The in situ physiology of Skermania piniformis in foams in Australian activated sludge plants

Abstract

The in situ physiology of the filamentous bacterium Skermania piniformis frequently seen in activated sludge foams in Australia was investigated. An oligonucleotide probe, Spin1449, targeting the 16S rRNA of S. piniformis was designed for its identification by fluorescence in situ hybridization (FISH), validated with pure cultures and applied successfully to foam samples from two geographically distant Australian plants. While filaments of this bacterium appeared to be comparatively hydrophobic, the organism had no clear preference for hydrophobic or hydrophilic substrates. In both foams examined using microautoradiography (MAR), filaments selectively took up substrates under aerobic and anoxic (NO(3) (-)) but not anaerobic or anoxic (NO(2) (-)) conditions. Skermania piniformis assimilated oleic acid, palmitic acid, glycerol and glycine. Ectoenzyme activities detected suggest that S. piniformis has an ability to assimilate a greater range of substrates than might be concluded from the MAR data obtained here. Based on the substrate uptake data presented here, an anaerobic selector may work for controlling S. piniformis in activated sludge systems.

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

“…Increasing the hybridization stringency conditions did not overcome this problem (results not shown). This differs from earlier observations by Eales et al (2006), and again could indicate the presence of populations whose 16S rRNA gene sequences are not yet available and hence cannot be used for probe design and validation. Application of the broad Mycolata probe (Myc657) revealed the presence of nonfilamentous Mycolata appearing as cocci or rods present inside flocs as well as small filaments with sparse branching.…”

“…Further information on probe sequences and the hybridization conditions required is available from probeBase (http://www.microbial-ecology.net/probebase). Those for Spin1449 are given by Eales et al (2006).…”

Ecophysiology of the Actinobacteria in activated sludge systems

“…Substrates like oleic acid which G. amarae grows on in pure culture are not always assimilated in situ Kragelund et al 2007b), and strong evidence for in situ substrate uptake with nitrate as electron acceptor questions whether G. amarae is obligately aerobic, as pure culture data suggest. Eales et al (2006) reported similar conflicting data for S. piniformis. Differences in substrate assimilation patterns were also apparent from studies carried out in samples from different plants with both FISH probed G. amarae and S. piniformis Kragelund et al 2007b).…”

“…For example, their ability to produce ectoenzymes, detected with enzyme linked fluorescence (ELF Ò ) assays Eales et al 2006) or substituted 4-bora-3a, 4a-diazas-indacene derivative (BODIPY) dye-labelled substrates ) provides information on whether populations may metabolize polymeric or low molecular weight substrates, and what their chemical nature might be. This approach is limited by the range of ELF substrates available commercially, but has been used in ecophysiological studies with foaming Mycolata (Kragelund et al 2007b;Eales et al 2006). The microbial adhesion to cells (MAC) assay can also be applied to these communities in conjunction with FISH to identify in situ which populations including the Mycolata possess high cell surface hydrophobicity , and whether this might change in response to varying plant operational conditions .…”

“…Studies have used FISH/MAR to elucidate the ecophysiology of G. amarae and S. piniformis in plants in Denmark, the Czech Republic and Australia Eales et al 2005Eales et al , 2006Kragelund et al 2007b), but nothing similar is known about the many other foaming Mycolata, including those for which FISH probes are not yet available. The data highlight the difficulties inherent in work of this kind.…”