Agmatine deiminase pathway genes in Lactobacillus brevis are linked to the tirosine decarboxylation operon in a putative acid resistance locus

LUCAS, PM; BLANCATO, VS; CLAISSE, O; MAGNI, C; LOLKEMA, J; LONVAUD-FUNEL, A

MICROBIOLOGY

SGM

Año: 2007 vol. 153 p. 2221 - 2230

0026-2617

In lactic acid bacteria (LAB), amino acids and their derivatives may be converted into amine-containing compounds designated biogenic amines, in pathways providing metabolic energy and/or acid resistance to the bacteria. In a previous study, a pathway converting tyrosine to tyramine was detected in Lactobacillus brevis and a fragment of a gene possibly involved in the production of another biogenic amine, putrescine, from agmatine, was detected in the same locus. The present study was carried out to determine if Lb. brevis actually harbours two biogenic amine-producing pathways in the same locus and to investigate the occurrence of the two gene clusters in other bacteria. Sequencing of the DNA locus in Lb. brevis revealed a cluster of six genes that are related to previously reported genes of agmatine deiminase pathways but with marked differences such as two genes encoding putative agmatine deiminases rather than one. Heterologous expression of encoded enzymes confirmed the presence of at least one activeagmatine deiminase and one amino acid transporter that efficiently exchanged agmatine andputrescine. It was concluded that the Lb. brevis gene cluster encodes a functional and highlyspecific agmatine deiminase pathway. Screening of a collection of 197 LAB disclosed the samegenes in 36 strains from six different species, and almost all the positive bacteria also containedthe tyrosine catabolic pathway genes in the same locus. These results support the hypothesis thatthe agmatine deiminase and tyrosine catabolic pathways belong to a genomic region that providesacid resistance and that is exchanged horizontally as a whole between LAB.