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Selection and Improvement of Industrial Organisms for Biotechnological Applications
Published in Nduka Okafor, Benedict C. Okeke, Modern Industrial Microbiology and Biotechnology, 2017
Nduka Okafor, Benedict C. Okeke
In climacteric fruits (i.e. fruits that are picked before they are ripe) such as tomatoes, avocados, and bananas, the initiation of ripening is associated with a burst in ethylene biosynthesis. After harvesting, unripe fruits such as bananas may be treated with ethylene to induce simultaneous ripening. Ethylene has been described as a gaseous plant hormone: extraneous ethylene and ethylene generated by the plant equally induce ripening. Ethylene is a gaseous effector with a very simple structure. In higher plants, ethylene is produced from L-methionine. A major step is the production of the non-protein amino acid 1-aminocyclopropane-1-carboxylic acid (ACC), catalyzed by the enzyme ACC synthase. It has numerous functions in higher plants. It stimulates the following activities: the release of dormancy, leaf and shoot abscission, leaf and flower senescence, flower opening, and fruit ripening.
Bacterial-Assisted Phytoextraction Mechanism of Heavy Metals by Native Hyperaccumulator Plants from Distillery Waste–Contaminated Site for Eco-restoration
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Phytohormones that are produced by plant-associated bacteria, such as auxins, cytokinins, and gibberellins, can frequently stimulate growth and indeed have been considered the causal agents for altered plant growth and reproduction, and protect plants against both biotic and abiotic stress (Egamberdieva et al. 2017). As the most studied phytohormones, auxin IAA produced by PGPR via the indole-3-pyruvate (IPyA) pathway can increase the number of root hairs, the number of lateral roots, and the total root surface, leading to an enhancement of root exudation and mineral uptake from the soil (Costacurta and Vanderleyden 1995). This latter effect may act to further enhance the colonization surface and the exudation of nutrients for bacterial growth; thus the IAA synthesized by PGPB is finely modulated in response to environmental stresses (such as salinity, HMs, acid pH) associated with the soil and plant. In addition, bacterial IAA loosens plant cell walls and, as a result, facilitates an increasing amount of root exudation that provides additional nutrients to support the growth of rhizospheric bacteria. IAA that was incorporated by the plant stimulated the activity of the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, resulting in increased synthesis of ACC, and a subsequent rise in ethylene that inhibited root elongation (Leveau and Lindow 2005; Glick 2012; Patel and Saraf 2017; Rajkumar et al. 2012). Overall, bacterial IAA increases root surface area and length and thereby provides the plant greater access to soil nutrients. In addition, rhizospheric IAA synthesized by both plants and bacteria may act as a signal for soil Streptomyces to increase their production of antibiotics, which are lethal to fungal and bacterial phytopathogens, thereby inhibiting the growth of competing microbes and simultaneously protecting plants from phytopathogens (Egamberdieva et al. 2017). However, the molecular mechanisms involved in PGPR-assisted phytoremediation of HMs–contaminated environments are still largely unknown.
Growth responses of tomato plants (Solanum lycopersicum) to aluminium and nickel from nanoparticle suspensions and ionic solutions
Published in Soil and Sediment Contamination: An International Journal, 2023
Tamara Anahí Coll, Soledad Perez Catán, Marina Gosatti, Aldana Moyano, Monica Guraya, Cristina Pérez Coll, Teresa Mabel Fonovich
The suitable environment for the development of plants depends on the biological activity of the soil, which results from the physiological functions of the microorganisms. The need for energy, nutrients, water, and temperature in addition to the absence of unsuitable conditions for microorganisms is similar to that of plants. Young humus (labile or free) does not fix or bind to soil particles, it just mixes with them. Its C/N ratio is greater than 15, contains intense activity of microorganisms and is essential for soil fertility (Julca-Otiniano et al. 2006). The rhizosphere is the site of action of organisms which are on or near the root of the plants. Plant growth promoting rhizobacteria (PGPR) is the term which describes a beneficial association of soil bacteria with plants (Pishchik et al. 2021). Siqueira Freitas et al. (2018) have studied biological nitrogen fixation in soya bean plants related to Ni activity on the active sites of two metalloenzymes urease and dehydrogenase. El-Tarabily (2008) studied rhizosphere-competent streptomycete actinomycetes (SA) for their potential to produce 1-aminocyclopropane-1- carboxylic acid deaminase (ACC deaminase) and to enhance plant growth by lowering the ethylene content in tomato plants (Lycopersicon esculentum). According to the knowledge about the associations between plants and microorganisms, it is clear that not only soil conditions and/or its contamination will affect plant growth due to the needs of the plants themselves. The soil must also provide an appropriate environment for the microorganisms that interact with plants.
Effects of the promoting bacterium on growth of plant under cadmium stress
Published in International Journal of Phytoremediation, 2023
Deng Yang, Mingbo Zuo, Yueli Chen, Yuan Liu, Yueqing He, Haoming Wang, Xiaoxiao Liu, Jing Xu, Minjuan Zhao, Yuanyuan Shen, Ying Liu, Gao Tianpeng
Many studies have shown that inoculation with plant growth-promoting bacteria (PGP) is effective in increasing plant biomass (Corretto et al. 2020). PGPB can produce the phytohormones indoleacetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, among others, and also can produce iron carriers and dissolve phosphorus, which can fix nitrogen and dissolve inorganic phosphorus in the soil (Złoch et al. 2016; Raymond et al. 2021). Inoculation with mycorrhizal fungi significantly increased phosphorus content in maize shoots grown on strontium- and cadmium-contaminated soil, significantly reduced heavy metal content and metal toxicity in maize roots and shoots, and promoted maize growth (Chang et al. 2018). Enterobacteriaceae EG16 produces IAA and amino cyclopropane carboxylic acid (ACC) deaminases, which provide nitrogen to the soil, reduce the toxicity of heavy metals, and improve the remediation of heavy metal-contaminated soils by crocus (Saravanan et al. 2020). Taken together, microorganisms can mitigate metal toxicity while improving plant growth and phytoremediation processes.
Ethylene oxide review: characterization of total exposure via endogenous and exogenous pathways and their implications to risk assessment and risk management
Published in Journal of Toxicology and Environmental Health, Part B, 2021
CR Kirman, AA Li, PJ Sheehan, JS Bus, RC Lewis, SM Hays
Under normal conditions, bacteria are able to produce ethylene from amino acids (methionine, glutamic acid) and their metabolites (2-keto-4-methylthiobutyric acid or KMTB, 2-oxoglutarate or OG, 1-aminocyclopropane-1-carboxylic acid or ACC) (Fukuda, Ogawa, and Tanase 1993). The ability to produce ethylene from methionine or KMTB was assessed in 14 species of bacteria (Mansouri and Bunch 1989). Most bacterial species were able to generate ethylene from KMTB, while only two (E. coli SPAO, C. violaceum) were able to synthesize ethylene from methionine. Production was also dependent on the carbon/nitrogen source used in the growth medium (glutamate, glucose+ammonia). A survey of 757 bacterial species from soil found that 229 species (approximately 30%) were capable of producing ethylene (Nagahama et al. 1992). Most of the producing strains (225/229) were categorized as synthesizing ethylene from methionine (via KMTB). A smaller fraction of the producing species did so from other source material. These include one species generating ethylene from oxoglutarate, three species producing ethylene from meat extract, and two species whose source was not characterized. Induction of oxidative stress in bacteria (via menadione and paraquat addition) increased ethylene synthesis by cells, but not by cell-free extracts of E. coli (Mansouri and Bunch 1989). One additional species (P. aeruginosa) was able to produce ethylene from KMTB only when co-incubated with menadione or paraquat.