SUMMARY
Bacterial activity, mainly Pseudomonas spp. plays a vital role in the fruiting process of white button mushroom, hence a rapid procedure to identify these bacteria is crucial. In the current study, the validity of commercial identification system, Analytical profile index API 20E to identify Pseudomonas isolates from mushroom casing soil were assessed. Using API strips fifty bacterial isolates from a selective medium (King B medium) were examined, all isolates were belonged to the genus Pseudomonas according to API 20E identification systems. However, only 74% of Pseudomonas bacteria were identified to species level. The molecular identification using 16S rRNA gene was used as a reference tool to identify bacteria at the species level. The results show that the accuracy of the system to classify florescent Pseudomonas to species level was 60%. This was species dependant, and the system accuracy were 100%, 87.5%, 81.3% and 63% in identifying P. aeruginosa, P. putida, P. fluorescens and P. tolaasii respectively. Our finding indicates that although the classification of the Pseudomonas genus with API 20E system is useful, but it is not enough to distinguish these bacteria to species level, genomic studies are necessary to confirm the exact taxonomic position of Pseudomonas spp.