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Rapidly Changing Environment and Role of Microbiome in Restoring and Creating Sustainable Approaches
Published in Suhaib A. Bandh, Javid A. Parray, Nowsheen Shameem, Climate Change and Microbial Diversity, 2023
Manishankar Chakraborty, Udaya Kumar Vandana, Debayan Nandi, Lakkakula Satish, P.B. Mazumder
Agricultural soils are being contaminated with heavy metal causing threat to the soil ecosystem and biosphere at large. Application of plant—microbe associations to renew contaminated soils is an optimistic method that is even continued today. Heavy metal tolerant—plant growth promoting (HMT—PGP) microorganisms are immensely beneficial for their expertise in improving soil quality, enhancing plant growth, detoxifying and removing heavy metals from the soil. Some recent microcosm-scale phytoextraction experiments found that amalgamation of HMT—PGP microbes with thiosulfate increased mobilization and interest of Hg and As in L. albus and B. juncea grew in polluted soils containing the aforesaid metals. Some microorganisms producing enzyme 1-aminocyclopropane-1-carboxylate deaminase showed enhanced growth in heavy metals-contaminated regions (Mishra et al., 2017).
Extremophilic Microbes and their Extremozymes for Industry and Allied Sectors
Published in Ajar Nath Yadav, Ali Asghar Rastegari, Neelam Yadav, Microbiomes of Extreme Environments, 2021
Hiran Kanti Santra, Debdulal Banerjee
Their biotechnological potential includes their use as a plant growth promoter in terms of ammonia, hydrogen cyanide, IAA (Indole-3-acetic acid), gibberelic acid, siderophore production, phosphate solubilization, ACC (1-aminocyclopropane-1-carboxylate) deaminase activity. Isolates were also potent in their bio-control ability of the pathogenic microorganisms like Rhizoctonia solani and Macrophomina phaseolina (root rot pathogens) that causes world-wide global destruction of economically important food products in plains and high altitudes (cold climatic) of agricultural lands. The species richness was highest in case of Pangon Lake followed by Khardungla Pass, Chumathang, Indus River and Zanskar River. Evenness was highest in the Indus River where as Shanon and Simpson’s index was highest for Pangon Lake followed by Khardungla Pass (H-3.40 and D-0.96) and Chumathang regions (H-3.27 and D-0.96). In terms of representation of niche specific bacteria, the Pangon Lake represents the highest value of 7 followed by the Chumathang where-as Khardungla Pass had the lowest value of 2. Table 1.3 represents the other remarkable reports of extremophiles and their extremozymes from the Himalayan cold-deserts.
Plant Growth–Promoting Rhizobacteria (PGPR) and Bioremediation of Industrial Waste
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Sangeeta Yadav, Kshitij Singh, Ram Chandra
PGPR have the diverse functional role in maintaining the soil fertility as well as assisting phytoremediation to plants; they fix atmospheric nitrogen; produce phytohormones and siderophores; solubilize phosphate, potassium, and zinc; alleviate the various stress by secreting ACC (1-aminocyclopropane-1 carboxylate) deaminase enzyme; and control disease by suppressing or killing the phytopathogens. Several PGPR and their role are shown in Table 13.1 and Figure 13.2. Kloepper and Schroth (1978) said that soil containing competitive microflora, which exerts a beneficial effect on plant growth, is termed as PGPR. In accordance with Vessey (2003), soil bacterial species burgeoning in plant rhizosphere, which grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms and are collectively known as PGPR. Alternatively, Somers et al. (2004) classified PGPR based on their functional activities as (i) biofertilizers (increasing the availability of nutrients to plant), (ii) phytostimulators (plant growth promotion, generally through phytohormones), (iii) rhizoremediators (degrading organic pollutants), and (iv) biopesticides (controlling diseases, mainly by the production of antibiotics and antifungal metabolites). Furthermore, in most studied cases, a single PGPR will often reveal multiple modes of action, including biological control (Kloepper, 2003). Generally, PGPR can be separated into extracellular (ePGPR), existing in the rhizosphere, on the rhizoplane, or in the spaces between cells of the root cortex and intracellular (iPGPR), which exist inside root cells, generally in specialized nodular structures. Some examples of ePGPR are Agrobacterium, Arthrobacter, Azotobacter, Azospirillum, Bacillus, Burkholderia, Caulobacter, Chromobacterium, Erwinia, Flavobacterium, Micrococcous, Pseudomonas, and Serratia. Similarly, some examples of the iPGPR are Allorhizobium, Azorhizobium, Bradyrhizobium, Mesorhizobium, and Rhizobium of the family Rhizobiaceae. Most of rhizobacteria belonging to this group are gram-negative rods with lower proportion of gram-positive rods, cocci or pleomorphic. Moreover, numerous actinomycetes are also one of the major components of rhizosphere microbial communities showing plant growth beneficial traits. Among them, Micromonospora sp. (gram-positive, spore-forming, generally aerobic and form a branched mycelium), Streptomyces spp., Streptosporangium sp., and Thermobifida sp. have shown an enormous potential as biocontrol agents against different root fungal pathogens.
Endophytic Serratia sp. PW7 shifts bacterial endophytes in wheat (Triticum aestivum L.) to reduce pyrene contamination
Published in Bioremediation Journal, 2022
Shuang Li, Xuezhu Zhu, Xue Wang, Haiyan Zhao, Danqin Wang
Some mutualistic symbiosis existed between the host plant and endophytic Serratia sp. PW7. Colonized endophytic bacteria were reported to produce phytohormones and stimulate relative enzyme activities to promote the plant growth, for example siderophores, phosphate solubilization, 1-aminocyclopropane-1-carboxylate deaminase, nitrogen fixation, and indole-3-acetic acid production (Baoune et al. 2018). Gurska et al. (2009) reported that endophytic bacteria directly mineralized organic contaminants to detoxify and enhance the adaptation of plant to contaminants, leading to better plant growth. The degradation pathway transfer among the bacterial community members might make the endophytic bacteria adapt better in stable communities (Li et al. 2008). The vertical and horizontal gene transfer between introduced and native bacteria is the crucial factor in enhancing their fitness along with the host plant to survive under environment stress (Karmakar, Bindiya, and Hariprasad 2019). Inoculation with functional endophytic bacteria would provide an opportunity for degradation gene to transfer from inoculum to indigenous endophytic bacteria, and then help the host plants against contaminations. On the other hand, phytoalexins produced by plants in response to stimulation by endophytes were found to have distinct effects on the nutritional and metabolic functions of endophytes lead to increasing removal of PAHs (Lu et al. 2019).