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Multi-Disciplinary Nature of Microbes in Agricultural Research
Published in Gustavo Molina, Zeba Usmani, Minaxi Sharma, Abdelaziz Yasri, Vijai Kumar Gupta, Microbes in Agri-Forestry Biotechnology, 2023
Zengwei Feng, Honghui Zhu, Qing Yao
P-acquiring is the core mechanism of AM fungi to promote growth of their host plants, especially in P-limited soils (Table 1.1). AM fungal extraradical hyphae (EH) continuously extend and then form a huge hypha network in the soil, which can efficiently absorb inorganic phosphate (Pi) via high-affinity fungal phosphate transporters such as GintPT and GigmPT from P-depleted soils (Fiorilli et al. 2013; Xie et al. 2016). Subsequently, Pi transported into the cytosol is incorporated into ATP in mitochondria and then is accumulated in the vacuoles as polyphosphate (polyPi), which is a high-efficiency form for translocating rapidly to arbuscules along EH and intraradical hyphae (IH) (Ezawa et al. 2003; Kikuchi et al. 2014). After that, polyPi is hydrolyzed into Pi by AM fungal phosphatase and exopolyphosphatase. Pi is exported from arbuscules to the periarbuscular space via fungal transporters (Xie et al. 2016), whereafter, it is transported across the periarbuscular membrane via mycorrhiza-specific and high-affinity phosphate transporters of their host plant and finally enters root cortical cells to meet plant P-requirement (Loth-Pereda et al. 2011; Yang et al. 2012). AM fungi made major contributions to P uptake of close to 100% to Solanum lycopersicum and Linum usitatissimum, and somewhat lower contributions to M. truncatula (60–80%) (Smith et al. 2004). According to the latest study, the maximum contribution of Rhizophagus intraradices to P uptake of Zea mays was up to 60% (Chu et al. 2020). These studies suggest that AM fungi play a vital important role in improving P nutrient of their host plants.
Long-term exposure to zinc oxide nanoparticles improves PAOs function in enhanced biological phosphorus removal
Published in Environmental Technology, 2023
Haining Huang, Lei Dong, Yang Wu, Shuyang Zhou, Xiong Zheng, Yinguang Chen
During EBPR processes, there are a number of enzymes accounting for the synthesis and degradation of polyphosphate, PHA and glycogen. Among them, PPK and PPX are two crucial enzymes involved in polyphosphate metabolism [34,48]. It has been found that PPK is responsible for the synthesis of an exopolyphosphatase and is associated with the bacterial membrane in some organisms, while PPX is an extracellular enzyme and is involved in polyphosphate degradation [49]. Our previous study showed that the shock load of a high concentration of ZnO NPs decreased the specific activities of PPX and PPK in the short term and inhibited the phosphorus removal correspondingly [31]. However, in this study, as was revealed in Figure 5, 50 mg/L of ZnO NPs did not have any adverse effect on the activities of PPX and PPK, but improved their activities somehow (PPK especially) (p <0.05). This was in accordance with the observed promoted phosphorus release and uptake (Figure 4) and the corresponding transformation of PHA and glycogen (Table 1) in the one-circle experiment. Similarly, the activities of PPX and PPK were observed to be recovered after long-term exposure to Ag NPs because of the stimulated production of EPS which could mitigate the toxicity of Ag+ to special enzymes [29]. Furthermore, ZnO NPs were reported to escalate the activities of various trans-peptidase enzymes because zinc could act as a cofactor in these enzymes [38]. Therefore, it is reasonable that after long-term exposure, the activities of key enzymes could be revived and even promoted with the presence of 50 mg/L ZnO NPs.
Effects of metal oxide nanoparticles on nitrification in wastewater treatment systems: A systematic review
Published in Journal of Environmental Science and Health, Part A, 2018
Vikram Kapoor, Duc Phan, A. B. M. Tanvir Pasha
Intracellular reactive oxygen species (ROS) are produced in the cells as products of normal metabolism and xenobiotic exposure.[88] Usually, the cells can convert ROS to water through electron transport chains and protect themselves from ROS damage by using several enzymes (i.e. glutathione peroxidase, catalases).[89] However, under harsh conditions such as in the presence of toxins (i.e. NPs), ROS can accumulate, and disrupt normal cellular functions.[81,90,91] Therefore, ROS production have been used as a potential cellular response to NPs based toxicity. Generally, ROS concentration can be measured with a fluorescence assay using a cell – permeant indicator such as dichlorodihydrofluorescein diacetate (H2DCF-DA).[81,91,92] For example, Zheng et al.[15] measured intracellular ROS production during ZnO NPs exposure in wastewater samples and indicated that the ROS production increased with an increase in ZnO NPs concentration. The high ROS production inhibited the polyphosphate-accumulation organisms and decreased the activities of nitrate reductase, exopolyphosphatase, and polyphosphate kinase.
Phosphorus and ammonium removal characteristics from aqueous solutions by a newly isolated plant growth-promoting bacterium
Published in Environmental Technology, 2020
Imen Daly, Salah Jellali, Ines Mehri, Maria A. M. Reis, Elisabete B. Freitas, Adrian Oehmen, Abdelwaheb Chatti
Effects of long idle period on nutrients removal from the mineral medium by the isolate PHR6, after feed, were presented in Figure 6(a–c)). As shown in Figure 6(a)), the long idle period affected bacterial cell growth by increasing the lag phase. Figure 6(b)) showed firstly an increase of phosphorus content in the medium until 8 h of incubation. Then, phosphorus contents decreased significantly with removal rates of 57.56 and 86.23 mgP gVSS−1 after 24 and 48 h of incubation, respectively. The initial increase of phosphorus contents in the medium reflected the release of phosphorus even under aerobic conditions. Previous studies suggested that the phosphorus release is linked to substrate uptake under strictly aerobic conditions when the electron donor (substrate) and the electron acceptor (nitrate or oxygen) are present simultaneously. This behaviour is characteristic of PAOs population [16]. Similar behaviour was also described by Li et al. [49] where about 6.2 mg L−1 of soluble orthophosphates were released by activated sludge during the first 15 min of the oxic stage in a sequence batch reactor (SBR) operated under oxic/anoxic/extended-idle regime. Similarly, Chen et al. [48] reported that the aerobic release of orthophosphates reached about 12 mg L−1 in an SBR operated under aerobic/extended-idle regime (cycles of: 210 min aeration, 55 min settling, 5 min decantation, and 210 min idle period). According to literature, the temporary phosphorus release was related to (i) shock nutrient load after starvation (therefore short cycles was usually adopted to cope with disturbances) [50,51] or to (ii) bacterial re-growth after long starvation period. In fact, it is admitted that prokaryotic homeostasis of polyphosphates is mainly controlled by two principal enzymes: polyphosphate kinase (PPK) which synthesizes poly-P from ATP and exopolyphosphatase (PPX) which releases inorganic phosphate (Pi) from poly-P [10,52,53]. Therefore, (PPK) and (PPX) are, respectively, responsible for phosphorus uptake and phosphorus release in biological phosphorus removal processes [10,53]. Moreover, it has been reported that (PPX) deficiency leads to accumulation of (Poly-P) and restriction of bacterial growth [52]. Thereby, it seems that phosphorus release, in our study, was linked to bacterial metabolic fitness regarding changing conditions and growth state. Probably, the long idle phase induced cell dormancy state as a response to stringent conditions. The medium renewal induced initially the phosphorus release marking growth resumption.