Isolation and identification of biodeteriorating phototrophs from Pasargadae

Pasargadae set of ancient structures remaining from the Achaemenid impire are located in Fars province, Iran. Tomb of Cyrus the Great, which is made of limestone placed in the southern part of this area. Like any other stone, the building has been influenced by physico-chemical and biological factors. Biodeterioration of materials is an irreversible process which materials and equipment under the influence of the micro and macroorganisms are degraded and causes massive economic losses. Almost all microorganisms are in the destructive biofilm form on the external surfaces of the monuments and phototrophic microorganisms preparing suitable condition for the growth of other organisms. The effects of these organisms are particularly important in the context of biodeterioration. BG-11, MKM, BBM medium was used for isolation of phototrophs. Stereomicroscope and scanning electron microscope (SEM) was done to observe the biological structures and the pattern of deteriorating alteration on the surface of the substratum. To identify the phototrophic populations, cultivation method was used. During this study, several species of microorganisms, including algae and cyanobacteria in biofilm structure, were isolated. Most of these species were sampled from the inside of tomb that displays more suitable conditions for phototrophic growth. Stereomicroscopic observation and SEM images revealed that microorganisms were better located within the cavities of the stone, where the intensity of light is optimum for phototroph growth. In this study, the most frequent type of biodeteriorant algae belong to Trebouxia sp., Chlorococcum sp. and Trentepohlia sp. For cyanobacteria, the genus of Chroococcus sp., Oscillatoria sp., Microcystis sp., Aphanothece sp., andLyngbya sp. were dominant cyanobacteria. The first step in eliminating orcontrolling the growth of deteriorating microorganisms is their isolation andidentification. Thus, the present study was carried out to isolate and identifyinvolved microorganisms. Further investigation should be done to find the bestmethod to clean the surfaces of the stone.