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Transport of Nutrients and Carbon Catabolite Repression for the Selective Carbon Sources
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
The first step in the metabolism of carbohydrates is the transport of these molecules into the cell (Fig. 4). In bacteria, various carbohydrates can be taken up by several mechanisms. Primary transport of sugars is driven by ATP, while secondary transport is driven by the electrochemical gradients of the translocated molecules across the membrane (Poolman and Konings 1992), where the secondary transport systems contain the symporters which co-transport two or more molecules, uniporters that transport single molecule, and antiporters that counter transport two or more molecules. Sugar symporters usually couple the uphill movement of the sugar to the downhill movement of proton (or sodium ion). Namely, the electrochemical proton (or sodium ion) gradient drives the sugar transport (Gunnewijk et al. 2001). Sugar uptake by group translocation is unique to bacteria and is involved in the phosphotransferase system (PTS) (Fig. 4). PTS is a transport system that catalyzes the uptake of a variety of carbohydrates and their conversion into their respective phosphoesters during transport (Deutscher et al. 2006, 2014, Kotrba et al. 2001, Gosset 2005, Luo et al. 2014).
Principles for quorum sensing-based exogeneous denitrifier enhancement of nitrogen removal in biofilm: a review
Published in Critical Reviews in Environmental Science and Technology, 2023
Ying-nan Zhu, Jinfeng Wang, Qiuju Liu, Ying Jin, Lili Ding, Hongqiang Ren
The phosphotransferase system (PTS) is a group of enzymes with specific functions and composed of enzyme I (EI), histidine phosphate carrier protein (HPr or NPr), and enzyme II (EII) compounds. It mainly includes two categories: carbohydrate PTS (PTSSugar) and nitrogen PTS (PTSNtr). Carbohydrate PTS is responsible for phosphorylating carbohydrates and then transporting them into cells, thereby regulating protein activity, carbon metabolism, and QS (Ha et al., 2018). In the case of nitrogen deficiency, the concentration of 2-OG increases (as a signal for nitrogen starvation), which directly inhibits the EI subunit of PTSSugar and prevents glucose input (Doucette et al., 2011). When the HPr subunit of PTSSugar binds to LsrK, it inactivates the kinase LsrK, which then inhibits AI-2 phosphorylation and its QS function. This indicates the ability of bacteria to respond rapidly to changing nutrient levels in terms of growth density (Ha et al., 2018).