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Open Access Research article

The PTS transporters of Lactobacillus gasseri ATCC 33323

Alyssa L Francl13, Taksawan Thongaram1 and Michael J Miller12*

Author Affiliations

1 Department of Food Science and Human Nutrition, University of Illinois, 905 S. Goodwin Ave., Urbana, IL, USA

2 Division of Nutritional Sciences, University of Illinois, 905 S. Goodwin Ave., Urbana, IL, USA

3 Danisco, USA, Inc., 3329 Agriculture Drive, Madison, WI 53716, USA

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BMC Microbiology 2010, 10:77  doi:10.1186/1471-2180-10-77

Published: 12 March 2010

Abstract

Background

Lactobacilli can utilize a variety of carbohydrates which reflects the nutrient availability in their respective environments. A common lactobacilli in the human gastrointestinal tract, Lactobacillus gasseri, was selected for further study. The currently available annotation of the L. gasseri ATCC 33323 genome describes numerous putative genes involved in carbohydrate utilization, yet the specific functions of many of these genes remain unknown.

Results

An enzyme I (EI) knockout strain revealed that a functional phosphotransferase transporter system (PTS) is required to ferment at least 15 carbohydrates. Analysis of the L. gasseri ATCC 33323 genome identified fifteen complete (containing all of the necessary subunits) PTS transporters. Transcript expression profiles in response to various carbohydrates (glucose, mannose, fructose, sucrose and cellobiose) were analyzed for the fifteen complete PTS transporters in L. gasseri. PTS 20 was induced 27 fold in the presence of sucrose and PTS 15 was induced 139 fold in the presence of cellobiose. No PTS transporter was induced by glucose, fructose or mannose. Insertional inactivation of PTS 15 and PTS 20 significantly impaired growth on cellobiose and sucrose, respectively. As predicted by bioinformatics, insertional inactivation of PTS 21 confirmed its role in mannose utilization.

Conclusions

The experiments revealed the extensive contribution of PTS transporters to carbohydrate utilization by L. gasseri ATCC 33323 and the general inadequacy of the annotated sugar specificity of lactobacilli PTS transporters.