Efficient insertional mutagenesis in Streptococcus thermophilus

Bacteria have always been considered ideal organisms for genetic analysis. While this is true for some model organisms, like Escherichia coli, Bacillu s subtilis and, more recently, Lactococcus lactis, genetic analysis of othe r organisms is often prevented by lack of valuable tools, like vectors, tra nsposons and methods for transformation, gene inactivation and random inser tional mutagenesis. This is the case of the moderately thermophilic bacteri um Streptococcus thermophilus, an organism that, in spite of its widespread use for food fermentations, is only poorly characterized. We report here a n insertional mutagenesis system that allows efficient random mutagenesis, easy characterization of the interrupted genes and construction of stable n ull mutations. This may become a powerful S. thermophilus tool for both gen etic analysis and construction of 'food-grade' mutants of this biotechnolog ically relevant microorganism. (C) 2000 Elsevier Science B.V. All rights re served.