Notice : Regarding Pseudozyma tsukubaensis JCM 10324T

December 14, 2015

We, the RIKEN BioResource Center, regret to inform you that a fungus Pseudozyma tsukubaensis JCM 10324T was contaminated by bacteria.

Pseudozyma tsukubaensis was described by H. Onishi in 1972, and its type strain was deposited to IFO*. JCM 10324T was obtained from IFO in 1998 and had been distributed since then. During the course of our quality tests, we recently detected the presence of bacteria in the culture of the ampoule.

As the strain forms various colony morphology on agar medium, contamination by the bacteria was unnoticed.

Sinece 2011, we have examined DNA sequences of the PCR-amplified rRNA gene of deposited strains and have compared the sequences with those provided by depositors of the strains to confirm the authenticity. We are now routinely performing examination of the strains that have not yet been confirmed their authenticity by rRNA gene sequencing. In the course of quality control efforts, we detected the contamination by bacteria in JCM 10324T.

Now JCM 10324T of which purity and authenticity have been confirmed by the quality tests including rRNA gene sequence analysis is available upon request.

For the strains that form various colony morphology on agar medium, we will perform more careful examination of the purity by observing morphology of well-grown isolated colonies on an agar plate. Furthermore, we will check the authenticity based on rRNA gene sequencing of culture obtained from several isolated colonies. We appreciate your support and understanding of our activities.

We informed users of JCM 10324T of this matter in detail with our sincere apology and asked for stopping its use.

If you have any question and concern on this matter, please feel free to contact us (

*IFO; Institute of Fermentation, Osaka, Japan.

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