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

Yong Jun Goh,Todd R. Klaenhammer

doi:10.1111/mmi.12338

Abstract

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.

Highlights

Lactobacillus acidophilus is one of the most recognized and widely used probiotic microbes in the commercialAccepted 20 July, 2013. *For correspondence
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 operon consisting of glgBCDAP-amy-pgm genes

Summary

Introduction

Lactobacillus acidophilus is one of the most recognized and widely used probiotic microbes in the commercialAccepted 20 July, 2013. *For correspondence. Production of yogurt and dietary supplements (Sanders and Klaenhammer, 2001). It belongs to a phylogenetically diverse genus that includes species found naturally in milk, plants, meats and the mucosal surfaces [oral, gastrointestinal (GI) tract and reproductive tracts] of mammalian hosts, as well as species that were domesticated for centuries, which altogether represent a group of microorganisms that are of economic importance for the manufacturing of fermented foods and as probiotic adjuncts in cultured dairy products. The probiotic functionality of L. acidophilus has been well documented, including the alleviation of lactose intolerance (Kim and Gilliland, 1983), mitigation of cold and influenza-like symptoms in children (Leyer et al, 2009), the modulation of immune cell functions (Konstantinov et al, 2008) and the alleviation of abdominal pain via modulation of the visceral pain perception (Rousseaux et al, 2007). Extensive studies are ongoing to elucidate in vivo mechanisms involved in the stress adaptation and host–microbe interactions of L. acidophilus in order to enhance its biodelivery and fitness in the host GI environment

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