Flagellated but Not Hyperfimbriated Salmonella enterica Serovar Typhimurium Attaches to and Forms Biofilms on Cholesterol-Coated Surfaces

Abstract

The asymptomatic, chronic carrier state of Salmonella enterica serovar Typhi occurs in the bile-rich gallbladder and is frequently associated with the presence of cholesterol gallstones. We have previously demonstrated that salmonellae form biofilms on human gallstones and cholesterol-coated surfaces in vitro and that bile-induced biofilm formation on cholesterol gallstones promotes gallbladder colonization and maintenance of the carrier state. Random transposon mutants of S. enterica serovar Typhimurium were screened for impaired adherence to and biofilm formation on cholesterol-coated Eppendorf tubes but not on glass and plastic surfaces. We identified 49 mutants with this phenotype. The results indicate that genes involved in flagellum biosynthesis and structure primarily mediated attachment to cholesterol. Subsequent analysis suggested that the presence of the flagellar filament enhanced binding and biofilm formation in the presence of bile, while flagellar motility and expression of type 1 fimbriae were unimportant. Purified Salmonella flagellar proteins used in a modified enzyme-linked immunosorbent assay (ELISA) showed that FliC was the critical subunit mediating binding to cholesterol. These studies provide a better understanding of early events during biofilm development, specifically how salmonellae bind to cholesterol, and suggest a target for therapies that may alleviate biofilm formation on cholesterol gallstones and the chronic carrier state.

Salmonella spp. survival strategies within the host gastrointestinal tract

“…As cholesterol is the primary constituent of human cholesterol gallstones, cholesterolcoated Eppendorf tubes have been employed to mimic human gallstones in vitro, and Salmonella has been shown to form biofilms on these tubes (Crawford et al, 2008). Screening of a random transposon bank for mutants that were impaired in biofilm formation on cholesterol-coated Eppendorf tubes led to the identification of 49 mutants with this phenotype (Crawford et al, 2010a). The results revealed that genes involved in flagellum biosynthesis and structure primarily mediated attachment to cholesterol (Crawford et al, 2010a).…”

“…Screening of a random transposon bank for mutants that were impaired in biofilm formation on cholesterol-coated Eppendorf tubes led to the identification of 49 mutants with this phenotype (Crawford et al, 2010a). The results revealed that genes involved in flagellum biosynthesis and structure primarily mediated attachment to cholesterol (Crawford et al, 2010a).…”

Salmonella: Invasion, Evasion & Persistence

“…Interestingly, however, formation of Salmonella biofilms on gallstones is dependent on the presence of bile (Prouty et al, 2002). Bile is known to interact and manipulate gene expression in Salmonella biofilms, such as downregulating SPI-1 genes and mobility genes (Crawford et al, 2010;Prouty & Gunn, 2000). Despite this, the effects are believed to be minimal and may not dramatically affect the abilitiy of Salmonella's to invade via effectors of SPI-1 or migrate via flagella.…”

Salmonella enterica Serovar Kentucky Flagella Are Required for Broiler Skin Adhesion and Caco-2 Cell Invasion

“…Furthermore, transposon mutagenesis of S. Typhimurium in flagellar hook-associated protein and lipopolysaccharide synthesis severely altered attachment to meat and poultry and biofilm formation on different surfaces (21). In a more recent study with S. Typhimurium motA, fliC, fljB, and fliC fljB mutants, it was concluded that flagellar motility does not affect biofilm formation on cholesterol surfaces, but fliC expression does (22).…”