Phyllosphere Microbiota Composition and Microbial Community Transplantation on Lettuce Plants Grown Indoors

Abstract

The aerial surfaces of plants, or phyllosphere, are microbial habitats important to plant and human health. In order to accurately investigate microbial interactions in the phyllosphere under laboratory conditions, the composition of the phyllosphere microbiota should be representative of the diversity of microorganisms residing on plants in nature. We found that Romaine lettuce grown in the laboratory contained 10- to 100-fold lower numbers of bacteria than age-matched, field-grown lettuce. The bacterial diversity on laboratory-grown plants was also significantly lower and contained relatively higher proportions of Betaproteobacteria as opposed to the Gammaproteobacteria-enriched communities on field lettuce. Incubation of field-grown Romaine lettuce plants in environmental growth chambers for 2 weeks resulted in bacterial cell densities and taxa similar to those on plants in the field but with less diverse bacterial populations overall. In comparison, the inoculation of laboratory-grown Romaine lettuce plants with either freshly collected or cryopreserved microorganisms recovered from field lettuce resulted in the development of a field-like microbiota on the lettuce within 2 days of application. The survival of an inoculated strain of Escherichia coli O157:H7 was unchanged by microbial community transfer; however, the inoculation of E. coli O157:H7 onto those plants resulted in significant shifts in the abundance of certain taxa. This finding was strictly dependent on the presence of a field-associated as opposed to a laboratory-associated microbiota on the plants. Phyllosphere microbiota transplantation in the laboratory will be useful for elucidating microbial interactions on plants that are important to agriculture and microbial food safety.

Abiotic Stress and Phyllosphere Bacteria Influence the Survival of Human Norovirus and Its Surrogates on Preharvest Leafy Greens

“…However, no previous studies have explored whether phyllosphere bacteria have any role in the persistence of HuNoV on plants. In our study, the overall range of bacterial counts obtained on PID 0 (3.5 and 4.5 log 10 CFU/g for lettuce and spinach, respectively) was similar to previously reported ranges of culturable bacteria on plants cultivated under greenhouse conditions (62,63).…”

Bacterial Communities Associated with Surfaces of Leafy Greens: Shift in Composition and Decrease in Richness over Time

“…Further studies of air, soil, and water samples should be done to identify possible inoculum sources. It should be mentioned that all of our L. sativa samples were sown in a greenhouse and grown for 2 weeks before planting in the field, but previous studies have shown that L. sativa plants grown indoors have lower total bacterial quantities than those grown in the field and that field microbiota can successfully colonize plants grown indoors (35). This suggests that the greenhouse period did not greatly influence the lettuce microbiota studied.…”

“…However, river water cannot be considered a homogeneous inoculum source for different crops at a single farm. Recently, airborne bacteria have been shown to be important in forming initial phyllosphere communities (33)(34)(35). Further studies of air, soil, and water samples should be done to identify possible inoculum sources.…”

From Rare to Dominant: a Fine-Tuned Soil Bacterial Bloom during Petroleum Hydrocarbon Bioremediation

“…The results of our study suggest that an Alkanindiges-related population may be enriched in soil after amendment with abundant hydrophobic hydrocarbons. Alkanindiges strains have also been isolated from lettuce plants (47) and clinical samples (48). In this study, the Alkanindiges strain observed after diesel amendment was originally present in unpolluted soil with abundant vegetation located in Laguna Verde at the south of Valparaíso, Chile.…”