Accumulation of DNA in the exopolymeric matrix of activated sludge and bacterial cultures

Palmgren, Rikke; Nielsen, Per Halkjær

doi:10.2166/wst.1996.0555

Cited by 33 publications

(26 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Accordingly, we have shown that the creation of a reducing environment by the addition of DTT readily inactivates S. oneidensis EndA. Also present in S. oneidensis EndA are the aspartic acid and glutamic acid residues that are involved in binding a catalytic divalent metal ion (36 sludge in wastewater treatment plants (46). Substantial amounts of eDNA have also been observed in marine sediments, in which it may represent the major source of phosphorus (14)(15)(16)(17).…”

Section: Discussionmentioning

confidence: 99%

Functional Specificity of Extracellular Nucleases of Shewanella oneidensis MR-1

Heun

Binnenkade

Kreienbaum

et al. 2012

Appl Environ Microbiol

View full text Add to dashboard Cite

ABSTRACTBacterial species such asShewanella oneidensisMR-1 require extracellular nucleolytic activity for the utilization of extracellular DNA (eDNA) as a source of nutrients and for the turnover of eDNA as a structural matrix component during biofilm formation. We have previously characterized two extracellular nucleases ofS. oneidensisMR-1, ExeM and ExeS. Although both are involved in biofilm formation, they are not specifically required for the utilization of eDNA as a nutrient. Here we identified and characterized EndA, a third extracellular nuclease ofShewanella. The heterologously overproduced and purified protein was highly active and rapidly degraded linear and supercoiled DNAs of various origins. Divalent metal ions (Mg2+or Mn2+) were required for function.endAis cotranscribed withphoA, an extracellular phosphatase, and is not upregulated upon phosphostarvation. Deletion ofendAabolished both extracellular degradation of DNA byS. oneidensisMR-1 and the ability to use eDNA as a sole source of phosphorus. PhoA is not strictly required for the exploitation of eDNA as a nutrient. The activity of EndA prevents the formation of large cell aggregates during planktonic growth. However, in contrast to the findings for ExeM,endAdeletion had only minor effects on biofilm formation. The findings strongly suggest that the extracellular nucleases ofS. oneidensisexert specific functions required under different conditions.

show abstract

Section: Discussionmentioning

confidence: 99%

Functional Specificity of Extracellular Nucleases of Shewanella oneidensis MR-1

Heun

Binnenkade

Kreienbaum

et al. 2012

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…However, e-DNA occurs in sufficiently high quantities to raise some doubt. In fact, Palmgren and Nielsen reported in 1996 the accumulation of DNA in the EPS matrix of activated sludge and pure cultures of Pseudomonas putida (17). Allesen-Holm et al (1) found that in P. aeruginosa biofilms, the e-DNA is likely derived from whole genomic DNA.…”

mentioning

confidence: 99%

The EPS Matrix: The “House of Biofilm Cells”

2007

View full text Add to dashboard Cite

“…Concentrations vary among different environments, ranging from 2 g g Ϫ1 in dry soil (49) to up to 20 mg g Ϫ1 organic matter in activated sludge from wastewater treatment plants (51). The pool of eDNA provides a reservoir for horizontal gene transfer (45,68) and a valuable source of carbon, nitrogen, and, in particular, phosphorus (11,12,48,53).…”

mentioning

confidence: 99%

“…This matrix, which in many cases comprises the majority of the communities' biomass, consists of different biopolymers. It has previously been reported that eDNA is abundant in bacterial biofilms (19,51); in addition, polysaccharides and proteins are common components (18). Studies of Pseudomonas aeruginosa demonstrated that eDNA in the matrix is required for structural integrity during the early stages of biofilm formation (70).…”

mentioning

confidence: 99%

Roles of Two Shewanella oneidensis MR-1 Extracellular Endonucleases

Gödeke

Heun

Bubendorfer

et al. 2011

Appl Environ Microbiol

View full text Add to dashboard Cite

The dissimilatory iron-reducing bacterium Shewanella oneidensis MR-1 is capable of using extracellular DNA (eDNA) as the sole source of carbon, phosphorus, and nitrogen. In addition, we recently demonstrated that S. oneidensis MR-1 requires eDNA as a structural component during all stages of biofilm formation. In this study, we characterize the roles of two Shewanella extracellular endonucleases, ExeS and ExeM. While ExeS is likely secreted into the medium, ExeM is predicted to remain associated with the cell envelope. Both exeM and exeS are highly expressed under phosphate-limited conditions. Mutants lacking exeS and/or exeM exhibit decreased eDNA degradation; however, the capability of S. oneidensis MR-1 to use DNA as the sole source of phosphorus is only affected in mutants lacking exeM. Neither of the two endonucleases alleviates toxic effects of increased eDNA concentrations. The deletion of exeM and/or exeS significantly affects biofilm formation of S. oneidensis MR-1 under static conditions, and expression of exeM and exeS drastically increases during static biofilm formation. Under hydrodynamic conditions, a deletion of exeM leads to altered biofilms that consist of densely packed structures which are covered by a thick layer of eDNA. Based on these results, we hypothesize that a major role of ExeS and, in particular, ExeM of S. oneidensis MR-1, is to degrade eDNA as a matrix component during biofilm formation to improve nutrient supply and to enable detachment.

show abstract

Accumulation of DNA in the exopolymeric matrix of activated sludge and bacterial cultures

Cited by 33 publications

References 0 publications

Functional Specificity of Extracellular Nucleases of Shewanella oneidensis MR-1

Functional Specificity of Extracellular Nucleases of Shewanella oneidensis MR-1

The EPS Matrix: The “House of Biofilm Cells”

Roles of Two Shewanella oneidensis MR-1 Extracellular Endonucleases

Contact Info

Product

Resources

About