Abstract

Phototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacterium Synechocystis sp. strain PCC 6803 (here Synechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT) Synechocystis caused extensive biofilm formation in a 2,000- liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenic Synechocystis forms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding by Synechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export in Escherichia coli, had a superbinding phenotype. In WT cultures, 1.2 × BG11 medium induced aggregation to the same degree as 0.8 × BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WT Synechocystis cells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.

Original languageEnglish (US)
Article numbere02192-18
JournalApplied and environmental microbiology
Volume85
Issue number7
DOIs
StatePublished - Apr 1 2019

Fingerprint

Synechocystis
Biofilms
biofilm
nutrient content
Food
nutrient
fimbriae
exopolysaccharides
cells
mutants
Photobioreactors
culture media
Axenic Culture
assay
Synechocystis sp. PCC 6803
microorganisms
Environmental Biodegradation
axenic culture
Biofuels
nutrient limitation

Keywords

  • Aggregation
  • Biofilms
  • Biofuels
  • Biogeochemistry
  • Blooms
  • Cyanobacteria
  • Exopolysaccharide
  • HABs
  • Photobioreactor
  • Synechocystis

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

Cite this

@article{ee43eacf312c424d9fca300c034f8a6b,
title = "Axenic biofilm formation and aggregation by synechocystis sp. Strain PCC 6803 are induced by changes in nutrient concentration and require cell surface structures",
abstract = "Phototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacterium Synechocystis sp. strain PCC 6803 (here Synechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT) Synechocystis caused extensive biofilm formation in a 2,000- liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenic Synechocystis forms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding by Synechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export in Escherichia coli, had a superbinding phenotype. In WT cultures, 1.2 × BG11 medium induced aggregation to the same degree as 0.8 × BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WT Synechocystis cells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.",
keywords = "Aggregation, Biofilms, Biofuels, Biogeochemistry, Blooms, Cyanobacteria, Exopolysaccharide, HABs, Photobioreactor, Synechocystis",
author = "Rey Allen and Bruce Rittmann and Roy Curtiss",
year = "2019",
month = "4",
day = "1",
doi = "10.1128/AEM.02192-18",
language = "English (US)",
volume = "85",
journal = "Applied and Environmental Microbiology",
issn = "0099-2240",
publisher = "American Society for Microbiology",
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TY - JOUR

T1 - Axenic biofilm formation and aggregation by synechocystis sp. Strain PCC 6803 are induced by changes in nutrient concentration and require cell surface structures

AU - Allen, Rey

AU - Rittmann, Bruce

AU - Curtiss, Roy

PY - 2019/4/1

Y1 - 2019/4/1

N2 - Phototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacterium Synechocystis sp. strain PCC 6803 (here Synechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT) Synechocystis caused extensive biofilm formation in a 2,000- liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenic Synechocystis forms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding by Synechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export in Escherichia coli, had a superbinding phenotype. In WT cultures, 1.2 × BG11 medium induced aggregation to the same degree as 0.8 × BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WT Synechocystis cells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.

AB - Phototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacterium Synechocystis sp. strain PCC 6803 (here Synechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT) Synechocystis caused extensive biofilm formation in a 2,000- liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenic Synechocystis forms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding by Synechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export in Escherichia coli, had a superbinding phenotype. In WT cultures, 1.2 × BG11 medium induced aggregation to the same degree as 0.8 × BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WT Synechocystis cells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.

KW - Aggregation

KW - Biofilms

KW - Biofuels

KW - Biogeochemistry

KW - Blooms

KW - Cyanobacteria

KW - Exopolysaccharide

KW - HABs

KW - Photobioreactor

KW - Synechocystis

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U2 - 10.1128/AEM.02192-18

DO - 10.1128/AEM.02192-18

M3 - Article

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AN - SCOPUS:85063684420

VL - 85

JO - Applied and Environmental Microbiology

JF - Applied and Environmental Microbiology

SN - 0099-2240

IS - 7

M1 - e02192-18

ER -