title: Appraising freeze-drying for storage of bacteria and their ready access in a rapid toxicity assessment assay.
abstract: Direct toxicity assessment (DTA) techniques seek to measure the impact of toxic chemicals on biological materials resident in the environment. This study features the use of freeze-dried bacterial cells in combination with a rapid DTA analyser, SciTOX. The effects of three factors-cryoprotectant type, bacterial strain, and storage temperature-were tested in order to validate the shelf life of the freeze-dried cells. Three freeze-dried Gram-negative bacterial strains, Acinetobacter calcoaceticus, Escherichia coli and Pseudomonas putida, were tested by using the bacteria in the SciTox(™) DTA assay and recording their responses to two standard toxicants: 2,4-dicholorophenol and 3,5-dichlorophenol. Each freeze-dried strain of bacteria was prepared in two forms--either pre-treatment with polyethylene glycol (PEG) or with sucrose/Tween 80--prior to storing at either 4 or -20 °C for three different storage periods (1, 2 or 3 months). While the sucrose/Tween 80 pre-treated freeze-dried cells exhibited better cell viability, we concluded that PEG was a more suitable cryoprotectant for the bacteria used in the DTA assay because of EC50 parity with fresh cell and zero-time freeze-dried cell assays. The results showed that freeze-dried cells, with appropriate materials and conditions, can give reproducible DTA results for up to 3 months. The availability of a biocomponent that can be activated by simple rehydration makes the deployment of this technology much easier for an end user.
authors: Lincoln University, PO Box 84, Lincoln, 7647, New Zealand, songw2@hotmail.com.
authors: Song
authors: S
authors: Wenfeng
authors: Ravi
authors: R
authors: Gooneratne
authors: Nicholas
authors: N
authors: Glithero
authors: Richard J
authors: RJ
authors: Weld
authors: Neil
authors: N
authors: Pasco
mesh_terms: D003451:Cryoprotective Agents / Q000633:toxicity*; D005612:Freeze Drying / Q000295:instrumentation / Q000379:methods*; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development*; D050296:Microbial Viability / Q000187:drug effects; D013696:Temperature
chemical_list: D003451:Cryoprotective Agents