Nacre (mother of pearl) is an attractive model for the development of new
materials. Its sheet structure of alternating layers of calcium carbonate and an
organic matrix confers it highly desirable properties such as high toughness and
strength. In this study, we produce a nacre-inspired composite material using
only bacterially-produced components. Calcium carbonate is crystallized via the
action of ureolytic bacteria. After each crystallization event, we apply
bacterially produced γ-polyglutamate (PGA) to the sample, which
promotes layering compared to the PGA-free control. We show that the combination
of these two compounds yields a layered material reminiscent of nacre, showing a
way towards the biotechnological production of new, nacre-inspired
materials.