Establishment Limitation Constrains the Abundance of Lactic Acid Bacteria in the Napa Cabbage Phyllosphere

Abstract

Patterns of phyllosphere diversity have become increasingly clear with high-throughput sequencing surveys, but the processes that control phyllosphere diversity are still emerging. Through a combination of lab and field experiments using Napa cabbage and lactic acid bacteria (LAB), we examined how dispersal and establishment processes shape the ecological distributions of phyllosphere bacteria. We first determined the abundance and diversity of LAB on Napa cabbage grown at three sites using both culture-based approaches and 16S rRNA gene amplicon sequencing. Across all sites, LAB made up less than 0.9% of the total bacterial community abundance. To assess whether LAB were low in abundance in the Napa cabbage phyllosphere due to a limited abundance in local species pools (source limitation), we quantified LAB in leaf and soil samples across 51 vegetable farms and gardens throughout the northeastern United States. Across all sites, LAB comprised less than 3.2% of the soil bacterial communities and less than 1.6% of phyllosphere bacterial communities. To assess whether LAB are unable to grow in the phyllosphere even if they dispersed at high rates (establishment limitation), we used a gnotobiotic Napa cabbage system in the lab with experimental communities mimicking various dispersal rates of LAB. Even at high dispersal rates, LAB became rare or completely undetectable in experimental communities, suggesting that they are also establishment limited. Collectively, our data demonstrate that the low abundance of LAB in phyllosphere communities may be explained by establishment limitation. IMPORTANCE The quality and safety of vegetable fermentations are dependent on the activities of LAB naturally present in the phyllosphere. Despite their critical role in determining the success of fermentation, the processes that determine the abundance and diversity of LAB in vegetables used for fermentation are poorly characterized. Our work demonstrates that the limited ability of LAB to grow in the cabbage phyllosphere environment may constrain their abundance on cabbage leaves. These results suggest that commercial fermentation of Napa cabbage proceeds despite low and variable abundances of LAB across different growing regions. Propagule limitation may also explain ecological distributions of other rare members of phyllosphere microbes.

Abundance, diversity and plant‐specific adaptations of plant‐associated lactic acid bacteria

“…For example, silage produced from wilted Italian ryegrass, whole crop corn, or wilted alfalfa were distinct such that the three fermentations were dominated by different LAB species over a two month time‐span in a manner that was not predicted based on the pre‐ensiled crop microbiota (Ni et al ., ). Similarly, inoculation of Napa cabbage with a mixture of Pediococcus pentosaceus B6N, L. mesenteroides BN10 and L. plantarum MRK2 strains isolated from plants did not affect cabbage fermentation outcomes (Miller et al ., ).…”

“…Reductions in L. plantarum PM411 culturable cell numbers were also observed after application onto apple and pear blossoms in the field, with a fraction of PM411 cells entering into a viable but non‐culturable state (Daranas et al ., ). Similarly, plant‐associated P. pentosaceus B6N, L. mesenteroides BN10, L. plantarum MKR2, or L. lactis D119, did not grow on gnotobiotic‐ or field‐grown Napa cabbage (Miller et al ., ). Although it is possible that the conditions needed to support robust LAB growth on plant tissues have yet to be identified, a compelling possibility is that plants serve as a reservoir for either slow growing or dormant but viable LAB.…”

Fermented food metagenomics reveals substrate-associated differences in taxonomy, health-associated- and antibiotic resistance-determinants

“…The brine-type foods tested comprised 26 plant substrate-derived foods fermented in a saline solution. Unlike both dairy- and sugar-type fermented foods, the majority of the brine-based foods undergo a spontaneous fermentation and, therefore, rely on fermentation by autochthonous microbes[51]. Among brine-type foods, Lactobacillus was the most abundant genus, comprising 46.8% of all reads assigned at the genus level.…”

Formation of a Mixed-Species Biofilm Is a Survival Strategy for Unculturable Lactic Acid Bacteria and Saccharomyces cerevisiae in Daqu, a Chinese Traditional Fermentation Starter

“…and S. cerevisiae (Tamang et al, 2016). Also, the research of fermented cabbage explained that although LAB is hardly detected in the Napa cabbage phyllosphere, the anaerobic, salty, and sugar-rich conditions of the fermentation environment make them dominant in the cabbage fermentation (Miller et al, 2019). Similar to cabbage fermentation, the suitable fermentation environment could be the reason for the dominance of Lactobacillus sp.…”