Catabolism and interactions of syntrophic propionate- and acetate oxidizing microorganisms under mesophilic, high-ammonia conditions.

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for future research into ammonia tolerance, mobility, aggregate formation and interspecies cooperation.

Terrestrial dissolved organic matter inputs accompanied by dissolved oxygen depletion and declining pH exacerbate CO2 emissions from a major Chinese reservoir.

Terrestrial inputs and subsequent degradation of dissolved organic matter (DOM) in lake ecosystems can result in rapid depletion of dissolved oxygen (DO). Inputs of terrestrial DOM including organic acids can also lead to decreases in pH. However, to date, few studies have investigated the linkages between terrestrial DOM inputs, DO and pH levels in the water column, and carbon dioxide (CO2) emissions from lake ecosystems. Based on monthly field sampling campaigns across 100 sites in Lake Qiandao, a major man-made drinking water reservoir in China, from May 2020 to April 2021, we estimated an annual CO2 efflux (FCO2) of 37.2 ± 29.0 gC m-2 yr-1, corresponding to 0.02 ± 0.02 TgC yr-1 from this lake. FCO2 increased significantly with decreasing DO, chlorophyll-a (Chl-a) and δ2H-H2O, while FCO2 increased with increasing specific UV absorbance (SUVA254) and a terrestrial humic-like component (C2). We found that DO concentration and pH declined with increasing terrestrial DOM inputs, i.e. increased SUVA254 and terrestrial humic-like C2 levels. Vertical profile sampling revealed that the partial pressure of CO2 (pCO2) increased with increasing terrestrial DOM fluorescence (FDOM), while DO, pH, and δ13C-CO2 declined with increasing terrestrial FDOM. These results highlight the importance of terrestrial DOM inputs in altering physico-chemical environments and fueling CO2 emissions from this lake and potentially other aquatic ecosystems.

Terrestrial dissolved organic matter inputs drive the temporal dynamics of riverine bacterial ecological networks and assembly processes.

Rivers receive, transport, and are reactors of terrestrial dissolved organic matter (DOM) and are highly influenced by changes in hydrological conditions and anthropogenic disturbances, but the effect of DOM composition on the dynamics of the bacterial community in rivers is poorly understood. We conducted a seasonal field sampling campaign at two eutrophic river mouth sites to examine how DOM composition influences the temporal dynamics of bacterial community networks, assembly processes, and DOM-bacteria associations. DOM composition and seasonal factors explained 34.7% of the variation in bacterial community composition, and 14.4% was explained purely by DOM composition where specific UV absorbance (SUVA254) as an indicator of aromaticity was the most important predictor. Significant correlations were observed between SUVA254 and the topological features of subnetworks of interspecies and DOM-bacteria associations, indicating that high DOM aromaticity results in more complex and connected networks of bacteria. The bipartite networks between bacterial taxa and DOM molecular formulae (identified by ultrahigh-resolution mass spectrometry) further revealed less specialized bacterial processing of DOM molecular formulae under the conditions of high water level and DOM aromaticity in summer than in winter. A shift in community assembly processes from stronger homogeneous selection in summer to higher stochasticity in winter correlated with changes in DOM composition, and more aromatic DOM was associated with greater similarity in bacterial community composition. Our results highlight the importance of DOM aromaticity as a predictor of the temporal dynamics of riverine bacterial community networks and assembly.

Dynamics and functions of biomarker taxa determine substrate-specific organic waste composting.

Bacteria are an influential component of diverse composting microbiomes, but their structure and underlying dynamics are poorly understood. This study analyzed the bacterial communities of 577 compost datasets globally and constructed a substrate-dependent catalog with more than 15 million non-redundant 16S rRNA gene sequences. Using a random-forest machine-learning model, 30 biomarker taxa were identified that accurately distinguish between the food, sludge and manure waste composting microbiomes (accuracy >98 %). These biomarker taxa were closely associated with carbon and nitrogen metabolic processes, during which they contributed to the predominant stochastic process and are influenced by different factors in the substrate-specific composts. This is corroborated by the community topological characteristics, which feature the biomarkers as keystone taxa maintaining the bacterial network stability. These findings provide a theoretical basis to identify and enhance the biomarker-functional bacteria for optimizing the composting performance of different organic wastes.

Syntrophic entanglements for propionate and acetate oxidation under thermophilic and high-ammonia conditions.

Propionate is a key intermediate in anaerobic digestion processes and often accumulates in association with perturbations, such as elevated levels of ammonia. Under such conditions, syntrophic ammonia-tolerant microorganisms play a key role in propionate degradation. Despite their importance, little is known about these syntrophic microorganisms and their cross-species interactions. Here, we present metagenomes and metatranscriptomic data for novel thermophilic and ammonia-tolerant syntrophic bacteria and the partner methanogens enriched in propionate-fed reactors. A metagenome for a novel bacterium for which we propose the provisional name 'Candidatus Thermosyntrophopropionicum ammoniitolerans' was recovered, together with mapping of its highly expressed methylmalonyl-CoA pathway for syntrophic propionate degradation. Acetate was degraded by a novel thermophilic syntrophic acetate-oxidising candidate bacterium. Electron removal associated with syntrophic propionate and acetate oxidation was mediated by the hydrogen/formate-utilising methanogens Methanoculleus sp. and Methanothermobacter sp., with the latter observed to be critical for efficient propionate degradation. Similar dependence on Methanothermobacter was not seen for acetate degradation. Expression-based analyses indicated use of both H2 and formate for electron transfer, including cross-species reciprocation with sulphuric compounds and microbial nanotube-mediated interspecies interactions. Batch cultivation demonstrated degradation rates of up to 0.16 g propionate L-1 day-1 at hydrogen partial pressure 4-30 Pa and available energy was around -20 mol-1 propionate. These observations outline the multiple syntrophic interactions required for propionate oxidation and represent a first step in increasing knowledge of acid accumulation in high-ammonia biogas production systems.

Thermodynamic restrictions determine ammonia tolerance of methanogenic pathways in Methanosarcina barkeri.

Ammonia is a ubiquitous potential inhibitor of anaerobic digestion processes, mainly exhibiting inhibition towards methanogenic activity. However, knowledge as to how ammonia affects the methanogens is still limited. In this study, we cultured a multitrophic methanogen, Methanosarcina barkeri DSM 800, with acetate, H2/CO2, and methanol to evaluate the influence of ammonia on different methanogenic pathways. Aceticlastic methanogenesis was more sensitive to increased ammonia concentrations than hydrogenotrophic and methylotrophic methanogenesis. Theoretical maximum NH3 tolerances of M. barkeri fed with acetate, H2/CO2, and methanol were calculated to be 39.1 ± 9.0, 104.3 ± 7.4, and 85.7 ± 1.0 mg/L, respectively. The order of the ΔG range of M. barkeri under three methanogenic pathways reflected the order of ammonia tolerance of M. barkeri. Our results provide insights into the role of the thermodynamic potential of methanogenesis on the tolerance of ammonia stress; and shed light on the mechanism of ammonia inhibition on anaerobic digestion.

Distribution of methanogenic and methanotrophic consortia at soil-water interfaces in rice paddies across climate zones.

Periphytic biofilms (PB) at the soil-water interface contributes 7-38% of the methane emission from rice paddies, yet the biogeographical mechanism underlying and affecting the process remain elusive. In this study, rice fields along an edapho-vclimatic gradient were sampled, and the environmental drivers affecting distribution of methanogenic and methanotrophic communities were evaluated. The methanogenic and methanotrophic communities at soil-water interface showed less complex inter/intra-generic interactions than those in soil, and their relative abundances were weakly driven by spatial distance, soil organic carbon, soil total nitrogen and pH. The nutrient supply and buffering capacity of extracellular polymeric substance released by PB reduced their interaction and enhanced the resilience on edaphic environment changes. Climate affected soil metal content, extracellular polymeric substance content, and thus the methane-related communities, and caused geographical variation in the impacts of PB on methane emissions from rice paddies. This study facilitates our understanding of geographical differences in the contribution of PB to methane emission.

Twice-milled magnetic biochar: A recyclable material for efficient removal of methylene blue from wastewater.

Although magnetic modification has potential for preparing recyclable biochar, the traditional preparation methods of loading magnetic materials on biochar will probably lead to pore blockage and consequently remarkable adsorption recession. Herein, a preparation method was developed in which ball milled biochar was loaded with ultrafine magnetite and then milled for a second time, thus generating a magnetic, recyclable biochar with minimal pore blockage. The deposits of magnetite did not significantly wrap the biochar, although a decreased sorption performance was still detectable. Benefitting from the extra milling step, surface functional groups and specific surface areas of the adsorbents were largely restored, thus leading to a 93.8 % recovery adsorption of 84.6 ± 2.5 mg/L on methylene blue. Meanwhile, the recyclability of the material was not affected. The adsorption was driven by multiple interactions. These twice-milled magnetic biochar is quite outstanding for sustainable removal of aqueous contaminants with its recyclability and high sorption efficiency.

Explaining the resistomes in a megacity's water supply catchment: Roles of microbial assembly-dominant taxa, niched environments and pathogenic bacteria.

Antibiotic resistance genes (ARGs) in drinking water sources suggest the possible presence of resistant microorganisms that jeopardize human health. However, explanations for the presence of specific ARGs in situ are largely unknown, especially how their prevalence is affected by local microbial ecology, taxa assembly and community-wide gene transfer. Here, we characterized resistomes and bacterial communities in the Taipu River catchment, which feeds a key drinking water reservoir to a global megacity, Shanghai. Overall, ARG abundances decreased significantly as the river flowed downstream towards the reservoir (P < 0.01), whereas the waterborne bacteria assembled deterministically (|ßNRI| > 2.0) as a function of temperature and dissolved oxygen conditions with the assembly-dominant taxa (e.g. Ilumatobacteraceae and Cyanobiaceae) defining local resistomes (P < 0.01, Cohen's D = 4.22). Bacterial hosts of intragenomic ARGs stayed at the same level across the catchment (60 ∼ 70 genome copies per million reads). Among them, the putative resistant pathogens (e.g. Burkholderiaceae) carried mixtures of ARGs that exhibited high transmission probability (transfer counts = 126, P < 0.001), especially with the microbial assembly-dominant taxa. These putative resistant pathogens had densities ranging form 3.0 to 4.0 × 106 cell/L, which was more pronouncedly affected by resistome and microbial assembly structures than environmental factors (SEM, std-coeff ß = 0.62 vs. 0.12). This work shows that microbial assembly and resistant pathogens play predominant roles in prevelance and dissemination of resistomes in receiving water, which deserves greater attention in devisng control strategies for reducing in-situ ARGs and resistant strains in a catchment.

Beyond the snapshot: identification of the timeless, enduring indicator microbiome informing soil fertility and crop production in alkaline soils.

BACKGROUND: Microorganisms are known to be important drivers of biogeochemical cycling in soil and hence could act as a proxy informing on soil conditions in ecosystems. Identifying microbiomes indicative for soil fertility and crop production is important for the development of the next generation of sustainable agriculture. Earlier researches based on one-time sampling have revealed various indicator microbiomes for distinct agroecosystems and agricultural practices as well as their importance in supporting sustainable productivity. However, these microbiomes were based on a mere snapshot of a dynamic microbial community which is subject to significant changes over time. Currently true indicator microbiomes based on long-term, multi-annual monitoring are not available. RESULTS: Here, using samples from a continuous 20-year field study encompassing seven fertilization strategies, we identified the indicator microbiomes ecophysiologically informing on soil fertility and crop production in the main agricultural production base in China. Among a total of 29,184 phylotypes in 588 samples, we retrieved a streamlined consortium including 2% of phylotypes that were ubiquitously present in alkaline soils while contributing up to half of the whole community; many of them were associated with carbon and nutrient cycling. Furthermore, these phylotypes formed two opposite microbiomes. One indicator microbiome dominated by Bacillus asahii, characterized by specific functional traits related to organic matter decomposition, was mainly observed in organic farming and closely associated with higher soil fertility and crop production. The counter microbiome, characterized by known nitrifiers (e.g., Nitrosospira multiformis) as well as plant pathogens (e.g., Bacillus anthracis) was observed in nutrient-deficit chemical fertilizations. Both microbiomes are expected to be valuable indictors in informing crop yield and soil fertility, regulated by agricultural management. CONCLUSIONS: Our findings based on this more than 2-decade long field study demonstrate the exciting potential of employing microorganisms and maximizing their functions in future agroecosystems. Our results report a "most-wanted" or "most-unwanted" list of microbial phylotypes that are ready candidates to guide the development of sustainable agriculture in alkaline soils.

Periphytic biofilms-mediated microbial interactions and their impact on the nitrogen cycle in rice paddies.

Rice paddies are unique waterlogged wetlands artificially constructed for agricultural production. Periphytic biofilms (PBs) at the soil-water interface play an important role in rice paddies characterized by high nutrient input but low utilization efficiency. PBs are composed of microbial aggregates, including a wide variety of microorganisms (algae, bacteria, fungi, protozoa, and metazoa), extracellular polymeric substances and minerals (iron, aluminum, and calcium), which form an integrated food web and energy flux within a relatively stable micro-ecosystem. PBs are crucial to regulate and streamline the nitrogen cycle by neutralizing nitrogen losses and improving rice production since PBs can serve as both a sink by capturing surplus nitrogen and a source by slowly re-releasing this nitrogen for reutilization. Here the ecological advantages of PBs in regulating the nitrogen cycle in rice paddies are illustrated. We summarize the key functional importance of PBs, including the intricate and delicate community structure, microbial interactions among individual phylotypes, a wide diversity of self-produced organics, the active adaptation of PBs to constantly changing environments, and the intricate mechanisms by which PBs regulate the nitrogen cycle. We also identify the future challenges of microbial interspecific cooperation in PBs and their quantitative contributions to agricultural sustainability, optimizing nitrogen utilization and crop yields in rice paddies.

Syntrophic propionate-oxidizing bacteria in methanogenic systems.

The mutual nutritional cooperation underpinning syntrophic propionate degradation provides a scant amount of energy for the microorganisms involved, so propionate degradation often acts as a bottleneck in methanogenic systems. Understanding the ecology, physiology and metabolic capacities of syntrophic propionate-oxidizing bacteria (SPOB) is of interest in both engineered and natural ecosystems, as it offers prospects to guide further development of technologies for biogas production and biomass-derived chemicals, and is important in forecasting contributions by biogenic methane emissions to climate change. SPOB are distributed across different phyla. They can exhibit broad metabolic capabilities in addition to syntrophy (e.g. fermentative, sulfidogenic and acetogenic metabolism) and demonstrate variations in interplay with cooperating partners, indicating nuances in their syntrophic lifestyle. In this review, we discuss distinctions in gene repertoire and organization for the methylmalonyl-CoA pathway, hydrogenases and formate dehydrogenases, and emerging facets of (formate/hydrogen/direct) electron transfer mechanisms. We also use information from cultivations, thermodynamic calculations and omic analyses as the basis for identifying environmental conditions governing propionate oxidation in various ecosystems. Overall, this review improves basic and applied understanding of SPOB and highlights knowledge gaps, hopefully encouraging future research and engineering on propionate metabolism in biotechnological processes.

A novel biotechnology based on periphytic biofilms with N-acyl-homoserine-lactones stimulation and lanthanum loading for phosphorus recovery.

This study presents an approach for developing periphytic biofilm with N-acyl-homoserine-lactones (AHLs) stimulation and lanthanum (La, a rare earth element) loading, to achieve highly efficient and stable phosphorus (P) recovery from wastewater. AHLs stimulated biofilm growth and formation, also improved stable P entrapment by enhancing extracellular polymeric substance (EPS) production and optimizing P-entrapment bacterial communities. Periphytic biofilms loading La is based on ligand exchanges, and La loading achieved initial rapid P entrapment by surface adsorption. The combination of AHLs stimulation and La loading achieved 99.0% P entrapment. Interestingly, the enhanced EPS production stimulated by AHLs protected biofilms against La. Moreover, a method for P and La separately recovery from biofilms was developed, achieving 89-96% of P and 88-93% of La recovery. This study offers a promising biotechnology to reuse La from La-rich wastewater and recover P by biofilm doped with La, which results in a win-win situation for resource sustainability.

Contribution of periphytic biofilm of paddy soils to carbon dioxide fixation and methane emissions.

Rice paddies are major contributors to anthropogenic greenhouse gas emissions via methane (CH4) flux. The accurate quantification of CH4 emissions from rice paddies remains problematic, in part due to uncertainties and omissions in the contribution of microbial aggregates on the soil surface to carbon fluxes. Herein, we comprehensively evaluated the contribution of one form of microbial aggregates, periphytic biofilm (PB), to carbon dioxide (CO2) and CH4 emissions from paddies distributed across three climatic zones, and quantified the pathways that drive net CH4 production as well as CO2 fixation. We found that PB accounted for 7.1%-38.5% of CH4 emissions and 7.2%-12.7% of CO2 fixation in the rice paddies. During their growth phase, PB fixed CO2 and increased the redox potential, which promoted aerobic CH4 oxidation. During the decay phase, PB degradation reduced redox potential and increased soil organic carbon availability, which promoted methanogenic microbial community growth and metabolism and increased CH4 emissions. Overall, PB acted as a biotic converter of atmospheric CO2 to CH4, and aggravated carbon emissions by up to 2,318 kg CO2 equiv ha-1 season-1. Our results provide proof-of-concept evidence for the discrimination of the contributions of surface microbial aggregates (i.e., PB) from soil microbes, and a profound foundation for the estimation and simulation of carbon fluxes in a potential novel approach to the mitigation of CH4 emissions by manipulating PB growth.

Geographic imprint and ecological functions of the abiotic component of periphytic biofilms.

We revealed abiotic components (extracellular polymeric substances, EPSs) in the periphytic biofilms. Further, the effect of the microbial community on the EPS, and the geodistribution patterns and ecological functions of the EPS were studied.

Importance of thermodynamics dependent kinetic parameters in nitrate-based souring mitigation studies.

Souring is the unwanted formation of hydrogen sulfide (H2S) by sulfate-reducing microorganisms (SRM) in sewer systems and seawater flooded oil reservoirs. Nitrate treatment (NT) is one of the major methods to alleviate souring: The mechanism of souring remediation by NT is stimulation of nitrate reducing microorganisms (NRM) that depending on the nitrate reduction pathway can outcompete SRM for common electron donors, or oxidize sulfide to sulfate. However, some nitrate reduction pathways may challenge the efficacy of NT. Therefore, a precise understanding of souring rate, nitrate reduction rate and pathways is crucial for efficient souring management. Here, we investigate the necessity of incorporating two thermodynamic dependent kinetic parameters, namely, the growth yield (Y), and FT, a parameter related to the minimum catabolic energy production required by cells to utilize a given catabolic reaction. We first show that depending on physiochemical conditions, Y and FT for SRM change significantly in the range of [0-0.4] mole biomass per mole electron donor and [0.0006-0.5], respectively, suggesting that these parameters should not be considered constant and that it is important to couple souring models with thermodynamic models. Then, we highlight this further by showing an experimental dataset that can be modeled very well by considering variable FT. Next, we show that nitrate based lithotrophic sulfide oxidation to sulfate (lNRM3) is the dominant nitrate reduction pathway. Then, arguing that thermodynamics would suggest that S° consumption should proceed faster than S0 production, we infer that the reason for frequently observed S0 accumulation is its low solubility. Last, we suggest that nitrate based souring treatment will suffer less from S0 accumulation if we (i) act early, (ii) increase temperature and (iii) supplement stoichiometrically sufficient nitrate.

Soil Organic Carbon Enrichment Triggers In Situ Nitrogen Interception by Phototrophic Biofilms at the Soil-Water Interface: From Regional Scale to Microscale.

Phototrophic biofilms are easy to grow at sediment/soil-water interfaces (SWIs) in shallow aquatic ecosystems and greatly impact nutrient biogeochemical cycles. However, the pathways by which they contribute to nitrogen interception and interact with sediment/soil remains largely unknown. Here, we conducted a field investigation in paddy fields in various regions of China and found that nitrogen immobilized in biofilm biomass significantly positively correlated with soil organic carbon (SOC) content. A microcosm experiment showed that this was due to increased bacterial and algal diversity, biomass accumulation, and inorganic nitrogen assimilation at high SOC, especially high dissolved organic carbon (DOC) levels. The metatranscriptomics results further verified that many KO groups of PSII, PSI, AP, and PC in antenna proteins and glutamate synthesis were distinctly expressed at elevated SOC and DOC levels. Our results elucidated the effects and possible pathways of how SOC enrichment triggers photosynthesis and nitrogen immobilization by phototrophic biofilms. The results will provide meaningful information for in situ nitrogen interception by using phototrophic biofilms at the SWI in human-made wetlands to change internal nitrogen cycling.

N-acyl-homoserine-lactones signaling as a critical control point for phosphorus entrapment by multi-species microbial aggregates.

Quorum sensing (QS) has been extensively studied in pure stains of microorganisms, but the ecological roles of QS in multi-species microbial aggregates are poorly understood due to the aggregates' heterogeneity and complexity, in particular the phosphorus (P) entrapment, a key aspect of element cycling. Using periphytic biofilm as a microbial-aggregate model, we addressed how QS signaling via N-acyl-homoserine-lactones (AHLs) regulated P entrapment. The most-abundant AHLs detected were C8-HSL, 3OC8-HSL, and C12-HSL, are the primary regulator of P entrapment in the periphytic biofilm. QS signaling-AHL is a beneficial molecule for bacterial growth in periphytic biofilm and the addition of these three AHLs optimized polyphosphate accumulating organisms (PAOs) community. Growth promotion was accompanied by up-regulation of pyrimidine, purine and energy metabolism. Both intra- and extra-cellular P entrapment were enhanced in the addition of AHLs. AHLs increased extracellular polymeric substances (EPS) production to drive extracellular P entrapment, via up-regulating amino acids biosynthesis and amino sugar/nucleotide sugar metabolism. Also, AHLs improved intracellular P entrapment potential by regulating genes involved in inorganic-P accumulation (ppk, ppx) and P uptake and transport (pit, pstSCAB). This proof-of-concept evidence about how QS signaling regulates P entrapment by microbial aggregates paves the way for managing QS to enhance P removal by microbial aggregates in aquatic environments.

Experimental and Genomic Evaluation of the Oestrogen Degrading Bacterium Rhodococcus equi ATCC13557.

Rhodococcus equi ATCC13557 was selected as a model organism to study oestrogen degradation based on its previous ability to degrade 17α-ethinylestradiol (EE2). Biodegradation experiments revealed that R. equi ATCC13557 was unable to metabolise EE2. However, it was able to metabolise E2 with the major metabolite being E1 with no further degradation of E1. However, the conversion of E2 into E1 was incomplete, with 11.2 and 50.6% of E2 degraded in mixed (E1-E2-EE2) and E2-only conditions, respectively. Therefore, the metabolic pathway of E2 degradation by R. equi ATCC13557 may have two possible pathways. The genome of R. equi ATCC13557 was sequenced, assembled, and mapped for the first time. The genome analysis allowed the identification of genes possibly responsible for the observed biodegradation characteristics of R. equi ATCC13557. Several genes within R. equi ATCC13557 are similar, but not identical in sequence, to those identified within the genomes of other oestrogen degrading bacteria, including Pseudomonas putida strain SJTE-1 and Sphingomonas strain KC8. Homologous gene sequences coding for enzymes potentially involved in oestrogen degradation, most commonly a cytochrome P450 monooxygenase (oecB), extradiol dioxygenase (oecC), and 17ß-hydroxysteroid dehydrogenase (oecA), were identified within the genome of R. equi ATCC13557. These searches also revealed a gene cluster potentially coding for enzymes involved in steroid/oestrogen degradation; 3-carboxyethylcatechol 2,3-dioxygenase, 2-hydroxymuconic semialdehyde hydrolase, 3-alpha-(or 20-beta)-hydroxysteroid dehydrogenase, 3-(3-hydroxy-phenyl)propionate hydroxylase, cytochrome P450 monooxygenase, and 3-oxosteroid 1-dehydrogenase. Further, the searches revealed steroid hormone metabolism gene clusters from the 9, 10-seco pathway, therefore R. equi ATCC13557 also has the potential to metabolise other steroid hormones such as cholesterol.