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Influence of calcium in extracellular DNA mediated bacterial aggregation and biofilm formation.

ABSTRACT: Calcium (Ca(2+)) has an important structural role in guaranteeing the integrity of the outer lipopolysaccharide layer and cell walls of bacterial cells. Extracellular DNA (eDNA) being part of the slimy matrix produced by bacteria promotes biofilm formation through enhanced structural integrity of the matrix. Here, the concurrent role of Ca(2+) and eDNA in mediating bacterial aggregation and biofilm formation was studied for the first time using a variety of bacterial strains and the thermodynamics of DNA to Ca(2+) binding. It was found that the eDNA concentrations under both planktonic and biofilm growth conditions were different among bacterial strains. Whilst Ca(2+) had no influence on eDNA release, presence of eDNA by itself favours bacterial aggregation via attractive acid-base interactions in addition, its binding with Ca(2+) at biologically relevant concentrations was shown further increase in bacterial aggregation via cationic bridging. Negative Gibbs free energy (?G) values in iTC data confirmed that the interaction between DNA and Ca(2+) is thermodynamically favourable and that the binding process is spontaneous and exothermic owing to its highly negative enthalpy. Removal of eDNA through DNase I treatment revealed that Ca(2+) alone did not enhance cell aggregation and biofilm formation. This discovery signifies the importance of eDNA and concludes that existence of eDNA on bacterial cell surfaces is a key facilitator in binding of Ca(2+) to eDNA thereby mediating bacterial aggregation and biofilm formation.

SUBMITTER: Das T

PROVIDER: S-EPMC3961253 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Influence of calcium in extracellular DNA mediated bacterial aggregation and biofilm formation.

Das Theerthankar T Sehar Shama S Koop Leena L Wong Yie Kuan YK Ahmed Safia S Siddiqui Khawar Sohail KS Manefield Mike M

PloS one 20140320 3

Calcium (Ca(2+)) has an important structural role in guaranteeing the integrity of the outer lipopolysaccharide layer and cell walls of bacterial cells. Extracellular DNA (eDNA) being part of the slimy matrix produced by bacteria promotes biofilm formation through enhanced structural integrity of the matrix. Here, the concurrent role of Ca(2+) and eDNA in mediating bacterial aggregation and biofilm formation was studied for the first time using a variety of bacterial strains and the thermodynami ...[more]

PMID: 24651318

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Project description:Campylobacter jejuni is a microaerophilic bacterium and is believed to persist in a biofilm to antagonize environmental stress. This study investigated the influence of environmental conditions on the formation of C. jejuni biofilm. We report an extracellular DNA (eDNA)-mediated mechanism of biofilm formation in response to aerobic and starvation stress. The eDNA was determined to represent a major form of constitutional material of C. jejuni biofilms and to be closely associated with bacterial lysis. Deletion mutation of the stress response genes spoT and recA enhanced the aerobic influence by stimulating lysis and increasing eDNA release. Flagella were also involved in biofilm formation but mainly contributed to attachment rather than induction of lysis. The addition of genomic DNA from either Campylobacter or Salmonella resulted in a concentration-dependent stimulation effect on biofilm formation, but the effect was not due to forming a precoating DNA layer. Enzymatic degradation of DNA by DNase I disrupted C. jejuni biofilm. In a dual-species biofilm, eDNA allocated Campylobacter and Salmonella at distinct spatial locations that protect Campylobacter from oxygen stress. Our findings demonstrated an essential role and multiple functions of eDNA in biofilm formation of C. jejuni, including facilitating initial attachment, establishing and maintaining biofilm, and allocating bacterial cells.IMPORTANCECampylobacter jejuni is a major cause of foodborne illness worldwide. In the natural environment, the growth of C. jejuni is greatly inhibited by various forms of environmental stress, such as aerobic stress and starvation stress. Biofilm formation can facilitate the distribution of C. jejuni by enabling the survival of this fragile microorganism under unfavorable conditions. However, the mechanism of C. jejuni biofilm formation in response to environmental stress has been investigated only partially. The significance of our research is in identifying extracellular DNA released by bacterial lysis as a major form of constitution material that mediates the formation of C. jejuni biofilm in response to environmental stress, which enhances our understanding of the formation mechanism of C. jejuni biofilm. This knowledge can aid the development of intervention strategies to limit the distribution of C. jejuni.

Dataset Information

Influence of calcium in extracellular DNA mediated bacterial aggregation and biofilm formation.

Publications

Influence of calcium in extracellular DNA mediated bacterial aggregation and biofilm formation.

Similar Datasets

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