11
Na
Sodium
22.99
Essential:
animals, most microbes
Sodium
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(1) Sodium: Essential for Some Organisms
Sodium is necessary for certain organisms, like animals and some bacteria, but is far less essential in other microbial species and plants.
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In animal cells, Na is essential due to its role in the sodium-potassium pump, which maintains the resting potential of the cell (Grider et al., 2020). This pump is necessary for a variety of cellular processes, such as nervous system signaling, kidney function, and maintaining blood pressure.
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Most microbes use Na. Halophilic bacteria require Na, likely for the creation of Na+ gradients to drive transport processes (Ventosa et al., 1998). Na is also required in marine bacteria for a variety of cellular functions, such as active transport and flagellar rotation (Kogure, 1998).
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In contrast with animals and most microbes, Na is not a required nutrient for most plants (Nieves-Cordones et al., 2016). When present, Na may be a cellular osmolyte and can bind and activate some enzymes, although rarely is this function exclusive to Na. Most intracellular enzymes that require a monovalent cation prefer K, which is likely the physiological cofactor. Because of its requirement for animal but not plant life, Na availability can provide an important constraint at the ecosystem level (Kaspari, 2020).
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(2) Environmental Impact of Road Salt
Road salt is one of the primary sources of sodium pollution in colder regions of the world, and its use has continually increased over the past years (Pecher et al., 2019). Road salt has a number of environmental impacts, damaging vegetation and affecting water supply. These increasing salt levels in freshwater systems are changing the microbial community present, with increases in toxic cyanobacteria and halophiles.
(3) Na Pumps as Antimicrobial Targets
Some bacterial pathogens encode Na pumps, suggesting that they are able to use Na+ as a coupling ion to replace or add to H+, which creates the electrochemical gradient that is essential for many cellular processes. Recent studies show that these Na+ pumps, like the Na+-translocating NADH:ubiquinone oxidoreductase, could be potential targets in new drugs and vaccines against these bacterial pathogens (Hase et al., 2001).
(4) Production of Trehalose
Fungus A. sydowii produces trehalose when growing without sufficient NaCl in a state of hypo-osmotic stress (Pérez-Llano et al., 2020). Trehalose is a general stress response for fungi and maintains protein interactions and structure, allowing the fungi to survive at less-than-optimal conditions, such as Na limitation.
(5) Li substitutes for Na in some bacteria
Vibrio parahaemolyticus is a halophilic bacterium that requires high NaCl for growth. At low concentrations of NaCl, it has been found that Li, which resembles Na in many physical properties, is the most effective monovalent cation in restoring growth (Morishita & Takada, 1976). In a medium of 0.05 M NaCl, which is significantly below the minimum requirement, addition of LiCl, KCl, or sucrose can support growth by providing osmotic pressure. The functional substitution of Na for Li allows growth at concentrations as low as 0.003 M Na. Li can also functionally substitute for at least some Na in several species of Salinispora, a marine actinomycete, to maintain maximal growth and yield (Tsueng & Lam, 2010).