微生物中多聚磷酸鹽細菌加強生物廢水中清除磷的能力畢業(yè)論文外文翻譯

1、微生物中多聚磷酸鹽細菌加強生物廢水中清除磷的能力摘要活性污泥處理工藝在厭氧和有氧（厭氧好氧法）環(huán)境交替進行方法可以提高的廢水中磷的去除效果（ebpr）。據(jù)了解，聚磷菌（pab）在厭氧好氧法中發(fā)揮重要作用。本文對微生物的新陳代謝和群落結(jié)構(gòu)描述有限，主要突出在ebpr過程中的選擇作用。微生物在厭氧好氧法中，碳源豐富的厭氧環(huán)境和碳源缺乏的好氧環(huán)境交替進行，促進了聚磷菌重要的新陳代謝特征。其中包括有機質(zhì)的吸收，以及把它們轉(zhuǎn)化為細胞內(nèi)聚磷菌自身儲存的pha和水解產(chǎn)物，并在厭氧條件下釋放能量。假設(shè)細胞內(nèi)神經(jīng)的功能是作為調(diào)節(jié)器，調(diào)節(jié)細胞的氧化還原平衡。能另儲存有助與聚磷菌在厭氧環(huán)境中維持氧化還原平衡，吸收各

2、種類型的有機質(zhì)，增強微生物的選擇功能。聚磷菌不能由其他物質(zhì)組成，各種各樣的細菌除外。要確定ebpr工藝中微生物群落的結(jié)構(gòu)，需要通過分子技術(shù)細心觀察在各種ebpr中，每一種聚磷菌的活動情況，因為許多聚磷菌都是不可用的培養(yǎng)基。關(guān)鍵詞： 活性污泥 厭氧好氧法 生態(tài)學(xué) 生物加強清除磷酸鹽 微生物群落 聚磷菌 廢水處理工藝當(dāng)過量的含磷廢水排入不外流的水體，湖泊或內(nèi)陸海水時會造成水體富營養(yǎng)化。（海藻過量生長繁殖）要在污水排入水體之前去處水中的磷。厭氧、好氧條件交替控制活性污泥法已經(jīng)成功的用于提高水體中磷的去處效果。這種厭氧好氧交替運行的工藝已經(jīng)得到普遍運用，在厭氧段、好氧段池體的空間布局以及利用設(shè)備的污泥

3、回流系統(tǒng)等方面有顯著效果。例如這種被稱為ebpr的厭氧好氧或厭氧缺氧過程。據(jù)研究顯示，聚磷菌在ebpr厭氧好氧法中具有重要作用。ebpr要實現(xiàn)高而穩(wěn)定的性能，必須保持聚磷菌在系統(tǒng)中的活性?；镜膮捬鹾醚醴ǖ膱D表可以說明其中的問題。這一過程的特點是結(jié)構(gòu)上存在一種厭氧階段，保持絕對厭氧條件,沒有氧氣,也沒有no2-/no3-為活性污泥細菌提供電子受體。有機質(zhì)的供應(yīng)一部分來自進入?yún)捬醵蔚奈鬯?，一部分是反?yīng)器中回流污泥補充碳源。在ebpr過程中，加快厭氧段有機質(zhì)的吸收率是細菌得到微生物的關(guān)鍵。這種pab繁殖機制可以如下表述。通常，在厭氧階段活性污泥向污水中釋磷，同時吸收有機質(zhì)。在后期的好氧段，吸收的磷

4、，遠大于在厭氧段前期釋放的磷。污水中的磷被去處了，它作為一種物質(zhì)積累到細胞里。多聚磷酸鹽是一種高能化合物，它水解能為細胞多種生化反應(yīng)提供足夠的能量。在厭氧階段，多聚磷化物的水解使pab獲得足夠的能量以滿足它們吸收有機質(zhì)。沒有電子受體（氧，no2-/no3-）好氧細菌和反硝化細菌沒有足夠的能量利用有機質(zhì)，也不能完成pab的利用。因此采用厭氧段使pab具有優(yōu)勢，更好的處理污泥中的磷。處理系統(tǒng)中的過量污泥并收集含高濃度磷的污泥，這樣可以提高除磷效率。數(shù)量極少的純培養(yǎng)基在ebpr中扮演重要角色。ebpr中新陳代謝方面的研究主要是基于對濃集的混合培養(yǎng)基的研究而不是純培養(yǎng)基。這方面的不足就是缺乏準(zhǔn)確的有關(guān)

5、ebpr的微生物學(xué)和生物化學(xué)方面的資料。因此，ebpr中pab的微生物學(xué)變的不容易理解。ebpr工藝中聚磷菌的碳代謝雖然厭氧好氧法對于ebpr從工程角度來說已經(jīng)是成熟的工藝方法，但它還不能清楚的解釋一些微生物方面的定義 在微生物的新陳代謝過程中，厭氧段通過廢水中細菌的酶化作用完成了碳化合物的吸收。由于污泥在厭氧條件下完成了和碳化合物的充分接觸，生物體能更有效的利用碳質(zhì)，在厭氧環(huán)境中占據(jù)優(yōu)勢。因此，在厭氧條件下，pab能實現(xiàn)對碳質(zhì)的高速吸收的原因是我們一直關(guān)注的重要課題。據(jù)了解，短鏈脂肪酸醋酸有利于ebpr中碳的來源，并且在ebpr中新陳代謝已經(jīng)作為碳質(zhì)的模型正在進行研究。在這項研究上有一個決定

6、性問題，就是事實上沒有一個細菌可以從ebpr工藝中孤立起來，來顯示ebpr污泥的主要特征。任何孤立的純文化每一個細菌在掩樣楊。這就是ebpr中的微生物被研究原因。這種高濃度pab培養(yǎng)基通常從模擬實驗獲得，模擬厭氧好氧法處理廢水。在一組醋酸作為碳源的厭氧實驗中，含高濃度pab的活性污泥利用短鏈迅速吸收醋酸，在細胞內(nèi)累計phas釋放磷。吸收的醋酸作為phs轉(zhuǎn)化和積累。據(jù)發(fā)現(xiàn)在高濃度pab中phas的積累由4部分組成3hb, 3hv, 3h2mb,和3h2mv。分析這些phas的化學(xué)成分并證明是由上述四個單位組成。至于碳水化合物，有人證明了它存在于厭氧好氧活性污泥中，當(dāng)醋酸作為碳源被吸收時，高濃度p

7、has在厭氧段形成。醋酸轉(zhuǎn)化為phas需要減少電能，因為phas比醋酸不易合成。為了解釋在沒有電子受體情況下減少電能這個過程，mino 和arun提出一個假設(shè)模型。該模型中，在假設(shè)降低phas能量情況下，厭氧環(huán)境中存儲的乙酰部分氧化為二氧化碳。這種模式現(xiàn)在被稱為mino模型,其相關(guān)的一些研究者已證實，理論化學(xué)計量學(xué)根據(jù)模型依照顯示能定量地解釋通過pab 污泥將醋酸鹽和糖朊轉(zhuǎn)換成pha ，成功地采用了類似的概念來解釋在ebpr中厭氧吸收率問題。ebpr中厭氧碳新陳代謝模型另一個假說是由matsuo、comeau和 wentze提出來的。根據(jù)這種假說，tca循環(huán)假設(shè)在厭氧條件下進行，把一部分醋酸氧

8、化成二氧化碳并減少能量。這種模式通常只在厭氧或好氧環(huán)境下進行循環(huán)。對于這一矛盾的熱力學(xué)理論，人們已經(jīng)在厭氧或好氧環(huán)境中發(fā)現(xiàn)完整的tca循環(huán)。這些微生物利用硫元素和電子受體通過氧化醋酸完全轉(zhuǎn)化二氧化碳。據(jù)認為,這種情況的產(chǎn)生主要是要求減少能量生成代謝，就像mino模型；而不是tca循環(huán)那種預(yù)言。原因如下：（1）這種理論能很好地解釋實驗觀察到醋酸厭氧吸收率的現(xiàn)象，通過高濃度pao，pha的形成、乙二醇的應(yīng)用、二氧化碳的生成。（2）13c示蹤實驗器材的使用指出：醋酸通過厭氧污泥吸收的不是二氧化碳,因此不會通過循環(huán)進行代謝。（3）實驗用13c-器材,顯示乙二醇轉(zhuǎn)化為厭氧代謝的淤泥。另一方面,有證據(jù)表明

9、有可能介入的局部tca循環(huán)發(fā)電,減少電能是在ebpr厭氧階段。即13c的碳被轉(zhuǎn)化高濃度pab，醋酸-污泥濃縮被認為是絕對厭氧條件下釋放二氧化碳。迄今為止,這是唯一可能的實驗結(jié)果顯示了運行周期邁進的階段厭氧ebpr的過程. 循環(huán)的功能邁進的碳排放源的厭氧吸收率以及對微生物的篩選過程ebpr有待進一步調(diào)查. ebpr的過程中,受到其他微生物碳厭氧環(huán)境和豐富的碳有氧環(huán)境惡劣. 這一交替的、綜合和退化三種形式臨時醫(yī)院引起循環(huán)和新陳代謝,是通過這些微生物完成的。這種微生物循環(huán)是能量的消耗，而不是微生物的能源利用效率。然而，這種微生物循環(huán)使pab在厭氧好氧環(huán)境中進行選擇。如何解釋這一規(guī)定在細胞循環(huán)代謝是由

10、pramanik發(fā)現(xiàn)的。這一模式包含了一整套涉及細胞代謝途徑和能源需求及高分子合成代謝物如何運輸并跨越細胞膜. 模型不僅支持假設(shè)，還提供了生物代謝途徑,以及能源供應(yīng),而且還表明,在代謝途徑中規(guī)則成立。 強化社會結(jié)構(gòu)生物學(xué)微生物磷清除過程 不動桿菌首次作為pab被提出來，很少有研究人員質(zhì)疑不動桿菌是否僅僅是ebpr中的一種細菌。它有可能被認為高磷ebpr淤泥清除能力是一組由微生物,試圖找出幾個不動桿菌以外生物體?，F(xiàn)在,新的強有力的工具的運用,對微生物體結(jié)構(gòu)的分析,了開發(fā)和利用ebpr淤泥。其中化學(xué)分析方法與分子分析與方法,如熒光在原地交錯(漁)、圖書館克隆方法、熱梯度電泳(dgge)、終端限制碎

11、片長度白細胞(t生物)等。高ebpr濃度污泥的微生物多樣性已成功利用這種新技術(shù)。分子分析適用于活性污泥結(jié)構(gòu)的特點分析，醌生物樣品的種類數(shù)量可確定,應(yīng)當(dāng)明確反映研究樣本形態(tài)組成。有人建議由幾個不同ebpr污泥組織，醌最豐富、q-8,僅占總數(shù)約pab污泥的31%（磷含量1.94、60mg懸浮固體); 第二個最豐富的人,q-10,占8.5%; 第三、mk-8(h4)、6.5%。換句話說,有幾個不同污泥微生物群體,已確認的其他研究人員也用它，t-樣品的分離,pcr-16s更直接表明不同的人口，數(shù)量約19至24年各主要見于高度pab污泥濃縮。（磷含量、懸浮固體12%）。dgge的技巧也顯示分離,擴大碎片

12、rdna和ebpr淤泥中的一些主要的dna序列不同的碎片,暗示研究ebpr結(jié)構(gòu)多樣性。這些成果有力地表明,沒有一個是pab或基因型數(shù)量有限,但也會涉及各類細菌。bond應(yīng)用pcr克隆啟動兩種活性污泥,高磷清除績效果以及典型的新陳代謝,pab等。他們發(fā)現(xiàn)這個組織數(shù)量相當(dāng)驚人，高磷污泥比低磷污泥大幅度提高了。這一結(jié)果顯示,有特定集團作用. 然而,只有14%的被占領(lǐng)，基因總數(shù)在少數(shù)的高磷污泥。現(xiàn)在還不能確定這能否為觀察到高磷清除績效。討論之前,有報道ebpr結(jié)構(gòu)中有一種壓倒優(yōu)勢(細菌總數(shù)81%)。就目前而言,這是唯一的一個案例,主要是細菌的主要表現(xiàn)是ebpr負責(zé)。用dapi進行雙重染色與rrna的探

13、針，針對不同對象確定細菌組繁殖在原地。因此,在檢驗污泥時這兩個群體被認為在累積磷。報告說,陽性菌g+c高含量dna扮演重要角色,因為較高ebpr發(fā)生這種細菌組發(fā)現(xiàn)了一個克隆ebpr的過程。大多數(shù)基因陽性菌具有很強的dnag+c含量，依據(jù)實驗樣品的rdna碎片從高濃度-污泥濃縮(磷含量,12%的懸浮固體)、污泥很低磷酸鹽含量(2%懸浮固體)。認為陽性菌具有很強的dnag+c的結(jié)構(gòu)不只是pab的重要組成部分。醌分析使用方法,該市污水處理廠污泥運作模式相類似,不論對方采取何種過程污泥 。從淤泥中ebpr程序和常規(guī)程序分子形態(tài)十分相似。比較不同啟動模式醌淤泥建議采用的厭氧階段進入，全面啟動常規(guī)污泥過程

14、不會導(dǎo)致大量細胞變化。上述這些結(jié)果又會導(dǎo)致下述結(jié)論:細胞擁有獨特的新陳代謝特點,把生物和微生物群體分開。最可能的阿爾法-、試用、伽瑪射線的類別和陽性菌具有很強的dnag+c的內(nèi)特性。展望未來這次審查顯示,pab不是由少數(shù)受限制物質(zhì)組成,但也會轉(zhuǎn)化成各類細菌。在ebpr中細菌的種類不同,負責(zé)功能不同。在ebpr過程中，明確界定微生物ebpr社會結(jié)構(gòu)和過程的機制來描述pab生態(tài)選擇，在研究加強和行為發(fā)生個別種類對ebpr的需要。因為許多pab似乎是不可能的結(jié)構(gòu),只有分子方法能實現(xiàn)這些目的。這可能意味著,新陳代謝的關(guān)鍵基因的ebpr常見細菌不同。最有趣最重要的是確定這種基因并且找出它是怎樣的規(guī)則。m

15、icrobial selection of polyphosphate-accumulating bacteria in activated sludge wastewater treatment processes for enhanced biological phosphate removalabstract:activated sludge processes with alternating anaerobic and aerobic conditions (the anaerobic-aerobic process) have been successfully used for

16、enhanced biological phosphate removal (ebpr) from wastewater. it is known that polyphosphate-accumulating bacteria (pab) play an essential role for ebpr in the anaerobic-aerobic process. the present paper reviews limited information available on the metabolism and the microbial community structure o

17、f ebpr, highlighting the microbial ecological selection of pab in ebpr processes. exposure of microorganisms to alternate carbon-rich anaerobic environments and carbon-poor aerobic environments in the anaerobic-aerobic process induces the key metabolic characteristics of pab, which include organic s

18、ubstrate uptake followed by its conversion to stored polyhydroxyalkanoate (pha) and hydrolysis of intracellular polyphosphate accompanied by subsequent pi release under anaerobic conditions. intracellular glycogen is assumed to function as a regulator of the redox balance in the cell. storage of gly

19、cogen is a key strategy for pab to maintain the redox balance in the anaerobic uptake of various organic substrates, and hence to win in the microbial selection. acinetobacter spp., microlunatus phosphovorus, lampropedia spp., and the rhodocyclus group have been reported as candidates of pab. pab ma

20、y not be composed of a few limited genospecies, but involve phylogenetically and taxonomically diverse groups of bacteria. to define microbial community structure of ebpr processes, it is needed to look more closely into the occurrence and behavior of each species of pab in various ebpr processes ma

21、inly by molecular methods because many of pab seem to be impossible to culture. key words: activated sludge, anaerobic-aerobic process, ecological selection, enhanced biological phosphate removal (ebpr), lampropedia, microbial community, (phas), polyphosphate-accumulating bacteria, wastewater treatm

22、ent phosphate can cause eutrophication (extraordinary growth of algae) when it is excessively discharged into closed natural water bodies like lakes and inland seas. to control eutrophication, phosphate removal from wastewater is often required before wastewater is discharged to the receiving water

23、bodies. activated sludge processes with alternating anaerobic and aerobic conditions have been successfully used for enhanced biological phosphate removal (ebpr) from wastewater. this anaerobic-aerobic alternation can be achieved either by spatial configuration of anaerobic and aerobic zones in seri

24、es in continuous flow systems with sludge recycle or by temporal arrangement of anaerobic and aerobic periods in sequence batch reactors. such ebpr processes are referred to as the anaerobic-aerobic or anaerobic-oxic process. it has been shown in previous studies that polyphosphate-accumulating bact

25、eria (pab) play an essential role for ebpr in the anaerobic-aerobic process. to achieve high and stable ebpr performance, it is essential to maintain pab in the system. a basic configuration of the anaerobic-aerobic process is schematically shown in fig. a. this process is structurally characterized

26、 by the presence of an anaerobic stage in which absolute anaerobic conditions are kept with neither oxygen nor no2-/no3- available as electron acceptor for activated sludge bacteria. organic substrates are supplied from influent wastewater into the anaerobic stage and the return sludge comes into co

27、ntact with the carbon source only in the anaerobic stage. faster uptake of organic substrates in the anaerobic stage is the key for bacteria to win in the microbial selection in the ebpr process. the mechanism of proliferation of pab can be described as follows. it is typically observed in the anaer

28、obic stage that the activated sludge releases pi to the bulk solution with concomitant uptake of organic substrates. in the subsequent aerobic stage, it takes up more pi than has been released in the previous anaerobic stage. the pi removed from the wastewater is accumulated in the cell as polyp. po

29、lyphosphate is a high-energy compound and its hydrolysis can supply energy to various biochemical reactions in the cell. in the anaerobic stage, the hydrolysis of intracellular polyp enables pab to obtain the energy they need to take up organic substrates. without electron acceptors (oxygen, no2-/no

30、3-), aerobic bacteria and denitrifying bacteria are unable to obtain the energy required for the utilization of organic substrates, and they are thus unable to compete with pab. therefore, the introduction of the anaerobic stage leads to the precedence of pab and to a rise in phosphorus content of t

31、he sludge. by withdrawing the phosphorus-rich sludge from the system as excess sludge, high phosphate removal efficiency can be achieved. fig. 1. a) basic concept of anaerobic-aerobic process for ebpr. b) behavior of the basic substances in ebpr. toc, total organic carbon present in the bulk solutio

32、n; po4-p, orthophosphate present in the bulk solution; glycogen, glycogen stored in the cells; pha, polyhydroxyalkanoates stored in the cells. although the anaerobic-aerobic process for ebpr is an established process from an engineering point of view, it has not been clearly defined in microbiologic

33、al terms. for example, the phylogenetic or taxonomic groups responsible for ebpr have not been identified, and general structures of the ebpr microbial community have not been successfully described yet. very few pure cultures have been isolated as candidates of pab playing a key role in ebpr proces

34、ses. studies on metabolic aspects of ebpr have been mainly done based on enriched mixed cultures but not on pure cultures. this has resulted in lack of definitive and conclusive information about the microbiology and biochemistry of ebpr. thus, the mechanism of microbial ecological selection of pab

35、in ebpr processes has been understood very poorly. the present paper reviews limited information available on the metabolism and the microbial community structure of ebpr, highlighting the selection of pab in ebpr processes. carbon metabolism adopted by polyphosphate-accumulating bacteria in ebpr pr

36、ocessesin terms of microbial metabolism, the anaerobic stage involves the uptake of organic substrates from wastewater by bacteria. since the sludge comes into contact with organic substrates under anaerobic conditions, organisms that can utilize organic substrates more rapidly in an anaerobic envir

37、onment gain precedence. therefore, the reason why pab can achieve a very high rate of organic substrate uptake under anaerobic conditions has been a major subject of concern. it has been well known that short chain fatty acids like acetate are favorable carbon sources for ebpr, and acetate metabolis

38、m has been intensively studied as a model carbon metabolism substrate in ebpr. a critical problem in such studies lays in the fact that none of the bacteria isolated from ebpr processes have exhibited all the key characteristics of the ebpr sludge and that any isolated pure cultures had never been v

39、erified to be primarily responsible for ebpr in an anaerobic-aerobic system until recently . this is the reason that metabolic aspects of ebpr have been studied using mixed cultures enriched with pab. such pab-enriched cultures have usually been obtained from lab-scale activated sludge reactors simu

40、lating the anaerobic-aerobic process fed with synthetic wastewater. in anaerobic batch experiments with acetate as the carbon source, the activated sludge enriched with pab typically take up acetate rapidly, accumulate phas in the cell, consume previously stored intracellular carbohydrate, and relea

41、se pi as a result of utilization of stored polyp. these typical behaviors of key substances involved in ebpr are graphically shown in fig. the acetate taken up is converted to and accumulated as phas. satoh et al. found that the phas accumulated in the pab-enriched sludge are composed of four monome

42、ric units: 3hb, 3hv, 3h2mb, and 3h2mv. inoue et al. analyzed the chemical structure of these phas by nmr and verified that they are co-polymers composed of the above four monomeric units. as for carbohydrate, liu et al. proved enzymologically that the carbohydrate stored in the anaerobic-aerobic slu

43、dge is a polymer of glycosyl units with the alpha-1,4- and the alpha-1,6-linkages, or glycogen. when acetate is fed as the carbon source, 3hb-rich phas are formed in the anaerobic stag. the conversion of acetate to pha requires reducing power, because pha is a more reduced compound than acetate. to

44、explain the source of the reducing power under the conditions without electron acceptors, a hypothetical model was proposed by mino et al. and arun et al. in that model, anaerobic degradation of stored glycogen to acetyl-coa as well as its partial oxidation to co2 is assumed to account for the gener

45、ation of the reducing power for pha synthesis. this model is now called the mino model, and its relevance has been confirmed by several researchers. the outlines of the model are shown in fig. the theoretical stoichiometry based on the model could quantitatively explain the observed conversions of a

46、cetate and glycogen to pha by pab-enriched sludges, as shown in the table. satoh et al. successfully applied a similar concept to explain the anaerobic uptake of propionate in ebpr processes (see the table). fig. 3. a conceptual model for anaerobic carbon metabolism in an ebpr process (after referen

47、ces). another hypothesis was postulated by matsuo et al., comeau et al. , and wentzel et al. to account for the source of the reducing power in anaerobic acetate metabolism. according to this hypothsis, the tca cycle is assumed to operate under anaerobic conditions in order to oxidize a part of acet

48、ate to co2 and to generate reducing power in the form of nadh. this model is referred to as the comeau-wentzel model. usually the tca cycle operates only under aerobic or anoxic conditions. the oxidation of succinate to fumarate in the tca cycle requires a terminal electron acceptor with a redox pot

49、ential (e0) more positive than that of fumarate/succinate couple (+32 mv). only o2 (o2/h2o, e0 = +818 mv), no3- (no3-/no2-, e0 = + 433 mv), and no2- (no2-/n2-, e0 = +970 mv) appear to meet these conditions. contradictory to this thermodynamic theory, a complete tca cycle has been found to operate in

50、 some anaerobic eubacteria or archae. these microorganisms can oxidize acetate completely to co2 via the tca cycle by utilizing elemental sulfur, thiosulfate, or sulfate as electron acceptor. it is believed, however, that major part of the required reducing power should be generated through the glyc

51、ogen metabolism as described in the mino model rather than through the tca cycle as predicted by the comeau-wentzel model. the reasons are as follows: 1) the theoretical stoichiometry for the glycogen metabolism can explain very well the experimentally observed anaerobic acetate uptake, pha formatio

52、n, glycogen utilization, and co2 production by pao-enriched sludges ; 2) a 13c tracer experiment using nmr indicated that the acetate taken up by the sludge anaerobically was not oxidized to co2 and thus not metabolized through the tca cycle, and 3) experiments using 13c-nmr demonstrated that glycog

53、en is involved in the anaerobic metabolism of ebpr sludges. on the other hand, there is evidence that indicates the possibility of partial involvement of the tca cycle in the generation of reducing power by pab in the anaerobic stage of the ebpr process. namely, 13c-labeled carbon in the acetate fed

54、 to a pab-enriched sludge was found to be released as co2 under absolute anaerobic conditions. so far, this is the only experimental result indicating the possible functioning of the tca cycle in the anaerobic phase of the ebpr process. the function of the tca cycle in the anaerobic uptake of carbon

55、 sources by pab as well as its contribution to the microbial selection in the ebpr process remains to be further investigated. in the ebpr process, microorganisms are exposed to alternate carbon-rich anaerobic environments and carbon-poor aerobic environments. by this alternation, synthesis and degr

56、adation of three kinds of biopolymers (polyp, pha, and glycogen) are induced and metabolic cycling through these biopolymers is established in microorganisms. such metabolic cycling is energy consuming and not favorable for microorganisms in terms of energy utilization efficiency. ecologically, howe

57、ver, this metabolic cycling enables pab to win in the microbial selection in the anaerobic-aerobic process. to explain how this metabolic cycling is regulated in the cell, a metabolic flux model was developed by pramanik et al. this model contains a complete set of metabolic pathways involved in bio

58、synthesis and energy production and accounts for energy requirements for macromolecule synthesis and metabolite transport across the cell membrane. the model not only supports the hypothesis that the biopolymer metabolism provides a means for pab to balance intracellular energy supplies, but also su

59、ggest pathways at which metabolic regulation should occur. microbial community structure of enhanced biological phosphate removal processwhen acinetobacter was first proposed as pab, there were very few researchers who raised the question of whether acinetobacter is the only bacterium responsible for ebpr. it may have been somehow assumed that ebpr sludges with high phosphate removal capability were dominated by a single group of microorganism