Galactoside metabolism of L. plantarum, genes and their function: Regulation is the key

SILVESTRONI, A.; CONNES, C.; LEBLANC, J.G.; PIARD, J.-C.; SESMA, F.; SAVOY DE GIORI, G.

San Carlos de Bariloche

Congreso; XXXIX Reunion Anual, Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular (SAIB); 2003

Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular (SAIB)

In this study we present evidence that Lactobacillus plantarum has sugar metabolism functional genes but fail to metabolize these carbohydrates probably because they lack a crucial step of their metabolic pathway. In L. plantarum ATCC8014, a 7.5 Kb gene cluster involved in galactosides metabolism was identified and sequenced. Their relevant genes, an a–galactosidase (melA) and a-galactosides permease (rafP) were cloned and expressed in heterologous hosts showing enzymatic activity and lactose transport, not present in the native strain. Using the cloned genes, the a-Gal activity was evidenced in different E. coli strains and Lactococcus lactis, while functional lactose transport was demonstrated in E. coli. The metabolic capacity of two L. plantarum strains were compared as was the complete genome region encoding the melA and rafP genes at the nucleotide and amino-acid level. Only one of these strains was able to grow on melibiose and lactose. However, sequence comparison showed no relevant differences, suggesting that regulatory genes could be responsible for these divergent results. This comparison provides another good example that genes “are live and are functional” only in a specific genetic environment.