Assessment of Biological Activity in the Marine Cyanobacterial Species from Coastal and Nearshore Environments

Abstract

Cyanobacteria are known to produce a multitude of bioactive compounds. Some of these novel compounds are toxic for domestic and wild animals, birds, fish and even human beings, whereas some metabolites are cytotoxic and show promise as killers of algae, bacteria and fungi. Some may even serve as agents for attacking tumor cells and viruses. Some of these novel compounds are toxic for domestic and wild animals, birds, fish and even human beings ( Martin 2001, scholin et al. 2000, Moron et al. 1997, Falconer 1996). Interestingly, some metabolites are cytotoxic and show promise as a killers of algae, bacteria and fungi and even serve as agents for attacking tumour cells and viruses. Most of the research that has been carried out so far deals largely the toxicity and biologically active compounds from fresh water cyanobacteria. However emerging reports on marine organisms indicate that marine ecosystem harbours a whole world of organisms that are capable of producing a range of fine chemicals. Evident from the literature is the fact that there has been no study on the biochemical or psychological behaviour of marine cyanobacteria inhabiting coastal areas along the coast of Pakistan. This paucity of data together with the importance of cyanobacteria in producing the new and unique substances had been instrumental in the proposal of the project under report. The objective of the project was to describe the distribution and biodiversity of marine cyanobacteria and to screen the potential of some of the isolates for production of biologically active substances. The project under report was able to demonstrate a high biological diversity of cyanobacteria in various niches if Karachi coast. It was also possible to sample and describe two blooms occurred in the Manora channel and Korangi creek. A number of cyanobacterial species were isolated from the field material collected from intertidal zone and coastal blooms. In total 15 isolates and two mixed cultures (from bloom) of the cyanobacteria were screened for the possible biological activity and toxicity. Crude extracts from all isolates and mixed cultures were tested for anti-microbial activity (against bacteria and fungi), haemolytic activity, effect on coagulation of blood, and lethality using rat bioassay. The present study forms a baseline data and more detailed future research is likely to develop on the toxins and other bioactive compounds from marine cyanobacteria. In summary, it may be noted that the screening of marine cyanobacteria species occurring along Karachi coast, for biological activities showed promising results. The isolated species and the mixed cultures displayed great capabilities for the production of biologically active compounds. One of the outcomes of this project is the data on the cyanobacterial distribution and diversity along the coast of Pakistan. The taxonomic inventory of these organisms is a useful addition to the pool of knowledge of this group of organisms neglected in the past. This study forms baseline information on the toxins and other bioactive compounds from marine cyanobacteria, and more detailed future research is likely to develop. The present report may, therefore, be considered a first step towards more elaborate studies on cyanobacterial natural products.