View source for Polyphosphate-accumulating organisms

[[File:Cluster of PAOs.jpg|thumb|Cluster of PAOs]]

'''Polyphosphate-accumulating organisms''' (PAOs) are a group of [[microorganism]]s that, under certain conditions, facilitate the removal of large amounts of [[phosphorus]] from their environments. The most studied example of this phenomenon is in polyphosphate-accumulating bacteria (PAB) found in a type of wastewater processing known as [[enhanced biological phosphorus removal]] (EBPR), however phosphate hyperaccumulation has been found to occur in other conditions such as soil and marine environments, as well as in non-bacterial organisms such as fungi and algae.<ref name=":2">{{Cite journal |last1=Akbari |first1=Ali |last2=Wang |first2=ZiJian |last3=He |first3=Peisheng |last4=Wang |first4=Dongqi |last5=Lee |first5=Jangho |last6=Han |first6=Il |last7=Li |first7=Guangyu |last8=Gu |first8=April Z. |date=January 2021 |title=Unrevealed roles of polyphosphate-accumulating microorganisms |journal=Microbial Biotechnology |language=en |volume=14 |issue=1 |pages=82–87 |doi=10.1111/1751-7915.13730 |issn=1751-7915 |pmc=7888455 |pmid=33404187}}</ref> PAOs accomplish this removal of phosphate by accumulating it within their cells as [[polyphosphate]]. PAOs are by no means the only microbes that can accumulate phosphate within their cells and in fact, the production of polyphosphate is a widespread ability among microbes. However, PAOs have many characteristics that other organisms that accumulate polyphosphate do not have that make them amenable to use in [[wastewater treatment]]. Specifically, in the case of classical PAOs, is the ability to consume simple carbon compounds (energy source) without the presence of an external electron acceptor (such as nitrate or oxygen) by generating energy from internally stored polyphosphate and glycogen. Many bacteria cannot consume carbon without an energetically favorable electron acceptor and therefore PAOs gain a selective advantage within the mixed microbial community present in the activated sludge.<ref>{{Cite journal |last1=Oehmen |first1=Adrian |last2=Lemos |first2=Paulo C. |last3=Carvalho |first3=Gilda |last4=Yuan |first4=Zhiguo |last5=Keller |first5=Jürg |last6=Blackall |first6=Linda L. |last7=Reis |first7=Maria A. M. |date=2007-06-01 |title=Advances in enhanced biological phosphorus removal: From micro to macro scale |url=https://www.sciencedirect.com/science/article/pii/S0043135407001091 |journal=Water Research |volume=41 |issue=11 |pages=2271–2300 |doi=10.1016/j.watres.2007.02.030 |issn=0043-1354|url-access=subscription }}</ref> Therefore, wastewater treatment plants that operate for enhanced biological phosphorus removal have an anaerobic tank (where there is no nitrate or oxygen present as external electron acceptor) prior to the other tanks to give PAOs preferential access to the simple carbon compounds in the wastewater that is influent to the plant.

== Metabolisms ==

=== Classical (Canonical) PAO Metabolism ===
The classical or "canonical" behavior of PAOs is considered to be the release of phosphate (as [[orthophosphate]]) to the environment and transformation of intracellular polyphosphate reserves into [[polyhydroxyalkanoates]] (PHA) from [[volatile fatty acids]] (VFAs) and glycogen during anoxic conditions.<ref name=":0">{{Citation |last1=Akram |first1=Fatima |title=Chapter 8 - Role of polyphosphate accumulating organisms in enhanced biological phosphorous removal |date=2022-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780323918930000031 |work=Microbial Consortium and Biotransformation for Pollution Decontamination |pages=151–179 |editor-last=Dar |editor-first=Gowhar Hamid |access-date=2023-07-07 |series=Advances in Environmental Pollution Research |publisher=Elsevier |language=en |isbn=978-0-323-91893-0 |last2=Aqeel |first2=Amna |last3=Ahmed |first3=Zeeshan |last4=Zafar |first4=Javeria |last5=Haq |first5=Ikram ul |editor2-last=Bhat |editor2-first=Rouf Ahmad |editor3-last=Qadri |editor3-first=Humaira |editor4-last=Hakeem |editor4-first=Khalid Rehman}}</ref> This is followed by the consumption of the PHA/VFAs and uptake of environmental orthophosphate during oxic conditions to regenerate polyphosphate reserves within the cell.<ref name=":0" />

=== Non-Canonical (or "Fermentative) PAO Metabolism ===
Some PAOs have been found to have alternative methods to accumulating polyphosphate, particularly to do with not storing PHA or glycogen.<ref name=":12">{{Cite journal |last1=Singleton |first1=C. M. |last2=Petriglieri |first2=F. |last3=Wasmund |first3=K. |last4=Nierychlo |first4=M. |last5=Kondrotaite |first5=Z. |last6=Petersen |first6=J. F. |last7=Peces |first7=M. |last8=Dueholm |first8=M. S. |last9=Wagner |first9=M. |last10=Nielsen |first10=P. H. |date=June 2022 |title=The novel genus, 'Candidatus Phosphoribacter', previously identified as Tetrasphaera, is the dominant polyphosphate accumulating lineage in EBPR wastewater treatment plants worldwide |journal=The ISME Journal |volume=16 |issue=6 |pages=1605–1616 |doi=10.1038/s41396-022-01212-z |issn=1751-7370 |pmc=9123174 |pmid=35217776}}</ref><ref name=":23">{{Cite journal |last1=Nielsen |first1=Per Halkjær |last2=McIlroy |first2=Simon J. |last3=Albertsen |first3=Mads |last4=Nierychlo |first4=Marta |date=June 2019 |title=Re-evaluating the microbiology of the enhanced biological phosphorus removal process |journal=Current Opinion in Biotechnology |volume=57 |pages=111–118 |doi=10.1016/j.copbio.2019.03.008 |issn=1879-0429 |pmid=30959426|s2cid=104294644 |doi-access=free }}</ref> This is generally believed to be seen more often in extracellular environments high in organic compounds, thus containing fermentable substrates like amino acids and sugars.<ref>{{Cite journal |last1=Nguyen |first1=Hien Thi Thu |last2=Kristiansen |first2=Rikke |last3=Vestergaard |first3=Mette |last4=Wimmer |first4=Reinhard |last5=Nielsen |first5=Per Halkjær |date=2015-07-15 |title=Intracellular Accumulation of Glycine in Polyphosphate-Accumulating Organisms in Activated Sludge, a Novel Storage Mechanism under Dynamic Anaerobic-Aerobic Conditions |url=http://dx.doi.org/10.1128/aem.01012-15 |journal=Applied and Environmental Microbiology |volume=81 |issue=14 |pages=4809–4818 |doi=10.1128/aem.01012-15 |pmid=25956769 |pmc=4551194 |issn=0099-2240}}</ref> However, the exact mechanisms of these microbes to accumulate and use polyphosphate are not well understood.<ref name=":23"/>

== Known Bacterial PAOs ==

=== ''Candidatus'' ''Phosphoribacter'' (previously referred to as ''[[Tetrasphaera]]'' prior to 2022) ===
''Candidatus'' ''Phosphoribacter'' is a bacterial genus that has been found to be the dominant PAO associated with wastewater treatment worldwide, and has been found to often participate more in the biological removal of phosphorus than ''Candidatus'' Accumulibacter, contrary to previous understandings.<ref name=":12"/><ref name=":4"/><ref name=":23"/> This bacteria has been found to be a non-canonical (or fermentative/"fPAO") PAO, and universally lack the genetic potential to store PHA.<ref name=":12" /><ref name=":3">{{Cite journal |last1=Otieno |first1=Jeremiah |last2=Kowal |first2=Przemysław |last3=Mąkinia |first3=Jacek |date=2022-10-28 |title=The Occurrence and Role of Tetrasphaera in Enhanced Biological Phosphorus Removal Systems |journal=Water |volume=14 |issue=21 |pages=3428 |doi=10.3390/w14213428 |issn=2073-4441 |doi-access=free }}</ref> This genus was largely found to be capable of producing the fermentation products acetate, lactate, alanine, and succinate.<ref name=":3" /><ref>{{Cite journal |last1=Kristiansen |first1=Rikke |last2=Nguyen |first2=Hien Thi Thu |last3=Saunders |first3=Aaron Marc |last4=Nielsen |first4=Jeppe Lund |last5=Wimmer |first5=Reinhard |last6=Le |first6=Vang Quy |last7=McIlroy |first7=Simon Jon |last8=Petrovski |first8=Steve |last9=Seviour |first9=Robert J. |last10=Calteau |first10=Alexandra |last11=Nielsen |first11=Kåre Lehmann |last12=Nielsen |first12=Per Halkjær |date=March 2013 |title=A metabolic model for members of the genus Tetrasphaera involved in enhanced biological phosphorus removal |journal=The ISME Journal |volume=7 |issue=3 |pages=543–554 |doi=10.1038/ismej.2012.136 |issn=1751-7370 |pmc=3578573 |pmid=23178666}}</ref> Additionally, it is suggested that the [[amino acid]]s lysine, arginine, histidine, leucine, isoleucine, valine and phenylalanine may replace the canonical purpose of PHA as an energy substrate during oxic conditions, based on genomic potential and similarity to behavior of other microbial metabolisms.<ref name=":12" /> Alternatively, the compound [[cyanophycin]] may used as an energy substrate due to the ubiquity of cyanophycin-metabolizing enzymes encoded in the species.<ref name=":12" />

=== ''Candidatus'' ''Accumlibacter phosphatis'' ===
[[Candidatus Accumulibacter phosphatis|''Candidatus'' ''Accumulibacter phosphatis'']] is one of the most well-studied PAOs, and is responsible for the development of the classical PAO metabolic model which ''Ca.'' ''Phosphoribacter'' later contradicted.<ref>{{Cite journal |last1=He |first1=Shaomei |last2=McMahon |first2=Katherine D. |date=2011-02-21 |title=Microbiology of {{'}}''Candidatus'' accumulibacter{{'}} in activated sludge |url=http://dx.doi.org/10.1111/j.1751-7915.2011.00248.x |journal=Microbial Biotechnology |volume=4 |issue=5 |pages=603–619 |doi=10.1111/j.1751-7915.2011.00248.x |pmid=21338476 |pmc=3819010 |issn=1751-7915}}</ref> Formerly considered the most important PAO in waste treatment, the bacteria is highly abundant in wastewater treatment plants globally.<ref name=":23"/><ref>{{Cite journal |last1=Onnis-Hayden |first1=Annalisa |last2=Srinivasan |first2=Varun |last3=Tooker |first3=Nicholas B. |last4=Li |first4=Guangyu |last5=Wang |first5=Dongqi |last6=Barnard |first6=James L. |last7=Bott |first7=Charles |last8=Dombrowski |first8=Paul |last9=Schauer |first9=Peter |last10=Menniti |first10=Adrienne |last11=Shaw |first11=Andrew |last12=Stinson |first12=Beverly |last13=Stevens |first13=Gerry |last14=Dunlap |first14=Patrick |last15=Takács |first15=Imre |date=March 2020 |title=Survey of full-scale sidestream enhanced biological phosphorus removal (S2EBPR) systems and comparison with conventional EBPRs in North America: Process stability, kinetics, and microbial populations |url=https://onlinelibrary.wiley.com/doi/10.1002/wer.1198 |journal=Water Environment Research |language=en |volume=92 |issue=3 |pages=403–417 |doi=10.1002/wer.1198 |pmid=31402530 |s2cid=199539909 |issn=1061-4303|url-access=subscription }}</ref> It can consume a range of carbon compounds, such as acetate and propionate, under anaerobic conditions and store these compounds as [[polyhydroxyalkanoates]] (PHA) which it consumes as a carbon and energy source for growth using oxygen or nitrate as electron acceptor. Historically, the hyperaccumulation of phosphate by ''Ca''. ''Accumulibacter'' was seen as a stress response, but currently it is suggested that this behavior may play an ecological role.<ref>{{Cite bioRxiv |last1=da Silva |first1=Leonor Guedes |last2=Gamez |first2=Karel Olavarria |last3=Gomes |first3=Joana Castro |last4=Akkermans |first4=Kasper |last5=Welles |first5=Laurens |last6=Abbas |first6=Ben |last7=van Loosdrecht |first7=Mark C.M. |last8=Wahl |first8=Sebastian Aljoscha |date=2018-11-01 |title=Revealing metabolic flexibility of''Candidatus'' Accumulibacter phosphatis through redox cofactor analysis and metabolic network modeling |biorxiv=10.1101/458331 }}</ref> In combination with Ca. ''Phosphoribacter'', these two PAOs are considered to account for 24-70% of phosphorus removed from wastewater during treatment processing.<ref name=":4">{{Cite journal |last1=Fernando |first1=Eustace Y. |last2=McIlroy |first2=Simon Jon |last3=Nierychlo |first3=Marta |last4=Herbst |first4=Florian-Alexander |last5=Petriglieri |first5=Francesca |last6=Schmid |first6=Markus C. |last7=Wagner |first7=Michael |last8=Nielsen |first8=Jeppe Lund |last9=Nielsen |first9=Per Halkjær |date=August 2019 |title=Resolving the individual contribution of key microbial populations to enhanced biological phosphorus removal with Raman-FISH |journal=The ISME Journal |volume=13 |issue=8 |pages=1933–1946 |doi=10.1038/s41396-019-0399-7 |issn=1751-7370 |pmc=6776032 |pmid=30894691}}</ref>

=== ''Candidatus'' ''dechloromonas'' ===
[[Dechloromonas|''Candidatus'' ''Dechloromonas'']] species phosphoritropha and phosphorivorans are PAOs with classical metabolism genotype.<ref>{{Cite web |title=Midas Field Guide |url=https://www.midasfieldguide.org/guide/fieldguide/genus/dechloromonas |access-date=2023-07-07 |website=www.midasfieldguide.org}}</ref> ''Dechloromonas'' has been found in high abundances in wastewater treatment plants across the world.<ref>{{Cite journal |last1=Terashima |first1=Mia |last2=Yama |first2=Ayano |last3=Sato |first3=Megumi |last4=Yumoto |first4=Isao |last5=Kamagata |first5=Yoichi |last6=Kato |first6=Souichiro |date=2016 |title=Culture-Dependent and -Independent Identification of Polyphosphate-Accumulating &lt;i&gt;Dechloromonas&lt;/i&gt; spp. Predominating in a Full-Scale Oxidation Ditch Wastewater Treatment Plant |url=http://dx.doi.org/10.1264/jsme2.me16097 |journal=Microbes and Environments |volume=31 |issue=4 |pages=449–455 |doi=10.1264/jsme2.me16097 |pmid=27867159 |pmc=5158118 |issn=1342-6311}}</ref><ref>{{Cite journal |last1=Wang |first1=Baogui |last2=Jiao |first2=Erlong |last3=Guo |first3=Yu |last4=Zhang |first4=Lifang |last5=Meng |first5=Qingan |last6=Zeng |first6=Wei |last7=Peng |first7=Yongzhen |date=2020-07-02 |title=Investigation of the polyphosphate-accumulating organism population in the full-scale simultaneous chemical phosphorus removal system |url=http://dx.doi.org/10.1007/s11356-020-09912-9 |journal=Environmental Science and Pollution Research |volume=27 |issue=30 |pages=37877–37886 |doi=10.1007/s11356-020-09912-9 |pmid=32617817 |s2cid=220305344 |issn=0944-1344|url-access=subscription }}</ref><ref>{{Cite journal |last1=Stokholm-Bjerregaard |first1=Mikkel |last2=McIlroy |first2=Simon J. |last3=Nierychlo |first3=Marta |last4=Karst |first4=Søren M. |last5=Albertsen |first5=Mads |last6=Nielsen |first6=Per H. |date=2017-04-27 |title=A Critical Assessment of the Microorganisms Proposed to be Important to Enhanced Biological Phosphorus Removal in Full-Scale Wastewater Treatment Systems |journal=Frontiers in Microbiology |volume=8 |page=718 |doi=10.3389/fmicb.2017.00718 |pmid=28496434 |pmc=5406452 |issn=1664-302X |doi-access=free }}</ref><ref name=":23" /> The two species described here, ''Dechloromonas'' phosphoritropha and phosphorivans, are the two most abundant species in waste treatment within the genus.<ref>{{Cite journal |last1=Petriglieri |first1=Francesca |last2=Singleton |first2=Caitlin |last3=Peces |first3=Miriam |last4=Petersen |first4=Jette F. |last5=Nierychlo |first5=Marta |last6=Nielsen |first6=Per H. |date=December 2021 |title="Candidatus Dechloromonas phosphoritropha" and "Ca. D. phosphorivorans", novel polyphosphate accumulating organisms abundant in wastewater treatment systems |journal=The ISME Journal |language=en |volume=15 |issue=12 |pages=3605–3614 |doi=10.1038/s41396-021-01029-2 |pmid=34155336 |pmc=8630035 |issn=1751-7370}}</ref>

=== ''Candidatus'' ''accumulimonas'' (previously referred to as ''Candidatus'' ''Halomonas phosphatis'') ===
''Candidatus'' ''accumulimonas'' is a species of PAO with classical metabolism phenotype.<ref>{{Cite journal |last1=Nguyen |first1=Hien Thi Thu |last2=Nielsen |first2=Jeppe Lund |last3=Nielsen |first3=Per Halkjaer |date=October 2012 |title='Candidatus Halomonas phosphatis', a novel polyphosphate-accumulating organism in full-scale enhanced biological phosphorus removal plants: Polyphosphate-accumulating uncultured Halomonas |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1462-2920.2012.02826.x |journal=Environmental Microbiology |language=en |volume=14 |issue=10 |pages=2826–2837 |doi=10.1111/j.1462-2920.2012.02826.x|pmid=22827168 |url-access=subscription }}</ref><ref>{{Cite web |title=Midas Field Guide |url=https://www.midasfieldguide.org/guide/fieldguide/genus/halomonas |access-date=2023-07-07 |website=www.midasfieldguide.org}}</ref>

=== ''Microlunatis'' ''phosphovorus'' ===
[[Microlunatus phosphovorus|''Microlunatis'' ''phosphovorus'']] is a species of PAO with likely non-canonical PAO metabolism, however exact mechanisms have not been determined.<ref>{{Cite journal |last1=Nakamura |first1=K. |last2=Hiraishi |first2=A. |last3=Yoshimi |first3=Y. |last4=Kawaharasaki |first4=M. |last5=Masuda |first5=K. |last6=Kamagata |first6=Y. |date=January 1995 |title=Microlunatus phosphovorus gen. nov., sp. nov., a new gram-positive polyphosphate-accumulating bacterium isolated from activated sludge |journal=International Journal of Systematic Bacteriology |volume=45 |issue=1 |pages=17–22 |doi=10.1099/00207713-45-1-17 |issn=0020-7713 |pmid=7857797|doi-access=free }}</ref><ref name=":5">{{Cite journal |last1=Kawakoshi |first1=A. |last2=Nakazawa |first2=H. |last3=Fukada |first3=J. |last4=Sasagawa |first4=M. |last5=Katano |first5=Y. |last6=Nakamura |first6=S. |last7=Hosoyama |first7=A. |last8=Sasaki |first8=H. |last9=Ichikawa |first9=N. |last10=Hanada |first10=S. |last11=Kamagata |first11=Y. |last12=Nakamura |first12=K. |last13=Yamazaki |first13=S. |last14=Fujita |first14=N. |date=2012-08-23 |title=Deciphering the Genome of Polyphosphate Accumulating Actinobacterium Microlunatus phosphovorus |url=http://dx.doi.org/10.1093/dnares/dss020 |journal=DNA Research |volume=19 |issue=5 |pages=383–394 |doi=10.1093/dnares/dss020 |pmid=22923697 |pmc=3473371 |issn=1340-2838}}</ref><ref>{{Cite journal |last1=Zhong |first1=Chuanqing |last2=Zhang |first2=Peipei |last3=Liu |first3=Cheng |last4=Liu |first4=Meng |last5=Chen |first5=Wenbing |last6=Fu |first6=Jiafang |last7=Qi |first7=Xiaoyu |last8=Cao |first8=Guangxiang |date=2019 |title=The PolS-PolR Two-Component System Regulates Genes Involved in Poly-P Metabolism and Phosphate Transport in Microlunatus phosphovorus |journal=Frontiers in Microbiology |volume=10 |page=2127 |doi=10.3389/fmicb.2019.02127 |pmid=31572333 |pmc=6754071 |issn=1664-302X |doi-access=free }}</ref> Belonging to the same phylum as ''Ca.'' ''phosphoribacter'',  these two actinobacterial organisms exhibit similar metabolisms, however ''M.'' ''phosphovorus'' has been suggested to hyperaccumulate over ten times the amount of polyphosphate per cell mass dry weight compared to ''Ca.'' ''phosphoribacter'' or proteobacterial PAOs.<ref name=":5" />

=== ''Pseudomonas'' spp. ===
Some unnamed species of the ''[[Pseudomonas]]'' genus have been observed to exhibit PAO phenotypes.<ref name=":1">{{Cite journal |last1=Günther |first1=S. |last2=Trutnau |first2=M. |last3=Kleinsteuber |first3=S. |last4=Hause |first4=G. |last5=Bley |first5=T. |last6=Röske |first6=I. |last7=Harms |first7=H. |last8=Müller |first8=S. |date=April 2009 |title=Dynamics of Polyphosphate-Accumulating Bacteria in Wastewater Treatment Plant Microbial Communities Detected via DAPI (4′,6′-Diamidino-2-Phenylindole) and Tetracycline Labeling |url=http://dx.doi.org/10.1128/aem.01540-08 |journal=Applied and Environmental Microbiology |volume=75 |issue=7 |pages=2111–2121 |doi=10.1128/aem.01540-08 |pmid=19181836 |pmc=2663203 |issn=0099-2240}}</ref>

=== ''Paracoccus'' ''denitrificans'' ===
[[Paracoccus denitrificans|''Paracoccus'' ''denitrificans'']] has been observed to exhibit a non-canonical PAO phenotype.<ref name=":1" /><ref>{{Cite journal |last1=Barak |first1=Yoram |last2=van Rijn |first2=Jaap |date=March 2000 |title=Atypical Polyphosphate Accumulation by the Denitrifying Bacterium ''Paracoccus denitrificans'' |url=http://dx.doi.org/10.1128/aem.66.3.1209-1212.2000 |journal=Applied and Environmental Microbiology |volume=66 |issue=3 |pages=1209–1212 |doi=10.1128/aem.66.3.1209-1212.2000 |pmid=10698794 |pmc=91965 |issn=0099-2240}}</ref>

=== ''Quatrionicoccus australiensis'' ===
''Quatrionicoccus australiensis'' is a bacteria isolated from activated sludge which has been found to accumulate polyphosphate and PHA, thus likely having a classical PAO phenotype.<ref>{{Cite journal |last1=Maszenan |first1=A M |last2=Seviour |first2=R J |last3=Patel |first3=B K C |last4=Schumann |first4=P |date=2002 |title=Quadricoccus australiensis gen. nov., sp. nov., a beta-proteobacterium from activated sludge biomass. |journal=International Journal of Systematic and Evolutionary Microbiology |volume=52 |issue=1 |pages=223–228 |doi=10.1099/00207713-52-1-223 |issn=1466-5034|doi-access=free }}</ref><ref name=":2" />

=== ''Malikia granosa'' ===
''[[Malikia granosa]]'' is a bacteria isolated from activated sludge which has been found to accumulate polyphosphate and PHA, thus likely having a classical PAO phenotype.<ref>{{Cite journal |last1=Spring |first1=Stefan |last2=Wagner |first2=Michael |last3=Schumann |first3=Peter |last4=Kämpfer |first4=Peter |date=March 2005 |title=Malikia granosa gen. nov., sp. nov., a novel polyhydroxyalkanoate- and polyphosphate-accumulating bacterium isolated from activated sludge, and reclassification of Pseudomonas spinosa as Malikia spinosa comb. nov |journal=International Journal of Systematic and Evolutionary Microbiology |volume=55 |issue=Pt 2 |pages=621–629 |doi=10.1099/ijs.0.63356-0 |issn=1466-5026 |pmid=15774634|doi-access=free }}</ref>

=== ''Lampropedia spp.'' ===
''Lampropedia'' species, isolated from EBPR activated sludge, have been found to accumulate polyphosphate and PHA, though not to extreme degrees.<ref>{{Cite journal |last1=Stante |first1=L. |last2=Cellamare |first2=C. M. |last3=Malaspina |first3=F. |last4=Bortone |first4=G. |last5=Tilche |first5=A. |date=1997-06-01 |title=Biological phosphorus removal by pure culture of Lampropedia spp. |url=https://www.sciencedirect.com/science/article/pii/S004313549600351X |journal=Water Research |language=en |volume=31 |issue=6 |pages=1317–1324 |doi=10.1016/S0043-1354(96)00351-X |issn=0043-1354|url-access=subscription }}</ref>

=== ''Candidatus Microthrix'' ===
''Candidatus Microthrix'', identified in more than one EBPR activated sludge source, is a filamentous bacteria suspected to be responsible for phosphate removal during the bulking phase of EBPR, where other PAOs decrease in abundance.<ref>{{Cite journal |last1=Wang |first1=Juan |last2=Qi |first2=Rong |last3=Liu |first3=Miaomiao |last4=Li |first4=Qian |last5=Bao |first5=Haipeng |last6=Li |first6=Yaming |last7=Wang |first7=Shen |last8=Tandoi |first8=Valter |last9=Yang |first9=Min |date=2014 |title=The potential role of 'Candidatus Microthrix parvicella' in phosphorus removal during sludge bulking in two full-scale enhanced biological phosphorus removal plants |journal=Water Science and Technology |volume=70 |issue=2 |pages=367–375 |doi=10.2166/wst.2014.216 |issn=0273-1223 |pmid=25051486|doi-access=free }}</ref>

=== ''Gemmatimonas aurantiaca'' ===
''[[Gemmatimonas aurantiaca]]'' is a bacteria isolated from activated sludge that has been observed to accumulate polyphosphate granules.<ref>{{Cite journal |last1=Zhang |first1=Hui |last2=Sekiguchi |first2=Yuji |last3=Hanada |first3=Satoshi |last4=Hugenholtz |first4=Philip |last5=Kim |first5=Hongik |last6=Kamagata |first6=Yoichi |last7=Nakamura |first7=Kazunori |date=2003 |title=Gemmatimonas aurantiaca gen. nov., sp. nov., a Gram-negative, aerobic, polyphosphate-accumulating micro-organism, the first cultured representative of the new bacterial phylum Gemmatimonadetes phyl. nov. |journal=International Journal of Systematic and Evolutionary Microbiology |volume=53 |issue=4 |pages=1155–1163 |doi=10.1099/ijs.0.02520-0 |issn=1466-5034|doi-access=free }}</ref>

==References==
{{Reflist}}

{{DEFAULTSORT:Polyphosphate-Accumulating Organisms}}
[[Category:Biotechnology]]
[[Category:Waste treatment technology]]
[[Category:Bacteriology]]
[[Category:Phosphorus]]