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|Title: ||The impact of microbial extracellular polymeric substances on sediment stability|
|Authors: ||Lubarsky, Helen V.|
|Supervisors: ||Paterson, David Maxwell|
|Issue Date: ||Jun-2011|
|Abstract: ||The main objective of this thesis is to investigate the impact of microbial extracellular
polymeric substances (EPS) on sediment stability and the related factors which influence
“biogenic stabilisation” as a basis to the prediction of sediment erosion and transport.
The ability to make direct and sensitive measurements of the physical properties of the
biofilm is a critical demand to further understanding of the overall biostabilisation
processes.Therefore, attention has been focused on developing a new technique, Magnetic
Particle Induction (MagPI) for measuring the adhesive properties of the biofilm. MagPI
determines the relative adhesive properties or “stickiness” of the test surface, whether a
biofilm, a sediment or other submerged material. The technique may have future
applications in physical, environmental and biomedical research.
Newly developed Magnetic Particle Induction(MagPI) and traditional techniques Cohesive
Strength Meter (CSM) for the determination of the adhesion/cohesion of the substratum
were used to assess the biostabilisation capacity of aquatic microorganisms. Whilst these
devices determine slightly different surface properties of the bed, they were found to
complement each other, increasing the range of measurements that could be made and
presented a strong correlation in the overlapping portion of the data.
It is recognized that microorganisms inhabiting natural sediments significantly mediate the
erosive response of the bed (“ecosystem engineers”) through the secretion of naturally
adhesive organic material (EPS: extracellular polymeric substances). Interactions between
main biofilm consortia microalgae, cyanobacteria and bacteria in terms of their individual
contribution to the EPS pool and their relative functional contribution to substratum
stabilisation were investigated.
The overall stabilisation potential of the various assemblages was impressive, as compared
to controls. The substratum stabilisation by estuarine microbial assemblages was due to the
secreted EPS matrix, and both EPS quality (carbohydrates and proteins) and quantity
(concentration) were important in determining stabilisation. Stabilisation was significantly
higher for the bacterial assemblages than for axenic microalgal assemblages. The peak of
engineering effect was significantly greater in the mixed assemblage as compared to the
bacterial and axenic diatom culture. This work confirmed the important role of
heterotrophic bacteria in “biostabilisation” and highlighted the interactions between
autotrophic and heterotrophic biofilm components of the consortia.
An additional approach, to investigate the impact of toxins on biostabilisation capacity of
aquatic organism was performed on cultured bacterial and natural freshwater biofilm.The
data suggest a different mode of triclosan (TCS) action ranging from suppressing
metabolisms to bactericidal effects depending on the TCS concentration. The inhibitory
effect of triclosanon bacterial and freshwater biofilms was confirmed.
This information contributes to the conceptual understanding of the microbial sediment
engineering that represents an important ecosystem function and service in aquatic
|Publisher: ||University of St Andrews|
|Appears in Collections:||Biology Theses|
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