Molecular detection of Candida krusei contamination in fruit juice using the citrate synthase gene cs1 and a potential role for this gene in the adaptive response to acetic acid.
OBJECTIVE
To develop a reverse transcription-polymerase chain reaction (RT-PCR) assay to detect viable Candida krusei contaminations and examine the potential role of the citrate synthase (cs1) gene in adaptation to acetic acid.


RESULTS
Fruit juice artificially contaminated with C. krusei cells was heat treated to inactivate the yeast cells, after which the improved ability of the RT-PCR over the PCR assay, through the amplification of the cs1 gene, to differentiate viable contaminations was shown. The sensitivity of the detection assay was 6 x 104 CFU ml-1. RT-PCR and densitometric analysis of the cs1 gene throughout the process of adaptation to acetic acid highlighted a potential role for the gene in the yeast's adaptive response.


CONCLUSIONS
The RT-PCR assay through the targeting of the cs1 gene proved to be a specific, sensitive and direct method for the identification of a C. krusei contamination in a food environment. The cs1 gene was shown to play a potential role in the adaptation of the culture to the weak-acid preservative acetic acid.


CONCLUSIONS
The development of a direct, sensitive and specific identification assay for C. krusei from a food environment and understanding the mechanism employed in adapting to a preservative challenge, represent important tools to the food industry in attempting to limit spoilage by this important food spoilage yeast.
Casey
G D
GD
Department of Microbiology, and National Food Biotechnology Centre, University College, Cork, Ireland.
Dobson
A D W
AD
D019342:Acetic Acid / Q000378:metabolism*; D000222:Adaptation, Physiological; D000595:Amino Acid Sequence / Q000235:genetics; D001628:Beverages / Q000382:microbiology*; D002175:Candida / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000235:genetics*; D002957:Citrus / Q000382:microbiology*; D003470:Culture Media; D005516:Food Microbiology; D015870:Gene Expression / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity
D003470:Culture Media; D002950:Citrate (si)-Synthase; D019342:Acetic Acid