Identity, abundance and ecophysiology of filamentous Chloroflexi species present in activated sludge treatment plants

Abstract

Filamentous Chloroflexi species are often present in activated sludge wastewater treatment plants in relatively low numbers, although bulking incidences caused by Chloroflexi filaments have been observed. A new species-specific gene probe for FISH was designed and using phylum-, subdivision-, morphotype 1851- and species-specific gene probes, the abundance of Chloroflexi filaments were monitored in samples from 126 industrial wastewater treatment plants from five European countries. Chloroflexi filaments were present in 50% of the samples, although in low quantities. In most treatment plants the filaments could only be identified with phylum or subdivision probes, indicating the presence of great undescribed biodiversity. The ecophysiology of various Chloroflexi filaments was investigated by a suite of in situ methods. The experiments revealed that Chloroflexi constituted a specialized group of filamentous bacteria only active under aerobic conditions consuming primarily carbohydrates. Many exo-enzymes were excreted, e.g. chitinase, glucuronidase and galactosidase, suggesting growth on complex polysaccharides. The surface of Chloroflexi filaments appeared to be hydrophilic compared to other filaments present. These results are generally supported by physiological studies of two new isolates. Based on the results obtained in this study, the potential role of filamentous Chloroflexi species in activated sludge is discussed.

Amyloid-Like Adhesins Produced by Floc-Forming and Filamentous Bacteria in Activated Sludge

“…The higher fraction of amyloid adhesins in treatment plants with biological phosphorus removal than in plants with only N removal seemed primarily to be associated with a relatively larger fraction of amyloid-producing filamentous bacteria. In many plants of this type, filaments belonging to Chloroflexi and Aquaspirillum are very common (4,30,63). Microcolonies and non-cellbound amyloids were also present in flocs from all plants, but were, as detected by antibodies, not as abundant.…”

“…These filamentous bacteria were often observed to have dead cells in the middle of the filament; but the sheath material kept the filament intact, and it was still antibody positive in these segments, confirming its relatively high mechanical and/or biological stability. They may thus be very important backbones in the floc and are also the most common filamentous bacteria in many Nand P-removing treatment plants (30). Interestingly, these two particular groups are also frequently observed with attached growth of other bacteria.…”

“…Further details about growth conditions and medium description of the cultures are available from the DSMZ and ATCC. Paraformaldehyde-fixed samples of Chloroflexi morphotype 1851 strain EU25 (30) and M. perideroedes strain Gr1 (62) were used to support staining/labeling results from activated sludge samples.…”

Genomic and in situ investigations of the novel uncultured Chloroflexi associated with 0092 morphotype filamentous bulking in activated sludge

“…Members of the Chloroflexi in activated sludge have been suggested to have an important role in the hydrolysis of complex carbohydrates, a suggestion reinforced by the in situ detection of extracellular surface-associated catalytic enzymes for some species (Kragelund et al, 2007). Annotation of the Cfx-K genome revealed putatively secreted enzymes (based on the detection of a signal peptide sequence (Bendtsen et al, 2004), including an alpha-galactosidase (CFX0092_a0397) and several glycoside hydrolase, esterase and protease family proteins.…”

“…Neither polyphosphate nor lipid storage has been detected in B45 by standard in situ histochemical staining methods (Speirs et al, 2009). Phylum-level in situ investigations of the Chloroflexi in activated sludge biomass suggest they have a role in degradation of complex polymers and display a preference for sugar utilization (Kragelund et al, 2007(Kragelund et al, , 2011. Whether this holds true for B45 phylotype members remains to be determined.…”