γ-Aminobutyric Acid Pathway and Modified Tricarboxylic Acid Cycle Activity During Growth and Sporulation of Bacillus thuringiensis

Abstract

Enzymatic analyses of Bacillus thuringiensis extracts suggested that a modified Krebs tricarboxylic acid cycle (without α-ketoglutarate dehydrogenase) can operate during sporulation in conjunction with the glyoxylic acid cycle and the γ-aminobutyric acid pathway.

Bacillus thuringiensis growth and toxicity

“…These enzymes are fully derepressed when sporulation begins. As BT shows no o~-ketoglutarate dehydrogenase activity, it has been concluded that an incomplete TCA cycle is present in this microorganism (7,26). The latter demonstrated the presence of the y-aminobutyric acid pathwayl which transforms glutamate to succinate, thus circumventing the t~-ketoglutarate dehydrogenase step.…”

“…The transfer of nitrogen from glutamate to other metabolites is catalyzed mainly by glutamate oxaloacetate transaminase and, to a lesser extent, by glutamate pyruvate transaminase and glutamate dehydrogenase. The pathways for ammonia assimilation are catabolized by alanine dehydrogenase and glutamate dehydrogenase (26,30). Although glutamate synthase and glutamine synthetase have been found in Bacillus megaterium (31,32), Bacillus licheniformis (33), and Bacillus subtilis (34), as far as the authors are aware, no report about the presence of this system in BT has been made.…”

Sporulation, Structure Assembly, and Germination in the Soil Bacterium Bacillus thuringiensis: Survival and Success in the Environment and the Insect Host

“…The γ-aminobutyric acid (GABA) shunt is an additional routing for the TCA cycle and is correlated with spore and parasporal crystal formation in B-thuringiensis [182,184]. GABA synthesis is through glutamate decarboxylation catalyzed by glutamate decarboxylase.…”

Kinetic Characterization and Molecular Modeling of NAD(P)+-Dependent Succinic Semialdehyde Dehydrogenase from Bacillus subtilis as an Ortholog YneI

“…In spore-forming Bacillus species, the required energy for survival is produced using the modified metabolic pathway, such as γ-aminobutyric acid (GABA) degradation pathway, during sporulation [3,17]. One of the antibiotic resistance mechanisms of spore-forming bacteria is the utilization of a modified metabolic pathway in order to bypass the action of antibiotics [3,17]. Thus, the approach of these metabolic pathways for designing new antibacterial drugs has been considered as an attractive target to overcome bacterial resistance.…”

“…On the other hand, in the high concentration range, the term K m /[S] is neglected and Eq. ( 1) becomes (3) and a plot of initial velocity versus [S] hyperbolic decay is used to determine V max and K i .…”