Identification of Species and Subspecies of Lactic Acid Bacteria Present in Spanish Cheeses Type "Torta" by MALDI-TOF MS and pheS gene Analyses

Microorganisms. 2020 Feb 21;8(2):301. doi: 10.3390/microorganisms8020301.


Several artisanal cheeses are elaborated in European countries, being commonly curdled with rennets of animal origin. However, in some Spanish regions some cheeses of type "Torta" are elaborated using Cynara cardunculus L. rennets. Two of these cheeses, "Torta del Casar" and "Torta de Trujillo", are elaborated in Cáceres province with ewe's raw milk and matured over at least 60 days without starters. In this work, we identified the lactic acid bacteria present in these cheeses using MALDI-TOF MS and pheS gene analyses, which showed they belong to the species Lactobacillus curvatus, Lactobacillus diolivorans, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus rhamnosus, Lactococcus lactis and Leuconostoc mesenteroides. The pheS gene analysis also allowed the identification of the subspecies La. plantarum subsp. plantarum, La. paracasei subsp. paracasei and Le. mesenteroides subsp. jonggajibkimchii. Low similarity values were found in this gene for some currently accepted subspecies of Lc. lactis and for the two subspecies of La. plantarum, and values near to 100% for the subspecies of Le. mesenteroides and La. paracasei. These results, which were confirmed by the calculated ANIb and dDDH values of their whole genomes, showed the need to revise the taxonomic status of these species and their subspecies.

Keywords: MALDI-TOF MS; Spain; cheese; lactic acid bacteria; pheS gene; “Torta” type.