Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm

ABSTRACT Bacterial biofilms are highly structured multicellular communities whose formation involves flagella and an extracellular matrix of adhesins, amyloid fibers, and exopolysaccharides. Flagella are produced by still-dividing rod-shaped Escherichia coli cells during postexponential growth when...

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Autores principales:	Diego O. Serra, Anja M. Richter, Gisela Klauck, Franziska Mika, Regine Hengge
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/da9de75af45b4b8494a6381bb3f7de67
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spelling	oai:doaj.org-article:da9de75af45b4b8494a6381bb3f7de672021-11-15T15:40:29ZMicroanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm10.1128/mBio.00103-132150-7511https://doaj.org/article/da9de75af45b4b8494a6381bb3f7de672013-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00103-13https://doaj.org/toc/2150-7511ABSTRACT Bacterial biofilms are highly structured multicellular communities whose formation involves flagella and an extracellular matrix of adhesins, amyloid fibers, and exopolysaccharides. Flagella are produced by still-dividing rod-shaped Escherichia coli cells during postexponential growth when nutrients become suboptimal. Upon entry into stationary phase, however, cells stop producing flagella, become ovoid, and generate amyloid curli fibers. These morphological changes, as well as accompanying global changes in gene expression and cellular physiology, depend on the induction of the stationary-phase sigma subunit of RNA polymerase, σS (RpoS), the nucleotide second messengers cyclic AMP (cAMP), ppGpp, and cyclic-di-GMP, and a biofilm-controlling transcription factor, CsgD. Using flagella, curli fibers, a CsgD::GFP reporter, and cell morphology as “anatomical” hallmarks in fluorescence and scanning electron microscopy, different physiological zones in macrocolony biofilms of E. coli K-12 can be distinguished at cellular resolution. Small ovoid cells encased in a network of curli fibers form the outer biofilm layer. Inner regions are characterized by heterogeneous CsgD::GFP and curli expression. The bottom zone of the macrocolonies features elongated dividing cells and a tight mesh of entangled flagella, the formation of which requires flagellar motor function. Also, the cells in the outer-rim growth zone produce flagella, which wrap around and tether cells together. Adjacent to this growth zone, small chains and patches of shorter curli-surrounded cells appear side by side with flagellated curli-free cells before curli coverage finally becomes confluent, with essentially all cells in the surface layer being encased in “curli baskets.” IMPORTANCE Heterogeneity or cellular differentiation in biofilms is a commonly accepted concept, but direct evidence at the microscale has been difficult to obtain. Our study reveals the microanatomy and microphysiology of an Escherichia coli macrocolony biofilm at an unprecedented cellular resolution, with physiologically different zones and strata forming as a function of known global regulatory networks that respond to biofilm-intrinsic gradients of nutrient supply. In addition, this study identifies zones of heterogeneous and potentially bistable CsgD and curli expression, shows bacterial curli networks to strikingly resemble Alzheimer plaques, and suggests a new role of flagella as an architectural element in biofilms.Diego O. SerraAnja M. RichterGisela KlauckFranziska MikaRegine HenggeAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 2 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Diego O. Serra Anja M. Richter Gisela Klauck Franziska Mika Regine Hengge Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm
description	ABSTRACT Bacterial biofilms are highly structured multicellular communities whose formation involves flagella and an extracellular matrix of adhesins, amyloid fibers, and exopolysaccharides. Flagella are produced by still-dividing rod-shaped Escherichia coli cells during postexponential growth when nutrients become suboptimal. Upon entry into stationary phase, however, cells stop producing flagella, become ovoid, and generate amyloid curli fibers. These morphological changes, as well as accompanying global changes in gene expression and cellular physiology, depend on the induction of the stationary-phase sigma subunit of RNA polymerase, σS (RpoS), the nucleotide second messengers cyclic AMP (cAMP), ppGpp, and cyclic-di-GMP, and a biofilm-controlling transcription factor, CsgD. Using flagella, curli fibers, a CsgD::GFP reporter, and cell morphology as “anatomical” hallmarks in fluorescence and scanning electron microscopy, different physiological zones in macrocolony biofilms of E. coli K-12 can be distinguished at cellular resolution. Small ovoid cells encased in a network of curli fibers form the outer biofilm layer. Inner regions are characterized by heterogeneous CsgD::GFP and curli expression. The bottom zone of the macrocolonies features elongated dividing cells and a tight mesh of entangled flagella, the formation of which requires flagellar motor function. Also, the cells in the outer-rim growth zone produce flagella, which wrap around and tether cells together. Adjacent to this growth zone, small chains and patches of shorter curli-surrounded cells appear side by side with flagellated curli-free cells before curli coverage finally becomes confluent, with essentially all cells in the surface layer being encased in “curli baskets.” IMPORTANCE Heterogeneity or cellular differentiation in biofilms is a commonly accepted concept, but direct evidence at the microscale has been difficult to obtain. Our study reveals the microanatomy and microphysiology of an Escherichia coli macrocolony biofilm at an unprecedented cellular resolution, with physiologically different zones and strata forming as a function of known global regulatory networks that respond to biofilm-intrinsic gradients of nutrient supply. In addition, this study identifies zones of heterogeneous and potentially bistable CsgD and curli expression, shows bacterial curli networks to strikingly resemble Alzheimer plaques, and suggests a new role of flagella as an architectural element in biofilms.
format	article
author	Diego O. Serra Anja M. Richter Gisela Klauck Franziska Mika Regine Hengge
author_facet	Diego O. Serra Anja M. Richter Gisela Klauck Franziska Mika Regine Hengge
author_sort	Diego O. Serra
title	Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm
title_short	Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm
title_full	Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm
title_fullStr	Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm
title_full_unstemmed	Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm
title_sort	microanatomy at cellular resolution and spatial order of physiological differentiation in a bacterial biofilm
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/da9de75af45b4b8494a6381bb3f7de67
work_keys_str_mv	AT diegooserra microanatomyatcellularresolutionandspatialorderofphysiologicaldifferentiationinabacterialbiofilm AT anjamrichter microanatomyatcellularresolutionandspatialorderofphysiologicaldifferentiationinabacterialbiofilm AT giselaklauck microanatomyatcellularresolutionandspatialorderofphysiologicaldifferentiationinabacterialbiofilm AT franziskamika microanatomyatcellularresolutionandspatialorderofphysiologicaldifferentiationinabacterialbiofilm AT reginehengge microanatomyatcellularresolutionandspatialorderofphysiologicaldifferentiationinabacterialbiofilm
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Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm

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