NDLI: Quantitative bioreduction assays for calibrating spore content and viability of commercial Bacillus thuringiensis insecticides

Content Provider	Springer Nature Link
Author	Seligy, V L Beggs, R W Rancourt, J M Tayabali, A F
Copyright Year	1997
Abstract	The redox dyes MTT (3-{4,5-dimethylthiazol-2-yl}-2,5-diphenyl tetrazolium bromide, thiazolyl blue) and XTT (sodium 3′- {1-[(phenylamino)-carbonyl]-3,4-tetrazolium}-bis{4-methoxy-6-nitro} benzene sulphonic acid hydrate) were used as dosimetry reporters in liquid (multi-well) and solid support (membrane) assays to estimate spore viability and content of commercial BT products derived from fermentation of Bacillus thuringiensis subsp kurstaki (Btk) and subsp israelensis (Bti). QC tests on five BT products were done using spore, protein and gene contents, and morphology (scanning electron microscopy) as indicators. Spore levels (6–40 × 109 colony forming units (CFU) ml−1) were approximately equivalent when based on International Units (IU) of potency. Spore viability was highly stable over a broad range of temperatures and pHs but germination and growth were restricted (optima: pH ≈ 7.5 and 37°C). Quantitative bioreduction activity (QBA) of MTT and XTT correlated with vegetative cell production. Depending on manipulation of pre-assay conditions, both dyes could discriminate doses from ∼2 to 109 spores (or 10−3 to 106 IU). Non-toxic effects of XTT and its formazan product enabled automated collection of data on growth and dose. Solid support assays also reliably estimated product dosage by in situ detection of CFU. With appropriate reference dilutions of microbe-containing products the QBA assays can provide high throughput QC monitoring of product comparisons and field release in aerial spray or water injection applications.
Starting Page	370
Ending Page	378
Page Count	9
File Format	PDF
ISSN	13675435
Journal	Journal of Industrial Microbiology and Biotechnology
Volume Number	18
Issue Number	6
e-ISSN	14765535
Language	English
Publisher	Nature Publishing Group
Publisher Date	1997-06-01
Publisher Place	London
Access Restriction	Subscribed
Content Type	Text
Resource Type	Article
Subject	Medicine Bioengineering Applied Microbiology and Biotechnology Biotechnology

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