Diverse pathways for salicin utilization in Shigella sonnei and Escherichia coli carrying an impaired bgl operon

Abstract

Utilization of the aryl-β-glucosides salicin or arbutin in most wild-type strains of E. coli is achieved by a single-step mutational activation of the bgl operon. Shigella sonnei, a branch of the diverse E. coli strain tree, requires two sequential mutational steps for achieving salicin utilization as the bglB gene, encoding the phospho-β-glucosidase B, harbors an inactivating insertion. We show that in a natural isolate of S. sonnei, transcriptional activation of the gene SSO1595, encoding a phospho-β-glucosidase, enables salicin utilization with the permease function being provided by the activated bgl operon. SSO1595 is absent in most commensal strains of E. coli, but is present in extra-intestinal pathogens as bgcA, a component of the bgc operon that enables β-glucoside utilization at low temperature. Salicin utilization in an E. coli bglB laboratory strain also requires a two-step activation process leading to expression of BglF, the PTS-associated permease encoded by the bgl operon and AscB, the phospho-β-glucosidase B encoded by the silent asc operon. BglF function is needed since AscF is unable to transport β-glucosides as it lacks the IIA domain involved in phopho-relay. Activation of the asc operon in the Sal(+) mutant is by a promoter-up mutation and the activated operon is subject to induction. The pathway to achieve salicin utilization is therefore diverse in these two evolutionarily related organisms; however, both show cooperation between two silent genetic systems to achieve a new metabolic capability under selection.

Evolution of Aromatic β-Glucoside Utilization by Successive Mutational Steps in Escherichia coli

“…Absorbance at 600 nm was used to normalize for cell density. Enzyme activity was determined using the following formula: activity units ϭ A 509 ϫ 10 3 /A 600 ϫ 10 ϫ v ϫ t, where v (ml) is the volume of concentrated cells used in the assay and t (min) is the time of incubation (7).…”

“…The ascG gene encodes a repressor, ascF encodes a nonfunctional permease, and ascB encodes a phospho-␤-glucosidase. In the absence of bglB, activation of the asc operon through a promoter mutation enables salicin utilization, with AscB providing the ␤-glucosidase function and BglF contributing the permease function (7).…”

“…However, wild-type strains are unable to utilize arbutin because of the lack of a permease (9). In the absence of BglB, BglA can hydrolyze arbutin if BglF is active and can provide the transport function (7). The bglA locus of the Gram-positive bacterium Streptococcus mutans, which has 72% similarity with E. coli bglB, has been shown to be involved in esculin utilization (10).…”

Analysis of Lactobacillus rhamnosus GG in Mulberry Galacto-Oligosaccharide Medium by Comparative Transcriptomics and Metabolomics

“…The KEGG pathway definition of bglA is 6-phospho-beta-glucosidase; this intracellular enzyme of microorganisms catalyzes the hydrolysis of β(1,4)-linked cellobiose to produce glucose and glucose-6phosphate. Both of these reaction products can further enter the glycolysis pathway to be used in energy production (35,36). PET-PTS, a phosphoenolpyruvate-dependent sugar PTS, is a multi-component sugar transport system that usually coexists with 6-phospho-beta-glucosidase in cellulose-degrading bacteria.…”

Genome Insights of the Plant-Growth Promoting Bacterium Cronobacter muytjensii JZ38 With Volatile-Mediated Antagonistic Activity Against Phytophthora infestans

“…These sugars included monosaccharides (L-enantiomers of arabinose and rhamnose and D-enantiomers of ribose, xylose, galactose, glucose, fructose and mannose), disaccharides (D-enantiomers of cellobiose, maltose, lactose, melibiose, saccharose/sucrose and trehalose and gentiobiose), glycosides (amygdalin, arbutin, esculin and salicin), polysaccharides (D-raffinose), polyols (glycerol, galacticol, inositol, and D-mannitol), and salts (potassium gluconate). Isolate JZ38 has the genomic potential for the metabolism of arabinose (araBAD) (Fritz et al, 2014), arabinogalactan (bgaB/ganA, ganB) (Watzlawick et al, 2016), cellulose and cellobiose (bcsZ, two copies of bglX, bglB, yliI) (Xie et al, 2007), citric acid (citABCDEFXG, citA in plasmid p2) (Martín et al, 2004), galactose (lacA, galK, galT) (Chai et al, 2012), galacticol (gatD, gatYZ, gatR) (Nolle et al, 2017), glucose (pgm, yihX, glk, pgi), glycerol (glpK, glpD) (Holmberg et al, 1990;Yang et al, 2014), glycosides (bglB, bglA/ascB, ascG) (Desai et al, 2010;Zangoui et al, 2015), inositol (iolBCDEGHI) (Morinaga et al, 2010), lactose (lacA, lacZ) (Zeng et al, 2010), maltose/matlodextrin (malP, malQ, malS, malZ, glvA) (Boos and Shuman, 1998), mannitol (mtlD) (Wisselink et al, 2004), melibiose and raffinose (rafA, rafR, scrB) (Russell et al, 1992; Hugouvieux-Cotte-Pattat and Charaoui-Boukerzaza, 2009), rhamnose (rhaBAD) (Schwartz et al, 1974;Rodionova et al, 2013), ribose (rbsK, rbsD, rbsR) (Mauzy and Hermodson, 1992;Sigrell et al, 1998), sucrose (scrB, two copies of scrK, scrR) (Hugouvieux-Cotte-Pattat and Charaoui-Boukerzaza, 2009), trehalose (two copies of treA, treC, treR) (Baker et al, 2018), and xylose (xylAB) (Shamanna and Sanderson, 1979).…”