Improving N2 fixation from the plant down: Compatibility of Trifolium subterraneum L. cultivars with soil rhizobia can influence symbiotic performance

Plant genotypes of Trifolium subterraneum L. (subterranean clover) were evaluated for differences in symbiotic N₂ fixation with soil rhizobia, with the long-term aim of using plant selection to overcome sub-optimal N₂ fixation associated with poorly effective soil rhizobia. Symbiotic performance (SP) was assessed for 49 genotypes of subterranean clover with each of four pure Rhizobium strains isolated from soil. Plants were grown in N free media in the greenhouse and their shoot dry weights measured and expressed as a percentage of dry weight with R. leguminosarm bv. trifolii WSM1325, the recommended commercial inoculant. Average SP with two Rhizobium strains (H and J) ranged from completely ineffective to 80% of potential for the subterranean clover genotypes. Two clover cultivars with high (cv. Campeda) and low (cv. Clare) SP values were investigated in more detail. Campeda typically fixed more N₂ than Clare when inoculated with 30 soil extracts (4.2 vs 2.4 mg N₂ fixed/shoot) and with 14 pure strains isolated from those soils (4.2 vs 2.2 mg N₂ fixed/shoot). The poor performance of Clare could be attributed to interruptions at multiple stages of the symbiotic association, from nodule initiation (less nodules), nodule development (small, white nodules), through to reduced nodule function (N₂ fixed/mg nodule) depending on the inoculation treatment. Through the careful use of subterranean clover genotypes by plant breeders it should be possible to make significant gains in the SP of future subterranean clover cultivars.     

Symbiotic effectiveness of strains of Rhizobium leguminosarum biovar phaseoli isolated from soils of Rwanda

We have isolated 48 strains of Rhizobium leguminosarum biovar phaseoli from nodules of Phaseolus vulgaris L. cultivated on 32 different soils at 22 various locations in Rwanda, Central Africa. The symbiotic effectiveness of the strains was appraised in the greenhouse by measuring shoots dry matter and total plant nitrogen content after six weeks of growth. Of the strains tested 19%, 58% and 23% were rated very effective, effective and ineffective, respectively. A very significant correlation (r=0.96, P<0.01) was observed between shoots dry matter and total N content. By using the total nitrogen balance method, it was estimated that in the presence of a very effective strain, up to 86% of the N present in the shoots comes from N₂ fixation. No significant correlations were observed between the symbiotic effectiveness of the strains and the pH of the soils from which they originated, the tolerance of the strains to acidity or their ability to produce organic acids. The nine very effective strains selected were highly competitive against two ineffective strains with the two P. vulgaris cultivars Rubona-5 and Kiryumukwe.Contribution no 367, Station de recherches, Agriculture Canada.Contribution no 367, Station de recherches, Agriculture Canada.     

Preliminary characterization of an ineffective Frankia derived from a spontaneously neomycin-resistant strain

Five strains of Frankia isolated from actinorhizae of 3 alder species were cultivated with various concentrations of neomycin in the medium. For one strain, resistance to neomycin was associated with lost of effectiveness. The ineffective strain was as infective as the parent strain. Protein and isoenzymes patterns showed that the ineffective and the parent strains were quite similar. The ineffective strain differentiated vesicles inside the infected host-cells.     

Gene centres,a source for genetic variants in symbiotic nitrogen fixation: The symbiotic response of the cultivated pea toRhizobium leguminosarum strains from Europe and the Middle East

Summary Soil samples from several European countries; Sweden, the Netherlands, Spain, Italy and Greece, contained rhizobial populations capable of forming an effective symbiosis with the cultivated pea cv. Rondo from the Netherlands. The range of variation among the European Rhizobium strains, as expressed on pea cv. Rondo, was not so large and almost the same variation could be found within the rhizobial population within each country. Superior Rhizobium strains for the Dutch pea were not restricted to soils from the Netherlands but were also found in those from Sweden and Italy.Soils from Turkey and Israel also contained Rhizobium strains capable of nodulating pea cv. Rondo. However, the genetic variation among these Middle East Rhizobium strains was much larger than that of the European strains. When tested on pea cv. Rondo the majority of the Middle East strains belonged to the medium or low effective classes and only a few strains were comparable with European Rhizobium strains.Dutch Rhizobium strains induced effective nodules on both the Dutch pea cv. Rondo and the Swedish cv. L 110. However, in association with a Turkish Rhizobium strain effective nodules were formed on pea cv. Rondo and ineffective nodules on cv. L 110.We suggest that the genetic uniformity of EuropeanR. leguminosarum strains is the result of selection and domestication of Rhizobium strains originally derived from the gene centres of the pea plant.     

Evaluation of the symbiotic nitrogen-fixing potential of soils by direct microbiological means

A method for estimating the nitrogen-fixing capacity of a population of rhizobia resident in soil is presented. legume test plants, growing under microbiologically-controlled conditions in test tubes packed with a vermiculite substrate moistened with a nitrogen-free plant nutrient solution, are inoculated directly with a suspension of the soil under examination. Rhizobia in the soil nodulate the test plants, and the amount of foliage dry matter produced in the 28 days after inoculation is regarded as an index of their effectiveness. An inoculum of at least 30, and preferably 100, rhizobia is needed to ensure that nitrogen fixation is not masked by delayed nodulation. The new method is tentatively described as the ‘whole-soil inoculation’ technique. Appraisals were made withTrifolium subterraneum L. andRhizobium trifolii and withMedicago sativa L. andR. meliloti. Soil-borne pathogens did not interfere with plant growth. The whole-soil inoculation technique was less tedious and time-consuming than an alternative method which involved extracting representative isolates from the soil and testing their effectiveness individually, and appeared to give more realistic values for the nitrogen-fixing capacity of the soil as a whole. Used in association with a field experiment, the whole-soil inoculation technique confirmed microbiologically that there had been an agronomic response to surface application of inoculant to poorly-nodulatedT. subterraneum pasture. It is submitted that this technique for determining the effectiveness of rhizobia in soil, combined with a plant-infection method for counting rhizobia, can be a reliable guide to the need for inoculation in the field.     

Plant growth and nutrient uptake characteristics of Fe-deficiency chlorosis susceptible and resistant subclovers

The objective of this study was to evaluate the growth and nutrient-uptake characteristics of Fe-deficiency resistant and susceptible subclover (Trifolium subterraneum L., T. yanninicum Katzn. and Morley, T. brachcalycinum Katzn. and Morley) cultivars on a calcareous soil. Ten subclover cultivars showing varying susceptibilities to Fe-deficiency chlorosis (Karridale, Nangeela, Geraldton, Mt. Barker, Woogenellup, Larisa, Trikkala, Rosedale, Koala and Clare) were grown on a low-Fe, calcareous soil (Petrocalcic Paleustoll) under moist (18% water content, 85% of water holding capacity) and water-saturated conditions using a Cone-tainer^® culture system. Chlorosis and its correlation with growth traits and mineral nutrition of the 10 cultivars were examined. The Fe-deficiency susceptibilities of the 10 cultivars decreased in the above order under the moist condition, but in slightly different order under the saturated condition. Shoot and root dry weights, total dry weight, and root-to-shoot ratio were each negatively correlated with chlorosis under both soil-moisture conditions, as was total shoot content of P, Ca, Fe, Mn and Zn. Shoot P and Fe concentrations were each positively correlated with chlorosis under the moist soil condition. Iron and Cu utilization efficiencies (biomass per unit weight of nutrient) in the shoot were each negatively correlated with chlorosis under the moist soil condition. These results suggest that there may be several characteristics of Fe-deficiency chlorosis resistance in subclovers, such as a more effective soil-Fe mobilizing mechanism(s), more balanced nutrition, lower required Fe concentration in the shoot, higher shoot-Fe utilization efficiency, and higher root/shoot ratio under Fe-deficiency stress conditions.     

两种栽培型广藿香内生真菌群落组成变化

为探索内生真菌与广藿香互作间对宿主活性成分形成机制的影响,该研究以成分差异较大的牌香和湛香为对象,采用传统形态学方法对所获菌株归类,通过真菌通用引物ITS1/ITS4扩增菌株rDNA-ITS序列,鉴定其分类地位并研究其多样性。结果表明：(1)用PDA和LBA培养基对苗期、分枝期和成株期广藿香茎叶组织块进行内生真菌分离,共获得3 070株菌株,其中牌香(PX)分离出1 624株,鉴定出1 319株,分属于36属;湛香(ZX)分离出1 446株,鉴定出994株,分属于33属。牌香分离出7种特有内生真菌,分别为香柱菌(Epichloe typhina)、盘长孢状刺盘孢菌(Colletotrichum gloeosporioides)、座腔孢菌(Botryosphaeria sp.)、丝核菌(Rhizoctonia sp.)及截盘多毛孢菌(Truncatella sp.),并首次分离到疫霉菌(Phytophthora sp.)和指疫霉菌(Sclerophthora sp.),这2种菌属于卵菌门内生菌。湛香分离出拟青霉菌(Paecilomyces sp.)和尾孢菌(Cercospora sp.)...     

nodT,a positively-acting cultivar specificity determinant controlling nodulation of Trifolium subterraneum by Rhizobium leguminosarum biovar trifolii

Rhizobium leguminosarum biovar trifolii strain TA1 nodulates a range of Trifolium plants including red, white and subterranean clovers. Nitrogen-fixing nodules are promptly initiated on the tap roots of these plants at the site of inoculation. In contrast to these associations, strain TA1 has a Nod^- phenotype on a particular cultivar of subterranean clover called Woogenellup (A.H. Gibson, Aust J Agric Sci 19: (1968) 907–918) where it induces rare, poorly developed, slow-to-appear and ineffective lateral root nodules. By comparing the nodulation gene region of strain TA1 with that of another R. leguminosarum bv. trifolii strain ANU843, which is capable of efficiently nodulating cv. Woogenellup, we have shown that the nodT gene (B.P. Surin et al., Mol Microbiol 4: (1990) 245–252) is essential for nodulation on cv. Woogenellup. The nodT gene is naturally absent in strain TA1. A cosmid clone spanning the entire nodulation gene region of strain TA1 was capable of conferring nodulation ability to R.l. bv. trifolii strains deleted for nodulation genes, but only on cultivars of subterranean clovers nodulated by strain TA1. This shows that cultivar recognition events are, in part, determined by genes in the nodulation region of strain TA1. Complementation studies also indicated that strain TA1 contains negatively-acting genes located on the Sym plasmid and elsewhere, which specifically block nodulation of cv. Woogenellup.     

Nodulation ofTrifolium subterraneum byRhizobium leguminosarum

Summary Four cultivars ofTrifolium subterraneum were nodulated by five strains ofRhizobium leguminosarum; all combinations except one gave 100% nodulation. Rates of nodule formation and total nodule numbers were similar to those with an effectiveR. trifolii strain. The nodules were more commonly associated with lateral roots and were ineffective in nitrogen fixation.     

Effects of leguminous ground cover competition on red birch and soil nutrient status in the nursery

Legumes as ground cover are regularly planted to increase nitrogen economy of crops and to improve soil. In the present study various clover species were evaluated as vegetative ground cover in nursery field production of micropropagated red birch (Betula pubescensEhrh. f. rubraUlvinen f. nova) in two 2-year experiments. The clover species and cultivars, Trifolium pratenseL. ‘Bjursele’, T. repens L. ‘Jogeva’, T. repens L. ‘Sonja’, T. hybridum L. ‘Frida’, T. incarnatum L. ‘Opolska’, T. resupinatum L. and T. subterraneum L. were compared to grass sod Festuca rubra L. ‘Ensylva’ and to a coverless ground (control). The last one was kept weed free by hand hoeing. Birch (leaves, stems, branches and roots) and soil nutrient concentrations (N, P, K, Ca, Mg and Fe) were analysed and nutrient ratios in birch determined. The annual clovers, T. incarnatumL., T. resupinatumL. and T. subterraneumL., provided about the same nutrient status in birch as did the control. Perennial clovers and grass were strong competitors with trees. High levels of P and Mg in birch leaves relative to N concentration were typical for poorly growing seedlings. Neither annual nor perennial clovers did generally improve soil nutrient status. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mycolytic effect of extracellular enzymes of antagonistic microbes to Colletotrichum falcatum,red rot pathogen of sugarcane

Strains of selected bacteria and Trichoderma harzianum isolated from sugarcane rhizosphere and endosphere regions were tested for the production of chitinolytic enzymes and their involvement in the suppression of Colletotrichum falcatum, red rot pathogen of sugarcane. Among several strains tested for chitinolytic activity, 12 strains showed a clearing zone on chitin-amended agar medium. Among these, bacterial strains AFG2, AFG 4, AFG 10, FP7 and VPT4 and all the tested T. harzianum strains produced clearing zones of a size larger than 10 mm. The antifungal activity of these strains increased when chitin was incorporated into the medium. Trichoderma harzianum strain T5 showed increased levels of activity of N-acetylglucosaminidase and -1,3-glucanase when grown on minimal medium containing chitin or cell wall of the pathogen. Lytic enzymes of bacterial strains AFG2, AFG4, VPT4 and FP7 and T. harzianum T5 inhibited conidial germination and mycelial growth of the pathogen. Enzymes from T. harzianum T5 were found to be the most effective in inhibiting the fungus. When mycelial discs of the pathogen were treated with the enzymes, electrolytes were released from fungal mycelia. The results indicated that antagonistic T. harzianum T5 caused a higher level of lysis of the pathogen mycelium, and the inhibitory effect was more pronounced when the lytic enzymes were produced using chitin or cell wall of the pathogen as carbon source.     

In vitro antagonism of Thielaviopsis paradoxa by Trichoderma longibrachiatum

Seventy-nine Trichoderma strains were isolated from soil taken from 28 commercial plantations of Agave tequilana cv. ‘Azul’ in the State of Jalisco, Mexico. Nine of these isolates produced nonvolatile metabolites that completely inhibited the growth of Thielaviopsis paradoxa on potato dextrose agar plates. These isolates were identified as Trichoderma longibrachiatum on the basis of their morphology and DNA sequence analysis of two genes (ITS rDNA and translation elongation factor EF-1α). Mycoparasitism of Th. paradoxa by T. longibrachiatum strains in dual cultures was examined by scanning electron microscopy. The Trichoderma hyphae grew alongside the Th. paradoxa hyphae, but penetration of Thielaviopsis hyphae by Trichoderma was no apparent. Aleurioconidia of Th. paradoxa were parasitized by Trichoderma. Both hyphae and aleurioconidia of Th. paradoxa lost turgor pressure, wrinkled, collapsed and finally disintegrated. In liquid cultures, all nine Trichoderma isolates produced proteases, β-1,3-glucanases and chitinases that would be responsible for the degradation of Thielaviopsis hyphae. These results demonstrate that the modes of action of T. longibrachiatum involved against Th. paradoxa in vitro experiments are mycoparasitism and the production of nonvolatile toxic metabolites.     

Isolation of Beauveria bassiana and Metarhizium anisopliae var. anisopliae from Boophilus microplus tick (Canestrini, 1887), in Rio de Janeiro State,Brazil

The objective of this work were to isolate and identify strains of entomopathogenic fungi from ingurgitated female Boophilus microplus ticks, collected from the soil in the municipality of Paracambi, Rio de Janeiro State, Brazil. The ingurgitated females were inoculated in the selective medium oat dodine agar (oda), where 49 colonies of Beauveria bassiana (71%) and 20 of Metarhizium anisopliae var. anisopliae (29%) were isolated. These isolated strains characterize for the first time in Brazil the natural occurrence of these species of fungi in this tick, and will be used to conduct bioassays to evaluate the pathogenicity and virulence of these strains for ticks of the genus Boophilus microplus. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genetic diversity of <Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis> associated with alfalfa in Chilean volcanic soils and their symbiotic effectiveness under acidic conditions

A study was conducted with the aim of evaluating the genetic diversity of alfalfa rhizobia isolated from volcanic soils in southern Chile and their ability to establish an effective symbiosis with alfalfa. Rhizobial strains isolated from nodules were identified and selected based on PCR analyses and acid tolerance. Symbiotic effectiveness (nodulation and shoot dry weight) of acid-tolerant rhizobia was evaluated in glasshouse experiments under acidic conditions. The results revealed that Sinorhizobium meliloti is the dominant species in alfalfa nodules with a high genetic diversity at strain level grouped in three major clusters. There was a close relationship (r ² = 0.895, P ≤ 0.001, n = 40) between soil pH and the size of rhizobial populations. Representative isolates from major cluster groups showed wide variation in acid tolerance expressed on buffered agar plates (pH 4.5–7.0) and symbiotic effectiveness with alfalfa. One isolate (NS11) appears to be suitable as an inoculant for alfalfa according to its acid tolerance and symbiotic effectiveness at low pH (5.5). The isolation and selection of naturalized S. meliloti strains with high symbiotic effectiveness under acidic conditions is an alternative approach to improving the productivity of alfalfa and for reducing the application of synthetic fertilizers in Chile.     

3种水稻土中7株固氮蓝细菌的分离与特征

【背景】蓝细菌是水生和陆地生态系统中生物固氮的主要贡献者。【目的】增加对稻田土壤固氮蓝细菌的了解,获得用于进一步研究的可培养固氮蓝细菌菌株。【方法】选择3种具有不同固氮能力的水稻土,采用BG11-N培养基分离培养固氮蓝细菌菌株,对新分离菌株进行形态特征观察,通过基因组DNA的nifH基因扩增明确其固氮潜力,进一步采用乙炔还原法和~(15)N_2示踪法定量测定其固氮能力,通过基因组DNA的16SrRNA基因序列比对进行鉴定。【结果】在光照培养条件下,采用BG11-N培养基共分离纯化得到自养菌株7株,细胞呈圆形或椭圆形、单列、无分枝、丝状和念珠状,在固体培养基上形成团垫状菌落。新分离菌株在BG11-N培养基中生长状况良好,以基因组DNA为模板可扩增出nifH基因,乙炔还原法和~(15)N_2示踪法测定结果显示具有较高固氮能力,同时具有铁载体生成能力。结合16S rRNA基因序列比对和形态特征,7株菌被初步鉴定隶属于念珠藻科(Nostocaceae)。【结论】从水稻土中分离到在稻田生物固氮中发挥重要作用的蓝细菌(念珠藻科)菌株,可培养固氮蓝细菌菌株固氮能力较高,兼具铁载体生成能力,可作为进一步深入研究的微生物资源,具有潜在的研究应用价值。     

Utilization of phosphorus by pasture plants supplied with myo-inositol hexaphosphate is enhanced by the presence of soil micro-organisms

A range of pasture grass (Danthonia richardsonii and Phalaris aquatica) and legume (Medicago polymorpha, M. sativa, Trifolium repens and T. subterraneum) species showed limited capacity to obtain phosphorus (P) from inositol hexaphosphate (IHP), when grown in either sterile agar (pH 5.0 or 5.5) or sand-vermiculite media (pH 5.0). The total P content of shoots from IHP-supplied plants grown in agar was between 20% and 34% of that for seedlings supplied with an equivalent amount of P as inorganic phosphate (P_i), while in sand-vermiculite, the total P content of IHP-grown plants was between 5 and 10% of control plants. The poor ability of plants to utilize P from IHP resulted in significantly lower tissue P concentrations and, in general, reduced plant dry weight accumulation. In contrast, the P nutrition of plants supplied with IHP was significantly improved by inoculating media with either a cultured population of total soil micro-organisms or with a specific isolate of Pseudomonas sp., selected for its ability to release phosphate from IHP (strain CCAR59; Richardson and Hadobas, 1997 Can. J. Micro. 43, 509-516). In agar and sand-vermiculite media, respectively, the P content of IHP-grown plants increased with inoculation by up to 3.9- and 6.8-fold, such that the dry weight and P content of the plant material were equivalent to those observed for control plants supplied with P_i. However, the response to inoculation was dependent on the growth medium and the source of micro-organisms used. In sand-vermiculite, the cultured population of soil micro-organisms was effective when IHP was supplied at an equivalent level of P_i required for maximum plant growth. By comparison, inoculation of plants with the Pseudomonas strain was only effective at very high levels of IHP supply (×36), whereas in agar a response to inoculation occurred at all levels of IHP. The ability of pasture plants to acquire P from phytate was, therefore, influenced by the availability of IHP substrate, which was further affected by the presence of soil micro-organisms. Our results show that in addition to having an effect on the sorption characteristics of the growth media, soil micro-organisms also provided a source of phytase for the dephosphorylation of phytate for subsequent utilization of P_i by plants.     

Herbicide effects on the growth and nodulation potential ofRhizobium trifolii withTrifolium subterraneum L.

A study was made of the effect of the herbicides 2,4-D, amitrole, atrazine, chlorsulfuron, diclofop-methyl, diquat, glyphosate, paraquat and trifluralin on the nodulation of sub-clover (Trifolium subterraneum L. ‘Clare’), the growth ofR. trifolii TA1 in liquid nutrient medium and the ability of herbicide-treated inoculum to successfully nodulate sub-clover plants. As concentrations of amitrole, diclofop-methyl and glyphosate in the rooting environment increased from 0 to 20 mg ai L⁻¹, nodulation decreased linearly. The other herbicides at these concentrations caused more severe decreases in nodulation. Growth ofR. trifolii TA1 in nutrient broth was significantly retarded by all concentrations of diquat, 2 mg ai L⁻¹ of paraquat, 10 mg ai L⁻¹ of glyphosate and 2 mg ai L⁻¹ of chlorsulfuron. Other herbicides did not suppress rhizobial growth. Inoculation with TA1 that had been grown in the presence of amitrole, atrazine or glyphosate and then washed free of the herbicide decreased nodulation of sub-clover, indicating that these herbicides may physiologically influence the nodulating potential of certain strains of Rhizobium. The remaining herbicides showed no indications of this effect.     

Antimutagenic activity of Lactobacillus plantarum KLAB21 isolated from kimchi Korean fermented vegetables

Antimutagenic activity of Lactobacillus plantarum KLAB21, isolated from Korean kimchi, was investigated against MNNG (N-methyl-N-nitro-N-nitrosoguanidine), NQO (4-nitroquinoline-1-oxide), NPD (4-nitro-O-phenylenediamine) and aflatoxin B1 using Salmonella typhimurium strains TA100 and TA98. Although all the cell fractions including the culture supernatant, dry cells and cell-free extract exhibited antimutagenic activity against MNNG and NQO, the culture supernatant possessed the highest activity. The antimutagenic ratio of the culture supernatant was 98.4% against MNNG on strain TA100 and 57.3% against NQO on strain TA98. Its antimutagenic activity was reconfirmed by a Bacillus subtilis spore-rec assay. Levels of the antimutagenic ratios of other lactic acid bacteria originating from fermented milk ranged between 26.8 to 53% against MNNG and 28.5 to 43.4% against NQO. The antimutagenic activities of the strain KLAB21 against NPD were 72.6% on TA100 and 62.8% on TA98, and those against aflatoxin B1 were 82.5% on TA100 and 78.2% on TA98.     

Studies of two Frankia strains isolated from Trevoa trinervis Miers

The Frankia strains TtI 11 and TtI 12 isolated from T. trinervis Miers were characterized regarding their carbon source utilization, intrinsic antibiotic resistance, infectivity, and effectivity on the original host. Both strains grew on BAP medium supplemented with glucose, maltose, and sucrose, but differed in their ability to use other carbon sources such as propionate, pyruvate, acetate, succinate, citrate, and mannitol. The isolates were sensitive to five of the twelve antibiotics tested at 1 μg mL⁻¹ concentration: chloramphenicol, tobramycin, eritromycin, streptomycin, and rifampicin. They exhibited a variable degree of resistance at 1 μg mL⁻¹ concentraction to penicillin G, 4-fluorouracil, oleandomycin, and lincomycin. Both isolates were able to infect and nodulate the original host plant, and thus represent the first reported infective and effective microsymbionts for T. trinervis Miers, a rhamnaceous actinorhizal host. R O D Dixon Section editor     

Isolation of the Acrylamide Denitrifying Bacteria from a Wastewater Treatment System Manufactured with Polyacrylonitrile Fiber

Acrylamide has carcinogenicity and toxicity, so its discharge to natural water and soil systems might have an adverse impact on water quality, endangering public health and welfare. The investigation attempts to isolate acrylamide denitrifying bacteria from a wastewater treatment system manufactured with polyacrylonitrile (PAN) fiber. The goal is to elucidate the effectiveness of isolated pure strain and PAN mixed strains in treating acrylamide from synthetic wastewater. The results reveal that Ralstonia eutropha TDM-3 was isolated from the wastewater treatment system manufactured with PAN fiber. The PAN mixed strains and R. eutropha TDM-3 can consume up to 1446 mg/L acrylamide to denitrify from synthetic wastewater. Complete acrylamide removal depended on the supply of sufficient electron acceptors (nitrate). Strain R. eutropha TDM-3, Azoarcus sp. pF6, Azoarcus sp. T, and Herbaspirillum sp. G8A1 are related closely, according to the phylogenetic analyses of 16S rDNA sequences.