Ethylene production in habituated and auxin-requiring tobacco callus cultures. Does ethylene play a role in the habituation?

Ethylene production of habituated and auxin-requiring tobacco ( Nicotiana tabacum L. cv. Xanthi) callus cultures were compared. More ethylene was produced by auxinrequiring i.e. auxin-heterotrophic cultures than by habituated ones. Treatment with 2,4-dichlorophenoxyacetic acid increased the ethylene evolution of habituated cultures over the range 10⁻⁷ to 10⁻⁴ M , which suggests that the higher ethylene production of auxin-dependent callus is caused by the 2,4-D in the medium. The IAA levels depended on the age of both types of callus cultures.     

小球藻RubisCO的纯化及其在异养向自养转变过程中的含量变化

经硫酸铵分部沉淀、ＳｅｐｈａｃｒｙｌＳ－３００和ＤＥＡＥ－纤维素柱层析纯化了小球藻ＲｕｂｉｓＣＯ,得率为１５％,比活力达１．２３２μｍｏｌＣＯ２ｍｓ－１ｍｉｎ－１,分子量是５００ｋＤ,它和菠菜叶片ＲｕｂｉｓＣＯ在分子量、亚基组成和免疫特性等方面相似,反映ＲｕｂｉｓＣＯ在高等和低等植物中有较高的同源性。自养小球藻ＲｕｂｉｓＣＯ占细胞可溶性蛋白质的２４％。而异养转变后的小球藻细胞内不含ＲｕｂｉｓＣＯ。异养小球藻向自养生长转变过程中,２０ｈ后细胞内叶绿素含量逐渐增加,２４ｈ时细胞内出现ＲｕｂｉｓＣＯ,２４ｈ后大量增加,至４１ｈ时含量达最高峰;标志着小球藻细胞光合作用能力的恢复和加强。     

Carbon flows in the Westerschelde estuary (The Netherlands) evaluated by means of an ecosystem model (MOSES)

The autotrophic production and heterotrophic consumption of organic matter in the Westerschelde, a highly turbid and eutrophic estuary in the Southwest Netherlands is examined by means of a dynamic simulation model. The model describes the ecologically relevant processes in thirteen spatial compartments and adequately fits most observed data.Three autotrophic processes are included in the model. Net pelagic photosynthetic production is relatively low (average 41 gC m^–2 yr^–1) and three spatial compartments near the turbidity maximum zone are respiratory sinks of phytoplankton biomass. According to the model, net phytobenthic primary production is more important than pelagic primary production in the upstream half of the Westerschelde. On the scale of the entire estuary, benthic primary production amounts to about 60% of pelagic primary production. Water-column nitrification, which is very important in the nitrogen cycle, is most pronounced near the turbidity zone where it accounts for the major autotrophic fixation of carbon (up to 27 g C m^–2 yr^–1). Viewed on the scale of the total estuary, however, the process is not very important.Less than 20% of total organic carbon input to the estuary is primary produced, the remainder is imported from waste discharges and from the river.The degree of heterotrophy of the Westerschelde estuary proved to be one of the highest yet reported. On average 380 g carbon per square metre is net lost per year (range 200–1200 gC m^–2 yr^–1). The yearly community respiration (bacterial mineralization, respiration of higher trophic levels and sedimentation) is 4 to 35 times (estuarine mean of 6) higher than the net production. This degree of heterotrophy is highest near the turbidity maximum and generally decreases from the freshwater to the seaward boundary. About 75% of all carbon losses can be ascribed to pelagic heterotrophic processes; the sediment is only locally important.Mineralisation rates are highest in the turbidity region, but as only a fraction of total carbon resides here, less than 20% of all organic carbon is lost in this part of the estuary. This result is in contradiction with a previous budget of the estuary, based on data of the early seventies, where more than 80% of all carbon was estimated to be lost in the turbidity zone. Part of this discrepancy is probably caused by changes that have occurred in the estuary since that time.Due to the high heterotrophic activity, nearly all imported and in situ produced carbon is lost in the estuary itself and the Westerschelde is an insignificant source of organic matter to the coastal zone.The model estuary acts as a trap for reactive organic matter, both from the land, from the sea or in situ produced. Internal cycling, mainly in the water column, results in the removal of most of the carbon while the more refractory part is exported to the sea.     

The use of disposable gaas generating kits for the growth of hydrogen-oxidizing bacteria and the determination of hydrogen autotrophy

A simplified procedure for the determination of autotropic growth of hydrogen-oxidizing bacteria has been developed. The method uses commercially available disposable hydrogen and carbon dioxide kits, commonly used in anaerobic bacteriology, to produce a gaseous atmosphre containing by volume approximately 41% hydrogen, 6% carbon dioxide, 11% oxygen and 42% nitrogen. The atmosphere was suitable for the growth of strains assigned to the species Alcaligenes eutrophus, Alcaligenes paradoxus, Paracoccus denitrificans, Pseudomonas facilis, Pseudomonas flava, Pseudomonas palleronii, Pseudomonas saccahrophilia and Rhodococcus sp. (‘Nocardia opaca’). The method can also be used for the screening of hydrogen-oxidizing ability in bacterial isolates, thus eliminating the need for complex gas mixing devices or expensive gas mixtures.     

Oxidation and Reduction of Iron by Acidophilic Bacteria

Abstract

Redox reactions of iron in acidic environments are of economic and environmental significance, for example, for the leaching of metal ores and for the formation of acid mine drainage and acid sulfate soils. Until recently, research on microbial iron metabolism in acidic environments has mainly been focused on the role of aerobic, autotrophic ferrous iron‐oxidizing bacteria. In the present paper, recent new developments in the field of acidophilic iron metabolism are reviewed. In addition to the well‐known autotrophic ferrous iron‐oxidizing organisms, new heterotrophic isolates have been described that are capable of oxidizing ferrous iron. Microorganisms can also play an important role in the reductive part of the iron cycle. Both heterotrophic and autotrophic organisms may also be involved in this process. The contribution of heterotrophic organisms to acidophilic iron cycling can be twofold: In addition to their direct role as a catalyst, these organisms may scavenge organic compounds that inhibit their autotrophic counterparts. Detailed studies of acidophilic ecosystems are needed to assess the significance of the various types of microorganisms for the overall rate of iron cycling in these extreme environments.     

Comparative study of nutritional mode and mycorrhizal fungi in green and albino variants of Goodyera velutina,an orchid mainly utilizing saprotrophic rhizoctonia

The majority of chlorophyllous orchids form mycorrhizal associations with so‐called rhizoctonia fungi, a phylogenetically heterogeneous assemblage of predominantly saprotrophic fungi in Ceratobasidiaceae, Tulasnellaceae, and Serendipitaceae. It is still a matter of debate whether adult orchids mainly associated with rhizoctonia species are partially mycoheterotrophic. Here, we investigated the nutritional modes of green and albino variants of Goodyera velutina, an orchid species considered to be mainly associated with Ceratobasidium spp., by measuring their ¹³C and ¹⁵N abundances, and by molecular barcoding of their mycorrhizal fungi. Molecular analysis revealed that both green and albino variants of G. velutina harbored a similar range of mycobionts, mainly saprotrophic Ceratobasidium spp., Tulasnella spp., and ectomycorrhizal Russula spp. In addition, stable isotope analysis revealed that albino variants were significantly enriched in ¹³C but not so greatly in ¹⁵N, suggesting that saprotrophic Ceratobasidium spp. and Tulasnella spp. are their main carbon source. However, in green variants, ¹³C levels were depleted and those of ¹⁵N were indistinguishable from the co‐occurring autotrophic plants. Therefore, we concluded that the albino G. velutina variants are fully mycoheterotrophic plants whose C derives mainly from saprotrophic rhizoctonia, while the green G. velutina variants are mainly autotrophic plants, at least at our study site, in spite of their additional associations with ectomycorrhizal fungi. This is the first report demonstrating that adult nonphotosynthetic albino variants can obtain their nutrition mainly from nonectomycorrhizal rhizoctonia.     

Description of “<Emphasis Type="Italic">Desulfotomaculum nigrificans</Emphasis> subsp. <Emphasis Type="Italic">salinus</Emphasis>” as a New Species, <Emphasis Type="Italic">Desulfotomaculum salinum</Emphasis> sp. nov.

This study focused on the physiological, chemotaxonomic, and genotypic characteristics of two thermophilic spore-forming sulfate-reducing bacterial strains, 435^T and 781, of which the former has previously been assigned to the subspecies “Desulfotomaculum nigrificans subsp. salinus”. Both strains reduced sulfate with the resulting production of H₂S on media supplemented with H₂ + CO₂, formate, lactate, pyruvate, malate, fumarate, succinate, methanol, ethanol, propanol, butanol, butyrate, valerate, or palmitate. Lactate oxidation resulted in acetate accumulation; butyrate was oxidized completely, with acetate as an intermediate product. Growth on acetate was slow and weak. Sulfate, sulfite, thiosulfate, and elemental sulfur, but not nitrate, served as electron acceptors for growth with lactate. The bacteria performed dismutation of thiosulfate to sulfate and hydrogen sulfide. In the absence of sulfate, pyruvate but not lactate was fermented. Cytochromes of b and c types were present. The temperature and pH optima for both strains were 60–6°C and pH 7.0. Bacteria grew at 0 to 4.5–6.0% NaCl in the medium, with the optimum being at 0.5–1.0%. Phylogenetic analysis based on a comparison of incomplete 16S rRNA sequences revealed that both strains belonged to the C cluster of the genus Desulfotomaculum, exhibiting 95.5–98.3% homology with the previously described species. The level of DNA–DNA hybridization of strains 435^T and 781 with each other was 97%, while that with closely related species D. kuznetsovii 17^T was 51–52%. Based on the phenotypic and genotypic properties of strains 435^T and 781, it is suggested that they be assigned to a new species: Desulfotomaculum salinum sp. nov., comb. nov. (type strain 435^T = VKM B 1492^T).     

Callus induction and culture from explants of Erysimum scoparium in a growth regulator-free medium

Calli from cotyledon, hypocotyl and radicle explants of Erysimum scoparium (Brassicaceae) were induced and cultured using a MS medium without growth regulators. Calli obtained from cotyledon or hypocotyl explants showed a higher growth rate while radicle-derived calli exhibited poor growth. Cotyledon-derived calli were compact and green-colored while hypocotyl- and radicle-derived calli were friable and with creamy-green pigmentation. Histological analysis was carried out during culture and the development of abundant vascular elements and meristematic nodules were found. Subculture on a growth regulator-free medium during 10 months did not ecrease callus growth.     

Relationship of indole-3-acetic acid and tryptophan concentrations in normal and 5-methyltryptophan-resistant cell lines of wild carrots

A 5-methyltryptophan(5-MT)-resistant cell line of wild carrot (Daucus carota L.), W001, that exhibited auxin-independent callus growth, was found to accumulate indole-3-acetic acid (IAA) and tryptophan (trp). Anthranilate-synthetase activity in W001 cell extract was less sensitive to feedback inhibition by trp than in the original 5-MT-sensitive cell lines. It is hypothesized that the resistant enzyme allowed more trp synthesis and accumulation which, in turn, affected the IAA concentration in the cell. Since carrot cultures cannot regenerate in the presence of exogenous auxin, the elevated IAA concentration in W001 may be responsible for its drastically reduced capacity to regenerate. The relationship between trp and IAA levels was further investigated by examining the effect of 2,4-dichlorophenoxy acetic acid (2,4-D) on the endogenous concentration of trp and IAA. In general, the IAA level was reduced but the trp concentration was elevated when 2,4-D was present in the culture medium.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - 5-MT 5-methyltryptophan - 5-MT^r 5-MT-resistant - 5-MT^s 5-MT-sensitive - trp tryptophan     

Relation between auxin autotrophy and tryptophan accumulation in cultured plant cells

Auxin autotrophy was studied in cultured carrot (Daucus carota L.), tobacco (Nicotiana tabacum L.), and potato (Solanum tuberosum L.) cell lines. Of 10 carrot lines resistant to 5-methyltryptophan (5MT), which accumulate free tryptophan (trp) because of an altered control enzyme, 5 were auxinautotrophic while the normal parent line was not. Carrot lines selected from the same parent line as resistant to other amino-acid analogs were not auxinautotrophic, like the parent. The only 5MT-resistant potato line studied was also auxin-autotrophic while the normal line was only partially auxin-autotrophic. The tobacco lines which accumulated free trp were not auxin-autotrophic, and no auxin-autotrophic tobacco lines were selected by screening for growth in medium lacking 2,4-dichlorophenoxyacetic acid (2,4-D). Several auxin-autotrophic carrot and potato lines were selected from the normal lines and none of these lines were resistant to 5MT. Length of time in culture and difficulty in selecting auxin-autotrophic lines were correlated on the 3 normal carrot lines studied. The addition of trp or indole to the culture medium would partially alleviate the auxin requirement of the normal lines studied. 2,4-D (0.4 mg/l) stimulated the growth of all auxin-autotrophic carrot lines.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - PEP DL-p-fluorophenylalanine - IAA indole-3-acetic acid - 5MT DL-5-methyltryptophan - trp L-tryptophan