Assessment of the factors contributing to the variations in microcystins biodegradability of the biofilms on a practical biological treatment facility

Presence or Absence of mlr Genes and Nutrient Concentrations Co-Determine the Microcystin Biodegradation Efficiency of a Natural Bacterial Community

“…The equal degradation of both MC-LR and MC-RR by our isolated strains in the presence of variable C and N concentrations (Figures S1–S3) indicates that both mlr and alternative non- mlr pathways do not appear to exhibit preference among MC variants, which is consistent with other studies where no differences were found either in reservoir water samples [53] or in mineral salts medium [50]. Therefore, regardless of common shifts in the relative abundance of MC variants along the bloom episode, MC degraders from the bacterial community will face these changes with similar efficiency, as they do not show any preference for one type over the other.…”

“…Similar results were observed by Zhu et al (2014) [49], who found that seasonal variations of extracellular MCs in water were related to variations in MCs-degrading bacterial abundance based on mlr A gene analysis. Our results, together with other studies, suggest that these mlr A + bacteria make an important contribution to the biodegradation of MCs in water [49,50]. However, the real contribution of the total biodegradation of MCs in nature can only be understood by considering the whole MCs-degrading bacterial community which, according to our results, goes beyond the analysis of the mlr A gene.…”

“…However, the real contribution of the total biodegradation of MCs in nature can only be understood by considering the whole MCs-degrading bacterial community which, according to our results, goes beyond the analysis of the mlr A gene. Therefore, although correlations between mlr A gene copy number and MC-LR biodegradation rate identified by Li et al (2015) [50] exhibited a similar changing trend, the low correlation ( R 2 = 0.54) actually indicates that biodegradation rate of MCs is only partially explained by mlr A-possessing MCs-degrading bacteria. This is consistent with the relatively higher abundance of mlr A − over mlr A + MCs-degrading bacteria found in our study and in Mou et al (2013) [24], which supports our observation that the MCs-degrading bacterial population that lacks mlr genes may be an important contribution to the MCs biodegradation process in nature.…”

The Effect of Organic Carbon Addition on the Community Structure and Kinetics of Microcystin-Degrading Bacterial Consortia

“…However, the toxin removal efficiency and extent of this lag phase can vary significantly with bacterial composition, nutrient concentration, and other environmental parameters that are associated with the source water. Efforts to evolve biofiltration from a passive process into a more standardized, controlled, and perhaps "engineered", biological treatment process for targeted removal of pollutants will require a better understanding of the physiology and genetics of MC-degrading bacteria [12][13][14][18][19][20].Significant efforts have been made to isolate and characterize the specific MC-degrading bacterial populations during algal bloom events in the source water and sediments, and from full scale biological treatment units in drinking water treatment facilities [7][8][9]17,[21][22][23][24]. However, these studies have not fully explored how these isolates function in mixed bacterial communities, nor the influences of mutualistic or antagonistic interactions on biodegradation kinetics.…”

“…Significant efforts have been made to isolate and characterize the specific MC-degrading bacterial populations during algal bloom events in the source water and sediments, and from full scale biological treatment units in drinking water treatment facilities [7][8][9]17,[21][22][23][24]. However, these studies have not fully explored how these isolates function in mixed bacterial communities, nor the influences of mutualistic or antagonistic interactions on biodegradation kinetics.…”