Lag Phase Of Cells Research Articles

Higher sensitivity to Cu2+ exposure of Microcystis aeruginosa in late lag phase is beneficial to its control

Cyanobacterial blooms are always treated in exponential phase, which demands high dosages of algicides (e.g., CuSO4). Actually, cyanobacterial blooms in late lag phase exhibit low cell-density and specific physiological/biochemical characteristics, implying the possibility of controlling blooms in a more efficient and economical way with CuSO4 treatment if cyanobacterial cells in late lag phase can be treated. In this study, the outbreakof a Microcystis bloom was simulated, and Microcystis samples in late lag and exponential phases were treated with CuSO4. The results showed that M. aeruginosa in late lag phase had a higher ratio of dividing-cells, Fv/Fm and intracellular total organic carbon content (TOC) than that in exponential phase, indicating that its metabolic activity was vigorous. M. aeruginosa in late lag phase could more easily be blocked, since a higher decrease in chlorophyll-a, Fv/Fm and membrane integrity occurred under the same dosages of CuSO4 exposure compared to M. aeruginosa in exponential phase. Meanwhile, microcystin release in late lag phase was less than that in exponential phase. Moreover, higher sensitivity in late lag phase was confirmed at the individual level, as the photosynthesis related genes psaB and rbcL were more down-regulated than those in exponential phase. In general, cyanobacteria in late lag phase exhibited higher sensitivity to CuSO4, indicating that CuSO4 treatments in late lag phase can achieve a higher control efficiency and fewer release of microcystin with low-dosages algicide. Hence, it is a more environmentally friendly strategy to control cyanobacterial blooms than the traditional strategy applied in exponential phase.

Visualization and Quantification of Genetically Adapted Microbial Cells During Preculture

As culture history is known to affect the length of the lag phase and microbial cell growth, precultures are often grown in the same medium as the main culture for physiological adaptation and to reduce a prolonged lag time in some microbial cells. To understand the adaptation process of microbial cells during transfer from Luria–Bertani medium to minimal medium, we used the growth of Escherichia coli BL21(DE3) in succinate minimal medium as a model system. We observed that only one or two sequential transfers from minimal medium to fresh minimal medium accelerated the growth rate of BL21(DE3) cells. In addition, the number of large colonies (diameter ≥0.1 cm) on succinate agar increased with the number of transfers. Genome and transcript analyses showed that the C-to-T point mutation in large colony cells converted the inactive promoter of kgtP (known to encode α-ketoglutarate permease) to the active form, allowing efficient uptake of exogenous succinate. Moreover, we visualized the occurrence of genetically adapted cells with better fitness in real time and quantified the number of those cells in the microbial population during transfer to the same medium. Fluorescence microscopy showed the occurrence and increase of adapted mutant cells, which contain intracellular KgtP-fused green fluorescent proteins, as a result of the C-to-T mutation in the promoter of a fused kgtP–sfgfp during transfer to fresh medium. Flow cytometry revealed that the proportion of mutant cells increased from 1.75% (first transfer) to 12.16% (second transfer) and finally 70.79% (third transfer), explaining the shortened lag time and accelerated growth rate of BL21(DE3) cells during adaptation to the minimal medium. This study provides new insights into the genetic heterogeneity of microbial populations that aids microbial adaptability in new environments.

Effects of Different Coagulants on Coagulation Process for Removal of Microcystis aeruginosa

The effects of different coagulants on coagulation process for algal removal were investigated with the laboratory scale to obtain data for their influence to drinking water treatment processes. Aluminum sulfate, which is the most commonly used for coagulation process in the world, and two other polymer coagulants, poly aluminum chloride and poly aluminum chloride silicate, were used to check coagulation efficiencies for algae removal. Microcystis aeruginosa, one of cyanobacteria and main species during waterbloom in worldwide, were selected and prepared their cells in each growth phase for coagulation tests. Coagulation inhibitions were shown for cells in log-growth phase as well as stationary phase in which periods algae cells might be most active, especially, when using poly aluminum chloride and poly aluminum chloride silicate. On the other hand, coagulation efficiencies were high with all coagulants for cells in lag phase as well as death phase. As result of the research, although polymer coagulants are generally known as better ones than aluminum sulfate, aluminum sulfate should be used during waterbloom rather than polymer coagulants such as poly aluminum chloride and poly aluminum chloride silicate since the most of algae cells during waterbloom may be in the log-growth phase and/or lag phase.

Survival and Growth of Wild-Type and rpoS-Deficient Salmonella Newport Strains in Soil Extracts Prepared with Heat-Treated Poultry Pellets

Manure runoff can transfer pathogens to farmlands or to water sources, leading to subsequent contamination of produce. Untreated biological soil amendments, like manure, can be contaminated with foodborne pathogens, such as Salmonella Newport, which may lead to transfer of the pathogen to fruits or vegetables. Studies have reported the occurrence and survival of Salmonella in manure or manure slurries. However, data on the survival and growth of Salmonella Newport is lacking in matrices simulating runoff. We quantified the survival and growth of wild-type (WT) Salmonella Newport and rpoS-deficient (Δ rpoS) strains in sterile and nonsterile soil extracts prepared with (amended) or without (unamended) heat-treated poultry pellets at 25°C. Salmonella Newport WT and Δ rpoS populations reached a maximum cell density of 6 to 8 log CFU/mL in 24 to 30 h in amended and unamended soil extracts and remained in stationary phase for up to 4 days. Salmonella Newport in amended soil extracts exhibited a decreased lag phase (λ , 2.87 ± 1.01 h) and greater maximum cell densities ( Nmax, 6.84 ± 1.25 CFU/mL) compared with λ (20.10 ± 9.53 h) and Nmax (5.22 ± 0.82 CFU/mL) in unamended soil extracts. In amended soil extract, the Δ rpoS strain had no measurable λ , similar growth rates (μmax) compared with WT, and a lower Nmax compared with the WT strain. Unamended, nonsterile soil extracts did not support the growth of Salmonella Newport WT and led to a decline in populations for the Δ rpoS strain. Salmonella Newport had lower cell densities in nonsterile soil extracts (5.94 ± 0.95 CFU/mL) than it did in sterile soil extracts (6.66 ± 1.50 CFU/mL), potentially indicating competition for nutrients between indigenous microbes and Salmonella Newport. The most favorable growth conditions were provided by amended sterile and nonsterile soil extracts, followed by sterile, unamended soil extracts for both Salmonella Newport strains. Salmonella Newport may grow to greater densities in amended extracts, providing a route for increased Salmonella levels in the growing environments of produce.

Resveratrol production by grapevine cells in fed-batch bioreactor: Experiments and modelling

The purpose of this work was to scale-up the culture of grapevine cells (Vitis labrusca) from shake-flasks (100 mL) to a 5L stirred bioreactor in order to develop a model able to describe the bioproduction of resveratrol under the controlled conditions of a fed-batch culture. For this study, the biomass, resveratrol and sugar concentrations as well as pH and dissolved oxygen were monitored daily. The experiments were conducted twice over a three month period. The culture was elicited during the exponential growth phase with methyl jasmonate, leading the cells to exhibit a complex behaviour during the resveratrol production phase. A model of the system behaviour involving simple mechanisms is proposed and successfully confronted to the experimental results. This model demonstrates that the system dynamic can be decomposed into four phases: a lag phase (cell growth slowing down), a starting phase (beginning of resveratrol production), a surge phase (significant resveratrol production accompanied by significant cell death) and a stationary phase. Thus, we were able to successfully scale-up resveratrol production from 100 mL flasks to 5L bioreactors.

Photodynamic damage predominates on different targets depending on cell growth phase of Candida albicans

Photodynamic inactivation (PDI) has been reported to be effective to eradicate a wide variety of pathogens, including antimicrobial-resistant microorganisms. The aim of this study was to identify the potential molecular targets of PDI depending on growth phase of Candida albicans. Fungal cells in lag (6h) and stationary (48h) phases were submitted to PDI mediated by methylene blue (MB) combined with a (662±21) nm-LED, at 360mW of optical power. Pre-irradiation time was 10min and exposure times were 12min, 15min and 18min delivering radiant exposures of 129.6J/cm2, 162J/cm2 and 194.4J/cm2, respectively, on a 24-well plate of about 2cm2 at an irradiance of 180mW/cm2. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force spectroscopy (AFS) and Fourier transform infrared spectroscopy (FT-IR) were employed to evaluate the photodynamic effect in young and old fungal cells following 15min of irradiation. Morphological analysis revealed wrinkled and shrunk fungal cell membrane for both growth phases while extracellular polymeric substance (EPS) removal was only observed for old fungal cells. Damaged intracellular structures were more pronounced in young fungal cells. The surface nanostiffness of young fungal cells decreased after PDI but increased for old fungal cells. Cellular adhesion force was reduced for both growth phases. Fungal cells in lag phase predominantly showed degradation of nucleic acids and proteins, while fungal cells in stationary phase showed more pronounced degradation of polysaccharides and lipids. Taken together, our results indicate different molecular targets for fungal cells in lag and stationary growth phase following PDI.

Phase-dependent dynamics of the lac promoter under nutrient stress

To survive, a bacterial population must sense nutrient availability and adjust its growth phase accordingly. Few studies have quantitatively analyzed the single-cell behavior of stress and growth phase-related transcriptional changes in Escherichia coli. To investigate the dynamic changes in transcription during different growth phases and starvation, we analyzed the single-cell transcriptional dynamics of the E. coli lac promoter. Cells were grown under different starvation conditions, including glucose, magnesium, phosphate and thiamine limitations, and transcription dynamics was quantified using a single RNA detection method at different phases. Differences in gene expression over conditions and phases indicate that stochasticity in transcription dynamics is directly connected to cell phase and availability of nutrients. Except for glucose, the pattern of transcription dynamics under all starvation conditions appears to be similar. Transcriptional bursts were more prominent in lag and stationary phase cells starved for energy sources. Identical behavior was observed in exponential phase cells starved for phosphate and thiamine. Noise measurements under all nutrient exhaustion conditions indicate that intrinsic noise is higher than extrinsic noise. Our results, obtained in a relA1 mutational background, which led to suboptimal production of ppGpp, suggest that the single-cell transcriptional changes we observed were largely ppGpp-independent. Taken together, we propose that, under different starvation conditions, cells are able to decrease the trend in cell-to-cell variability in transcription as a common means of adaptation.

Performance evaluation of the anammox hybrid reactor seeded with mixed inoculum sludge

ABSTRACTLong startup and poor granulation are the major bottlenecks in field-scale application of the anammox (ANaerobic AMMonium OXidation) process. In the present study, the anammox process was investigated in a modified anammox hybrid reactor (AHR) inoculated with mixed seed culture (anoxic and activated sludge). The startup study delineated four distinct phases, i.e. cell lysis, lag phase, activity elevation and stationary phase. Use of mixed seed culture at influent ratio (1:1) and hydraulic retention time (HRT) of 1 d led to early startup of the anammox process. The removal efficiencies of and during acclimation were found to be 94.3% and 96.4%, respectively, at nitrogen loading rate (NLR) of 0.35 kg N/m3 d. Pearson correlation analysis dictated strong and positive correlation of HRT and sludge retention time (SRT) with nitrogen removal efficiency (NRE) while NLR and sludge loading rate (SLR) were negatively correlated. Attached growth system (AGS) in AHR contributed an additional 11% ammonium removal and reduced the sludge washout rate by 29%. Mass balance of nitrogen revealed that the major fraction (74.1%) of input nitrogen was converted into N2 gas indicating higher substrate conversion efficiency of anammox biomass. Scanning electron microscope (SEM) study of biomass indicated the presence of heterogeneous population of cocci and rod-shaped bacteria of average diameter varying from 1.2 to 1.5 mm. Owing to the features of early start-up, ability to retain high biomass and consistently higher NRE, hybrid reactor configuration seeded with mixed culture offers noble strategy for cultivation of well-compacted anammox granules for field-scale installation.

Intensive DNA Replication and Metabolism during the Lag Phase in Cyanobacteria.

Unlike bacteria such as Escherichia coli and Bacillus subtilis, several species of freshwater cyanobacteria are known to contain multiple chromosomal copies per cell, at all stages of their cell cycle. We have characterized the replication of multi-copy chromosomes in the cyanobacterium Synechococcus elongatus PCC 7942 (hereafter Synechococcus 7942). In Synechococcus 7942, the replication of multi-copy chromosome is asynchronous, not only among cells but also among multi-copy chromosomes. This suggests that DNA replication is not tightly coupled to cell division in Synechococcus 7942. To address this hypothesis, we analysed the relationship between DNA replication and cell doubling at various growth phases of Synechococcus 7942 cell culture. Three distinct growth phases were characterised in Synechococcus 7942 batch culture: lag phase, exponential phase, and arithmetic (linear) phase. The chromosomal copy number was significantly higher during the lag phase than during the exponential and linear phases. Likewise, DNA replication activity was higher in the lag phase cells than in the exponential and linear phase cells, and the lag phase cells were more sensitive to nalidixic acid, a DNA gyrase inhibitor, than cells in other growth phases. To elucidate physiological differences in Synechococcus 7942 during the lag phase, we analysed the metabolome at each growth phase. In addition, we assessed the accumulation of central carbon metabolites, amino acids, and DNA precursors at each phase. The results of these analyses suggest that Synechococcus 7942 cells prepare for cell division during the lag phase by initiating intensive chromosomal DNA replication and accumulating metabolites necessary for the subsequent cell division and elongation steps that occur during the exponential growth and linear phases.

Evaluation of the molecular mechanisms of bacterial resistance in Pseudomonas aeruginosa by FTIR microspectroscopy

Evaluation of the molecular mechanisms of bacterial resistance in Pseudomonas aeruginosa by FTIR microspectroscopy

Effect of photodynamic therapy on fluconazole-resistant Candida albicans adhesion ability

Effect of photodynamic therapy on fluconazole-resistant Candida albicans adhesion ability

Antifungal effect of Trachyspermum ammi against susceptible and fluconazole-resistant strains of Candida albicans

Trachyspermumammi (T.ammi) has been known as having many therapeutic properties and its antimicrobial activity has currently received a renewed interest. This study aimed to verify the effectiveness of T.ammi essential oil to inhibit the growth of Candida albicans (C.albicans) strains isolated from HIV(+) patients with oropharyngeal candidiasis (OPC). The essential oil was obtained by hydrodistillation in a Clevenger apparatus and analyzed by gas chromatography. Susceptibility tests were expressed as inhibition zone by the disk diffusion method and minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) by the broth microdilution method. Thymol (63.4%), p-cymene (19%) and γ-terpinen (16.9%) were found as the most abundant constituents. The disk diffusion results revealed that 67% of oral C.albicans isolates were susceptible, 9% susceptible-dose dependent and 24% resistant to fluconazole. In the broth microdilution method, 68% of isolates were susceptible, 5% susceptible-dose dependent and 27% resistant to fluconazole. The increase in concentration led to a significant reduction in yeasts that were growing in exponential phase. In addition, with increasing in T.ammi oil concentration, the time of remaining cells in lag phase was significantly increased. This study showed that all clinical C.albicans isolates were susceptible to T.ammi essential oil, indicating a significant reduction in the yeast growth in exponential phase.

Toxicidade de herbicidas utilizados na cultura da cana-de-açúcar à bactéria diazotrófica Herbaspirillum seropedicae

The objective of this work was to identify herbicides used in the sugarcane crop that affects neither the growth, the development, of nor the process of biological nitrogen fixation (BNF) by the diazotrophic bacterium Herbaspirillum seropedicae. Eighteen herbicides (paraquat, ametryne, tebuthiuron, amicarbazone, diuron, metribuzin, [hexazinone + diuron], [hexazinone + clomazone], clomazone, isoxaflutole, sulfentrazone, oxyfluorfen, imazapic, imazapyr, [trifloxysulfuron sodium + ametryne], glyphosate, MSMA e 2,4-D) were tested in their respective commercial doses regarding their impact on the growth of the bacteria in liquid medium DIGs. For this, we determined the duration of lag phase, generation time and maximum cell density of H. seropedicae, calculated from optical density data obtained at regular intervals during the incubation of cultures for 33 h at 32oC. We also evaluated the impact of herbicides on nitrogenase activity of H. seropedicae grown in semi-solid N-free JNFb medium. The effects of herbicides on the growth variables and the ARA were compared with the untreated control by Dunnett test. A completely randomized design was used. The herbicides paraquat, imazapyr, ametryne, glyphosate and oxyfluorfen inhibited the growth of H. seropedicae in vitro. Ametryne, oxyfluorfen and glyphosate caused a small reduction in the duration of the lag phase of diazotrophic bacteria H. seropedicae. Oxyfluorfen, ametryne and imazapyr resulted in increased the generation time by H. seropedicae. Glyphosate promoted drastic reduction in biological nitrogen fixation in vitro by H. seropedicae. The other tested herbicides did not affect the growth or the same BNF by H. seropedicae.

Listeria monocytogenes Serotype 1/2b and 4b Isolates from Human Clinical Cases and Foods Show Differences in Tolerance to Refrigeration and Salt Stress

Control of Listeria monocytogenes in food processing facilities is a difficult issue because of the ability of this microorganism to form biofilms and adapt to adverse environmental conditions. Survival at high concentrations of sodium chloride and growth at refrigeration temperatures are two other important characteristics of L. monocytogenes isolates. The aim of this study was to compare the growth characteristics under stress conditions at different temperatures of L. monocytogenes serotypes responsible for the majority of clinical cases from different sources. Twenty-two L. monocytogenes isolates, 12 from clinical cases (8 serotype 4b and 4 serotype 1/2a) and 10 from food (6 serotype 4b and 4 serotype 1/2a), and an L. monocytogenes Scott A (serotype 4b) reference strain were analyzed for the ability to grow in brain heart infusion broth plus 1.9 M NaCl (11%) at 4, 10, and 25°C for 73, 42, and 15 days, respectively. The majority of L. monocytogenes strains was viable or even grew at 4°C and under the high osmotic conditions usually used to control pathogens in the food industry. At 10°C, most strains could adapt and grow; however, no significant difference (P > 0.05) was found for lag-phase duration, maximum growth rate, and maximum cell density. At 25°C, all strains were able to grow, and populations increased by up 5 log CFU/ml. Clinical strains had a significantly longer lag phase and lower maximum cell density (P < 0.05) than did food strains. Regarding virulence potential, no significant differences in hemolytic activity were found among serotypes; however, serotype 4b strains were more invasive in Caco-2 cells than were serotype 1/2a strains (P < 0.05). The global tendency of decreasing NaCl concentrations in processed foods for health reasons may facilitate L. monocytogenes survival and growth in these products. Therefore, food companies must consider additional microbial growth barriers to assure product safety.

Cytotoxic diterpenes from roots of Crossopetalum gaumeri, a Celastraceae species from Yucatan Peninsula

Four new diterpenes, crossogumerins A–D (1–4) along with six known ones (5–10) were isolated from the root bark of Crossopetalum gaumeri, an endemic medicinal plant from the Yucatan Peninsula. Their structures were elucidated on the basis of 1D and 2D NMR techniques, including HMQC, HMBC, and ROESY experiments. Compounds 1–5, 8–10 were evaluated for cytotoxicity against HeLa (carcinoma of the cervix) and Hep-2 (lung carcinoma) human tumor cells lines and against normal Vero cells (African green monkey kidney) in lag and log phase of growth. Podocarpane diterpenes, crossogumerin B (2) and nimbiol (10), exhibited the highest activity against HeLa cells (IC50 values of 3.1 and 8.1μM, respectively), but also selectivity on Vero cells (SI 22.6 and 7.5, respectively). The preliminary SAR studies suggest that an epoxy moiety in ring B and a hydrogen bond-donor group strategically positioned in the diterpene core are important requirements for cytotoxicity and selectivity.

Tolerância da bactéria diazotrófica Gluconacetobacter diazotrophicus a herbicidas utilizados na cultura da cana-de-açúcar

The objective of this work was to identify herbicides used in the sugarcane crop that affects neither the growth of nor the process of biological nitrogen fixation (BNF) by the diazotrophic bacterium Gluconacetobacter diazotrophicus. Eighteen herbicides (paraquat, ametryne, amicarbazone, diuron, metribuzin, [hexazinone + diuron], [hexazinone + clomazone], clomazone, isoxaflutole, sulfentrazone, oxyfluorfen, imazapic, imazapyr, [trifloxysulfuron sodium + ametryne], s-metolachlor, glyphosate, MSMA e 2.4-D) were tested in their respective commercial doses. For this, we determined the duration of lag phase, generation time and maximum cell density of G. diazotrophicus. We also evaluated the impact of herbicides on nitrogenase activity of G. diazotrophicus measured by the technique of acetylene reduction assay. Diuron, metribuzin, 2.4-D and MSMA caused a small reduction in maximum growth of G. diazotrophicus in vitro. Amicarbazone, [hexazinone + clomazone] and clomazone showed some bacteriostatic effect on G. diazotrophicus. Treatments containing the herbicide paraquat and glyphosate resulted inhibitory effect on BFN by G. diazotrophicus.

Partitioning studies of l-glutaminase production by Bacillus cereus MTCC 1305 in different PEG–salt/dextran

Partitioning studies of l-glutaminase production by Bacillus cereus MTCC 1305 was carried out in different PEG–salt/PEG–dextran system. The partitioning value of l-glutaminase increased with increasing molecular weight of PEG from 2000–4000kDa and decreased with higher molecular weight of 6000kDa. Phase system of PEG 4000 (8.5%)/dextran T500 (9.5%) was selected for the extractive fermentative production of l-glutaminase on the basis maximum partition coefficient (1.31). The production of l-glutaminase was found higher in top phase of ATPS (2.09U/ml) than control media (1.42U/ml). Overall production of l-glutaminase (1.83U/ml) was found lower than top phase (2.09U/ml) in ATPS system. The growth profile with short lag phase and higher cell concentration was obtained for ATPS. The partition coefficient of l-glutaminase increased with increase of system pH and temperature and optimum production was obtained at pH 7.5 and temperature 30°C in top phase of PEG 4000/dextran T500 system.

Toxicidade de inseticidas utilizados na cultura da cana-de-açúcar à bactéria diazotrófica Herbaspirillum seropedicae

Although sugarcane crop responds to nitrogen fertilization, especially in sugarcane ratoon, the use of mineral sources of N is one of the factors of great economic impact in sugarcane production. Studies indicate that the use of diazotrophic bacteria can supply part of the need of nitrogen for this crop. The objective of this study was to identify pesticides used in the cultivation of sugarcane that do not affect the growth or cause harm to the ability of biological nitrogen fixation (BNF) of the diazotrophic bacterium Herbaspirillum seropedicae. Five insecticides (imidacloprid, fipronil, thiamethoxam, endosulfan and carbofuran) were tested in their respective commercial doses regarding their impact on bacteria growth. The parameters analyzed were duration of the lag phase, generation time and maximum cell density. The impact of pesticides on the nitrogenase activity of H. seropedicae grown in semi-solid medium was also assessed. Endosulfan and carbofuran hindered the growth of diazotrophic bacteria H. seropedicae, but did not reduce the BNF in vitro. Carbofuran increased the generation time and reduced the lag phase duration of H. seropedicae. Endosulfan increased its lag phase duration. Imidacloprid, fipronil and thiamethoxam did not cause any toxic effects to the growth and BNF in vitro of the diazotrophic bacteria H. seropedicae.

Localization Pattern of Conjugation Machinery in a Gram-Positive Bacterium

Conjugation is an efficient way for transfer of genetic information between bacteria, even between highly diverged species, and a major cause for the spreading of resistance genes. We have investigated the subcellular localization of several conserved conjugation proteins carried on plasmid pLS20 found in Bacillus subtilis. We show that VirB1, VirB4, VirB11, VirD2, and VirD4 homologs assemble at a single cell pole, but also at other sites along the cell membrane, in cells during the lag phase of growth. Bimolecular fluorescence complementation analyses showed that VirB4 and VirD4 interact at the cell pole and, less frequently, at other sites along the membrane. VirB1 and VirB11 also colocalized at the cell pole. Total internal reflection fluorescence microscopy showed that pLS20 is largely membrane associated and is frequently found at the cell pole, indicating that transfer takes place at the pole, which is a preferred site for the assembly of the active conjugation apparatus, but not the sole site. VirD2, VirB4, and VirD4 started to localize to the pole or the membrane in stationary-phase cells, and VirB1 and VirB11 were observed as foci in cells resuspended in fresh medium but no longer in cells that had entered exponential growth, although at least VirB4 was still expressed. These data reveal an unusual assembly/disassembly timing for the pLS20 conjugation machinery and suggest that specific localization of conjugation proteins in lag-phase cells and delocalization during growth are the reasons why pLS20 conjugation occurs only during early exponential phase.

Enhancing hypericin production of Hypericum perforatum cell suspension culture by ozone exposure

Accumulation of secondary metabolites is one of the common reactions of plants to ozone exposure in nature. To investigate the effect of ozone on the production of desired compounds of plant cell cultures, we assayed hypericin production of Hypericum perforatum suspension cell cultures treated with different doses of ozone at different culture phases. The results show that hypericin contents of the cells treated with 60 to 180 nL L(-1) ozone are significantly higher than those of the control, showing that ozone exposure may stimulate hypericin synthesis. Hypericin production of the cells treated with ozone at exponential phase is higher than that of lag and stationary phase, which suggests that exponential phase cell cultures are more responsive to ozone exposure than lag and stationary phase cells. The highest hypericin production is obtained by the cells exposed to 90 nL L(-1) ozone at late exponential phase for 3 h, being about fourfold of the control.