Nutritional and Other Aspects of Fruit-body Production in Pure Cultures of Collybia velutipes (Curt.) Fr.

Fruit-body production of Collybia velutipes on a synthetic mediumconsisting of minerals, asparagine, sucrose, and vitamin B₁has been studied. Compared with others tested this medium favouredfructification rather than mycelium growth. Primordia aroseon culturea between pH 5•2 and 7•2 approximately.Relatively low initial concentration of asparagine, high initialconcentration of sucrose, and increases in volume (without essentialincrease of the air interface) of media resulted in enhanceddry weights of sporophore crops. These factors variously affectedmycelium yields and the times of primordium production. Detailsof growth, sporophore production, maximum yield, and changesin the medium are given.     

The Influence of Ultra-Violet Light upon the Growth of Animals

A diketopiperazine derivative isolated from the soy-bean meal hydrolysates, AMINOSAN-EKI, has been proved as l-isoleucyl-l-valine anhydride by elemental analysis, melting point, and by paper chromatography. l-Isoleucyl-l-valine anhydride must be derived from the dipeptide produced by hydrolysis of the proteins.     

Production of NO and N(inf2)O by Pure Cultures of Nitrifying and Denitrifying Bacteria during Changes in Aeration

Peak emissions of NO and N(inf2)O are often observed after wetting of soil. The reactions to sudden changes in the aeration of cultures of nitrifying and denitrifying bacteria with respect to NO and N(inf2)O emissions were compared to obtain more information about the microbiological aspects of peak emissions. In continuous culture, the nitrifier Nitrosomonas europaea and the denitrifiers Alcaligenes eutrophus and Pseudomonas stutzeri were cultured at different levels of aeration (80 to 0% air saturation) and subjected to changes in aeration. The relative production of NO and N(inf2)O by N. europaea, as a percentage of the ammonium conversion, increased from 0.87 and 0.17%, respectively, at 80% air saturation to 2.32 and 0.78%, respectively, at 1% air saturation. At 0% air saturation, ammonium oxidation and N(inf2)O production ceased but NO production was enhanced. Coculturing of N. europaea with the nitrite oxidizer Nitrobacter winogradskyi strongly reduced the relative levels of NO and N(inf2)O production, probably as an effect of the lowered nitrite concentration. After lowering the aeration, N. europaea produced large short-lasting peaks of NO and N(inf2)O emissions in the presence but not in the absence of nitrite. A. eutrophus and P. stutzeri began to denitrify below 1% air saturation, with the former accumulating nitrite and N(inf2)O and the latter reducing nitrate almost completely to N(inf2). Transition of A. eutrophus and P. stutzeri from 80 to 0% air saturation resulted in transient maxima of denitrification intermediates. Such transient maxima were not observed after transition from 1 to 0%. Reduction of nitrate by A. eutrophus continued 48 h after the onset of the aeration, whereas N(inf2)O emission by P. stutzeri increased for only a short period. It was concluded that only in the presence of nitrite are nitrifiers able to dominate the NO and N(inf2)O emissions of soils shortly after a rainfall event.     

The Influence of Light and Temperature on Fruiting of Coprinus lagopus Fr. in Pure Culture

Some effects of light and temperature on fruiting of Coprinuslagopus in pure culture are described. Fruiting, which in darknessdid not commence until about the 15th day, was accelerated bycontinuous light or by brief exposures to light between the7th and 13th days of incubation. Very small exposures sufficed,provided they were of a wavelength no longer than that of greenlight, the response being restricted to the area of myceliumactually exposed. In both light and dark a temperature near25° C. was optimal for growth and fruiting.     

Baculovirus Per Os Infectivity Factors Form a Complex on the Surface of Occlusion-Derived Virus

Five highly conserved per os infectivity factors, PIF1, PIF2, PIF3, PIF4, and P74, have been reported to be essential for oral infectivity of baculovirus occlusion-derived virus (ODV) in insect larvae. Three of these proteins, P74, PIF1, and PIF2, were thought to function in virus binding to insect midgut cells. In this paper evidence is provided that PIF1, PIF2, and PIF3 form a stable complex on the surface of ODV particles of the baculovirus Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV). The complex could withstand 2% SDS-5% β-mercaptoethanol with heating at 50°C for 5 min. The complex was not formed when any of the genes for PIF1, PIF2, or PIF3 was deleted, while reinsertion of these genes into AcMNPV restored the complex. Coimmunoprecipitation analysis independently confirmed the interactions of the three PIF proteins and revealed in addition that P74 is also associated with this complex. However, deletion of the p74 gene did not affect formation of the PIF1-PIF2-PIF3 complex. Electron microscopy analysis showed that PIF1 and PIF2 are localized on the surface of the ODV with a scattered distribution. This distribution did not change for PIF1 or PIF2 when the gene for PIF2 or PIF1 protein was deleted. We propose that PIF1, PIF2, PIF3, and P74 form an evolutionarily conserved complex on the ODV surface, which has an essential function in the initial stages of baculovirus oral infection.The entry mechanism of enveloped viruses includes two major steps: virus binding to host receptors and subsequent fusion of the viral membrane with the cell membrane. For many viruses the processes of binding and fusion are mediated by a machinery composed of several membrane proteins working in concert with sequential events triggered by conformational changes upon interaction with host (co)receptors. Examples are herpes simplex virus (HSV) (4) and vaccinia virus (23), which have an entry machinery composed of four and eight proteins, respectively. The entry of the occlusion-derived virus (ODV) form of baculoviruses into insect midgut epithelial cells upon oral infection of insect larvae may involve a similar strategy, but little is known about the role of ODV membrane proteins.Baculovirus ODVs are orally infectious, enveloped virus particles embedded in a protein crystal called an occlusion body (OB) that infect midgut epithelial cells (24). After ingestion of OBs by the host, the proteinaceous OB crystal dissolves quickly due to the alkaline conditions (pH 10 to 11) in the midgut, and the ODV particles are released (reviewed in reference 24). After passage through the peritrophic membrane, ODVs bind and fuse with the microvilli of columnar epithelial cells, resulting in the release of nucleocapsids into the cytosol and subsequent initiation of infection (10, 12, 24). A second type of virus particle, the budded virus (BV), is produced in these cells and infects other cells and tissues in the insect, causing a systemic infection (reviewed in reference 22). While the entry mechanisms of BVs have been studied at least to a certain extent (16, 31, 32), the entry mechanism of ODVs is still rather enigmatic due to its complexity and the lack of proper cell lines supporting ODV entry.ODVs contain more than 10 different envelope proteins (3). Five of these, denoted PIF1, PIF2, PIF3, PIF4, and P74, have been identified to be essential for per os infection of insect larvae (6, 7, 14, 18, 20). These PIF proteins function in the early stage of virus infection, and deletion of any of these pif genes leads to a block in infection prior to viral gene expression in midgut epithelial cells (7, 10, 18). Until now, three of these proteins, PIF1, PIF2, and P74, have been reported to function in virus binding (10, 18). Deletion of any of these three proteins leads to a loss of oral infectivity, while only a 3-fold reduction in binding is measured, and no significant reduction in fusion efficiency is observed (10, 18). This suggests that the three PIF proteins, apart from binding to midgut epithelial cells, may have other unknown functions for which they may have to work together. The functions of PIF3 and PIF4 are rather enigmatic although there has been speculation that PIF3 functions in nucleocapsid translocation along the microvilli as it seemed to be dispensable for ODV binding and fusion (18, 24).All five proteins are highly conserved in Baculoviridae and are encoded by so-called core genes (3, 6, 11, 29). Recent work further revealed that these proteins have homologues in other large invertebrate DNA viruses which replicate in the nucleus, such as salivary gland hypertrophy viruses (SGHVs) (9), nudiviruses (30) and white spot syndrome virus (WSSV) (Nimaviridae) (J. A. Jehle, personal communication). pif genes are also found in polydnaviruses of braconid wasps (2). This high conservation of pif genes in a diverse range of large, circular, double-stranded DNA viruses suggests that the PIF proteins are associated with a conserved and evolutionarily ancient entry mechanism of viruses into invertebrate hosts.The aim of the present study is to follow the ODV entry process by investigating whether the PIF proteins form a complex on the ODV membrane. Based on immunogold labeling, cross-linking, differential temperature SDS-PAGE, and coimmunoprecipitation (CoIP) analysis with a panel of recombinant viruses, we provide strong evidence that PIF1, PIF2, PIF3, and P74 form a complex on the ODV surface. This complex is likely to play an essential role in virus entry into midgut epithelial cells of susceptible insect larvae.     

Light as an Energy Source in Continuous Cultures of Bacteriorhodopsin-Containing Halobacteria

The role of light as an energy source for slightly aereated cultures of halobacteria was studied, using continuous cultures with low nutrient concentrations and a low oxygen supply. A series of experiments were carried out with non-illuminated and differently illuminated cultures and with different oxygen transfer rates. Under low oxygen availability, light proved to be a decisively important energy source that allowed the populations to reach higher growth rates and much higher population densities. Oxygen influenced the growth over only a minimal level, below which neither the illuminated nor the dark cultures were affected by the oxygen transfer rate. From these results, it appears that the bacteriorhodopsin-mediated energy supply could have a very important role for the ecology of halobacteria in their microaerophilic habitats. In the illuminated cultures, cells that originated purple colonies on plates appeared. These cells, which could be bacteriorhodopsin-constitutive mutants, are now being studied.     

The Effect of Monensin on Pure and Mixed Cultures of Rumen Bacteria

The antibiotic monensin was added to pure cultures of Bacteroides ruminicola, Selenomonas ruminantium, Anaerovibrio lipolytica and Megasphaera elsdenii. These organisms, representing succinate- and propionate-producing rumen bacteria, were not affected by monensin up to 10 μg/ml. Methanobacterium ruminantium was slightly inhibited by monensin, Butyrivibrio fibrisolvens, Ruminococcus albus and Streptococcus bovis were inhibited to differing extents by monensin at concentrations between 0.1 and 10 μg/ml. Bacteroides succinogenes was inhibited at first by monensin at >0.5 μg/ml but after a prolonged lag phase adapted to grow in the presence of monensin at concentrations below 5 μg/ml.
Monensin (1 μg/ml) almost completely stopped the digestion of chopped straw and dewaxed cotton fibres by rumen contents incubated in vitro. The digestion of grass and powdered filter paper was not significantly reduced under these conditions, but when the concentration of monensin was increased to between 3 and 5 μg/ml, the digestion of these substrates was reduced.     

Feed Refusal Factors in Pure Cultures of Fusarium roseum ”graminearum”

Isolations from 1972 Wisconsin feed refusal corn yielded predominantly cultures of Fusarium roseum 'graminearum.' With one possible exception, none of the selected isolates of this fungus induced emesis in pigeons, whereas six of nine isolates produced feed refusal responses in all test animals. A single isolate of F. roseum 'equiseti' also induced a severe refusal response and possibly slight emesis. None of the other fungi isolated from this corn (F. moniliforme, Acremoniella atra) or controls caused either emesis or feed refusal. Zearalenone was detected in all isolates and was shown to be partially responsible for refusal activity. The remaining activity was ascribed to one or more nonvolatile, neutral, relatively polar molecules. T-2 toxin, although not detected in these isolates, was shown to have dramatic refusal activity in rats.     

The Aeration of Catharanthus roseus L. G. Don Suspension Cultures in Airlift Bioreactors: The Inhibitory Effect at High Aeration Rates on Culture Growth

An investigation was carried out to examine the effect of aerationon the growth of Catharanthus roseus suspension cultures inairlift bioreactors. A high aeration rate (0·86 v.v.m.)was found to inhibit the growth of cultures. Venting culturesat a high rate with low oxygen content gas mixtures was equallyinhibitory to culture growth, showing that high aeration wasnot inhibitory as a result of oxygen toxicity. The dissolvedcarbon dioxide tension was found to be lower in cultures operatedat high aeration than those operated at low aeration. Supplyingexogenous CO₂ to cultures at high aeration restored the CO₂tension to values normally encountered at a low aeration rate,and was found to alleviate the inhibitory effects at high aeration.However, further increasing the CO₂ supply to cultures was foundto be severely inhibitory to growth. Therefore, the growth ofC. roseus cultures is very sensitive to dissolved CO₂ concentration,growth being inhibited at values either higher or lower thanan optimum. Key words: Aeration, carbon dioxide, Catharanthus roseus suspension culture     

Plants Actively Avoid State Transitions upon Changes in Light Intensity: Role of Light-Harvesting Complex II Protein Dephosphorylation in High Light

Photosystem II (PSII) core and light-harvesting complex II (LHCII) proteins in plant chloroplasts undergo reversible phosphorylation upon changes in light intensity (being under control of redox-regulated STN7 and STN8 kinases and TAP38/PPH1 and PSII core phosphatases). Shift of plants from growth light to high light results in an increase of PSII core phosphorylation, whereas LHCII phosphorylation concomitantly decreases. Exactly the opposite takes place when plants are shifted to lower light intensity. Despite distinct changes occurring in thylakoid protein phosphorylation upon light intensity changes, the excitation balance between PSII and photosystem I remains unchanged. This differs drastically from the canonical-state transition model induced by artificial states 1 and 2 lights that concomitantly either dephosphorylate or phosphorylate, respectively, both the PSII core and LHCII phosphoproteins. Analysis of the kinase and phosphatase mutants revealed that TAP38/PPH1 phosphatase is crucial in preventing state transition upon increase in light intensity. Indeed, tap38/pph1 mutant revealed strong concomitant phosphorylation of both the PSII core and LHCII proteins upon transfer to high light, thus resembling the wild type under state 2 light. Coordinated function of thylakoid protein kinases and phosphatases is shown to secure balanced excitation energy for both photosystems by preventing state transitions upon changes in light intensity. Moreover, PROTON GRADIENT REGULATION5 (PGR5) is required for proper regulation of thylakoid protein kinases and phosphatases, and the pgr5 mutant mimics phenotypes of tap38/pph1. This shows that there is a close cooperation between the redox- and proton gradient-dependent regulatory mechanisms for proper function of the photosynthetic machinery.Photosynthetic light reactions take place in the chloroplast thylakoid membrane. Primary energy conversion reactions are performed by synchronized function of the two light energy-driven enzymes PSII and PSI. PSII uses excitation energy to split water into electrons and protons. PSII feeds electrons to the intersystem electron transfer chain (ETC) consisting of plastoquinone, cytochrome b₆f, and plastocyanin. PSI oxidizes the ETC in a light-driven reduction of NADP to NADPH. Light energy is collected by the light-harvesting antenna systems in the thylakoid membrane composed of specific pigment-protein complexes (light-harvesting complex I [LHCI] and LHCII). The majority of the light-absorbing pigments are bound to LHCII trimers that can serve the light harvesting of both photosystems (Galka et al., 2012; Kouřil et al., 2013; Wientjes et al., 2013b). Energy distribution from LHCII is regulated by protein phosphorylation (Bennett, 1979; Bennett et al., 1980; Allen et al., 1981) under control of the STN7 and STN8 kinases (Depège et al., 2003; Bellafiore et al., 2005; Bonardi et al., 2005; Vainonen et al., 2005) and the TAP38/PPH1 and Photosystem II Core Phosphatase (PBCP) phosphatases (Pribil et al., 2010; Shapiguzov et al., 2010; Samol et al., 2012). LHCII trimers are composed of LHCB1, LHCB2, and LHCB3 proteins, and in addition to reversible phosphorylation of LHCB1 and LHCB2, the protein composition of the LHCII trimers also affects the energy distribution from the light-harvesting system to photosystems (Damkjaer et al., 2009; Pietrzykowska et al., 2014). Most of the LHCII trimers are located in the PSII-rich grana membranes and PSII- and PSI-rich grana margins of the thylakoid membrane, and only a minor fraction resides in PSI- and ATP synthase-rich stroma lamellae (Tikkanen et al., 2008b; Suorsa et al., 2014). Both photosystems bind a small amount of LHCII trimers in biochemically isolatable PSII-LHCII and PSI-LHCII complexes (Pesaresi et al., 2009; Järvi et al., 2011; Caffarri et al., 2014). The large portion of the LHCII, however, does not form isolatable complexes with PSII or PSI, and therefore, it separates as free LHCII trimers upon biochemical fractionation of the thylakoid membrane by Suc gradient centrifugation or in native gel analyses (Caffarri et al., 2009; Järvi et al., 2011), the amount being dependent on the thylakoid isolation method. Nonetheless, in vivo, this major LHCII antenna fraction serves the light-harvesting function. This is based on the fact that fluorescence from free LHCII, peaking at 680 nm in 77-K fluorescence emission spectra, can only be detected when the energy transfer properties of the thylakoid membrane are disturbed by detergents (Grieco et al., 2015).Regulation of excitation energy distribution from LHCII to PSII and PSI has, for decades, been linked to LHCII phosphorylation and state transitions (Bennett, 1979; Bennett et al., 1980; Allen et al., 1981). It has been explained that a fraction of LHCII gets phosphorylated and migrates from PSII to PSI, which can be evidenced as increase in PSI cross section and was assigned as transition to state 2 (for review, see Allen, 2003; Rochaix et al., 2012). The LHCII proteins are, however, phosphorylated all over the thylakoid membrane (i.e. in the PSII- and LHCII-rich grana core) in grana margins containing PSII, LHCII, and PSI as well as in PSI-rich stroma lamellae also harboring PSII-LHCII, LHCII, and PSI-LHCII complexes in minor amounts (Tikkanen et al., 2008b; Grieco et al., 2012; Leoni et al., 2013; Wientjes et al., 2013a)—making the canonical-state transition theory inadequate to explain the physiological role of reversible LHCII phosphorylation (Tikkanen and Aro, 2014). Moreover, the traditional-state transition model is based on lateral segregation of PSII-LHCII and PSI-LHCI to different thylakoid domains. It, however, seems likely that PSII and PSI are energetically connected through a shared light-harvesting system composed of LHCII trimers (Grieco et al., 2015), and there is efficient excitation energy transfer between the two photosystems (Yokono et al., 2015). Nevertheless, it is clear that LHCII phosphorylation is a prerequisite to form an isolatable PSI-LHCII complex called the state transition complex (Pesaresi et al., 2009; Järvi et al., 2011). Existence of a minor state transition complex, however, does not explain why LHCII is phosphorylated all over the thylakoid membrane and how the energy transfer is regulated from the majority of LHCII antenna that is shared between PSII and PSI but does not form isolatable complexes with them (Grieco et al., 2015).Plants grown under any steady-state white light condition show the following characteristics of the thylakoid membrane: PSII core and LHCII phosphoproteins are moderately phosphorylated, phosphorylation takes place all over the thylakoid membrane, and the PSI-LHCII state transition complex is present (Järvi et al., 2011; Grieco et al., 2012; Wientjes et al., 2013b). Upon changes in the light intensity, the relative phosphorylation level between PSII core and LHCII phosphoproteins drastically changes (Rintamäki et al., 1997, 2000) in the timescale of 5 to 30 min. When light intensity increases, the PSII core protein phosphorylation increases, whereas the level of LHCII phosphorylation decreases. On the contrary, a decrease in light intensity decreases the phosphorylation level of PSII core proteins but strongly increases the phosphorylation of the LHCII proteins (Rintamäki et al., 1997, 2000). The presence and absence of the PSI-LHCII state transition complex correlate with LHCII phosphorylation (similar to the state transitions; Pesaresi et al., 2009; Wientjes et al., 2013b). Despite all of these changes in thylakoid protein phosphorylation, the relative excitation of PSII and PSI (i.e. the absorption cross section of PSII and PSI measured by 77-K fluorescence) remains nearly unchanged upon changes in white-light intensity (i.e. no state transitions can be observed despite massive differences in LHCII protein phosphorylation; Tikkanen et al., 2010).The existence of the opposing behaviors of PSII core and LHCII protein phosphorylation, as described above, has been known for more than 15 years (Rintamäki et al., 1997, 2000), but the physiological significance of this phenomenon has remained elusive. It is known that PSII core protein phosphorylation in high light (HL) facilitates the unpacking of PSII-LHCII complexes required for proper processing of the damaged PSII centers and thus, prevents oxidative damage of the photosynthetic machinery (Tikkanen et al., 2008a; Fristedt et al., 2009; Goral et al., 2010; Kirchhoff et al., 2011). It is also known that the damaged PSII core protein D1 needs to be dephosphorylated before its proteolytic degradation upon PSII turnover (Koivuniemi et al., 1995). There is, however, no coherent understanding available to explain why LHCII proteins are dephosphorylated upon exposure of plants to HL and PSII core proteins are dephosphorylated upon exposure to low light (LL).The above-described light quantity-dependent control of thylakoid protein phosphorylation drastically differs from the light quality-dependent protein phosphorylation (Tikkanen et al., 2010). State transitions are generally investigated by using different light qualities, preferentially exciting either PSI or PSII. State 1 light favors PSI excitation, leading to oxidation of the ETC and dephosphorylation of both the PSII core and LHCII proteins. State 2 light, in turn, preferentially excites PSII, leading to reduction of ETC and strong concomitant phosphorylation of both the PSII core and LHCII proteins (Haldrup et al., 2001). Shifts between states 1 and 2 lights induce state transitions, mechanisms that change the excitation between PSII and PSI (Murata and Sugahara, 1969; Murata, 2009). Similar to shifts between state lights, the shifts between LL and HL intensity also change the phosphorylation of the PSII core and LHCII proteins (Rintamäki et al., 1997, 2000). Importantly, the white-light intensity-induced changes in thylakoid protein phosphorylation do not change the excitation energy distribution between the two photosystems (Tikkanen et al., 2010). Despite this fundamental difference between the light quantity- and light quality-induced thylakoid protein phosphorylations, a common feature for both mechanisms is a strict requirement of LHCII phosphorylation for formation of the PSI-LHCII complex. However, it is worth noting that LHCII phosphorylation under state 2 light is not enough to induce the state 2 transition but that the P-LHCII docking proteins in the PSI complex are required (Lunde et al., 2000; Jensen et al., 2004; Zhang and Scheller, 2004; Leoni et al., 2013).Thylakoid protein phosphorylation is a dynamic redox-regulated process dependent on the interplay between two kinases (STN7 and STN8; Depège et al., 2003; Bellafiore et al., 2005; Bonardi et al., 2005; Vainonen et al., 2005) and two phosphatases (TAP38/PPH1 and PBCP; Pribil et al., 2010; Shapiguzov et al., 2010; Samol et al., 2012). Concerning the redox regulation mechanisms in vivo, only the LHCII kinase (STN7) has so far been thoroughly studied (Vener et al., 1997; Rintamäki et al., 2000; Lemeille et al., 2009). The STN7 kinase is considered as the LHCII kinase, and indeed, it phosphorylates the LHCB1 and LHCB2 proteins (Bellafiore et al., 2005; Bonardi et al., 2005; Tikkanen et al., 2006). In addition to this, STN7 takes part in the phosphorylation of PSII core proteins (Vainonen et al., 2005), especially in LL (Tikkanen et al., 2008b, 2010). The STN8 kinase is required for phosphorylation of PSII core proteins in HL but does not significantly participate in phosphorylation of LHCII (Bellafiore et al., 2005; Bonardi et al., 2005; Vainonen et al., 2005; Tikkanen et al., 2010). It has been shown that, in traditional state 1 condition, which oxidizes the ETC, the dephosphorylation of LHCII is dependent on TAP38/PPH1 phosphatase (Pribil et al., 2010; Shapiguzov et al., 2010), whereas the PSII core protein dephosphorylation is dependent on the PBCP phosphatase (Samol et al., 2012). However, it remains unresolved whether and how the TAP38/PPH1 and PBCP phosphatases are involved in the light intensity-dependent regulation of thylakoid protein phosphorylation typical for natural environments.Here, we have used the two kinase (stn7 and stn8) and the two phosphatase (tap38/pph1and pbcp) mutants of Arabidopsis (Arabidopsis thaliana) to elucidate the individual roles of these enzymes in reversible thylakoid protein phosphorylation and distribution of excitation energy between PSII and PSI upon changes in light intensity. It is shown that the TAP38/PPH1-dependent, redox-regulated LHCII dephosphorylation is the key component to maintain excitation balance between PSII and PSI upon increase in light intensity, which at the same time, induces strong phosphorylation of the PSII core proteins. Collectively, reversible but opposite phosphorylation and dephosphorylation of the PSII core and LHCII proteins upon increase or decrease in light intensity are shown to be crucial for maintenance of even distribution of excitation energy to both photosystems, thus preventing state transitions. Moreover, evidence is provided indicating that the pH gradient across the thylakoid membrane is yet another important component in regulation of the distribution of excitation energy to PSII and PSI, possibly by affecting the regulation of thylakoid kinases and phosphatases.     

The Effect of Light on the Synthesis of Mitochondrial Enzymes in Division-synchronized Euglena Cultures

The development of the mitochondrial enzymes fumarase and succinate dehydrogenase has been followed in Euglena cultures division-synchronized by 14-hour light periods alternating with 12-hour dark periods. The activity of both enzymes was unaltered over the light phase, doubled in early dark phase, and thereafter remained constant over the rest of the cycle. The increase in enzyme activity in early dark phase probably represented de novo enzyme synthesis because it was prevented by the addition of cycloheximide at a concentration known to inhibit protein synthesis on Euglena cytoplasmic ribosomes.     

Effects of Temperature on Methane Consumption in a Forest Soil and in Pure Cultures of the Methanotroph Methylomonas rubra

Methane oxidation in soil cores from a mixed hardwood-coniferous forest varied relatively little as a function of incubation temperatures from −1 to 30°C. The increase in oxidation rate was proportional to T^2.4 (in kelvins). This relationship was consistent with limitation of methane transport through a soil gas phase to a subsurface zone of consumption by diffusion. The Q₁₀ for CO₂ production, 3.4, was substantially higher than that for methane oxidation, 1.1, and indicated that the response of soil respiration to temperature was limited by enzymatic processes and not diffusion of either organic substrates or molecular oxygen. When grown under conditions of phase-transfer limitation, cultures of Methylomonas rubra showed a minimal response to temperature changes between 19 and 38°C, as indicated by methane oxidation rates; in the absence of phase-transfer limitations, M. rubra oxidized methane at rates strongly dependent on temperature.