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Chapter 1
ecosystem with the use of microscopy, it was deduced that 99.9% of the
bacteria assessed grew in a biofilm on a range of surfaces [69].
The formation and structure of a biofilm is influenced by numerous
variables including species [70], surface [71], nutrients available [32, 72]
and other environmental conditions [73]. The biofilm development process
is initiated with single cells attaching to a surface or to each other, this is
then followed by the formation of clustered cells or microcolonies [74].
Over time, the microcolonies are surrounded by a protective layer of
protein-rich substances referred to as extracellular polymeric substances
(EPS). As the biofilm grows the biofilm matrix develops water channels that
act as a support system to provide nutrients to the less exposed areas of
the biofilm and act as a route for waste disposal [74].
Previous research has suggested that almost all bacteria can form a biofilm
and that once the transition from planktonic cells to their biofilm state is
initiated, this becomes the optimum form for the bacterial cells existence
[75]. It is also reported that single-species bacteria can be heterogeneous
in their nature, with each group of cells undertaking a different role in the
biofilm development depending on environmental cues such as availability
of oxygen. The cells of a single species within a bacterial culture may
display differences in metabolism, gene expression, morphology and
physiology allowing it to work well within its community, depending on it
spatial relationship in the biofilm matrix [76]. For example, a bacterial cell
embedded in the biofilm matrix may survive on less nutrients and lower
oxygen gradients by going into a dormant state [75].
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