INTERNATIONAL RESEARCH JOURNAL OF MODERNIZATION IN ENGINEERING TECHNOLOGY AND SCIENCE

Abstract

ABSTRACT LICHENS ARE SYMBIOTIC ORGANISM COMPOSED OF FUNGUS AND AN ALGAE.THEY PRODUCE CHARACTERIC SECONDARY METABOLITES LICHEN SUBSTANCE THAT SELDOM OCCUR IN OTHER ORGANISMS. LICHEN MYCOBIONTS AS OTHER FUNGI COULD THEREFORE BE A POTENTIAL SOURCE IN THE SEARCH FOR PHARMACEUTICAL USEFUL CHEMICALS.LICHEN PRODUCES UNIQUE METABOLITES THAT HAS VARIOUS EFFECT AS ANTIMICROBIAL AND ANTIFUNGAL AGENTS LICHENS AND THEIR METABOLITES HAVE MANY BIOLOGICAL ACTIVITIES SUCH AS ANTIMICROBIAL, ANTIVIRAL, ANTI-OXIDANT, ANTI-INFLAMMATORY AND ANALGESIC ACTIVITY. THE SPOT TEST IS DONE TO IDENTIFY THE LICHENS AND THE EXTRACTIONS ARE ANALYSED FOR THE PHYTOCHEMICAL SCREENINGS THEIR ANTIBACTERIAL AND ANTIFUNGAL PROPERTIES ARE DESCRIBED BY PLATING TECHNIQUES.KEYWORDS: LICHEN ISOLATION-SPOT TEST-SECONDARY METABOLITES -BIOPOTENTIAL ACTIVITY ANTIMICROBIAL AGENTINTRODUCTIONLichens are symbiotic organisms composed of fungus and an algae.They produce characteristic secondary metabolites 'lichen substancesthat seldom occur in other organisms. Lichens are composed of fungal partner mycobiont and one or more photosynthetic partner photobiont. The photosynthetic partner is generally algae or cyanobacteria.There are about 13,500 species of lichen on the earth. In lichen ,the mycobiont produces a thallus,which houses the photobiont .There are three major morphological types of thalli Foliose, Crustose and fruticose. Lichens can survive severe conditions because they can withstand drying.The lack of water interupts photosynthesis.In this suspended state ,some lichens are able to great extremes in temperature. Lichens produce an unique variety of extracellular secondary metabolites known as lichen substances.These compounds exist within the thalli either in an amorphous form or as crystals. A lichen absorbs most of its mineral nutrients from the air and rainfall. Pollution in the atmosphere can be especially dangerous to lichens because they retain, and can accumulate, deadly amounts of heavy metals, sulfur, radioactive elements, NO2, and ozone. Sulfur dioxide (SO2) is especially lethal to lichens because it lowers pH and deteriorates chlorophyll, which causes photosynthesis to cease. Anti-sulfur dioxide legislation in the last 25 years is allowing lichens to return to formerly polluted areas. Lichens have been used to monitor the amount of pollutants in an environment. This is done by observing the condition of lichens as well as their chemical composition. Lichenometry is a technique used in dating rock surfaces on which certain lichens grow by means of their rate of growth. Lichens produce many secondary compounds which play an important role in distiguishing species in the laboratory. A practical use for these same compounds is seen in medicine as well as natural dyes and as a component in perfume. In nature these compounds may serve as a defense against herbivores and may also help break down rock substrates. Lichens colonize places that have not had any previous growth, such as rocks. Lichens having cyanobacteria as a photobiont provide fixed nitrogen to their environment.Ecologically, they are also important in providing food and shelter to wildlife including deer, moose, and elk, as well as certain species of squirrels, mice, and bats. Lichens contribute to the background diversity of the natural landscape and can be appreciated by all, even if only subliminally to the untrained eye. Lichen mycobionts as the fungi, could therefore be a potential source in the search for pharmaceutical useful chemical .Lichens and their metabolites have many biological activities such as antimicrobial ,antiviral, anti-oxidant, anti-inflammatory and analgesic activity.Inspite of the wide spectrum of biological activities shown by the lichens,they have long been neglected by mycologists and overlooked by pharmaceutical industry because if its slow growth in nature and difficulties in the artificial cultivation of the organisms.Hence the large-scale industrial production of the lichen metabolites have never been accomplished.Lichen extracts and their metabolites have been widely studied for their antimicrobial properties.but their anti biofilm potential is still poorly explore.Some of these studies ,particularly on cultured mycobionts, tired to improve the culture to trigger and enhance the synthesis of secondary metabolites,to reveal the factors involved in this process,to understand the role of each of the partners in the synthesis of the lichens substances,or to find sources of therapeutic an gents.In some cases the asymbiotic fungal strains synthesized the same secondary metabolites as the natural lichen. All or only some of them .Other examples showed that some mycobionts produced secondary metabolites different from those present as major compounds in the symbiotic state, including novel molecules such as the graphislactones, graphenone and xanthones.The primary intracellular metabolites include proteins , amino acids, cartenoids, polysaccharides and vitamins are generally soluble in water and can be easily isolated from the lichens by boiling water.Some of the primary metabolites are produced by fungi and some by algae. Most of these metabolites are non specific and also may occur in free living fungi and some algae.In general,the amount pf nitrogen compounds is between 1.6% and 11.4% dry weight of the lichen thallus among vitamins.Lichen contains ascorbic acid, biotin , -tocophenol, nicotinic acid, pantothenic acid. Riboflavin ,thiamine and folic acid.Vitamins were identified as metabolic products which biosynthesis algae.While more than 800 secondary metabolites are known from lichens.All of the secondary substances in in lichens are of fungal origin.These substances are the crystals deposited on the surface if the hyphae, which are poorly soluble in water,and usually can be isolated from the lichens by organic solvent.Morphology: Father of lichenology is Erick Acharius, who have started the study of lichen morphology.Study on lichen structures began over a century ago when the light microscope became readily available.The accurate account of the internal structure of several lichens is presented by Schwendener in 1860. Different parameters are needed to lichen identification by morphologyVegetative part: The characterization of lichens by variety of vegetative structures rhizines, tomentum,cilia are also known as in fungi. But soredia to lichenized fungi. Pycnidia and conidia are non-symbiotic reproduction parts.Growth form: Lichen morphology is usually determined by the organization of fungal filaments.Their vegetative part is known as Thallus. The most visually prominent part of the lichen was thallus,They are grouped by thallus type as crustose (crusts that are strongly attached to substrate), squamulose (having scale like lobes), Foliose(leafy structure), Umbilicate(attached t single point), Fruticose (shrubby), Gelatnous (its mucusy-gelly type and its photobiont is cyanobacterium) and Leprose (powdery). Macro and micro lichens are differ from their growth form will be the despite of wide diversity ,but they all have similar outer surface , where it comes in contact with the environment,are packed tightly together to form the intensity of light ,which may damage the algal cells.The algal cells are distributed just below the cortex in a layer. Medulla is below algal layerSexual reproduction It depends upon sexual life cycle of Ascomycota and according to different projections on the surface of thallus for sexual reproduction , lichens can be identified.These non vegetative bodies includes Mazaedia and Apothecia Lecanorine, Lecideine, Biatorine, Zeorin and perithecia, Hysterothecia, pseudothecia.

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