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Microbial biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Nitrogen fixation can be found distributed throughout nearly all bacterial lineages and physiological classes, but is not a universal property. The enzyme nitrogenase is responsible for nitrogen fixation and is very sensitive to oxygen, which will inhibit it irreversibly; consequently, all nitrogen-fixing organisms must possess some mechanism to keep the concentration of low oxygen. Some examples of these mechanisms include Heterocyst formation (cyanobacteria, e.g., Anabaena) where one cell does not photosynthesize but instead fixes nitrogen for its neighbors, which in turn provide it with energyRoot nodule symbioses (e.g., Rhizobium) with plants that supply oxygen to the bacteria bound to molecules of leghemoglobinAnaerobic lifestyle (e.g., Clostridium pasteurianum)Very fast metabolism (e.g., Azotobacter vinelandii)
Variability in Physiological, Biochemical, and Molecular Mechanisms of Chickpea Varieties to Water Stress
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Nataša Čerekovič, Nadia Fatnassi, Angelo Santino, Palmiro Poltronieri
Root nodules are highly specialized sink tissues in which at least one sucrose synthase isoform is strongly induced (Morell and Copeland, 1985): the reduction in sucrose synthase activity is considered one of the key factors responsible for the inhibition of SNF during drought (Gonzalez et al., 1995; Galvez et al., 2005). Under drought conditions, a decrease in sucrose synthesis activity in nodules was observed. This drop occurred simultaneously with a decrease in nitrogen fixation, with high correlation between both processes in adverse conditions. A drop in the concentration of phosphate, sugars, and organic acids was observed, indicating a decrease in carbon flow in the nodules, a drop that limited the supply of carbon to the bacteroid and the capacity of the bacteroid to fix nitrogen in various leguminous plants (Galvez, 2005; Ladrera Fernández, 2008). The stress occurred rapidly and intensely, while another pathway, dependent on ABA, involving control through leghemoglobin/oxygen, was activated. Treatment with exogenous ABA, carried out under conditions of water stress, played a beneficial role in the protein content of the plant. Likewise, recovery of the total activity of the metabolism of carbon and nitrogen enzymes in the nodules was observed. However, the application of ABA did not reverse the negative effect of the water stress and it was not possible to relate species of activated oxygen with the regulation of nitrogen fixation. In this context, the decrease in nitrogen fixation occurred in association with a limitation in the carbon flow in the nodules, caused by the inhibition of sucrose synthase activity under these conditions.
Promising Future Products from Microalgae for Commercial Applications
Published in Kalyan Gayen, Tridib Kumar Bhowmick, Sunil K. Maity, Sustainable Downstream Processing of Microalgae for Industrial Application, 2019
Triton is also developing a portfolio of interesting products. This includes a meat alternative using a recombinant yellow C. reinhardtii to produce meat proteins (leghemoglobin and myoglobin) that are combined with algal biomass to make a meat alternative.
Metal resistant rhizobia and ultrastructure of Anthyllis vulneraria nodules from zinc and lead contaminated tailing in Poland
Published in International Journal of Phytoremediation, 2018
Marzena Sujkowska-Rybkowska, Rafał Ważny
The environmental stress has a negative influence on the nodules structure, their functioning and hastens their senescence (Dupont et al. 2012). However, there are no studies concerning the anatomy and ultrastructure of Anthyllis nodules. Anthyllis nodules collected from the Bolesław heap were round in shape (Figure 3) and they differed in size, color and structure as they matured. Young nodules (to 0.5 mm) were white in a cross-section, whereas mature nodules (up to 4 mm) were pink in their centre due to the presence of leghemoglobin and effective nitrogen fixation (Figure 3A, B). The old, degenerated nodules were dark and sunken. Our observations have clearly shown that the Anthyllis nodules are the determined type of nodule (like on soybean, birdsfoot trefoil; Vance et al. 1982; Vance 2002), with a central zone containing uninfected and infected cells with symbiosomes, and a peripheral cortical region with vascular bundles (Figure 3C). The Anthyllis nodules (stressed and control one) were surrounded by peripheral cortex tissues (nodule cortex, endodermis and parenchyma). The nodule cortex cells were thick-walled and quickly peeled off (Figure 3C, F, G). The intercellular spaces of nodule parenchyma were intensively filled with glycoproteins (?) (Figure 3F, G). These glycoproteins fillings are important for the functioning of parenchyma as diffusion barrier (Parsons and Day, 1990). The outer nodule cortex reduces water loss from the nodule and plays the role of a defense barrier against pathogens (Hartmann et al. 2002). In our study, the nodule cortex and parenchyma cells of metal-treated nodules contained phenolics precipitates in vacuoles (Figure 3C, F–H). Similar vacuolar inclusions in nodule cells were observed in Pisum sativum under salinity stress (Borucki and Sujkowska 2008) and were classified as phenolic-like substances. The heavy metal stress induced production of phenolics due to their ability to metal chelation (Jun et al. 2003). Lafuente et al. (2015) showed in nodules the induction of genes related with phenolic synthesis upon exposure of Medicago plants to As. Phenolics induction was also observed in Phaseolus vulgaris exposed to Cd2+ (Smeets et al. 2005), in maize after Al treatment (Winkel-Shirley 2002) and under stress conditions, phenolics are also efficient reactive oxygen species (ROS)-scavengers (Rice-Evans et al.1997, Lafuente et al. 2015). Thus, phenolic compounds may contribute to the protection of legumes against reactive oxygen species under heavy metal stress (Pawlak-Sprada et al. 2011, Lafuente et al. 2015).