Isolation, characterization, and use for plant growth promotion under salt stress, of ACC deaminase-producing halotolerant bacteria derived from coastal soil.

Department of Agricultural Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361-763, Korea.
Journal of Microbiology and Biotechnology (Impact Factor: 1.4). 11/2010; 20(11):1577-84.
Source: PubMed

ABSTRACT In total, 140 halotolerant bacterial strains were isolated from both the soil of barren fields and the rhizosphere of six naturally growing halophytic plants in the vicinity of the Yellow Sea, near the city of Incheon in the Republic of Korea. All of these strains were characterized for multiple plant growth promoting traits, such as the production of indole acetic acid (IAA), nitrogen fixation, phosphorus (P) and zinc (Zn) solubilization, thiosulfate (S2O3) oxidation, the production of ammonia (NH3), and the production of extracellular hydrolytic enzymes such as protease, chitinase, pectinase, cellulase, and lipase under in vitro conditions. From the original 140 strains tested, on the basis of the latter tests for plant growth promotional activity, 36 were selected for further examination. These 36 halotolerant bacterial strains were then tested for 1- aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Twenty-five of these were found to be positive, and to be exhibiting significantly varying levels of activity. 16S rRNA gene sequencing analyses of the 36 halotolerant strains showed that they belong to 10 different bacterial genera: Bacillus, Brevibacterium, Planococcus, Zhihengliuella, Halomonas, Exiguobacterium, Oceanimonas, Corynebacterium, Arthrobacter, and Micrococcus. Inoculation of the 14 halotolerant bacterial strains to ameliorate salt stress (150 mM NaCl) in canola plants produced an increase in root length of between 5.2% and 47.8%, and dry weight of between 16.2% and 43%, in comparison with the uninoculated positive controls. In particular, three of the bacteria, Brevibacterium epidermidis RS15, Micrococcus yunnanensis RS222, and Bacillus aryabhattai RS341, all showed more than 40% increase in root elongation and dry weight when compared with uninoculated saltstressed canola seedlings. These results indicate that certain halotolerant bacteria, isolated from coastal soils, have a real potential to enhance plant growth under saline stress, through the reduction of ethylene production via ACC deaminase activity.

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    ABSTRACT: The main objective of this work is the study of the phylogeny, evolution and ecological importance of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, the activity of which represents one of the most important and studied mechanisms used by plant growth-promoting microorganisms. The ACC deaminase gene and its regulatory elements presence in completely sequenced organisms was verified by multiple searches in diverse databases, and based on the data obtained a comprehensive analysis was conducted. Strain habitat, origin and ACC deaminase activity were taken into account when analyzing the results. In order to unveil ACC deaminase origin, evolution and relationships with other closely related pyridoxal phosphate (PLP) dependent enzymes a phylogenetic analysis was also performed. The data obtained show that ACC deaminase is mostly prevalent in some Bacteria, Fungi and members of Stramenopiles. Contrary to previous reports, we show that ACC deaminase genes are predominantly vertically inherited in various bacterial and fungal classes. Still, results suggest a considerable degree of horizontal gene transfer events, including interkingdom transfer events. A model for ACC deaminase origin and evolution is also proposed. This study also confirms the previous reports suggesting that the Lrp-like regulatory protein AcdR is a common mechanism regulating ACC deaminase expression in Proteobacteria, however, we also show that other regulatory mechanisms may be present in some Proteobacteria and other bacterial phyla. In this study we provide a more complete view of the role for ACC deaminase than was previously available. The results show that ACC deaminase may not only be related to plant growth promotion abilities, but may also play multiple roles in microorganism's developmental processes. Hence, exploring the origin and functioning of this enzyme may be the key in a variety of important agricultural and biotechnological applications.
    PLoS ONE 01/2014; 9(6):e99168. · 3.53 Impact Factor
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    ABSTRACT: Microbial life can be found over a wide range of extreme conditions like high salinity, pH, temperature, pressure, light intensity, oxygen and nutrients. Halotolerant or halophilic microorganisms, are able to live in saline environments, offer potential applications in various fields of Biotechnology. The halotolerant or halophilic microorganisms are important for maintenance of soil condition and nutrient recycling in saline environment. The environment is ideally placed at the inter-phase between the terrestrial and marine environment and support a rich and diverse group of microorganisms. In this study, attempts were made to isolate the halotolerant marine bacteria and screen them for enzymes to be used for the decolorization of textile dyes and tannery effluent. A total of 192 halotolerant marine bacteria were isolated from Kelambakkam and Marakanam Salterns and named as AMETH101 to AMETH292. The isolated strains were tested for their growth at various salt concentrations such as 0M, 0.5M, 2.5M and 5M. All were found to grow well at 0.5M NaCl concentration. These organisms were studied for their ability to produce enzymes like lipase, tannase and protease. Among these strains, 107 have exhibited lipase activity, 41 strains exhibited tannase activity and 130 strains have exhibited protease activity. Totally 192 strains were tested for IAA production using qualitative assay and found that 41 strains showed positive activity and the remaining strains showed negative activity. For morphological characterization, KOH string test and catalase tests were performed. The results indicated that among the 192 strains, 138 strains were gram positive and remaining were gram negative strains while all the strains were positive for catalase test. This preliminary study has demonstrated that bioprospecting of halotolerant marine bacteria may yield potential microorganisms to be used in various environmental and biotechnological applications. Isolated halotolerant bacteria are very good producers of extracellular enzymes and IAA. These halotolerant bacteria with the combined ability of producing bioremediation enzymes and plant growth promoting hormones enhances the potential uses of them for the treatment and reuse of industrial effluents for the irrigation of ornamental plants. Halophiles are salt-loving organisms that inhabit hypersaline environments. They include prokaryotic and eukaryotic microorganisms with the capacity to balance the osmotic pressure of the environment and resist the denaturing effects of salts. Among halophilic microorganisms are a variety of heterotrophic and methanogenic archaea; photosynthetic, lithotrophic, and heterotrophic bacteria; and photosynthetic and heterotrophic eukaryotes (DasSarma and Arora, 2001). Most of
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    ABSTRACT: Dyes are the major toxic substances in all industrial wastewater and are highly carcinogenic to human beings and other soil and water living things. In this present study, 52 halophilic bacterial strains were isolated from water and sediments samples collected from Kelambakkam and Marakkanam salterns, nearby East Coast of Tamil Nadu, India and they were designated with unique codes as AMETH101 to AMETH152. They were screened for their ability to produce hydrolytic enzymes such as protease, lipase and tannase enzymes. On comparison, three strains namely, AMETH111, AMETH132 and AMETH148 have exhibited all of the enzyme activities tested and they were chosen to test their ability in decolorization of five different textile dyes namely Black'B' , Yellow MR , Red BSID , Blue M2R and Torque Blue 'G'. Among the three halophilic bacterial strains, AMETH148 exhibited 93.61% decolorization in Black-B, 68.74% decolorization in Yellow-MR, 72.84% in Torque Blue 'G', 91.27% Red BSID and 92.26% in Blue M2R compared to other two isolates and hence chosen for immobilization and further study. The halotolerant strain AMETH148 was immobilized with calcium alginate and dye decolorization experiments were conducted. After immobilization, there was a good improvement in decolorization percentage by the strain, as compared to their free cell counterparts and it was concluded that AMETH148 was the most efficient of all the bacterial strains in decolorizing all the five textile dyes. Decolorized dye solutions were subjected to plant growth promotion studies to determine to understand the level of bioremediation or detoxification. All the decolorized dye solutions were found to enhance the seed germination and seedling growth parameters of four different crop plants such as, Green gram (Vigna radiata), Black gram (Vigna mungo), Wheat (Triticum aestivum) and Paddy (Oryza sativa). This confirms that the treated dyes had no phytotoxic effect on crop plant seedlings. This study concluded the potential of halotolerant marine bacterium AMETH148 as a suitable candidate for the decolorization and bioremediation of textile dyes. Halophiles are extremophile organisms that are live in very high concentrations of salt (Roohi et al., 2012). Environments with high-salt concentrations are often populated by dense microbial communities. Various applications were found to be halophilic microorganisms which can be isolated from different saline environments and different strains even belonging to the same genus. Wastewater and soil rich in both organic matter
    01/2014; 11:69-79.

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