FdTonB is involved in the photoregulation of cellular morphology during complementary chromatic adaptation in Fremyella diplosiphon

2012

Microbiology

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Fremyella diplosiphon modifies the pigment composition of its major light-harvesting complexes, i.e. phycobilisomes, and cell and filament morphology according to ambient light quality in a process termed complementary chromatic adaptation (CCA). The cells are red in colour and rectangular shaped, and filaments are longer under green light (GL), in contrast with blue-green, spherical cells and shorter filaments under red light (RL). In this study, we report that wild-type (WT) UTEX 481 and WT-pigmented, shortened filament strain SF33 of F. diplosiphon accumulate reactive oxygen species (ROS) under both GL and RL, with the level of oxidative stress being higher under RL as compared with GL. During CCA, higher levels of ROS under RL are correlated with the RL-specific spherical cell shape and filament fragmentation -cells exhibiting elevated levels of ROS under RL have reduced cell length, yet the width of cells is not affected. Addition of ascorbic acid to RL-grown cultures resulted in lower ROS levels and a concomitant shift to GL-associated cellular morphology, i.e. an increased cell length. This observation identifies an RL-dependent oxidative-stress-mediated regulation of morphogenesis in a bacterial system. Spherical cell morphology may result from ROS-dependent changes in the cell membrane integrity or cell wall loosening and associated cell expansion.

Section: Introductionmentioning

confidence: 99%

Reactive oxygen species are involved in the morphology-determining mechanism of Fremyella diplosiphon cells during complementary chromatic adaptation

Singh

2012

Microbiology

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“…1). 8 TonB has no apparent impact on pigmentation. 8 The molecular mechanism(s) employed by TonB to impact cell width is still under investigation.…”

Section: Introductionmentioning

confidence: 95%

“…4,[6][7][8][9][10][11] Characterization of a ΔcpcF mutant, which lacks virtually all PBPs, provided strong evidence that cellular morphology is regulated reversibly by GL and RL, largely separate from the impacts of these light qualities on PBP pigment accumulation. 10 A ΔcpcF mutant accumulates less than 5% of phycoerythrin (PE) and phycocyanin (PC) levels of WT and lower allophycocyanin (AP) levels than WT, yet the length of ΔcpcF cells under GL and RL differed little from WT.…”

Section: Dissecting the Regulatory Mechanisms Controlling Distinct Asmentioning

confidence: 99%

“…TonB function in GL, 8 others for which the identity of the mutation has not been elucidated, 11 and likely others yet that have not been identified at all. Components that appear to largely impact pigmentation are CpcF under RL and GL, 10 and CpeD, 9 CpeE, 11 and CpeBA 9 under GL.…”

Section: ©2 0 1 1 L a N D E S B I O S C I E N C E D O N O T D I S Tmentioning

confidence: 99%

“…4,7 Our analyses of the factors that function downstream of RcaE in the regulation of distinct aspects of CCA, i.e., pigmentation vs. morphology, indicate that some common factors are involved, particularly under RL; 7 yet, a number of distinct components contribute to light-dependent control of pigmentation and/or morphology in this organism. [8][9][10][11] Recent results provide an emerging picture that downstream of the central RL-and GL-responsive photoreceptor RcaE the regulation of morphology and pigmentation, the principal features of CCA, are mediated by independently driven processes at the molecular level.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Convergence and divergence of the photoregulation of pigmentation and cellular morphology inFremyella diplosiphon

Pattanaik

Whitaker

Plant Signaling & Behavior

2011

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Photosynthetic pigment accumulation and cellular and filament morphology are regulated reversibly by green light (GL) and red light (RL) in the cyanobacterium Fremyella diplosiphon during complementary chromatic adaptation (CCA). The photoreceptor RcaE (regulator of chromatic adaptation), which appears to function as a light-responsive sensor kinase, controls both of these responses. Recent findings indicate that downstream of RcaE, the signaling pathways leading to light-dependent changes in morphology or pigment synthesis and/or accumulation, branch and utilize distinct molecular components. We recently reported that the regulation of the accumulation of the GL-absorbing photosynthetic accessory protein phycoerythrin (PE) and photoregulation of cellular morphology are largely independent, as many mutants with severe PE accumulation defects do not have major disruptions in the regulation of cellular morphology. Furthermore, morphology can be disrupted under GL without impacting GL-dependent PE accumulation. Most recently, however, we determined that the disruption of the cpeR gene, which encodes a protein that is known to function as an activator of PE synthesis under GL, results in disruption of cellular morphology under GL and RL. Thus, apart from RcaE, CpeR is only the second known regulator to impact morphology under both light conditions in F. diplosiphon.

Regulation of biofilm formation and cellular buoyancy through modulating intracellular cyclic di‐GMP levels in engineered cyanobacteria

Agostoni

Waters

Biotech & Bioengineering

2015

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The second messenger cyclic dimeric (3'→5') GMP (cyclic di-GMP or c-di-GMP) has been implicated in the transition between motile and sessile lifestyles in bacteria. In this study, we demonstrate that biofilm formation, cellular aggregation or flocculation, and cellular buoyancy are under the control of c-di-GMP in Synechocystis sp. PCC 6803 (Synechocystis) and Fremyella diplosiphon. Synechocystis is a unicellular cyanobacterium and displays lower levels of c-di-GMP; F. diplosiphon is filamentous and displays higher intracellular c-di-GMP levels. We transformed Synechocystis and F. diplosiphon with a plasmid for constitutive expression of genes encoding diguanylate cylase (DGC) and phosphodiesterase (PDE) proteins from Vibrio cholerae or Escherichia coli, respectively. These engineered strains allowed us to modulate intracellular c-di-GMP levels. Biofilm formation and cellular deposition were induced in the DGC-expressing Synechocystis strain which exhibited high intracellular levels of c-di-GMP; whereas strains expressing PDE in Synechocystis and F. diplosiphon to drive low intracellular levels of c-di-GMP exhibited enhanced cellular buoyancy. In addition, the PDE-expressing F. diplosiphon strain showed elevated chlorophyll levels. These results imply roles for coordinating c-di-GMP homeostasis in regulating native cyanobacterial phenotypes. Engineering exogenous DGC or PDE proteins to regulate intracellular c-di-GMP levels represents an effective tool for uncovering cryptic phenotypes or modulating phenotypes in cyanobacteria for practical applications in biotechnology applicable in photobioreactors and in green biotechnologies, such as energy-efficient harvesting of cellular biomass or the treatment of metal-containing wastewaters.