scholarly journals Conserved tandem arginines for PbgA/YejM allow Salmonella to regulate LpxC and control lipopolysaccharide biogenesis during infection

2020 ◽  
Author(s):  
Nicole P. Giordano ◽  
Joshua A. Mettlach ◽  
Zachary D. Dalebroux
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Transmembrane Protein ◽  
Systemic Disease ◽  
Side Chain ◽  
Serovar Typhimurium ◽  
And Control ◽  
Rate Limiting ◽  
Severe Systemic Disease

ABSTRACTSalmonella enterica serovar Typhimurium uses PbgA/YejM, a conserved multi-pass transmembrane protein with a soluble periplasmic domain (PD), to balance the glycerophospholipid (GPL) and lipopolysaccharide (LPS) concentrations within the outer membrane (OM). The lipid homeostasis and virulence defects of pbgAΔ191-586 mutants, which are deleted for the PD, can be suppressed by substitutions in three LPS regulators, LapB/YciM, FtsH, and LpxC. We reasoned that S. Typhimurium uses the PbgA PD to regulate LpxC through functional interactions with LapB and FtsH. In the stationary phase of growth, pbgAΔ191-586 mutants accumulated LpxC and overproduced LPS precursors, known as lipid A-core molecules. Trans-complementation fully decreased the LpxC and lipid A-core levels for the mutants, while substitutions in LapB, FtsH, and LpxC variably reduced the concentrations. PbgA binds lipid A-core, in part, using dual arginines, R215 and R216, which are located near the plasma membrane. Neutral, conservative, and non-conservative substitutions were engineered at these positions to test whether the side-chain charges for residues 215 and 216 influenced LpxC regulation. Salmonellae that expressed PbgA with dual alanines or aspartic acids overproduced LpxC, accumulated lipid A-core and short-LPS molecules, and were severely attenuated in mice. Bacteria that expressed PbgA with tandem lysines were fully virulent in mice and yielded LpxC and lipid A-core levels that were similar to the wild type. Thus, S. Typhimurium uses the cationic charge of PbgA R215 and R216 to down-regulate LpxC and decrease lipid A-core biosynthesis in response to host stress and this regulatory mechanism enhances their virulence during bacteremia.IMPORTANCESalmonella enterica serovar Typhimurium causes self-limiting gastroenteritis in healthy individuals and severe systemic disease in immunocompromised humans. The pathogen manipulates the immune system of its host by regulating the lipid, protein, and polysaccharide content of the outer membrane (OM) bilayer. Lipopolysaccharides (LPS) comprise the external leaflet of the OM, and are essential for establishing the OM barrier and providing gram-negative microbes with intrinsic antimicrobial resistance. LPS molecules are potent endotoxins and immunomodulatory ligands that bind host-pattern receptors, which control host resistance and adaptation during infection. Salmonellae use the cationic charge of dual arginines for PbgA/YejM to negatively regulate LPS biosynthesis. The mechanism involves PbgA binding to an LPS precursor and activating a conserved multi-protein signal transduction network that cues LpxC proteolysis, the rate-limiting enzyme. The cationic charge of the tandem arginines is critical for the ability of salmonellae to survive intracellularly and to cause systemic disease in mice.

Conserved tandem arginines for PbgA/YejM allow Salmonella Typhimurium to regulate LpxC and control lipopolysaccharide biogenesis during infection.

2021 ◽  
Author(s):  
Nicole P. Giordano ◽  
Joshua A. Mettlach ◽  
Zachary D. Dalebroux
Keyword(s):  
Lipid A ◽  
Systemic Disease ◽  
Alpha Helix ◽  
Transmembrane Segments ◽  
Ftsh Protease ◽  
Serovar Typhimurium ◽  
Inner Membrane Protein ◽  
Key Residues ◽  
And Control ◽  
Basic Region

Enterobacteriaceae use the periplasmic domain of the conserved inner membrane protein, PbgA/YejM, to regulate lipopolysaccharide (LPS) biogenesis. Salmonella enterica serovar Typhimurium ( S. Typhimurium) relies on PbgA to cause systemic disease in mice and this involves functional interactions with LapB/YciM, FtsH, and LpxC. Escherichia coli PbgA interacts with LapB, an adaptor for the FtsH protease, via the transmembrane segments. LapB and FtsH control proteolysis of LpxC, the rate-limiting LPS biosynthesis enzyme. Lipid A-core, the hydrophobic anchor of LPS molecules, co-crystallizes with PbgA and interacts with residues in the basic region. The model predicts that PbgA-LapB detects periplasmic LPS molecules and prompts FtsH to degrade LpxC. However, the key residues and critical interactions are not defined. We establish that S. Typhimurium uses PbgA to regulate LpxC and define the contribution of two pairs of arginines within the basic region. PbgA R215 R216 form contacts with lipid A-core in the structure and R231 R232 exist in an adjacent alpha helix. PbgA R215 R216 are necessary for S . Typhimurium to regulate LpxC, control lipid-A core biogenesis, promote survival in macrophages, and enhance virulence in mice. In contrast, PbgA R231 R232 are not necessary to regulate LpxC or to control lipid A-core levels, nor are they necessary to promote survival in macrophages or mice. However, residues R231 R232 are critical for infection lethality, and the persistent infection phenotype requires mouse Toll-like receptor four, which detects lipid A. Therefore, S. Typhimurium relies on PbgA’s tandem arginines for multiple interconnected mechanisms of LPS regulation that enhance pathogenesis.

scholarly journals Yersinia pestis Is Viable with Endotoxin Composed of Only Lipid A

2005 ◽  
Vol 187 (18) ◽  
pp. 6599-6600 ◽  
Author(s):  
Li Tan ◽  
Creg Darby
Keyword(s):  
Escherichia Coli ◽  
Yersinia Pestis ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Gram Negative Bacteria ◽  
Membrane Component ◽  
Gram Negative ◽  
Serovar Typhimurium

ABSTRACT Lipopolysaccharide (LPS) is the major outer membrane component of gram-negative bacteria. The minimal LPS structure for viability of Escherichia coli and Salmonella enterica serovar Typhimurium is lipid A glycosylated with 3-deoxy-D-manno-octulosonic acid (Kdo) residues. Here we show that another member of the Enterobacteriaceae, Yersinia pestis, can survive without Kdo in its LPS.

scholarly journals Inhibition of Salmonella enterica Serovar Typhimurium Lipopolysaccharide Deacylation by Aminoarabinose Membrane Modification

2005 ◽  
Vol 187 (7) ◽  
pp. 2448-2457 ◽  
Author(s):  
Kiyoshi Kawasaki ◽  
Robert K. Ernst ◽  
Samuel I. Miller
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Bacterial Resistance ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Host Recognition ◽  
Membrane Modification ◽  
Serovar Typhimurium ◽  
Nonionic Detergent

ABSTRACT Salmonella enterica serovar Typhimurium remodels the lipid A component of lipopolysaccharide, a major component of the outer membrane, to survive within animals. The activation of the sensor kinase PhoQ in host environments increases the synthesis of enzymes that deacylate, palmitoylate, hydroxylate, and attach aminoarabinose to lipid A, also known as endotoxin. These modifications promote bacterial resistance to antimicrobial peptides and reduce the host recognition of lipid A by Toll-like receptor 4. The Salmonella lipid A 3-O-deacylase, PagL, is an outer membrane protein whose expression is regulated by PhoQ. In S. enterica serovar Typhimurium strains that had the ability to add aminoarabinose to lipid A, 3-O-deacylated lipid A species were not detected, despite the PhoQ induction of PagL protein expression. In contrast, strains defective for the aminoarabinose modification of lipid A demonstrated in vivo PagL activity, indicating that this membrane modification inhibited PagL's enzymatic activity. Since not all lipid A molecules are modified with aminoarabinose upon PhoQ activation, these results cannot be ascribed to the substrate specificity of PagL. PagL-dependent deacylation was detected in sonically disrupted membranes and membranes treated with the nonionic detergent n-octyl-β-d-glucopyranoside, suggesting that perturbation of the intact outer membrane releases PagL from posttranslational inhibition by aminoarabinose-containing membranes. Taken together, these results suggest that PagL enzymatic deacylation is posttranslationally inhibited by membrane environments, which either sequester PagL from its substrate or alter its conformation.

scholarly journals Phosphate Groups of Lipid A Are Essential for Salmonella enterica Serovar Typhimurium Virulence and Affect Innate and Adaptive Immunity

2012 ◽  
Vol 80 (9) ◽  
pp. 3215-3224 ◽  
Author(s):  
Qingke Kong ◽  
David A. Six ◽  
Qing Liu ◽  
Lillian Gu ◽  
Shifeng Wang ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Adaptive Immunity ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Outer Membrane Proteins ◽  
Polymyxin B ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Phosphate Groups

ABSTRACTLipid A is a key component of the outer membrane of Gram-negative bacteria and stimulates proinflammatory responses via the Toll-like receptor 4 (TLR4)-MD2-CD14 pathway. Its endotoxic activity depends on the number and length of acyl chains and its phosphorylation state. InSalmonella entericaserovar Typhimurium, removal of the secondary laurate or myristate chain in lipid A results in bacterial attenuation and growth defectsin vitro. However, the roles of the two lipid A phosphate groups in bacterial virulence and immunogenicity remain unknown. Here, we used anS. TyphimuriummsbB pagL pagP lpxRmutant, carrying penta-acylated lipid A, as the parent strain to construct a series of mutants synthesizing 1-dephosphorylated, 4′-dephosphorylated, or nonphosphorylated penta-acylated lipid A. Dephosphorylated mutants exhibited increased sensitivity to deoxycholate and showed increased resistance to polymyxin B. Removal of both phosphate groups severely attenuated the mutants when administered orally to BALB/c mice, but the mutants colonized the lymphatic tissues and were sufficiently immunogenic to protect the host from challenge with wild-typeS. Typhimurium. Mice receivingS. Typhimurium with 1-dephosphorylated or nonphosphorylated penta-acylated lipid A exhibited reduced levels of cytokines. Attenuated and dephosphorylatedSalmonellavaccines were able to induce adaptive immunity against heterologous (PspA ofStreptococcus pneumoniae) and homologous antigens (lipopolysaccharide [LPS] and outer membrane proteins [OMPs]).

scholarly journals PhoPQ-Mediated Regulation Produces a More Robust Permeability Barrier in the Outer Membrane of Salmonella enterica Serovar Typhimurium

2007 ◽  
Vol 189 (20) ◽  
pp. 7213-7222 ◽  
Author(s):  
Takeshi Murata ◽  
Will Tseng ◽  
Tina Guina ◽  
Samuel I. Miller ◽  
Hiroshi Nikaido
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Divalent Cations ◽  
Nile Red ◽  
Permeability Barrier ◽  
Eosin Y ◽  
Drug Induced ◽  
Serovar Typhimurium ◽  
High Concentrations

ABSTRACT The PhoPQ two-component system of Salmonella enterica serovar Typhimurium produces a remodeling of the lipid A domain of the lipopolysaccharide, including the PagP-catalyzed addition of palmitoyl residue, the PmrAB-regulated addition of the cationic sugar 4-aminoarabinose and phosphoethanolamine, and the LpxO-catalyzed addition of a 2-OH group onto one of the fatty acids. By using the diffusion rates of the dyes ethidium, Nile red, and eosin Y across the outer membrane, as well as the susceptibility of cells to large, lipophilic agents, we evaluated the function of this membrane as a permeability barrier. We found that the remodeling process in PhoP-constitutive strains produces an outer membrane that serves as a very effective permeability barrier in an environment that is poor in divalent cations or that contains cationic peptides, whereas its absence in phoP null mutants produces an outer membrane severely compromised in its barrier function under these conditions. Removing combinations of the lipid A-remodeling functions from a PhoP-constitutive strain showed that the known modification reactions explain a major part of the PhoPQ-regulated changes in permeability. We believe that the increased barrier property of the remodeled bilayer is important in making the pathogen more resistant to the stresses that it encounters in the host, including attack by the cationic antimicrobial peptides. On the other hand, drug-induced killing assays suggest that the outer membrane containing unmodified lipid A may serve as a better barrier in the presence of high concentrations (e.g., 5 mM) of Mg2+.

scholarly journals Murein Lipoprotein Is a Critical Outer Membrane Component Involved in Salmonella enterica Serovar Typhimurium Systemic Infection

2005 ◽  
Vol 73 (2) ◽  
pp. 1081-1096 ◽  
Author(s):  
A. A. Fadl ◽  
J. Sha ◽  
G. R. Klimpel ◽  
J. P. Olano ◽  
D. W. Niesel ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Enteric Bacteria ◽  
Host Cells ◽  
Double Knockout ◽  
In Vivo Models ◽  
Serovar Typhimurium

ABSTRACT Lipopolysaccharide (LPS) and Braun (murein) lipoprotein (Lpp) are major components of the outer membrane of gram-negative enteric bacteria that function as potent stimulators of inflammatory and immune responses. In a previous paper, we provided evidence that two functional copies of the lipoprotein gene (lppA and lppB) located on the chromosome of Salmonella enterica serovar Typhimurium contributed to bacterial virulence. In this study, we characterized lppA and lppB single-knockout (SKO) mutants and compared them with an lpp double-knockout (DKO) mutant using in vitro and in vivo models. Compared to the lpp DKO mutant, which was nonmotile, the motility of the lpp SKO mutants was significantly increased (73 to 77%), although the level of motility did not reach the level of wild-type (WT) S. enterica serovar Typhimurium. Likewise, the cytotoxicity was also significantly increased when T84 human intestinal epithelial cells and RAW264.7 murine macrophages were infected with the lpp SKO mutants compared to the cytotoxicity when cells were infected with the lpp DKO mutant. The level of interleukin-8 (IL-8) in polarized T84 cells infected with the lppB SKO mutant was significantly higher (two- to threefold higher), reaching the level in cells infected with WT S. enterica serovar Typhimurium, than the level in host cells infected with the lppA SKO mutant. The lpp DKO mutant induced minimal levels of IL-8. Similarly, sera from mice infected with the lppB SKO mutant contained 4.5- to 10-fold-higher levels of tumor necrosis factor-α and IL-6; the levels of these cytokines were 1.7- to 3.0-fold greater in the lppA SKO mutant-infected mice than in animals challenged with the lpp DKO mutant. The increased cytokine levels observed with the lppB SKO mutant in mice correlated with greater tissue damage in the livers and spleens of these mice than in the organs of animals infected with the lppA SKO and lpp DKO mutants. Moreover, the lppB SKO mutant-infected mice had increased susceptibility to death. Since the lpp DKO mutant retained intact LPS, we constructed an S. enterica serovar Typhimurium triple-knockout (TKO) mutant in which the lppA and lppB genes were deleted from an existing msbB mutant (msbB encodes an enzyme required for the acylation of lipid A). Compared to the lpp DKO and msbB SKO mutants, the lpp-msbB TKO mutant was unable to induce cytotoxicity and to produce cytokines and chemokines in vitro and in vivo. These studies provided the first evidence of the relative contributions of Lpp and lipid A acylation to Salmonella pathogenesis.

scholarly journals Association of a Protective Monoclonal IgA with the O Antigen of Salmonella enterica Serovar Typhimurium Impacts Type 3 Secretion and Outer Membrane Integrity

2012 ◽  
Vol 80 (7) ◽  
pp. 2454-2463 ◽  
Author(s):  
Stephen J. Forbes ◽  
Daniel Martinelli ◽  
Chyongere Hsieh ◽  
Jeffrey G. Ault ◽  
Michael Marko ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Membrane Integrity ◽  
Effector Proteins ◽  
Content Type ◽  
O Antigen ◽  
Serovar Typhimurium ◽  
Type 3

ABSTRACTInvasion of intestinal epithelial cells bySalmonella entericaserovar Typhimurium is an energetically demanding process, involving the transfer of effector proteins from invading bacteria into host cells via a specialized organelle known as theSalmonellapathogenicity island 1 (SPI-1) type 3 secretion system (T3SS). By a mechanism that remains poorly understood, entry ofS. Typhimurium into epithelial cells is inhibited by Sal4, a monoclonal, polymeric IgA antibody that binds an immunodominant epitope within the O-antigen (O-Ag) component of lipopolysaccharide. In this study, we investigated how the binding of Sal4 to the surface ofS. Typhimurium influences T3SS activity, bacterial energetics, and outer membrane integrity. We found that Sal4 treatment impaired T3SS-mediated translocon formation and attenuated the delivery of tagged effector proteins into epithelial cells. Sal4 treatment coincided with a partial reduction in membrane energetics and intracellular ATP levels, possibly explaining the impairment in T3SS activity. Sal4's effects on bacterial secretion and energetics occurred concurrently with an increase in O-Ag levels in culture supernatants, alterations in outer membrane permeability, and changes in surface ultrastructure, as revealed by transmission electron microscopy and cryo-electron microscopy. We propose that Sal4, by virtue of its ability to bind and cross-link the O-Ag, induces a form of outer membrane stress that compromises the integrity of theS. Typhimurium cell envelope and temporarily renders the bacterium avirulent.

scholarly journals Display of Recombinant Proteins on Bacterial Outer Membrane Vesicles by Using Protein Ligation

2018 ◽  
Vol 84 (8) ◽  
pp. e02567-17 ◽  
Author(s):  
H. Bart van den Berg van Saparoea ◽  
Diane Houben ◽  
Marien I. de Jonge ◽  
Wouter S. P. Jong ◽  
Joen Luirink
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Membrane Vesicles ◽  
Therapeutic Agents ◽  
Outer Membrane Vesicles ◽  
High Density ◽  
Content Type ◽  
Protein Ligation ◽  
Serovar Typhimurium

ABSTRACT The Escherichia coli virulence factor hemoglobin protease (Hbp) has been engineered into a surface display system that can be expressed to high density on live E. coli and Salmonella enterica serovar Typhimurium cells or derived outer membrane vesicles (OMVs). Multiple antigenic sequences can be genetically fused into the Hbp core structure for optimal exposure to the immune system. Although the Hbp display platform is relatively tolerant, increasing the number, size, and complexity of integrated sequences generally lowers the expression of the fused constructs and limits the density of display. This is due to the intricate mechanism of Hbp secretion across the outer membrane and the efficient quality control of translocation-incompetent chimeric Hbp molecules in the periplasm. To address this shortcoming, we explored the coupling of purified proteins to the Hbp carrier after its translocation across the outer membrane using the recently developed SpyTag/SpyCatcher protein ligation system. As expected, fusion of the small SpyTag to Hbp did not hamper display on OMVs. Subsequent addition of purified proteins fused to the SpyCatcher domain resulted in efficient covalent coupling to Hbp-SpyTag. Using in addition the orthogonal SnoopTag/SnoopCatcher system, multiple antigen modules could be coupled to Hbp in a sequential ligation strategy. Not only antigens proved suitable for Spy-mediated ligation but also nanobodies. Addition of this functionality to the platform might allow the targeting of live bacterial or OMV vaccines to certain tissues or immune cells to tailor immune responses.IMPORTANCE Outer membrane vesicles (OMVs) derived from Gram-negative bacteria attract increasing interest in the development of vaccines and therapeutic agents. We aim to construct a semisynthetic OMV platform for recombinant antigen presentation on OMVs derived from attenuated Salmonella enterica serovar Typhimurium cells displaying an adapted Escherichia coli autotransporter, Hbp, at the surface. Although this autotransporter accepts substantial modifications, its capacity with respect to the number, size, and structural complexity of the antigens genetically fused to the Hbp carrier is restricted. Here we describe the application of SpyCatcher/SpyTag protein ligation technology to enzymatically link antigens to Hbp present at high density in OMVs. Protein ligation was apparently unobstructed by the membrane environment and allowed a high surface density of coupled antigens, a property we have shown to be important for vaccine efficacy. The OMV coupling procedure appears versatile and robust, allowing fast production of experimental vaccines and therapeutic agents through a modular plug-and-display procedure.

scholarly journals Salmonella enterica Serovar Typhimurium Uses PbgA/YejM To Regulate Lipopolysaccharide Assembly during Bacteremia

2019 ◽  
Vol 88 (1) ◽  
Author(s):  
Melina B. Cian ◽  
Nicole P. Giordano ◽  
Revathi Masilamani ◽  
Keaton E. Minor ◽  
Zachary D. Dalebroux
Keyword(s):  
Salmonella Enterica ◽  
Lipid A ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Transmembrane Domain ◽  
Wild Type ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Periplasmic Domain ◽  
Inner Membrane Protein ◽  
Substitution Mutations

ABSTRACT Salmonella enterica serovar Typhimurium (S. Typhimurium) relies upon the inner membrane protein PbgA to enhance outer membrane (OM) integrity and promote virulence in mice. The PbgA transmembrane domain (residues 1 to 190) is essential for viability, while the periplasmic domain (residues 191 to 586) is dispensable. Residues within the basic region (residues 191 to 245) bind acidic phosphates on polar phospholipids, like for cardiolipins, and are necessary for salmonella OM integrity. S. Typhimurium bacteria increase their OM cardiolipin concentrations during activation of the PhoPQ regulators. The mechanism involves PbgA’s periplasmic globular region (residues 245 to 586), but the biological role of increasing cardiolipins on the surface is not understood. Nonsynonymous polymorphisms in three essential lipopolysaccharide (LPS) synthesis regulators, lapB (also known as yciM), ftsH, and lpxC, variably suppressed the defects in OM integrity, rifampin resistance, survival in macrophages, and systemic colonization of mice in the pbgAΔ191–586 mutant (in which the PbgA periplasmic domain from residues 191 to 586 is deleted). Compared to the OMs of the wild-type salmonellae, the OMs of the pbgA mutants had increased levels of lipid A-core molecules, cardiolipins, and phosphatidylethanolamines and decreased levels of specific phospholipids with cyclopropanated fatty acids. Complementation and substitution mutations in LapB and LpxC generally restored the phospholipid and LPS assembly defects for the pbgA mutants. During bacteremia, mice infected with the pbgA mutants survived and cleared the bacteria, while animals infected with wild-type salmonellae succumbed within 1 week. Remarkably, wild-type mice survived asymptomatically with pbgA-lpxC salmonellae in their livers and spleens for months, but Toll-like receptor 4-deficient animals succumbed to these infections within roughly 1 week. In summary, S. Typhimurium uses PbgA to influence LPS assembly during stress in order to survive, adapt, and proliferate within the host environment.

scholarly journals Global Transcriptional Analysis of Dehydrated Salmonella enterica Serovar Typhimurium

2012 ◽  
Vol 78 (22) ◽  
pp. 7866-7875 ◽  
Author(s):  
Nadia Gruzdev ◽  
Michael McClelland ◽  
Steffen Porwollik ◽  
Shany Ofaim ◽  
Riky Pinto ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Lipid A ◽  
Isocitrate Lyase ◽  
Protein Biosynthesis ◽  
Potassium Transport ◽  
Transcriptional Analysis ◽  
Scaffolding Protein ◽  
Transport Channel ◽  
Content Type ◽  
Serovar Typhimurium

ABSTRACTDespite the scientific and industrial importance of desiccation tolerance inSalmonella, knowledge regarding its genetic basis is still scarce. In the present study, we performed a transcriptomic analysis of dehydrated and water-suspendedSalmonella entericaserovar Typhimurium using microarrays. Dehydration induced expression of 90 genes and downregulated that of 7 genes. Ribosomal structural genes represented the most abundant functional group with a relatively higher transcription during dehydration. Other main induced functional groups included genes involved in amino acid metabolism, energy production, ion transport, transcription, and stress response. The highest induction was observed in thekdpFABCoperon, encoding a potassium transport channel. Knockout mutations were generated in nine upregulated genes. Five mutants displayed lower tolerance to desiccation, implying the involvement of the corresponding genes in the adaptation ofSalmonellato desiccation. These included genes encoding the isocitrate-lyase AceA, the lipid A biosynthesis palmitoleoyl-acyltransferase Ddg, the modular iron-sulfur cluster scaffolding protein NifU, the global regulator Fnr, and the alternative sigma factor RpoE. Notably, these proteins were previously implicated in the response ofSalmonellato oxidative stress, heat shock, and cold shock. A strain with a mutation in the structural genekdpAhad a tolerance to dehydration comparable to that of the parent strain, implying that potassium transport through this system is dispensable for early adaptation to the dry environment. Nevertheless, this mutant was significantly impaired in long-term persistence during cold storage. Our findings indicate the involvement of a relatively small fraction of theSalmonellagenome in transcriptional adjustment from water to dehydration, with a high prevalence of genes belonging to the protein biosynthesis machinery.

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