Gene diversity of fructose metabolism in Fructobacillus

MOHAMED, F.; MOLINA, ROMINA; DE VUYST, LUC; RAYA, RAÚL R.; MOZZI, F

Egmond aan Zee

Simposio; 14th International Symposium on lactic Acid bacteria; 2023

The genus Fructobacillus is a group of fructophilic lactic acid bacteria reclassified from Leuconostoc that requires fructose or other external electron acceptors for growth. Fructose can be used as an external electron acceptor and reduced to mannitol by mannitol-2-dehydrogenase (MDH) or as carbon substrate through the phosphoketolase pathway by fructokinase (FK) and glucose-6-phosphate isomerase (GPI). In this work, the distribution of mdh, fk, and gpi genes and their genomic context in 13 Fructobacillus species was studied, as well as their gene expression in Fructobacillus sp. CRL 2054 and F. tropaeoli CRL 2034 when growing on fructose and/or glucose. The genomic region harboring the mdh gene was well-conserved in all genomes studied, with a gene for a fructose permease located downstream of the mdh gene. In contrast, two fk genes and three gpi genes were widely distributed within the genus. The genes fk1 and gpi1 were found in different parts of each genome, whereas fk2 and gpi2 were contiguously located in a presumptive operon (except for F. broussonetiae) with a variable genomic context. Additionally, cre repression sites were detected around some fk and gpi promoters. Differential gene expression studies showed a slight increase in mdh expression and a significative inhibition of fk and gpi expression when glucose was present compared to the expression values in the presence of fructose. The quantification of MDH, FK, and GPI enzymatic activities mostly supported these findings. The results obtained suggested catabolite repression of the fk and gpi genes by glucose for the Fructobacillus strains tested.