Abstract:

Irradiation experiments were conducted on a well-characterized protein-containing extracellular polymeric substance (EPS) from Sagitulla stellata (ss), a lignin-transforming marine gram-negative aerobic bacterium. The turbidity level was monitored to indicate the flocculation progress during irradiation, and the aggregates were collected for the mass measurement and FTIR analysis. By assessing the protein contents of ss EPS to that of a phytoplankton (amp), in conjunction with ROS experiments, the possible mechanisms are revealed. This dataset contains measurements of aggregate weight, dissolved organic carbon (DOC), dissolved nitrogen (DN), Fourier transform infrared spectroscopy (FTIR) absorbance, UV-Vis absorbance, and turbidity.

Suggested Citation:

Luni Sun; Peter Santschi. 2017. EPS mechanisms which aid in aggregation: A test of light to induce bacterial EPS aggregation, turbidity, aggregate weight, FTIR, DOC and DN, and UV-Vis. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N78S4MXW

Publications:

Sun, L., Xu, C., Zhang, S., Lin, P., Schwehr, K. A., Quigg, A., … Santschi, P. H. (2017). Light-induced aggregation of microbial exopolymeric substances. Chemosphere. doi:10.1016/j.chemosphere.2017.04.099

Purpose:

To examine the possibility of light-induced aggregation of bacterial extracellular polymeric substance (EPS).

Data Parameters and Units:

EPS= extracellular polymeric substance; ss= Sagitulla stellata; amp= Amphora; ASW= artificial seawater; SW= salt water (same salinity (35) as ASW but with all cation ion being replaced by Na+); Dissolved organic carbon=DOC; dissolved nitrogen=DN Aggregate weight: weight (mg) ss= Sagitulla stellata; amp= Amphora; Blank (ASW): with only ASW filtered Dark: no exposure Light: under irradiation Glass (1h): sample in glass for 1 hours Quartz (4h): sample in quartz for 4 hours (as example) filter1 (mg) = weight of filter replicate 1, milligrams filter2 (mg) =weight of filter replicate 2, milligrams filter+aggregate1(mg) = weight of filter replicate 1 plus aggregate after solution filtered, milligrams filter+aggregate2(mg) = weight of filter replicate 2 plus aggregate after solution filtered (milligrams) DOC, DN: ppm ss= Sagitulla stellata; amp= Amphora; Blank (ASW): with only ASW filtered Dark: no exposure Light: under irradiation condition: details whether the irradiation treatment was carried out using a glass or quartz flask UV-Vis: (UV-Vis) absorbance (no unit) wavelength; ss eps sample prior to any treatment FTIR: IR (infrared) absorbance (no unit) ss eps sample prior to any treatment and of the aggregate after resuspension in ASW and irradiation for 1 hr in glass Turbidity: turbidity (NTU = Nephelometric Turbidity Units) ss= Sagitulla stellata; amp= Amphora; ASW= artificial seawater; SW= salt water Dark: no exposure Light: under irradiation Time: exposure time in minutes DMSO (.OH): with quencher DMSO to test .OH effect Azide (1O2): with quencher sodium azide to test 1O2 effect pyrate (hydroperoxide): with quencher sodium pyrate to test hydroperoxide effect Amp ASW dark 0: amp in ASW in dark at time point 0 (as example) Turbidity1= replicate 1 Turbidity2 = replicate 2

Methods:

The Sagitulla stellata (ss) extracellular polymeric substance (EPS) was dissolved in milli-Q water, artificial seawater (ASW), and salt water, respectively with final concentration of 10 mg/L. The samples were filtered through 0.2 μm polycarbonate filter. The UV-vis absorbance spectrum was measured for ss EPS. The samples were irradiated in 250 mL borosilicate or quartz flasks outdoor in a water bath. The samples were irradiated under natural sunlight in the noon or in dark as control. The turbidity level was measured during irradiation using a turbidity meter. Only turbidity was measured for Amphora (amp) in ASW and salt water. The effects of 1O2, HO•, hydroperoxide, and superoxide (•O2–) were tested by adding the quenchers sodium azide, dimethyl sulfoxide (DMSO), sodium pyruvate, and superoxide dismutase, respectively to ss EPS in milli-Q water. The salinity was adjusted to 29 with concentrated ASW after 1h irradiation. The turbidity of each sample was compared to the dark control and that with no quencher addition. After irradiation, the samples were filtered through 0.2 μm filter. The weight of the aggregates collected on the filter was calculated by the weight difference of the filters before and after filtration. Dissolved organic carbon (DOC) and dissolved nitrogen (DN) of the filtrate were measured on a Shimadzu TOC-L analyzer. The freeze-dried EPS and the resultant aggregate in ASW were analyzed by ATR-FTIR. UV-Vis: samples were measured in the well, the data was collected every 1 nm wavelength. FTIR: 650 to 4000 cm-1 wavenumber range with 100 co-added scans, a sensitivity of 8, and a resolution of 8 cm-1. The spectra were baseline corrected and smoothed using a 5-point Savitzky–Golay quad-cubic function. Turbidity: The turbidity level was measured on the turbidity meter during irradiation. DOC, DN: The filtrate was diluted 3 times and acidified to pH <3. The filtrate was measured on the instrument. Aggregate weight: The weight of the aggregate collected on the filter was calculated by the difference of the weight of the filter before and after filtration. The blank sample was only filtered through ASW.

Instruments:

UV-Vis: Biotech-Epoch UV-vis spectrometer FTIR: Varian 3100 Excalibur FTIR with triple reflection diamond PIKE ATR Turbidity: turbidity meter (Hach 2100Q) DOC, DN: Shimadzu TOC-L analyzer Aggregate weight: balance (Mettler Toledo)

Error Analysis:

Turbidity: Two measurements. DOC, DN: automatic by instrument, coefficient of variation set to 3% or less. Aggregate weight: each sample was weighed twice

Individual Files: