TITLE:
Extracellular DNA Plays an Important Structural Role in the Biofilm of the Plastic Degrading Actinomycete Rhodo-coccus ruber
AUTHORS:
Irit Gilan, Alex Sivan
KEYWORDS:
Biofilm; Extracellular DNA; DNase; RNase; RAPD-PCR
JOURNAL NAME:
Advances in Microbiology,
Vol.3 No.8,
December
12,
2013
ABSTRACT:
Biofilms, the preferred bacterial mode of living and survival, are employed
by most microorganisms—which tend to attach to surfaces—to gain physical support,
increase nutrient utilization and availability, and augment their resistance against
anti-bacterial agents. Rhodococcus ruber (C208) has been shown to form a
dense biofilm on polyethylene surfaces while degrading them. Bacterial biofilms
comprise bacterial cells embedded in self-secreted extracellular polymeric substances
(EPS) whose main components are polysaccharides, proteins and nucleic acids. Revealing
the roles of these components will enable further insight into biofilm development
and, therefore, the EPS structure-function relationship. The current study focuses
on contribution of extracellular DNA to biofilm formation and stability. This was
approached by investigating the influence of nucleases on biofilm formation via
degradation of their corresponding substrates within the biofilm of C208. RNase
application to cultures of C208 decreased biofilm formation. Degradation of biofilm
DNA by DNase reduced early-stage biofilm formation by 20% -25% but
had no significant effect on established, mature biofilm. Likewise, the addition
of DNA to cultures significantly enhanced early-stage biofilm formation by 50% -100%. RAPD-PCR
analysis revealed different band patterns from intra-cellular DNA and extra-cellular
DNA and also between the supernatant and biofilm fractions of extra-cellular DNA,
indicating that perhaps only certain DNA molecules are utilized as part of the biofilm.