Reviewing the Role of EPS Layers in Sustaining Pests and Reducing Sanitation Efficacy
Abstract
Biofilms represent a pervasive challenge in wastewater treatment, food production, and
agricultural environments. These structured microbial communities form on wetted surfaces,
creating a hydrophobic extracellular matrix that retains moisture, protects embedded
microorganisms, and resists oxidizing biocides. This environment also provides a breeding
substrate for pests such as filter flies (Psychodidae), leading to recurring infestations and
increased sanitation costs.
This review synthesizes current literature on the formation, composition, and functional
impacts of biofilms, with an emphasis on their role as pest harborage. The analysis highlights
the limitations of existing sanitation practices—including chlorine dosing, fogging, and
mechanical removal—and calls for the integration of biofilm-targeted interventions into
standard pest management protocols.
1. Introduction
Biofilms are surface-associated microbial communities embedded within a self-produced
matrix of extracellular polymeric substances (EPS). These matrices are composed primarily of
polysaccharides, proteins, and extracellular DNA, forming a hydrated, gel-like barrier that
protects microbial residents from environmental stressors and chemical agents.
In engineered systems such as wastewater treatment plants, biofilm development is nearly
inevitable on any wetted surface. While biofilms play a role in certain treatment processes,
their uncontrolled growth can reduce hydraulic efficiency, create localized anaerobic zones,
and harbor nuisance organisms including insect larvae. This review aims to consolidate
current understanding of biofilm biology with respect to its role in sustaining pest populations
and impeding sanitation efficacy.2. Biofilm Formation and Composition
Biofilm formation is a multistage process involving initial attachment, irreversible adhesion,
maturation, and eventual dispersion of microbial cells. The extracellular polymeric substance
(EPS) matrix is a heterogeneous mixture of polysaccharides, proteins, lipids, and extracellular
DNA, which together form a hydrated, gel-like scaffold. This matrix provides mechanical
stability, creates a hydrophobic barrier to cleaning agents, and traps nutrients, allowing
microbial persistence.
Once mature, biofilms display high cell density and metabolic diversity, including aerobic and
anaerobic organisms coexisting within the same matrix. This structural and functional
heterogeneity makes biofilms difficult to eradicate and explains their role as a chronic source
of contamination in industrial and agricultural environments.
3. Biofilms as Pest Harborage
Biofilms create a microenvironment favorable for invertebrate colonization, particularly for
species whose life cycles depend on persistent moisture and nutrient availability. Filter flies
(Psychodidae) are strongly associated with biofilm-rich environments in wastewater treatment
plants and drains.
The EPS matrix retains water and nutrients, providing a food source and protection for
developing larvae. Biofilms act as a physical and chemical barrier, shielding larvae from
biocides and allowing fly populations to persist despite surface sanitation programs. Adult flies
emerging from these habitats can transport pathogens mechanically, posing public health and
food safety concerns.4. Impact on Sanitation and Control Measures
Biofilm presence significantly reduces the effectiveness of conventional sanitation programs.
The EPS layer acts as a diffusion barrier, neutralizing chlorine and other oxidizers before they
can reach embedded microbes. This results in sublethal exposures, potential microbial
adaptation, and increased chemical demand to maintain compliance.
Surface-applied insecticides and fogging treatments may temporarily suppress adult fly
populations but fail to eliminate biofilm-harbored larvae, leading to population rebounds. The
persistence of biofilm drives chronic maintenance burdens, including labor-intensive cleaning,
increased downtime, and customer complaints.
5. Current Methods and Limitations
Mechanical removal (scraping, flushing) provides immediate but short-lived results, as biofilm
rapidly recolonizes surfaces. Chemical oxidizers require high dosages to penetrate EPS,
increasing costs and potentially damaging equipment. Insecticide fogging leaves larval
habitats intact and requires frequent reapplication, raising the risk of resistance.
6. Need for Innovative Solutions
The literature highlights the need for biofilm-targeted interventions that penetrate EPS,
prevent rapid recolonization, enhance the activity of oxidizers, and provide residual protection.
Biosurfactant-based formulations are an emerging technology that show promise in
addressing these needs by combining biofilm displacement with extended surface action.
7. Conclusion
Biofilms are a persistent and costly challenge, providing harborage for pests and resisting
conventional sanitation. Breaking the biofilm barrier is critical to achieving sustainable pest
control, improving regulatory compliance, and reducing operational costs. Future research
should focus on integrated approaches that combine biofilm removal, residual surface
protection, and complementary chemical treatments.References
Banat, I. M., et al. (2014). Microbial biosurfactants production, applications and future
potential. Applied Microbiology and Biotechnology, 98, 381–394.
Donlan, R. M. (2002). Biofilms: Microbial Life on Surfaces. Emerging Infectious Diseases,
8(9), 881–890.
Flemming, H.-C., & Wingender, J. (2010). The biofilm matrix. Nature Reviews Microbiology, 8,
623–633.
Hall-Stoodley, L., Costerton, J. W., & Stoodley, P. (2004). Bacterial biofilms: from the natural
environment to infectious diseases. Nature Reviews Microbiology, 2, 95–108.
LeChevallier, M. W., Cawthon, C. D., & Lee, R. G. (1988). Factors promoting survival of
bacteria in chlorinated water supplies. Applied and Environmental Microbiology, 54(3),
649–654.
Lindquist, D. A., Geden, C. J., & Hogsette, J. A. (2018). Biology and control of filter flies in
wastewater systems. Journal of Vector Ecology, 43(2), 167–176.
Stewart, P. S. (2003). Diffusion in biofilms. Journal of Bacteriology, 185(5), 1485–1491.