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Yoo, YD, Seong KA, Myung G, Kim HS, Jeong HJ, Palenik B, Yih W.  2015.  Ingestion of the unicellular cyanobacterium Synechococcus by the mixotrophic red tide ciliate Mesodinium rubrum. Algae. 30:281-290.   10.4490/algae.2015.30.4.281   AbstractWebsite

We explored phagotrophy of the phototrophic ciliate Mesodinium rubrum on the cyanobacterium Synechococcus. The ingestion and clearance rates of M. rubrum on Synechococcus as a function of prey concentration were measured. In addition, we calculated grazing coefficients by combining the field data on abundance of M. rubrum and co-occurring Synechococcus spp. with laboratory data on ingestion rates. The ingestion rate of M. rubrum on Synechococcus sp. linearly increased with increasing prey concentrations up to approximately 1.9 x 10(6) cells mL(-1), to exhibit sigmoidal saturation at higher concentrations. The maximum ingestion and clearance rates of M. rubrum on Synechococcus were 2.1 cells predator(-1) h(-1) and 4.2 nL predator(-1)h(-1), respectively. The calculated grazing coefficients attributable to M. rubrum on co-occurring Synechococcus spp. reached 0.04 day(-1). M. rubrum could thus sometimes be an effective protistan grazer of Synechococcus in marine planktonic food webs. M. rubrum might also be able to form recurrent and massive blooms in diverse marine environments supported by the unique and complex mixotrophic arrays including phagotrphy on hetrotrophic bacteria and Synecho coccus as well as digestion, kleptoplastidy and karyoklepty after the ingestion of cryptophyte prey.

Tetu, SG, Johnson DA, Varkey DR, Phillippy K, Stuart RK, Dupont C, Hassan KA, Palenik B, Paulsen IT.  2013.  Impact of DNA damaging agents on genome-wide transcriptional profiles in two marine Synechococcus species. Frontiers in Microbiology. 4   10.3389/fmicb.2013.00232   AbstractWebsite

Marine microorganisms, particularly those residing in coastal areas, may come in contact with any number of chemicals of environmental or xenobiotic origin. The sensitivity and response of marine cyanobacteria to such chemicals is, at present, poorly understood. We have looked at the transcriptional response of well characterised Synechococcus open ocean (WH8102) and coastal (CC9311) isolates to two DNA damaging agents, mitomycin C and ethidium bromide, using whole-genome expression microarrays. The coastal strain showed differential regulation of a larger proportion of its genome following √ęshock√≠ treatment with each agent. Many of the orthologous genes in these strains, including those encoding sensor kinases, showed different transcriptional responses, with the CC9311 genes more likely to show significant changes in both treatments. While the overall response of each strain was considerably different, there were distinct transcriptional responses common to both strains observed for each DNA damaging agent, linked to the mode of action of each chemical. In both CC9311 and WH8102 there was evidence of SOS response induction under mitomycin C treatment, with genes recA, lexA and umuC significantly upregulated in this experiment but not under ethidium bromide treatment. Conversely, ethidium bromide treatment tended to result in upregulation of the DNA-directed RNA polymerase genes, not observed following mitomycin C treatment. Interestingly, a large number of genes residing on putative genomic island regions of each genome also showed significant upregulation under one or both chemical treatments.

de la Broise, D, Palenik B.  2007.  Immersed in situ microcosms: A tool for the assessment of pollution impact on phytoplankton. Journal of Experimental Marine Biology and Ecology. 341:274-281.   10.1016/j.jembe.2006.10.045   AbstractWebsite

In situ phytoplankton microcosms were developed and characterized for use in toxicity testing. The microcosms contained 225 mu m filtered seawater maintained in 1 liter glass bottles attached to a plastic frame and immersed at 3 in under the sea surface. Synechococcus and picoeukaryote population dynamics in microcosms and the surrounding water were compared. A bloom-like behaviour observed for Synechococcus in these phytoplankton microcosms was avoided when 10% of the culture volume was replaced, every two days, by filtered seawater. After 2 weeks, no significant difference in Synechococcus and picoeukaryotes cell counts was observed in microcosms compared to the surrounding free seawater. Synechococcus fluorescence at 545 nm (phycoerythrobilin) fluctuated with a similar pattern in such microcosms and in free seawater and were shown to be correlated to light intensity fluctuations over a two week experiment. The in situ microcosms were used to study the impact of low copper additions. Synechococcus populations were dramatically decreased by copper addition, while picoeukaryote populations were increased simultaneously. Our data show that drastic changes in species composition can occur at copper concentrations encountered in polluted coastal areas. (c) 2006 Elsevier B.V. All rights reserved.

Dyhrman, ST, Palenik BP.  1997.  The identification and purification of a cell-surface alkaline phosphatase from the dinoflagellate Prorocentrum minimum (Dinophyceae). Journal of Phycology. 33:602-612.   10.1111/j.0022-3646.1997.00602.x   AbstractWebsite

Two cell-surface proteins were identified in the dinoflagellate Prorocentrum minimum (Pavillard) Schiller strain CCMP 1329 that are evident in phosphate-limited cultures, but not in nitrate-limited cultures or cultures growing-exponentially in complete media. These proteins were detected by labeling cell-surface proteins with the biotinylating reagent succinimidyl 6-(biotinamido) hexanoate. One protein, of approximately 200,000 daltons was purified using differential centrifugation, detergent extraction, and gel filtration chromatography. This purified protein was able to hydrolyze orthophosphate groups from p-nitrophenylphosphate at pH 8, indicating it is an alkaline phosphatase, although it is larger than other alkaline phosphatases isolated to date from most microorganisms. This protein may be induced to help P. minimum cleave orthophosphate groups from organic forms of phosphate in marine environments. Ultimately, this protein could represent a unique antigen for developing an antibody probe for examining the relationships between phosphate stress and bloom formation in P. minimum, and perhaps other dinoflagellates, in the field.