Studies on host-foodborne bacteria in intestinal three-dimensional cell culture model indicate possible mechanisms of interaction

Applying 3D cultures and high-throughput technologies to study host-pathogen interactions

Recent advances in cell culturing and DNA sequencing have dramatically altered the field of human microbiome research. Three-dimensional (3D) cell culture is an important tool in cell biology, in cancer research, and for studying host-microbe interactions, as it mimics the in vivo characteristics of the host environment in an in vitro system, providing reliable and reproducible models. This work provides an overview of the main 3D culture techniques applied to study interactions between host cells and pathogenic microorganisms, how these systems can be integrated with high-throughput molecular methods, and how multi-species model systems may pave the way forward to pinpoint interactions among host, beneficial microbes and pathogens.

Mutual adhesion of Lactobacillus spp. to intestinal cells: A review of perspectives on surface layer proteins and cell surface receptors

The bacterial ability to adhere and colonize in the gut is a key prerequisite to become a probiotic. Lactobacillus spp. surface layer proteins (SLPs) play an important role for such functions in the human body. Interestingly, all SLPs in spite of their structural variation promote adhesion and colonization. A clear understanding about the binding sites of SLPs with the host and their binding modes would help to precisely reveal the process of Lactobacillus spp.-host interaction. Therefore, in this paper, we have sorted out the Lactobacillus spp. SLPs and their adhesion sites in human intestinal cells. Such SLPs included surface layer protein, motif proteins, binding proteins and moonlighting proteins, while enterocyte adhesion receptors included transmembrane glycoproteins and extracellular matrix proteins. We also summarized the tools to assess the adhesion by Lactobacillus spp. Finally, we recommended that three-dimensional cell models and intestinal microarrays could be major tools for assessing adhesion in the future.

The Characteristics and Function of Internalin G in Listeria monocytogenes

In order to clarified characteristics and function of internalin G (inlG) in Listeria monocytogenes ATCC®19111 (1/2a) (LM), the immune protection of the inlG was evaluated in mice, the homologous recombination was used to construct inlG deletion strains, and their biological characteristics were studied by the transcriptomics analysis. As a result, the immunization of mice with the purified protein achieved a protective effect against bacterial infection. The deletion strain LM-AinlG was successfully constructed with genetic stability. The mouse infection test showed that the virulence of LM was decreased after the deletion of the inlG gene. The deletion strain showed enhanced adhesion to and invasion of Caco-2 cells. Compared to the wild strain, 18 genes were up-regulated, and 24 genes were down-regulated in the LM-AinlG. This study has laid a foundation for further research on the function of inlG and the pathogenesis of LM. In this study, immunization of mice with the purified inlG protein achieved a protective effect against Listeria monocytogenes infection. The virulence of LM-ΔinlG was decreased by mouse infection. However, the adhesion and invasion ability to Caco-2 cell were enhanced. Compared to the wild strain, 18 genes were up-regulated, and 24 genes were down-regulated in the LM-ΔinlG. This study has laid a foundation for further study of the function of the inlG and the listeriosis.

Lactiplantibacillus plantarum subsp. plantarum and Fructooligosaccharides Combination Inhibits the Growth, Adhesion, Invasion, and Virulence of Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen responsible for many food outbreaks worldwide. This study aimed to investigate the single and combined effect of fructooligosaccharides (FOS) and Lactiplantibacillus plantarum subsp. plantarum CICC 6257 (L. plantarum) on the growth, adhesion, invasion, and virulence of gene expressions of Listeria monocytogenes 19112 serotype 4b (L. monocytogenes). Results showed that L. plantarum combined with 2% and 4% (w/v) FOS significantly (p < 0.05) inhibited the growth of L. monocytogenes (3-3.5 log10 CFU/mL reduction) at the incubation temperature of 10 °C and 25 °C. Under the same combination condition, the invasion rates of L. monocytogenes to Caco-2 and BeWo cells were reduced more than 90% compared to the result of the untreated group. After L. plantarum was combined with the 2% and 4% (w/v) FOS treatment, the gene expression of actin-based motility, sigma factor, internalin A, internalin B, positive regulatory factor A, and listeriolysin O significantly (p < 0.05) were reduced over 91%, 77%, 92%, 89%, 79%, and 79% compared to the result of the untreated group, respectively. The inhibition level of the L. plantarum and FOS combination against L. monocytogenes was higher than that of FOS or L. plantarum alone. Overall, these results indicated that the L. plantarum and FOS combination might be an effective formula against L. monocytogenes.