Specific and sensitive detection of Alcaligenes species from an agricultural environment

A quantitative real-time PCR assay to specifically detect and quantify the genus Alcaligenes in samples from the agricultural environment, such as vegetables and farming soils, was developed. The minimum detection sensitivity was 106 fg of pure culture DNA, corresponding to DNA extracted from two cells of Alcaligenes faecalis. To evaluate the detection limit of A. faecalis, serially diluted genomic DNA from this organism was mixed with DNA extracted from soil and vegetables and then a standard curve was constructed. It was found that Alcaligenes species are present in the plant phytosphere at levels 10(2)-10(4) times lower than those in soil. The approach presented here will be useful for tracking or quantifying species of the genus Alcaligenes in the agricultural environment.