A functional glycogen biosynthesis pathway in Lactobacillus acidophilus: expression and analysis of the glg operon

• Published in: Molecular microbiology Vol. 89; no. 6; pp. 1187 - 1200
• Main Authors: Goh, Yong Jun, Klaenhammer, Todd R.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.09.2013; BlackWell Publishing Ltd
• Subjects: 1,4-alpha-Glucan Branching Enzyme - genetics; 1,4-alpha-Glucan Branching Enzyme - metabolism; Bile - metabolism; Biosynthetic Pathways - genetics; Carbon - metabolism; Energy Metabolism; Enzymes; Gene Deletion; Gene Expression Regulation, Bacterial; Glucose - metabolism; Glycogen - biosynthesis; Glycogen Phosphorylase - genetics; Glycogen Phosphorylase - metabolism; Glycogen Synthase - genetics; Glycogen Synthase - metabolism; Humans; Lactobacillus acidophilus; Lactobacillus acidophilus - genetics; Lactobacillus acidophilus - growth & development; Lactobacillus acidophilus - metabolism; Metabolism; Microbiology; Operon; Probiotics; Prokaryotes; Raffinose - metabolism; Survival analysis; Trehalose - metabolism
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.12338

Summary Glycogen metabolism contributes to energy storage and various physiological functions in some prokaryotes, including colonization persistence. A role for glycogen metabolism is proposed on the survival and fitness of Lactobacillus acidophilus, a probiotic microbe, in the human gastrointestinal environment. L. acidophilus NCFM possesses a glycogen metabolism (glg) operon consisting of glgBCDAP‐amy‐pgm genes. Expression of the glg operon and glycogen accumulation were carbon source‐ and growth phase‐dependent, and were repressed by glucose. The highest intracellular glycogen content was observed in early log‐phase cells grown on trehalose, which was followed by a drastic decrease of glycogen content prior to entering stationary phase. In raffinose‐grown cells, however, glycogen accumulation gradually declined following early log phase and was maintained at stable levels throughout stationary phase. Raffinose also induced an overall higher temporal glg expression throughout growth compared with trehalose. Isogenic ΔglgA (glycogen synthase) and ΔglgB (glycogen‐branching enzyme) mutants are glycogen‐deficient and exhibited growth defects on raffinose. The latter observation suggests a reciprocal relationship between glycogen synthesis and raffinose metabolism. Deletion of glgB or glgP (glycogen phosphorylase) resulted in defective growth and increased bile sensitivity. The data indicate that glycogen metabolism is involved in growth maintenance, bile tolerance and complex carbohydrate utilization in L. acidophilus.