Bacillus subtilis biofilms resemble cross-linked hydrogels in their morphology and swelling properties. All the water in these biofilms is bound water. Water binding is mostly related with accumulated solutes.
Biomineralization
is a mineral precipitation process occurring
in the presence of organic molecules and used by various organisms
to serve a structural and/or a functional role. Many biomineralization
processes occur in the presence of extracellular matrices that are
composed of proteins and polysaccharides. Recently, there is growing
evidence that bacterial biofilms induce CaCO3 mineralization
and that this process may be related with their extracellular matrix
(ECM). In this study we explore, in vitro, the effect
of two bacterial ECM proteins, TasA and TapA, and an exopolysaccharide,
EPS, on calcium carbonate crystallization. We have found that all
the three biopolymers induce the formation of complex CaCO3 structures. The crystals formed in the presence of the EPS are very
diverse in morphology and they are either calcite or vaterite in structure.
However, more uniformly sized calcite crystals are formed in the presence
of the proteins; these crystals are composed of single crystalline
domains that assemble together into spherulites (in the presence of
TapA) or dumbbell-like shapes (in the presence of TasA). Our results
suggest the EPS affects the nucleation of calcium carbonate when it
induces the formation of vaterite crystals and that unlike EPS, the
proteins stabilize preformed calcite nuclei and induce their aggregation
into complex calcite structures. Biomineralization processes induced
by bacterial ECM macromolecules make biofilms more robust and difficult
to remove when they form, for example, on pipes and filters in water
desalination systems or on ship hulls. Understanding the formation
conditions and mechanism of formation of calcium carbonate in the
presence of bacterial biopolymers may lead to the design of suitable
mineralization inhibitors.
Biofilms are multicellular microbial communities that encase themselves in an extracellular matrix (ECM) of secreted biopolymers and attach to surfaces and interfaces. Bacterial biofilms are detrimental in hospital and industrial settings, but they can be beneficial, for example, in agricultural as well as in food technology contexts. An essential property of biofilms that grants them with increased survival relative to planktonic cells is phenotypic heterogeneity, the division of the biofilm population into functionally distinct subgroups of cells. Phenotypic heterogeneity in biofilms can be traced to the cellular level; however, the molecular structures and elemental distribution across whole biofilms, as well as possible linkages between them, remain unexplored. Mapping X-ray diffraction across intact biofilms in time and space, we revealed the dominant structural features in Bacillus subtilis biofilms, stemming from matrix components, spores, and water. By simultaneously following the X-ray fluorescence signal of biofilms and isolated matrix components, we discovered that the ECM preferentially binds calcium ions over other metal ions, specifically, zinc, manganese, and iron. These ions, remaining free to flow below macroscopic wrinkles that act as water channels, eventually accumulate and may possibly lead to sporulation. The possible link between ECM properties, regulation of metal ion distribution, and sporulation across whole, intact biofilms unravels the importance of molecular-level heterogeneity in shaping biofilm physiology and development.
Functional amyloid proteins are self-secreted by microbial cells that aggregate into extracellular networks and provide microbial colonies with mechanical stability and resistance to antibiotic treatment. In order to understand the...
Biofilms are surface-associated soft microbial communities, which may be either detrimental or beneficial to their hosting environment. They develop from single cells into mature colonies, that are composed of cells and sometimes (in Firmicutes phylum) spores, held together by an extracellular matrix (ECM) of secreted biomolecular components. Biofilm development is a dynamic process, during which cells organize into subgroups, creating functionally distinct regions in space. Specific examples of functional-spatial division in Bacillus subtilis biofilms include matrix and spore formation as well as water channels that form beneath wrinkles. An interesting question arising is whether the division of labor in biofilms is also reflected in the molecular-level order across whole biofilms. Using combined X-ray diffraction (XRD)/X-ray fluorescence (XRF), we studied the molecular order in intact biofilms across multiple length scales. We discovered that biofilms display a distinct spatio-temporal XRD signature that depends on highly ordered structures in spores and on cross beta sheet structures in matrix components. Spore signal is found especially enhanced with water molecules and metal-ions signals along macroscopic wrinkles, known to act as water channels. Demonstrating in situ the link between molecular structures, metal ions distribution and division of labor across whole biofilms in time and space, this study provides new pivotal insight to the understanding biofilm development.
Biofilms are surface or interface-associated communities of bacterial cells, embedded in a self-secreted extracellular matrix (ECM). Cells in biofilms are 100-1000 times more resistant to antibiotic treatment relative to planktonic...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.