Stone-eating
bacteria belong to several families in the genus Thiobacillus. They can
cause damage to monuments, tombs, buildings, and sculptures by converting
marble into plaster. The principal danger seems to come from Thiobacillus thioparus.
This microbe's metabolic system converts sulfur dioxide gas (found in the
air) into sulfuric acid and uses it to transform calcium carbonate (marble)
into calcium sulfate (plaster). The bacilli draw their nutrition from carbon dioxide
formed in the transformation. Nitrobacter and Nitrosomonas are other
"stone-eating bacteria" that use ammonia from the air to generate
nitric and nitrous acid. Still other kinds of bacteria and fungi can produce
organic acids (formic, acetic, and oxalic acids) which attack the stone as well.
The presence of these microbes was first observed by French scientist Henri Pochon
at Angkor Wat, Cambodia, during the 1950s. The increase of these bacteria and other
biological-damaging organisms that threaten tombs and buildings of antiquity are
due to the sharp climb in the level of free sulfur dioxide gas in the
atmosphere from automotive and industrial emissions. (The Handy Science Answer
Book, compiled by the Science and Technology department of the Carnegie Library
of Pittsburgh)
Stone-eating
bacteria belong to several families in the genus Thiobacillus. They can
cause damage to monuments, tombs, buildings, and sculptures by converting
marble into plaster. The principal danger seems to come from Thiobacillus thioparus.
This microbe's metabolic system converts sulfur dioxide gas (found in the
air) into sulfuric acid and uses it to transform calcium carbonate (marble)
into calcium sulfate (plaster). The bacilli draw their nutrition from carbon dioxide
formed in the transformation. Nitrobacter and Nitrosomonas are other
"stone-eating bacteria" that use ammonia from the air to generate
nitric and nitrous acid. Still other kinds of bacteria and fungi can produce
organic acids (formic, acetic, and oxalic acids) which attack the stone as well.
The presence of these microbes was first observed by French scientist Henri Pochon
at Angkor Wat, Cambodia, during the 1950s. The increase of these bacteria and other
biological-damaging organisms that threaten tombs and buildings of antiquity are
due to the sharp climb in the level of free sulfur dioxide gas in the
atmosphere from automotive and industrial emissions. (The Handy Science Answer
Book, compiled by the Science and Technology department of the Carnegie Library
of Pittsburgh)