Glycogen Metabolism Impairment via Single Gene Mutation in the glgBXCAP Operon Alters the Survival Rate of Escherichia coli Under Various Environmental Stresses

Abstract

Glycogen is a highly branched polysaccharide that is widely present in all life domains. It has been identified in many bacterial species and functions as an important energy storage compound. In addition, it plays important roles in bacterial transmission, pathogenicity, and environmental viability. There are five essential enzymes (coding genes) directly involved in bacterial glycogen metabolism, which forms a single operon glgBXCAP with a suboperonic promoter in glgC gene in Escherichia coli. Currently, there is no comparative study of how the disruptions of the five glycogen metabolism genes influence bacterial phenotypes, such as growth rate, biofilm formation, and environmental survival, etc. In this study, we systematically and comparatively studied five E. coli single-gene mutants (glgC, glgA, glgB, glgP, glgX) in terms of glycogen metabolism and explored their phenotype changes with a focus on environmental stress endurance, such as nutrient deprivation, low temperature, desiccation, and oxidation, etc. Biofilm formation in wild-type and mutant strains was also compared. E. coli wild-type stores the highest glycogen content after around 20-h culture while disruption of degradation genes (glgP, glgX) leads to continuous accumulation of glycogen. However, glycogen primary structure was abnormally changed in glgP and glgX. Meanwhile, increased accumulation of glycogen facilitates the growth of E. coli mutants but reduces glucose consumption in liquid culture and vice versa. Glycogen metabolism disruption also significantly and consistently increases biofilm formation in all the mutants. As for environmental stress endurance, glycogen over-accumulating mutants have enhanced starvation viability and reduced desiccation viability while all mutants showed decreased survival rate at low temperature. No consistent results were found for oxidative stress resistance in terms of glycogen metabolism disruptions, though glgA shows highest resistance toward

Effects of NaCl Concentrations on Growth Patterns, Phenotypes Associated With Virulence, and Energy Metabolism in Escherichia coli BW25113

“…As for short-term adaptation, Biselli et al discovered that E. coli tended to decrease growth and maintenance rate in exchange of longer survival during carbon deficiency (Biselli et al, 2020). In this study, we examined the response of E. coli BW25113 to nutrient fluctuation, according to which, higher glucose concentration (0.8%) significantly improved the number of viable cells during 24-h culture (Figure 1A), which is consistent with previous studies (Wang et al, 2018(Wang et al, , 2020b. Bacterial replication is a key factor for host colonization, resource exploitation, and between-host transmission (Rohmer et al, 2011), high rate of which could contribute to bacterial virulence.…”

“…For glucose concentration, 1 × M9 minimal medium supplemented with higher level of glucose (0.8%) showed the highest number of viable cells in the culture, which was significantly different from those with 0.2% and 0.4% glucose (P-value <0.05) after culturing for 20 h (Figure 2A). This result is similar with previous studies performed on E. coli BL21(DE3) and E. coli DH5α, which confirms that high level of carbon source facilitates the replication of bacterial cells (Wang et al, 2018(Wang et al, , 2020b. As for osmotic stress, four sodium chloride (NaCl) concentrations (0, 1, 3.5, and 5%) were explored and statistical analysis showed that the number of viable cells in LB broth supplemented with 0% NaCl at 24 h is significantly higher than other tested groups, that is, LB broth supplemented with 1%, 3.5%, and 5% NaCl (Figure 2B).…”

“…As for glycogen metabolism, it was obvious that NaCl had a dose-dependent inhibitory effect on glycogen accumulation in E. coli (Figures 4D-F). In addition, glycogen accumulation also showed a time-dependent pattern when the culture was the same, that is, higher at 20-h and lower at 16and 24-h, which was also consistent with previous studies (Wang et al, 2020b). Moreover, trehalose accumulation in cultures with different NaCl concentrations also showed dose-dependent changing patterns (Figures 4G-I).…”

“…Among the DEGs, potential virulence genes that were up-regulated in high salinity conditions were discussed, which could contribute to the elucidation of the potential linkages between bacterial environmental adaptation and the evolution of virulence. Nutrient fluctuation is a commonly encountered abiotic stress for bacteria during their transmission between hosts and external environment (Wang et al, 2020b). Its driving force will change bacteria at both physiological and genetic level.…”

From Prokaryotes to Eukaryotes: Insights Into the Molecular Structure of Glycogen Particles

“…It has been reported that most bacteria accumulate glycogen in stationary phase when nitrogen source is limited while carbon source is abundant ( Wilson et al, 2010 ; Wang and Wise, 2011 ). However, through comparative analysis of glycogen content curves, it was noticed that glycogen metabolism in Escherichia coli had two stages, synthesis stage and degradation stage ( Strydom et al, 2017 ; Wang et al, 2020c ), which could be used to study the structural alteration of glycogen α particles. By using E. coli BL21(DE3) as a model organism, we recently revealed that glycogen α particles in bacteria followed a similar pattern of structural change as in healthy liver, that is, fragile during synthesis stage and stable during degradation stage ( Wang M. et al, 2021 ); in addition, fragile glycogen particles tend to have longer chain length distribution than stable glycogen particles ( Wang M. et al, 2021 ), which is also consistent with previous results in healthy and diabetic mice ( Hu et al, 2018 ).…”