CULTIVATING AN ENDOLITHIC CYANOBACTERIUM

The bioerosion of carbonate minerals by some boring cyanobacteria is one of the longest known and best described interactions between microbes and minerals. It has also one of the longest fossil records, recognised since the Precambrian up to the present in the form of microborings, microfossils and other sedimentary signatures (1, 2). This geomicrobial activity affects the rock cycle of marine carbonate platforms in a significant manner (1). In spite of all the importance of boring cyanobacteria, the mechanism by which carbonate bioerosion occurs, remains largely unknown and is at odds with the geochemical models that predict the precipitation of carbonates by oxygenic phototrohic cyanobacterial metabolism (3).

The lack of appropriate cultivated isolates of euendolithic cyanobacteria that can bore in the laboratory under controlled experimental conditions has been the main single handicap in solving the paradox of the boring mechanisms of cyanobacteria. In this work, we report on the isolation and cultivation of a novel isolate of cyanobacteria, resembling the morphologically complex genus Fischerella (or Matteia) in the Stigonematales, that actively penetrates carbonate minerals in the laboratory. We used SEM, optical microscopy as well as chlorophyll determinations to study the boring process by this organism on calcite under a variety of environmental and physiological conditions. We also will report on the growth, attachment and boring capacity on a variety of mineralogically pure substrates that include various carbonates, phosphates and sulfates.

Bibliography

1.- Golubic, S., Friedmann, I. & Schneider, J. 1981. The lithobiontic ecological niche, with special reference to microorganisms. J. Sediment. Petrol. 51:475–8.

2.- Chacón, E., Berrendero, E. and Garcia-Pichel, F., 2006. Biogeological signatures of microboring cyanobacterial communities in marine carbonates from Cabo Rojo, Puerto Rico., Sed. Geol. 185: 215–228.

3.- Garcia-Pichel, F. 2006. Plausible mechanisms for the boring on carbonates by microbial phototrophs. Sed. Geol. 185: 205–213.