Comparison of growth and toxicity responses between non-toxic and toxic strains of Prorocentrum hoffmannianum

Abstract

We aimed to study the growth and toxicity responses of non-toxic (CCMP683) and toxic (CCMP2804) strains of Prorocentrum hoffmannianum under various nitrate and phosphate concentrations. The 2 strains were cultured in L1-Si medium with standard, depleted or 10-fold repleted nitrate or phosphate. CCMP683 cultured in standard L1-Si medium exhibited delayed growth. Nitrate or phosphate depletion decreased the cell density of both strains. Repletion of nitrate slightly increased the cell density of both strains. Repletion of phosphate also slightly increased the cell density of CCMP2804 but surprisingly decreased the cell density of CCMP683. Okadaic acid (OA) and its derivatives were not detected in CCMP683. OA was detected only in CCMP2804. Depletion of nitrate or phosphate increased the cellular concentration of OA, and repletion of nitrate or phosphate had no effect on the cellular concentration of OA. Correlation analysis indicated that the cellular concentration of OA was negatively correlated with cell density. Differences in the growth response to phosphate repletion and in the ability to produce OA suggest that the 2 strains may be good candidates for comparative studies related to phosphate metabolism and OA toxicity.

High Value Phycotoxins From the Dinoflagellate Prorocentrum

“…For example, all reported Prorocentrum lima strains produce OA and some strains also produce DTX1 as a minor toxin (Jackson et al, 1993;McLachlan et al, 1994;Vanucci et al, 2010;Varkitzi et al, 2010;Hoppenrath et al, 2013;Wang et al, 2015;Hou et al, 2016;Lee et al, 2016;Hoppenrath, 2017;Pan et al, 2017;Aquino-Cruz et al, 2018;Gu et al, 2019). Prorocentrum belizeanum, caipirignum, concavum, maculosum and hoffmannianum are also known producers of DSP toxins (Morton et al, 1994;Zhou and Fritz, 1994;Hoppenrath et al, 2013;López-Rosales et al, 2014;Luo et al, 2017;Accoroni et al, 2018;Rodríguez et al, 2018;Lim et al, 2019;Lee et al, 2020).…”

“…It has been speculated that the low chlorophyll a to carbon ratio is responsible for the slow growth of dinoflagellates (Tang, 1996) but the chlorophyll a content per unit mass of dinoflagellates is similar to diatoms (Gallardo- Rodríguez et al, 2012). Several studies have focused on small-scale cultures of benthic dinoflagellates to optimize growth rates and toxic production (Jackson et al, 1993;McLachlan et al, 1994;Morton et al, 1994;Yang et al, 2008;Zhong et al, 2008;Li et al, 2009;Vanucci et al, 2010;Varkitzi et al, 2010;López-Rosales et al, 2014;Wang et al, 2015;Hou et al, 2016;Accoroni et al, 2018;Aquino-Cruz et al, 2018;Gu et al, 2019;Lee et al, 2020). In a typical photosynthetic culture the maximum biomass concentration reached was well below 1 g/L and regarding phycotoxin production it is of the order of picograms (Gallardo- Rodríguez et al, 2012).…”

“…Then, a second growth phase (G2 phase) in which cells accumulate nutrients needed for the mitosis (M phase) and cytokinesis (Pan et al, 1999;Bhaud et al, 2000). The biosynthesis of phycotoxins typically varies during different growth phases, with the highest production rates during the end of the exponential phase prior entering the stationary phase (Pan et al, 1999;Jia et al, 2019;Lee et al, 2020). Circadian rhythms are also known to influence growth rates and biosynthesis of secondary metabolites (Jacob-Lopes et al, 2009;Jia et al, 2019).…”

“…The effects of key environmental factors (e.g., nutrients, temperature, salinity, and light availability) on the phycotoxin production are species dependent (Vanucci et al, 2010;Varkitzi et al, 2010;Wang et al, 2015;Aquino-Cruz et al, 2018;Gu et al, 2019;Lee et al, 2020). Nutrient limitation is the most common strategy used to boost phycotoxin production, however as a result of nutrient limitation cell growth usually declines.…”

“…Benthic Prorocentrum spp. has been cultured using nitrate, ammonium and urea (Table 2) (McLachlan et al, 1994;Pan et al, 1999;Zhong et al, 2008;Li et al, 2009;Varkitzi et al, 2010;Hou et al, 2016;Accoroni et al, 2018;Gu et al, 2019;Lee et al, 2020). Whereas some studies suggest that nitrogen concentration is directly proportional to the maximum cell density but not growth rate (Zhong et al, 2008;Vanucci et al, 2010;Hou et al, 2016), others found that it is directly proportional to both (McLachlan et al, 1994;Li et al, 2009).…”