P2: Phenotypic and genotypic analysis of the primary metabolic pathway in Lactobacillus strains

In microorganisms, biosynthetic pathways of the primary metabolism have been established with model microorganisms such as Escherichia coli. For a long time, the biosynthetic routes so far established were believed to be common among all microorganisms. However, recent genome sequencings revealed that some microorganisms do not possess the orthologs of the known pathways. This fact was one of triggers to find new pathways such as 2-C-methyl-D-erythritol 4-phosphate and futalosine pathways. We searched a new pathway in Lactobacillus strains. Lactobacillus strains had been shown to have mutations in the many primary metabolic pathways and require rich media containing various amino acids and nucleobases for their growth. Recently, the detailed phenotypic and genotypic analyses of the primary metabolic pathway in Lactobacillus strains begun after the whole genome sequences of them were determined. All of these analyses, however, were performed with the database of known biosynthetic pathways. Considering that the many Lactobacillus strains do not possess a part of orthologs in the known pathways and that the genome sizes of them are relatively large, we expected the presence on an alternative primary metabolism pathway in Lactobacillus strains. We performed analyses of the phenotypic and genotypic relationships focusing on biosyntheses of amino acids, purine/pyrimidines, and cofactors in three Lactobacillus strains and found that at least Lactobacillus fermentum IFO 3956 perhaps synthesized para-aminobenzoate, an intermediate of folic acid biosynthesis, by an alternative pathway.