Antimicrobial Activity of Extremely Halophilic Archaea Isolated from Southern Thai Salt-Fermented Products and Solar Saltern of Pattani, Thailand

Abstract

This research aimed to study the diversity and antimicrobial activity of culturable haloarchaea in soil samples of solar saltern in Pattani Province, Thailand and Southern Thai salt-fermented food. Seventy-seven extremely haloarchaea were isolated on Halophilic medium agar containing 25% NaCl at 37°C for 7-21 days. They were grouped by Amplified Ribosomal DNA Restriction Analysis (ARDRA) with two restriction enzymes, RsaI and HindIII. The ARDRA patterns illustrated 6 different Operation Taxonomic Units (OTUs). Partial 16S rRNA gene sequences (938 bp) of the representative of each OTUs were aligned with the GenBank database. The results showed that the representatives of OTU1, OTU2, OTU3, OTU4, OTU5, and OTU6 had 99-100% similarity to Halobacterium salinarum, 99-100% similarity to Halostagnicola larsenii, 99% similarity to Natronococcus sp., 99-100% similarity to Haloferax alexandrinus, 99-100% similarity to Natrialba sp. and 97% similarity to Halococcus sp., respectively. The antimicrobial activity testing of the 17 isolated haloarchaeal strains from solar saltern was performed against 5 tested strains of Hbt. salinarum and 1 strain of Natrialba sp. were isolated from fermented food. Seven (41.2%) were candidate halocin-producing strains. In addition, no phage activity was observed. The 14-day fermentation broth of Natronococcus sp. SS13 showed the highest antimicrobial activity against Hbt. salinarum PK08, BD07 and BD09 (>5,120 AU/ml).