Temporal expression ofagrB,cidA, andalsSin the early development ofStaphylococcus aureusUAMS-1 biofilm formation and the structural role of extracellular DNA and carbohydrates

Grande, Rossella; Nistico, Laura; Sambanthamoorthy, Karthik; Longwell, Mark; Iannitelli, Antonio; Cellini, Luigina; Stefano, Antonio Di; Stoodley, Luanne Hall; Stoodley, Paul

doi:10.1111/2049-632x.12158

Cited by 40 publications

(34 citation statements)

References 53 publications

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“…To gain a better understanding of the contribution of eDNA during early biofilm development under the flow cell conditions used in the present study, we added exogenous DNase I (0.5 U ml −1 ) at various time points (2-h intervals) during the biofilm attachment and multiplication phases. Similar to a recent study demonstrating DNase I insensitivity during early biofilm development ( 24 ), the addition of DNase I had no effect on the biofilm through 8 h of growth ( Fig. 2A ), suggesting that the initial attachment and multiplication stages lack eDNA under these conditions or that the eDNA present in the matrix during this time is insensitive to DNase I treatment.…”

Section: Resultssupporting

confidence: 87%

Temporal and Stochastic Control of Staphylococcus aureus Biofilm Development

Moormeier

Bose

Horswill

et al. 2014

mBio

157

167

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Biofilm communities contain distinct microniches that result in metabolic heterogeneity and variability in gene expression. Previously, these niches were visualized within Staphylococcus aureus biofilms by observing differential expression of the cid and lrg operons during tower formation. In the present study, we examined early biofilm development and identified two new stages (designated “multiplication” and “exodus”) that were associated with changes in matrix composition and a distinct reorganization of the cells as the biofilm matured. The initial attachment and multiplication stages were shown to be protease sensitive but independent of most cell surface-associated proteins. Interestingly, after 6 h of growth, an exodus of the biofilm population that followed the transition of the biofilm to DNase I sensitivity was demonstrated. Furthermore, disruption of the gene encoding staphylococcal nuclease (nuc) abrogated this exodus event, causing hyperproliferation of the biofilm and disrupting normal tower development. Immediately prior to the exodus event, S. aureus cells carrying a nuc::gfp promoter fusion demonstrated Sae-dependent expression but only in an apparently random subpopulation of cells. In contrast to the existing model for tower development in S. aureus, the results of this study suggest the presence of a Sae-controlled nuclease-mediated exodus of biofilm cells that is required for the development of tower structures. Furthermore, these studies indicate that the differential expression of nuc during biofilm development is subject to stochastic regulatory mechanisms that are independent of the formation of metabolic microniches.

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Section: Resultssupporting

confidence: 87%

Temporal and Stochastic Control of Staphylococcus aureus Biofilm Development

Moormeier

Bose

Horswill

et al. 2014

mBio

157

167

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“…Expression of lrgAB is induced by the LytSR two-component system, which senses a reduction in the membrane potential (⌬⌿) (69). Although in an earlier study a cidA mutant in S. aureus UAMS-1 exhibited decreased lysis resulting in smaller amounts of eDNA and impaired biofilm formation (22,24), the LAC cidA mutant showed the same biofilm phenotype as the wt strain in our biofilm model after 18 h. Transcription of cidA in UAMS-1 biofilms steadily increased over time (up to 90-fold after 72 h) (70). Therefore, its effect on biofilm formation might play only a minor role in our 18-h-old biofilm system while LrgAB might be activated by changes in the membrane potential at an earlier time point.…”

Section: Discussionmentioning

confidence: 55%

Modulation of Staphylococcus aureus Biofilm Matrix by Subinhibitory Concentrations of Clindamycin

Schilcher

Andreoni

Haunreiter

et al. 2016

Antimicrob Agents Chemother

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Staphylococcus aureus biofilms are extremely difficult to treat. They provide a protected niche for the bacteria, rendering them highly recalcitrant toward host defenses as well as antibiotic treatment. Bacteria within a biofilm are shielded from the immune system by the formation of an extracellular polymeric matrix, composed of polysaccharides, extracellular DNA (eDNA), and proteins. Many antibiotics do not readily penetrate biofilms, resulting in the presence of subinhibitory concentrations of antibiotics. Here, we show that subinhibitory concentrations of clindamycin triggered a transcriptional stress response in S. aureus via the alternative sigma factor B ( B ) and upregulated the expression of the major biofilm-associated genes atlA, lrgA, agrA, the psm genes, fnbA, and fnbB. Our data suggest that subinhibitory concentrations of clindamycin alter the ability of S. aureus to form biofilms and shift the composition of the biofilm matrix toward higher eDNA content. An understanding of the molecular mechanisms underlying biofilm assembly and dispersal in response to subinhibitory concentrations of clinically relevant antibiotics such as clindamycin is critical to further optimize antibiotic treatment strategies of biofilm-associated S. aureus infections. Staphylococcus aureus is a major cause of both health care-related and community-associated (CA) infections. The Grampositive human-pathogenic bacterium produces and secretes a range of toxins and enzymes leading to acute infections such as bacteremia and skin abscesses (1, 2). In addition, most S. aureus strains are capable of biofilm formation and can persist in host tissues such as the bone, leading to chronic osteomyelitis, or on implanted medical devices such as vascular catheters, vascular grafts, heart valves, and prosthetic joints (3-5). Biofilm-associated infections are extremely difficult to treat, and these chronic or relapsing infections typically require prolonged antibiotic treatment or removal of the device (6-8). Antibiotic resistance of bacteria within a biofilm may result from slow growth, phenotypic heterogeneity, persister cell formation, and inactivation or reduced penetration of the antibiotic (9, 10). Diffusion of the antibiotic through biofilm cell clusters is dependent on the thickness and the composition of the extracellular polymeric matrix (9, 11). The slow transport within biofilms suggests that the bacteria may encounter subinhibitory concentrations of antibiotics. Previous studies have shown that low doses of different antibiotics trigger biofilm formation (12, 13) and lead to dramatic alterations in bacterial gene expression in S. aureus (14).Biofilm formation proceeds in at least three phases: initial attachment, biofilm maturation, and dispersal (15, 16). Initial surface attachment is dependent on bacterial surface molecules such as the S. aureus murein hydrolase AtlA, teichoic acids, and fibronectin-binding proteins (FnBPs) (17)(18)(19)(20). After attachment to the surface, the bacteria multiply and produce the extracellular...

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“…The ORFs include genes required for adhesion (fimC), iron sequestration (feo and fec family members), nickel transport (nikR), two-component systems, anaerobic growth (dmsABC, frdC, and adhE), and lipid A (arnACT) and outer membrane production (wecFG, wbbM, and wzyE) (53)(54)(55)(56)(57)(58)(59). Sublethal antibiotics have also been implicated in altered biofilm formation in P. aeruginosa, E. coli, and S. aureus (60,61) and we observed the differential gene expression of a number of biofilm-related ORFs, including cidA, ariR, mlrA, bssR, and cysB (62)(63)(64)(65)(66). As biofilm formation is yet another important virulence factor for K. pneumoniae and other bacteria, altering biofilms with sublethal concentrations of carbapenems may have positive effects on decreasing virulence potential.…”

Section: Discussionmentioning

confidence: 64%

Sublethal Concentrations of Carbapenems Alter Cell Morphology and Genomic Expression of Klebsiella pneumoniae Biofilms

Laar

Chen²,

You

et al. 2015

Antimicrob Agents Chemother

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b Klebsiella pneumoniae, a Gram-negative bacterium, is normally associated with pneumonia in patients with weakened immune systems. However, it is also a prevalent nosocomial infectious agent that can be found in infected surgical sites and combat wounds. Many of these clinical strains display multidrug resistance. We have worked with a clinical strain of K. pneumoniae that was initially isolated from a wound of an injured soldier. This strain demonstrated resistance to many commonly used antibiotics but sensitivity to carbapenems. This isolate was capable of forming biofilms in vitro, contributing to its increased antibiotic resistance and impaired clearance. We were interested in determining how sublethal concentrations of carbapenem treatment specifically affect K. pneumoniae biofilms both in morphology and in genomic expression. Scanning electron microscopy showed striking morphological differences between untreated and treated biofilms, including rounding, blebbing, and dimpling of treated cells. Comparative transcriptome analysis using RNA sequencing (RNA-Seq) technology identified a large number of open reading frames (ORFs) differentially regulated in response to carbapenem treatment at 2 and 24 h. ORFs upregulated with carbapenem treatment included genes involved in resistance, as well as those coding for antiporters and autoinducers. ORFs downregulated included those coding for metal transporters, membrane biosynthesis proteins, and motility proteins. Quantitative real-time PCR validated the general trend of some of these differentially regulated ORFs. Treatment of K. pneumoniae biofilms with sublethal concentrations of carbapenems induced a wide range of phenotypic and gene expression changes. This study reveals some of the mechanisms underlying how sublethal amounts of carbapenems could affect the overall fitness and pathogenic potential of K. pneumoniae biofilm cells.

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Temporal expression ofagrB,cidA, andalsSin the early development ofStaphylococcus aureusUAMS-1 biofilm formation and the structural role of extracellular DNA and carbohydrates

Cited by 40 publications

References 53 publications

Temporal and Stochastic Control of Staphylococcus aureus Biofilm Development

Temporal and Stochastic Control of Staphylococcus aureus Biofilm Development

Modulation of Staphylococcus aureus Biofilm Matrix by Subinhibitory Concentrations of Clindamycin

Sublethal Concentrations of Carbapenems Alter Cell Morphology and Genomic Expression of Klebsiella pneumoniae Biofilms

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