Brugia Malayi - Clark Science Center - Smith College

Effects of Surface Chemistry on Biofilm Colonization
Minhee Kim, Jinglin Huang and Jing Zhang
The effect of surface chemistry on biofilm colonization has become a popular research subject in medical and environmental
fields, with a growing public concern on biofilm coating on medical devices and water pipelines. 1, 2 Our summer research
continued our previous study on the responses of Pseudomonas aeruginosa, a model organism in biofilm studies, to nanoscale surfaces
with different physical characters.
Two types of nanoscale surface topography, flat hydrophobic and flat hydrophilic, were constructed and coated by P.
aeruginosa, followed by a visual observation of biofilm growth under fluorescence microscope. The qualitative analysis on the
arabinose-induced fluorescence, emitted by the attached bacteria, suggested that layers of bacteria start to accumulate and
are discernible for measurement after six hours of incubation. Three ways to quantify the biofilm growth were performed to
distinguish bacteria’s response to two studied surface types. The first one is through TECAN Infinite M1000, a microplate reader
capable of detecting and quantifying the fluorescence intensity emitted from areas of interest. TECAN data collected from three
sets of experiments demonstrated a distinguishable difference between biofilm growth on flat hydrophobic and hydrophilic
surfaces after six hours of incubation. The three-dimensional modeling of the spatial distribution of bacteria on the surface was
enabled by Magellan, a software developed by TECAN Group. To prove the validity of results obtained through TECAN, the
second quantification means was proposed, through which microscopic images were sampled from areas of interest and analyzed
by an image-processing program named Image J. 4 Sonication was carried out as a third way to assess the growing performance of
P. aeruginosa. An ultrasound water bath 5 was applied to remove attached bacterial cells from the surfaces and after centrifugation,
cells were reintroduced in aliquots to growth media. Cell colonies were counted and the difference in colony-forming units
appeared indicated that more cells were detached from flat hydrophobic samples compared to flat hydrophilic ones after six hours
of incubation.
In continuation of our studies, the protocols developed from our summer research should be repeated for multiple times until
substantial amount of data are gathered to draw the conclusion. To investigate the effects of surface roughness, protocols should
be tested on rough hydrophobic and hydrophilic surfaces, in comparison to flat topography. (Supported by the Howard Hughes
Medical Institute)
Advisors: Kate Queeney and Rob Dorit
References:
1
Mack D, Rohde H, Harris LG, Davies AP, Horstkotte MA, Knobloch JK. (2006). Biofilm formation in medical device-related infection. International Journal of
Artificial Organs. 29 (4): 343-59.
2
Pavanello G, Faimali M, Pittore M, Mollica A, Mollica A, Mollica A. (2011). Exploiting a new electrochemical sensor for biofilm monitoring and water treatment
optimization. Water Research. 45 (4): 1651-1658. 3 The information of TECAN Group Ltd is available at www.tecan.com.
4
The information of Image J is available at http://rsbweb.nih.gov/ij/.
5
The information of Branson model 2510 sonicating water bath is available at http://www.emersonindustrial.com/en-US/branson/Products/precision-cleaning/
bench-top-cleaners/bransonics/Pages/default.aspx.
2012
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