Abstract:Increasing incidences of activated sludge foaming have been reported in the last decade in Danish plants treating both municipal and industrial wastewaters. In most cases, foaming is caused by the presence of Actinobacteria; branched mycolic acid-containing filaments (the Mycolata) and the unbranched Candidatus'Microthix parvicella'. Surveys from wastewater treatment plants revealed that the Mycolata were the dominant filamentous bacteria in the foam. Gordonia amarae-like organisms and those with the morpholog… Show more
“…Although these notorious and always filamentous BFB, if present outside the bioflocs, can cause settling (bulking) and foaming problems and deteriorate effluent quality, it is believed that BFBrelated filaments are usually presented in 'well-behaved' activated sludge and have versatile roles (for example, bioflocs formation; Kragelund et al, 2007; lipids or oleic acid degradation, Nielsen et al, 2010) other than being detrimental. Moreover, the protein hydrolyzers Saprospiraceae (phylum Bacteroidetes) were highly diverse (40 OTUs, Figure 2d) and abundant (5.0%, Figure 2e) in activated sludge.…”
Section: Environmental Influences On Bacterial Diversity and Abundancementioning
Understanding environmental and biological influences on the dynamics of microbial communities has received great attention in microbial ecology. Here, utilizing large time-series 16S rRNA gene data, we show that in activated sludge of an environmentally important municipal wastewater treatment plant, 5-year temporal dynamics of bacterial community shows no significant seasonal succession, but is consistent with deterministic assemblage by taxonomic relatedness. Biological interactions are dominant drivers in determining the bacterial community assembly, whereas environmental conditions (mainly sludge retention time and inorganic nitrogen) partially explain phylogenetic and quantitative variances and indirectly influence bacterial assembly. We demonstrate a correlation-based statistical method to integrate bacterial association networks with their taxonomic affiliations to predict community-wide co-occurrence and co-exclusion patterns. The results show that although taxonomically closely related bacteria tend to positively co-occur (for example, out of a cooperative relationship), negative co-excluding correlations are deterministically observed between taxonomically less related species, probably implicating roles of competition in determining bacterial assembly. Overall, disclosures of the positive and negative species-species relations will improve our understanding of ecological niches occupied by unknown species and help to predict their biological functions in ecosystems.
“…Although these notorious and always filamentous BFB, if present outside the bioflocs, can cause settling (bulking) and foaming problems and deteriorate effluent quality, it is believed that BFBrelated filaments are usually presented in 'well-behaved' activated sludge and have versatile roles (for example, bioflocs formation; Kragelund et al, 2007; lipids or oleic acid degradation, Nielsen et al, 2010) other than being detrimental. Moreover, the protein hydrolyzers Saprospiraceae (phylum Bacteroidetes) were highly diverse (40 OTUs, Figure 2d) and abundant (5.0%, Figure 2e) in activated sludge.…”
Section: Environmental Influences On Bacterial Diversity and Abundancementioning
Understanding environmental and biological influences on the dynamics of microbial communities has received great attention in microbial ecology. Here, utilizing large time-series 16S rRNA gene data, we show that in activated sludge of an environmentally important municipal wastewater treatment plant, 5-year temporal dynamics of bacterial community shows no significant seasonal succession, but is consistent with deterministic assemblage by taxonomic relatedness. Biological interactions are dominant drivers in determining the bacterial community assembly, whereas environmental conditions (mainly sludge retention time and inorganic nitrogen) partially explain phylogenetic and quantitative variances and indirectly influence bacterial assembly. We demonstrate a correlation-based statistical method to integrate bacterial association networks with their taxonomic affiliations to predict community-wide co-occurrence and co-exclusion patterns. The results show that although taxonomically closely related bacteria tend to positively co-occur (for example, out of a cooperative relationship), negative co-excluding correlations are deterministically observed between taxonomically less related species, probably implicating roles of competition in determining bacterial assembly. Overall, disclosures of the positive and negative species-species relations will improve our understanding of ecological niches occupied by unknown species and help to predict their biological functions in ecosystems.
“…This foam causes acute operational problems and may also pose environmental and health hazards (13,43,44). The foam is stabilized by highly abundant hydrophobic bacteria, including the mycolic acid-containing Actinobacteria, the mycolata (13,23,41). Many control measures have been described to eliminate these foams, but none are successful in all cases, which probably reflects the poor understanding of foam microbial ecology (13).…”
Activated sludge plants suffer frequently from the operational problem of stable foam formation on aerobic reactor surfaces, which can be difficult to prevent. Many foams are stabilized by mycolic acid-containing Actinobacteria, the mycolata. The in situ biocontrol of foaming using phages is an attractive strategy. We describe two polyvalent phages, GTE5 and GRU1, targeting Gordonia terrae and Gordonia rubrupertincta, respectively, isolated from activated sludge. Phage GRU1 also propagates on Nocardia nova. Both phages belong to the family Siphoviridae and have similar-size icosahedral heads that encapsulate doublestranded DNA genomes (ϳ65 kb). Their genome sequences are similar to each other but markedly different from those of other sequenced phages. Both are arranged in a modular fashion. These phages can reduce or eliminate foam formation by their host cells under laboratory conditions.
“…Its cause is the overproliferation of hydrophobic bacterial populations, among which are the mycolic acid-producing Actinobacteria, the mycolata (3,5,11,18,19). This group includes the genera Corynebacterium, Dietzia, Gordonia, Skermania, Mycobacterium, Nocardia, Rhodococcus, and Tsukamurella (5).…”
Most activated sludge treatment plants suffer from the presence of foams on the surfaces of their aeration reactors. These are often stabilized by hydrophobic mycolic acid-synthesizing actinobacterial species. A polyvalent Siphoviridae phage, GTE7, which lysed several Gordonia and Nocardia species, is described here. Its genome has a modular structure similar to that described for Rhodococcus phage ReqiDocB7. In laboratoryscale experiments, we showed that GTE7 prevents stabilization of foams by these Gordonia and Nocardia species.
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