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Microbial Remediation of Persistent Organic Pollutants
Published in Narendra Kumar, Vertika Shukla, Persistent Organic Pollutants in the Environment, 2021
Bacteria import nutrients for growth from their environment and export metabolites by the processes of passive transport, active transport, and group translocation. Passive transport is a naturally occurring phenomenon and does not require the cell to expend energy, as substances move from an area of higher concentration to an area of lower concentration by a process called diffusion. Only small molecules like oxygen and carbon dioxide or lipid-soluble chemicals diffuse freely through the cytoplasmic membrane using this process. On the other hand, active transport uses transmembrane proteins to transport a substance against a concentration or electrochemical gradient, for which the cell has to spend some ATP molecules. These transport mechanisms make up the mass transport system of a bacterial cell. This mass transport, of the pollutant to the bacterial cell, is the rate-controlling step in the process of biodegradation. When a pollutant is lipophilic in nature, a bacterium can speed up its mass transport by production of surfactant (Mateju, 2016).
Computational and Experimental Approaches to Cellular and Subcellular Tracking at the Nanoscale
Published in Sarhan M. Musa, ®, 2018
Zeinab Al-Rekabi, Dominique Tremblay, Kristina Haase, Richard L. Leask, Andrew E. Pelling
The properties of the cell membrane depend on both the composition of the molecules it is constructed from and the nature of the molecules that the cell contains. The two major organic types of molecules that constitute the cell are either water-soluble (hydrophilic) or water-insoluble (hydrophobic) molecules. However, many proteins found in the cell are those that possess both hydrophilic and hydrophobic chemical groups (i.e., amphipathic molecules). The most popular of the amphipaths are the phospholipids They are elongated molecules about 2–3nm, long and contain one hydrophilic end and one hydrophobic end (Warren 1987). They are insoluble in water; nevertheless, due to their distinct structure, they can easily self-assemble to hide their hydrophobic groups and form a phospholipid bilayer, where two monolayers are in contact along their hydrophobic ends and only the hydrophilic sides are exposed to the aqueous surroundings (see Figure 9.1). This structure is the major component of the cell plasma membrane and is found embedded with many proteins that are required for transport across the membrane, signaling, and recognition. The plasma membrane is a semi-permeable structure, which controls the movement of substances in and out of the cells through either active or passive transport. Moreover, it contains proteins and lipids, which are involved in a variety of cellular processes such as cell adhesion, ion channel conductance, and cell signaling, all crucial in the transduction mechanism (Warren 1987). In addition, the membrane also serves as the attachment point for the cytoskeleton.
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Passive transport is a movement of biochemicals and other atomic or molecular substances across cell membranes. Unlike active transport, it does not require an input of chemical energy, being driven by the growth of entropy of the system. The rate of passive transport depends on the permeability of the cell membrane, which, in turn, depends on the organization and characteristics of the membrane lipids and proteins. The four main kinds of passive transport are: diffusion, facilitated diffusion, filtration and osmosis.
Optimization of ultrasound-assisted microemulsions of citral using biopolymers: characterization and antifungal activity
Published in Journal of Dispersion Science and Technology, 2022
Dulce María Miss-Zacarías, Maricarmen Iñiguez-Moreno, Montserrat Calderón-Santoyo, Juan Arturo Ragazzo-Sánchez
In addition, the microemulsions may guarantee excellent protection of EOs against degradation or evaporation.[62] Also, the subcellular size of micro- or submicron emulsions may promote the EOs interaction with the microbial cell membranes through four main routes (i) increased surface area and passive transport through the outer cell membrane improve the interaction with the cytoplasmic membranes[63]; (ii) fusion of the emulsifier droplets with the phospholipid bilayer of the cell membrane likely promotes the targeted release of the EOs at the desired sites[64]; (iii) sustained release over time[64] and (iv) the electrostatic interaction of positively charged nanoemulsions droplets with negatively charged microbial cell walls increases the concentration of EOs at the site of action.[65] Micro- and nano-emulsions prepared using EOs or their constituents are rapidly increasing significance in the development of biocontrol agents against pathogenic microbes and insects.[60]
Cadmium stress in plants: A critical review of the effects, mechanisms, and tolerance strategies
Published in Critical Reviews in Environmental Science and Technology, 2022
Taoufik El Rasafi, Abdallah Oukarroum, Abdelmajid Haddioui, Hocheol Song, Eilhann E. Kwon, Nanthi Bolan, Filip M. G. Tack, Abin Sebastian, M. N. V. Prasad, Jörg Rinklebe
Generally, trace elements are taken up in the bivalent form (Fontes et al., 2014; Gupta et al., 2016). Cd2+ has to cross root cell walls using the same transporters as those of Ca2+, Fe2+, Mg2+, Cu2+, and Zn2+ (Fontes et al., 2014; Ismael et al., 2019; Villiers et al., 2012). Cadmium may pass from soil solution to plant roots through the cell walls using passive transport (diffusion) (Redjala et al., 2011; Rog Young et al., 2015). Moreover, it has been reported that active transport is used by Cd to cross the plasma membrane of root cells by the involvement of nonspecific membrane transport proteins (zinc transporter [ZIP] and iron transporter [IRT]) and metals pumping ATPase (Gallego et al., 2012; Sebastian & Prasad, 2018; Wu et al., 2015; Yamaguchi et al., 2011).
Alleviation of boron toxicity in plants: Mechanisms and approaches
Published in Critical Reviews in Environmental Science and Technology, 2021
Tianwei Hua, Rui Zhang, Hongwen Sun, Chunguang Liu
Boron toxicity has been reported to damage plant cell membranes through lipid peroxidation, which may induce an increase in membrane permeability. Since passive transport across the cell membrane is a primary mechanism of B uptake in plants (Cervilla et al., 2009), the increase of membrane permeability may result in more B absorption. The increase of membrane permeability induced by excess B has been observed in some studies by the determination of tissue electrolyte leakage (Gunes et al., 2007b; Eraslan et al., 2008). These studies found the application of Si reduced membrane permeability and consequently inhibited B uptake. An explanation for the protection of cell membrane integrity is the formation of amorphous silica (SiO2·nH2O) barrier (Exley, 2015). Another explanation is the Si-induced antioxidant responses, including the decreases in H2O2 generation and lipid peroxidation (indicated with malondialdehyde) (Soylemezoglu et al., 2009).