Quantitative Analysis of Histidine Decarboxylase Gene (hdcA) Transcription and Histamine Production by Streptococcus thermophilus PRI60 under Conditions Relevant to Cheese Making

Abstract

This study evaluated the influence of parameters relevant for cheese making on histamine formation by Streptococcus thermophilus. Strains possessing a histidine decarboxylase (hdcA) gene represented 6% of the dairy isolates screened. The most histaminogenic, S. thermophilus PRI60, exhibited in skim milk a high basal level of expression of hdcA, upregulation in the presence of free histidine and salt, and repression after thermization. HdcA activity persisted in cell extracts, indicating that histamine might accumulate after cell lysis in cheese.

Lactobacillus reuteri-Specific Immunoregulatory Gene rsiR Modulates Histamine Production and Immunomodulation by Lactobacillus reuteri

“…Increased histamine production and increased expression of the hdc gene cluster in the presence of histidine have been described in other histaminogenic Gram-positive bacteria, such as Lactobacillus hilgardii ISE 5211 (57), L. hilgardii 464, Pediococcus parvulus P270, Oenococcus oeni 4042 (16), and Streptococcus thermophilus PRI60 (12). However, the regulatory mechanisms affecting hdc gene expression in Gram-positive bacteria are currently unknown.…”

“…strain 30a), an isolate from a horse's stomach (11). Subsequently, several other Lactobacillus species were found to contain a functional hdc gene cluster, which consists of the histi-dine decarboxylase pyruvoyl type (hdcA), a putative helper protein (hdcB), and a histidine/histamine antiporter (hdcP) (12). The hdcA and hdcB genes are cotranscribed as a single bicistronic mRNA, and hdcA and hdcB expression is coregulated under the P hdcAB promoter, which lies directly upstream of hdcA (13,14).…”

Improved Acid Stress Survival of Lactococcus lactis Expressing the Histidine Decarboxylation Pathway of Streptococcus thermophilus CHCC1524

“…Typically, in Gram-positives, the presence of gene clusters encoding amino acid decarboxylation pathways is strain-specific rather than species-specific, indicating that the clusters have been spread through horizontal gene transfer (14,16,18,26). The physiological benefit of the newly acquired pathway for the receiving host, essential for maintenance of the gene cluster, will depend on the metabolic capacity and robustness of the host and the habitat in which the host must survive.…”

“…Once a function is established, further evolution of the genes and gene cluster will optimize the integration of the pathway in the host organism. Here, we mimic the horizontal gene transfer event, the first step in the successful acquisition of new functionality in this evolutionary process, by introducing the histidine decarboxylation pathway of the yoghurt bacterium Streptococcus thermophilus CHCC1524 (16,26) in the cheese bacterium Lactococcus lactis and analyzing the beneficial effects for the receiving organism. The gene cluster encoding the pathway consists of the histidine decarboxylase gene hdcA, the histidine/ histamine exchanger gene hdcP, and the HdcA maturation factor gene hdcB and is transcribed as one mRNA, thus forming one operon (16,26).…”

“…Here, we mimic the horizontal gene transfer event, the first step in the successful acquisition of new functionality in this evolutionary process, by introducing the histidine decarboxylation pathway of the yoghurt bacterium Streptococcus thermophilus CHCC1524 (16,26) in the cheese bacterium Lactococcus lactis and analyzing the beneficial effects for the receiving organism. The gene cluster encoding the pathway consists of the histidine decarboxylase gene hdcA, the histidine/ histamine exchanger gene hdcP, and the HdcA maturation factor gene hdcB and is transcribed as one mRNA, thus forming one operon (16,26). Recently, the complete hdcA-hdcP-hdcB operon was functionally expressed in L. lactis as part of a study demonstrating the function of HdcB in the cleavage of the HdcA proenzyme, an essential step in the formation of the pyruvoyl group cofactor (27,28).…”