Figures & data
Fig. 1. Cultures of A. platensis NIES-39 after freezing and thawing.
Notes: (A) Growth of control samples. A trichome suspension in SOT medium (approximately 1 × 104 trichomes mL−1) was dispensed into ten tubes (1 mL each) and cultured for four days. Photographs were taken at the beginning of culture (Day 0) and after four days (Day 4). (B) Cultures of frozen-and-thawed samples. Trichomes (approximately 1 × 104 trichomes) were frozen under various conditions. After thawing, they were cultured for four days in 1 mL each of SOT medium. Ten samples were prepared and photographed for each set of conditions. The following conditions were used for the freezing: (a) Snap-freezing in SOT medium containing 5% (v/v) glycerol, (b) snap-freezing in SOT medium containing 5% DMSO, (c) snap-freezing in SOT medium containing 5% (v/v) MeOH and (d) freezing at a rate of approximately −1 °C min−1 in SOT medium containing 10% (v/v) DMSO. Asterisks indicate samples whose OD730 values were >0.15
Fig. 2. Recovery rate of A. platensis NIES-39 frozen under various conditions.
Notes: A. platensis NIES-39 (1 × 104 trichomes) were either snap-frozen in liquid nitrogen (A) or frozen at a cooling rate of approximately −1 °C min−1 (B) in 50 μL of SOT medium (Medium) or SOT medium containing various concentrations of glycerol, DMSO, or MeOH. After thawing, cells were cultured and the ratio of samples that grew to OD730 of more than 0.15 by the fourth day of culture were determined. Box plots show medians (thick horizontal lines), interquartile ranges (boxes), largest, and smallest values that are not outliers (whiskers) and outliers (circles).
Fig. 3. Growth of A. platensis NIES-39 after freezing and thawing.
Notes: A. platensis NIES-39 (6.4 × 103 trichomes) were frozen under various conditions and stored at −80 °C. The next day (day 0), they were rapidly thawed and trichome propagation was monitored by measuring OD730. All data at day 0 were obtained 30 min after sample thawing, except for the controls that had not been frozen (open circles). The following freezing conditions were used: trichomes suspended in SOT medium containing 10% (v/v) DMSO were frozen at a cooling rate of approximately −1 °C min−1 (closed circles), trichomes suspended in SOT medium containing 5% (v/v) DMSO (closed triangles) or 5% (v/v) glycerol (closed squares) were snap-frozen in liquid nitrogen. Means and standard deviations are shown (n = 6).
Fig. 4. Survival rate of A. platensis NIES-39 after prolonged cryopreservation.
Notes: A. platensis NIES-39 frozen at a cooling rate of approximately −1 °C min−1 in the presence of 10% (v/v) DMSO were stored either in the vapor phase of liquid nitrogen (circles) or in a −80 °C freezer (triangles). Samples were thawed after the indicated period of time, and survival rates were determined. Means and standard deviations are shown (n = 6). The asterisks indicate data points significantly different from the results of the day 1 samples (p < 0.05, Student’s t-test).
Table 1. Survival rate of various Arthrospira strains after freezing and thawing.
Supplemental material
