http://hdl.handle.net/10453/84 2013-05-26T02:29:03Z 2013-05-26T02:29:03Z Behrendt Lars Schrameyer Verena Qvortrup Klaus Lundin Luisa Sã¸Rensen Sã¸Ren Larkum Anthony Kuhl Michael http://hdl.handle.net/10453/18205 2012-10-12T03:33:33Z 2012-01-01T00:00:00Z

Biofilm growth and near-infrared radiation-driven photosynthesis of the chlorophyll d-containing cyanobacterium Acaryochloris marina Behrendt Lars; Schrameyer Verena; Qvortrup Klaus; Lundin Luisa; Sã¸Rensen Sã¸Ren; Larkum Anthony; Kuhl Michael The cyanobacterium Acaryochloris marina is the only known phototroph harboring chlorophyll (Chl) d. It is easy to cultivate it in a planktonic growth mode, and A. marina cultures have been subject to detailed biochemical and biophysical characterization. In natural situations, A. marina is mainly found associated with surfaces, but this growth mode has not been studied yet. Here, we show that the A. marina type strain MBIC11017 inoculated into alginate beads forms dense biofilm-like cell clusters, as in natural A. marina biofilms, characterized by strong O-2 concentration gradients that change with irradiance. Biofilm growth under both visible radiation (VIS, 400 to 700 nm) and near-infrared radiation (NIR, similar to 700 to 730 nm) yielded maximal cell-specific growth rates of 0.38 per day and 0.64 per day, respectively. The population doubling times were 1.09 and 1.82 days for NIR and visible light, respectively. The photosynthesis versus irradiance curves showed saturation at a photon irradiance of E-k (saturating irradiance) >250 mu mol photons m(-2) s(-1) for blue light but no clear saturation at 365 mu mol photons m(-2) s(-1) for NIR. The maximal gross photosynthesis rates in the aggregates were similar to 1,272 mu mol O-2 mg Chl d(-1) h(-1) (NIR) and similar to 1,128 mu mol O-2 mg Chl d(-1) h(-1) (VIS). The photosynthetic efficiency (alpha) values were higher in NIR-irradiated cells [(268 +/- 0.29) x 10(-6) m(2) mg Chl d(-1) (mean +/- standard deviation)] than under blue light [(231 +/- 0.22) x 10(-6) m(2) mg Chl d(-1)]. A. marina is well adapted to a biofilm growth mode under both visible and NIR irradiance and under O-2 conditions ranging from anoxia to hyperoxia, explaining its presence in natural niches with similar environmental conditions.

2012-01-01T00:00:00Z Behrendt Lars Larkum Anthony Trampe Erik Norman Anders Sã¸Rensen Sã¸Ren Kuhl Michael http://hdl.handle.net/10453/18206 2012-10-12T03:33:33Z 2012-01-01T00:00:00Z

Microbial diversity of biofilm communities in microniches associated with the didemnid ascidian Lissoclinum patella Behrendt Lars; Larkum Anthony; Trampe Erik; Norman Anders; Sã¸Rensen Sã¸Ren; Kuhl Michael We assessed the microbial diversity and microenvironmental niche characteristics in the didemnid ascidian Lissoclinum patella using 16S rRNA gene sequencing, microsensor and imaging techniques. L. patella harbors three distinct microbial communities spatially separated by few millimeters of tunic tissue: (i) a biofilm on its upper surface exposed to high irradiance and O-2 levels, (ii) a cloacal cavity dominated by the prochlorophyte Prochloron spp. characterized by strong depletion of visible light and a dynamic chemical microenvironment ranging from hyperoxia in light to anoxia in darkness and (iii) a biofilm covering the underside of the animal, where light is depleted of visible wavelengths and enriched in near-infrared radiation (NIR). Variable chlorophyll fluorescence imaging demonstrated photosynthetic activity, and hyperspectral imaging revealed a diversity of photopigments in all microhabitats. Amplicon sequencing revealed the dominance of cyanobacteria in all three layers. Sequences representing the chlorophyll d containing cyanobacterium Acaryochloris marina and anoxygenic phototrophs were abundant on the underside of the ascidian in shallow waters but declined in deeper waters. This depth dependency was supported by a negative correlation between A. marina abundance and collection depth, explained by the increased attenuation of NIR as a function of water depth. The combination of microenvironmental analysis and fine-scale sampling techniques used in this investigation gives valuable first insights into the distribution, abundance and diversity of bacterial communities associated with tropical ascidians. In particular, we show that microenvironments and microbial diversity can vary significantly over scales of a few millimeters in such habitats; which is information easily lost by bulk sampling

2012-01-01T00:00:00Z Mitrovic Simon Bowling Lee Buckney Rodney http://hdl.handle.net/10453/18194 2012-10-12T03:33:32Z 2001-01-01T00:00:00Z

Quantifying potential benefits to Microcystic aeruginosa through disentrainment by buoyancy within an embayment of a freshwater river Mitrovic Simon; Bowling Lee; Buckney Rodney Vertical profiles of Microcystis aeruginosa and other phytoplankton were measured on several occasions within the main channel and an embayment of a freshwater tidal river. The cyanobacteria M. aeruginosa and Anabaena circinalis were able to migrate to surface waters within the embayment but not within the main channel. Using a quantitative estimate of primary productivity (over a 24 hour period), the potential benefits through disentrainment by buoyancy were determined for M. aeruginosa within the embayment and compared to the main channel. The population within the embayment had a daily integral of photosynthesis of 603.13 mmol of O(2)m(-2), nine times greater than the evenly distributed main channel population with a daily integral of 62.08 mmol of O(2)m(-2). It is likely that embayments along the tidally mixed reaches of the Hawkesbury River may be areas where M. aeruginosa can disentrain through buoyancy and enhance primary productivity rates.

2001-01-01T00:00:00Z Tan Yi Sun Lun-Quan Kamal Mohammad Wang Xiaoyang Seale J.P. Qu Xianqin http://hdl.handle.net/10453/18193 2012-10-12T03:33:32Z 2011-01-01T00:00:00Z

Suppression Of Retinol-binding Protein 4 With Rna Oligonucleotide Prevents High-fat Diet-induced Metabolic Syndrome And Non-alcoholic Fatty Liver Disease In Mice Tan Yi; Sun Lun-Quan; Kamal Mohammad; Wang Xiaoyang; Seale J.P.; Qu Xianqin Conflicting data have been reported regarding the role of retinol-binding protein (RBP4) in insulin resistance, obesity, type 2 diabetes and non-alcoholic fatty liver disease (NAFLD). In this study, we used pharmacological methods to investigate the role

2011-01-01T00:00:00Z