bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of antibiotics on conjugational resistance gene transfer in Staphylococcus aureus in sewage
Authors: Ohlsen Knut , Ternes Thomas , Werner Guido , Wallner Ursula , Löffler Dirk , Ziebuhr Wilma , Witte Wolfgang , Hacker Jörg 
Published: July 2003

SummaryThe growing rate of microbial pathogens becoming resistant to standard antibiotics is an important threat to public health. In order to assess the role of antibiotics in the environment on the spread of resistance factors, the impact of subinhibitory concentrations of antibiotics in sewage on gene transfer was investigated using conjugative gentamicin resistance (aacA–aphD) plasmids of Staphylococcus aureus. Furthermore, the concentration of antibiotics in hospital sewage was measured by high‐performance liquid chromatography (HPLC)–electrospray tandem mass spectrometry. Several antibiotics were found to be present in sewage, e.g. ciprofloxacin up to 0.051 mg l−1 and erythromycin up to 0.027 mg l−1. Resistance plasmid transfer occurred both on solidified (dewatered) sewage and in liquid sewage in a bioreactor with a frequency of 1.1 × 10−5−5.0 × 10−8. However, low‐level concentrations of antibiotics measured in sewage are below concentrations that can increase plasmid transfer frequencies of gentamicin resistance plasmids of staphylococci.
Geographical isolation in hot spring cyanobacteria
Authors: Papke R. Thane , Ramsing Niels B. , Bateson Mary M. , Ward David M. 
Published: July 2003

SummaryIt has been proposed that free‐living microorganisms exhibit ubiquitous dispersal, do not form geographically isolated populations and rarely (if ever) speciate via allopatry. We studied island‐like hot spring cyanobacterial communities in which geographical isolation should be prominent and detectable if it influences the evolution of bacteria. The genetic diversity of cyanobacteria indigenous to North American, Japanese, New Zealand and Italian springs was surveyed by (i) amplification and cloning of 16S rRNA and 16S−23S internal transcribed spacer regions; (ii) lineage‐specific oligonucleotide probing (used to verify the predominance of cloned sequences); and (iii) lineage‐specific polymerase chain reaction (PCR) (used to search for possible rare genotypes). Phylogenetic and distribution patterns were found to be consistent with the occurrence of geographical isolation at both global and local spatial scales, although different cyanobacterial lineages were found to vary in their distribution. A lack of correspondence between biological patterning and the chemical character of springs sampled suggested that the geographical distribution of thermophilic cyanobacteria cannot be explained by the 20 potential niche‐determining chemical parameters that we assayed. Thus, geographical isolation (i.e. genetic drift) must in part be responsible for driving the observed evolutionary divergences. Geographical isolation may be an important underestimated aspect of microbial evolution.
The hidden lifestyles of Bacillus cereus and relatives
Authors: Jensen G. B. , Hansen B. M. , Eilenberg J. , Mahillon J. 
Published: July 2003

Summary Bacillus cereus sensu lato, the species group comprising Bacillus anthracis, Bacillus thuringiensis and B. cereus (sensu stricto), has previously been scrutinized regarding interspecies genetic correlation and pathogenic characteristics. So far, little attention has been paid to analysing the biological and ecological properties of the three species in their natural environments. In this review, we describe the B. cereus sensu lato living in a world on its own; all B. cereus sensu lato can grow saprophytically under nutrient‐rich conditions, which are only occasionally found in the environment, except where nutrients are actively collected. As such, members of the B. cereus group have recently been discovered as common inhabitants of the invertebrate gut. We speculate that all members disclose symbiotic relationships with appropriate invertebrate hosts and only occasionally enter a pathogenic life cycle in which the individual species infects suitable hosts and multiplies almost unrestrained.
Photoreceptors and cone patterns in the retina of the smelt Osmerus eperlanus (L.) (Osmeridae: Teleostei)
Authors: Reckel F. , Hoffmann B. , Melzer R. R. , Horppila J. , Smola U. 
Published: July 2003

AbstractThe outer retina of the smelt Osmerus eperlanus, a visually orientated plankton feeder, of Lake Hiidenvesi (Finland), was examined using both light and transmission electron microscopy. Apart from rods, six morphologically different cone photoreceptor types were identified: short single cones, long single cones, unequal/equal double cones and triple cones (triangular and linear variety). Additionally, in the dorsal region, multiple cone arrangements consisting of up to five members occur. Long single cones and triple cones were observed only sporadically throughout the retina. The incidence of short single cones as a regular element of the cone mosaic is restricted to the ventrotemporal area. The dominant pattern in the Osmerus retina is a pure or a twisted row pattern occurring in all regions. Ventrotemporally, however, square patterns were found as well. The highest cone densities occur in the peripheral ventrotemporal retina. These results indicate that the ventrotemporal region plays an important role in the vision of the smelt. The findings are discussed with respect to the photic habitat conditions and behavioural ecology of the smelt in Lake Hiidenvesi.
Ultrastructure and overall organization of ligament sac, uterine bell, uterus and vagina in Paratenuisentis ambiguus (Acanthocephala, Eoacanthocephala) – the character evolution within the Acanthocephala
Authors: Herlyn H. , Röhrig H. 
Published: July 2003

AbstractAs an adaptation to their endoparasitic lifestyle, Acanthocephala (Palaeacanthocephala, Eoacanthocephala, Polyacanthocephala, Archiacanthocephala) have evolved a highly specialized reproductive system. Most of our present knowledge of the efferent duct system of the female is based on palaeacanthocephalan and archiacanthocephalan representatives. In order to provide a basis for further elucidating the phylogenetic relationships within the Acanthocephala, we herein describe ultrastructure and overall organization of the ligament sac and efferent duct system in females of Paratenuisentis ambiguus (Eoacanthocephala, Neoechinorhynchida). Only one ligament sac was found. The uterine bell consists of two contractile binucleate syncytia (bell wall syncytium, lateral pocket syncytium), two pairs of contractile cells (lappet cells, uterine bell retractors) and three pairs of noncontractile cells (median cells). The contractile uterus bears four nuclei. The vagina is composed of a syncytial epithelium (four nuclei) and two binucleate sphincters. A comparison of the present findings with literature data leads to the following conclusions: except for the uterine bell retractors, the uterine bell components found in P. ambiguus can be assumed to be autapomorphies for the Acanthocephala. The sheathing syncytium and median dorsal cell belong to the basal pattern (sensu ground pattern) of a palaeacanthocephalan subclade termed the Echinorhynchus‐group in the present study. The median oviduct syncytium and paired uterine bell retractors can be assumed to be basal pattern characteristics of the Archiacanthocephala and Neoechinorhynchida, respectively. The study includes a tabular survey of terminological synonyms used in the literature.
Ultrastructural and immunocytochemical observations of the nervous systems of three macrodasyidan gastrotrichs
Authors: Hochberg R. , Litvaitis M. K. 
Published: July 2003

AbstractThe nervous systems of three macrodasyidan gastrotrichs, Dactylopodola baltica, Macrodasys caudatus and Dolichodasys elongatus, were investigated using immunocytochemistry and electron microscopy. Labelling of neural structures against serotonin revealed the presence of two pairs of cerebral cells, a dorsal cerebral connective, and paired ventral nerve cords in D. baltica. In M. caudatus and D. elongatus serotonin immunoreactivity was present in a single pair of dorsal cerebral cells and the ventral nerve cords; the dorsal connective of D. elongatus was also immunoreactive to serotonin and acetylated α‐tubulin. The presence of paired, serotonin‐like immunoreactive cells in D. baltica and other species may represent the plesiomorphic condition in Macrodasyida. The fine structure of the photoreceptors in D. baltica was also investigated to explore the potential ground pattern for eyes in the Macrodasyida. The pigmented photoreceptors of D. baltica contain a unicellular pigment cup, sheath cell and sensory receptor. The pigment cup contains numerous osmiophilic granules that presumably function to shield the eyes from downwelling light in the red part of the spectrum. Projecting into the pigment cup and sheath cell are numerous microvilli from a bipolar sensory cell. A single sensory cell may represent the plesiomorphic condition in Macrodasyida, with multiplication of sensory cells representative of more derived taxa.
Comparative morphology and evolutionary pathways of the mouthparts in spore‐feeding Staphylinoidea (Coleoptera)
Authors: Betz Oliver , Thayer Margaret K. , Newton Alfred F. 
Published: July 2003

AbstractThis study surveys the external morphology of the mouthparts in the guild of spore‐feeders among the coleopterous superfamily Staphylinoidea, evaluating the influence of different phylogenetic and ecological starting points on the formation of their mouthparts. Our emphasis is on a scanning electron microscope analysis (SEM) of the involved trophic structures in spore‐feeding larvae and adults of the Ptiliidae, Leiodidae and Staphylinidae, describing the fine structure of their main functional elements. Functionally, mouthpart structures resemble brushes, brooms, combs, rakes, rasps, excavators, knives, thorns, cram‐brushes, bristle troughs, blocks and differently structured grinding surfaces. Their different involvement in the various aspects of the feeding process (i.e. food gathering, transporting, channelling and grinding) is deduced from our SEM analyses plus direct video observations. We infer five different patterns of food transport and processing, discriminating adults of ptiliids, leiodids plus staphylinids (excluding some aleocharines), several aleocharine staphylinids, and the larvae of leiodids and staphylinids. The structural diversity of the mouthparts increases in the order from (1) Ptiliidae, (2) Leiodidae towards (3) Staphylinidae, reflecting the increasing systematic and ecological diversity of these groups. Comparisons with non‐spore‐feeders show that among major lineages of staphylinoids, shifts from general microphagy to sporophagy are not necessarily constrained by, nor strongly reflected in, mouthpart morphology. Nevertheless, in several of these lineages the organs of food intake and grinding have experienced particular fine‐structural modifications, which have undergone convergent evolution, probably in response to specialized mycophagy such as spore‐feeding. These modifications involve advanced galeal rakes, galeal or lacinial ‘spore brushes’ with arrays of stout bristles, reinforced obliquely ventrad orientated prosthecal lobes and the differentiations of the molar grinding surfaces into stout teeth or tubercles. In addition, several staphylinids of the tachyporine and oxyteline groups with reduced mandibular molae have evolved secondary trituration surfaces, which in some aleocharines are paralleled by considerable re‐constructions of the labium–hypopharynx.
Stable transgene expression and random gene silencing in wheat
Authors: Anand Ajith , Trick Harold N. , Gill Bikram S. , Muthukrishnan Subbaratnam 
Published: July 2003

SummaryWheat genes for pathogenesis‐related (PR‐)proteins, chitinase and β‐1,3‐glucanase, under the control of maize ubiquitin promoter‐intron were used for transforming the spring wheat ‘Bobwhite’, using a biolistic approach. Twenty of the 24 primary transgenic lines expressing the PR‐protein genes in the T0 generation were silenced in either the T1 or T2 generations. Two apparently genetically identical regenerants arising from a single callus co‐bombarded with chitinase and β‐1,3‐glucanase transgene combinations, but differing in the expression of the transgenes were selected for further characterization. In one homozygous line, transgene silencing was observed in the T3 plants, while the other line homozygous for the transgene loci stably expressed and inherited the transgenes to at least the T4 generation. Southern blot analyses of genomic DNA from the two lines using the isoschizomeric methylation‐sensitive enzymes, MspI and HpaII, revealed a higher degree of methylation of CCGG sequences in the line with the silenced transgene locus. Analysis by reverse transcriptase‐polymerase chain reaction, Northern blotting and Western blotting detected stable expression of the transgenes in the line with a lesser extent of methylation, whereas the line with a higher level of CCGG methylation had no transgene expression by the T3 generation. The germination of seeds from the silenced plants in the presence of a cytidine analogue, 5‐azacytidine (azaC), did not lead to a reversion of this phenotype.
A sequence mutation in the cinnamyl alcohol dehydrogenase gene associated with altered lignification in loblolly pine
Authors: Gill Geoffrey P. , Brown Garth R. , Neale David B. 
Published: July 2003

SummaryEvidence for the molecular basis of a null allele of cinnamyl alcohol dehydrogenase (CAD) has been discovered in the loblolly pine (Pinus taeda L.) clone 7‐56. The mutation is a two‐base pair adenosine insertion located in exon 5 that causes a frame‐shift which is predicted to result in premature termination of the protein. For routine detection of the mutation, a diagnostic assay was developed utilizing Template‐directed Dye‐terminator Incorporation and Fluorescence Polarization detection (FP‐TDI). Loblolly pine is the most important commercial tree species in the USA, being harvested for pulp and solid wood products. Chemical pulping could be increased in efficiency by selecting for trees having a two‐base pair adenosine insertion, by use of the rapid diagnostic assay developed in this study.
Characterization of a gene from chromosome 1B encoding the large subunit of ADPglucose pyrophosphorylase from wheat: evolutionary divergence and differential expression ofAgp2genes between leaves and developing endosperm
Authors: Thorneycroft David , Hosein Felicia , Thangavelu Madan , Clark Joanna , Vizir Igor , Burrell Michael M. , Ainsworth Charles 
Published: July 2003

SummaryA full‐length genomic clone containing the gene encoding the large subunit of the ADPglucose pyrophosphorylase (Agp2), was isolated from a genomic library prepared from etiolated shoots of hexaploid wheat (Triticum aestivumL., cv, Chinese Spring). The coding region of this gene is identical to one of the cDNA clones previously isolated from a developing wheat grain cDNA library and is therefore an actively transcribed gene. The sequence represented by the cDNA spans 4.8 kb of the genomic clone and contains 15 introns. 2852 bp of DNA flanking the transcription start site of the gene was cloned upstream of the GUS (β‐glucuronidase) reporter gene. ThisAgp2::GUS construct and promoter deletions were used to study the pattern of reporter gene expression in both transgenic tobacco and wheat plants. Histochemical analysis of GUS expression in transgenic tobacco demonstrated that the reporter gene was expressed in guard cells of leaves and throughout the seed. In transgenic wheat, reporter gene expression was confined to the endosperm and aleurone with no expression in leaves. The clonedAgp2gene was located to chromosome 1B by gene‐specific PCR with nullisomic–tetrasomic lines. Northern analysis demonstrated that theAgp2genes are differentially expressed in leaves and developing endosperm; while all three classes ofAgp2genes are transcribed in developing wheat grain endosperm, only one is transcribed in leaves. The differences between theAgp2genes are discussed in relation to the evolution of hexaploid wheat.
Global transcript analysis of rice leaf and seed using SAGE technology
Authors: Gibbings J. George , Cook Brian P. , Dufault Michael R. , Madden Stephen L. , Khuri Sawsan , Turnbull Chris J. , Dunwell Jim M. 
Published: July 2003

SummaryWe have compiled two comprehensive gene expression profiles from mature leaf and immature seed tissue of rice (Oryza sativa ssp. japonica cultivar Nipponbare) using Serial Analysis of Gene Expression (SAGE) technology. Analysis revealed a total of 50 519 SAGE tags, corresponding to 15 131 unique transcripts. Of these, the large majority (∼70%) occur only once in both libraries. Unexpectedly, the most abundant transcript (∼3% of the total) in the leaf library was derived from a type 3 metallothionein gene. The overall frequency profiles of the abundant tag species from both tissues differ greatly and reveal seed tissue as exhibiting a non‐typical pattern of gene expression characterized by an over abundance of a small number of transcripts coding for storage proteins. A high proportion (∼80%) of the abundant tags (≥ 9) matched entries in our reference rice EST database, with many fewer matches for low abundant tags. Singleton transcripts that are common to both tissues were collated to generate a summary of low abundant transcripts that are expressed constitutively in rice tissues. Finally and most surprisingly, a significant number of tags were found to code for antisense transcripts, a finding that suggests a novel mechanism of gene regulation, and may have implications for the use of antisense constructs in transgenic technology.
Expression of Vitreoscilla haemoglobin in hybrid aspen (Populus tremula × tremuloides)
Authors: Häggman Hely , Frey Alexander D. , Ryynänen Leena , Aronen Tuija , Julkunen‐Tiitto Riitta , Tiimonen Heidi , Pihakaski‐Maunsbach Kaarina , Jokipii Soile , Chen Xiwen , Kallio Pauli T. 
Published: July 2003

SummaryWe describe the first ever expression of Vitreoscilla haemoglobin (VHb) in an economically important boreal woody plant hybrid aspen (Populus tremula×tremuloides). VHb has mainly been expressed in biotechnologically important unicellular organisms of both prokaryotic and eukaryotic origin. VHb expression, in this study, was analysed under different greenhouse cultivation conditions and under elevated UV‐B illumination. Microscope analyses of leaves grown under optimized conditions revealed significant differences both in cell structure and size when the transgenic VHb lines were compared with the control lines. VHb lines displayed a higher relative volume of mitochondria and a significantly enhanced accumulation of starch in chloroplasts, all of which pointed towards changes in cellular energy production. Under elevated UV‐B illumination, the differences between VHb lines became evident. Some specific VHb lines had elevated levels of total flavonoids, individual quercetin, kaempferol‐ and myricetin‐derivatives relative to controls and other transgenic lines. This observation may reflect the availability of extra energy resources for secondary metabolite production and possibly an enhanced protection ability of these transgenic lines against UV‐B illumination. Thus, all these findings point to changes in the energy metabolism of VHb lines. In the cultivation conditions tested this observation did not, however, result in a general improvement of elongation growth.
Seed‐expressed fluorescent proteins as versatile tools for easy (co)transformation and high‐throughput functional genomics in Arabidopsis
Authors: Stuitje Antoine R. , Verbree Elizabeth C. , Van Der Linden Karin H. , Mietkiewska Elzbieta M. , Nap Jan‐Peter , Kneppers Tarcies J. A. 
Published: July 2003

SummaryWe demonstrate that fluorescent proteins can be used as visual selection markers for the transformation of Arabidopsis thaliana by the floral dip method. Seed‐specific expression of green fluorescent protein (GFP) variants, as well as DsRed, permits the identification of mature transformed seeds in a large background of untransformed seeds by fluorescence microscopy. In planta visualization of transformed seeds in siliques shows that susceptibility to floral dip transformation is limited to a small, defined window in flower development. In the competent stage, the random transformation of up to 25% of the seeds within a single silique may occur. The use of fluorescent proteins with different spectral characteristics allows a rapid identification and genetic analysis of seeds that have received multiple genes‐of‐interest in co‐transformation experiments. The data reveal that co‐transformation does not occur at random, since the co‐transformed genes are integrated at a single genetic locus in ≈ 70% of the cases. This genetic linkage of the co‐transformed genes greatly simplifies metabolic pathway engineering by reverse genetics in Arabidopsis. Additional advantages of using visual selection instead of antibiotic resistance include a rapid identification of the effect of the T‐DNA insertion or the transgene on seed development and/or germination. This technology, of tagging and identifying transformed seeds by fluorescence provides a novel high‐throughput screening system with many potential applications in plant biotechnology.
Expression of mercuric ion reductase in Eastern cottonwood (Populus deltoides) confers mercuric ion reduction and resistance
Authors: Che Dongsheng , Meagher Richard B. , Heaton Andrew C. P. , Lima Amparo , Rugh Clayton L. , Merkle Scott A. 
Published: July 2003

SummaryMercury is one of the most hazardous heavy metals and is a particular problem in aquatic ecosystems, where organic mercury is biomagnified in the food chain. Previous studies demonstrated that transgenic model plants expressing a modified mercuric ion reductase gene from bacteria could detoxify mercury by converting the more toxic and reductive ionic form [Hg(ii)] to less toxic elemental mercury [Hg(0)]. To further investigate if a genetic engineering approach for mercury phytoremediation can be effective in trees with a greater potential in riparian ecosystems, we generated transgenic Eastern cottonwood (Populus deltoides) trees expressing modified merA9 and merA18 genes. Leaf sections from transgenic plantlets produced adventitious shoots in the presence of 50 µm Hg(ii) supplied as HgCl2, which inhibited shoot induction from leaf explants of wild‐type plantlets. Transgenic shoots cultured in a medium containing 25 µm Hg(ii) showed normal growth and rooted, while wild‐type shoots were killed. When the transgenic cottonwood plantlets were exposed to Hg(ii), they evolved 2–4‐fold the amount of Hg(0) relative to wild‐type plantlets. Transgenic merA9 and merA18 plants accumulated significantly higher biomass than control plants on a Georgia Piedmont soil contaminated with 40 p.p.m. Hg(ii). Our results indicate that Eastern cottonwood plants expressing the bacterial mercuric ion reductase gene have potential as candidates for in situ remediation of mercury‐contaminated soils or wastewater.