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Microbial Bioinoculants for Sustainable Agriculture
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Strains of Azospirillum are known to produce siderophores, which form complexes with the metal ions, thereby contributing to improve the iron nutrition of plants and offer protection from minor pathogens. Similarly, azospirilla form antibiotic substances that suppress plant diseases due to their fungistatic activity against a wide range of phytopathogenic fungi, e.g., protecting cotton plants against Thielaviopsis basicola and Fusarium oxysporum. The field experiments in Israel have demonstrated that Azospirillum-inoculated sorghum plants made better use of moisture stored in soils from winter precipitation than did uninoculated plants (Sarig et al., 1988). In both green house and field experiments, inoculated plants were efficient at absorbing nitrogen, phosphorus, potassium, and other microelements from soil than uninoculated plants. Even the synergistic effects of Azospirillum with Rhizobium on different leguminous crops have been reported where stimulation of nodulation may be due to an increase in production of lateral roots and in root hair branching, and this, in turn, has been proposed to be due to production of phytohormones by Azospirillum. Phytohormone production and modulation of plant defense–related genes through seed and foliar application of Azospirillum brasilense have been reported to improve the growth of maize (Fukami et al., 2017). Fasciglione et al. (2015) reported that growth and quality of lettuce increases in Azospirillum-inoculated plants grown under salt stress.
Gold Nanoparticles in Biology and Medicine
Published in Lev Dykman, Nikolai Khlebtsov, Gold Nanoparticles in Biomedical Applications, 2017
Thanks to their porous structure, gold nanocages (GNCs) can be easily discriminated from particles of a similar size (and moreover from smaller or larger particles), while analyzing TEM images with nanocage-based biomarkers. This property suggests utilizing GNCs in combination with common CG nanospheres for a multiplexed immunoelectron microscopy visualization of at least two different antigen moieties. Figure 2.3 serves as an example of such multiplexed immunoelectron microscopy labeling [40]. Shown here is an Azospirillum brasilense Sp245 bacterium, which lives on its own in soil or in close associations with plants in the rhizosphere, thus promoting growth and increasing the yield of many plant species. To discriminate between H-antigens (the polar flagellum antigens [PFL]) and O-antigens of a lipopolysaccharide (LPS) capsule, we used two types of GNP conjugates. Namely, 15-nm GNPs were functionalized with antibodies against H-antigens, and 50-nm GNCs were functionalized with antibodies against O-antigens. In the case of native bacteria, their LPS capsule covers both the bacteria surface and polar flagellum (Figure 2.3b).
Beneficial Microorganisms and Abiotic Stress Tolerance in Plants
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Antra Chatterjee, Alka Shankar, Shilpi Singh, Vigya Kesari, Ruchi Rai, Amit Kumar Patel, L.C. Rai
Microorganisms as biostimulants are involved in stimulating natural processes in plants for better nutrient uptake, abiotic stress tolerance, nutrient efficiency and crop quality. Potential biostimulant bacteria have been isolated from different ecosystems comprising saline, alkaline, acidic and arid soils. Examples of nitrogen-fixing free-living bacterium used as biostimulants include Azotobacter chroococcum, which registered its role in salt tolerance (Egamberdiyeva and Höflich, 2003), in Zea mays as well as Triticum aestivum and temperature tolerance (Egamberdiyeva and Höflich, 2004) in T. aestivum. Azospirillum brasilense, a plant growth promoting bacteria, provide drought (Pereyra et al., 2006, 2012; Romero et al., 2014) tolerance in T. aestivum and salt tolerance in Cypripedium arietinum (Hamaoui et al., 2001), Vicia faba (Barassi et al., 2006), Lactuca sativa (Fasciglione et al., 2015). Hartmannibacter diazotrophicus is a phosphate-mobilizing bacterium invol ved in salt tolerance in Hordeum vulgare (Suarez et al., 2015). Symbiotic nitrogen-fixing bacteria such as Rhizobium leguminosarum has also registered its role in salt tolerance in V. faba and Pisum sativum (Cordovilla et al., 1999). Plant growth promoting proteobacteria Azospirillum lipoferum reported providing tolerance against salt stress in Triticum aestivum (Bacilio et al., 2004). Burkholderia phytofirmans belongs to the ß-Proteobacteria and provides tolerance against cold in Vitis vinifera (Fernandez et al., 2012; Theocharis et al., 2012). Flavobacterium glaciei psychrophilic obligate aerobic bacterium provided cold tolerance in Solanum lycopersicum (Subramanian et al., 2016).
Principles for quorum sensing-based exogeneous denitrifier enhancement of nitrogen removal in biofilm: a review
Published in Critical Reviews in Environmental Science and Technology, 2023
Ying-nan Zhu, Jinfeng Wang, Qiuju Liu, Ying Jin, Lili Ding, Hongqiang Ren
In addition, QS can modulate bacterial motility and chemotaxis to promote colonization and metabolization, thus rapidly and adequately degrading pollutants. Pili and flagella play important roles in motility, adhesion, and the uptake and emission of proteins and DNA, which can disassemble rapidly under certain environmental conditions (Craig et al., 2019). Chemotaxis is the broad ability of motile microorganisms to guide their movement along chemical gradients (Keegstra et al., 2022). In Azospirillum brasilense, chemotaxis can be mediated by two pathways: Che1 and Che4, which affects nitrogen metabolization (nitrate assimilation and nitrogen fixation), depending on the transcription regulation of global regulator rpoN (encoding RpoN) (Ganusova et al., 2021). Moreover, when the cells sense the carrier surface, the QS gene rhl is expressed, regulating the production of EPS and surfactants, controlling microbial chemotaxis through flagella, and forming biofilms (Saxena & Gupta, 2020).