The process of spicule formation in L. virgulata results in a drop in pH, which, if left unregulated, could lead to demineralization and subsequent animal death. Carbonic anhydrase has been suggested as a possible pH regulatory mechanism in L. virgulata tissues. This study focuses on an additional hypothetical mechanism of pH regulation involving the production of urease by endosymbiotic bacteria living within L. virgulata tissue. PCR and DGGE are used as culture-independent methods to characterize facets of microbial community structure on L.