaf surface. The bacterial and fungal communities of baby leaf spinach (Spinacia oleracea), and rocket (Diplotaxis tenuifolia) were investigated in a field trial for two years in a commercial setting. Nitrogen fertilizer was tested in four doses (basic nitrogen, basic + suboptimal, basic + commercial, basic + excess) with six replicates in each. Culture-independent (Illumina sequencing) and culture-dependent (viable count and identification of bacterial isolates) community studies were combined with monitoring of plant physiology and site weather conditions. This study found that alpha diversity of bacterial communities decreased in response to increasing nitrogen fertilizer dose, whereas viable counts showed no differences. Correspondingly, fungal communities of the spinach phyllosphere showed a decreasing pattern, whereas the decreasing diversity of fungal communities of rocket was not significant. Plant species and effects of annual variations on microbiome structure were observed for bacterial and fungal communities on both spinach and rocket. This study provides novel insights on the impact of nitrogen fertilizer regime on a nutrient scarce habitat, the phyllosphere.
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Affiliation(s)
- Julia Darlison
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden.
| | - Lars Mogren
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Anna Karin Rosberg
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Maria Grudén
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Antoine Minet
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Clarisse Liné
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Morgane Mieli
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Torbjörn Bengtsson
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Åsa Håkansson
- LTH Lund University, Department of Food Technology, Box 124, SE-221 00 Lund, Sweden
| | - Elisabeth Uhlig
- LTH Lund University, Department of Food Technology, Box 124, SE-221 00 Lund, Sweden
| | - Paul G Becher
- Swedish University of Agricultural Sciences, Department of Plant Protection Biology, PO Box 102, SE-230 53 Alnarp, Sweden
| | - Maria Karlsson
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
| | - Beatrix W Alsanius
- Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Microbial Horticulture Laboratory, PO Box 103, SE-230 53 Alnarp, Sweden
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Söderqvist K, Rosberg AK, Boqvist S, Alsanius B, Mogren L, Vågsholm I. Season and Species: Two Possible Hurdles for Reducing the Food Safety Risk of Escherichia coli O157 Contamination of Leafy Vegetables. J Food Prot 2019; 82:247-255. [PMID: 30681384 DOI: 10.4315/0362-028x.jfp-18-292] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The food safety risk of Shiga toxin-producing Escherichia coli (STEC) infection per serving of leafy vegetables was investigated using a quantitative microbial risk assessment (QMRA) approach. The estimated level of E. coli O157 contamination was based on observed numbers of Enterobacteriaceae and E. coli on leafy vegetables grown and processed in southern Sweden from 2014 to 2016. Samples were collected before harvest, after washing, and at the end of shelf life. The observed counts were combined with data on the ratio of E. coli to E. coli O157 taken from earlier studies to estimate the probability of illness. The risks of STEC infection associated with species, either spinach ( Spinacia oleracea) or rocket ( Diplotaxis tenuifolia), growing season (spring or autumn), and washing (washed or not washed) were then evaluated. The results indicated that leafy vegetable species and growing season could be possible hurdles for reducing the food safety risk of STEC infection. At harvest, the probability of infection was 87% lower when consuming rocket compared with spinach and 90% lower when consuming leafy vegetables grown in spring compared with autumn. These relative risk reductions remained consistent even with other serving sizes and dose-response models. The lowest risk of STEC infection was associated with leafy vegetables early in the production chain, i.e., before harvest, while the risk increased during storage and processing. Consequently, the highest risk was observed when leafy vegetables were consumed at the end of shelf life. Washing had no effect on the food safety risk of STEC infection in this study. To improve the quality of QMRA, there is a need for additional data on the relationship between indicator organisms that can be easily enumerated (e.g., E. coli and Enterobacteriaceae) and E. coli strains that can cause STEC infection (e.g., E. coli O157) but are difficult to identify in food samples such as leafy vegetables.
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Affiliation(s)
- Karin Söderqvist
- 1 Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7036, SE-750 07 Uppsala, Sweden (ORCID: http://orcid.org/0000-0002-1249-1949 [K.S.])
| | - Anna Karin Rosberg
- 2 Department of Biosystems and Technology, Microbial Horticulture Unit, P.O. Box 103, SE-230 53 Alnarp, Sweden
| | - Sofia Boqvist
- 1 Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7036, SE-750 07 Uppsala, Sweden (ORCID: http://orcid.org/0000-0002-1249-1949 [K.S.])
| | - Beatrix Alsanius
- 2 Department of Biosystems and Technology, Microbial Horticulture Unit, P.O. Box 103, SE-230 53 Alnarp, Sweden
| | - Lars Mogren
- 2 Department of Biosystems and Technology, Microbial Horticulture Unit, P.O. Box 103, SE-230 53 Alnarp, Sweden
| | - Ivar Vågsholm
- 1 Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7036, SE-750 07 Uppsala, Sweden (ORCID: http://orcid.org/0000-0002-1249-1949 [K.S.])
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