The tests (shells) of agglutinated foraminiferan protists are composed of mineral grains tightly bound by a chemically-resistant, biological cement (i.e., """"""""bioadhesive"""""""" of """"""""extracelllular matrix""""""""). During test morphogenesis, their pseudopodial networks collect mineral grains from the sediment, secrete bioadhesives in the proper amount and location, and through their coordinated movements, sculpt these architecturally-elegant structures. The high abundance of key, giant agglutinated species at our Antarctic collection site makes this foraminiferan community uniquely suited for studying specific aspects of agglutinated test construction, and addressing related questions concerning the phylogeny of the group. Our morphogenetic studies will focus on Astrammina rara - a giant unicellular system that allows us to study the secretion and assembly of bioadhesive in a cold-adpted marine organism without the complications of cell-cell and cell-tissue interactions common to the metazoan systems. Studies using time-lapse videomicroscopy, light -and HVEM cytochemistry and polyacrylamide gel electrophoresis will provide information on agglutinated test construction at the cellular and biochemical levels of analysis. Materials testing combined finite element analysis will characterize the mechanical properties of A.rara's bioadhesive. From a practical standpoint, this environmentally- safe bioadhesive binds immunoglobulins and has useful material properties that may have biotechnological applications. Finally, molecular phylogenetic analyses, based on 18S rDNA sequence data of selected species, will provide a much-needed framework for determining the evolution of this important protisan taxon.
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