Bacterial Adhesion and Surface Modification for Micropatterning Bacteria

1
Bacterial Adhesion and Surface Modification for
Micropatterning Bacteria
Nathaniel D. Kopp - The Pennsylvania State
University
Department of Chemical Engineering - Advisor Dr.
Darrell Velegol
Background
Results
Why Study Bacterial Adhesion and
Biofilms? Bacterial adhesion and biofilms have
been increasingly studied due to their importance
in numerous applications. For instance, biofilms
contribute to biofouling as bacterial communities
form on surfaces such as ship hulls, pipes, and
prosthetic devices which decreases efficiency and
promotes corrosion and infection. In addition,
bacteria have also proven useful in
bioremediation as they are able to remove toxins
from soils and other contaminated media.
Methods
Future Work
Adhesion Process
An elastomeric PDMS (polydimethylsiloxane) stamp
will be used to stamp PEI onto a glass coverslip
or create bare patches on a coverslip corralled
in PEG. The silane-terminated PEG (polyethylene
glycol) attaches to the glass resulting in a PEG
surface, which resists bacterial adhesion. The
bacteria will preferentially adhere to the
stamped PEI or bare regions which will be in
hexagonal arrays to ensure the separation
distance and rate of diffusion of biomolecules is
uniform between all adhered bacteria. These
arrays will vary in the number of bacteria and
the spacing between cells. As the number of
bacteria in the array is altered, the force
required to detach the adhered bacteria may
change if biofilm formation is a cell density
dependent factor.
Results
Example of template to micropattern bacteria onto
coverslips for adhesion force measurements
Purpose
Study bacterial adhesion on modified surfaces of
polyethylenimine (PEI), poly-D-lysine (PDL), and
polyethylene glycol (PEG). Determine adhesion
force controls for randomly adhered bacteria for
use in future patterned bacteria
experiments.
Conclusions
From this study it has been shown that B. cepacia
G4 exhibits a relationship between the fraction
of cells detached on a coverslip when a flow is
applied in the flow chamber and the adhesion
time. As the adhesion increases, the fraction
detached decreases which indicate a maturation of
the biofilm which boosts adhesion. In addition,
this same strain also displays a relationship
between the concentration of positively charged
PEI and PDL and the fraction of cells detached.
As the concentrations of the PEI and PDL
increase, the fraction of cells that detach
decreases. Interestingly, with the two strains
of Pseudomonas, it was observed that both adhered
beyond the ability of the flow chamber set-up to
remove. Also, the non-sticky mutant of B.
cepacia, ENV 435, did not attach to the surfaces
as expected. On the other hand, all three
strains adhered to the bare coverslip which
contradicts the prediction of like negatively
charged objects repelling. Overall, the controls
and procedures for future experiments with
adhesion, biofilms, and quorum sensing were
nearly finalized.
Acknowledgements 1 Dr. Darrell Velegol
Advisor 2 Mary Parent - Grad Student 3Chemical
Engineering Bio-Endowment/REU Program