Utilization of Acetate byBeggiatoa

Abstract

A proposed system which would permit acetate incorporation into four-carbon compounds without the presence of key enzymes of the citric acid cycle or glyoxylate cycle is described. In this system, acetyl-coenzyme A (CoA) is condensed with glyoxylate to form malate, which, in turn, is converted to oxaloacetate. Oxaloacetate then reacts with glutamate to produce ax-ketoglutarate, which is subsequently converted to isocitrate. Cleavage of isocitrate produces glyoxylate and succinate. Thus, the proposed system is similar to the glyoxylate bypass in that malate is produced from glyoxylate and acetyl-CoA, but differs from both the citric acid cycle and the glyoxylate bypass, since citrate and fumarate are not involved. Fumarase, aconitase, catalase, citritase, pyruvate kinase, enolase, phosphoenolpyruvate carboxylase, lactic dehydrogenase, a-ketoglutarate dehydrogenase, and condensing enzyme were not detectable in crude extracts of Beggiatoa. Succinate was oxidized by a soluble enzyme not associated with an electron-transport particle. Isocitrate was identified as the sole compound labeled when C1402 was added to a reduced nicotinamide adenine dinucleotide, CO2 generating system (crystalline glucose-6-phosphate dehydrogenase and glucose-6-phosphate) in the presence of a-ketoglutarate. ' Published as technical paper no. 1875, Oregon Agricultural Experiment Station. This paper was taken in part from a dissertation submitted by Sheril D. Burton in partial fulfillment of the requirements for the Ph.D. degree

Organic nutrition of Beggiatoa sp

“…That clone 75-2a grows well only on acetate or compounds which are frequent metabolic precursors of acetate (pyruvate, lactate, and ethanol) points strongly to the operation of the tricarboxylic acid (15). This is in contrast to the findings of Burton et al (4). They argued against the operation of the tricarboxylic acid cycle in their Beggiatoa sp.…”

“…Winogradsky (31) and Keil (13) believed that heterotrophic nutrition was not possible, but the concentrations of organic compounds used in their studies were quite high. More recently, heterotrophic nutrition has become a well-established fact for Beggiatoa species (4,7,10,23,26), but various studies of the extent of growth on particular organic media have frequently yielded disparate results. Faust and Wolfe (10) and Scotten and Stokes (26), working with several Beggiatoa sp.…”

Vacuolar respiration of nitrate coupled to energy conservation in filamentous Beggiatoaceae

“…Alternative electron donor (Burton et al, 1966) Acetate respiration delivers electrons via complex I Vacuolar respiration of nitrate in Beggiatoaceae 2913 least some Beggiatoaceae are not strictly chemoautothroph (Burton et al, 1966). Upon addition of acetate ( Fig.…”

“…Specifically, it inhibits the transfer of electrons from iron-sulfur centres in complex I to ubiquinone (Ernster et al, 1963;Haley, 1978;Li et al, 2003;Cava et al, 2004). Complex I is needed in Beggiatoa to deliver electrons from acetate respiration to the ETC (Burton et al, 1966). Antimycin A (5 mM) was also used as an electron transport chain inhibitor that blocks the transport of electrons from ubiquinone to cytochrome c (Slater, 1973;Moir and Wood, 2001).…”

“…Myxothiazol (2 mM) inhibits the same complex as antimycin (Thierbach and Reichenbach, 1981a,b). Acetate (10 mM) can serve as an alternative electron donor in Beggiatoa and delivers electrons via complex I (Burton et al, 1966).…”