Bacterial Community Morphogenesis Is Intimately Linked to the Intracellular Redox State

Former address: Department of Biology and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139.
Journal of bacteriology (Impact Factor: 2.81). 01/2013; 195(7). DOI: 10.1128/JB.02273-12
Source: PubMed


Many microbial species form multicellular structures comprising elaborate wrinkles and concentric rings, yet the rules governing
their architecture are poorly understood. The opportunistic pathogen Pseudomonas aeruginosa produces phenazines, small molecules that act as alternate electron acceptors to oxygen and nitrate to oxidize the intracellular
redox state and that influence biofilm morphogenesis. Here, we show that the depth occupied by cells within colony biofilms
correlates well with electron acceptor availability. Perturbations in the environmental provision, endogenous production,
and utilization of electron acceptors affect colony development in a manner consistent with redox control. Intracellular NADH
levels peak before the induction of colony wrinkling. These results suggest that redox imbalance is a major factor driving
the morphogenesis of P. aeruginosa biofilms and that wrinkling itself is an adaptation that maximizes oxygen accessibility and thereby supports metabolic homeostasis.
This type of redox-driven morphological change is reminiscent of developmental processes that occur in metazoans.

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Available from: Lars E. Dietrich, May 13, 2014
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    • "It has been reported that the redox status is highly critical for the microorganisms to cope with environmental stresses (Cannon and Remington, 2009; Morgan et al., 2011). The intracellular redox state has been demonstrated to have a great impact in driving the morphological development of biofilms (Dietrich et al., 2013). To understand the role of redox state in biofilm development and responses of biofilms to environmental perturbations, it is essential to quantify the redox state of microenvironments in biofilms. "
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    ABSTRACT: Biofilms are the most ubiquitous and resilient form of microbial life on earth. One most important feature of a biofilm is the presence of a self-produced matrix, which creates highly heterogeneous and dynamic microenvironments within biofilms. Redox status in biofilm microenvironments plays a critical role in biofilm development and function. However, there is a lack of non-intrusive tools to quantify extracellular redox status of microenvironments within a biofilm matrix. In this study, using Shewanella oneidensis as a model organism, we demonstrated a novel approach to monitor extracellular redox status in biofilm microenvironments. Specifically, we displayed a redox sensitive fluorescence protein roGFP onto the cell surface of S. oneidensis by fusing it to the C-terminal of BpfA, a large surface protein, and used the surface displayed roGFP as a sensor to quantify the extracellular redox status in the matrix of S. oneidensis biofilms. The fusion of roGFP into BpfA has no negative impacts on cell growth and biofilm formation. Upon exposure to oxidizing agents such as H2O2, Ag+, and SeO32-, S. oneidensis BpfA-roGFP cells exhibited a characteristic fluorescence of roGFP. Proteinase treatment assay and super-resolution structured illumination microscopy confirmed the surface localization of BpfA-roGFP. We further used the surface displayed roGFP monitored the extracellular redox status in the matrix at different depths of a biofilm exposed to H2O2. This study provides a novel approach to non-invasively monitor extracellular redox status in microenvironments within biofilms, which can be used to understand redox responses of biofilms to environmental perturbations. Biotechnol. Bioeng. © 2014 Wiley Periodicals, Inc.
    Full-text · Article · Mar 2015 · Biotechnology and Bioengineering
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    • "As only shortly mentioned in this review, macrocolony biofilms also exhibit striking macroscopic morphological patterns of ridges, rings and wrinkles, a phenotype that has been termed 'wrinkled', 'rugose' or 'rdar' ('rough, dry and red', with 'redness' depending on the use of the dye Congo Red), although these simple designations do not adequately reflect the complexity and diversity of these structures, which are drastically modulated by oxygen content, the presence of reactive oxygen species or salt or the humidity at the agar surface (Römling, 2005; Aguilar et al., 2007; Beyhan et al., 2007; DePas et al., 2013; Dietrich et al., 2013; Kolodkin-Gal et al., 2013; Serra et al., 2013a). A common signature of these structures is their strict dependence on extracellular matrix components (Friedman and Kolter, 2004; Römling, 2005; Romero et al., 2010; Colvin et al., 2012; Serra et al., 2013a,b), which confer the connectivity and elasticity that allow growing bacterial biofilms to essentially behave as tissues that buckle up under the spatial constraints and therefore tension generated by cellular crowding (Serra et al., 2013a; Trejo et al., 2013). "
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    • "The abundance of phenazines could then offer an alternative electron acceptor in oxygen limited conditions, thereby increasing 2,3-butanedione production and growth or survival of acetoin metabolizing strains (for example, Streptococcus spp.). Phenazine producing mutants of P. aeruginosa have been shown to form biofilms with architecture that increases surface area to increase access to oxygen, supporting the role of phenazines as alternative electron acceptors when access to oxygen is reduced (Dietrich et al., 2013). As shown in Figure 7b, phenazines that accept electrons from NADH that is produced in the course of microbial catabolism may recycle their redox state when they come into contact with O 2 or Fe 3 þ , depending on oxygen availability, pH and the redox potential of the phenazine (Wang and Newman, 2008). "
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    ABSTRACT: The airways of cystic fibrosis (CF) patients are chronically colonized by patient-specific polymicrobial communities. The conditions and nutrients available in CF lungs affect the physiology and composition of the colonizing microbes. Recent work in bioreactors has shown that the fermentation product 2,3-butanediol mediates cross-feeding between some fermenting bacteria and Pseudomonas aeruginosa, and that this mechanism increases bacterial current production. To examine bacterial fermentation in the respiratory tract, breath gas metabolites were measured and several metagenomes were sequenced from CF and non-CF volunteers. 2,3-butanedione was produced in nearly all respiratory tracts. Elevated levels in one patient decreased during antibiotic treatment, and breath concentrations varied between CF patients at the same time point. Some patients had high enough levels of 2,3-butanedione to irreversibly damage lung tissue. Antibiotic therapy likely dictates the activities of 2,3-butanedione-producing microbes, which suggests a need for further study with larger sample size. Sputum microbiomes were dominated by P. aeruginosa, Streptococcus spp. and Rothia mucilaginosa, and revealed the potential for 2,3-butanedione biosynthesis. Genes encoding 2,3-butanedione biosynthesis were disproportionately abundant in Streptococcus spp, whereas genes for consumption of butanedione pathway products were encoded by P. aeruginosa and R. mucilaginosa. We propose a model where low oxygen conditions in CF lung lead to fermentation and a decrease in pH, triggering 2,3-butanedione fermentation to avoid lethal acidification. We hypothesize that this may also increase phenazine production by P. aeruginosa, increasing reactive oxygen species and providing additional electron acceptors to CF microbes.The ISME Journal advance online publication, 9 January 2014; doi:10.1038/ismej.2013.229.
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