Catabolism of N -Acetylneuraminic Acid, a Fitness Function of the Food-Borne Lactic Acid Bacterium Lactobacillus sakei, Involves Two Newly Characterized Proteins

Abstract

In silico analysis of the genome sequence of the meat-borne lactic acid bacterium (LAB) Lactobacillus sakei 23K has revealed a repertoire of potential functions related to the adaptation of this bacterium to the meat environment. Among these functions, the ability to use N-acetyl-neuraminic acid (NANA) as a carbon source could provide a competitive advantage for growth on meat in which this amino sugar is present. In this work, we proposed to analyze the functionality of a gene cluster encompassing nanTEAR and nanK (nanTEAR-nanK). We established that this cluster encoded a pathway allowing transport and early steps of the catabolism of NANA in this genome. We also demonstrated that this cluster was absent from the genome of other L. sakei strains that were shown to be unable to grow on NANA. Moreover, L. sakei 23K nanA, nanT, nanK, and nanE genes were able to complement Escherichia coli mutants. Construction of different mutants in L. sakei 23K ⌬nanR, ⌬nanT, and ⌬nanK and the double mutant L. sakei 23K ⌬(nanA-nanE) made it possible to show that all were impaired for growth on NANA. In addition, two genes located downstream from nanK, lsa1644 and lsa1645, are involved in the catabolism of sialic acid in L. sakei 23K, as a L. sakei 23K ⌬lsa1645 mutant was no longer able to grow on NANA. All these results demonstrate that the gene cluster nanTEAR-nanK-lsa1644-lsa1645 is indeed involved in the use of NANA as an energy source by L. sakei.

Metabolism of Sialic Acid by Bifidobacterium breve UCC2003

“…1) (29). An analogous pathway has been described in H. influenzae (73), Staphylococcus aureus (74), and L. sakei (32), yet it differs slightly from that found in Bt. fragilis.…”

“…1) (29). Other gut inhabitants, including the pathogen Vibrio cholerae (30) and the commensals Bacteroides fragilis and Lactobacillus sakei (31,32), have since been shown to utilize sialic acid as a carbon source.…”

Novel insights into the pathogenicity of epidemic Aeromonas hydrophila ST251 clones from comparative genomics

“…Briefly, sialic acid from the surrounding environment is transported into the cytoplasm by a symporter (NanT) through the inner membrane. A pyruvate group is first removed from the sialic acid with the help of N-acetylneuraminate lyase (NanA), after which N-acetylmannosamine is catalyzed by NanK, NanE, NagA and NagB, thereby generating fructose-6-phosphate, which may then enter the glycolysis metabolic pathway 18 . The pyruvate produced in this process is at a crossroads of central metabolic pathways, and it can yield acetyl-CoA to provide energy under aerobic conditions.…”

First Functional and Mutational Analysis of Group 3 N-Acetylneuraminate Lyases from Lactobacillus antri and Lactobacillus sakei 23K

“…It is this latter compound that enters the common pathways of amino sugar utilization [6]. This sialic acid catabolism process has been found in Clostridium perfringens [7], Escherichia coli [8], Pasteurella multocida [9], Haemophilus influenza [10], Bacteroides fragilis [11] and, recently, in Lactobacillus sakei 23K [12]. However, enzymes related with such catabolism have been described in more microorganisms, including Lactobacillus plantarum [13], Staphylococcus carnosus [14] and Bacteroides ovatus [15].…”