Abstract:

Exposure to oil has been shown to be lethal to most phytoplankton species, however, some are able to survive and grow at normal or reduced growth rates. This ability to tolerate oil exposure appears to be independent of the class and phylum of the phytoplankton and their ability to consume components of oil heterotrophically. We, therefore, conducted an experiment on oil-resistant chlorophyte; Dunaliella tertiolecta in control and water accommodated fraction of oil (WAF) with and without metabolic inhibitors targeting biochemical pathways (photosynthetic electron transport, cyclic electron transport of PSI, Kreb’s cycle, mitochondrial electron transport, pentose-phosphate pathway and photo-respiration). We found inhibiting pathways such as photosynthetic electron transport and pentose-phosphate pathway were lethal, however, inhibition of pathways such as mitochondrial electron transport chain and cyclic electron transport around PSI caused growth arrest in cells. Pathways such as photorespiration and Kreb’s cycle played a critical role in oil tolerating ability of Dunaliella tertiolecta. Analysis of photo-physiology revealed alteration in the photosynthetic apparatus under inhibition of photo-respiration and not Kreb’s cycle. Further studies on how these photo-respiration and Kreb’s cycle help the survival of Dunaliella tertiolecta is under way.

Suggested Citation:

Manoj Kamalanathan, Savannah Mapes, Patricia Faulkner, Jessica Hillhouse, David Hala, John Beardall, John Raven, Antonietta Quigg. 2019. Identification of biochemical pathways contributing to oil tolerant ability of Dunaliella tertiolecta. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/X3FBFZZH

Publications:

Kamalanathan, M., Mapes, S., Prouse, A., Faulkner, P., Klobusnik, N. H., Hillhouse, J., Hala, D., & Quigg, A. (2022). Core metabolism plasticity in phytoplankton: Response of Dunaliella tertiolecta to oil exposure. Journal of Phycology, 58(6), 804–814. Portico. https://doi.org/10.1111/jpy.13286

Purpose:

To gain a mechanistic understanding behind how oil affects green chlorophytes.

Data Parameters and Units:

The dataset consists of several excel files containing information on the parameters described below: Fv/Fm: relative fluorescence Sigma PSII: Å2 (quanta)-1 NPQ: relative fluorescence ROS: relative ROS per cell Chlorophyll a: microgram per cell Alpha: micromol e-.micromol-1 photons P: p ETRmax: micromol.electrons m2.s-1 Tau: microsecond Respiration rates: nmol O2. (10^7 cells). min-1 Cell counts: cells per ml Carbohydrate: mg Carbohydrates. Cell-1 Lactic acid: femtograms per cell Malic acid: femtograms per cell Glycolic acid: femtograms per cell Pyruvic acid: femtograms per cell Hydroxybutyric acid: femtograms per cell

Methods:

Macondo surrogate oil was used to make the WAF. The initial oil concentration was 3.25 mg/L. The WAF was prepared using the Chemical Response to Oil Spills Ecological Effects Research Forum (CROSERF) method mixing sterile f/2 growth media and oil (400 µL. L^-1^), the solution was overnight in the dark Wade (2017). The first experiment with the 7 metabolic inhibitors was run for a total duration of 5 days, the second experiment with just AOA as the inhibitors was run for a total of 7 days and the third experiment with just Control and WAF only ran for 48 hrs. All the experiments were run under 12:12 hr day/night light cycle. The light levels were 60 micromoles per sec per meter square. The concentration of the cells in the first experiment was 100,000 cells/ml. The concentration of the cells in the second experiment was 5833 cells per mL and in the third experiment was 10,000 cells/mL. Regular seawater obtained from NOAA was used for all the experiments.

Instruments:

Estimated oil equivalent (EOE) was measured using a Shimadzu spectrofluorometer (RF-5301PC; Shimadzu, Houston, TX, USA). Reactive Oxygen Species (ROS) was measured using a BioTek CytationTM 5 imaging reader controlled by Gen52.09 software (USA). Chlorophyll was measured using a benchtop fluorometer (10AU Fluorometer, Turner Designs, San Jose, CA, USA). All the other photosynthetic parameters were measured using a pulse amplitude modulated fluorescence system (Phyto-PAM, Walz, Germany) and the FIRe fluorometer system (Satlantic, Halifax NS, Canada).

Provenance and Historical References:

Wade, T. L., Morales-McDevitt, M., Bera, G., Shi, D., Sweet, S., Wang, B., … Knap, A. H. (2017). A method for the production of large volumes of WAF and CEWAF for dosing mesocosms to understand marine oil snow formation. Heliyon, 3(10), e00419. doi:10.1016/j.heliyon.2017.e00419

Individual Files: