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Pathogens form biofilms to increase their resistance to environmental stress and antibacterial compounds. The rhizosphere is a rich source of microorganisms producing industrially important compounds including those with antimicrobial and biofilm inhibitory activities. Four isolates from soil collected from Taguig City, Philippines, were subjected to phenotypic and genotypic characterization, screening for protease production, and biofilm inhibition assays. Colony morphology and microscopic analyses indicated the isolates were putative Bacillus species. Upon DNA extraction, 16S rRNA gene was amplified, and based on their sequences, the isolates were confirmed to be Bacillus spp. Isolate AHP was B. cereus, isolate DJA was Priestia megaterium, formerly known as B. megaterium and isolates SJS and SKA were Bacillus spp.--all of which produced protease. Although the cell-free supernatants (CFS) of the isolates did not inhibit the growth of Staphylococcus aureus 1258, Citrobacter freundii ATCC24864, Salmonella Typhimurium ATCC13311, Escherichia coli ATCC11229, and E. coli O157:H7, biofilm formation of S. aureus was inhibited by all CFS, with B. cereus AHP showing the highest biofilm inhibition at 46%, followed by Bacillus sp. SKA (39%), P. megaterium DJA (36%), and Bacillus sp. SJS (31%). Even though further studies are warranted, the bioactivities of these isolates indicate potential use for pharmaceutical purposes due to their ability to produce protease and inhibition of biofilm formation of a common bacterial pathogen. [ABSTRACT FROM AUTHOR]

Amylase and protease are two of the most commonly used enzymes in the pharmaceutical industry. Particularly, Bacillus spp. is widely regarded as a "factory" of these enzymes. In this study, a total of 40 isolates were collected from four soil samples from different metropolitan sites namely, near Chemicals and Energy Division (CED), and National Metrology Laboratory (NML) oil tankers parking lot inside the Department of Science and Technology (DOST) Compound in Taguig City, and two metropolitan-volcanic sites in Clark Freeport Zone, Pampanga (CRK1, CRK2). Of these, 33 isolates were deemed putative Bacillus spp. via phenotypic assays and were screened for the production of amylase and protease. Results showed that 26 of the screened isolates were able to produce protease and 12 were positive for amylase production. Molecular identification revealed that the enzyme-producing isolates were Bacillus spp., B. cereus, B. aryabhattai, B. amyloliquefaciens, B. firmus, B. velezensis, and Fictibacillus sp. No isolate was able to produce amylase alone. These results show the potential of Bacillus spp. from metropolitan soil as sources of pharmaceutically-important enzymes. [ABSTRACT FROM AUTHOR]