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The relationship between predominant physiological types of prokaryotes in marine sediments and propionate degradation through sulfate reduction, fermentation, and methanogenesis was studied in marine sediments. Propionate conversion was assessed in slurries containing sediment from three different biogeochemical zones of Aarhus Bay, Denmark. Sediment slurries were amended with 0, 3 or 20 mM sulfate and incubated at 25°C and 10°C for 514 - 571 days. Methanogenesis in the sulfate zone and sulfate reduction in the methane zone slurries was observed. Both processes occurred simultaneously in enrichments originating from samples along the whole sediment. Bacterial community analysis revealed dominance of Desulfobacteraceae and Desulfobulbaceae members in sulfate-amended slurries incubated at 25°C and 10°C. Cryptanaerobacter belonging to Peptococcaceae family dominated sulfate-free, methanogenic slurries at 25°C, whereas bacteria related to Desulfobacteraceae were dominant at 10°C. Archaeal community analysis revealed prevalence of different genera belonging to Methanomicrobiales in slurries incubated at different temperatures and amended with different sulfate concentrations. Methanosarcinaceae were only detected in the absence of sulfate. In summary, Aarhus Bay sediment zones contain sulfate reducers, syntrophs and methanogens interacting with each other in the conversion of propionate. Our results indicate that in Aarhus Bay sediments Cryptanaerobacter degrades propionate in syntrophic association with methanogens.

In this work, a dynamic calculation of the thermodynamics of the considered reactions in ADM1 highlighted the role of hydrogen on VFA degradation. In ADM1, a hydrogen inhibition factor based on its concentration is used to represent the same effect. Our comparison of a thermodynamic-based against the simpler concentration-based inhibition factor during dynamic simulations validates the ADM1 approach. Our results also show the need to correct the VFAs Gibbs energies with temperature if a thermodynamic-based inhibition is to be used. The thermodynamics of butyrate degradation under both experimental and simulated conditions suggest the unfeasibility of the reaction and the need for a revision of the current pathway biochemistry.

酪酸を単一炭素源として用い,酪酸馴養メタン発酵汚泥から水素資化性メタン生成細菌BHM-1株を得,BHM-1株の微生物学的性状を調べ,酪酸分解菌との微生物相互の役割について微生物生態学的見地から考察した。酪酸に対するメタン発酵においてメタンの生成には2つのピークがあり,ピークIは酪酸分解菌と水素資化性メタン生成細菌との共生関係によるメタン生成,ピークIIは酢酸資化性メタン生成細菌かあるいは酢酸分解菌と水素資化性メタン生成細菌によるメタン生成であることが推察された。ピークIに着目して検討した結果,分離したBHM-1株はMethanobacterium formicicumに極めて類縁な微生物であった。酪酸分解菌とBHM-1株からなるコロニーの液体培養から,酪酸分解菌とBHM-1株での共生関係が示唆された。

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007, Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2007, Bütirat, organik maddenin ayrışmasında metanojenlerin mevcut olduğu havasız arıtma koşullarında önemli bir ara üründür. Havasız reaktörlerde metan üretiminin %60’a varan kısmı bütirattan kaynaklanabilir. Bu tezde sunulan çalışmanın amacı havasız biyoreaktörlerde önemli bir ara ürün olan bütiratı ayrıştıran sintrofik mikrobiyal topluluğun popülasyon dinamiğini detaylı bir şekilde ortaya çıkarmaktır. Bu kapsamda konvansiyonel kültür çalışmalarıyla birlikte kültür çalışması gerektirmeyen moleküler teknikler kullanılmıştır. Ayrıca, atıksularda yaygın olarak gözlenen sülfatın sintrofik bütirat ayrışmasına etkisi de incelenmiştir. Yukarı akışlı Havasız Çamur Yataklı (UASB) Reaktörler ve farklı inkübasyon teknikleri kullanılarak biyokütle bütirata alıştırılmış ve moleküler biyolojik teknikler ile bu biyokütlenin karakterizasyonu yapılmıştır. Sintrofik butirat ayrıştıran mikrobiyal topluluktaki türler konvansiyonel ve moleküler teknikler ile kalitatif ve kantitatif olarak belirlenmiştir. Bu teknikler, MPN: En Uygun Sayı, PCR-RFLP: Polimeraz Zincir Reaksiyonu-Restriksiyon Parça Uzunluk Polimorfizm, DGGE: Denatüre Gradyan Jel Elektroforezi, Q-PCR: Kantitatif PCR, ve SIP: Stabil İzotop İşaretlemesi’dir. Yapılan bu çalışmada bütiratı ayrıştıran topluluğun bilinen organizmalardan farklı ve çeşitliliğinin fazla olduğu bulunmuştur. Aynı zamanda bu çeşitlilik filogenetik olarak da farklı gruplara düşmektedir. Bulgular, sintrofik olarak bütiratı ayrıştıran mikrobiyal topluluğun düşünülenden daha geniş olduğunu göstermektedir. Bu sintrofik topluluğun yapısının anlaşılması atıksuların havasız arıtılmasına ışık tutmakta ve havasız prosesin geliştirilmesinde önemli bir adım olabilir., An important intermediate of organic matter conversion under methanogenic conditions is butyrate; which may account for up to 60% of methanogenesis in anaerobic bioreactors. The aim of this research was to get a deeper and better insight about the population dynamics of syntrophic butyrate oxidizing microbial consortia in anaerobic bioreactors using conventional culture dependent and the culture independent molecular techniques. Moreover, the investigation was extended to examining the combined cultivation under methanogenic and sulfidogenic conditions. For this purpose, biomass adapted to butyrate using Upflow Anaerobic Sludge Blanket (UASB) bioreactors and different incubation techniques and then molecular techniques were used to characterize this butyrate adapted biomass. The use of combination of conventional and molecular techniques (MPN: Most Probable Number, PCR-RFLP: Polymerase Chain Reaction-Restricted Fragment Length Polymorphism, DGGE: Denaturing Gradient Gel Electrophoresis, Q-PCR: Quantitative PCR, and SIP: Stable Isotope Probing) enabled us to identify several species in an anaerobic syntrophic butyrate degrading-consortium, both qualitatively and quantitatively. The main player for the butyrate degradation was attained into several species demonstrated that this functional group of organisms is not fallen into the phylogenetically consistent groups, rather spread out in to several lineages. Therefore, it was evident that the syntrophic butyrate degrading community is larger than it was thought before. Better understanding of this community structure shed some light on anaerobic treatment of wastewaters and may lead to improvements this process as well., Doktora, PhD

The effect of temperature on butyrate degradation was investigated in defined syntrophic cultures of Syntrophomonas wolfei co-cultured with either Methanospirillum hungatei or Desulfovibrio strain Gll. The temperature response was almost linear in an Arrhenius plot from 20 – 37 °C. Below 20°C, almost no butyrate metabolism occurred. Measurements of hydrogen partial pressures in the cultures indicated that S. wolfei was more temperature sensitive than the hydrogen scavenging bacteria.