Biology subjects

Culliney, P.

Publications and source records attributed to Culliney, P..

2 recordsLinked to original sources

bioRxiv2024

Cultivation conditions of leafy vegetables determine phyllosphere bacterial community structures and ultimately affect growth of L. monocytogenes post-harvest

Cultivation conditions including plant species, variety, cultivation method and seasonality are all at least co-factors of epiphytic growth of L. monocytogenes. Meanwhile, phyllosphere associated bacteria were found to influence colonisation of invading pathogens. Thus, the main objective of this study was to determine whether cultivation conditions are factors in the development of the bacterial phyllosphere community on leafy vegetables which consequently influences L. monocytogenes growth. Indeed, this study revealed that vegetable cultivation condition was a more influential determinant of phyllosphere development than plant species. Of the identified phyllosphere associated bacteria presence of Pseudomonadaceae had a positive correlation with L. monocytogenes populations on all tested produce. Yet, Pseudomonadaceae content appeared to be more important for L. monocytogenes growth on spinach F1 Trumpet. From day 7 to 9 of storage, Pseudomonadaceae increases on open field spinach F1 Trumpet were associated with L. monocytogenes largest increase (0.94 log10 cfu g-1), whereas Pseudomonadaceae content decreased for polytunnel spinach F1 Trumpet and the corresponding L. monocytogenes populations remained unchanged. Carnobacteriaceae were present on spinach F1 Trumpet from polytunnel but not on other spinach produce with higher associated L. monocytogenes growth. Pectobacteriaceae (genus Dickeya) increased for spinach F1 Trumpet polytunnel but decreased for other spinach produce with lower associated L. monocytogenes growth. Similarly, polytunnel rocket Esmee had an increasing relative abundance of Pectobacteriaceae whereas it remained constant for polytunnel rocket Buzz. Compared to summer spinach F1 Trumpet produce, winter produce had significantly greater Streptococcaceae content and was correlated with a decrease in L. monocytogenes growth. Finally, higher phyllosphere alpha diversity putatively limited L. monocytogenes growth. Ultimately, this study revealed that cultivation conditions determine bacterial phyllosphere community structure which consequently influences L. monocytogenes growth.

microbiology↗

bioRxiv2024

Bacterial community structure analysis on Listeria monocytogenes inoculated spinach leaves is affected by PCR based methods to exclude chloroplast co-amplification

Consumption of ready-to-eat leafy vegetables has increased in popularity due to their anticipated health benefits, but their consumption also poses a potential health risk in the form of foodborne pathogens. Listeria monocytogenes is a ubiquitous pathogen that has been regularly found on leafy vegetables including spinach. Growth determining factors go beyond plant species and cultivation practice and may include the phyllosphere bacteriome to affect the growth potential of L. monocytogenes. This study investigated the bacteriome of spinach leaves, stored under EURL challenge conditions for 9 days after inoculation with L. monocytogenes using two methods of excluding chloroplast co-amplification (COMPETE, BLOCK) at the PCR step as well as a post-PCR chloroplast sequence filter option (CONTROL). While all three approaches have demonstrated a change of bacterial communities over time, the pPNA based BLOCK approach resulted in greater diversity similarities to the CONTROL option. The COMPETE solution with a specifically designed primer to prevent chloroplast amplification had a strong underrepresentation of the Planctomycetota phylum and to a lesser extend underrepresentation of Chloroflexi and Verrucomicrobiota due to the inheritance of the selected primer region that allowed to deselect chloroplast co-amplification. However, the COMPETE approach had the lowest level of chloroplast co-amplification. Higher growth potential of L. monocytogenes from day 7 to 9 co-occurred with higher relative abundances of Pseudomonadaceae and lower numbers of Lactobacillales, suggesting that particular phylogenetic groups may support growth of L. monocytogenes. While chloroplast co-amplification with spinach in the present study was relatively modest and a purely filter based chloroplast removal was sufficient, other leafy vegetables may require one of the tested co-amplification prevention solutions. While the COMPETE solution in the present study was linked to some amplification bias, the approach may be useful when otherwise co-amplification is very high and the demonstrated BLOCK approach with pPNA is insufficient.

microbiology↗