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Armillaria mellea can infect the perennial weed, Rumex obtusifolius, in the UK (2000)

West, J. S. ; Hughes, C. ; Fox, R. T. V.

Oxford, UK : Blackwell Science Ltd

Plant pathology 49 (2000), S. 0

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ISSN: 1365-3059

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3059.2000.00517.x

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Relationship between natural occurrence of banana streak badnavirus and symptom expression, relative concentration of viral antigen, and yield characteristics of some micropropagated Musa spp. (2000)

Dahal ; Ortiz ; Tenkouano ; [et al.]

Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd

Plant pathology 49 (2000), S. 0

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ISSN: 1365-3059

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Micropropagated plants of 36 Musa genotypes with diverse genetic backgrounds, including 14 tetraploid plantain (TMPx) and banana (TMBx) hybrids, were evaluated for their response to banana streak badnavirus (BSV) infection under three environments from 1995 to 1997 in Nigeria. The characteristics evaluated were the natural incidence of BSV based on symptoms and virus indexing, relative concentration of BSV antigens in leaf tissues determined by ELISA, and some growth and yield descriptors. Virus occurrence and symptom expression, as well as the relative concentration of BSV antigens, fluctuated greatly between seasons during the cropping cycle, being high during the rainy season and low or negligible during the hot dry season. The natural incidence of plants with symptoms and BSV-infected plants varied between genotypes. Incidence of BSV on most International Institute of Tropical Agriculture (IITA) TMPx hybrids and three Fundación Hondureòa de Investigación Agrìcola (FHIA) hybrids was high in the three environments, with some variation. Most landraces and some FHIA or Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA) hybrids were not BSV-infected under either environment at Onne. However, a few expressed some foliar symptoms at Ibadan and indexed BSV positive. The relative concentration of BSV antigens in leaf samples was also high in most TMPx and some FHIA hybrids, but low in most landraces. While BSV infection had no significant effect on most growth characteristics, it had a highly variable effect on bunch weight loss among the genotypes. There was no relationship between the natural incidence of BSV, concentration of viral antigen and bunch weight loss among the 11 TMPx hybrids, three FHIA hybrids and three plantain landraces. Despite the high natural BSV incidence and the high relative antigen concentration in their leaf tissue, TMPx 548-9, TMPx 2637-49, TMPx 7002-1 and FHIA 21 suffered less than 15% bunch weight loss, and TMPx 548-4 and FHIA 22 suffered no loss. These results suggest that under the conditions specified in this study, these hybrids could be tentatively classified as ‘field tolerant’ to BSV.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3059.2000.00420.x

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Iron acquisition and virulence in Helicobacter pylori: a major role for FeoB, a high-affinity ferrous iron transporter (2000)

Velayudhan, Jyoti ; Hughes, Nicky J. ; McColm, Andrew A. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 37 (2000), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: The genome sequence of Helicobacter pylori suggests that this bacterium possesses several Fe acquisition systems, including both Fe2+- and Fe3+-citrate transporters. The role of these transporters was investigated by generating insertion mutants in feoB, tonB, fecA1 and fecDE. Fe transport in the feoB mutant was ≈ 10-fold lower than in the wild type (with 0.5 μM Fe), irrespective of whether Fe was supplied in the Fe2+ or Fe3+ form. In contrast, transport rates were unaffected by the other mutations. Complementation of the feoB mutation fully restored both Fe2+ and Fe3+ transport. The growth inhibition exhibited by the feoB mutant in Fe-deficient media was relieved by human holo-transferrin, holo-lactoferrin and Fe3+-dicitrate, but not by FeSO4. The feoB mutant had less cellular Fe and was more sensitive to growth inhibition by transition metals in comparison with the wild type. Biphasic kinetics of Fe2+ transport in the wild type suggested the presence of high- and low-affinity uptake systems. The high-affinity system (apparent Ks = 0.54 μM) is absent in the feoB mutant. Transport via FeoB is highly specific for Fe2+ and was inhibited by FCCP, DCCD and vanadate, indicating an active process energized by ATP. Ferrozine inhibition of Fe2+ and Fe3+ uptake implied the concerted involvement of both an Fe3+ reductase and FeoB in the uptake of Fe supplied as Fe3+. Taken together, the results are consistent with FeoB-mediated Fe2+ uptake being a major pathway for H. pylori Fe acquisition. feoB mutants were unable to colonize the gastric mucosa of mice, indicating that FeoB makes an important contribution to Fe acquisition by H. pylori in the low-pH, low-O2 environment of the stomach.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01987.x

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Completion of the hook–basal body complex of the Salmonella typhimurium flagellum is coupled to FlgM secretion and fliC transcription (2000)

Karlinsey, Joyce E. ; Tanaka, Shugo ; Bettenworth, Vera ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 37 (2000), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: The flhDC operon of Salmonella typhimurium is the master control operon required for the expression of the entire flagellar regulon. The flagellar master operon was placed under the tetracycline-inducible promoter PtetA using the T-POP transposon. Cells containing this construct are motile in the presence of tetracycline and non-motile without inducer present. No flagella were visible under the electron microscope when cells were grown without inducer. The class 1, class 2 and class 3 promoters of the flagellar regulon are temporally regulated. After addition of tetracycline, the class 1 flhDC operon was transcribed immediately. Transcription of flgM (which is transcribed from both class 2 and class 3 promoters) began 15 min after induction. At 20 min after induction, the class 2 fliA promoter became active and intracellular FliA protein levels increased; at 30 min after induction, the class 3 fliC promoter was activated. Induction of fliC gene expression coincides with the appearance of FlgM anti-sigma factor in the growth medium. This also coincides with the completion of hook–basal body structures. Rolling cells first appeared 35 min after induction, and excess hook protein (FlgE) was also found in the growth medium at this time. At 45 min after induction, nascent flagellar filaments became visible in electron micrographs and over 40% of the cells exhibited some swimming behaviour. Multiple flagella assemble and grow on individual cells after induction of the master operon. These results confirm that the flagellar regulatory hierarchy of S. typhimurium is temporally regulated after induction. Both FlgM secretion and class 3 gene expression occur upon completion of the hook–basal body structure.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02081.x

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New functions for the ancient globin family: bacterial responses to nitric oxide and nitrosative stress (2000)

Poole, Robert K. ; Hughes, Martin N.

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 36 (2000), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Globin-like oxygen-binding proteins occur in bacteria, yeasts and other fungi, and protozoa. The simplest contain protohaem as sole prosthetic group, but show considerable variation in their similarity to the classical animal globins and plant globins. Flavohaemoglobins comprise a haem domain homologous to classical globins and a ferredoxin-NADP+ reductase (FNR)-like domain that converts the globin into an NAD(P)H-oxidizing protein with diverse reductase activities. In Escherichia coli, the prototype flavohaemoglobin (Hmp) is clearly involved in responses to nitric oxide (NO) and nitrosative stress: (i) the structural gene hmp is upregulated by NO and nitrosating agents; (ii) purified Hmp binds NO avidly, but also converts it to nitrate (aerobically) or nitrous oxide (anaerobically); (iii) hmp mutants are hypersensitive to NO and nitrosative stresses. Here, we review recent advances in E. coli and the growing number of microbes in which globins are known, draw particular attention to the essential chemistry of NO and related reactive species and their interactions with globins, and suggest that microbial globins have additional functions unrelated to ‘NO’ stresses.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01889.x

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Fusidic acid-resistant EF-G perturbs the accumulation of ppGpp (2000)

Macvanin, Mirjana ; Johanson, Urban ; Ehrenberg, Måns ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 37 (2000), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Reductions in growth rate caused by fusidic acid-resistant EF-G mutants in Salmonella typhimurium correlate strongly with increased mean cell size. This is unusual because growth rate and cell size normally correlate positively. The global transcription regulator molecule ppGpp has a role in co-ordinating growth rate and division, and its basal level normally correlates inversely with cell size at division. We show that fusidic acid-resistant EF-G mutants have perturbed ppGpp basal levels during steady-state growth and perturbed induced levels during starvation. One mutation, fusA1, associated with the slowest growth rate and largest cell size, causes a reduction in the basal level of ppGpp to one-third of that found in the wild-type strain. Other fusA mutants with intermediate or wild-type growth rates and cell sizes have either normal or increased basal levels of ppGpp. There is an inverse relationship between the basal level of ppGpp in vivo and the degree to which translation dependent on mutant EF-G is inhibited by ppGpp in vitro. This enhanced interaction between mutant EF-G and ppGpp correlates with an increased KM for GTP. Our results suggest that mutant EF-G modulates the production of ppGpp by the RelA (PSI) pathway. In conclusion, fusidic acid-resistant EF-G mutations alter the level of ppGpp and break the normal relationship between growth rate and cell size at division. It would not be surprising if other phenotypes associated with these mutants, such as loss of virulence, were also related to perturbations in ppGpp levels effected through altered transcription patterns.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01967.x

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