Assessment of Changes in Biodiversity when a Community of Ultramicrobacteria Isolated from Groundwater Is Stimulated to Form a Biofilm |
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Authors: | Ross N Villemur R Marcandella E Deschênes L |
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Institution: | (1) National Water Research Institute, Environment Canada, L7R 4A6 Burlington, Ontario, Canada;(2) Microbiologie et Biotechnologie, INRS-Institut Armand-Frappier, H7V IB7 Laval, Quebec, Canada;(3) NSERC Industrial Chair in Site Remediation and Management, Department of Chemical Engineering, école Polytechnique de Montréal, Station Centre-Ville, P.O. Box 6079, H3C 3A7 Montreal, Quebec, Canada |
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Abstract: | The stimulation of groundwater bacteria to form biofilms, for the remediation of polluted aquifers, is subjected to environmental
regulations that included measurement of effects on microbial biodiversity. Groundwater microorganisms contain a proportion
of unidentified and uncharacterized ultramicrobacteria (UMB) that might play a major role in the bioclogging of geological
materials. This study aimed to assess the changes in genetic and metabolic biodiversity when a community of UMB, isolated
from groundwater, is stimulated to form biofilms on a ceramic surface. UMB were stimulated with aerobic conditions and injection
of molasses, in reactors reproducing groundwater composition and temperature. Concentration of planktonic viable UMB, secretion
of extracellular polymeric substances (EPS), and biofilm thickness were monitored. The assessment of changes in biodiversity
was achieved by comparing the initial UMB community to the biofilm community, using the single strand conformational polymorphism
(SSCP) method, the cloning and sequencing of 16S rRNA gene (16S rDNA) sequences, and the Biolog microplate system. The hypothesis
stating that indigenous UMB would play a significant role of in the biofilm development was corroborated. Within 13 days of
stimulation, the UMB produced 700 mg L−1 of planktonic EPS and formed a biofilm up to a thickness of 1100 μm. This stimulation led to a decrease in genetic diversity
and an increase in metabolic diversity. The decrease in genetic diversity was shown by a reduced number of single strand DNA
fragments in the SSCP profiles. As such, 16S rDNA sequences from the biofilm revealed the predominance of four bacterial groups:
Zoogloea, Bacillus/Paenibacillus, Enterobacteriaceae, and Pseudomonads. A significant increase in metabolic diversity was shown by a highest substrate richness
profile and a lower substrate evenness profile of the biofilm bacterial population (p=0.0 and p=0.09, respectively). This higher metabolic diversity might be a consequence of the stimulation that seemed to favor the growth
of bacteria having a high nutritional versatility. Stimulation of UMB, isolated from groundwater, was effective to form a
biofilm having a high metabolic biodiversity. This combination of molecular-based and metabolic-based methods expanded the
insight into monitoring the changes in bacterial biodiversity. |
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