Ecophysiology of mycolic acid-containing Actinobacteria (Mycolata) in activated sludge foams

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 morphology of Skermania piniformis were frequently observed, and they often coexisted. Their identity was confirmed by FISH, using a new permeabilization procedure. It was not possible to identify all abundant Mycolata using existing FISH probes, which suggests the presence of currently undetectable and potentially undescribed populations. Furthermore, some Mycolata failed to give any FISH signal, although substrate uptake experiments with microautoradiography revealed that they were physiologically active. Ecophysiological studies were performed on the Mycolata identified by their morphology or FISH in both foams and mixed liquors. Large differences were seen among the Mycolata in levels of substrate assimilation and substrate uptake abilities in the presence of different electron acceptors. These differences were ascribed mainly to the presence of currently undescribed Mycolata species and/or differences in foam age.

Bacterial assembly and temporal dynamics in activated sludge of a full-scale municipal wastewater treatment plant

“…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.…”

Genome Sequences and Characterization of the Related Gordonia Phages GTE5 and GRU1 and Their Use as Potential Biocontrol Agents

“…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).…”

Prevention of Gordonia and Nocardia Stabilized Foam Formation by Using Bacteriophage GTE7

“…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).…”