Salmonella enterica Serovar Enteritidis tatB and tatC Mutants Are Impaired in Caco-2 Cell Invasion In Vitro and Show Reduced Systemic Spread in Chickens

Abstract

Salmonella enterica subsp. enterica serovar Enteritidis is a leading causative agent of gastroenteritis in humans. This pathogen also colonizes the intestinal tracts of poultry and can spread systemically in chickens. Transfer to humans usually occurs through undercooked or improperly handled poultry meat or eggs. The bacterial twin-arginine transport (Tat) pathway is responsible for the translocation of folded proteins across the cytoplasmic membrane. In order to study the role of the Tat system in the infection and colonization of chickens by Salmonella Enteritidis, we constructed chromosomal deletion mutants of the tatB and tatC genes, which are essential components of the Tat translocon. We observed that the tat mutations affected bacterial cell morphology, motility, and sensitivity to albomycin, sodium dodecyl sulfate (SDS), and EDTA. In addition, the mutant strains showed reduced invasion of polarized Caco-2 cells. The wild-type phenotype was restored in all our Salmonella Enteritidis tat mutants by introducing episomal copies of the tatABC genes. When tested in chickens by use of a Salmonella Enteritidis ⌬tatB strain, the Tat system inactivation did not substantially affect cecal colonization, but it delayed systemic infection. Taken together, our data demonstrated that the Tat system plays a role in Salmonella Enteritidis pathogenesis.

Identification and Evaluation of Twin-Arginine Translocase Inhibitors

“…Notably, the TAT translocation system has also been demonstrated to play a role in the pathogenesis of model infections for many of these pathogens (8,16,19,33,38,71). TAT was initially not known to participate in the secretion of extracellular virulence factors (e.g., toxins) beyond the outer membrane.…”

“…For example, the genomes of some Mycobacterium tuberculosis strains can encode as many as four separate TAT-transported PlcH orthologs (37), while the Burkholderia pseudomallei genome encodes three (31), and Burkholderia mallei and Acinetobacter baumannii each encode two. Additionally, there is a growing number of other plant and animal bacterial pathogens where TAT has now been shown to be required for full virulence, including enterohemorrhagic E. coli O157:H7 (48), Salmonella enterica (38), Legionella pneumophila (15), Vibrio spp. (19,71), Yersinia pseudotuberculosis (33), Pseudomonas syringae (8), and Agrobacterium tumefaciens (16).…”

Transcriptomic and Phenotypic Analysis Reveals New Functions for the Tat Pathway in Yersinia pseudotuberculosis

“…Several studies indicate that a functional Tat system is required for many pathogenic bacteria, such as Pseudomonas syringae pv. tomato DC3000, S. enterica, Campylobacter jejuni, and Ralstonia solanacearum (5,(48)(49)(50)(51), to efficiently re- spond to diverse forms of physicochemical stresses. Indeed, our transcriptomic analysis of the Y. pseudotuberculosis ⌬tatC mutant revealed that a number of prominent stress-responsive genes were induced at both temperatures, and this number was higher during stationary-phase growth.…”

Salmonella enterica Serovar Enteritidis Antimicrobial Peptide Resistance Genes Aid in Defense against Chicken Innate Immunity, Fecal Shedding, and Egg Deposition

“…In S. Typhimurium, a mutation in msbB caused formation of elongated cells and a mutation in tatB or tatC (encoding twin arginine transport proteins required for transporting outer membrane components) caused long aggregate filaments to form (34,53). Although a mutation in somA (ybjX) suppressed many phenotypes associated with the msbB mutant, the phenotypes related to a single mutation in somA (ybjX) were not characterized in the previous study (53).…”

“…The ZM100, ⌬virK, ⌬ybjX, ⌬virK ⌬ybjX, ⌬virK pWSKVirK, and ⌬ybjX pWSKYbjX strains were tested for their sensitivity to EDTA and deoxycholic acid (DOC) as previously described (34,35). Briefly, approximately 1 ϫ 10 8 CFU bacteria were added to warm 0.5% LB agar and the mixture was poured over 1.5% LB agar plates.…”