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Monuments and Caves: Effect of Cyanobacteria

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STUDIES ON THE ROLE OF EPILITHIC AND CRYPTOENDOLIHIC CYANOBACTERIA ON MONUMENTS AND CAVES OF WESTERN ODISHA AND STRATEGIC DEVELOPMENT OF THEIR CONSERVATION TECHNOLOGY.

ABSTRACT

Cyanobacteria are morphologically diverse group of Gram negative photosynthetic prokaryotes successfully colonize and inhabit almost all kind of terrestrial and aquatic habitat including extreme habitats such as rocks and external walls of monuments and buildings. Natural and rock cut cave characterized by extreme condition also offer a unique habitat for cyanobacteria. These groups of organisms are prone to environmental stress such as desiccation, temperature and UV radiation. Cyanobacteria adopted survival strategies by producing photo protective pigments and bio-active compounds.

There are two schools of thoughts regarding the role of cyanobacteria on exposed rock surface of monumental works. Few opined in favor as these groups of microorganisms prevent deteriorating rock surface and monument get well preserved. Colonization of cyanobacteria can protect friable sand stone from the ravage of rain and wind by coalescing sand grain into a hard mass. Other school of thought belong to a number of workers, cyanobacteria make blackish brown crust /tuft on rock surfaces deteriorate the texture of substratum affect the fine carving of rock. Conclusive investigation is found inevitable to know whether cyanobacteria induce deterioration or check bio-erosion of stone objects. Future investigation is to test hardiness in order of porosity and tensile strength of stone object inoculating stress compatible strain of cyanobacteria over the substratum. If inoculant will found as agent of deterioration conservation strategy for rock based monuments can be carried out. In contrast to that no conservation strategy will require if bio inoculant found suitable to prevent weathering of stone object by coalescing sand grains.

Western Odisha also referred as Koshal is a territory in western part of Odisha is known for its possession of historically significant temples, caves and monuments. Frequent rock falling from these monuments is now a matter of great concern for all groups of people. Scientific reason behind this event is yet to be carried out. Few workers have made responsible to cyanobacteria for its cryptic role in losing contact between individual rock and also, deterorating stone objects. Biodeterioration of monuments and stone artifacts leads to both economic loss and damage of our cultural heritage. In order to develop effective control and restoration or conservation strategies for monuments, knowledge of the occurrence and diversity of microorganisms, including cyanobacteria and their activity in the surface biofilms is essential. Reports on epilithic and cryptoendolithic cyanobacterial flora of these places are meager. Significant taxonomic enumeration along with studies on eco-physiological (Screening of dessication, temperature and UV stress compatible strain) aspect of cyanoprokaryotes of these places is the starting point for successful conservation treatment and control of these stone monuments.

KEY WORDS: Cyanobacteria, Desiccation, UV, Artifacts, Biofilms, Cryptoendolithic.

The epilithic cyanobacteria have gained notoriety as potent biodeteriogens, causing aesthetically unacceptable discoloration and biodeterioration of colonized surfaces of walls of monuments, temples and historical buildings (Crispim and Gaylarde, 2005; Crispim et al., 2003; Crispim et al., 2006; Crispim et al., 2004; Gaylarde and Gaylarde, 1999; Gaylarde and Gaylarde, 2005). 

Cyanobacteria in biofilms or crusts on open rock surfaces and external walls of buildings frequently experience water stress (desiccation stress) and high light intensities combined with increased levels ultraviolet (UV) radiation (Büdel, 1999) extracellular polymeric substances (EPSs) that are crucial in different processes, including surface colonization, cell aggregation and biofilms formation and stabilization.

Pigments produced by cyanobacteria cause discoloration of colonized monuments/buildings, whereas production of EPSs and acid or alkaline secretion are primarily responsible for bioweathering and decay of their constructional rocks (Gaylarde and Gaylarde, 1999; Ortega-Morales et al., 2000; Wessels and Büdel, 1995).

State of art

Cyanobacteria successfully colonize and inhabit almost all kinds of terrestrial and aquatic habitat including extreme lithic habitats such as rocks and external walls of monuments and buildings (Budel, B.1999; Adhikary, 2000; Gorbushina, 2007; Hauer, 2008; Macedo et al., 2009; Makandar and Bhatnagar, 2010; Zammit et al.,2011; Deepa et al; 2011). Caves also offer an unique habitat for rare forms of life.Natural and rock cut caves generally are characterized by extreme conditions and low nutrients availability (Pederson, 2000). Cyanobacteria often occurs in lime stone wall and rock in caves paticulllarly in entrance zone where opimal growth conditions prevail (Mulec et al.,2008; Martinez and Asencio, 2010; Marcinkowska and Mrozinska, 2011).

Colonization of cyanobacteria along with other algae in the form of colour patches have been documented by many authors. Surface water in very small rock pores (small tight open spaces between the sand grains) make conducive for microbial flora to flourish along with several species of cyanobacteria (Broady, 1981). Bio-induced physical wheathering of sand stone is quite well documentd (Barker et al., 1997; Budel et al., 2004). Wheathering of sand stone was reported by Friedman and Weed, 1987; Nienow and Friedmann, 1993). The lithobiont (rock inhabiting cyanobacteria) are potent biodeteriogens causing aesthetically unacceptable discoloration and biodeterioration of colonized surface of walls of monuments, temples and historical buildings (Madhavan et al., 2008; Khan and Kulathuran, 2010; Pandey, 2011). These biodeteriogens of concrete, mortar and stones by producing organic and inorganic acids (Gaylarde and Morton, 1999; Brehm et al., 2005). Most of the archaeologically important monuments therefore look blakish brown due to excessive growth of the cyanobacteria as crust mats (Joshi and Mukundan, 1997; Tomaseli et al., 2000; Pattnaik et al., 2002; Welton et al.,2003; Crispim et al., 2003; Uher et al., 2005; Uher, B, 2008; Cappiteli et al.,2012). Microbial deterioration of stone is a widely recognized problem affecting monuments and buildings. These crusts and mats of cyanobacteria creates problem for conservation of ancient monuments and cave paintings around the world. Identifyinng the microorganisms involved in bio-deterioration is one of the most important steps in the study of microbial ecology of monumental stones.

Environmental tolerances of extremophillic rock dwelling cyanobacteria were studied by many workers. Cyanobacteria in biofilms or crusts on open rock surfaces and external walls of buildings frequently experience water stress (desiccation stress). Fernandez (1993) studied the response of cyanobacteria to water stress. Apte (1975) reported the molecular basis of tolerance of cyanobacteria to salinity and drought. Novel water stress proteins from a dessication tolerant cyanobacteria was studied by Schner and Potts (1989). Effect of temperature on cyanobacteria was also, studied more extensively. Most cyanobacteria investigated to date response to stress by synthesizing new set of proteins (Bhagwat and Apte, 1989; Blondin, 1993; Adhikary, 2003). Specific stress polypeptides were detected in few drought resistance cyanobacteria (Hershkovitz et al., 1991). Several cyanobacteria were greatly affected by temperature shifts (Borbely et al.,1985).

Also, many cyanobacteria are known to tolerate environmental extremes like UV light and their resistance to dessication and tolerance for high level of light intensities and UV radiation provide them a distinct advantage for their survival on exposed surfaces. To cope with the intence solar radiation some cyanobacteria synthesize UV sunscreen pigments including scytonemin, mycosporin like aminoacids and biopterin glucosides (Shibata, 1969; Scherer et al., 1988; Garcia Pichel and Castenholtz, 1991; Matsunaga et al.,1993; Dilon et al.,1999; Karsten et al.,2007; Sinha et al.,2008; Rastogi etal., 2010). There are several reports on the effect of UV radiation on Nitrogenase activity as it relates to the role of Cyanobacteria in the Nitrogen economy of ecosystem (Rai et al.,1995; Uma Maheswari and Anand, 2003; Solheim et al., 2006).

OBJECTIVES

  1. Survey and collection of epilithic cyanobacterial crust and rock samples comprising cryptoendolithic cyanobacteria from monuments and caves of western odisha.
  2. Isolation, purification and systematic account of cyanobacteria from collected samples and its further maintenance in laboratory condition.
  3. Taxonomic enumeration of cyanobacterial flora by morphometric analysis.
  4. Study of growth, pigments (chlorophyll, carotenoids, phycocyanin and phycoerythrin), MAA, protein and sugar content of purified cultures.
  5. To analyze Nitrogenase activity and photosynthetic efficiency of all pure epilithic and endolithic cyanobacterial culture.
  6. To assess the effect of UV and temperature stress on growth, pigment contents, nitrogenase activity and photosynthetic electron transport of experimental organisms in laboratory condition.
  7. Screening of stress compatible(UV, dessication and temperature) compatible epilithic and cryptoendolithic cyanobacterial strains to be used as experimental bio-inoculant on the surface of monumental substratum (marble, limestone dolomite and sandstone).
  8. Comparative analysis of natural monumental rocks and bio (cyanobacterial) induced rocks based on physical parameters like porosity and tensile strength.
  9. Strategic development of suitable conservation technology of monuments using algicidal specific for regional isolates.

TOTAL RESEARCH PLAN (PHASE WISE)

1st Phase

Survey, isolation, maintenance and morpho-metric analysis of epilithic and cryptoendolithic cyanobacteria from different monuments (temples, statues and caves) and elevated structures of Western Odisha.

2nd Phase

Study of physico – chemical parameters including effect of various stress on all experimental organisms.

3rd Phase

Physical parameter like porosity (volume % and median pore access diameter in micrometer) and tensile strength of natural monumental rock and bio (cy-anobacterial) induced rocks. Strategic development of suitable conservation technology of rock works.

MATERIALS AND METHODS

A. Sampling

Collection of epilithic cyanobacterial crust and rock samples from different monuments and caves by scrapping the surface of the various study sites. Collected materials have to be assign strain number and have to put in a suitable BG 11 ± medium (Rippka et al., 1979).

B. Observation, Culturing and Identification

1 - Identification of cyanobacterial strains by Desikachary, 1959; Komarek and Angnostidis, 1989 and Anagnostidis and Komarek, 1990.

C. Maintenance of pure culture

D. Study of Biochemical parameters

1. Growth

Measurement of growth will be done by light scattering technique taking the absorbance at 760nm.

2. Total protein content

Total protein content will be measured as per Lowry et al., 1951.

3. Pigments

a) Chlorophyll

Measurment of chlorophyll content as per Mackinney, 1941.

b) Carotenoid

Carotenoid will be measured by formula of Jensen, 1978.

c) Phycobiliprotein

Phycobiliprotein will be isolated in Po4 buffer and quantified as per Bennet and Bogoard, 1973.

d) Scytonemin (Dillon and Castenholz, 1999).

4. Photosynthetic Electron Transport ability

Electron transport ability of PS II will be measured in terms of DCPIP Photoreduction ( Swain et al., 1990).

5. Study of Nitrogenase activity ( Hardy et al., 1973).

6. Sugar as per anthrone method (Herbert et al., 1971).

7. Mineralogical study viz pore space by Mercury Intrusion porosimetry and tensile strength by Brazilian Splitting method.


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