Atp‐Dependent gold accumulation by living chlorella cells

Abstract

An effect of the Aii(II1) energy dependent concentration has been discovered by living ChZweZZa cells. The process 11s most intensive within the alkaline interval of pH, fading away in the dark, and is suppressed in the presence of arsenate (C 1 FM), fluorides (C 1 0.01 mM), sodium azide (1 mM), DCCD (10 pM), 2,4-dinitrophenol (0.1 mM). I n the dark the process is stimulated b y BTP (but not by ADP, or AIIP). ATP also neutralizes NaN, effect, but not that of DNP. An energy dependent AulIII) concentration is also observed for other green, blue-green, and, red singlecell algae.Inactivated algal biomass has various functional groups. Due to this fact it can sorb a great number of heavy metals [l-41. This peculiarity has been used in the sorbent construction for the recovery of the metal from solutions [5-'71. I n this case a physicochemical sorption is the principle of metal immobilization. But it is well-known that cells effectively redistribute between intra and extracellular media and several vital elements which are of great physiological importance (K, Na, Xg, Ca), while the sorption of such metals by cellular structures is rather small. On the other hand, various elements (Cu, Fe, etc. [S, 81) are effectively bound to algal biomass. The cell needs these elements in microamounts. Besides, some cells may bind the elements, for example, 81, Au [3, 81 that were not observed to participate in biochemical processes. It had been noticed that the values of heavy metal accumulation by intact and inactivated cells were essentially different [ 101. The latter is evidence of the importance of physiological processes and the cells interacting with heavy metals. Moreover, the comparison between liophilized Chlorella biomass ability to bind such element as Au [3] and living cells effectiveness in this process [9] showed that, firstly, the result was higher when living cells were used, and secondly, in the last case the sorption process can be controlled. So the aim of this study -to investigate the appropriateness of ionic gold concentration by functionally a.ctive Chlorella cells -was stipulated by the differences between living and inactivated Chlorella cells discovered. Besides, it has been taken into account that the sorption characteristics of liophilized Chlorella biomass for several gold compleses were presented in [3].

Peculiarities of live cells' interaction with micro- and nanoparticles

“…Even if we were able to show that this effect works for microparticles, it is completely unrealistic for nanoparticles. Reduction in size by at least 10-fold -as seen in the experiments by Pohl's group and in those by the Ukrainian group [27][28][29][30][31][32][33][34][35][36] -would require an electric field that was 10 times stronger to capture the nanoparticles. It is impossible to imagine cells emitting an electric field with a strength around 500 V/cm.…”

“…The results were published in international journals [27][28][29][30][31][32][33][34][35][36]. The cells used in the experiments were representative heterotrophic bacteria, such as Bacillus cereus, Bacillus fascidiosus, Bacillus subtilis, and Pseudomonas iodinum, and microalgae such as Chlorella vulgaris.…”

“…Experimentally-observed reversibility of the interaction of gold nanoparticles with live cells [27][28][29][30][31][32][33][34][35][36] requires special theoretical treatment because it is associated with cell metabolism.…”

“…The Ukrainian investigators had discovered some peculiar features of the interactions of microbial cells with gold nanoparticles that dramatically distinguished them from the typical interactions between nano-and micro-scale equilibrium objects [27][28][29][30][31][32][33][34][35][36]. Some bacteria collected large numbers of gold nanoparticles on their surfaces (Fig.…”

Accumulation of gold in the sheath ofPlectonema terebrans(filamentous marine cyanobacteria)

“…The more that can be understood about these organisms (especially bacteria), their specific activities, and their communities, the better the understanding will be of particular "signatures" useful in prospecting. Karamushka et al (1989Karamushka et al ( , 1991 demonstrated that seven genera of freshwater cyanobacteria concentrate Au 3+ from chloride solutions: Nostoc, Spirulina, Phormidium, Anabaena, Microcystis, Anacystis, and Synechococcus (Table 1). The first three of these are especially good concentrators, leaving only about 10% of the available gold in solution.…”