Marine photosynthetic microorganisms are the largest primary producers of biomass in the marine environment. Their metabolic functions have developed during the evolutionary process for the adaptation of these microorganisms to diversified marine environments. With the development of marine biotechnology, photosynthetic microorganisms from unique and extreme marine environments are attracting attention as new biological resources. Considerable efforts are being made to isolate new strains and/or new species which can produce useful materials such as medicine and cosmetics. However, molecular approach has shown that microbial diversity in nature is far greater than that reflected in laboratory isolating microorganisms. Microorganisms in marine environments remain unexplored and unknown, since access to enormous reservoir of secondary metabolite producers has been hindered by the difficulty of culturing most of them. Recent molecular biotechnology developed to overcome the difficulties of culturing microorganisms involves extracting DNA directly from natural bacteria environments, cloning and expressing that DNA in surrogate expression hosts. Here, we introduce our research for screening and characterization of useful substances and products from marine photosynthetic microorganisms, mainly marine cyanobacteria as well as the genetic manipulation for the purpose of metabolic engineering in marine microorganisms with the application of marine genomes.
Production of useful materials by marine photosynthetic microorganisms
More than 600 strains of marine photosynthetic microorganisms mainly isolated from the Japanese coastal area were analyzed and tested for the production of useful substances and energy. Among the isolated microorganisms, several strains produced useful materials such as a UV-A absorbing substance (biopterin glucoside), a plant growth regulator, fatty acids, antimicrobial substance, polysaccharides etc.. We have also developed genetic engineered marine microorganisms for production of eicosapentaenoic acid and b-carotene, respectively.
The marine environment is remarkable diverse where it harbors a wide variety of organisms that have acquired novel metabolic functions and corresponding genes through evolutionary adaptation. Hence, there may be as many unique genes as there are species of organisms which indicates that marine organisms are potentially a treasure of gene resources.
Standard culturing techniques account for only 1% or less of the bacterial diversity in the environments. Surprisingly, over 99% of the remaining microflora is either still unknown or unculturable. With the recent introduction of new isolation and culturing techniques, several selected marine microorganisms are slowly being successfully isolated and cultured but these methods again are time consuming and is of low efficient. Therefore, we started to focus on the utilization of marine genome, especially from uncultured microorganisms in sponges and corals where total DNA from marine sponges were extracted and cloned into Escherichia coli. These E.coli transformants harboring the DNA fragments are then screened based on activity to exploit novel and potential useful genes. By taking the genetic approach, a more efficient and rapid method for the detection of these potential and useful genes from unculturable or unknown marine microorganisms can be achieved.