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Metal and Silicate Sorption and Subsequent Mineral Formation on Bacterial Surfaces: Subsurface Implications
Published in Herbert E. Allen, Metal Contaminated Aquatic Sediments, 2018
Susanne Schultze-Lam, Matilde Urrutia-Mera, Terry J. Beveridge
The outer membrane also has various types of proteins embedded in it which are usually present as high copy numbers of only a few different types [15, 4]. These proteins may either span the membrane or be embedded in either face. Generally there are three types of proteins present: (a) the “porins” which form water-filled channels through the outer membrane to allow the passage of hydrophilic solutes, (b) proteins which allow the binding of specific molecules for transport into the cell, and (c) those which serve to bind the outer membrane to the peptidoglycan layer. The latter, known as lipoproteins, are very small polypeptides (made up of approximately 58 amino acids) with a hydrophobic end that anchors the molecule to the outer membrane and a hydrophilic end bound to the peptidoglycan layer [15]. In E. coli only one third of the lipoprotein molecules are actually covalently bound to the peptidoglycan, the rest are associated with the bonded variety in a 2:1 stoichiometry, forming trimers [13].
Metabolic Engineering for the Production of a Variety of Biofuels and Biochemicals
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
In relation to solvent stresses caused by the accumulation of biofuels in the culture broth, the primary role to protect the cell such as E. coli, etc. from such stresses is made by outer membrane porin proteins, where the specific molecules can only move across these channels. Porins are the outer membrane proteins that produce large, open but regulated water-filled pores that form substrate specific, ion-selective, or nonspecific channels that allow the influx of small hydrophilic molecules and efflux of waste metabolites (Nikaido and Nakano 1980). The porin genes are under control of two-component system such as EnvZ-OmpR system, where EnvZ is an inner membrane sensor kinase, and OmpR is the cytosolic response regulator. In response to the environmental signals such as osmolarity, pH, temperature, nutrients, and toxins, EnvZ phosphorylates OmpR, where the phosphorylated OmpR controls the membrane protein expressions to protect the cell from the stresses (De la Cruz et al. 2007) as mentioned in Chapter 3.
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Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[biomedical, energy] Specialized cellular component (organelles) in living cells that use oxygen. The living cell (eukaryotic) has a nucleus. The mitochondria have the sole responsibility for the production and storage of energy to make the cell operate, specifically the formation of adenosine triphosphate (ATP) synthesis. In the process executed by the mitochondria, oxidation of simple organic compounds produces electrons generated during a chain of four membrane-bound enzymes, housed in the membrane. The reduction process is referred to as the electron transport or respiratory chain. The final stage involves the reduction of oxygen to produce water, generating an electron movement that builds a proton gradient across the membrane. The proton gradient drives the ATP generation as a turbine. The mitochondria additionally house several metabolic enzymes that support the survival of the cell. The inner structure of the mitochondrial membrane uses surface enlargement for optimal performance, since all energy processes take place in the membrane itself, next to the storage in the liquid of the organelle. The outer membrane consists of a lipid bilayer that is freely permeable to a broad range of molecules. The permeability to the molecules, specifically smaller than about 5000 daltons, results from the abundance of a channel-forming protein called porin. Some of the enzymes in the mitochondrial fluid also assist in the production of phosphates that can be converted to ATP, by phosphorylating other nucleotides. Mitochondria have a diameter ranging from 0.5 to 1.0 µm and length ranging from 1 to 10 µm, depending on the type of cell in the biological system (see Figure M.114).
Pulsed electric field promotes the growth metabolism of aerobic denitrifying bacteria Pseudomonas putida W207-14 by improving cell membrane permeability
Published in Environmental Technology, 2023
Fan Wang, Liang Li, Xuejie Li, Xiaomin Hu, Bo Zhang
The most significant GO terms in enrichment analysis were selected as the main node of the directed acyclic graph (DAG), and the associated GO terms were displayed together through the inclusion relation. As shown in Figure 7, pore complex (GO:0046930) was one of the significant final GO terms of up-regulated DEGs at membrane (GO:0016020) Go term branch in cellular component. There were 12 genes up-regulated in pore complex, including 5 genes that have been characterized and 7 genes of hypothetical protein with unknown function (Figure 8, Table 1). These 5 up-regulated genes were all related to membrane porin, involving three genes encoding carbohydrate outer membrane porin (oprB-I, oprB-II, oprB-III), one gene encoding proline-specific outer membrane porin (opdB) and one gene encoding histidine-specific outer membrane porin (opdC). Membrane porin was defined as a transmembrane matrix protein present in the outer membrane of some Gram-negative (G−) bacteria, allowing substances with relatively small molecular weight to pass freely. OpdB and opdC were both specific membrane porin. OprB was described as a carbohydrate-selective membrane porin, which has been associated with the diffusion of carbohydrate. A previous study indicated that oprB would form a glucose-selective porin in the outer membrane of Pseudomonas aeruginosa and promoted the diffusion of glucose into cells [51]. In this study, opdB, opdC, and oprB were highly significant up-regulated, together with another 7 highly expressed hypothetical proteins, which confirmed that PEF could activate the activity of membrane porin. The activation of these membrane porins promoted the formation of protein transport pores, which enabled more specific nutrients to enter the cell through the transport of cell membrane, so as to be better utilized by cell growth metabolism. These findings were consistent with the results of flow cytometry analysis that reversible electroporation improved cell membrane permeability.