Functional Specificity of Extracellular Nucleases of Shewanella oneidensis MR-1

Heun, Magnus; Binnenkade, Lucas; Kreienbaum, Maximilian; Thormann, Kai M.

doi:10.1128/aem.07895-11

Cited by 30 publications

(37 citation statements)

References 63 publications

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“…As indicated above, endA likely encodes a probable DNA-specific endonuclease I. Moreover, the deduced amino acid sequence of EndA shares ϳ50% identity to the periplasmic nucleases EndA from E. coli and Vvn from Vibrio vulnificus, as well as to the extracellular nucleases Dns from Vibrio cholerae and Aeromonas hydrophila, and EndA from Shewanella oneidensis MR-1 (52)(53)(54)(55)(56). In addition, Gnanadhas et al (44) reported that exposure of P. aeruginosa biofilms to L-methionine results in increased DNase activity in culture supernatants, with L-Met treatment coinciding with upregulated expression of four DNase genes (sbcB, endA, eddB, and recJ).…”

Section: Resultsmentioning

confidence: 89%

Pseudomonas aeruginosa Requires the DNA-Specific Endonuclease EndA To Degrade Extracellular Genomic DNA To Disperse from the Biofilm

Cherny

Sauer

2019

J Bacteriol

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The dispersion of biofilms is an active process resulting in the release of planktonic cells from the biofilm structure. While much is known about the process of dispersion cue perception and the subsequent modulation of the c-di-GMP pool, little is known about subsequent events resulting in the release of cells from the biofilm. Given that dispersion coincides with void formation and an overall erosion of the biofilm structure, we asked whether dispersion involves degradation of the biofilm matrix. Here, we focused on extracellular genomic DNA (eDNA) due to its almost universal presence in the matrix of biofilm-forming species. We identified two probable nucleases, endA and eddB, and eddA encoding a phosphatase that were significantly increased in transcript abundance in dispersed cells. However, only inactivation of endA but not eddA or eddB impaired dispersion by Pseudomonas aeruginosa biofilms in response to glutamate and nitric oxide (NO). Heterologously produced EndA was found to be secreted and active in degrading genomic DNA. While endA inactivation had little effect on biofilm formation and the presence of eDNA in biofilms, eDNA degradation upon induction of dispersion was impaired. In contrast, induction of endA expression coincided with eDNA degradation and resulted in biofilm dispersion. Thus, released cells demonstrated a hyperattaching phenotype but remained as resistant to tobramycin as biofilm cells from which they egress, indicating EndA-dispersed cells adopted some but not all of the phenotypes associated with dispersed cells. Our findings indicate for the first time a role of DNase EndA in dispersion and suggest weakening of the biofilm matrix is a requisite for biofilm dispersion. IMPORTANCE The finding that exposure to DNase I impairs biofilm formation or leads to the dispersal of early stage biofilms has led to the realization of extracellular genomic DNA (eDNA) as a structural component of the biofilm matrix. However, little is known about the contribution of intrinsic DNases to the weakening of the biofilm matrix and dispersion of established biofilms. Here, we demonstrate for the first time that nucleases are induced in dispersed Pseudomonas aeruginosa cells and are essential to the dispersion response and that degradation of matrix eDNA by endogenously produced/secreted EndA is required for P. aeruginosa biofilm dispersion. Our findings suggest that dispersing cells mediate their active release from the biofilm matrix via the induction of nucleases.

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Section: Resultsmentioning

confidence: 89%

Pseudomonas aeruginosa Requires the DNA-Specific Endonuclease EndA To Degrade Extracellular Genomic DNA To Disperse from the Biofilm

Cherny

Sauer

2019

J Bacteriol

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“…However, most studies attribute DNA breakdown to a suite of extracellular enzymes including phosphatase and nucleases. [40,41] Abiotic hydrolysis facilitated by mineral phases [42] is potentially an alternate pathway for the degradation of DNA in aquatic ecosystems -but it has not been demonstrated. The only abiotic degradation pathway that has been demonstrated to date is the breaking of DNA double strands induced by radiation from dissolved uranium.…”

Section: Quantificationmentioning

confidence: 99%

Organic phosphorus in the aquatic environment

Baldwin¹

2013

Environ. Chem.

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Environmental context. Organic phosphorus can be one of the major fractions of phosphorus in many aquatic ecosystems. This paper discusses the distribution, cycling and ecological significance of five major classes of organic P in the aquatic environment and discusses several principles to guide organic P research into the future.Abstract. Organic phosphorus can be one of the major fractions of phosphorus in many aquatic ecosystems. Unfortunately, in many studies the 'organic' P fraction is operationally defined. However, there are an increasing number of studies where the organic P species have been structurally characterised -in part because of the adoption of 31 P NMR spectroscopic techniques. There are five classes of organic P species that have been specifically identified in the aquatic environment -nucleic acids, other nucleotides, inositol phosphates, phospholipids and phosphonates. This paper explores the identification, quantification, biogeochemical cycling and ecological significance of these organic P compounds. Based on this analysis, the paper then identifies a number of principles which could guide the research of organic P into the future. There is an ongoing need to develop methods for quickly and accurately identifying and quantifying organic P species in the environment. The types of ecosystems in which organic P dynamics are studied needs to be expanded; flowing waters, floodplains and small wetlands are currently all under-represented in the literature. While enzymatic hydrolysis is an important transformation pathway for the breakdown of organic P, more effort needs to be directed towards studying other potential transformation pathways. Similarly effort should be directed to estimating the rates of transformations, not simply reporting on the concentrations. And finally, further work is needed in elucidating other roles of organic P in the environment other than simply a source of P to aquatic organisms.

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“…eDNA was initially thought to be mainly residual debris of lysed cells; however, a number of recent studies clearly showed that this compound constitutes an important structural component of the biofilm matrix for many bacterial species (4)(5)(6)(7)(8)(9)(10). Additionally, eDNA can serve as a source of phosphorus, carbon, and nitrogen (11,12), provide a genetic pool for horizontal gene transfer (13), exhibit antimicrobial activity (14), induce antibiotic resistance (14,15), and facilitate twitching motility-mediated biofilm expansion (16). The origin of eDNA in biofilms has been a focus of numerous studies.…”

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confidence: 99%

Iron Triggers λSo Prophage Induction and Release of Extracellular DNA in Shewanella oneidensis MR-1 Biofilms

Binnenkade

Teichmann

Thormann

2014

Appl Environ Microbiol

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bProphages are ubiquitous elements within bacterial chromosomes and affect host physiology and ecology in multiple ways. We have previously demonstrated that phage-induced lysis is required for extracellular DNA (eDNA) release and normal biofilm formation in Shewanella oneidensis MR-1. Here, we investigated the regulatory mechanisms of prophage So spatiotemporal induction in biofilms. To this end, we used a functional fluorescence fusion to monitor So activation in various mutant backgrounds and in response to different physiological conditions. So induction occurred mainly in a subpopulation of filamentous cells in a strictly RecA-dependent manner, implicating oxidative stress-induced DNA damage as the major trigger. Accordingly, mutants affected in the oxidative stress response (⌬oxyR) or iron homeostasis (⌬fur) displayed drastically increased levels of phage induction and abnormal biofilm formation, while planktonic cells were not or only marginally affected. To further investigate the role of oxidative stress, we performed a mutant screen and identified two independent amino acid substitutions in OxyR (T104N and L197P) that suppress induction of So by hydrogen peroxide (H 2 O 2 ). However, So induction was not suppressed in biofilms formed by both mutants, suggesting a minor role of intracellular H 2 O 2 in this process. In contrast, addition of iron to biofilms strongly enhanced So induction and eDNA release, while both processes were significantly suppressed at low iron levels, strongly indicating that iron is the limiting factor. We conclude that uptake of iron during biofilm formation triggers So-mediated lysis of a subpopulation of cells, likely by an increase in iron-mediated DNA damage sensed by RecA.

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Functional Specificity of Extracellular Nucleases of Shewanella oneidensis MR-1

Cited by 30 publications

References 63 publications

Pseudomonas aeruginosa Requires the DNA-Specific Endonuclease EndA To Degrade Extracellular Genomic DNA To Disperse from the Biofilm

Pseudomonas aeruginosa Requires the DNA-Specific Endonuclease EndA To Degrade Extracellular Genomic DNA To Disperse from the Biofilm

Organic phosphorus in the aquatic environment

Iron Triggers λSo Prophage Induction and Release of Extracellular DNA in Shewanella oneidensis MR-1 Biofilms

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