Physiology and metabolism of pathogenic neisseria: tricarboxylic acid cycle activity in Neisseria gonorrhoeae

Abstract

Tricarboyxlic acid cycle activity was examined in Neisseria gonorrhoeae CS-7. The catabolism of glucose in N. gonorrheae by a combination of the Entner-Doudoroff and pentose phosphate pathways resulted in the accumulation of acetate, which was not further catabolized until the glucose was depleted or growth became limiting. Radiorespirometric studies revealed that the label in the 1 position of acetate was converted to CO2 at twice the rate of the label in the 2 position, indicating the presence of a tricarboxylic acid cycle. Growth on glucose markedly reduced the levels of all tricarboxylic acid cycle enzymes except citrate synthase (EC 4.1.3.7). Extracts of glucose-grown cells contained detectable levels of all tricarboxylic acid cycle enzymes except aconitase (EC 4.2.1.3), isocitrate dehydrogenase (EC 1.1.1.42), and a pyridine nucleotide-dependent malate dehydrogenase (EC 1.1.1.37). Extracts of cells capable of oxidizing acetate lacked only the pyridine nucleotide-dependent malate dehydrogenase. In lieu of this enzyem, a particulate pyridine nucleotide-independent malate oxidase (EC 1.1.3.3) was present. This enzyme required flavin adenine dinucleotide for activity and appeared to be associated with the electron transport chain. Radiorespirometric studies utilizing labeled glutamate demonstrated that a portion of the tricarboxylic acid cycle functioned during glucose catabolism. In spite of the presence of all tricarboxylic acid cycle enzymes, N. gonorrhoeae CS-7 was unable to grow in medium supplemented with cycle intermediates.

The Entner-Doudoroff pathway: history, physiology and molecular biology

“…Other organisms are known to utilize the Entner-Doudoroff pathway in a linear, catabolic mode. For example, in Neisseria gonorrhoeae, glucose is the only carbohydrate that can serve as an energy source and is catabolized by combined action of the Entner-Doudoroff (87% of carbon flux) and pentose phosphate pathways [30,31]. The end products of glucose metabolism are acetate and CO2, formed presumably via pyruvate dehydrogenase with acetyl CoA as an intermediate.…”

Effect of pH on the growth and glucose metabolism of Neisseria gonorrhoeae

“…Most of the acetate excreted into the growth medium contained carbons 2 and 3 and 5 and 6 of glucose. Additional studies (7) showed that the acetate produced under these conditions was not oxidized until either the glucose was depleted or the culture entered the stationary phase of growth.…”

“…Frozen stock cultures were prepared by the method of La Scolea and Young (12) and used for inocula as previously described (7). All liquid cultures were incubated at 370C ( Radiorespirometry and cell fractionations.…”

“…Pathways of glucose metabolism were determined by radiorespirometry as previously described (17). Acetate utilization was examined radiorespirometrically as described by Hebeler and Morse (7). All constituents were fractionated chemically in screwcapped centrifuge tubes by the procedure described by Morse et al (17).…”

The Hfq regulon of Neisseria meningitidis

“…A pathway or biological role was given based on KEGG [42] or Uniprot [43]. Pathway analysis was further refined to apply specifically to the N. meningitidis genome [44][45][46][47][48][49][50][51]. Operon information was derived from previous transcriptome experiments in H44/76 [52].…”