title: Viability and physiological state transitions of Rhizopus oligosporus sporangiospores in tempe starter culture.
abstract: The viability and various physiological characteristics of individual sporangiospores of Rhizopus oligosporus in tempe starter cultures that had been stored for 8, 10, 16 and 30 months were examined by flow cytometry in combination with fluorescent dyes. Besides live, dead, and dormant spores we distinguished a category of sublethally damaged spores. Results indicated that the shelf-life of tempe starters was not limited by the death of spores, but by sublethal damage to spores as well as by dormancy which can be overcome by resuscitation, respiratory activation. During storage, the number of dormant and sublethally damaged spores increased: the longer the starter cultures were stored, the less dormant spores could still be activated. In contrast, the transition from sublethally damaged (spores that are not able to transform cFDA and emit green fluorescence except by activation treatment) to activated spores did not decrease with longer storage. However, after very long (30 months) storage, sublethally damaged spores could still be activated but could not germinate anymore. The shelf-life of spores in tempe starter is related to the physiological state of spores being sublethally damaged; a mechanism of physiological state transitions of R. oligosporus sporangiospores is proposed.
authors.affiliation: Biotechnology Research and Development Institute, Can Tho University, Can Tho, Vietnam.
authors.forename: Nguyen V
authors.initials: NV
authors.lastname: Thanh
authors.forename: Frans M
authors.initials: FM
authors.lastname: Rombouts
authors.forename: M J Rob
authors.initials: MJ
authors.lastname: Nout
mesh_terms: D003470:Culture Media; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D012233:Rhizopus / Q000502:physiology*; D013172:Spores, Fungal / Q000502:physiology*; D013194:Staining and Labeling; D013997:Time Factors
chemical_list: D003470:Culture Media; D005456:Fluorescent Dyes