Transcriptome sequencing reveals the difference in the expression of biofilm and planktonic cells between two strains of Salmonella Typhimurium

Abstract

Salmonela enterica serovar Typhimurium (S. Typhimurium) is a food-borne pathogen that can form biofilms to increase its resistance to the external environment. Through the detection of biofilm of several S. Typhimurium strains in this study, strain CDC3 with strong biofilm forming capacity and strain CVCC3384 with weak biofilm forming capacity were identified. The genes expressed in planktonic and biofilm cells of two S. Typhimurium strains were analysed by transcriptome sequencing. Results showed that the genes related to the signal transduction pathway were upregulated and genes related to motility were downregulated in strain CDC3. By comparing biofilms and planktonic cells of the two strains, we found that CDC3 regulates biofilm formation mainly through the two-component system kdpABC, while strain CVCC3384 does so mainly through motility and quorum sensing. This study revealed regulation mechanism of biofilms formation between different biofilm forming capacity strains, and provided a theoretical basis for subsequent research.

Keywords: Biofilm; Differential gene expression; Planktonic; S. Typhimurium; Transcriptome sequencing.

Fig. 1

Biofilm formation of S.Typhimurium under different environmental conditions. a, the temperature (20 °C,25 °C,30 °C,37 °C); b, the pH (3.0–10.0); c, sodium chloride (0–2.0%).

Fig. 2

Sample correlation heat map. Both the horizontal and vertical axes represent each sample. The color represents the correlation coefficient (the darker the color is, the higher the correlation is, and the lighter the color is, the lower the correlation is). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

Volcanic map of four groups of differential genes. The significantly up-regulated genes were represented by red dots, the significantly down-regulated genes were expressed by blue dots, and the genes with no significant differences were expressed by gray dots.

Fig. 4

Enrichment of differential gene GO pathways in four sets of comparative analysis. a, DEGs in biofilm cells of strains CDC3 and CVCC3384; b, DEGs between biofilm and planktonic cells of CDC3; c, DEGs between biofilm and planktonic cells of CVCC3384; d, DEGs in planktonic cells of strains CDC3 and CVCC3384. The genes on the left are up-regulated and those on the right are down-regulated.

Fig. 5

Enrichment of differential gene KEGG pathways in four sets of comparative analysis. a, DEGs in biofilm cells of strains CDC3 and CVCC3384; b, DEGs between biofilm and planktonic cells of CDC3; c, DEGs between biofilm and planktonic cells of CVCC3384; d, DEGs in planktonic cells of strains CDC3 and CVCC3384. The genes on the left are up-regulated and those on the right are down-regulated.

Fig. 6

RT-PCR verification. a, b, c and d are the results of differential gene verification between strain CVCC3384 biofilm bacteria and plankton bacteria, strain CDC3 biofilm bacteria and plankton bacteria RT-PCR, strain CDC3 and CVCC3384 biofilm cell differential genes, strain CDC3 and CVCC3384 plankton cell differential gene verification results.

Fig. S1

The assembly process of flagella. The genes that are down-regulated in the biofilm cells of strain CDC3 are marked in green.

Fig. S2

Bacterial chemotaxis. The down-regulated genes in the biofilm cells of strain CDC3 are marked in green, and the up-regulated genes are marked in red.

Fig. S3

Regulation of two-component system in biofilm cells of strain CDC3. The red color are the up-regulated genes; the green color are the down-regulated genes.