自养和兼养条件下蛋白核小球藻昼夜节律的响应

【目的】研究自养和兼养两种培养方式对蛋白核小球藻(Chlorella pyrenoidosa)生长、细胞分裂和生化组分积累的影响,探讨人工培养蛋白核小球藻的昼夜节律响应机制和优化技术。【方法】小球藻自养培养采用BG11培养基,兼养培养基在BG11培养基中添加4种不同浓度(1、5、10、20 g/L)的葡萄糖,培养周期为10 d。血球板计数法测定藻细胞浓度,干重法测定藻细胞生物量。显微观察藻细胞大小和分裂情况。脂染色法测定小球藻总脂的含量,藻细胞的叶绿素、蛋白和淀粉分别采用甲醇、氢氧化钠、硝酸钙浸提后通过紫外分光光度法定量测定。【结果】葡萄糖兼养培养对蛋白核小球藻具有显著的促生长效应,最适浓度为10 g/L。10 d收获时,兼养组(10 g/L葡萄糖)藻细胞浓度和干重分别是自养组的2.57倍和6.73倍。分析一昼夜中的藻细胞增殖规律可知,第2天和第5天时自养组中增殖的新生子细胞约有76.00%在黑暗期分裂产生,而兼养组中第2天和第5天光照期的新细胞增殖量占比分别达到40.90%和67.50%。一昼夜内藻细胞大小的迁移动态监测表明,第2天自养组藻细胞的体积变化静息期为8 h,兼养组只有4 h;第5天两组藻细胞大小迁移动态的昼夜节律明显,但兼养组黑暗结束后较大细胞(D6μm)占比显著高于自养组。第8天时,兼养组藻细胞已处于稳定期,总脂和蛋白含量均显著高于自养组,藻细胞总脂和色素含量在一昼夜中相对稳定,但蛋白和淀粉含量分别在光照8 h和12 h左右达到峰值。从第2天开始,对兼养组细胞每天进行2 h光延长,收获时藻细胞浓度和干重分别比对照组提高13%和11%。【结论】葡萄糖兼养培养能大幅提高蛋白核小球藻的生物量。蛋白核小球藻生长增殖与生化组分积累均受昼夜节律调控,自养条件下藻细胞以光照期生长黑暗期增殖为主。兼养培养提高藻细胞生物量的机制在于缩短藻细胞生长静息期,在昼夜节律中加速藻细胞生长并显著提高通过细胞周期检查点的细胞比例,光照期效应尤其明显。藻细胞蛋白和淀粉含量昼夜节律明显,最佳收获时间分别在光照8 h和12 h后。     

Das rhythmische Verhalten einer farblosen Mutante von Euglena gracilis

Summary A colorless mutant of Euglena gracilis shows a cireadian rhythmic mobility in darkness just as mixotrophic and autotrophic green forms do.Therefore the obligatory heterotrophic form is very suitable for testing to what extent the rhythmic behavior of the mixotrophic cells, in contrast to that of the autotrophic cells, is independent of photosynthesis.Like the green cells, the colorless cells are synchronized by a single transient from light to dark. About 12 hours after the beginning of the darkness the rhythmic mobility of the colorless cells attains the first maximum, whereas the green forms both show their first maximum 18 hours after the end of the light period, which is much more advantageous for a photosynthesizing organism.The free running period seems to be dependent on the temperature during anaerobic glycolysis and independent of temperature during respiration, just as it has been recently found out in the case of green forms. The type of energy supply changes with the age of the cultures.Respiration has no significance as energy source for the rhythm which continues under pure glycolytic conditions.A sudden increase of the constant temperature does not shift the phase. The same is true in the case of mixotrophic cells but not in the case of autotrophic cells. However, the rhythm is often first suppressed for several days.A lowering of the temperature is followed by two or three transients with about half the frequency, but it does not influence the phase as far as it can be extrapolated. The same has been shown to be true in the case of mixotrophic cells.The rhythmic behavior of the heterotrophic cells is very similar to that of the mixotrophic ones. However, the heterotrophic cells are very sensitive to changes in temperature, which are more compensated for in the mixotrophic cells, apparently by photosynthesis.     

Effects of light and temperature on the growth of Takayama helix (Dinophyceae): mixotrophy as a survival strategy against photoinhibition

Takayama helix is a mixotrophic dinoflagellate that can feed on diverse algal prey. We explored the effects of light intensity and water temperature, two important physical factors, on its autotrophic and mixotrophic growth rates when fed on Alexandrium minutum CCMP1888. Both the autotrophic and mixotrophic growth rates and ingestion rates of T. helix on A. minutum were significantly affected by photon flux density. Positive growth rates of T. helix at 6–58 μmol photons · m^?2 · s^?1 were observed in both the autotrophic (maximum rate = 0.2 · d^?1) and mixotrophic modes (0.4 · d^?1). Of course, it did not grow both autotrophically and mixotrophically in complete darkness. At ≥247 μmol photons · m^?2 · s^?1, the autotrophic growth rates were negative (i.e., photoinhibition), but mixotrophy turned these negative rates to positive. Both autotrophic and mixotrophic growth and ingestion rates were significantly affected by water temperature. Under both autotrophic and mixotrophic conditions, it grew at 15–28°C, but not at ≤10 or 30°C. Therefore, both light intensity and temperature are critical factors affecting the survival and growth of T. helix.     

Biomass production in mixotrophic culture of Euglena gracilis under acidic condition and its growth energetics

When Euglena gracilis was grown in the heterotrophic condition with glucose and (NH₄)₂SO₄ as the carbon and nitrogen source, a high cell yield (4.28–4.48 g l^–1) was obtained and the culture pH decreased to 1.6–2. The biomass production in the heterotrophic culture was compared to those in the autotrophic and mixotrophic cultures. Autotrophic growth was 4.7–6.3% of the heterotrophic one, whereas about 15–19% higher growth was obtained in the mixotrophic culture. Moreover, good production of chlorophyll (39.4 mg l^–1) and carotenoids (13.8 mg l^–1) were attained in the mixotrophic culture, giving the highest fermenter productivity with respect to biomass as well as chlorophyll and carotenoids. Through an energetic analysis in the mixotrophic culture, it was estimated about 25–28% of the total ATP requirement is formed in the photochemical reactions. This resulted in an improved biomass production in the mixotrophic culture of E. gracilis.     

Temperature Dependency of Circadian Period in a Single Cell (Acetabularia)

The circadian rhythm in the oxygen production of 30 individual Acetabularia cells has been studied at different temperatures. The temperature induced period variation was continuously evaluated over the whole data record of each individual cell with an advanced spectral analysis technique. The observed circadian periods of O₂ production displayed a well established region of temperature compensation between 25 °C and 30 °C with a Q₁₀, value of 0.9, whereas between 15°C and 22°C a positive temperature coefficient was measured (Q₁₀ at 22 °C 0.9, Q₁₀ at 20°C 0.8, Q₁₀at 17°C 0.7).     

Mixotrophic organisms become more heterotrophic with rising temperature

The metabolic theory of ecology predicts that temperature affects heterotrophic processes more strongly than autotrophic processes. We hypothesized that this differential temperature response may shift mixotrophic organisms towards more heterotrophic nutrition with rising temperature. The hypothesis was tested in experiments with the mixotrophic chrysophyte Ochromonas sp., grown under autotrophic, mixotrophic and heterotrophic conditions. Our results show that (1) grazing rates on bacterial prey increased more strongly with temperature than photosynthetic electron transport rates, (2) heterotrophic growth rates increased exponentially with temperature over the entire range from 13 to 33 °C, while autotrophic growth rates reached a maximum at intermediate temperatures and (3) chlorophyll contents during mixotrophic growth decreased at high temperature. Hence, the contribution of photosynthesis to mixotrophic growth strongly decreased with temperature. These findings support the hypothesis that mixotrophs become more heterotrophic with rising temperature, which alters their functional role in food webs and the carbon cycle.     

SPONTANEOUS AND STIMULATED BIOLUMINESCENCE OF THE DINOFLAGELLATE CERATOCORYS HORRZDA (PERIDINIALES)1

This is the first report of spontaneous bioluminescence in the autotrophic dinoflagellate Ceratocorys horrida von Stein. Bioluminescence was measured, using an automated data acquisition system, in a strain of cultured cells isolated from the Sargasso Sea. Ceratocorys horrida is only the second dinoflagellate species to exhibit rhythmicity in the rate of spontaneous flashing, flash quantum flux (intensity), and level of spontaneous glowing. The rate of spontaneous flashing was maximal during hours 2–4 of the dark phase [i.e. circadian time (CT)16–18 for a 14:10 h LD cycle (LD14:10)], with approximately 2% of the population flashing-min^?1, a rate approximately one order of magnitude greater than that of the dinoflagellate Gonyaulax polyedra. Flash quantum flux was also maximal during this period. Spontaneous flashes were 134 ms in duration with a maximum flux (intensity) of 3.1×10⁹ quanta-s^?1. Light emission presumably originated from blue fluorescent microsources distributed in the cell periphery and not from the spines. Values of both spontaneous flash rate and maximum flux were independent of cell concentration. Isolated cells also produced spontaneous flashes. Spontaneous glowing was dim except for a peak of 6.4× 10⁴quanta-s^?1 cell^?1, which occurred at CT22.9 for LD14:10 and at CT22.8 for LD12:12. The total integrated emission of spontaneous flashing and glowing during the dark phase was 4×10⁹ quantacell^?1, equivalent to the total stimulable luminescence. The rhythms for C. horrida flash and glow behavior were similar to those of Gonyaulax polyedra, although flash rate and quantum flux were greater. Spontaneous bioluminescence in C. horrida may be a circadian rhythm because it persisted for at least three cycles in constant dark conditions. This is also the first detailed study of the stimulated bioluminescence of C. horrida, which also displayed a diurnal rhythm. Cultures exhibited >200 times more mechanically stimulated bioluminescence during the dark phase than during the light phase. Mechanical stimulation during the dark phase resulted in 6.7 flashes. cell^?1; flashes were brighter and longer in duration than spontaneous flashes. Cruise-collected cells exhibited variability in quantum flux with few differences in flash kinetics. The role of dinoflagellate spontaneous bioluminescence in the dynamics of near-surface oceanic communities is unknown, but it may be an important source of natural in situ bioluminescence.     

川中丘陵区冬水田种植模式转旱作土壤呼吸组分特征及碳平衡

冬水田-水稻是川中丘陵区传统的稻田种植模式,冬水田种植模式转变是实现多熟种植及机械化的重要途径。为探究冬水田-水稻种植模式转旱作过程中作物季及休闲期土壤呼吸速率及其组分构成,试验设置冬水田-水稻转旱作(FTD)、冬水田-水稻(FR)和冬闲田-玉米(FM)3种不同种植模式,采用根排除法和静态明箱-气相色谱法原位取样测定作物季及季后休闲期土壤呼吸及其组分,并通过测算净生态系统生产力(NEP)进而判断冬水田-水稻转旱作过程的农田系统碳汇强度。结果表明:(1)FTD显著提高了土壤总呼吸速率及其自养和异养呼吸速率,从而提高了其累积排放量(P<0.05)。与FR相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了13.14倍、11.32倍和15.56倍(P<0.05);与FM相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了70.56%、40.83%和115.47%(P<0.05)。(2)与FR和FM相比,FTD均降低了土壤呼吸及其组分的温度敏感性(Q₁₀),且土壤总呼吸的温度敏感性介于异养呼吸和自养呼吸之间。(3)FR,FM和FTD的净生态系统生产力(NEP)均为正值,其数值分别为7911.66 kg/hm²,5667.89 kg/hm²和1583.46 kg/hm²,均表现为大气CO₂的碳汇,但与FR与FM相比,FTD显著降低了其净生态系统生产力,呈现出较弱的碳汇。     

Protein Synthesis in Euglena gracilis is Light-and Temperature-Dependent,Oscillating in a Circadian,Temperature-Compensated Manner

Abstract: Incorporation of radiolabelled amino acids into proteins of Euglena gracilis revealed that the amount of labelled protein depends on the conditions of illumination and temperature of cultivation. Protein synthesis was generally lower under dark conditions except at 37 °C. The largest amounts of labelled protein were measured at 21 °C and decreased at higher and lower temperatures. By separating the labelled proteins of the membraneous cell fraction from subcultures under a range of culture conditions, the synthesis of some specific proteins was found to be light- and/or temperature-dependent. On incubating cells taken at different times during a light/dark cycle and under constant conditions, a circadian rhythm of ³⁵S-methionine- as well as ³⁵S-cysteine-incorporation was detected. Thereby the cells incorporated ten-times less cysteine than methionine. Protein synthesis always peaked during the last quarter of the daily light phase, confirming the rhythmic rise in total protein. The length of the rhythm period, approximately 24 h, was nearly independent of the applied temperature in the range of 16 to 27 °C.     

Effects of light-dark cycles on the circadian conidiation rhythm inNeurospora crassa

The effects of 24 hr light-dark cycles on the circadian conidiation rhythm inNeurospora crassa were compared among will-typefrq ⁺ and clock mutantsfrq ⁺,frq ³,frq ⁷,frq ⁹ andfrq ¹¹. The minimum length of the light period necessary for complete entrainment to the light-dark cycles was almost 2 hr infrq ⁺,frq ³ andfrq ⁷ strains. The minimum duration of the dark period necessary for the appearance of circadian conidiation was almost 4 hr in all of the strains except thefrq ¹¹ strain. The phase of the conidiation rhythm was dependent on the light to dark transition in thefrq ¹ strain in all light-dark cycles examined and in thefrq ⁺ andfrq ³ strains when the light period was shorter than 16 hr. In contrast, the phase of thefrq ⁷ strain was dependent on the light to dark transition when the light period was shorter than 10 hr.     

Reassessment of the bioenergetic yield of Arthrospira platensis using continuous culture

Reassessement of bioenergetic growth yield of Arthrospira platensis was performed by using continuous culture under both autotrophic and mixotrophic conditions. Continuous culture was carried out at dilution rates of 0.017, 0.023 and 0.030 h^–1. Under these dilution rates bioenergetic yields ranged between 4.45–6.03 × 10^–3 g biomass kJ^–1 and between 5.42–7.46 × 10^–3 g biomass kJ^–1, under autotrophic and mixotrophic conditions respectively. A maximum bioenergetic yield of 8.1 × 10^–3 g biomass kJ^–1 using an autotrophic culture can be calculated. Pigment accumulation (chlorophyll a and carotenoids) may be related to light irradiance, reaching a maximum pigment concentration under light saturation irradiance. Phycocyanin concentration increased during light limitation.     

Reduced inorganic sulfur oxidation supports autotrophic and mixotrophic growth of Magnetospirillum strain J10 and Magnetospirillum gryphiswaldense

Magnetotactic bacteria are present at the oxic–anoxic transition zone where opposing gradients of oxygen and reduced sulfur and iron exist. Growth of non‐magnetotactic lithoautotrophic Magnetospirillum strain J10 and its close relative magnetotactic Magnetospirillum gryphiswaldense was characterized in microaerobic continuous culture. Both strains were able to grow in mixotrophic (acetate + sulfide) and autotrophic (sulfide or thiosulfate) conditions. Autotrophically growing cells completely converted sulfide or thiosulfate to sulfate and produced 7.5 g dry weight per mol substrate at a maximum observed growth rate of 0.09 h^?1 for strain J10 and 0.07 h^?1 for M. gryphiswaldense. The respiratory activity for acetate was repressed in autotrophic and also in mixotrophic cultures, suggesting acetate was used as C‐source in the latter. We have estimated the proportions of substrate used for assimilatory processes and evaluated the biomass yields per mol dissimilated substrate. The yield for lithoheterotrophic growth using acetate as the C‐source was approximately twice the autotrophic growth yield and very similar to the heterotrophic yield, showing the importance of reduced sulfur compounds for growth. In the draft genome sequence of M. gryphiswaldense homologues of genes encoding a partial sulfur‐oxidizing (Sox) enzyme system and reverse dissimilatory sulfite reductase (Dsr) were identified, which may be involved in the oxidation of sulfide and thiosulfate. Magnetospirillum gryphiswaldense is the first freshwater magnetotactic species for which autotrophic growth is shown.     

Growth and Carbohydrate Metabolism of Sulfobacilli

The moderately thermophilic acidophilic bacteria Sulfobacillus thermosulfidooxidans, strain 1269, S. thermosulfidooxidanssubsp. asporogenes, strain 41, and the thermotolerant strain S. thermosulfidooxidanssubsp. thermotolerans K1 prefer mixotrophic growth conditions (the concomitant presence of ferrous iron, thiosulfate, and organic compounds in the medium). In heterotrophic and autotrophic growth conditions, these sulfobacilli can grow over only a few culture transfers. In cell-free extracts of these sulfobacilli, key enzymes of the Embden–Meyerhof–Parnas, pentose-phosphate, and Entner–Doudoroff pathways were found. The role of a particular pathway depended on the cultivation conditions. All of the enzymes assayed were most active under mixotrophic conditions in the presence of Fe²⁺and glucose, suggesting the operation of all of the three major pathways of carbohydrate metabolism under these conditions. However, the operation of the Entner–Doudoroff pathway in strain 41 was restricted under mixotrophic conditions. After the first culture transfer from mixotrophic to heterotrophic conditions, the utilization of glucose occurred only via the Embden–Meyerhof–Parnas and Entner–Doudoroff pathways. After the first culture transfer from mixotrophic to autotrophic conditions, the activity of carbohydrate metabolism enzymes decreased in all of the strains studied; in strain K1, only the glycolytic pathway remained operative. The high activity of fructose-bisphosphate aldolase, remaining in strain 41 cells under these conditions, suggests the involvement of this enzyme in the reactions of the Calvin cycle or of gluconeogenesis.     

Investigation of mixotrophic,heterotrophic, and autotrophic growth of Chlorella vulgaris under agricultural waste medium

Growth of Chlorella vulgaris and its lipid production were investigated under autotrophic, heterotrophic, and mixotrophic conditions. Cheap agricultural waste molasses and corn steep liquor from industries were used as carbon and nitrogen sources, respectively. Chlorella vulgaris grew remarkably under this agricultural waste medium, which resulted in a reduction in the final cost of the biodiesel production. Maximum dry weight of 2.62 g L^?1 was obtained in mixotrophic growth with the highest lipid concentration of 0.86 g L^?1. These biomass and lipid concentrations were, respectively, 140% and 170% higher than autotrophic growth and 300% and 1200% higher than heterotrophic growth. In mixotrophic growth, independent or simultaneous occurrence of autotrophic and heterotrophic metabolisms was investigated. The growth of the microalgae was observed to take place first heterotrophically to a minimum substrate concentration with a little fraction in growth under autotrophic metabolism, and then the cells grew more autotrophically. It was found that mixotrophic growth was not a simple combination of heterotrophic and autotrophic growth.     

Growth characteristics of the cyanobacterium Nostoc flagelliforme in photoautotrophic, mixotrophic and heterotrophic cultivation

Nostoc flagelliforme is a terrestrial cyanobacterium with high economic value. Dissociated cells separated from a natural colony of N. flagelliforme were cultivated for 7 days under either phototrophic, mixotrophic or heterotrophic culture conditions. The highest biomass, 1.67 g L⁻¹ cell concentration, was obtained under mixotrophic culture, representing 4.98 and 2.28 times the biomass obtained in phototrophic and heterotrophic cultures, respectively. The biomass in mixotrophic culture was not the sum as that in photoautotrophic and heterotrophic cultures. During the first 4 days of culture, the cell concentration in mixotrophic culture was lower than the sum of those in photoautotrophic and heterotrophic cultures. However, from the 5th day, the cell concentration in mixotrophic culture surpassed the sum of those obtained from the other two trophic modes. Although the inhibitor of photosynthetic electron transport DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea] efficiently inhibited autotrophic growth of N. flagelliforme cells, under mixotrophic culture they could grow by using glucose. The addition of glucose changed the response of N.flagelliforme cells to light. The maximal photosynthetic rate, dark respiration rate and light compensation point in mixotrophic culture were higher than those in photoautotrophic cultures. These results suggest that photoautotrophic (photosynthesis) and heterotrophic (oxidative metabolism of glucose) growth interact in mixotrophic growth of N. flagelliforme cells.     

CIRCADIAN GROWTH RHYTHM IN JUVENILE SPOROPHYTES OF LAMINARIALES (PHAEOPHYTA)1

A circadian rhythm in growth was detected by computer-aided image analysis in 3–4-cm-long, juvenile sporophytes of the kelp species Pterygophora California Rupr. and in seven Laminaria spp. In P. californica, the free-running rhythm occurred in continuous white fluorescent light, had a period of 26 h at 10°or 15°C, and persisted for at least 2 weeks in white or blue light. The rhythm became insignificant in continuous green or red light after 3 cycles. Synchronization by white light-dark regimes, e.g. by 16 h light per day, resulted in an entrained period of 24 h and in a shift of the circadian growth minimum into the middle of the light phase. A morning growth peak represented the decreasing portion of the circadian growth curve, and an evening peak the increasing portion. The circadian growth peak was not visible during the dark phase, because growth rate decreased immediately after the onset of darkness. At night, some growth still occurred at 16 or 12 h light per day, whereas growth stopped completely at 8 h light per day, as in continuous darkness. During 11 days of darkness, the thallus area became reduced by 3.5%, but growth rate recovered in subsequent light–dark cycles, and the circadian growth rhythm reappeared in subsequent continuous light.     

Remarks on mixotrophic and autotrophic carbon nutrition of Vitis plantlets cultured in vitro

Two Vitis species were cultured in vitro under photoautrophic (sucrose-free culture medium) and photomixotrophic (sucrose 15 g l^-1) conditions during the period following microcutting rooting (day 34 to day 120). Several parameters were measured at the end of the culture: growth, plant dry weight, carbohydrate uptake from the medium and rates of photosynthesis and dark respiration. The two species behaved very differently. Under photoautotrophic conditions, dark respiration, net photosynthesis and daily CO₂ fixation were higher in Vitis vinifera than in Vitis rupestris. Culture under mixotrophic conditions caused increase in growth, respiration and photosynthesis in Vitis rupestris. In contrast, photosynthesis decreased in Vitis vinifera under the same conditions.     

Microbial processes and temperature in Chesapeake Bay: current relationships and potential impacts of regional warming

The importance of temperature in regulating physiological processes is without question; however, the interpretation of the relationship between temperature and ecological data is much more complicated. Consequently, it is difficult to decide how the nature of the temperature response terms should be included in models used to predict responses of microbial processes to increasing regional temperature. This analysis compiles several years of data from a research programme conducted in Chesapeake Bay, in an effort to examine how individual microbial processes ? as well as the balance between autotrophy and heterotrophy ? have responded to temperature, and to predict changes in microbial trophic state based on realistic increases in global temperature. The upper boundary on all of the pelagic microbial rate processes that were measured could be described remarkably well as a linear function of temperature, although there was substantial scatter in the data. Pelagic microbial rate processes (e.g. phytoplankton production, respiration, bacterial productivity) showed a remarkably constrained range of Q₁₀ values from 1.7 to 3.4. The one notable exception to this was nitrogen uptake in the North and Mid Bay, which exhibited Q₁₀ values < 1.0. Proxies for phytoplankton biomass (e.g. chlorophyll) were largely independent of temperature while bacterial abundance was significantly related to temperature and was found to have a Q₁₀ of 1.88. Using these individual temperature responses, the balance of autotrophy and heterotrophy was assessed by calculating the community photosynthesis to respiration (P:R), NH₄⁺ uptake to regeneration (U:R) and phytoplankton to bacterial productivity (PP:BP) ratios for current conditions (all ratios) and for a 2 and 5 °C temperature increase (NH₄⁺ U:R excluded). The NH₄⁺ U:R ratio stayed remarkable constant at ～1 over the entire temperature range supporting the importance of regenerative processes to nitrogen availability even during periods of heavy allochthonous inputs. These elevated temperature calculations for P:R and PP:BP suggest that the magnitude of autotrophic production during the spring bloom may decrease with increased regional temperature and, as a consequence, the Chesapeake Bay might become net heterotrophic on an annual timescale. These calculations should be considered with caution, but nonetheless demonstrate that the impact of increasing temperature on the balance of autotrophic and heterotrophic processes needs to be researched further.     

Complex interaction between circadian rhythm and diet on bile acid homeostasis in male rats

Desynchronization between the master clock in the brain, which is entrained by (day) light, and peripheral organ clocks, which are mainly entrained by food intake, may have negative effects on energy metabolism. Bile acid metabolism follows a clear day/night rhythm. We investigated whether in rats on a normal chow diet the daily rhythm of plasma bile acids and hepatic expression of bile acid metabolic genes is controlled by the light/dark cycle or the feeding/fasting rhythm. In addition, we investigated the effects of high caloric diets and time-restricted feeding on daily rhythms of plasma bile acids and hepatic genes involved in bile acid synthesis. In experiment 1 male Wistar rats were fed according to three different feeding paradigms: food was available ad libitum for 24 h (ad lib) or time-restricted for 10 h during the dark period (dark fed) or 10 h during the light period (light fed). To allow further metabolic phenotyping, we manipulated dietary macronutrient intake by providing rats with a chow diet, a free choice high-fat-high-sugar diet or a free choice high-fat (HF) diet. In experiment 2 rats were fed a normal chow diet, but food was either available in a 6-meals-a-day (6M) scheme or ad lib. During both experiments, we measured plasma bile acid levels and hepatic mRNA expression of genes involved in bile acid metabolism at eight different time points during 24 h. Time-restricted feeding enhanced the daily rhythm in plasma bile acid concentrations. Plasma bile acid concentrations are highest during fasting and dropped during the period of food intake with all diets. An HF-containing diet changed bile acid pool composition, but not the daily rhythmicity of plasma bile acid levels. Daily rhythms of hepatic Cyp7a1 and Cyp8b1 mRNA expression followed the hepatic molecular clock, whereas for Shp expression food intake was leading. Combining an HF diet with feeding in the light/inactive period annulled CYp7a1 and Cyp8b1 gene expression rhythms, whilst keeping that of Shp intact. In conclusion, plasma bile acids and key genes in bile acid biosynthesis are entrained by food intake as well as the hepatic molecular clock. Eating during the inactivity period induced changes in the plasma bile acid pool composition similar to those induced by HF feeding.