Mechanized systems for media dispensing, inoculation, and replication of microorganisms

Two instruments were developed to mechanize the handling of anaerobic microorganisms for microbial mutant isolation. The instruments automatically dispense liquid or agar medium to large and small 96-well platesand petridishes. Protocols were developed for inoculating different microorganisms, and calibration curves of number of areas or wells inoculated versus cell concentration were prepared for bacteria, yeast and fungi (spores). Experiments with yeast auxotrophic mutants and fungal spores showed that microbe inoculation follows Poisson statistics in distributing a single microorganism per inoculation point. The isolation and identification of Yarrowia lipolytica auxotrophic, morphological, and temperature-sensitive or tolerant mutants demonstrated the use of the instruments for microbial screening.