Biodeterioration vs Biodegradation: the Role of Mieroorganisms in the Removal of Pollutants Deposited on Historie Buildings

INTRODUCTlON T his papc r describes sorne biodegrada tion processes onginating from ¡he activity of microorganisms in the black c rusts o f hi sto rie bui ldi ngs . T he crusts are main ly composeJ of gypsum. ca rbonaceolls particles. a nd polycyclic aromatic hydr carbo ns. T he slowly d issolv ing gypsum from black c rusts reprcscn ts a contin uo us sou rce of sulphur for microbial grow th. T he sulphate-bonding capaci ty of the shea th of cyanobacteria ca uses a pa rticul rly high demand for sulpha te. t hu~ mak ing s ulphur nutrit ion a releva nt a~peCl in their physiology . On the other hand , bacteria capa ble o f us ing pol ycyc1ic a roma tic hydrocarbons a:.; a sa le ca rhon <L nJ ene rgy source we re isolat d (rom monuments. These examples illustra tc th<l t n the surraces of building stones. loca ted in poll uted environments, t llere is a conti nuous deposit ion a ndo at the same time. a hiodegradation oC poll llta n ts leading la thei r removal.