POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X Thurs. Morning Session<br />
REGULATION OF CELL FATE IN BACILLUS SUBTILIS BIOFILMS<br />
H. C. Vlamakis 1* , C. Aguilar 1* , R. Losick 2 , and R. Kolter 1<br />
1 Harvard Medical School, Boston, MA, 2 Harvard <strong>University</strong>, Cambridge, MA.<br />
*These authors contributed equally to this work.<br />
Many microbial populations differentiate from free-living planktonic cells into surfaceassociated<br />
multicellular communities known as bi<strong>of</strong>ilms. Within a bi<strong>of</strong>ilm, motile Bacillus subtilis<br />
cells differentiate into non-motile chains <strong>of</strong> cells that form parallel bundles held together by an<br />
extracellular matrix. These bundles eventually produce aerial structures that serve as<br />
preferential sites for sporulation. By analyzing strains harboring multiple cell-type specific<br />
promoter fusions we can visualize the spatial anatomy <strong>of</strong> at least three physiologically distinct<br />
cell populations within mature bi<strong>of</strong>ilms. Motile, matrix-producing, and sporulating cells localize to<br />
distinct regions within the bi<strong>of</strong>ilm and the localization and percentage <strong>of</strong> each cell type is<br />
dynamic. Mutants unable to produce extracellular matrix form unstructured bi<strong>of</strong>ilms that are<br />
deficient in sporulation. This suggests that in architecturally complex bi<strong>of</strong>ilms, spore formation<br />
is coupled to the production <strong>of</strong> extracellular matrix. The coupling <strong>of</strong> matrix production and<br />
sporulation could be explained by the phosphorylation state <strong>of</strong> the master transcriptional<br />
regulator Spo0A. Spo0A is phosphorylated both directly and through a phosphorelay by at least<br />
five different histidine kinase proteins. When cells have low levels <strong>of</strong> Spo0A-P, matrix genes<br />
are expressed; however, at higher levels <strong>of</strong> Spo0A-P, sporulation commences. We have found<br />
that a deletion <strong>of</strong> kinD, a gene encoding one <strong>of</strong> the kinases that feed into the Spo0A<br />
phosphorelay, is sufficient to restore sporulation to matrix-deficient mutants. We hypothesize<br />
that KinD is not acting as a kinase under these conditions, but rather functions as a<br />
phosphatase to delay sporulation until matrix (or a matrix-encased signal) is sensed.<br />
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