DETECTION OF EXTRACELLULAR PROTEASES FROM MICROORGANISMS ON AGAR PLATES

We present herein an improved assay for detecting the presence of extr acellular proteases from microorganisms on agar plates. Using differen t substrates (gelatin, BSA, hemoglobin) incorporated into the agar and varying the culture medium composition, we were able to detect proteo lytic activities from Pseudomonas aeruginosa, Micrococcus luteus and S erratia marcescens as well as the influence that these components disp layed in the expression of these enzymes. For all microorganisms teste d we found that in agar-BHI or yeast extract medium containing gelatin the sensitivity of proteinase detection was considerably greater than in BSA-agar or hemoglobin-agar. However, when BSA or hemoglobin were added to the culture medium, there was an increase in growth along wit h a marked reduction in the amount of proteinase production. In the ca se of M. luteus the incorporation of glycerol in BHI or yeast extract gelatin-agar induced protease liberation. Our results indicate that th e technique described here is of value for detecting extracellular pro teases directly in the culture medium, by means of a qualitative assay , simple, inexpensive, straightforward method to assess the presence o f the proteolytic activity of a given microorganism colony with great freedom in substrate selection.