DNA fingerprinting differentiation between β-carotene hyperproducer strains of Dunaliella from around the world

Jorge Olmos,Rosalía Contreras,Jesus Paniagua-Michel,Leonel Ochoa

doi:10.1186/1746-1448-5-5

Abstract

BackgroundDunaliella salina is the most important species of the genus for β-carotene production. Several investigations have demonstrated that D. salina produces more than 10% dry weight of pigment and that the species grows in salt saturated lagoons. High plasticity in the green stage and the almost indistinguishable differences in the red phase make identification and differentiation of species and ecotypes very difficult and time consuming.ResultsIn this work, we applied our intron-sizing method to compare the 18S rDNA fingerprint between D. salina (CCAP 19/18), D. salina/bardawil (UTEX LB2538) and β-carotene hyperproducing strains of Dunaliella isolated from salt saturated lagoons in Baja, Mexico. All hyperproducer strains reached β-carotene levels of about 10 pg/cell. Optical microscopy did not allow to differentiate between these Dunaliella strains; however, 18S rDNA fingerprinting methodology allowed us to differentiate D. salina from D. salina/bardawil.ConclusionIn Baja Mexico we found D. salina and D. salina/bardawil species by using intron-sizing-method. The National Center for Biotechnology Information (NCBI) Dunaliella 18S rDNA gene sequences were analyzed with our methodology and extraordinary correlation was found with experimental results.

Highlights

Dunaliella salina is the most important species of the genus for β-carotene production
In this work, using intron-sizing method, we demonstrated that each hyperproducer species has an exclusive 18S rDNA fingerprint profile
D. salina BCO2 strain isolated in Mexico, presented the same 18S rDNA fingerprint [5,13] as did D. salina strain found in India by Raja and coworkers [14]

Summary

Introduction

Dunaliella salina is the most important species of the genus for β-carotene production. High plasticity in the green stage and the almost indistinguishable differences in the red phase make identification and differentiation of species and ecotypes very difficult and time consuming. Even today differentiation among halophilic and carotenogenic Dunaliella species in both green and red stages is difficult and time consuming. Some strains and species in culture collections are misnamed and have given rise to unnecessary strains and species names [1] This confusion of strains and species names makes comparison of results by different authors difficult [2]. D. salina and D. salina/ bardawil are the only reported β-carotene hyperproducer species of the genus (at least 10%), that grows in salt saturated lagoons [3]. Molecular identification provides a useful tool to distinguish between inter and intra-specific morphologically similar species [4,5] and mixed popula-

Methods

Results

Conclusion