Thermusand the Pink Discoloration Defect in Cheese.
A DNA sequencing-based strategy was applied to study the microbiology of Continental-type cheeses with a pink discoloration defect. The basis for this phenomenon has remained elusive, despite decades of research. The bacterial composition of cheese containing the defect was compared to that of control cheese using 16S rRNA gene and shotgun metagenomic sequencing as well as quantitative PCR (qPCR). Throughout, it was apparent thatThermus, a carotenoid-producing genus, was present at higher levels in defect-associated cheeses than in control cheeses. Prompted by this finding and data confirming the pink discoloration to be associated with the presence of a carotenoid, a culture-based approach was employed, andThermus thermophiluswas successfully cultured from defect-containing cheeses. The link betweenThermusand the pinking phenomenon was then established through the cheese defect equivalent of Koch's postulates when the defect was recreated by the reintroduction of aT. thermophilusisolate to a test cheese during the manufacturing process.IMPORTANCEPink discoloration in cheese is a defect affecting many cheeses throughout the world, leading to significant financial loss for the dairy industry. Despite decades of research, the cause of this defect has remained elusive. The advent of high-throughput, next-generation sequencing has revolutionized the field of food microbiology and, with respect to this study, provided a means of testing a possible microbial basis for this defect. In this study, a combined 16S rRNA, whole-genome sequencing, and quantitative PCR approach was taken. This resulted in the identification ofThermus, a carotenoid-producing thermophile, in defect-associated cheeses and the recreation of the problem in cheeses to whichThermuswas added. This finding has the potential to lead to new strategies to eliminate this defect, and our method represents an approach that can be employed to investigate the role of microbes in other food defects of unknown origin.
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; School of Microbiology, University College Cork, Cork, Ireland.
Lisa
L
Quigley
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
Daniel J
DJ
O'Sullivan
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
David
D
Daly
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
Orla
O
O'Sullivan
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
Zuzana
Z
Burdikova
Tescan Orsay Holding, Brno, Czech Republic.
Rostislav
R
Vana
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
Tom P
TP
Beresford
APC Microbiome Institute, Cork, Ireland; College of Science, Engineering and Food Science, University College Cork, Cork, Ireland.
R Paul
RP
Ross
School of Microbiology, University College Cork, Cork, Ireland; APC Microbiome Institute, Cork, Ireland.
Gerald F
GF
Fitzgerald
School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
Paul L H
PL
McSweeney
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
Linda
L
Giblin
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
Jeremiah J
JJ
Sheehan
Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; APC Microbiome Institute, Cork, Ireland.
Paul D
PD
Cotter
Thermus; carotenoid; cheese; microbiota; pinking