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1. Introduction
The agricultural soil plays an important role in global food production; as a result, crop soils are intensively farmed and planted to maximize yields. Farmers use high inorganic fertilizers in large quantities for many continuous years, which are really hazardous to the health of the crop soil and the quality of agricultural products [1]. ENFB species in peanut root nodules have been studied in order to understand the symbiotic relationship for nitrogen fixation and mutual benefits [2, 3]. Endophytic nitrogen-fixing bacteria play a crucial role in crop growth by promoting plant biomass and yield, helping to meet the growing global demand for food as the population increases [4, 5]. The root nodules of legumes are formed through a symbiotic relationship with ENFB called as rhizobia. These nodules have specialized structures and functions that facilitate the conversion of atmospheric N2 into plant-usable forms such as
2. Materials and Methods
2.1. Nodule Collection
Nodule samples of peanuts were from peanuts plants in Phuoc Hung commune, An Phu district, An Giang Province. Nodules, which were taken from peanut roots, were cut from the tumor using scissors and then the surface of the nodules were disinfected with CaOCl2 solution (4%) for 180 seconds before being cleaned with fresh water for 10 seconds. The collected nodule samples were in the size of 02 –03 mm in diameter. The light or pink nodules indicated that a community of nitrogen-fixing bacteria were acting and living inside [14, 15]. Later, nodules were soaked in 70% Alc. solution for 3 minutes and again washed with sterile distilled water. The clean nodules placed into an Eppendorf, containing sterile distilled water to form suspension. The above suspension was diluted from 10−2 to 10−6 and inoculated into 3 Petri dishes of YMA medium. The plates after inoculation were incubated at room temperature for 4-5 days, followed by observation for the growth of colonies, recording for the results and inoculation and purification [16].
2.2. ENFB Isolation
The nutrient medium composition of YMA consisted of yeast extract, mannitol, K2HPO4, MgSO4, NaCl, agar, pH = 7, and adding Congo red solution to obtain the 25 mg·L−1 content. YMA medium plates containing ENFB colonies were incubated at 28°C for 4 days. It was continued by streaking the separated isolates until forming completely pure colonies from white to pink and malleable and shimmery. The colonies of ENFB were then extracted from most other soil bacteria by filtration through YMA [14, 15].
The isolated ENFB genus was further classified through a number of selective media since most of the ENFB strains were Gram-negative and rod-shaped bacteria.
(i) YMA-BTB medium: this can identify ENFB colonies fast because of turning agar to slowly blue color
(ii) GPA-BCP medium: in this medium, ENFB strains poorly grew on because of high pH, used for checking the isolate purity [17].
(iii) Lactose agar medium: this medium was to check the yellow ring around the colonies after being flooded with reagent of Benedict, confirming the ENFB presence because of converting lactose to 3-ketolactose. It was called as the keta-lactose test [18].
(iv) Hofer’s alkaline medium: this medium was used for ENFB strains isolation, which could grow at high pH such pH > 6.5 [19].
(v) N-free medium: this medium was used by isolating free-living ENFB strains, which could utilize air N to form protein synthesis. In this research, it was used for testing colonies, which could develop N-free medium or not [20]. Checking Biochemistry was conducted using the ASM technology [21].
As shown in Figure 1, three pure colonies for endophytic bacterial genera were isolated from peanut nodules, which were selected as potential endophytic bacterial isolates with distinct morphological and colony color. The isolation and genomic identification of endophytic bacterial genera from peanut nodules by the YMA nutrient medium was conducted for the identification of isolates and Gram symbols for identification of their biological properties.
[figure(s) omitted; refer to PDF]
2.3. 16S rDNA Sequencing
Pure ENFB colonies were placed in Eppendorf tubes for DNA extraction, which were used by the GeneJET Genomic DNA Purification Kits from Thermal Scientific™. The 16S rDNA genes of the isolates was amplified by PCR using the primer set 20F 5′-CTACGGCAAGGCGACGCTGACG-3′ and 1500R 5′- GGTTACCTTGTTACGACTT-3′ [16, 22]. The sequence data were analyzed using MEGA software and compared to the most similar sequence in GenBank using the BLAST technique with an identity threshold of greater than 99.70% [23].
2.4. ENFB Characterization
The ENFB species were purified and characterized by Gram staining, catalase and oxidase tests, and macroscopic and microscopic observations. Their growth on YMA containing bromothymol blue was observed as well. In addition, the isolated species were tested for their resistance to heat and salinity, which are main factors for screening ENFB for the introducing an aim to them into degraded soils.
2.5. Thermal Tolerance
To determine the optimal incubation temperature, a set of 12 tubes containing YMA medium were prepared. Four tubes were prepared for each temperature and incubated at 25, 37, and 45 ± 1°C in an incubator. The growth of bacterial colonies was daily monitored for 7 days. The thermos tolerance test of the isolated ENFB species was performed, which were streaked on YMA agar plates and incubated at temperature ranging from 25, 37 and 45°C. The experiments were performed in quadruplicate for each species and the growth of colonies was recorded for one week [24].
2.6. Saline Tolerance
Nutrient agar containing different the NaCl concentrations (0.5%, 2%, 3%, 4%, and 5%) were inoculated by ten isolated colonies and incubated at 28°C with four replications and recorded the results after a week [24].
3. Results
3.1. Isolation and Characterization Identification
Nodulous samples were collected from Phuoc Hung commune, An Phu district, An Giang, Vietnam. These collected nodules were isolated by the new technologies for ENFB [25]. The isolation and genomic identification of rhizosphere N-fixing bacteria from peanut nodules by the YMA nutrient medium was conducted for the identification of isolates and Gram symbols for identification of their biological properties. Table 1 presents the identified species, noting that all isolates were negative for Gram staining after flooding.
Table 1
Identification of ENFB from peanut nodules.
| Symbol | Identity (rod shape) | YMA (clear pink) | YMA-BTB (yellow) | GPA | Hofer agar | Burk agar | Genus |
| B2B | (−) gram | (+) | (+) | (+) | (−) | (++) | ENFB |
| V1 | (−) gram | (+) | (+) | (+) | (−) | (++) | ENFB |
| V2 | (−) gram | (+) | (+) | (+) | (−) | (++) | ENFB |
| 18 | (−) gram | (+) | (+) | (+) | (−) | (++) | ENFB |
| V4 | (−) gram | (+) | (+) | (+) | (−) | (+) | ENFB |
| V5 | (−) gram | (+) | (+) | (+) | (−) | (++) | ENFB |
| 2 | (−) gram | (+) | (+) | (+) | (−) | (+) | ENFB |
| 3 | (−) gram | (+) | (+) | (+) | (−) | (+) | ENFB |
| 4 | (−) gram | (+) | (+) | (+) | (−) | (+) | ENFB |
| 5 | (−) gram | (+) | (+) | (+) | (−) | (+) | ENFB |
Note: (−): negative gram; (−): no reaction; (++): strong reaction.
The sequencing results (Table 2) showed that the similarity of the ten selected species was ≥99.5% compared to the standard ENFB species. The NCBI database (https://www.ncbi.nlm.nih.gov/genbank/) was used to identify their highest similarity.
Table 2
Identification of ENFB isolates by partial sequencing of 16S rRNA.
| Symbol | Strains | Similarity (%) | 16s rRNA sequence (5′ ⟶ 3′) | GenBank accession no. |
| B2B | Bacillus aryabhattai strain CM44 | 100 | 1–1457 bp | KC503992.1 |
| V1 | Enterobacter asburiae strain IIWM-JS-07L | 99.74 | 1–1406 bp | MT158657.1 |
| V2 | Klebsiella quasipneumoniae subsp. similipneumoniae strain CW-D 3 | 99.65 | 1–1456 bp | NR_132596.1 |
| 18 | Bacillus songklensis strain KCa6 | 99.93 | 1–1495 bp | OP437689.1 |
| V4 | Enterobacter cloacae subsp. dissolvens strain LMG 2683 | 99.65 | 1–1543 bp | NR_044978.1 |
| V5 | Enterobacter cloacae strain ATCC 13047 | 99.65 | 1–1543 bp | NR_102794.2 |
| 2 | Bacillus sp. strain NTLG2-20 | 100 | 1–1424 bp | OP890980.1 |
| 3 | Priestia aryabhattai strain AFS098338 | 99.92 | 1–1528 bp | OP986875.1 |
| 4 | Enterobacter asburiae strain cjy142 | 99.63 | 1–1380 bp | MN177198.1 |
| 5 | Enterobacter mori strain cjy13 | 99.93 | 1–1442 bp | MN177190.1 |
Table 3 illustrates the adaptability of ten ENFB strains to the temperature range of 25–45°C, within which they were capable of surviving and growing. Notably, the optimal temperature range for their development fell between 37 and 45°C. Excessive or insufficient temperatures in agricultural environments can adversely affect plant growth and nodule formation, ultimately compromising the nitrogen-fixing efficiency of ENFB [26]. YMA medium containing different NaCl concentrations (0.5%, 2%, 3%, 4%, and 5%) were inoculated at 28°C for 48 hours. The isolates grew in the different NaCl concentrations, which were then observed and compared together (from low to high NaCl concentrations). The salt tolerance test observed that most survived at 0.5% and 2% salinity (except Enterobacter cloacae subsp. dissolvens strain LMG 2683 and Enterobacter mori strain cjy13), while at 4%, only 3 isolates (species: B2B, V1 and 18) and at 5%, only 2 isolates survived, namely, V1 and 18. Most of ten ENFB strains could adapt to the range of 25°C and 45°C (except Enterobacter cloacae subsp. dissolvens strain LMG 2683 and Enterobacter mori strain cjy13 at 25°C) [27]. In this study, the pH effect of selected colonies on the YEMA semisolid medium (acidified with H2SO4) was investigated after 5 days of incubating. The results showed that seven out of ten selected strains exhibited weak growth at
Table 3
Tolerance of selected strains to high temperature, salt, and pH in vitro [27].
| Symbol | References species | NaCl (%) | Temperature (°C) | pH | ||||||||
| 0.5 | 2 | 3 | 4 | 5 | 25 | 37 | 45 | 4.5 | 7 | 8.5 | ||
| B2B | Bacillus aryabhattai strain CM44 | ++ | + | ++ | + | − | ++ | ++ | + | ++ | ++ | + |
| V1 | Enterobacter asburiae strain IIWM-JS-07L | ++ | ++ | ++ | ++ | + | ++ | ++ | + | ++ | ++ | ++ |
| V2 | Klebsiella quasipneumoniae subsp. similipneumoniae strain CW-D 3 | ++ | + | + | − | − | ++ | ++ | + | + | ++ | ++ |
| 18 | Bacillus songklensis strain KCa6 | ++ | + | ++ | + | + | ++ | ++ | + | ++ | ++ | + |
| V4 | Enterobacter cloacae subsp. dissolvens strain LMG 2683 | ++ | − | − | − | − | − | ++ | + | + | ++ | − |
| V5 | Enterobacter cloacae strain ATCC 13047 | ++ | + | − | − | − | ++ | ++ | + | + | ++ | − |
| 2 | Bacillus sp. strain NTLG2-20 | ++ | + | + | − | − | ++ | ++ | + | + | ++ | − |
| 3 | Priestia aryabhattai strain AFS098338 | ++ | + | − | − | − | + | ++ | + | + | ++ | − |
| 4 | Enterobacter asburiae strain cjy142 | ++ | + | − | − | − | ++ | ++ | + | + | ++ | − |
| 5 | Enterobacter mori strain cjy13 | ++ | − | − | − | − | − | ++ | + | + | ++ | − |
Figure 2 shows that the three selected species, including Bacillus aryabhattai strain CM44, Enterobacter asburiae strain IIWM-JS-07L, and Bacillus songklensis strain KCa6, exhibited remarkable characteristics when being tested for their ability to withstand heat, salinity, and other conditions. Furthermore, they shared a high degree of similarity with high nitrogen-fixing species. These species were selected based on previous screenings and were represented in the phylogenetic tree. The phylogenetic determination used three selected isolates with reference neighboring sequences from the previous database. A close relationship of these branches was closely grouped together with the genera of Bacillus aryabhattai strain CM44, Enterobacter asburiae strain IIWM-JS-07L, and Bacillus songklensis strain KCa6.
[figure(s) omitted; refer to PDF]
4. Discussion
On Hofer medium, which had a high pH, the ability of selected species to grow well was considered as a key factor in assessing its potential to belong to the group of ENFB species [28]. All ten obtained strains with clear pink colonies on YMA. It is a main characteristic of Rhizobium strain, already explained by Somasegaran and Hoben [15]. The test of GPA-BCP medium aimed to check a culture purity of a highly nutritious medium. The results, as shown in Table 1, showed that all ENFB isolates were significantly developed on this medium. On contrary, other genus were weakly developed [29]. All identified ENFB species were checked for the nitrogen-fixing ability by Burk medium (without N) to determine their genera size. This result represented that isolated species developed well on agar medium (without nitrogen). These ENFB species were the highest priority selection to study on the field experiments [30–32]. The tests of oxidase and catalase showed that all rhizobial strains had positive results. These results were consistent with previous studies revealing that rhizobial strains usually give positive results for the oxidase and catalase reaction [33, 34]. The test of chemical traits showed different results dependent on each rhizobial species (Table 4). However, theses result proved that different factors of ENFB species were highly affected by their living environment [35, 36]. The 16S rRNA sequences of the ten selected strains, as presented in Table 2, were derived from the rhizosphere of peanut plants. This analysis, along with other cutting-edge molecular techniques, has facilitated the discovery of numerous new ENFB species. These findings have significantly expanded our knowledge of ENFB diversity and their valuable attributes. Overall, learning these new techniques is a means to enhance the reliability and effectiveness of molecular research and applications. [37]. The selected ENFB species could have the high adaption of NaCl concentration up to 3-4% [24] or even to 5% (w/v) NaCl [38]. However, NaCl concentration was below 1% (w/v), which was suitable for most ENFB species. Ten obtained species were suitable in
Table 4
Biochemical tests of ENFB.
| Symbol | Oxidase | Catalase | Urea hydrolysis | Nitrate reduction | Citrate utilization |
| B2B | (+) | (+) | (+) | (−) | (+) |
| V1 | (+) | (+) | (+) | (−) | (+) |
| V2 | (+) | (+) | (+) | (−) | (+) |
| 18 | (+) | (+) | (+) | (−) | (+) |
| V4 | (+) | (+) | (+) | (−) | (+) |
| V5 | (+) | (+) | (+) | (−) | (+) |
| 2 | (+) | (+) | (+) | (−) | (+) |
| 3 | (+) | (+) | (+) | (−) | (+) |
| 4 | (+) | (+) | (+) | (−) | (+) |
| 5 | (+) | (+) | (+) | (−) | (−) |
Note: (−): no reaction; (+): reaction.
5. Conclusions
Ten ENFB species were isolated, identified, and tested by various biochemical and molecular assays. Three selected potential species consisted of Bacillus aryabhattai strain CM44, Enterobacter asburiae strain IIWM-JS-07L, and Bacillus songklensis strain KCa6, which were tested for the abilities of thermal, saline pH tolerance, and for their categorization into groups to be used for further field studies to the ultimate goal of developing inoculants in future. Understanding ENFB and their host plant origins has enabled us to make more extensive and confident use of these positive species, as long as their optimal conditions are still well concerned.
Authors’ Contributions
Nguyen Van Chuong collected samples and contributed all research funds and wrote down the whole manuscript; Tran Le Kim Tri and Nguyen Van Chuong carried out the laboratory work (both isolation and molecular identification). The authors approved the final version of this manuscript.
[1] FAO, Global Assessment of Soil Pollution: Report, 2021.
[2] A. Peix, M. H. Ramírez-Bahena, E. Velázquez, E. J. Bedmar, "Bacterial associations with legumes," Critical Reviews in Plant Sciences, vol. 34, pp. 17-42, 2015.
[3] S. López-Fernández, V. Mazzoni, F. Pedrazzoliet, I. Pertot, A. Campisano, "A phloem-feeding insect transfers bacterial endophytic communities between grapevine plants," Frontiers in Microbiology, vol. 8, 2017.
[4] L. Chen, Q. Lu, L. Zu, X. Li, Z. Chen, L. Sun, W. Wang, Z. Lin, J. Zhao, N. Yamaji, J. F. Ma, M. Gu, G. Xu, H. Liao, "A nodule-localized phosphate transporter GmPT7 plays an important role in enhancing symbiotic N 2 fixation and yield in soybean," New Phytologist, vol. 221, pp. 2013-2025, 2019.
[5] R. Amin, M. R. Wani, A. Rainaet, S. Khursheed, "Induced morphological and chromosomal diversity in the mutagenized population of black cumin ( Nigella sativa L.) using single and combination treatments of gamma rays and ethyl methane sulfonate," Jordan Journal of Biological Sciences, vol. 12, pp. 23-30, 2019.
[6] K. Guo, N. Yang, N. Yu, L. Luo, E. Wang, "Biological nitrogen fixation in cereal crops: progress, strategies, and perspectives," Plant Communications, vol. 4, 2023.
[7] K. Mahmud, S. Makaju, R. Ibrahim, A. Missaoui, "Current progress in nitrogen fixing plants and microbiome research," Plants, vol. 9 no. 97, 2020.
[8] E. Michelle, D. Afkhami, L. Mahler, J. H. Burns, G. Marjorie, M. F. Weber, J. S. Wojciechowski, Y. Sharon, "Symbioses with nitrogen-fixing bacteria: nodulation and phylogenetic data across legume genera," Ecology, vol. 99 no. 2, 2018.
[9] B. Ren, X. Wang, J. Duan, J. Ma, "Rhizobial tRNA-derived small RNAs are signal molecules regulating plant nodulation," Science, vol. 365 no. 6456, pp. 919-922, 2019.
[10] A. Carter, M. Tegeder, "Increasing nitrogen fixation and seed development in soybean requires complex adjustments of nodule nitrogen metabolism and partitioning processes," Current Biology, vol. 26, pp. 2044-2051, 2016.
[11] N. Forrester, T. L. Ashman, "The direct effects of plant polyploidy on the legume-rhizobia mutualism," Annals of Botany, vol. 121, pp. 209-220, 2018.
[12] V. Sobolev, R. Arias, K. Goodman, T. Walk, V. Orner, P. Faustinelli, A. Massa, "Suppression of aflatoxin production in Aspergillus species by selected peanut ( Arachis hypogaea ) stilbenoids," Journal of Agricultural and Food Chemistry, vol. 66, pp. 118-126, 2018.
[13] A. Sathya, R. Vijayabharathi, S. Gopalakrishnan, "Plant growth-promoting actinobacteria: a new strategy for enhancing sustainable production and protection of grain legumes," 3 Biotech, vol. 7 no. 2, 2017.
[14] C. Wekesa, F. Acu, O. Ralf, "Isolation and characterization of high-efficiency rhizobia from Western Kenya nodulating with common bean," Frontiers in Microbiology, vol. 10 no. 12, 2021.
[15] P. Somasegaran, H. J. Hoben, Methods in Legume-Rhizobium Technology, 1985.
[16] A. Chibeba, S. Kyei-Boahen, A. M. Chibeba, S. Kyei-Boahen, M. F. Guimarães, M. A. Nogueira, M. Hungria, "Isolation, characterization and selection of indigenous Bradyrhizobium strains with outstanding symbiotic performance to increase soybean yields in Mozambique," Agriculture, Ecosystems & Environment, vol. 246, pp. 91-305, 2017.
[17] S. Upadhayay, N. Pareek, G. Mishra, "Short communication: isolation and biochemical characterization of Rhizobium strains from nodules of lentil and pea in Tarai agro-ecosystem, Pantnagar, India," Nusantara Bioscience, vol. 7 no. 2, pp. 73-76, 2015.
[18] J. Don, N. R. Brenner, J. T. S. Krieg, "Rhizobium," Bergey’s manual of systematic bacteriology, vol. 2, pp. 325-340, 2005.
[19] A. Hofer, "Methods for distinguishing between legume bacteria and their most common contaminant," Journal of the American Society of Agronomy, vol. 27 no. 3, pp. 228-230, 1935.
[20] M. Stella, M. Suhaimi, "Selection of suitable growth medium for free-living diazotrophs isolated from compost (Pemilihan medium pertumbuhan yang sesuai untuk bakteria pengikat nitrogen hidup bebas yang dipencil daripada kompos)," Journal of Tropical Agriculture and Food Science, vol. 38 no. 2, pp. 211-219, 2010.
[21] ASM, 2021, https://asm.org/Browse-By-Content-Type/Protocols
[22] A. Del-Canto, A. Sanz-Saez, A. Sillero-Martínez, E. Mintegi, M. Lacuesta, "Selected indigenous drought tolerant rhizobium strains as promising biostimulants for common bean in Northern Spain," Frontiers in Plant Science, vol. 14, 2023.
[23] P. Yarza, P. Yilmaz, E. Pruesse, F. O. Glöckner, W. Ludwig, K. H. Schleifer, W. B. Whitman, J. Euzéby, R. Amann, R. Rosselló-Móra, "Uniting the classification of cultured and uncultured bacteria and archaea using 16S rRNA gene sequences," Nature Reviews Microbiology, vol. 12 no. 9, pp. 635-645, 2014.
[24] A. Datta, R. K. Singh, S. Tabassum, "Isolation, characterization and growth of Rhizobium strains under optimum conditions for effective biofertilizer production," International Journal of Pharmaceutical Sciences Review and Research, vol. 32 no. 1, pp. 199-208, 2015.
[25] P. Somasegaran, H. J. Hoben, Handbook for Rhizobia: Methods in Legume-Rhizobium Technology, 2012.
[26] D. Rao, "Recent advances in biological nitrogen fixation in agricultural systems," Proceedings of the Indian National Science Academy, vol. 80 no. 2, pp. 359-378, 2014.
[27] X. Zhang, J. Tong, M. Dong, K. Akhtar, B. Heet, "Isolation, identification and characterization of nitrogen fixing endophytic bacteria and their effects on cassava production," PeerJ, vol. 10, 2022.
[28] Z. Lei, G. Jian-ping, W. Shi-qing, Z. Ze-yang, Z. Chao, Y. Yongxiong, "Mechanism of acid tolerance in a rhizobium strain isolated from Pueraria lobata (Willd.) Ohwi," Canadian Journal of Microbiology, vol. 57 no. 6, pp. 514-524, 2011.
[29] P. Mahaveer Sharma, K. Srivastava, S. K. Sharma, "Biochemical characterization and metabolic diversity of soybean rhizobia isolated from Malwa region of Central India," Plant Soil and Environment, vol. 56, pp. 375-383, 2009.
[30] S. Gauri, A. K. Singh, R. B. Bhatt, S. Pant, M. K. Bedi, A. Naglot, "Characterization of Rhizobium isolated from root nodules of Trifolium alexandrinum," International Journal of Agricultural Technology, vol. 7 no. 6, pp. 1705-1723, 2011.
[31] M. Park, C. Kim, J. Yang, H. Lee, W. Shin, S. Kim, T. Sa, "Isolation and characterization of diazotrophic growth promoting bacteria from rhizosphere of agricultural crops of Korea," Microbiological Research, vol. 160 no. 2, pp. 127-133, 2005.
[32] B. Singh, R. Kaur, K. Singh, "Characterization of Rhizobium strain isolated from the roots of Trigonella foenumgraecum (fenugreek)," African Journal of Biotechnology, vol. 7 no. 20, pp. 3671-3676, 2008.
[33] A. Hossain, S. K. Gunri, M. Barman, A. Sabagh, J. Teixeira da Silva, "Isolation, characterization and purification of Rhizobium strain to enrich the productivity of groundnut ( Arachis hypogaea L.)," Open Agriculture, vol. 4 no. 1, pp. 400-409, 2019.
[34] A. Tyagi, V. Kumar, V. Kumar, A. Tomar, "Isolation, identification, biochemical and antibiotic sensitivity characterization of Rhizobium strains from Vigna mungo (L.) Hepper, Cicer arietinum (L.) and Vigna radiata (L.) Wilczek in Muzaffarnagar, Uttar Pradesh India," International Journal of Current Microbiology and Applied Sciences, vol. 6 no. 12, pp. 2024-2035, 2017.
[35] K. Thin, S. W. He, X. Wang, Y. Wang, M. Rong, J. G. Han, X. Zhang, "Rhizobium rhizolycopersici sp. nov., isolated from the rhizosphere soil of tomato plants in China," Current Microbiology, vol. 78 no. 2, pp. 830-836, 2021.
[36] A. Panwar, S. Choudhary, M. Sharma, Y. K. Shrama, R. S. Meena, S. K. Malhotra, R. S. Mehta, O. P. Aishwath, "Morphological and biochemical characterization of Rhizobium isolates obtained from fenugreek ( Trigonella foenum )," Seed Research, vol. 40 no. 2, pp. 196-200, 2012.
[37] N. Nguyen, N. Hanh, T. T. M. Vo, K. M. Nguyen, D. C. Pham, T. T. Phung, T. T. M. Doan, T. T. P. Le, V. N. A. Nguyen, P. N. M. Ta, X. T. K. Tran, Q. M. Nguyen, D. T. Nguyen, "Isolation and characterization of Rhizobium spp. and Bradyrhizobium spp. from legume nodules," HCMCOUJS-Engineering and Technology, vol. 12 no. 2, pp. 70-98, 2022.
[38] Ç. Küçük, M. Kivanç, K. Merih, K. Engin, "Characterization of Rhizobium sp. isolated from bean," Turkish Journal of Biology, vol. 30 no. 3, pp. 127-132, 2006.
[39] J. Vincent, "The genus rhizobium," The Prokaryotes: A Handbook on Habitats, Isolation, and Identification of Bacteria, pp. 818-841, 1981.
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Abstract
This work was carried out to isolate and perform molecular identification and selection of endophytic nitrogen-fixing bacteria (ENFB) to be utilized as biofertilizer. In this research, nodulous samples of peanuts were collected from inside dyke areas, namely, Phuoc Hung of An Phu, An Giang, Vietnam. Ten colonies were isolated from nutrient agar plates containing YMA’s medium. All isolates were rod shaped, Gram negative, and no spore creation. Biochemical tests indicated that they were obligate aerobes, catalase, oxidase, urea hydrolysis, well motile ability, and no nitrate reduction. The salt tolerance observed that most survived at 0.5% and 2% salinity (except Enterobacter cloacae subsp. dissolvens strain LMG 2683), while at 4%, only 3 isolates (Bacillus aryabhattai strain CM44, Enterobacter asburiae strain IIWM-JS-07L, and Bacillus songklensis strain KCa6) and at 5% only, 2 isolates survived, namely, Enterobacter asburiae strain IIWM-JS-07L and Bacillus songklensis strain KCa6. The result showed that most of ten ENFB strains could adapt to the range of 25°C and 45°C (except Enterobacter cloacae subsp. dissolvens strain LMG 2683 and Enterobacter mori strain cjy13 at 25°C). Out of ten isolates, three were finally selected for the next studies, which potentially have N-fixing ability and are utilized as biofertilizer in agricultural cultivation.
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; Tran Le Kim Tri 2 1 Agricultural Faculty of An Giang University An Giang Province, VNU HCM City Vietnam
2 Center Laboratory of An Giang University An Giang Province, VNU HCM City Vietnam