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1.
Yoval-Sánchez B Jasso-Chávez R Lira-Silva E Moreno-Sánchez R Rodríguez-Zavala JS 《Journal of bioenergetics and biomembranes》2011,43(5):519-530
Ethanol is one of the most efficient carbon sources for Euglena gracilis. Thus, an in-depth investigation of the distribution of ethanol metabolizing enzymes in this organism was conducted. Cellular
fractionation indicated localization of the ethanol metabolizing enzymes in both cytosol and mitochondria. Isolated mitochondria
were able to generate a transmembrane electrical gradient (Δψ) after the addition of ethanol. However, upon the addition of
acetaldehyde no Δψ was formed. Furthermore, acetaldehyde collapsed Δψ generated by ethanol or malate but not by D-lactate.
Pyrazole, a specific inhibitor of alcohol dehydrogenase (ADH), abolished the effect of acetaldehyde on Δψ, suggesting that
the mitochondrial ADH, by actively consuming NADH to reduce acetaldehyde to ethanol, was able to collapse Δψ. When mitochondria
were fractionated, 27% and 60% of ADH and aldehyde dehydrogenase (ALDH) activities were found in the inner membrane fraction.
ADH activity showed two kinetic components, suggesting the presence of two isozymes in the membrane fraction, while ALDH kinetics
was monotonic. The ADH Km values were 0.64–6.5 mM for ethanol, and 0.16–0.88 mM for NAD+, while the ALDH Km values were 1.7–5.3 μM for acetaldehyde and 33–47 μM for NAD+. These novel enzymes were also able to use aliphatic substrates of different chain length and could be involved in the metabolism
of fatty alcohol and aldehydes released from wax esters stored by this microorganism. 相似文献
2.
Abhinav Grover Jayashankar S. Yadav Ranjita Biswas Choppakatla S. S. Pavan Punita Mishra Virendra S. Bisaria Durai Sundar 《Plant Cell, Tissue and Organ Culture》2012,108(2):323-331
Cell suspension cultures of Camellia sinensis were established in 250 ml shake flasks. Flasks contained 50 ml liquid medium of either Murashige and Skoog (MS), N/5 MS
or Heller medium containing different levels of 6-benzyladenine (BA) (0.05–2 mg l−1), 2,4-dichlorophenoxyacetic acid (2,4-D) (1–10 mg l−1), and sucrose (10–50 g l−1). Moreover, the pH of the medium was varied from 5.2–6.2. In addition, cultures were subjected to light irradiation as well
as to complete darkness. Following optimization of aroma and terpenoid extraction methods, cell cultures were analyzed for
the volatile compounds using GC/MS. A total of 43 compounds were identified using the micro SDE apparatus. Among the major
monoterpenoids obtained were α-terpineol and nerol. Moreover, other high aroma-value compounds, including 2-ethyl hexanol,
benzyl alcohol, benzene acetaldehyde, nonanal and phenylethylalcohol were also detected. The highest levels of these compounds
were obtained from cell suspension cultures grown in MS medium containing 5 mg l−1 2,4-D, 1 mg l−1 BA and 30 g l−1 sucrose at pH of 5.8 with incubation in complete darkness. 相似文献
3.
Acetaldehyde is a known mutagen and carcinogen. Active aldehyde dehydrogenase (ALDH) represents an important mechanism for
acetaldehyde detoxification. A yeast strain XJ-2 isolated from grape samples was found to produce acetaldehyde dehydrogenase
with a high activity of 2.28 U/mg and identified as Issatchenkia terricola. The enzyme activity was validated by oxidizing acetaldehyde to acetate with NAD+ as coenzyme based on the headspace gas chromatography analysis. A novel acetaldehyde dehydrogenase gene (ist-ALD) was cloned by combining SiteFinding-PCR and self-formed adaptor PCR. The ist-ALD gene comprised an open reading frame of 1,578 bp and encoded a protein of 525 amino acids. The predicted protein of ist-ALD showed the highest identity (73%) to ALDH from Pichia angusta. The ist-ALD gene was expressed in Escherichia coli, and the gene product (ist-ALDH) presented a productivity of 442.3 U/mL cells. The purified ist-ALDH was a homotetramer of
232 kDa consisting of 57 kDa-subunit according to the SDS-PAGE and native PAGE analysis. Ist-ALDH exhibited the optimal activity
at pH 9.0 and 40°C, respectively. The activity of ist-ALDH was enhanced by K+, NH4+, dithiothreitol, and 2-mercaptoethanol but strongly inhibited by Ag+, Hg2+, Cu2+, and phenylmethyl sulfonylfluoride. In the presence of NAD+, ist-ALDH could oxidize many aliphatic, aromatic, and heterocyclic aldehydes, preferably acetaldehyde. Kinetic study revealed
that ist-ALDH had a k
cat value of 27.71/s and a k
cat/K
m value of 26.80 × 103/(mol s) on acetaldehyde, demonstrating ist-ALDH, a catalytically active enzyme by comparing with other ALDHs. These studies
indicated that ist-ALDH was a potential enzymatic product for acetaldehyde detoxification. 相似文献
4.
A medicinal mushroom, Phellinus linteus, was successfully cultivated using a cheese-processing waste, whey, and the optimal bioconversion conditions for the maximum
mycelial growth rate was also estimated through solid-state cultivation experiments. Response surface analysis with a face-centered
design (center point replication = 5) was applied to statistically approximate the simultaneous effects of the three variables,
i.e., substrate concentration (10–30 g lactose l−1), temperature (20–30°C), and pH (4–6), on the mycelial growth rate of P. linteus. The following is a partial cubic model where η is the mycelial growth rate (K
r
) and x
k
is the corresponding variable term (k = substrate concentration, temperature, and pH in order): η = −23.8 + 8.67 × 10−2
x
1 + 1.48x
2 + 1.77x
3 + 8.00 × 10−4
x
1
x
2 + 7.25 × 10−2
x
1
x
3 + 5.13 × 10−2
x
2
x
3 −1.28 × 10−2
x
12 –3.18 × 10−2
x
22. −2.64 × 10−1
x
32 −3.28 × 10−3
x
1
x
2
x
3 + 4.68 × 10−4
x
12
x
2. The produced response surface model proved to be significant (r
2 > 0.99, P-value <0.0001, coefficient of variation <5%) to describe the explored space. Temperature was found to be the most significant
factor of dominant effects on the mycelial growth rate, and other variables such as temperature2, pH, pH2, and (substrate concentration2 × temperature) also showed significant effects on the model output. The maximum mycelial growth rate was predicted to be
2.80 mm d−1 at 29.7 g lactose l−1, 26.2°C, and pH 5. Our results proved a good potential of whey to serve as an alternative growth medium for cultivating P. linteus mycelia. This may provide another potential for managing this nutrient-rich waste in a cost-effective way. 相似文献
5.
6.
Copper (II) complex of formulation [Cu–Phen–Tyr](H2O)](ClO4) (Phen = 1,10-phenanthroline, l-Tyr = l-tyrosine), has been prepared, and their induced DNA oxidative cleavage activity studied. The complex binds to DNA by intercalation,
as deduced from the absorption and fluorescence spectral data. Scatchard plots constructed from the absorption titration data
gave binding constant 2.44 × 104 M−1 of base pairs. Extensive hypochromism, broadening, and red shifts in the absorption spectra were observed. Upon binding to
DNA, the fluorescence from the DNA–ethidium bromide system was efficiently quenched by the copper (II) complex. Stern–Volmer
quenching constant 0.61 × 103 M−1 obtained from the linear quenching plots. [Cu–Phen–Tyr] complex efficiently cleave the supercoiled DNA to its nicked circular
form with gallic acid as biological reductant at appropriate complex concentration. The gallic acid as reductant could observably
improve copper (II) complex to DNA damage. The pseudo-Michaelis–Menten kinetic parameters (k
cat, K
M) were calculated to be 1.32 h−1 and 5.46 × 10−5 M for [Cu–Phen–Tyr] complex. Mechanistic studies reveal the involvement of superoxide anions and hydroxyl radical (HO·) as the reactive species under an aerobic medium. 相似文献
7.
SMAD7 has been demonstrated to antagonize TGF-β-mediated fibrosis, carcinogenesis, and inflammation. Two previous genome-wide
association studies identified three single nucleotide polymorphisms (SNPs) (rs4939827, rs12953717 and rs4464148) in SMAD7 to be associated with colorectal cancer in a Western population. We conducted the first case–control study in a Han Chinese
population to explore the associations between these three SNPs and colorectal, gastric, and lung cancers. Of the three SNPs,
only rs12953717 was strongly associated with the three types of cancer, fitting the overdominant model. Compared with the
CC/TT (CC combined with TT) genotype, the adjusted odds ratios for the CT genotype were 2.002 (95% CI, 1.250–3.207, P = 0.004), 1.678 (95% CI, 1.048–2.689, P = 0.031), 3.825 (95% CI, 2.310–6.335, P < 1 × 10−4), and 2.294 (95% CI, 1.537–3.343, P < 1 × 10−4), respectively, for colorectal, gastric, lung, and combined cancers. These outcomes suggest that rs12953717 is a common risk
marker of these three types of cancer in the Han Chinese. 相似文献
8.
A Bacillus sp., capable of degrading chloroform, was immobilized in calcium alginate. The beads in 20 g alginate l−1 (about 2 × 108 cells/bead) could be re-used nine times for degradation of chloroform at 40 μM. The immobilized cells had a higher range
of tolerance (pH 6.5–9 and 20–41°C) than free cells (pH 7–8.5 and 28–32°C). At 5 g alginate l−1, leakage of the cells from the beads was 0.51 mg dry wt ml−1. This species is the first reported Bacillus that can degrade chloroform as the sole carbon source. 相似文献
9.
Recent studies have identified common variants in or near GC, CYP2R1 and NADSYN1/DHCR7 to be associated with 25-hydroxyvitamin D [25(OH)D] levels in European populations. We aimed to examine whether these variants
also influence 25(OH)D levels in Chinese. Seven common variants were successfully genotyped and tested for associations with
plasma 25(OH)D levels in a population-based cohort of 3,210 Chinese Hans from Beijing and Shanghai. Six common variants at
GC (rs4588, rs7041, rs2282679 and rs1155563) and NADSYN1/DHCR7 (rs3829251 and rs1790349) loci were all significantly associated with lower plasma 25(OH)D levels (−0.036 ≤ β ≤ −0.076 per risk-allele, P ≤ 5.7 × 10−5), while CYP2R1-rs2060793 showed a trend toward association with 25(OH)D levels in the Shanghai subpopulation (P = 0.08), but not in the Beijing subpopulation (P = 0.82). Haplotype-based association analyses of the four GC variants showed that only the haplotype that contained all risk-alleles (TACC) was significantly associated with lower plasma
25(OH)D levels (β = −0.085, P = 2.3 × 10−9), while the haplotype containing the risk-alleles of rs4588 and rs2282679 (TATC) was marginally associated with lower 25(OH)D
levels (β = −0.054, P = 0.0562) when compared with GCTA haplotype carrying the four protective alleles. Most notably, conditional analyses showed
that only GC-rs4588 and GC-rs2282679 (r
2 = 0.97) remained significantly associated with 25(OH)D concentrations (P ≤ 1.9 × 10−5) after adjusting for the other two SNPs in GC. In conclusion, GC and NADSYN1/DHCR7 loci individually and collectively contribute to variation in plasma vitamin D levels in Chinese Hans. 相似文献
10.
Han Gil Choi Ki Hoon Lee Hyun Il Yoo Pil Jun Kang Young Sik Kim Ki Wan Nam 《Journal of applied phycology》2008,20(5):729-735
The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance
(10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m−2s−1) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m−2s−1), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day−1 (25°C, 20 μmol photons m−2s−1) and 13% day−1 (8 h daylength). In contrast, the RGRs of the blade weights were 4% day−1 (15°C, 20 μmol photons m−2s−1) and 5% day−1 (12 h daylength). Negative growth rates were found at 20 μmol photons m−2s−1 of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m−2s−1, and 8 h daylength for construction of Sargassum beds and restoration of barren areas. 相似文献
11.
Irzykowska L Bocianowski J Waśkiewicz A Weber Z Karolewski Z Goliński P Kostecki M Irzykowski W 《Journal of applied genetics》2012,53(2):237-247
Thirty single-spore isolates of a toxigenic fungus, Fusarium oxysporum, were isolated from asparagus spears and identified by species-specific polymerase chain reaction (PCR) and translation elongation
factor 1-α (TEF) sequence analysis. In the examined sets of F. oxysporum isolates, the DNA sequences of mating type genes (MAT) were identified. The distribution of MAT idiomorph may suggest that MAT1-2 is a predominant mating type in the F. oxysporum population. F. oxysporum is mainly recognised as a producer of moniliformin—the highly toxic secondary metabolite. Moniliformin content was determined
by high-performance liquid chromatography (HPLC) analysis in the range 0.05–1,007.47 μg g−1 (mean 115.93 μg g−1) but, also, fumonisin B1 was detected, in the concentration range 0.01–0.91 μg g−1 (mean 0.19 μg g−1). There was no association between mating types and the mycotoxins biosynthesis level. Additionally, a significant intra-species
genetic diversity was revealed and molecular markers associated with toxins biosynthesis were identified. 相似文献
12.
A thorough understanding of the reproductive phenology of introduced species is crucial for effective management and control.
Undaria pinnatifida is an invasive macroalga from the Northwest Pacific which has been recently introduced into three countries in the Southern
Hemisphere: Australia, New Zealand and Argentina. Reproductive phenological studies in Port Phillip Bay, Australia, were undertaken
and compared with other populations in the Southern Hemisphere, especially with those from Tasmania which were suspected to
be very different. The growth season began earlier in Port Phillip Bay than in Tasmanian populations, and abundance was higher.
Growth rates were lower in Port Phillip Bay, but this might be due to the different morphology of both populations. The maximum
spore release competency of U. pinnatifida in Port Phillip Bay was 12.1 × 105 spores cm−2 h−1 which is 20 times the maximum obtained in Tasmania (0.6 × 105 spores cm−2 h−1). For most of the growth season, spore release competency ranged between 2 and 3 × 105 spores cm−2 h−1, 3–5 times more than in Tasmania. Undaria pinnatifida has not been established outside Port Phillip Bay in continental Australia, but a precautionary approach should be undertaken
in order to avoid further spread. Monitoring for early detection and removal of immature sporophytes prior to spore release
seem to be the best options. This monitoring should be continuous since new recruits may appear throughout the growth season
(April–February) and it should be combined with informative programmes to reduce the chances of spread. 相似文献
13.
Simultaneous measurements of chlorophyll (Chl) fluorescence and CO2 assimilation (A) in Vicia faba leaves were taken during the first weeks of growth to evaluate the protective effect of 24-epibrassinolide (EBR) against
damage caused by the application of the herbicide terbutryn (Terb) at pre-emergence. V. faba seeds were incubated for 24 h in EBR solutions (2 × 10−6 or 2 × 10−5 mM) and immediately sown. Terb was applied at recommended doses (1.47 or 1.96 kg ha−1) at pre-emergence. The highest dose of Terb strongly decreased CO2 assimilation, the maximum quantum yield of PSII photochemistry in the dark-adapted state (F
V/F
M), the nonphotochemical quenching (NPQ), and the effective quantum yield (ΔF/F′M) during the first 3–4 weeks after plant emergence. Moreover, Terb increased the basal quantum yield of nonphotochemical processes
(F
0/F
M), the degree of reaction center closure (1 − q
p), and the fraction of light absorbed in PSII antennae that was dissipated via thermal energy dissipation in the antennae
(1 − F′V/F′M). The herbicide also significantly reduced plant growth at the end of the experiment as well as plant length, dry weight,
and number of leaves. The application of EBR to V. faba seeds before sowing strongly diminished the effect of Terb on fluorescence parameters and CO2 assimilation, which recovered 13 days after plant emergence and showed values similar to those of control plants. The protective
effect of EBR on CO2 assimilation was detected at a photosynthetic photon flux density (PFD) of 650 μmol m−2 s−1 and the effect on ΔF/F′M and photosynthetic electron transport (J) was detected under actinic lightings up to 1750 μmol m−2 s−1. The highest dose of EBR also counteracted the decrease in plant growth caused by Terb, and plants registered the same growth
values as controls. 相似文献
14.
The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile
suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm
agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved
CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic
carboxydotrophic species. 相似文献
15.
Kim HT Ko HJ Kim N Kim D Lee D Choi IG Woo HC Kim MD Kim KH 《Biotechnology letters》2012,34(6):1087-1092
A gene, alg7D, from Saccharophagus degradans, coding for a putative alginate lyase belonging to the family of polysaccharide lyase-7, was overexpressed in Escherichia coli. The properties of the recombinant Alg7D were characterized. The enzyme endolytically depolymerized alginate by β-elimination
into oligo-alginates with degrees of polymerization of 2–5. Its activity was maximal at 50°C and pH 7 and was slightly increased
in the presence of Na+. The K
M
, V
max
, k
cat
, and k
cat
/K
M
values were: 3 mg ml−1, 6.2 U mg−1, 1.9 × 10−2 s−1, and 6.3 × 10−3 mg−1 ml s−1, respectively. 相似文献
16.
Mulligan CJ Robin RW Osier MV Sambuughin N Goldfarb LG Kittles RA Hesselbrock D Goldman D Long JC 《Human genetics》2003,113(4):325-336
Enzymes encoded by two gene families, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), mediate alcohol metabolism in humans. Allelic variants have been identified that alter metabolic rates and influence risk for alcoholism. Specifically, ADH1B*47His
(previously ADH2-2) and ALDH2-2 have been shown to confer protection against alcoholism, presumably through accumulation of acetaldehyde in the blood and a resultant 'flushing response' to alcohol consumption. In the current study, variants at ADH1B
(previously ADH2), ADH1C (previously ADH3), and
ALDH2 were assayed in DNA extracts from participants belonging to a Southwest American Indian tribe (n=490) with a high prevalence of alcoholism. Each subject underwent a clinical interview for diagnosis of alcohol dependence, as well as evaluation of intermediate phenotypes such as binge drinking and flushing response to alcohol consumption. Detailed haplotypes were constructed and tested against alcohol dependence and related intermediate phenotypes using both association and linkage analysis. ADH and ALDH variants were also assayed in three Asian and one African population (no clinical data) in order to provide an evolutionary context for the haplotype data. Both linkage and association analysis identified several ADH1C alleles and a neighboring microsatellite marker that affected risk of alcohol dependence and were also related to binge drinking. These data strengthen the support for
ADH as a candidate locus for alcohol dependence and suggest further productive study. 相似文献
17.
Brain serotonin (5-HT) modulates the neural effects of ethanol. In the present study, we investigated the changes in 5-HT
level, 5-HT2A receptor binding and aldehyde dehydrogenase (ALDH) activity in brain stem and liver of ethanol treated rats and 5-HT2A regulation on ALDH in hepatocyte cultures in vitro. The 5-HT content in the brain stem and liver significantly decreased
with an increased 5-HIAA/5-HT ratio in the ethanol treated rats compared to control. Scatchard analysis of [3H] (±)2,3-dimethoxyphenyl-1-[2-(-4-piperidine)-methanol] [3H] MDL 100907 against ketanserin in brain stem of ethanol treated rats showed a significant increase in B
max without any change in K
d compared to control. The competition curve for [3H] MDL 100907 against ketanserin fitted one-site model in both control and ethanol treated rats with unity as Hill slope value.
A significant increase in V
max of ALDH activity in liver and a significant decrease in K
m in liver and brain stem of ethanol treated rats compared to control was observed. In 24 h culture studies, an increase in
enzyme activity was observed in cells in medium with 10% ethanol. The elevated ALDH activity in ethanol treated cells was
reversed to control level in presence of 10−5 and 10−7 M 5-HT. Ketanserin, an antagonist of 5-HT2A, reversed the effect of 5HT on 10% ethanol induced ALDH activity in hepatocytes. Our results showed that there was a decreased
5-HT content with an enhanced 5-HT2A receptor and aldehyde dehydrogenase activity in the brain stem of alcohol treated rats and in vitro hepatocyte cultures.
The enhanced ALDH activity in ethanol supplemented hepatocytes was reversed to control level in presence of 10−5 and 10−7 M 5-HT. 相似文献
18.
Atsushi Nanami 《Ichthyological Research》2011,58(4):310-314
The ornate jobfish Pristipomoides argyrogrammicus is an important lutjanid species for fisheries in the Okinawan region of Japan. The present study estimated the size composition
and reproduction of this species in the waters around Ishigaki Island, Okinawa Prefecture. The length–frequency distribution
indicated that males grow larger than females. The fork length (FL; mm)–whole body weight (BW; g) relationship and FL–total
length (TL) relationship were as follows: BW = 1.048 × 10−5 FL3.121 and TL = 1.101 × FL + 2.196, respectively. The main spawning season was estimated as between April and August, since higher
gonadosomatic index (GSI) values were found for both sexes, and matured oocytes were observed in females during these months.
The developmental stage of ovaries correlated with the GSI of females. Fecundity ranged from 9,530 to 98,260 oocytes in fish
of 177.0 to 278.0 mm FL, and the FL–fecundity relationship was as follows: fecundity = 9.525 × 10−8 FL4.903. 相似文献
19.
Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment
and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m−2 s−1 with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105,
130 μmol photons m−2 s−1) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C
for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into
disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m−2 s−1, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m−2 s−1, whilst it was 80–130 μmol photons m−2 s−1 for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis. 相似文献
20.
We investigated the effects of limiting (1.96 × 10−9 mol l−1 total Cu, corresponding to pCu 14.8; where pCu = −log [Cu2+]) and toxic Cu concentrations up to 8.0 × 10−5 mol l−1 total Cu (equivalent to pCu 9.5) on growth rates and photosynthetic activity of exponentially grown Phaeocystis cordata, using batch and semi-continuous cultures. With pulse amplitude modulated (PAM) fluorometry, we determined the photochemical
response of P. cordata to the various Cu levels, and showed contrasting results for the batch and semi-continuous cultures. Although maximum photosystem
II (PSII) quantum yield (ΦM) was optimal and constant in the semi-continuous P. cordata, the batch cultures showed a significant decrease in ΦM with culture age (0–72 h). The EC50 for the batch cultures was higher (2.0 × 10−10 mol l−1, pCu9.7), than that for the semi-continuous cultures (6.3 × 10−11 mol l−1, pCu10.2). The semi-continuous cultures exhibited a systematic and linear decrease in ΦM as Cu levels increased (for [Cu2+] < 1.0 × 10−12 mol l−1, pCu12.0), however, no effect of high Cu was observed on their operational PSII quantum yield (Φ′M). Similarly, semi-continuous cultures exhibited a significant decrease in ΦM, but not in Φ′M, because of low-Cu levels. Thus, Cu toxicity and Cu limitation damage the PSII reaction centers, but not the processes downstream
of PSII. Quenching mechanisms (NPQ and Q
n) were lower under high Cu relative to the controls, suggesting that toxic Cu impairs photo-protective mechanisms. PAM fluorometry
is a sensitive tool for detecting minor physiological variations. However, culturing techniques (batch vs. semi-continuous)
and sampling time might account for literature discrepancies on the effects of Cu on PSII. Semi-continuous culturing might
be the most adequate technique to investigate Cu effects on PSII photochemistry. 相似文献