Glucose 6-phosphate dehydrogenase is required for sucrose and trehalose to be efficient osmoprotectants inSinorhizobium meliloti

Abstract

Inactivation of the zwf gene in Sinorhizobium meliloti induces an osmosensitive phenotype and the loss of osmoprotection by trehalose and sucrose, but not by ectoine and glycine betaine. This phenotype is not linked to a defect in the biosynthesis of endogenous solutes. zwf expression is induced by high osmolarity, sucrose and trehalose, but is repressed by betaine. A zwf mutant is more sensitive than its parental strain to superoxide ions, suggesting that glucose 6-phosphate dehydrogenase involvement in the osmotic response most likely results from the production of reactive oxygen species during osmotic stress.

Effect of Trehalose and Trehalose Transport on the Tolerance ofClostridium perfringensto Environmental Stress in a Wild Type Strain and Its Fluoroquinolone-Resistant Mutant

“…Trehalose is implicated in the protection of several bacteria from environmental stress [4, 5, 8, 9, 14] and we have shown its osmoprotective effect in C. perfringens by demonstrating that addition of trehalose to cultures of ATCC 13124 improved the tolerance of the cultures to increased salt concentration. By comparing the expression of genes proposed to be involved in the transport and metabolism of sucrose and trehalose [2, 24], in the mutant that could not grow on sucrose or trehalose in minimal medium, we have shown that treB and treC are involved in trehalose transport and metabolism.…”

“…Increased intracellular trehalose has been reported in bacteria after treatment with NaCl [12, 16]. 1 mM trehalose has been shown to protect bacteria against 0.5 M NaCl [14]. Although the protective role of sucrose has been shown during L-form formation in C. perfringens [17], the role of trehalose in the protection of C. perfringens from environmental stress is not known.…”

The Use of Transposon Insertion Sequencing to Interrogate the Core Functional Genome of the Legume Symbiont Rhizobium leguminosarum

“…Genes required for conversion of G6P into gluconate-6P (GN6P) through the ED pathway (overlapping the oxidative branch of the pentose phosphate pathway) resulted in a GI phenotype when mutated on both TY and VMM (Figure 4: reaction 1.1–2). The essential nature of these reactions may be due to several factors: (1) the NADPH generated during conversion (Spaans et al, 2015), (2) the possibly toxic accumulation of phosphorylated intermediates (Cerveñanský and Arias, 1984; Kadner et al, 1992), (3) the role of G6P in the biosynthesis of osmoprotectants (Barra et al, 2003), and (4) the need for carbon flux into the ED pathway for glycolytic growth (Arias et al, 1979; Glenn et al, 1984; Stowers, 1985). Conversion of GN6P into pyruvate through the ED pathway was determined to be VGI (Figure 4: reaction 1.3–4).…”

Physiology, genetics, and biochemistry of carbon metabolism in the alphaproteobacteriumSinorhizobium meliloti

“…The locus contains edd, predicted to encode 6PG dehydratase; pgl, predicted to encode 6-phosphogluconolactonase; and zwf, predicted to encode G6P dehydrogenase (Table 1). A strain carrying a zwf mutation was later shown to lack G6P dehydrogenase activity, reinforcing this region as an ED locus in S. meliloti (Barra et al 2003). A gene encoding KDPG aldolase has not been experimentally identified, but 2 putative KDPG aldolase genes are encoded on the chromosome (eda1, eda2) (Table 1) (Galibert et al 2001).…”