Microscopic and transcriptomic characterization of Listeria monocytogenes aggregation and biofilm formation in cantaloupe juice

Authors: REDDING, MARINA - ORISE FELLOW; ZHENG, JIE - FOOD AND DRUG ADMINISTRATION(FDA); MOWERY, JOSEPH; Gu, Ganyu; BOLTEN, SAMANTHA - ORISE FELLOW; Luo, Yaguang - Sunny; Nou, Xiangwu

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2023
Publication Date: 12/3/2023
Citation: Redding, M., Zheng, J., Mowery, J.D., Gu, G., Bolten, S., Luo, Y., Nou, X. 2023. Microscopic and transcriptomic characterization of Listeria monocytogenes aggregation and biofilm formation in cantaloupe juice. Food Control. https://doi.org/10.1016/j.foodcont.2023.110243.
DOI: https://doi.org/10.1016/j.foodcont.2023.110243

Interpretive Summary: Biofilm formation is a strategy for microorganisms, including foodborne pathogens such as Listeria monocytogenes, to survive environmental stresses. It is a major mechanism for L. monocytogenes to persist and to contaminate food in the processing environment. In this study, ARS scientists, in collaboration with a FDA scientist, investigated the biofilm formation of L. monocytogenes in cantaloupe juice, which is likely the major nutrient source in cantaloupe processing facilities. Microscopic and transcriptomic analyses were carried out to determine the characteristics of the biofilms and the effect on bacterial global gene expression. This study showed that L. monocytogenes growth in cantaloupe juice resulted in strong autoaggregation and biofilm formation. Growth in cantaloupe juice also led to modulation of global gene expression, with genes in multiple pathways significantly up or down regulated. Results from this study provided the basis for future functional characterization of genes with potential roles in Lm biofilm formation and persistence in fresh produce processing environments, as well as for development of mitigation practices against L. monocytogenes biofilms on produce and food contact surfaces.

Technical Abstract: Plant exudate is likely the major nutrient source supporting the survival and biofilm formation of microorganisms in fresh produce processing environments. This study compared the impact of cantaloupe juice on the physiology and gene expression of Listeria monocytogenes (Lm) using microscopic and transcriptomic tools. Lm showed a strong autoaggregation and formed significantly more biofilms on stainless steel (SS) coupons when grown in cantaloupe juice in comparison to in TSB. SEM images revealed a different attachment profile of Lm on SS coupons. In TSB, Lm cells were mainly found in scratches and grooves of the metal surface, whereas, in cantaloupe juice they attached to the smooth surface as well. Lm planktonic and biofilm cells in cantaloupe juice exhibited stress-induced phenotypes, including strong cell elongation and increased proportion of cells with membrane permeability. Lm growth in cantaloupe juice resulted in distinct transcriptional profiles of both biofilm and planktonic cells in comparison to that in TSB. Functional annotation indicated that the significantly differentially expressed genes mainly participated in metabolism, signaling and stress response. Notably, certain pathways downregulated for planktonic cells were significantly upregulated for biofilm cells in cantaloupe juice compared to TSB, including ABC transporters, two-component system, quorum sensing, chemotaxis, and flagellar assembly.