Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light

Fixen, Kathryn R.; Baker, Anna W.; Stojković, Emina A.; Beatty, J. Thomas; Harwood, Caroline S.

doi:10.1073/pnas.1322410111

Cited by 27 publications

(29 citation statements)

References 52 publications

(60 reference statements)

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“…The chromophores of phytochromes from photosynthetic heterokonts such as diatoms and the phaeophyte Ectocarpus are less straightforward to predict. It is possible that these proteins are able to sense other signals or to signal without chromophore (35). Heterokont algae lack phycobiliproteins, but their genomes retain ferredoxin-dependent bilin reductases (FDBRs) required to synthesize phytobilins from BV (24,36).…”

Section: Resultsmentioning

confidence: 99%

Eukaryotic algal phytochromes span the visible spectrum

Rockwell

Duanmu

Martin

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

162

180

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Plant phytochromes are photoswitchable red/far-red photoreceptors that allow competition with neighboring plants for photosynthetically active red light. In aquatic environments, red and far-red light are rapidly attenuated with depth; therefore, photosynthetic species must use shorter wavelengths of light. Nevertheless, phytochrome-related proteins are found in recently sequenced genomes of many eukaryotic algae from aquatic environments. We examined the photosensory properties of seven phytochromes from diverse algae: four prasinophyte (green algal) species, the heterokont (brown algal) Ectocarpus siliculosus, and two glaucophyte species. We demonstrate that algal phytochromes are not limited to red and far-red responses. Instead, different algal phytochromes can sense orange, green, and even blue light. Characterization of these previously undescribed photosensors using CD spectroscopy supports a structurally heterogeneous chromophore in the far-red–absorbing photostate. Our study thus demonstrates that extensive spectral tuning of phytochromes has evolved in phylogenetically distinct lineages of aquatic photosynthetic eukaryotes.

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Section: Resultsmentioning

confidence: 99%

Eukaryotic algal phytochromes span the visible spectrum

Rockwell

Duanmu

Martin

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

162

180

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“…R. palustris strain CGA009 was used as the wild-type for this study. Anaerobic cultures were grown under illumination at 30 °C, using a defined media PM with 20 mM sodium acetate or 10mM sodium succinate as the carbon source ( 45 ). The longevity of R. palustris cultures was determined by counting the colony-forming units as described previously ( 12 ).…”

Section: Methodsmentioning

confidence: 99%

Bacterial longevity requires protein synthesis and a stringent response

Yin

Nakayasu

et al. 2019

Preprint

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Gram-negative bacteria in infections, biofilms and industrial settings often stop growing due to nutrient depletion, immune responses or environmental stresses. Bacteria in this state tend to be tolerant to antibiotics and are often referred to as dormant. Rhodopseudomonas palustris, a phototrophic α-proteobacterium, can remain fully viable for more than four months when growth is arrested. Here, we show that protein synthesis, specific proteins involved in translation and a stringent response are required for this remarkable longevity. Because it can generate ATP from light during growth arrest, R. palustris is an extreme example of a bacterial species that will stay alive for long periods of time as a relatively homogeneous population of cells and it is thus an excellent model organism for studies of bacterial longevity. There is evidence that other Gram-negative species also continue to synthesize proteins during growth arrest and that a stringent response is required for their longevity as well. Our observations challenge the notion that growth-arrested cells are necessarily dormant and metabolically inactive, and suggest that such bacteria may have a level of metabolic activity that is higher than many would have assumed. Our results also expand our mechanistic understanding of a crucial but understudied phase of the bacterial life cycle.IMPORTANCEWe are surrounded by bacteria; but they do not completely dominate our planet despite the ability of many to grow extremely rapidly in the laboratory. This has been interpreted to mean that bacteria in nature are often in a dormant state. We investigated life in growth arrest of Rhodopseudomonas palustris, a proteobacterium that stays alive for months when it is not growing. We found that cells were metabolically active; they continued to synthesize proteins and mounted a stringent response, both of which were required for their longevity. Our results suggest that long-lived bacteria are not necessarily inactive but have an active metabolism that is well adjusted to life without growth.

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“…R. palustris also grows aerobically as a heterotroph, and some strains grow anaerobically in the dark by nitrate respiration. It has served as a model organism for studies of anaerobic aromatic compound degradation, hydrogen gas production, nitrogen fixation, and photosynthesis (13)(14)(15)(16)(17)(18)(19)(20)(21). R. palustris grows by budding in which a motile daughter swarmer cell is pinched off from the pole of a sessile mother cell once chromosome replication is complete (22).…”

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confidence: 99%

Essential Genome of the Metabolically Versatile Alphaproteobacterium Rhodopseudomonas palustris

et al. 2016

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Rhodopseudomonas palustris is an alphaproteobacterium that has served as a model organism for studies of photophosphorylation, regulation of nitrogen fixation, production of hydrogen as a biofuel, and anaerobic degradation of aromatic compounds. This bacterium is able to transition between anaerobic photoautotrophic growth, anaerobic photoheterotrophic growth, and aerobic heterotrophic growth. As a starting point to explore the genetic basis for the metabolic versatility of R. palustris, we used transposon mutagenesis and Tn-seq to identify 552 genes as essential for viability in cells growing aerobically on semirich medium. Of these, 323 have essential gene homologs in the alphaproteobacterium Caulobacter crescentus, and 187 have essential gene homologs in Escherichia coli. There were 24 R. palustris genes that were essential for viability under aerobic growth conditions that have low sequence identity but are likely to be functionally homologous to essential E. coli genes. As expected, certain functional categories of essential genes were highly conserved among the three organisms, including translation, ribosome structure and biogenesis, secretion, and lipid metabolism. R. palustris cells divide by budding in which a sessile cell gives rise to a motile swarmer cell. Conserved cell cycle genes required for this developmental process were essential in both C. crescentus and R. palustris. Our results suggest that despite vast differences in lifestyles, members of the alphaproteobacteria have a common set of essential genes that is specific to this group and distinct from that of gammaproteobacteria like E. coli. IMPORTANCEEssential genes in bacteria and other organisms are those absolutely required for viability. Rhodopseudomonas palustris has served as a model organism for studies of anaerobic aromatic compound degradation, hydrogen gas production, nitrogen fixation, and photosynthesis. We used the technique of Tn-seq to determine the essential genes of R. palustris grown under heterotrophic aerobic conditions. The transposon library generated in this study will be useful for future studies to identify R. palustris genes essential for viability under specialized growth conditions and also for survival under conditions of stress.

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Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light

Cited by 27 publications

References 52 publications

Eukaryotic algal phytochromes span the visible spectrum

Eukaryotic algal phytochromes span the visible spectrum

Bacterial longevity requires protein synthesis and a stringent response

Essential Genome of the Metabolically Versatile Alphaproteobacterium Rhodopseudomonas palustris

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