Biofilm Growth and Near-Infrared Radiation-Driven Photosynthesis of the Chlorophyll
            <i>d</i>
            -Containing Cyanobacterium Acaryochloris marina

Behrendt, Lars; Schrameyer, Verena; Qvortrup, Klaus; Lundin, Luisa; Sørensen, Søren J.; Larkum, Anthony W. D.; Kühl, Michael

doi:10.1128/aem.00397-12

Cited by 23 publications

(17 citation statements)

References 54 publications

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“…The model uses alginate-encapsulated (24, 25) P. aeruginosa, mimicking growth conditions under diffusion limitation through the secondary matrix as seen in chronic infections (26).…”

Section: Discussionmentioning

confidence: 99%

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Sønderholm

Kragh

Koren

et al. 2017

Appl Environ Microbiol

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124

113

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Alginate beads represent a simple and highly reproducible in vitro model system for diffusion-limited bacterial growth. In this study, alginate beads were inoculated with Pseudomonas aeruginosa and followed for up to 72 h. Confocal microscopy revealed that P. aeruginosa formed dense clusters similar in size to in vivo aggregates observed ex vivo in cystic fibrosis lungs and chronic wounds. Bacterial aggregates primarily grew in the bead periphery and decreased in size and abundance toward the center of the bead. Microsensor measurements showed that the O2 concentration decreased rapidly and reached anoxia ∼100 μm below the alginate bead surface. This gradient was relieved in beads supplemented with NO3− as an alternative electron acceptor allowing for deeper growth into the beads. A comparison of gene expression profiles between planktonic and alginate-encapsulated P. aeruginosa confirmed that the bacteria experienced hypoxic and anoxic growth conditions. Furthermore, alginate-encapsulated P. aeruginosa exhibited a lower respiration rate than the planktonic counterpart and showed a high tolerance toward antibiotics. The inoculation and growth of P. aeruginosa in alginate beads represent a simple and flexible in vivo-like biofilm model system, wherein bacterial growth exhibits central features of in vivo biofilms. This was observed by the formation of small cell aggregates in a secondary matrix with O2-limited growth, which was alleviated by the addition of NO3− as an alternative electron acceptor, and by reduced respiration rates, as well as an enhanced tolerance to antibiotic treatment.IMPORTANCE Pseudomonas aeruginosa has been studied intensively for decades due to its involvement in chronic infections, such as cystic fibrosis and chronic wounds, where it forms biofilms. Much research has been dedicated to biofilm formation on surfaces; however, in chronic infections, most biofilms form small aggregates of cells not attached to a surface, but embedded in host material. In this study, bacteria were encapsulated in small alginate beads and formed aggregates similar to what is observed in chronic bacterial infections. Our findings show that aggregates are exposed to steep oxygen gradients, with zones of oxygen depletion, and that nitrate may serve as an alternative to oxygen, enabling growth in oxygen-depleted zones. This is important, as slow growth under low-oxygen conditions may render the bacteria tolerant toward antibiotics. This model provides an alternative to surface biofilm models and adds to the comprehension that biofilms do not depend on a surface for formation.

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“…The model uses alginate-encapsulated (24, 25) P. aeruginosa, mimicking growth conditions under diffusion limitation through the secondary matrix as seen in chronic infections (26).…”

Section: Discussionmentioning

confidence: 99%

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Sønderholm

Kragh

Koren

et al. 2017

Appl Environ Microbiol

Self Cite

124

113

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“…A promising approach for enrichment and growth of Prochloron cells in gradients under controlled biofilm-like conditions could be based on immobilization of extracted Prochloron cells in alginate beads; an approach recently shown to work with A. marina (Behrendt et al, 2012b). …”

Section: Discussionmentioning

confidence: 99%

Microenvironmental Ecology of the Chlorophyll b-Containing Symbiotic Cyanobacterium Prochloron in the Didemnid Ascidian Lissoclinum patella

et al. 2012

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The discovery of the cyanobacterium Prochloron was the first finding of a bacterial oxyphototroph with chlorophyll (Chl) b, in addition to Chl a. It was first described as Prochloron didemni but a number of clades have since been described. Prochloron is a conspicuously large (7–25 μm) unicellular cyanobacterium living in a symbiotic relationship, primarily with (sub-) tropical didemnid ascidians; it has resisted numerous cultivation attempts and appears truly obligatory symbiotic. Recently, a Prochloron draft genome was published, revealing no lack of metabolic genes that could explain the apparent inability to reproduce and sustain photosynthesis in a free-living stage. Possibly, the unsuccessful cultivation is partly due to a lack of knowledge about the microenvironmental conditions and ecophysiology of Prochloron in its natural habitat. We used microsensors, variable chlorophyll fluorescence imaging and imaging of O2 and pH to obtain a detailed insight to the microenvironmental ecology and photobiology of Prochloron in hospite in the didemnid ascidian Lissoclinum patella. The microenvironment within ascidians is characterized by steep gradients of light and chemical parameters that change rapidly with varying irradiances. The interior zone of the ascidians harboring Prochloron thus became anoxic and acidic within a few minutes of darkness, while the same zone exhibited O2 super-saturation and strongly alkaline pH after a few minutes of illumination. Photosynthesis showed lack of photoinhibition even at high irradiances equivalent to full sunlight, and photosynthesis recovered rapidly after periods of anoxia. We discuss these new insights on the ecological niche of Prochloron and possible interactions with its host and other microbes in light of its recently published genome and a recent study of the overall microbial diversity and metagenome of L. patella.

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“…By extending the PAR band, Acaryochloris marina can even exploit the near-infrared light. 35 Given solar radiation, not more than about 9 % of the full spectrum energy can be converted into biomass. 36 However, considering only the PAR region, the maximal efficiency of photosynthesis is estimated to be 11.3 %.…”

Section: Light Quantity and Qualitymentioning

confidence: 99%

Photo-autotrophic Production of Poly(hydroxyalkanoates) in Cyanobacteria

Drosg¹,

Fritz²,

Gattermayr³

et al. 2015

Chem.Biochem.Eng.Q.

100

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In the last two decades, poly(hydroxyalkanoates) (PHA) were solely produced using heterotrophic bacteria in aerobic cultivation. With respect to the great potential (500 Mt yr -1 ) of raw industrial CO 2 streams and even greater potential of flue gases, the focus on photo-autotrophic biotechnological processes is increasing steadily. Primarily, PHA-gene transfer from heterotrophic bacteria into algae and plant cells was attempted, with the intention to combine the known biosynthesis pathway with autotrophic cultivation. The natural occurrence of PHA in cyanobacteria is known at least since 1966. However, cyanobacteria were never considered for commercial production because the PHA amount based on cell mass and based on volumetric productivity is generally very low. Therefore, strain improvements were suggested, either by gene amplification or by suppression of biochemical pathways competing for the cell's acetate pool. In the late 1990s, the success of genetic modification was confirmed experimentally, elevating the cyanobacteria cell's PHA content. With additional optimization, PHB amounts up to 50 % w/w of biomass dry matter or up to about 2.4 g L -1 bioreactor volume could be produced within 11 days. Considering the land use for agriculture and the competition for plant biomass between food, feed, fuel and energy production, the binding of CO 2 in a biotechnological process using photo-autotrophic microorganisms may become a promising option.

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Biofilm Growth and Near-Infrared Radiation-Driven Photosynthesis of the Chlorophyll d -Containing Cyanobacterium Acaryochloris marina

Cited by 23 publications

References 54 publications

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Microenvironmental Ecology of the Chlorophyll b-Containing Symbiotic Cyanobacterium Prochloron in the Didemnid Ascidian Lissoclinum patella

Photo-autotrophic Production of Poly(hydroxyalkanoates) in Cyanobacteria

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