TY  - JOUR
A1  - Spijkerman, Elly
A1  - Stojkovic, Slobodanka
A1  - Holland, Daryl
A1  - Lachmann, Sabrina C.
A1  - Beardall, John
T1  - Nutrient induced fluorescence transients (NIFTs) provide a rapid measure of P and C (co-)limitation in a green alga
JF  - European journal of phycology
N2  - Nutrient Induced Fluorescence Transients (NIFTs) have been shown to be a possible way of testing for the limiting nutrient in algal populations. In this study we tested the hypothesis that NIFTs can be used to detect a (co-)limitation for inorganic phosphorus (Pi) and CO2 in the green alga Chlamydomonas acidophila and that the magnitude of the NIFTs can be related to cellular P:C ratios. We show a co-limitation response for Pi and CO2 via traditional nutrient enrichment experiments in natural phytoplankton populations dominated by C. acidophila. We measured NIFT responses after a Pi- or a CO2-spike in C. acidophila batch cultures at various stages of Pi and inorganic C limitation. Significant NIFTs were observed in response to spikes in both nutrients. The NIFT response to a Pi-spike showed a strong negative correlation with cellular P:C ratio that was pronounced below 3 mmol P: mol C (equivalent to 0.2 pg P cell(-1)). Both cellular P and C content influenced the extent of the Pi-NIFT response. The NIFT response to a CO2-spike correlated to low CO2 culturing conditions and also had a negative correlation with cellular P content. A secondary response within the Pi-NIFT response was related to the CO2 concentration and potentially reflected co-limitation. In conclusion, NIFTs provided a quick and reliable method to detect the growth-limiting nutrient in an extremophile green alga, under Pi-, CO2- and Pi/CO2 (co-)limited growth conditions.
KW  - acidophile
KW  - Chlamydomonas
KW  - CO2 concentrating mechanism
KW  - CO2 limitation
KW  - extremophile
KW  - nutrient limitation
KW  - photosynthesis response
KW  - phytoplankton
KW  - stoichiometry
Y1  - 2016
U6  - https://doi.org/10.1080/09670262.2015.1095355
SN  - 0967-0262
SN  - 1469-4433
VL  - 51
SP  - 47
EP  - 58
PB  - Hindawi
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Spijkerman, Elly
A1  - Stojkovic, Slobodanka
A1  - Beardall, John
T1  - CO2 acquisition in Chlamydomonas acidophila is influenced mainly by CO2, not phosphorus, availability
JF  - Photosynthesis research
N2  - The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.4), where CO2 is the sole inorganic carbon source. Previous work has revealed that the species can accumulate inorganic carbon (Ci) and exhibits high affinity CO2 utilization under low-CO2 (air-equilibrium) conditions, similar to organisms with an active CO2 concentrating mechanism (CCM), whereas both processes are down-regulated under high CO2 (4.5 % CO2) conditions. Responses of this species to phosphorus (Pi)-limited conditions suggested a contrasting regulation of the CCM characteristics. Therefore, we measured external carbonic anhydrase (CA(ext)) activities and protein expression (CAH1), the internal pH, Ci accumulation, and CO2-utilization in cells adapted to high or low CO2 under Pi-replete and Pi-limited conditions. Results reveal that C. acidophila expressed CA(ext) activity and expressed a protein cross-reacting with CAH1 (the CA(ext) from Chlamydomonas reinhardtii). Although the function of this CA remains unclear, CA(ext) activity and high affinity CO2 utilization were the highest under low CO2 conditions. C. acidophila accumulated Ci and expressed the CAH1 protein under all conditions tested, and C. reinhardtii also contained substantial amounts of CAH1 protein under Pi-limitation. In conclusion, Ci utilization is optimized in C. acidophila under ecologically relevant conditions, which may enable optimal survival in its extreme Ci- and Pi-limited habitat. The exact physiological and biochemical acclimation remains to be further studied.
KW  - CO2 concentrating mechanism
KW  - Inorganic phosphorus limitation
KW  - Varying CO2 condition
KW  - Extremophilic green alga
KW  - Co-limitation
KW  - Internal pH
KW  - Inorganic carbon accumulation
KW  - Affinity for CO2 uptake
Y1  - 2014
U6  - https://doi.org/10.1007/s11120-014-0016-6
SN  - 0166-8595
SN  - 1573-5079
VL  - 121
IS  - 2-3
SP  - 213
EP  - 221
PB  - Springer
CY  - Dordrecht
ER  -