A Model Representing a Physiological Role of CO2 at the Cell Membrane

Abstract

A model is presented suggesting the interaction of CO~ and bicarbonate on lipids of the cell membrane, The inteffacial tensions between water and oil (ber~zene) phases were measured using the stalagmometer and the sessile drop methods. Effects of electrolyte solutions and of CO~ on molecular arrangement ~at the interface were calculated. Chloride solutions against oleie acid in benzene 'produced little decrease in inteffacial tension from that measured for pure water against the oil phase. Presence or absence of CO2 caused no change in interfacial tension of water or chloride solutions against the oil phase. Bicarbonate salts in the absence of CO2 caused marked decreases in inteffacial tension from that measured for water or chloride solutions. Concomitant with this decrease in inteffacial tension were an increase in hydration of the interface and changes in molecular spacings O f the lipid. This hydration may be considered as reflecting a more ionic-permeable cell membrane. The addition of CO~ to the bicarbonates caused an increase in interfaeial tension of the model, approaching that of the chlorides, with decreased hydration of the interface. Viewed as occurring at the cell membrane this would make the lipid more continuous and decrease the ease of ionic penetration. In this way the action of bicarbonates and CO2 at the interface suggests an explanation of the action of CO~ on the cell. I N T R O D U C T I O NIncreased tensions of CO 2 have marked effects on living systems. Perhaps the most prominent alteration is decreased excitability of the organism or cell. This action of CO 2 is interwoven with the problem of narcosis and remains to be explained. Investigations concerned with CO~ effects have led to the question as to whether CO 2 as a gas, bicarbonate ions, or hydrogen ions are responsible for the cellular changes (e.g., Tomita, 1935;Becker, 1936; Niedergerke and St/~mpfli, 1953; and McElroy, Gerdes, and Brown, 1958). Numerous and varied biological effects of CO2 have recently been reviewed by Loomis (1957).

Three functional β-carbonic anhydrases in Pseudomonas aeruginosa PAO1: role in survival in ambient air

“…In the former case, the need for CO 2 is attributed to CO 2 fixation in biosynthetic reactions, and CAs, as discussed above, are shown to be commonly required for survival of these organisms at low levels of CO 2 (Kusian et al, 2002;Burghout et al, 2010;Hashimoto & Kato, 2003;Merlin et al, 2003). Whereas CO 2 inhibition, the phenomenon used in food preservation (Dixon & Kell, 1989), is consistent with its inhibitory effect on respiratory metabolism (Dixon & Kell, 1989), enzymic activity (King & Nagel, 1975) and/or alterations in cell membrane permeability (Sears & Eisenberg, 1961), the role of CAs in the organisms inhibited by elevated CO 2 has not been specifically addressed. One possible mechanism may relate to the role of CAs in the maintenance of intracellular pH homeostasis through the CO 2 /HCO 3 2 buffer system.…”

Physicochemical Basis for the Inhibitory Effects of Organic and Inorganic Salts on the Growth of Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum

“…Different biochemical mechanisms have been put forth to explain the antimicrobial activity of organic and inorganic salts, including inhibition of several steps of the energy metabolism (benzoate, bicarbonate, propionate, sorbate, and sulfite salts) (2,3,11,16,17,19,25) and complexation to DNA and RNA (aluminum and sulfites) (12,13,15,20,27,28). However, little is known about the physicochemical basis for the general antimicrobial action of salts.…”

CO 2 - and Anaerobiosis-Induced Changes in Physiology and Gene Expression of Different Listeria monocytogenes Strains

“…It has been hypothesized that CO 2 inhibits growth of bacteria by (i) changing the conformation of cellular enzymes and thereby decreasing the rate of the metabolic reactions (36); (ii) CO 2 product repression of carboxylases and decarboxylases (25); (iii) disrupting cell membrane structural integrity and/or specific functions (40); (iv) decreasing intracellular pH, which demands that ATP is used for reestablishing pH i rather than for growing (44); or (v) some combination of these mechanisms (9). It was reported recently that glutamate decarboxylase is essential for survival of L. monocytogenes in strong acid (6).…”