Advances in engineered Bacillus subtilis biofilms and spores, and their applications in bioremediation, biocatalysis, and biomaterials

Bacillus subtilis is a commonly used commercial specie with broad applications in the fields of bioengineering and biotechnology.B.subtilis is capable of producing both biofilms and spores.Biofilms are matrix-encased multicellular communities that comprise various components including exopolysaccharides,proteins,extracellular DNA,and poly-γ-glutamic acid.These biofilms resist environmental conditions such as oxidative stress and hence have applications in bioremediation technologies.Furthermore,biofilms and spores can be engineered through biotechnological techniques for environmentally-friendly and safe production of bio-products such as enzymes.The ability to withstand with harsh conditions and producing spores makes Bacillus a suitable candidate for surface display technology.In recent years,the spores of such specie are widely used as it is generally regarded as safe to use.Advances in synthetic biology have enabled the reprogramming of biofilms to improve their functions and enhance the production of value-added products.Globally,there is increased interest in the production of engineered biosensors,biocatalysts,and biomaterials.The elastic modulus and gel properties of B.subtilis biofilms have been utilized to develop living materials.This review outlines the formation of B.subtilis biofilms and spores.Biotechnological engineering processes and their increasing application in bioremediation and biocatalysis,as well as the future directions of B.subtilis biofilm engineering,are discussed.Furthermore,the ability of B.subtilis biofilms and spores to fabricate functional living materials with self-regenerating,self-regulating and environmentally responsive characteristics has been summarized.This review aims to resume advances in biological engineering of B.subtilis biofilms and spores and their applications.

Probing the growth and mechanical properties of Bacillus subtilis biofilms through genetic mutation strategies

Bacterial communities form biofilms on various surfaces by synthesizing a cohesive and protective extracellular matrix,and these biofilms protect microorganisms against harsh environmental conditions.Bacillus subtilis is a widely used experimental species,and its biofilms are used as representative models of beneficial biofilms.Specifically,B.subtilis biofilms are known to be rich in extracellular polymeric substances(EPS)and other biopolymers such as DNA and proteins like the amyloid protein TasA and the hydrophobic protein BslA.These materials,which form an interconnected,cohesive,three-dimensional polymer network,provide the mechanical stability of biofilms and mediate their adherence to surfaces among other functional contributions.Here,we explored how genetically-encoded components specifically contribute to regulate the growth status,mechanical properties,and antibiotic resistance of B.subtilis biofilms,thereby establishing a solid empirical basis for understanding how various genetic engineering efforts are likely to affect the structure and function of biofilms.We noted discrete contributions to biofilm morphology,mechanical properties,and survival from major biofilm components such as EPS,TasA and BslA.For example,EPS plays an important role in maintaining the stability of the mechanical properties and the antibiotic resistance of biofilms,whereas BslA has a significant impact on the resolution that can be obtained for printing applications.This work provides a deeper understanding of the internal interactions of biofilm components through systematic genetic manipulations.It thus not only broadens the application prospects of beneficial biofilms,but also serves as the basis of future strategies for targeting and effectively removing harmful biofilms.