Exposure of Salmonella enterica Serovar Typhimurium to a Protective Monoclonal IgA Triggers Exopolysaccharide Production via a Diguanylate Cyclase-Dependent Pathway

ABSTRACTSal4 is a monoclonal polymeric IgA antibody directed against the O antigen (O-Ag) ofSalmonella entericaserovar Typhimurium (S. Typhimurium), which is sufficient to protect mice against intestinal infections fromS. Typhimurium. We recently reported that the exposure ofS. Typhimurium to Sal4 results in the immediate loss of flagellum-based motility, in alterations to the outer membrane (OM) integrity, and in the concomitant appearance of a mucoid phenotype that is reminiscent of cells in the earliest stages of biofilm formation. We demonstrate here that prolonged (>4 h) exposure ofS. Typhimurium to Sal4 at 37°C (but not at ambient temperature [25°C]) results in measurable exopolysaccharide (EPS) accumulation and biofilm formation on both borosilicate glass surfaces and polystyrene microtiter plates. The polysaccharide produced byS. Typhimurium in response to Sal4 contains cellulose, in addition to O-Ag capsule and colanic acid. EPS production was dependent on YeaJ, a proposed inner membrane-localized diguanylate cyclase (DGC) and a known regulator of cellulose biosynthesis. AnS. Typhimurium ΔyeaJstrain was unable to produce cellulose or form a biofilm in response to Sal4. Conversely, the overexpression ofyeaJinS. Typhimurium enhanced Sal4-induced biofilm formation and resulted in increased intracellular levels of cyclic dimeric guanosine monophosphate (c-di-GMP) compared to that of a wild-type control; this strongly suggests that YeaJ is indeed a functional DGC. Based on these data, we speculate that Sal4, by virtue of its ability to associate with the O-Ag and to induce OM stress, rendersS. Typhimurium avirulent by triggering a c-di-GMP-dependent signaling pathway via YeaJ that leads to the suppression of bacterial motility while simultaneously stimulating EPS production.

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Comparative Analysis of Salmonella enterica Serovar Typhimurium Biofilm Formation on Gallstones and on Glass

Infection and Immunity ◽

10.1128/iai.71.12.7154-7158.2003 ◽

2003 ◽

Vol 71 (12) ◽

pp. 7154-7158 ◽

Cited By ~ 106

Author(s):

A. M. Prouty ◽

J. S. Gunn

Keyword(s):

Comparative Analysis ◽

Culture Condition ◽

Salmonella Enterica ◽

Biofilm Formation ◽

Salmonella Enterica Serovar Typhimurium ◽

Complex Nature ◽

Global Regulators ◽

Serovar Typhimurium ◽

Glass Surfaces

ABSTRACT In this study, the roles of global regulators, motility, lipopolysaccharide, and exopolysaccharides were further characterized with respect to biofilm formation on both gallstones and glass surfaces. These studies show the complex nature of biofilms and demonstrate that characteristics observed for each biofilm are unique to the particular culture condition.

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The Acyl Homoserine Lactone Receptor, SdiA, of Escherichia coli and Salmonella enterica Serovar Typhimurium Does Not Respond to Indole

Applied and Environmental Microbiology ◽

10.1128/aem.00046-12 ◽

2012 ◽

Vol 78 (15) ◽

pp. 5424-5431 ◽

Cited By ~ 29

Author(s):

Anice Sabag-Daigle ◽

Jitesh A. Soares ◽

Jenée N. Smith ◽

Mohamed E. Elmasry ◽

Brian M. M. Ahmer

Keyword(s):

Escherichia Coli ◽

Salmonella Enterica ◽

Biofilm Formation ◽

Salmonella Enterica Serovar Typhimurium ◽

Homoserine Lactone ◽

Acyl Homoserine Lactone ◽

Content Type ◽

E Coli ◽

Serovar Typhimurium ◽

High Concentrations

ABSTRACTIn this study, we tested the hypothesis that the SdiA proteins ofEscherichia coliandSalmonella entericaserovar Typhimurium respond to indole. While indole was found to have effects on gene expression and biofilm formation, these effects were notsdiAdependent. However, high concentrations of indole did inhibitN-acyl-l-homoserine lactone (AHL) sensing by SdiA. We conclude that SdiA does not respond to indole but indole can inhibit SdiA activity inE. coliandSalmonella.

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Regulation of RamA by RamR in Salmonella enterica Serovar Typhimurium: Isolation of a RamR Superrepressor

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01320-12 ◽

2012 ◽

Vol 56 (11) ◽

pp. 6037-6040 ◽

Cited By ~ 15

Author(s):

Vito Ricci ◽

Stephen J. W. Busby ◽

Laura J. V. Piddock

Keyword(s):

Transcription Factor ◽

Salmonella Enterica ◽

Fluorescent Protein ◽

Salmonella Enterica Serovar Typhimurium ◽

Promoter Sequence ◽

Palindromic Sequence ◽

Content Type ◽

Gfp Reporter ◽

Serovar Typhimurium ◽

Green Fluorescent

ABSTRACTRamA is a transcription factor involved in regulating multidrug resistance inSalmonella entericaserovar Typhimurium SL1344. Green fluorescent protein (GFP) reporter fusions were exploited to investigate the regulation of RamA expression by RamR. We show that RamR represses theramApromoter by binding to a palindromic sequence and describe a superrepressor RamR mutant that binds to theramApromoter sequence more efficiently, thus exhibiting aramAinactivated phenotype.

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

Infection and Immunity ◽

10.1128/iai.00758-19 ◽

2019 ◽

Vol 88 (1) ◽

Cited By ~ 16

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.

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Clarithromycin Exerts an Antibiofilm Effect against Salmonella enterica Serovar Typhimurium rdar Biofilm Formation and Transforms the Physiology towards an Apparent Oxygen-Depleted Energy and Carbon Metabolism

Infection and Immunity ◽

10.1128/iai.00510-20 ◽

2020 ◽

Vol 88 (11) ◽

Author(s):

Munirah Zafar ◽

Humera Jahan ◽

Sulman Shafeeq ◽

Manfred Nimtz ◽

Lothar Jänsch ◽

...

Keyword(s):

Antimicrobial Resistance ◽

Salmonella Enterica ◽

Biofilm Formation ◽

Antibiofilm Activity ◽

Bacterial Cells ◽

Content Type ◽

Regulatory Pathways ◽

Heat Shock Stress ◽

Extracellular Matrix Components ◽

Serovar Typhimurium

ABSTRACT Upon biofilm formation, production of extracellular matrix components and alteration in physiology and metabolism allows bacteria to build up multicellular communities which can facilitate nutrient acquisition during unfavorable conditions and provide protection toward various forms of environmental stresses to individual cells. Thus, bacterial cells within biofilms become tolerant against antimicrobials and the immune system. In the present study, we evaluated the antibiofilm activity of the macrolides clarithromycin and azithromycin. Clarithromycin showed antibiofilm activity against rdar (red, dry, and rough) biofilm formation of the gastrointestinal pathogen Salmonella enterica serovar Typhimurium ATCC 14028 (Nalr) at a 1.56 μM subinhibitory concentration in standing culture and dissolved cell aggregates at 15 μM in a microaerophilic environment, suggesting that the oxygen level affects the activity of the drug. Treatment with clarithromycin significantly decreased transcription and production of the rdar biofilm activator CsgD, with biofilm genes such as csgB and adrA to be concomitantly downregulated. Although fliA and other flagellar regulon genes were upregulated, apparent motility was downregulated. RNA sequencing showed a holistic cell response upon clarithromycin exposure, whereby not only genes involved in the biofilm-related regulatory pathways but also genes that likely contribute to intrinsic antimicrobial resistance, and the heat shock stress response were differentially regulated. Most significantly, clarithromycin exposure shifted the cells toward an apparent oxygen- and energy-depleted status, whereby the metabolism that channels into oxidative phosphorylation was downregulated, and energy gain by degradation of propane 1,2-diol, ethanolamine and l-arginine catabolism, potentially also to prevent cytosolic acidification, was upregulated. This analysis will allow the subsequent identification of novel intrinsic antimicrobial resistance determinants.

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Facultative Anaerobes Shape Multispecies Biofilms Composed of Meat Processing Surface Bacteria and Escherichia coli O157:H7 or Salmonella enterica Serovar Typhimurium

Applied and Environmental Microbiology ◽

10.1128/aem.01123-19 ◽

2019 ◽

Vol 85 (17) ◽

Author(s):

Jeyachchandran Visvalingam ◽

Hui Wang ◽

Tim C. Ells ◽

Xianqin Yang

Keyword(s):

Food Processing ◽

Salmonella Enterica ◽

Biofilm Formation ◽

Single Species ◽

Meat Processing ◽

Content Type ◽

E Coli ◽

Facultative Anaerobes ◽

Serovar Typhimurium ◽

Multispecies Biofilms

ABSTRACT This study investigated the microbial dynamics in multispecies biofilms of Escherichia coli O157:H7 strain 1934 (O157) or Salmonella enterica serovar Typhimurium ATCC 14028 (ST) and 40 strains of meat processing surface bacteria (MPB). Biofilms of O157 or ST with/without MPB were developed on stainless steel coupons at 15°C for up to 6 days. Bacteria in suspensions (inoculum, days 2 and 6) and biofilms (days 2 and 6) were enumerated by plating. The composition of multispecies cultures was determined by 16S rRNA gene sequencing. In suspensions, levels of O157 and ST were ∼2 log higher in single-species than in multispecies cultures on both sampling days. ST was 3 log higher in single-species than in multispecies biofilms. A similar trend, though to a lesser extent, was observed for O157 in biofilms on day 2 but not on day 6. No difference (P > 0.05) in bacterial counts was noted for the two MPB-pathogen cocultures at any time during incubation. Bacterial diversity in multispecies cultures decreased with incubation time, irrespective of the pathogen or culture type. The changes in the relative abundance of MPB were similar for the two MPB-pathogen cocultures, though different interbacterial interactions were noted. Respective fractions of ST and O157 were 2.1% and 0.97% initially and then 0.10% and 0.07% on day 2, and 0.60% and 0.04% on day 6. The relative proportions of facultative anaerobes in both multispecies cultures were greater in both suspensions and biofilms than in the inoculum. Citrobacter, Hafnia, Aeromonas, and Carnobacterium predominated in biofilms but not always in the planktonic cultures. IMPORTANCE Results of this study demonstrate that Salmonella enterica serovar Typhimurium and E. coli O157:H7 can integrate into biofilms when cocultured with bacteria from meat plant processing surfaces. However, the degree of biofilm formation for both pathogens was substantially reduced in the presence of the competing microbiota, with S. Typhimurium more greatly affected than E. coli O157:H7. The expression of extracellular determinants such as curli and cellulose appears to be less important for biofilm formation of the pathogens in multispecies cultures than in monoculture. In contrast to previous reports regarding food processing surface bacteria, data collected here also demonstrate that facultative anaerobes may have a competitive edge over strict aerobes in establishing multispecies biofilms. It would be important to take into account the presence of background bacteria when evaluating the potential persistence of a pathogen in food processing facilities.

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SlyA and HilD Counteract H-NS-Mediated Repression on the ssrAB Virulence Operon of Salmonella enterica Serovar Typhimurium and Thus Promote Its Activation by OmpR

Journal of Bacteriology ◽

10.1128/jb.00530-18 ◽

2019 ◽

Vol 201 (8) ◽

Cited By ~ 3

Author(s):

María M. Banda ◽

Crispín Zavala-Alvarado ◽

Deyanira Pérez-Morales ◽

Víctor H. Bustamante

Keyword(s):

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Growth Conditions ◽

The Other ◽

Regulatory Mechanisms ◽

Two Component System ◽

Content Type ◽

Additive Action ◽

Serovar Typhimurium ◽

Bacterial Fitness

ABSTRACT H-NS-mediated repression of acquired genes and the subsequent adaptation of regulatory mechanisms that counteract this repression have played a central role in the Salmonella pathogenicity evolution. The Salmonella pathogenicity island 2 (SPI-2) is an acquired chromosomal region containing genes necessary for Salmonella enterica to colonize and replicate in different niches of hosts. The ssrAB operon, located in SPI-2, encodes the two-component system SsrA-SsrB, which positively controls the expression of the SPI-2 genes but also other many genes located outside SPI-2. Several regulators have been involved in the expression of ssrAB, such as the ancestral regulators SlyA and OmpR, and the acquired regulator HilD. In this study, we show how SlyA, HilD, and OmpR coordinate to induce the expression of ssrAB under different growth conditions. We found that when Salmonella enterica serovar Typhimurium is grown in nutrient-rich lysogeny broth (LB), SlyA and HilD additively counteract H-NS-mediated repression on ssrAB, whereas in N-minimal medium (N-MM), SlyA antagonizes H-NS-mediated repression on ssrAB independently of HilD. Interestingly, our results indicate that OmpR is required for the expression of ssrAB independently of the growth conditions, even in the absence of repression by H-NS. Therefore, our data support two mechanisms adapted for the expression of ssrAB under different growth conditions. One involves the additive action of SlyA and HilD, whereas the other involves SlyA, but not HilD, to counteract H-NS-mediated repression on ssrAB, thus favoring in both cases the activation of ssrAB by OmpR. IMPORTANCE The global regulator H-NS represses the expression of acquired genes and thus avoids possible detrimental effects on bacterial fitness. Regulatory mechanisms are adapted to induce expression of the acquired genes in particular niches to obtain a benefit from the information encoded in the foreign DNA, as for pathogenesis. Here, we show two mechanisms that were integrated for the expression of virulence genes in Salmonella Typhimurium. One involves the additive action of the regulators SlyA and HilD, whereas the other involves SlyA, but not HilD, to counteract H-NS-mediated repression on the ssrAB operon, thus favoring its activation by the OmpR regulator. To our knowledge, this is the first report involving the coordinated action of two regulators to counteract H-NS-mediated repression.

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Complete Genome Sequence of Salmonella enterica Serovar Typhimurium Siphophage Siskin

Microbiology Resource Announcements ◽

10.1128/mra.00188-19 ◽

2019 ◽

Vol 8 (18) ◽

Author(s):

Chandler O’Leary ◽

Yicheng Xie ◽

Rohit Kongari ◽

Jason J. Gill ◽

Mei Liu

Keyword(s):

Genome Sequence ◽

Complete Genome Sequence ◽

Salmonella Enterica ◽

Complete Genome ◽

Salmonella Enterica Serovar Typhimurium ◽

Content Type ◽

New Class ◽

Typhimurium Strain ◽

Serovar Typhimurium ◽

Lysis Cassette

Bacteriophage Siskin is a member of the χ-like siphovirus phage cluster that infects Salmonella enterica serovar Typhimurium strain LT2. Here, we report the complete 58,476-bp sequence of the Siskin genome, provide confirmation of its genomic termini, and describe a potentially new class of holins and endolysins found in the lysis cassette.

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Complete Genome Sequence of Salmonella enterica Serovar Typhimurium Siphophage Skate

Microbiology Resource Announcements ◽

10.1128/mra.00541-19 ◽

2019 ◽

Vol 8 (27) ◽

Author(s):

Matthew Rohren ◽

Yicheng Xie ◽

Chandler O’Leary ◽

Rohit Kongari ◽

Jason Gill ◽

...

Keyword(s):

Genome Sequence ◽

Complete Genome Sequence ◽

Salmonella Enterica ◽

Complete Genome ◽

Salmonella Enterica Serovar Typhimurium ◽

Foodborne Illnesses ◽

Gram Negative ◽

Content Type ◽

Typhimurium Strain ◽

Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium is a Gram-negative pathogen and a primary cause of foodborne illnesses worldwide. Here, we present the complete 47,393-bp genome sequence of the siphophage Skate, which was isolated against S. Typhimurium strain LT2.

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