Abstract
Sialic acids in the structural matrix of biofilms developing in engineered water systems constitute a potential target in the battle against biofouling. This report focuses specifically on the presence of sialic acids as part of the extracellular polymeric substances (EPS) of biofilms forming in cooling towers and the potential effect of nutrient starvation on sialic acid presence and abundance. Two cooling water compositions were compared in parallel pilot-scale cooling towers, one poor in nutrients and one enriched in nutrients. Fresh deposits from the two cooling towers were collected after a five-week operation period. EPS extractions and analyses by Fourier transform infrared spectroscopy (FTIR) and high-resolution mass spectrometry (MS), along with 16S rRNA gene amplicon sequencing were performed. The results of MS analyses showed the presence of pseudaminic/legionaminic acids (Pse/Leg) and 2-keto-3-deoxy-d-glycero-d-galacto-nononic acid (KDN) in both biofilm EPS samples. FTIR measurements showed the characteristic vibration of sialic acid-like compounds ν(C=O)OH in the nutrient poor sample exclusively. Our findings, combined with other recent studies, suggest that bacterial sialic acids are common compounds in environmental biofilms. Additionally, the conservation of sialic acid production pathways under nutrient starvation highlights their importance as constituents of the EPS. Further in-depth studies are necessary to understand the role of sialic acids in the structural cohesion and protection of environmental biofilm layer.
Highlights
Biofilm formation is highly detrimental to the daily operation and lifetime of engineered water processes, such as heat exchangers and membrane filtration systems
The objectives are to (i) evaluate the presence of sialic acids in extracellular polymeric substances (EPS) of environmental biofilms and estimate the potential for sialic acid production by the biofilm bacterial communities, (ii) investigate the impact of nutrient poor condition on the presence and abundance of sialic acids, and (iii) explore the implications of the findings related to engineered water processes prone to biofouling
Biofilms were developed under the following conditions: (i) poor in nutrients, i.e., Seawater reverse osmosis (SWRO) permeate without additional nutrients as feed water, and (ii) enriched in nutrients, i.e., SWRO permeate with addition of 0.5:0.1:0.05 (C:N:P) mg/L and trace metals as feed water
Summary
Biofilm formation is highly detrimental to the daily operation and lifetime of engineered water processes, such as heat exchangers and membrane filtration systems. A newly established mass spectrometric approach by Kleikamp et al [6] revealed their wide-spread occurrence in non-pathogenic species These recent discoveries raise interesting questions regarding the occurrence of sialic acids in the biofouling layer of engineered water systems. The objectives are to (i) evaluate the presence of sialic acids in EPS of environmental biofilms and estimate the potential for sialic acid production by the biofilm bacterial communities, (ii) investigate the impact of nutrient poor condition on the presence and abundance of sialic acids, and (iii) explore the implications of the findings related to engineered water processes prone to biofouling
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