1 research outputs found
Induced Mineralization of Hydroxyapatite in Escherichia coli Biofilms and the Potential Role of Bacterial Alkaline Phosphatase
Biofilms appear when bacteria colonize a surface and
synthesize
and assemble extracellular matrix components. In addition to the organic
matrix, some biofilms precipitate mineral particles such as calcium
phosphate. While calcified biofilms induce diseases like periodontitis
in physiological environments, they also inspire the engineering of
living composites. Understanding mineralization mechanisms in biofilms
will thus provide key knowledge for either inhibiting or promoting
mineralization in these research fields. In this work, we study the
mineralization of Escherichia coli biofilms
using the strain E. coli K-12 W3110,
known to produce an amyloid-based fibrous matrix. We first identify
the mineralization conditions of biofilms grown on nutritive agar
substrates supplemented with calcium ions and β-glycerophosphate.
We then localize the mineral phase at different scales using light
and scanning electron microscopy in wet conditions as well as X-ray
microtomography. Wide-angle X-ray scattering enables us to further
identify the mineral as being hydroxyapatite. Considering the major
role played by the enzyme alkaline phosphatase (ALP) in calcium phosphate
precipitation in mammalian bone tissue, we further test if periplasmic
ALP expressed from the phoA gene in E. coli is involved in biofilm mineralization. We
show that E. coli biofilms grown on
mineralizing medium supplemented with an ALP inhibitor undergo less
and delayed mineralization and that purified ALP deposited on mineralizing
medium is sufficient to induce mineralization. These results suggest
that also bacterial ALP, expressed in E. coli biofilms, can promote mineralization. Overall, knowledge about hydroxyapatite
mineralization in E. coli biofilms
will benefit the development of strategies against diseases involving
calcified biofilms as well as the engineering of biofilm-based living
composites