Ecophysiology of Defluviicoccus‐related tetrad‐forming organisms in an anaerobic–aerobic activated sludge process

Abstract

A group of uncultured tetrad-forming organisms (TFOs) was enriched in an acetate-fed anaerobic-aerobic sequencing membrane bioreactor showing deteriorated enhanced biological phosphorus removal capacity. Based on 16S rRNA gene clone library and fluorescence in situ hybridization (FISH) analyses, these TFOs were identified as novel members of the Defluviicoccus cluster in the Alphaproteobacteria, accounting for 90 +/- 5% of the EUBmix FISH-detectable bacterial cell area in the reactor biomass. Microautoradiography in combination with FISH and polyhydroxyalkanoate (PHA) staining revealed that these Defluviicoccus-related TFOs could take up and transform acetate, lactate, propionate and pyruvate, but not aspartic acid and glucose, into PHA under anaerobic conditions. In contrast, under continuous anaerobic-aerobic cultivation, Defluviicoccus vanus, the only cultured strain from the cluster, was able to take up glucose with concurrent glycogen consumption and PHA production under anaerobic conditions. Under subsequent aerobic conditions, the accumulated PHA was utilized and the biomass glycogen levels were restored. These findings not only re-confirmed these Defluviicoccus-related TFOs as glycogen-accumulating organisms, but also revealed unexpected levels of physiological, phylogenetic and morphological diversity among members of the Defluviicoccus cluster.

‘Candidatus Competibacter’-lineage genomes retrieved from metagenomes reveal functional metabolic diversity

“…This analysis revealed that essentially all the observed Competibacteraceae cells assimilated glucose under both aerobic and anaerobic conditions (Supplementary Figure S3), thus supporting the ability for glucose assimilation and fermentation that is suggested by annotation of the C. denitrificans genome. The ability to ferment glucose and store PHA is shared with the Tetrasphaera japonica PAO and the Defluviicoccus vanus GAO (Wong and Liu, 2007). Interestingly, anaerobic energy demand for C. denitrificans may be supplemented by the excretion of lactate, produced from glycogen fermentation, in symport with a cation contributing to a PMF (Konings et al, 1984).…”

The microbiology of phosphorus removal in activated sludge processes-the current state of play

“…This is due in part to difficulties in acquiring their 16S rRNA sequence information in clone libraries generated from EBPR communities even where they are abundant (Meyer et al, 2006). Success has been achieved with prior enrichment (Wong et al, 2004;Meyer et al, 2006;Wong and Liu, 2007;McIlroy et al, submitted). Wong et al (2004) first proposed that putative alphaproteobacterial GAO may be related to Defluviicoccus vanus from clone sequences in a library constructed with alpha-proteobacterial targeted PCR primers.…”

“…The probes Meyer et al (2006) published (DEF988 and DEF1020) were also designed so that together they targeted the whole cluster. A third Defluviicoccus 'cluster' (Wong and Liu, 2007) is based on a single 16S rRNA sequence only from a non-EBPR system but no FISH probes are available to detect it. Additional sequence data increasing the diversity among members of both clusters I and II have been reported (Wong and Liu, 2007), but the FISH probe designed to cover these for cluster II members (TFO_DF629) does not appear to work (Wong and Liu, 2007;McIlroy et al, submitted).…”

“…A third Defluviicoccus 'cluster' (Wong and Liu, 2007) is based on a single 16S rRNA sequence only from a non-EBPR system but no FISH probes are available to detect it. Additional sequence data increasing the diversity among members of both clusters I and II have been reported (Wong and Liu, 2007), but the FISH probe designed to cover these for cluster II members (TFO_DF629) does not appear to work (Wong and Liu, 2007;McIlroy et al, submitted). Furthermore, insufficient sequence data were obtained to determine whether the probes already available for the cluster II members (Meyer et al, 2006), covered these additional sequences.…”

“…In the absence of being able to identify glycogen accumulating cells directly by staining (Serafim et al, 2002), recognising the GAO in EBPR communities has been based on applying a range of molecular methods to identify the dominating populations (often as tetrad forming organisms or TFO) in systems with low EBPR capacity. Whether these possess the GAO phenotype can be determined by fluorescence in situ hybridization/microautoradiography (FISH/MAR) (Kong et al, 2006;Ahn et al, 2007;Wong and Liu, 2007).…”