Fine Structure of Thiobacillus thiooxidans

Mahoney, Robert P. (Skidmore College, Saratoga Springs, N.Y.), and Mercedes R. Edwards. Fine structure of Thiobacillus thiooxidans. J. Bacteriol. 92: 487-495. 1966.-Thin section analysis of the chemosynthetic autotroph Thiobacillus thiooxidans revealed structures comparable to gram-negative heterotrophic bacteria. Although this species is unique in that it oxidizes elemental sulfur for energy, uses carbon dioxide as its sole source of carbon, and can withstand a pH of less than 1, thin sections revealed a profile of the cell envelope (cell wall and plasmalemma) similar to other gram-negative species which have more common physiological traits. The cell wall is composed of five layers with an overall width of approximately 200 A, and the plasmalemma appears as a conventional "unit membrane" with a width of about 85 A. Volutin granules and less-dense bodies of similar shape and size were frequently observed in close association with the nucleoplasm. The nature and function of these bodies are unknown at this time.     

A quantitative comparison of dual control of a hormone response element by progestins and glucocorticoids in the same cell line

Progesterone receptor-containing T47D human breast cancer cells are responsive to progestins but fail to respond to other steroid hormones, in particular dexamethasone, because they have no measurable levels of receptors for estrogens, androgens, or glucocorticoids. To quantitatively study dual responsiveness of the mouse mammary tumor virus (MMTV) promoter to progestins and glucocorticoids, we have stably transfected T47D cells with a glucocorticoid receptor (GR) expression vector. A cloned derivative (A1-2) was isolated that expresses a normal, full length GR, as assessed by steroid binding and Western immunoblot with a monoclonal anti-GR antibody. Moreover, GR is expressed at levels (80,000-100,000 molecules per cell) comparable to the high levels of endogenous progesterone receptor (200,000 molecules per cell). In A1-2 cells transiently transfected with an MMTV-chloramphenicol acetyl transferase reporter gene, induction by glucocorticoid was substantially greater (5-fold) than induction mediated by progestins. These results suggest that glucocorticoids may be the primary regulator of MMTV.     

Spatial Analysis of the Canopy of Kiwifruit Vines as it Relates to the Physical, Chemical and Postharvest Attributes of the Fruit

The position of individual fruit on kiwifruit vines (Actinidiadeliciosa var. deliciosa) grown on a horizontal trellis (pergola)and on a T-bar trellis was determined using a theodolite. Thephysical, chemical, and postharvest attributes of the fruitwere related to their position on the vine during development. Fruit from the pergola vines were more numerous, of lesser weight,with lower concentrations of most mineral nutrients, but greaterconcentrations of soluble solids, and similar flesh firmnessafter 12 weeks of storage at 0 °C, than fruit from the T-barvines. The position on the vine accounted for most of the variationin the attributes of the fruit. Differences between fruit ona single lateral accounted for 43-56% of the variation. Variationbetween vines was relatively small (< 4% of the total variance). The heavier fruit were located at the apical ends of the laterals,while greater concentrations of soluble solids were associatedwith fruit located closer to the cordon. The larger fruit fromthe pergola vines developed from the early opening flowers.A similar relationship existed initially for the T-bar vines,but a reduction in growth of fruit from the early opening flowers8 weeks after anthesis resulted in a more even distributionof fruit size at harvest. The strongest relationship between mineral composition and postharvestattributes of the fruit was with soluble solids concentration(29-46% of the variance). The relationship with flesh firmnesswas weak (r = -0·14 to -0·32). Individual elementscould not be considered in isolation but rather in groups ofelements. Nitrogen was grouped strongly with phosphorus, sulphur,potassium, and copper, while calcium was linked with a secondgroup which included manganese and zinc. These two groups werenegatively related to one another. The greatest proportion of fruit with superior characteristicswas located in the denser parts of the canopy. Fruit with lessdesirable attributes were from the extremities of the canopywhere the leaf area index was low.Copyright 1994, 1999 AcademicPress Actinidia deliciosa, kiwifruit, fruit position, fruit quality, within-vine variation     

Role of proteinaceous amino acids released in root exudates in nutrient acquisition from the rhizosphere

The role of proteinaceous amino acids in rhizosphere nutrient mobilization was assessed both experimentally and theoretically. The degree of adsorption onto the soil's solid phase was dependent on both the amino acid species and on soil properties. On addition of amino acids to both soil and freshly precipitated Fe(OH)₃, no detectable mobilization of nutrients (K, Na, Ca, Mg, Cu, Mn, Zn, Fe, S, P, Si and Al) was observed, indicating a very low complexation ability of the acidic, neutral and basic amino acids. This was supported by results from a solution equilibria computer model which also predicted low levels of amino acid complexation with solutes present in the soil solution. On comparison with the Fe(OH)₃ and equilibria data obtained for the organic acid, citrate, it was concluded that amino acids released into the rhizosphere have a limited role in the direct acquisition of nutrients by plants. The effectiveness of root exudates such as amino acids, phytosiderophores and organic acids in nutrient mobilization from the rhizosphere is discussed with reference to rhizosphere diffusion distances, microbial degradation, rate of complexation and the root's capacity to recapture exudate-metal complexes from the soil.     

Isolation of glucosinolate degrading microorganisms and their potential for reducing the glucosinolate content of rapemeal

Abstract K88ab fimbriae are filamentous protein structures at the surface of certain enterotoxigenic Escherichia coli strains. Electron microscopy analysis of K88ab fimbriae showed that these structures have different morphological appearances dependent on the medium in which cells expressing these fimbriae or in which purified fimbriae were suspended. Thin and curled structures, thin and flexible fimbriae, a wider and rigid form of the fimbriae, and, in addition, paracrystalline structures were detected. Optical diffraction analysis of the paracrystalline structures indicated a helical conformation of K88ab fimbriae.     

Origin of the main class of repetitive DNA within selected Pennisetum species

In an attempt to identify relationships among genomes of the allotetraploid Pennisetum purpureum Schumach and closely related Pennisetum species with which it can be successfully hybridized, repetitive DNA sequences were examined. Digestion with KpnI revealed two highly repetitive fragments of 140 by and 160 bp. The possibility that these sequences could be used as genome markers was investigated. Average sequences were determined for the 140 by and 160 by KpnI families from P. purpureum and P. squamulatum Fresen. Average sequences (based upon four or five repeats) were determined for the P. glaucum (L.) R. Br. 140 by KpnI family and the diploid P. hohenackeri Hochst. ex Steud. 160 bp KpnI family. The average sequences of the 160 by KpnI families in P. purpureum and P. squamulatum differ by only nine bases. The 140 by KpnI families of the three related species, P. purpureum, P. squamulantum, and P. glaucum are nearly identical, and thus likely represent a recent divergence from a common progenitor or a common genome. Each repetitive sequence may contain internal duplications, which probably diverged following amplification of the original sequence. The 140 by KpnI repeat probably evolved from the 160 by KpnI repeat since the missing 18 by segment is part of the internal duplication that is otherwise conserved in the subrepeats. Tandemly arrayed repetitive sequences in plants are likely to be composed of subrepeats which have been duplicated and amplified.Florida Aqricultural Experiment Station series #R-02758     

Interactive effects of rising temperatures and urbanisation on birds across different climate zones: A mechanistic perspective

Climate change and urbanisation are among the most pervasive and rapidly growing threats to biodiversity worldwide. However, their impacts are usually considered in isolation, and interactions are rarely examined. Predicting species' responses to the combined effects of climate change and urbanisation, therefore, represents a pressing challenge in global change biology. Birds are important model taxa for exploring the impacts of both climate change and urbanisation, and their behaviour and physiology have been well studied in urban and non-urban systems. This understanding should allow interactive effects of rising temperatures and urbanisation to be inferred, yet considerations of these interactions are almost entirely lacking from empirical research. Here, we synthesise our current understanding of the potential mechanisms that could affect how species respond to the combined effects of rising temperatures and urbanisation, with a focus on avian taxa. We discuss potential interactive effects to motivate future in-depth research on this critically important, yet overlooked, aspect of global change biology. Increased temperatures are a pronounced consequence of both urbanisation (through the urban heat island effect) and climate change. The biological impact of this warming in urban and non-urban systems will likely differ in magnitude and direction when interacting with other factors that typically vary between these habitats, such as resource availability (e.g. water, food and microsites) and pollution levels. Furthermore, the nature of such interactions may differ for cities situated in different climate types, for example, tropical, arid, temperate, continental and polar. Within this article, we highlight the potential for interactive effects of climate and urban drivers on the mechanistic responses of birds, identify knowledge gaps and propose promising future research avenues. A deeper understanding of the behavioural and physiological mechanisms mediating species' responses to urbanisation and rising temperatures will provide novel insights into ecology and evolution under global change and may help better predict future population responses.