Role of Fimbriae, Flagella and Cellulose on the Attachment of Salmonella Typhimurium ATCC 14028 to Plant Cell Wall Models

Abstract

Cases of foodborne disease caused by Salmonella are frequently associated with the consumption of minimally processed produce. Bacterial cell surface components are known to be important for the attachment of bacterial pathogens to fresh produce. The role of these extracellular structures in Salmonella attachment to plant cell walls has not been investigated in detail. We investigated the role of flagella, fimbriae and cellulose on the attachment of Salmonella Typhimurium ATCC 14028 and a range of isogenic deletion mutants (ΔfliC fljB, ΔbcsA, ΔcsgA, ΔcsgA bcsA and ΔcsgD) to bacterial cellulose (BC)-based plant cell wall models [BC-Pectin (BCP), BC-Xyloglucan (BCX) and BC-Pectin-Xyloglucan (BCPX)] after growth at different temperatures (28°C and 37°C). We found that all three cell surface components were produced at 28°C but only the flagella was produced at 37°C. Flagella appeared to be most important for attachment (reduction of up to 1.5 log CFU/cm2) although both cellulose and fimbriae also aided in attachment. The csgD deletion mutant, which lacks both cellulose and fimbriae, showed significantly higher attachment as compared to wild type cells at 37°C. This may be due to the increased expression of flagella-related genes which are also indirectly regulated by the csgD gene. Our study suggests that bacterial attachment to plant cell walls is a complex process involving many factors. Although flagella, cellulose and fimbriae all aid in attachment, these structures are not the only mechanism as no strain was completely defective in its attachment.

Attachment and colonization of Salmonella on ‘Rayada’, ‘Golden Delicious’, and ‘Red Delicious’ apples

“…14 Other researchers have found that Salmonella fimbriae are required for successful attachment in a plant cell wall model. 15 The attachment percentages found in our study are similar to those reported in tomato (0.8%), green tomato (1.3%), small green tomato (0.2%), and peach (3.0%). 11,12,16 In many reports, the populations of the attached microorganisms are expressed in concentration units (log CFU), but the inoculum level is not always shown, making it difficult to compare studies with different levels of inoculum and attached populations.…”

“…Lipopolysaccharides have a protective role in the immunity mechanisms of animals and plants . Other researchers have found that Salmonella fimbriae are required for successful attachment in a plant cell wall model …”

Systematic analyses of factors required for adhesion ofSalmonella entericaserovar Typhimurium to corn salad (Valerianella locusta)

“…The effect of flagella and motility on infection of various plants has been previously investigated for Salmonella and other pathogenic bacteria (15, 38, 39). Here we demonstrate the binding properties and the contribution of motility in adhesion to corn salad using four distinct deletion strains.…”

Interaction between Salmonella and Plants: Potential Hosts and Vectors for Human Infection

“…Bioilm formation of Salmonella is inluenced by environmental conditions and is reported to be maximal under reduced nutrient availability, aerobic conditions, low osmolarity, and mid temperatures [73], which are characteristic for the plant surface. In contrast, it was shown in vitro that S. Typhimurium cells grown at 37°C, the temperature in the animal host, do not produce cellulose and imbriae [64]. Furthermore, the red dry and rough (rdar) and the smooth and white (saw) morphotypes, regulated by the agfD promoter and deined by a combination of traits such as the presence of thin aggregative imbriae (tai), cellulose, and O-antigen capsule, might afect the dispersal of Salmonella in an agricultural environment [74].…”

“…Several bacterial elements such as imbrial structures, nonimbrial adhesins, lagella, cellulose, and lipopolysaccharides (LPS) are important bacterial factors for colonization [63,64]. Although previous studies demonstrated that the atachment depends on plant and bacterial factors, no single factor was found to be essential, suggesting that bacteria use several parallel mechanisms to ensure atachment to diferent plants or to diferent plant cells under a wide variety of conditions [65].…”