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SRIJAN AGGARWAL
Bacterial Biofilms- A
Public Health Nuisance?
Assistant Professor
Civil & Environmental Engineering
University of Alaska Fairbanks
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WHAT IS A BIOFILM?
A community of micro-organisms attached to a solid surface and encapsulated within self-produced slime.
Source: CDC Public Health Image Library
S. aureus biofilm on the
surface of a medical
catheter that was removed
from a patient
(electron micrograph
magnified 2363×)
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WHAT IS A BIOFILM ?
cells
Extracellular polymeric substances
(EPS)
Photo credit: Centre for Biofilm Engineering, Montana State University
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WIDE RANGING BIOFILM IMPACTS
http://carroll1.cc.edu/~jclausz/microbiology/wst.htmlPhoto credit: Centre for Biofilm Engineering, Montana State University
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Photo credit: Centre for Biofilm Engineering, Montana State University
BIOFILMS IN THE HUMAN BODY
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Pathogen
growth
in biofilm
and protozoa Biofilm detachmentDISINFECTION
Sediment
resuspension
Particle
depositionSUBSTRATE
LEACHING
Water
Quality
Microbiome
Microbiome
Water
Quality
Water Quality
Infrastructure
Infrastructure Integrity
Water Quality
Biofilms In Drinking Water Distribution Systems
National Science Foundation. 2018-23. CAREER: Fundamental
Investigation of Biofilm Mechanical Properties in Drinking Water
Distribution Systems. Aggarwal (PI). $507,986.
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Why Biofilm Mechanical Properties ?
Motivation: Biofilm Control
Biofilm Control
Remove detrimental biofilms. e.g., Biofilms
in CF patients
Promote/Stabilize beneficial biofilms. e.g., Trickling filter
Biofilm detachment characteristics
Biofilm mechanical properties
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Biofilm Growth Reactors
Inflow
media
Peristaltic
pump
Waste
Media
Rotating
disk
reactor
CDC Biofilm
Reactor
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Aggarwal & Hozalski 2012,
Aggarwal & Hozalski 2010
Aggarwal et al. 2010, 2015
Microscope
objective lens
Microscope
stage
Motorized
micro-manipulator
Biofilm
coupon Micro-cantilever
20 mm scaleSee the movie
Cohesive/Adhesive Strength of
Biofilms
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Biofilm Mechanical Strength
Testing
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Mean Biofilm
strength
Applied
Stress (τ)
Factor of
Safety
24,821 0.071 348,746
8,078 0.183 44,207
10-2
10-1
100
101
102
103
104
105
P. aeruginosa S. epidermidis
Co
hesiv
e s
tren
gth
(P
a)
Biofilm Strength
Applied Stress
Are biofilms
overdesigned ?
Why is it difficult to remove
biofilms ?
(Aggarwal et al. 2015
Microbiology insights 8, MBI-S31444)
Strength in Pascals (N/m2)
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Paradigm shift:
Focus on the EPS matrix
• Need to weaken the biofilm EPS matrix
• Instead of bacteria, focus on the EPS matrix
• Investigate EPS weakening agents termed as
‘detachment-promoting agents’ (DPAs)
• e.g. Dispersin B, Tannins, D-amino acids, urea, enzymes
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Flow Cell Studies
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Funding Sources
• National Science Foundation (NSF)
• U.S. Environmental Protection Agency (EPA)
• Alaska NSF EPSCoR
• University of Alaska BLaST Program
• Upcoming: NSF CAREER Award (2018-23)
14
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QUESTIONS?