Utilization of gaseous emissions from a methanol plant for cultivation of <Emphasis Type="Italic">Acutodesmus obliquus</Emphasis>

This study aimed to culture the green alga Acutodesmus obliquus utilizing the gaseous emissions containing a high concentration of CO₂ (99.13 %) from a methanol plant and study the tolerance of microalgae. The effect of CO₂ concentration, aeration rate, inoculum concentration, intermittent sparging, and nitrogen sources on the growth of A. obliquus was examined. Acutodesmus obliquus also was cultivated in a 500-L pilot outdoor tubular photobioreactor (OTP) to advance the laboratory scale system to outdoor scale-up applications. The results showed that A. obliquus could tolerate high CO₂ concentrations of 50 %, and a maximum biomass of 0.935 g L^?1 (dry weight) was achieved at 20 % CO₂. An aeration rate of 500 mL min^?1, inoculum concentration (optical density at 680 nm [OD₆₈₀]?=?0.3), and intermittent sparging of 10 min per 2 h enhanced growth to the optimum and influenced culture pH and photosynthesis. Urea as a nitrogen source was shown to be more beneficial to cell growth. A urea concentration of 0.3 g L^?1 and an N/P ratio of 15 led to maximum biomass accumulation thus enhancing the gaseous emission utilization efficiency. In conclusion, this work demonstrated that gaseous emissions containing high concentration of CO₂ from a methanol plant could be directly introduced into A. obliquus cultures and that A. obliquus was suitable well for large-scale outdoor cultivation in a tubular photobiorecator.     

Carbonic Anhydrase and the Regulation of Photosynthesis

THE role of CO₂ in the regulation of photosynthetic and respiratory metabolism in plants is little understood in the unicellular alga Chlorella pyrenoidosa; for example, after autotrophic growth in high CO₂ (5·5% by volume), transfer to a CO₂ concentration about ten times less than the concentration in air results initially in low rates of photosynthesis characterized by the virtual absence of the Calvin cycle¹ of CO₂ fixation². An induction period of about 2 h is necessary before normal photosynthetic rates are established. Cells grown in air (0.03% CO₂) do not show this effect and photosynthesize at comparatively high rates even in very low concentrations of CO₂.     

Impact of elevated CO<Subscript>2</Subscript> in <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> rooted stem cuttings inoculated with <Emphasis Type="Italic">Frankia</Emphasis>

Impact of different levels of elevated CO ₂ on the activity of Frankia (Nitrogen-fixing actinomycete) in Casuarina equisetifolia rooted stem cuttings has been studied to understand the relationship between C. equisetifolia, Frankia and CO₂. The stem cuttings of C. equietifolia were collected and treated with 2000 ppm of Indole Butyric Acid (IBA) for rooting. Thus vegetative propagated rooted stem cuttings of C. equisetifolia were inoculated with Frankia and placed in the Open top chambers (OTC) with elevated CO₂ facilities. These planting stocks were maintained in the OTC for 12 months under different levels of elevated CO₂ (ambient control, 600 ppm, 900 ppm). After 12 months, the nodule numbers, bio mass, growth, and photosynthesis of C. equisetifolia rooted stem cuttings inoculated with Frankia were improved under 600 ppm of CO₂. The rooted stem cuttings of C. equisetifolia inoculated with Frankia showed a higher number of nodules under 900 ppm of CO₂ and cuttings without Frankia inoculation exhibited poor growth. Tissue Nitrogen (N) content was also higher under 900 ppm of CO₂ than ambient control and 600 ppm levels. The photosynthetic rate was higher (17.8 μ mol CO₂ m^?2 s^?1) in 900 ppm of CO₂ than in 600 ppm (13.2 μ mol CO₂ m^?2 s^?1) and ambient control (8.3 μ mol CO₂ m^?2 s^?1). This study showed that Frankia can improve growth, N fixation and photosynthesis of C. equietifolia rooted stem cuttings under extreme elevated CO₂ level conditions (900 ppm).     

Physiological and proteomic analysis of salinity tolerance of the halotolerant cyanobacterium <Emphasis Type="Italic">Anabaena</Emphasis> sp

The halotolerant cyanobacterium Anabaena sp was grown under NaCl concentration of 0, 170 and 515 mM and physiological and proteomic analysis was performed. At 515 mM NaCl the cyanobacterium showed reduced photosynthetic activities and significant increase in soluble sugar content, proline and SOD activity. On the other hand Anabaena sp grown at 170 mM NaCl showed optimal growth, photosynthetic activities and comparatively low soluble sugar content, proline accumulation and SOD activity. The intracellular Na⁺ content of the cells increased both at 170 and 515 mM NaCl. In contrast, the K⁺ content of the cyanobacterium Anabaena sp remained stable in response to growth at identical concentration of NaCl. While cells grown at 170 mM NaCl showed highest intracellular K⁺/Na⁺ ratio, salinity level of 515 mM NaCl resulted in reduced ratio of K⁺/Na⁺. Proteomic analysis revealed 50 salt-responsive proteins in the cyanobacterium Anabaena sp under salt treatment compared with control. Ten protein spots were subjected to MALDI-TOF–MS/MS analysis and the identified proteins are involved in photosynthesis, protein folding, cell organization and energy metabolism. Differential expression of proteins related to photosynthesis, energy metabolism was observed in Anabaena sp grown at 170 mM NaCl. At 170 mM NaCl increased expression of photosynthesis related proteins and effective osmotic adjustment through increased antioxidant enzymes and modulation of intracellular ions contributed to better salinity tolerance and optimal growth. On the contrary, increased intracellular Na⁺ content coupled with down regulation of photosynthetic and energy related proteins resulted in reduced growth at 515 mM NaCl. Therefore reduced growth at 515 mM NaCl could be due to accumulation of Na⁺ ions and requirement to maintain higher organic osmolytes and antioxidants which is energy intensive. The results thus show that the basis of salt tolerance is different when the halotolerant cyanobacterium Anabaena sp is grown under low and high salinity levels.     

General medium for the autotrophic cultivation of acetogens

Syngas fermentation, a microbial process in which synthesis gas serves as a substrate for acetogens, has attracted increasing interest in the last few years. For the purposeful selection of acetogens for various applications, it would be useful to characterize and compare the process performances of as many autotrophic strains as possible under identical process conditions. Unfortunately, all the media compositions so far recommended for syngas fermentation differ considerably with respect to each individual strain. Therefore, a general medium for syngas fermentation was designed. The suitability of this new general-acetogen medium (GA-medium) was proven based on the autotrophic batch cultivation of Acetobacterium fimetarium, Acetobacterium wieringae, Blautia hydrogenotrophica, Clostridium magnum, Eubacterium aggregans, Sporomusa acidovorans, Sporomusa ovata and Terrisporobacter mayombei in anaerobic flasks with an initial gas phase of H₂:CO₂ (66:34) (P = 200 kPa). A comparison of the autotrophic batch processes with this medium revealed T. mayombei as the bacterium with the highest maximum growth rate of 5.77 day^?1 which was more than 10 times higher than the lowest identified maximum growth rate of A. fimetarium. The maximum growth rates of A. wieringae, C. magnum and S. acidovorans were all in the same order of magnitude around 1.7 day^?1. The newly designed GA-medium offers the possibility to compare autotrophic process performances of different acetogens under similar conditions absent the effects of various media compositions.     

Molecular characterization and expression analysis of the Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> exchanger gene family in <Emphasis Type="Italic">Medicago truncatula</Emphasis>

One important mechanism plants use to cope with salinity is keeping the cytosolic Na⁺ concentration low by sequestering Na⁺ in vacuoles, a process facilitated by Na⁺/H⁺ exchangers (NHX). There are eight NHX genes (NHX1 through NHX8) identified and characterized in Arabidopsis thaliana. Bioinformatics analyses of the known Arabidopsis genes enabled us to identify six Medicago truncatula NHX genes (MtNHX1, MtNHX2, MtNHX3, MtNHX4, MtNHX6, and MtNHX7). Twelve transmembrane domains and an amiloride binding site were conserved in five out of six MtNHX proteins. Phylogenetic analysis involving A. thaliana, Glycine max, Phaseolus vulgaris, and M. truncatula revealed that each individual MtNHX class (class I: MtNHX1 through 4; class II: MtNHX6; class III: MtNHX7) falls under a separate clade. In a salinity-stress experiment, M. truncatula exhibited ~?20% reduction in biomass. In the salinity treatment, sodium contents increased by 178 and 75% in leaves and roots, respectively, and Cl^? contents increased by 152 and 162%, respectively. Na⁺ exclusion may be responsible for the relatively smaller increase in Na⁺ concentration in roots under salt stress as compared to Cl^?. Decline in tissue K⁺ concentration under salinity was not surprising as some antiporters play an important role in transporting both Na⁺ and K ⁺ . MtNHX1, MtNHX6, and MtNHX7 display high expression in roots and leaves. MtNHX3, MtNHX6, and MtNHX7 were induced in roots under salinity stress. Expression analysis results indicate that sequestering Na⁺ into vacuoles may not be the principal component trait of the salt tolerance mechanism in M. truncatula and other component traits may be pivotal.     

Two-tier vessel for photoautotrophic high-density cultures

Two-tier vessels, developed for culturing of microalgae and cyanobacteria at high cell density on a shaken platform, were assembled from a flat lower chamber to be filled with a CO₂ buffer and an upper flat sterile chamber for the culture that was separated from the lower chamber by a porous polypropylene membrane. Diffusive gas exchange with the atmosphere was controlled by the O₂ outlet channel. Referred to surface area, rates of CO₂ transfer to a shaken weakly alkaline buffer solution across the membrane were higher than those reached on the conventional pathway through the free upper liquid surface. Membrane-mediated CO₂ supply enabled rapid growth of Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 up to ultrahigh cell density. The biomass (dry weight) concentration of Synechococcus cultures reached more than 30 g L^?1 on a buffered medium with adequate concentrations of mineral nutrients. An increase of 15 to 20 g L^?1 was observed during repeated two-day cycles. Separate pathways for CO₂ supply and oxygen outlet prevented significant loss of CO₂. Convective gas flow through the oxygen outlet channel enabled the estimation of the O₂ generation rate. The permeability of the channel for diffusive O₂/N₂ exchange limited the O₂ concentration to a moderate value. It is concluded that shaken flat cultures using CO₂ supply through a porous hydrophobic membrane and diffusive release of O₂ through a separate pathway are promising for research on microalgae and cyanobacteria.     

Na<Superscript>+</Superscript>-translocating rhodopsin from <Emphasis Type="Italic">Dokdonia</Emphasis> sp. PRO95 does not contain carotenoid antenna

Carotenoid-binding properties of Na⁺-translocating rhodopsin (NaR) from Dokdonia sp. PRO95 were studied. Carotenoids were extracted from Dokdonia sp. PRO95 cells. It was found that zeaxanthin is the predominant carotenoid of this bacterium. Incubation of recombinant NaR purified from Escherichia coli cells with carotenoids from Dokdonia sp. PRO95 did not result in any changes in optical absorption or circular dichroism spectra, indicating the absence of binding of the carotenoids by NaR. The same results were obtained using salinixanthin as the carotenoid. These data along with genome analysis of Dokdonia sp. PRO95 and other flavobacteria indicate that NaR from Dokdonia sp. PRO95 and possibly the other flavobacterial Na⁺-translocating rhodopsins do not contain a carotenoid antenna.     

Lima bean nodulates efficiently with <Emphasis Type="Italic">Bradyrhizobium</Emphasis> strains isolated from diverse legume species

Lima bean (Phaseolus lunatus L.) is an important legume species that establishes symbiosis with rhizobia, mainly of the Bradyrhizobium genus. The aim of this study was to evaluate the efficiency of rhizobia of the genus Bradyrhizobium in symbiosis with lima bean, in both Leonard jars and in pots with a Latossolo Amarelo distrófico (Oxisol). In the experiment in Leonard jars, 17 strains isolated from nodules of the three legume subfamilies, Papilionoideae (Vigna unguiculata, Pterocarpus sp., Macroptilium atropurpureum, Swartzia sp., and Glycine max), Mimosoideae (Inga sp.), and Caesalpinioideae (Campsiandra surinamensis) and two uninoculated controls, one with a low concentration (5.25 mg L^?1) and another with a high concentration (52.5 mg L^?1) of mineral nitrogen (N) were evaluated. The six strains that exhibited the highest efficiency in Leonard jars, isolated from nodules of Vigna unguiculata (UFLA 03–144, UFLA 03–84, and UFLA 03–150), Campsiandra surinamensis (INPA 104A), Inga sp. (INPA 54B), and Swartzia sp. (INPA 86A), were compared to two uninoculated controls, one without and another with 300 mg N dm^?3 (NH₄NO₃) applied to pots with samples of an Oxisol in the presence and absence of liming. In this experiment, liming did not affect nodulation and plant growth; the INPA 54B and INPA 86A strains stood out in terms of shoot dry matter production and provided increases of approximately 48% in shoot N accumulation compared to the native rhizobia populations. Our study is the first to indicate Bradyrhizobium strains isolated from the three legume subfamilies are able to promote lima bean growth via biological nitrogen fixation in soil conditions.     

Effect of red and blue light on acclimation of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> to CO<Subscript>2</Subscript>-limiting conditions

Effects of red (RL) and blue (BL) light on acclimation of the unicellular green alga Chlamydomonas reinhardtii to the low level of ambient CO₂ were studied. C. reinhardtii cells grown at 5% CO₂ and under white light (170 μmol/(m²s)) had a relatively low activity of extracellular carbonic anhydrase (CA), a low affinity for dissolved inorganic carbon, and a low rate of photosynthesis under CO₂-limiting conditions. These cells readily started acclimation to the low CO₂ concentration when they were exposed to atmospheric air (～ 0.03% CO₂) under RL or BL (150 μmol/(m² s) each). The acclimation was manifested in a significant increase in the CO₂-limited rate of photosynthesis, the affinity for dissolved inorganic carbon, and the extracellular CA activity with no difference between RL-and BL-cells. Independently of light quality, the acclimation was completed for 5–7 h after cell exposure to air. As is evident from RL-and BL-dependent changes in the sum of chlorophylls and chlorophyll a/b ratio, transfer of C. reinhardtii cells to air and RL or BL triggered also the process of algal photosynthetic adaptation to light quality. However, this process did not interfere with acclimation to low CO₂ because started 4 h later. On the basis of similarity in the low CO₂-induced changes under RL and BL, it is concluded that acclimation of C. reinhardtii to CO₂-limiting conditions does not depend on light quality.     

Effect of cement industry flue gas simulation on the physiology and photosynthetic performance of <Emphasis Type="Italic">Chlorella sorokiniana</Emphasis>

Cement plants account for significant emissions of CO₂ and other pollutants into the atmosphere. As a means for its mitigation, we tested the effect of a cement industry-based flue gas simulation (FGS — 18% CO₂, 9% O₂, 300 ppm NO₂, 140 ppm SO₂) on the green alga, Chlorella sorokiniana. Culture pH, cell density, cell viability and productivity, specific growth rates, photosynthetic performance, and biochemical composition were monitored. The treatments consisted of different FGS volumes (0.1, 0.3, 0.8, 1.5, 6, and 48 L day^?1) that were applied in a series of laboratory-scale semi-continuous batch cultures under controlled conditions. Controls were exposed to 18% CO₂ enriched air. Cell density showed that C. sorokiniana was able to grow in all treatments, but compared to the controls, low pH (~ 5.0) caused by 48 L FGS day^?1 led to 27% decrease in specific growth rate. Increasing FGS exposure decreased maximum and operational quantum yields obtained by pulse amplitude modulated fluorometry, while photochemical quenching remained constant (~ 0.93). The α and rETR _max parameters calculated from rapid light curves decreased with increasing FGS exposure. Total proteins and carbohydrates (per cell basis) increased after 6 and 48 L FGS day^?1, which can be advantageous for biotechnological applications, but cell productivity (cells L^?1 day^?1) decreased. Despite the effects in physiology, C. sorokiniana could withstand a pH range of 6.0–5.0 imposed by 48 L FGS day^?1. Overall, C. sorokiniana can be considered a robust species in flue gas bioremediation.     

Effect of high CO<Subscript>2</Subscript> concentrations on the growth and macromolecular composition of a heat- and high-light-tolerant microalga

A green microalga, Acutodesmus sp., a close relative of Acutodesmus deserticola, was isolated from the wastewater discharges of an oil refinery in India. This study examined the effects of light intensity, temperature, pH, and high-CO₂ treatments (up to 20 %) on the growth of the alga and investigated the effects of different CO₂ treatments on its macromolecular composition (protein, carbohydrate, and lipids). Under controlled laboratory conditions, the alga showed high growth rates over a wide range of light (up to 700 μmol photons m^?2 s^?1), temperature (up to 40 °C), and pH (5–10) conditions. In the stationary phase, the highest protein and carbohydrate content was found to be 71.52 and 40.72 % of dry weight at 5 and 15 % CO₂, respectively. After 5 days of cultivation, the maximum dry weight biomass attained in these cultures was 1.149, 1.99, 1.75, and 1.65 g L^?1 at 5, 10, 15, and 20 % CO₂, respectively, indicating that this strain has significant tolerance to CO₂. These results indicate that this strain is a promising candidate for use in biofixation of CO₂ from the flue gases emitted by industries, and it also has a strong potential as a feedstock for value-added substances.     

Effects of macrophyte leachate on <Emphasis Type="Italic">Anabaena</Emphasis> sp. and <Emphasis Type="Italic">Chlamydomonas moewusii</Emphasis> growth in freshwater tropical ecosystems

This study reports on the effects of dissolved organic matter (DOM) derived from the aquatic macrophyte Pistia stratiotes (collected from a tropical reservoir) on the mixotrophic growth of two phytoplankton species (Chlamydomonas moewusii and Anabaena sp.). The DOM from P. stratiotes had a mainly aliphatic structure, low molecular weight, low cellulose and lignin content and high carbon content. The addition of DOM (5% v/v) significantly decreased the growth rate of Anabaena sp. but increased the chlorophyll a concentration of C. moewusii. Higher light intensity (100 versus 30 µmol m^?2 s^?1) was important for Anabaena sp., increasing its growth rate and chlorophyll content. The use of DOM from P. stratiotes to mitigate cyanobacterial blooms should be further explored in future studies.     

Elucidating the role of nutrients in C-phycocyanin production by the halophilic cyanobacterium <Emphasis Type="Italic">Euhalothece</Emphasis> sp.

In this study, a novel halophilic cyanobacterium was isolated and identified as Euhalothece sp. KZN. This fast-growing strain had the ability to synthesise high yields (12 mg g^?1) of C-phycocyanin (C-PC), a highly fluorescent blue light-harvesting pigment with numerous potential uses in the biotechnology and commercial sectors. This study elucidated the individual and interactive role of different nutrients in BG11 growth medium for enhancing C-PC production in Euhalothece sp. KZN. Nine components of BG11 medium were screened for their effects via fractional factorial design (FFD). The results revealed a significant influence of nutrients, viz. MgSO₄, NaNO₃ and minor nutrients (citric acid, EDTA-iron citrate, CaCl₂ and Na₂CO₃) on C-PC yield. These three components were further explored for their optimum concentration for enhancing C-PC production using a central composite design. The optimum values for these essential nutrients were found to be as follows: 0.10 g L^?1 of MgSO₄, 1.67 g L^?1 of NaNO₃ and 10 mL L^?1 of minor nutrients which resulted in a 280% increase in C-PC yield with predicted and actual values of 43.97 and 45 mg g^?1, respectively. Euhalothece sp. KZN is a strong potential candidate for C-PC production and can be further exploited to produce this industrially valuable compound.     

Paul Henry Latimer (1925–2011): discoverer of selective scattering in photosynthetic systems

The response of marine phytoplankton to the ongoing increase in atmospheric pCO₂ reflects the consequences of both increased CO₂ concentration and decreased pH in surface seawater. In the model diatom Thalassiosira weissflogii, we explored the effects of varying pCO₂ and pH, independently and in concert, on photosynthesis and respiration by incubating samples in water enriched in H₂ ¹⁸O. In long-term experiments (~6-h) at saturating light intensity, we observed no effects of pH or pCO₂ on growth rate, photosynthesis or respiration. This absence of a measurable response reflects the very small change in energy used by the carbon concentrating mechanism (CCM) compared to the energy used in carbon fixation. In short-term experiments (~3 min), we also observed no effects of pCO₂ or pH, even under limiting light intensity. We surmise that in T. weissflogii, it is the photosynthetic production of NADPH and ATP, rather than the CO₂-saturation of Rubisco that controls the rate of photosynthesis at low irradiance. In short-term experiments, we observed a slightly higher respiration rate at low pH at the onset of the dark period, possibly reflecting the energy used for exporting H⁺ and maintaining pH homeostasis. Based on what is known of the biochemistry of marine phytoplankton, our results are likely generalizable to other diatoms and a number of other eukaryotic species. The direct effects of ocean acidification on growth, photosynthesis and respiration in these organisms should be small over the range of atmospheric pCO₂ predicted for the twenty-first century.     

<Emphasis Type="Italic">Artemisia frigida</Emphasis> and <Emphasis Type="Italic">Stipa krylovii</Emphasis>, two dominant species in Inner Mongolia steppe,differed in their responses to elevated atmospheric CO<Subscript>2</Subscript> concentration

Aims

Despite extensive studies on effects of elevated CO₂ concentration ([CO₂]_e) on plant growth, few studies have investigated the responses of native grassland plant species to [CO₂]_e in terms of nutrient acquisition.

Methods

The effects of [CO₂]_e (769 ± 23 ppm) on Artemisia frigida and Stipa krylovii, two dominant species in Inner Mongolia steppe were investigated by growing them for 7 weeks in Open-Top Chambers (OTC).

Results

Exposure to [CO₂]_e enhanced shoot and root growth of A. frigida and S. krylovii. Elevated [CO₂] increased photosynthetic rates (Pn) by 34 % in A. frigida but decreased Pn by 52 % in S. krylovii. Moreover, root-secreted acid phosphatase activity in A. frigida was stimulated by [CO₂]_e, while exudation of malate from roots of S. krylovii was suppressed by [CO₂]_e. Exposure to [CO₂]_e led to a decrease in P concentration in shoots and roots of A. frigida and S. krylovii, but total amount of P accumulated in shoots and roots of both species was increased by [CO₂]_e.

Conclusions

The two dominant species in temperate steppes differed in their responses to [CO₂]_e, such that A. frigida was more adapted to [CO₂]_e than S. krylovii under low availability of soil P.

     

<Emphasis Type="Italic">Tetraselmis suecica</Emphasis> culture for CO<Subscript>2</Subscript> bioremediation of untreated flue gas from a coal-fired power station

The accumulation of atmospheric CO₂, primarily due to combustion of fossil fuels, has been implicated in potential global climate change. The high rate of CO₂ bioremediation by microalgae has emerged as a favourable method for reducing coal-fired power plant emissions. However, coal-fired power station flue gas contains other chemicals such as SO_x which can inhibit microalgal growth. In the current study, the effect of untreated flue gas as a source of inorganic carbon on the growth of Tetraselmis in a 1000 L industrial-scale split-cylinder internal-loop airlift photobioreactor was examined. The culture medium was recycled after each harvest. Tetraselmis suecica grew very well in this airlift photobioreactor during the 7-month experiment using recycled medium from an electroflocculation harvesting unit. Increased medium SO₄ ^2? concentration as high as 870 mg SO₄ ^2??L^?1 due to flue gas addition and media recycling had no negative effect on the overall growth and productivity of this alga. The potential organic biomass productivity and carbon sequestration using an industrial-scale airlift PBR at International Power Hazelwood, Gippsland, Victoria, Australia, are 178.9?±?30 mg L^?1 day^?1 and 89.15?±?20 mg?‘C’?L^?1 day^?1, respectively. This study clearly indicates the potential of growing Tetraselmis on untreated flue gas and using recycled medium for the purpose of biofuel and CO₂ bioremediation.     

Synthesis of some new <Emphasis Type="Italic">N</Emphasis>-substituted-<Emphasis Type="Italic">N</Emphasis>-(2,3-Dihydro-[1,4]benzodioxin-6-yl)-4-acetamidobenzenesulfonamides as valuable antibacterial agents

The aim of the research was to investigate the anti-bacterial potential of some N-substituted sulfonamides bearing benzodioxane moiety. The synthesis was started by reaction of N-2,3-dihydrobenzo[1,4]dioxin-6-amine with 4-acetamidobenzene-1-sulfonyl chloride in the presence of 10% aqueous Na₂CO₃ solution to yield N-(2,3-dihydrobenzo[1,4]-dioxin-6-yl)-4-acetamidobenzenesulfonamide, which was further reacted with alkyl/aralkyl halides in DMF and lithium hydride as a base to afford N-substituted-N-(2,3dihydro-[1,4]-benzodioxin-6-yl)-4-acetamidobenzenesulfonamides. All the synthesized compounds were characterized by spectral data (IR, ¹H NMR, EI-MS, and HR-MS). The compounds were tested for antibacterial activity and most of them exhibited potent therapeutic potential against various Gram-negative and Gram-positive strains.     

Effects of the interaction between vapor-pressure deficit and salinity on growth and photosynthesis of <Emphasis Type="Italic">Cucumis sativus</Emphasis> seedlings under different CO<Subscript>2</Subscript> concentrations

We studied growth and photosynthesis of cucumber (Cucumis sativus) seedlings under two vapor-pressure deficit levels (VPD; 0.4 and 3.0 kPa), two salinity levels (0 mM and 34 mM NaCl), and two CO₂ concentrations ([CO₂]; 400 and 1,000 μmol mol^–1). Relative growth rate (RGR) decreased with increasing VPD, but the causal factor differed between salinity levels and CO₂ concentrations. Under ambient [CO₂], RGR decreased with increasing VPD at low salinity mainly due to decreased leaf area ratio (LAR), and decreased net assimilation rate (NAR) at high salinity. The decrease in intercellular [CO₂] (C_i) with decreasing stomatal conductance caused by high VPD did not significantly limit net photosynthetic rate (P_N) at low salinity, but P_N was potentially limited by C_i at high salinity. At high [CO₂], high VPD reduced LAR, but did not affect NAR. This is because the decrease in C_i occurred where slope of P_N–C_i curve was almost flat.     

The dependence of intracellular ATP level on the nutrition mode of the acidophilic bacteria <Emphasis Type="Italic">Sulfobacillus thermotolerans</Emphasis> and <Emphasis Type="Italic">Alicyclobacillus tolerans</Emphasis>

The dynamics of the ATP pool in the aerobic spore-forming acidothermophilic mixotrophic bacteria Sulfobacillus thermotolerans Kr1^T and Alicyclobacillus tolerans K1^T were studied in the course of their chemolithoheterotrophic, chemoorganoheterotrophic, and chemolithoautotrophic growth. It was established that, during mixotrophic growth, the maximum ATP concentrations in the cells of S. thermotolerans Kr1 and A. tolerans K1 were 3.8 and 0.6 nmol/mg protein, respectively. The ATP concentrations in sulfobacilli and alicyclobacilli during organotrophic growth were 2.2 and 3.1 nmol/mg protein, respectively. In the cells of the obligately heterotrophic bacterium Alicyclobacillus cycloheptanicus 4006^T, the maximum ATP concentration was several times higher and reached 12.3 nmol/mg protein. During lithotrophic growth, the maximum values of the ATP concentration in the cells of S. thermotolerans Kr1 and A. tolerans K1 were 0.3 and <0.1 nmol/mg protein, respectively; in the cells of the autotrophic bacterium Acidithiobacillus ferrooxidans TFBk, the ATP content was about 60–300 times higher (17.0 nmol/mg protein). It is concluded that low ATP content is among the possible causes of growth cessation of S. thermotolerans Kr1 and A. tolerans K1 under auto-and heterotrophic conditions after several culture transfers.