Macromonas bipunctata
Douglas Scheidt

Deep within the caves of western America and Europe lurks a mysterious microbe. This microbe sits and waits in abundance within a white substance called moonmilk, which collects on walls deep inside the caves. The microbe is a bacterium called Macromonas bipunctata, which was named Psuedomonas bipunctata by Gicklhorn in 1920, and renamed to its current name by Utermohl and Koppe in 1923; however it was not isolated until 1989 by Dubinina and Grabovich.

Macromonas bipunctata is a Gram negative bacterium that is heterotrophic and a strict aerobe. It is motile as well. It is lophotrichous, so it moves around by using a polar tuft of flagella located on one end of its body. The bacterium is about 2-4 x 3-7 micrometers in size and is cylindrical or sometimes slightly pear shaped. It appears to be a mesophile, since the procedure for culturing is set at around 28 degrees Celsius. In addition, Macromonas bipunctata appears to be a neutrophile, being cultured around a pH of 7.2-7.4. Research is still being done on this microbe, but most scientists have concluded that it consists partly of calcium carboxylate (CaCO3). It has been suspected that Macromonas bipunctata is, at least in part, responsible for metabolizing organic acids and precipitating calcite into a different form of calcite crystals. These crystals are unstable and will solidify into the long crystal structure that makes up moonmilk. This bacteria has more recently been classified as a colorless sulfur bacteria that has the ability to oxidize reduced or partially oxidized inorganic sulfur compounds.

The moonmilk in which Macromonas bipunctata is found has somewhat of an interesting background as well. Moonmilk is soft and pasty when it is wet (comparable to cream cheese) and is hard and crumbly when it is dry. There are two distinct stories of its origin. One comes from the German-speaking part of Switzerland where people believed that the moonmilk was formed by the rays of the moon. People during the 16th Century thought that light from celestial bodies gained substance as it passed through rock, which produced metallic ores, or in this case, the nighttime dew which made up the moonmilk. The other story is of peasants who believed gnomes put the moonmilk in caves for people to use. Both stories end up sharing a common theme in that the moonmilk was used as medicine. People often used moonmilk to cure infections and speed up the healing process. Moonmilk is made up of more than just Macromonas bipunctata. It also contains cyanobacteria, fungi, green algae, and actinomycetes, which are the main producers of antibiotics. This explains why it was effective as a potential healing substance.

There are many microorganisms working together in moonmilk, it is still uncertain as to exactly what Macromonas bipunctata uses as an energy source. Moonmilk is mainly found where water is allowed to move through the substance. It is believed that the bacteria and microflora work together in their natural life processes to disintegrate rock from the cave and produce the moonmilk substance.


This is a picture of moonmilk in a dry state. This formation was created through the effort of many bacteria, including Macromonas bipunctata, and other microorganisms working together naturally.


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*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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