Molecular identification of endophytic bacterium DBA2 isolated from the leaf of binahong (Anredera cordifolia (Ten.) Steenis) and its antagonistic activity against bacteria associated with dental caries

Abstract

Binahong plants (Anredera cordifolia (Ten.) Steenis) are known to contain secondary metabolites which have important biological properties. The current study focused on the endophytic bacteria which lives in the leaves of A. cordifolia (Ten.) Steenis. The aim of this study is to isolate and identify the endophytic bacteria which can produce antibacterial metabolites from the leaves of A. cordifolia (Ten.) Steenis. Two isolates, DBA1 and DBA2 were isolated and purified from the leaves of A. cordifolia. These isolates were subjected to the screening for their antagonistic activity against the bacteria associated with dental caries, which are Streptococcus mutans and Lactobacillus acidophilus using the disk-diffusion method. The strain of DBA2 exhibited the largest diameter of inhibition zone against both S. mutans (31,17 mm) and L. acidophilus (35,57 mm). While DBA1 exhibited the diameter of inhibition zone of 23,47 mm and 25,87 mm against S. mutans and L. acidophilus, as respectively. The strain of DBA2 was then subjected for molecular identification. The genomic DNA of DBA2 was extracted with the Geno Plus™ Genomic DNA Extraction Miniprep System and molecular identification was performed by PCR amplification and sequencing of the 16S rRNA gene. The amplicons were then purified and sequenced, before the 16S rRNA gene sequences were analysed by a Basic Local Alignment Search Tool (BLAST) search against the National Centre Biotechnology Information (NCBI) database. The endophytic bacterial strain DBA2 from the leaves of A. cordifolia was identified to be closely related to Bacillus sp., and the top match from the database search revealed a similarity value of 100% with the reference Bacillus sp. strain x20. Future studies are required to analyse the bioactive compounds of strain DBA2, which can be considered as a potential source for the new antibacterial drugs for the dental caries treatment.