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Highlight 1 November 2007: The micro Petri dish, a million-well chip for the culture and high-throughput screening of micro-organisms
More than one million Petri dishes on a single chip not larger than the size of a postage stamp. The chip has been developed in our group in close cooperation with the Top Institute Food & Nutrition and NIZO food research in Wageningen. The results have reached the cover (PNAS) of the authoritative journal Proceedings of the National Academy of Sciences (PNAS) of 13th November 2007.
On this chip more than one million cultures can be grown in parallel which opens up a wide range of uses from diagnosis of infection to the improvement of industrial bacteria. The chip that has the potential to meet the automation and miniaturisation needs of modern microbiology. The ‘micro Petri dish’ allows growth assays to catch up with other high-throughput technologies in the life sciences.
The innovation is in the micro-engineering of a unique porous ceramic to create millions of wells that serve as growth areas for micro-organisms. The micron-scale wells of the chip can be regarded as an array of millions of “micro Petri dishes”, where bacteria or yeasts are efficiently supplied with nutrients from below through a porous membrane. By using this chip, assays for the detection and growth of micro-organisms will become faster and cheaper whilst it permits larger screening operations for improved industrial strains than have been possible to date.
Fig. 1. Images of materials, growth compartments, and microbial culture on chips.
(A) SEM of aluminumoxide showing pores on average 200nm diameter. (B) Transmission light microscopy
of hundreds of 20x20μm compartments viewed from above. (C) SEM of 7x7 μm compartments from above at a 30° angle. (D) Culture of L. plantarum in six compartments of the same dimensions as C stained with a fluorogenic dye (Syto 9) after growth and imaged from above. (E) Detection of β-galactosidase activity using the fluorogenic substrate FDG, from E. coli containing plasmid pUC18 grown in a 20x20μm compartment. (F) As in E with one plasmid-containing micro colony, viewed at lower magnification. (G) View of 20x20μm format chip with one area supporting a GFP-expressing strain of E. coli in a background of non-fluorescent cells. (H) Previously uncultivated oligotrophic bacterium related to Dechloromonas sp. labeled by FDP metabolism and grown in a 20x20μm compartment supplied by Rhine water, before recovery and identification by PCR.
