1.1. What are cyanobacteria
Cyanobacteria are blue-green algae include a highly diverse group of prokaryotic microorganisms exhibiting oxygenic photosynthesis (Manage et al., 2009). The major cause for eutrophication is the occurrence of particular cyanobacteria blooms (Xu et al., 2011). Phylogenetically (as based on the small subunit ribosomal RNA-based tree of life) they are a coherent group within the domain Bacteria. Environmental conditions such as pH, temperature, light intensity and nutrient (nitrate and phosphate) content will persuade or enhance cyanobacteria population (Bownik, 2010). Cyanobacteria perform oxygenic photosynthesis just like eukaryotic green algae and higher plant, the chloroplasts of eukaryotic algae and higher plants have originated from endosymbiotic relationships with cyanobacteria (Raven and Allen, 2003). Their principal storage products are cyanophycean starch and glycogen together with specialized intracellular storage compounds like lipids, protein containing cyanophycean granules and polyphosphate bodies. Cyanobacteria are genetically highly diverse. (Whitton and Potts, 2007)
Various strains of cyanobacteria are known to produce intracellular (Endo-metabolites) and extracellular metabolites (Exo-metabolites) with diverse biological activities such as antibacterial, antifungal cytotoxic algaecide, immunosuppressive, and antiviral activities (Kundim et al, 2003). Exo-metabolites are isolated through the cell free extract such as a new brominated indole alkaloid, designated as bromoanaindolone, was isolated from the culture media of the cyanobacterium Anabaena constricta (Kundim et al., 2003).
Endo-metabolites have been isolated from cyanobacteria such as lyngbyabellin from Lyngbya majuscula (cytotoxic) pahayokolide A from Lyngbya semiplena (anticancer), hapalindole series (antituberculosis), venturamide A, B from Oscillatoria sp. (antimalarial), Antimalarial linear lipopeptides from marine cyanobacterium L. majuscula (antimalarial) (Kumar et al., 2012).
From 2001 to 2006, 128 cyanobacterial alkaloids were published with a wide structural diversity and variety of biological actions such as antifungal activity, cytotoxicity, sodium channel modulation, and inhibition of proteases (Tan, 2007; Harvey, 2008; Vasas et al., 2010). Majority of them were originated from the filamentous genera Lyngbya, Oscillatoria, and Symploca (Williams et al., 2001, 2004; Osswald et al, 2007; Grindberg et al., 2008).
1.2 Distribution and associations with other organisms
They are not only widespread in freshwater, marine and terrestrial ecosystems but also found in extreme habitats such as hot water springs, hyper saline localities, freezing environments and arid deserts (Fogg et al., 1973). They are also common inhabitants of polluted water bodies, drains and garbage dumps which are generally inhospitable to most other organisms. They often live in association with other organisms forming microbial mats, biofilms and benthic communities and such associations are the predominant and sometimes the only life forms found in certain extreme habitats (Fogg et al., 1973). Many important roles played by these simple prokaryotes justify referring to them as pioneers of planet Earth.
1.3. Morphology, taxonomy and molecular biology
Group :Algae (Eukaryotic)
Division: Chlorophyta (Green algae)
Class :Cyanophyceae or Myxophyceae (BlueGreen algae)
Characteristically all cyanobacteria have thin or thick gelatinous sheaths outside their cell walls, their thickness and sometimes their colour contribute to the final appearance of the organism (Kulasooriya, 2011). Mainly based on the variance of their peptidoglycan architecture, both envelope types show a characteristic difference when stained with crystal violet (Gram staining) (Beveridge, 1990). The peptidoglycan of Gram-positive bacteria is multilayered, thickness ranging from 20 to 40 nm and in Gram-negative bacteria, with their relatively thin sacculus of 2 to 6nm. (Glauner et al.,1988). The cyanobacteria-specific cell envelope features are consequence of specific adaptations during their (assumed) nearly 3.5 billion years of evolution.
Table 1. The principal groups of cyanobacteria (Adapted from: Singh et al., 2005).
Antimicrobial activity of Lyngbya sp.
The filamentous Cyanobacterial genus Lyngbya is being observed to be a rich source of toxic and generally bioactive metabolites. Only bioassay of active fraction were done to demonstrate that it has some antimicrobial action Many of the compound isolated from marine cyanobacteria have been appeared to have particular focuses in higher eukaryotic living beings (e.g., tubulin, actin) and have negligible or no antibacterial action. Four novel cyclic undecapeptides, lyngbyazothrins A, B, C , and D were isolated from the refined Lyngbya sp.( Kumar, 2014). The mixture of lyngbyazothrins A and B demonstrates just low antimicrobial action against Micrococcus flavus, while the mixture of lyngbyazothrins C and D were active against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi. Malyngolide is characteristic δ-lactones obtained from different strains of the marine cyanobacterium Lyngbya and characterized by a hydroxymethyl group and a long aliphatic chain connected to the δ-position of a sixmembered lactone ring. (Kumar, 2014).
Fig1: Figure 1 The structure of Lyngbyabellin A and B (Costa et al., 2012)
1.4 Important of the project
Antibiotics are used as chemotherapeutic drugs to control bacterial and fungal infectious disease. In general, isolation of bioactive compounds from cyanobacteria is done to discover new compounds. However pathogenic bacteria and fungi can obtain ability to survive even under over use of antibiotic and this is refers to as development of antibiotic or drug resistant genes.
Human and animal have been reported during last decades with evolved novel bacteria and fungi. Drug resistant of microorganism is another major problem associated with animal and human health. Unlimited and unregulated usage of antibacterial and antifungal drugs against causative microorganisms result evolving resistant of microorganisms against existence drugs. Thus drugs have been become resistant to novel bacteria and fungi disease during past decades. (Tiwari and Sharma., 2013).
The unregulated use of antimicrobial drugs in plant, animal, agriculture, veterinary medicine and human medicine are common practice and consequent treatment complication and increased healthcare costs and sometimes death. Many types of novel bacterial and fungal disease have been reported in human medication, animal, fish farm and agriculture which resistant for most of prevailing antibiotic in our country. Cyanobacteria have been recognized as a major source of active natural product with potential therapeutic application in the treatment of cancer and HIV (Singh et al., 2011). Discovering the new bioactive compound from cyanobacteria can be given strong solution for against increasing antibacterial and antifungal infections.