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Rahnella aquatilis, a nitrogen-fixing enteric bacterium associated with the rhizosphere of wheat and maize

Canadian Science Publishing
Canadian Journal of Microbiology
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Abstract

In a study of dominant diazotrophic bacteria present in the rhizosphere of wheat and maize, 28 strains of Enterobacteriaceae were isolated. They were all Voges-Proskauer positive, motile at 28 °C but not at 37 °C, and they produced a Tween-80 esterase and did not exhibit decarboxylase activity. This fits well with the description of Rahnella aquatilis. The ability of these strains to reduce acetylene in pure culture and in association with their host plant and the DNA hybridization with a nifHDK probe are described. This is the first time that R. aquatilis is reported as a rhizosphere-associated bacterium and also a nitrogen fixer. Key words: Rahnella aquatilis, rhizosphere, wheat, maize, nitrogen fixation.
... Rahnella aquatilis was first studied and described in 1976 by the Pasteur Institute. Rahnella belongs to the Yersiniaceae family and is a Gram-negative, rod-shaped, fast-moving microaerophilic bacterium that is common in various environments (Adeolu, 1998), i.e. in soil, plant phyllosphere, water and food (Berge et al., 1991;Rhodes et al., 1998). There are currently 6 species of bacteria belonging to the Rahnella genus, namely R. aquatilis, R. variigena, R. inusitata, R. bruchi, R. woolbedingensis and R. victoriana. ...
... Of them, isolates UT3, UT4 and UT9 showed high acetylene-reducing activity (79-91 nmol C 2 H 4 /flacon/24h). Berge et al. (1991) reported the R. aquatilis CF1, CF3, CF4, TR01, TR02, and TR03 rhizospheric strains exerted acetylene reductase activity measuring 60-306 nmol С 2 Н 4 /tube (Berge et al., 1991). It should be noted that those strains of rhizobacteria also showed growth on the Ashby's nitrogen-free nutrient medium, which means that their nitrogen-fixing properties have been confirmed once again. ...
... Of them, isolates UT3, UT4 and UT9 showed high acetylene-reducing activity (79-91 nmol C 2 H 4 /flacon/24h). Berge et al. (1991) reported the R. aquatilis CF1, CF3, CF4, TR01, TR02, and TR03 rhizospheric strains exerted acetylene reductase activity measuring 60-306 nmol С 2 Н 4 /tube (Berge et al., 1991). It should be noted that those strains of rhizobacteria also showed growth on the Ashby's nitrogen-free nutrient medium, which means that their nitrogen-fixing properties have been confirmed once again. ...
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As the number of people on earth increases, so does the need for food. Providing the population with environmentally friendly agricultural food is one of the urgent problems of our time. Currently, the main direction of modern organic farming is the use of biofertilizers. Bacterial preparations are capable of influencing the physiological processes of plants in small quantities, leading to increase in plant productivity. The objective of this work was studying rhizobac-teria associated with wheat roots. For this purpose, more than 100 isolates of rhizobacteria from the rhizosphere and root surface of wheat plants grown in irrigated fields of Tashkent, Syrdarya, Andijan, Kashkadarya regions. Rhizobac-teria were grown on nutrient media of Döbereiner, Ashby, Pikovsky, and Zack, and 25 isolates of associative rhizobac-teria were selected based on the characteristics of absorption of molecular nitrogen, mobilization of phosphorus and potassium. They actively dissolved Сa 3 (PO 4) 2 and KAlSiO 4 for 3 days. They were found to produce organic acids. In organic farming, nitrogen-fixing, phosphorus-and potassium-mobilizing rhizobacteria are of great practical importance , while our experiments on obtaining biological products are considered as an environmentally friendly and cost-effective way to increase crop yields. From the surface of wheat roots grown in different zones of Uzbekistan, when screening for nitrogen fixation, we selected 3 isolates with acetylene reductase activity of 79-91 nmol C 2 H 4 /flacon/24h. We determined that bacteria completely mobilized phosphate, forming 100% acid when grown in a medium containing Ca 3 (PO 4) 2 for 5 days. The ability of the bacteria to mobilize potassium was studied on a nutrient KAlSiO 4-containing medium. The bacteria were observed to mobilize potassium, forming 90-100% acid within 15 days. Based on the study of the 16S rRNA gene of bacteria, we identified rhizobacteria UT3, UT4, and UT9 as Rah-nella aquatilis.
... Rahnella was a Gram-negative, rod-shaped, facultatively anaerobic bacterium belonging to the family Yersiniaceae (Adeolu et al., 2016), and was widely distributed in a variety of environments, including soil, phyllosphere, water, seeds, food, some clinical samples, and even in American mastodon remains (Berge et al., 1991;Rhodes et al., 1998). Rahnella was first proposed in 1979, and normally consisted of six species including R. aquatilis (which was described as the type species of Rahnella), R. variigena, R. inusitata, R. bruchi, R. woolbedingensis, and R. victoriana by multilocus sequence analysis (Brady et al., 2014). ...
... Rahnella spp. were also reported to possess the capacity for nitrogen fixation (Berge et al., 1991). For, insurance, R. aquatilis HX2 was reported as a PGPR and could promote the growth of corn for the ability to fix nitrogen (Guo et al., 2012). ...
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Many Rahnella strains have been widely described as plant growth-promoting rhizobacteria with the potential to benefit plant growth and protect plants from pathogens. R. aceris ZF458 is a beneficial plant bacterium isolated from swamp soil with the potential for biocontrol. Strain ZF458 has shown broad-spectrum antagonistic activities against a variety of plant pathogens and exhibited a dramatic effect on controlling Agrobacterium tumefaciens in sunflowers. The R. aceris ZF458 genome sequence contained a 4,861,340-bp circular chromosome and two plasmids, with an average G + C content of 52.20%. Phylogenetic analysis demonstrated that R. aceris ZF458 was closely related to R. aceris SAP-19. Genome annotation and comparative genomics identified the conservation and specificity of large numbers of genes associated with nitrogen fixation, plant growth hormone production, organic acid biosynthesis and pyrroloquinoline quinone production that specific to benefiting plants in strain ZF458. In addition, numerous conserved genes associated with environmental adaption, including the bacterial secretion system, selenium metabolism, two-component system, flagella biosynthesis, chemotaxis, and acid resistance, were also identified in the ZF458 genome. Overall, this was the first study to systematically analyze the genes linked with plant growth promotion and environmental adaption in R. aceris. The aim of this study was to derive genomic information that would provide an in-depth insight of the mechanisms of plant growth-promoting rhizobacteria, and could be further exploited to improve the application of R. aceris ZF458 in the agriculture field.
... These microbes have been already reported as rhizopsheric bacteria associated with different plants except Erwinia aphidicola. In a report, R. aquatilis CF3 was isolated from the rhizosphere of wheat plant [37]. Similarly, R. aquatilis ISL19 from rhizosphere of soybean [38]. ...
... R. aquatilis was originally isolated from freshwater samples in France but has also been isolated from the soil, the rhizosphere, and the intestine of snails; occasionally, it has been isolated from human clinical specimens and food (Kämpfer, 2015;Asselin et al., 2019). Additionally, R. aquatilis has been reported as a nitrogen-fixing (Berge et al., 1991) bacterium and a biocontrol agent (Chen et al., 2009). R. aceris, originally isolated from Acer pictum sap in the Republic of Korea (Lee et al., 2020), has also been isolated from onion bulbs with symptoms of bacterial decay in Norway and the United States of America (Brady et al., 2022) and from bleeding cankers of black poplar (Populus nigra) in Iran, with pathogenicity demonstrated by the formation of water-soaked cankers on this host (Moradi-Amirabad and Khodakaramian, 2020). ...
Chapter
Rah'nel.la. L. fem. dim. n. suff. ‐ella , diminutive ending; N.L. fem. dim. n. Rahnella , named after Otto Rahn, the German‐American microbiologist who proposed the name Enterobacteriaceae in 1937. Pseudomonadota / Gammaproteobacteria / Enterobacteriales / Enterobacteriaceae / Rahnella Rahnella species are ubiquitous in the environment, regularly isolated from water, soil, and woody tree hosts as well as occasionally from human clinical samples. Cells are Gram stain negative, facultatively anaerobic, and motile rods. Species are psychrotolerant, able to grow at 4°C, and favor growth temperatures of 25–30°C. Carbon sources such as d ‐maltose, N ‐acetyl‐ d ‐glucosamine, α‐ d ‐glucose, and d ‐mannose are readily assimilated. Species form a monophyletic clade when phylogenetic analysis is based on multilocus sequence analysis (MLSA) or whole‐genome sequences. The major fatty acids are C 16:0 and C 17:0 cyclo; the percentage of C 18:1 ω7 c , summed feature 2 (iso‐C 16:1 and/or C 14:0 3‐OH), and summed feature 3 (C 16:1 ω7 c and/or iso‐C 15:0 2‐OH) is variable, with some species exhibiting these fatty acids in larger amounts. DNA G + C content (mol%) : 51.3–53.7 (genome analysis). Type species : Rahnella aquatilis Izard et al. 1979, VL7.
... These eight species contributed to the existing diversity of Rahnella with isolations of Rahnella victoriana, Rahnella variigena and Rahnella inusitata from bleeding cankers of oak; R. victoriana, R. variigena and R. woolbedingensis from asymptomatic alder and walnut; Rahnella bruchi from the gut of the Agrilus biguttatus beetle; Rahnella aceris and Rahnella laticis from sap of Acer pictum and Rahnella contaminans as a contaminant from MRSA agar plates [5][6][7]. In addition to their isolation from the natural environment, Rahnella species have been linked to nitrogen-fixation [8], metal and radionuclide sequestration [9] and biological control [10]; and more recently as possible pathogens of oak [11], poplar [12] and onion [13]. ...
Article
Bacteria isolated from onion bulbs suffering from bacterial decay in the United States and Norway were previously shown to belong to the genus Rahnella based on partial housekeeping gene sequences and/or fatty acid analysis. However, many strains could not be assigned to any existing Rahnella species. Additionally, strains isolated from creek water and oak as well as a strain with bioremediation properties were assigned to Rahnella based on partial housekeeping gene sequences. The taxonomic status of these 21 strains was investigated using multilocus sequence analysis, whole genome analyses, phenotypic assays and fatty acid analysis. Phylogenetic and phylogenomic analyses separated the strains into five clusters, one of which corresponded to Rahnella aceris . The remaining four clusters could be differentiated both genotypically and phenotypically from each other and existing Rahnella species. Based on these results, we propose the description of four novel species: Rahnella perminowiae sp. nov. (type strain SL6 T =LMG 32257 T =DSM 112609 T ), Rahnella bonaserana sp. nov. (H11b T =LMG 32256 T =DSM 112610 T ), Rahnella rivi sp. nov. (FC061912-K T =LMG 32259 T =DSM 112611 T ) and Rahnella ecdela sp. nov. (FRB 231 T =LMG 32255 T =DSM 112612 T ).
... IAA plays an important role in the physiological processes of plants, such as cell division (Patten and Glick 2002;Rangarajan et al. 2003;Yang et al. 2009). Rahnella aquatilis, isolated from drinking water and the rhizosphere of different plants (Brenner et al. 1998;Berge et al. 1991), is one of the plant-growth-promoting rhizobacteria (PGPR) (Beazley et al. 2009;Valverde et al. 2011). The main purposes of this study were to investigate (1) the effects of R. aquatilis on the As accumulation of V. natans and (2) the role of R. aquatilis in resistance of V. natans to arsenic stress. ...
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Vallisneria natans (Lour.) Hara is a suitable submerged plant for the phytoremediation of As-contaminated water. Rahnella aquatilis is one of the plant growth–promoting rhizobacteria. Influences of R. aquatilis on the arsenic accumulation and detoxification of V. natans were investigated. The results showed that As accumulation by V. natans could be significantly improved after R. aquatilis inoculated at the lower level of As (< 2 mg/L). At 0.5, 1, and 2 mg/L As levels, the As concentrations of V. natans with R. aquatilis were respectively 100.40%, 57.96%, and 22.62% higher than that of V. natans with no R. aquatilis. The concentration of As in V. natans was increased with the increasing the As concentration up to 1 mg/L, but it was decreased at 2 mg/L As. The correlation analysis showed that the As accumulated in the plant was positive correlated (R² = 0.977, p < 0.01) with indole-3-acetic acid (IAA) produced by R. aquatilis under different As levels. IAA may be the major factor affecting the As accumulation of V. natans. The results of malondialdehyde and superoxide dismutase, hydrogen peroxidase, and ascorbate peroxidase indicated that IAA produced by R. aquatilis had alleviated the arsenic stress on V. natans. The synthesis of IAA by R. aquatilis was related to the As levels. When the As was at 2 mg/L, the IAA that produced by R. aquatilis decreased and the promotion of R. aquatilis on As accumulation by V. natans reduced. However, R. aquatilis has a positive influence on the arsenic accumulation by V. natans at the lower As levels (< 2 mg/L), and it may be a potentially useful way to improve the removal of arsenic from contaminated water using submerged plants.
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The present investigation aims to isolate nitrogen fixing endophytic bacteria from cereals crops and their potential role in plant growth promotion of wheat (Triticum aestivum L.) for sustainable growth. In the present investigation, endophytic bacteria were isolated from different cereal crops growing in the Divine Valley of Baru Sahib, Himachal Pradesh, India and isolates were screened for nitrogen fixation. The nitrogenase activity exhibiting bacterial isolates were further screened for other plant growth promoting traits including solubilization of phosphorus, potassium, and zinc; production of indole-3-acetic acid, siderophores, ammonia, hydrogen cyanide and extracellular enzyme. The potential nitrogen fixing strains were molecularly identified and evaluated for the growth promotion of wheat. A total of 304 putative endophytic bacterial isolates were isolated from wheat, oats, barley, and maize using selective and complex growth media. Among 304 putative endophytic bacteria, 8 isolates exhibits nitrogenase activity. On the basis of nitrogenase activity and other plant promoting traits, two efficient strains i.e. EU-E1ST3.1 and EU-A2RNfb were molecularly identified using 16S rRNA gene sequencing and found that these strains belongs to genera Rahnella. The wheat inoculated with two selected nitrogen-fixing endophytic bacterial strains showed considerable enhancement in total chlorophyll, nitrogen, Fe and Zn content over the un-inoculated control. In comparison of two selected nitrogen-fixing endophytic bacterial strains, Rahnella aquatilis EU-E1ST3.1 was found to enhance better growth and physiological parameters and it might be developed as biofertilizers to establish a sustainable agriculture system. In the present investigation, the isolated potential nitrogen fixing endophytic bacteria could be used as biofertilizer or bioinoculant for growth of diverse cereal crops growing in hilly region for agricultural sustainability.
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