Molecular investigation of luxA gene to identify luminescent bacteria in Caspian sea

• Main Authors: Mojtaba Mohseni, Mohaddeseh Salehghamari
• Format: Article
• Language: fas
• Published: University of Isfahan 2014-01-01
• Series: Taxonomy and Biosystematics Journal
• Subjects: Luminous bacteria; Bioluminescence; Caspian sea; luxA
• Online Access: http://uijs.ui.ac.ir/tbj/browse.php?a_code=A-10-384-1&slc_lang=en&sid=1
• ISSN: 2008-8906; 2322-2190

Bioluminescence is a chemical reaction that causes light emission in the living organisms. Luminous bacteria are the most abundant bioluminescent organisms in natural environments. Biochemical tests are used for identification of luminous bacteria. However, molecular characterization of luxA gene could be suitable for investigation of luminescent bacteria due to differences in the sequences. In this study, the results of identification of luminescent bacteria were compared to the results of biochemical tests and PCR amplification of luxA using designed specific primers. In addition, thr results were confirmed by sequencing of 16S rDNA gene in the isolated luminescent bacteria. Samples of sea water were collected from several locations of southern shores of the Caspian sea. Luminous bacteria were isolated using specific cultures SWB and SWA. Then, morphological and physiological characterization of the isolates was identified. Specific primers for amplification of luxA were designed and synthesized after classification of luminescent bacteria according to the sequence of luxA. Polymerase chain reaction for luxA and 16S rDNA genes was performed after nucleic acid extraction of bacteria. Sequencing of 16S rDNA gene was obtained and then phylogenetic tree was constructed. Nine strains of luminescent bacteria were isolated from the Caspian sea. According to the results of biochemical tests, 5 strains belonged to the Photobacterium genus and 4 strains belonged to the Vibrio genus. Also, luxA PCR amplification of Aliivibrio, Photobacterium and Vibrio was done in order to specify primers luxA1, luxA2 and luxA3, respectively. In addition, BLAST subroutine of the 16S rDNA sequences revealed that the isolates were most similar to Photobacterium leiognathi with 99% homology. Results of isolates determination are according to the biochemical tests, molecular investigation of PCR luxA using specific primer and 16S rDNA analyses was correspondent. Therefore, the specific primer of luxA could be used for preliminary determination of luminescent bacteria.