Pigment production by Cryptococcus neoformans from para- and ortho-Diphenols: effect of the nitrogen source.
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Cryptococcus neoformans produced pigments when p-diphenols were substrates in a glucose-amino acid-salts medium. The best substrates were 2.5-dihydroxybenzoic acid and 2,5-dihydroxybenzenesulfonic acid. In contrast to the cellular pigment production from o-diphenols (hydroxyl groups in the 2,3- or 3,4-position of phenyl ring), the p-diphenols (1,4- or 2,5-positions for the hydroxyl groups) produced large amounts of soluble pigments that diffused into the medium. When an optimal source of nitrogen (glutamine, glycine, and asparagine) was used, 89% of the C. neoformans strains produced pigments from p-diphenols. In contrast, 0 to 67% of the strains produced pigments when a suboptimal nitrogen source (proline, ammonium sulfate, ornithine, and methionine) was used. When glutamine-glycine-asparagine was the nitrogen source, 100% of the C. neoformans strains produced pigments from o0diphenols, whereas 77 to 100% of the strains produced pigment when proline-ammonium sulfate-ornithine-methionine was the nitrogen source. Cryptococcus species other than C. neoformans and all tested Candida species failed to produce pigments from any of the substrates except when hydroquinone was used. A combination of glutamine-glycine-asparagine and 3,4-dihydroxyphenylalanine allowed differentiation of colonies of C. neoformans from C. albicans in 3 to 6 days. These data showed that pigment production from o- and p-diphenols served as an excellent biochemical test for the identification of C. neoformans. (+info)
Dynein, dynactin, and kinesin II's interaction with microtubules is regulated during bidirectional organelle transport.
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The microtubule motors, cytoplasmic dynein and kinesin II, drive pigmented organelles in opposite directions in Xenopus melanophores, but the mechanism by which these or other motors are regulated to control the direction of organelle transport has not been previously elucidated. We find that cytoplasmic dynein, dynactin, and kinesin II remain on pigment granules during aggregation and dispersion in melanophores, indicating that control of direction is not mediated by a cyclic association of motors with these organelles. However, the ability of dynein, dynactin, and kinesin II to bind to microtubules varies as a function of the state of aggregation or dispersion of the pigment in the cells from which these molecules are isolated. Dynein and dynactin bind to microtubules when obtained from cells with aggregated pigment, whereas kinesin II binds to microtubules when obtained from cells with dispersed pigment. Moreover, the microtubule binding activity of these motors/dynactin can be reversed in vitro by the kinases and phosphatase that regulate the direction of pigment granule transport in vivo. These findings suggest that phosphorylation controls the direction of pigment granule transport by altering the ability of dynein, dynactin, and kinesin II to interact with microtubules. (+info)
Vanadium interferes with siderophore-mediated iron uptake in Pseudomonas aeruginosa.
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Vanadium is a metal that under physiological conditions can exist in two oxidation states, V(IV) (vanadyl ion) and V(V) (vanadate ion). Here, it was demonstrated that both ions can form complexes with siderophores. Pseudomonas aeruginosa produces two siderophores under iron-limiting conditions, pyoverdine (PVD) and pyochelin (PCH). Vanadyl sulfate, at a concentration of 1-2 mM, strongly inhibited growth of P. aeruginosa PAO1, especially under conditions of severe iron limitation imposed by the presence of non-utilizable Fe(III) chelators. PVD-deficient mutants were more sensitive to vanadium than the wild-type, but addition of PVD did not stimulate their growth. Conversely, PCH-negative mutants were more resistant to vanadium than the wild-type strain. Both siderophores could bind and form complexes with vanadium after incubation with vanadyl sulfate (1:1, in the case of PVD; 2:1, in the case of PCH). Although only one complex with PVD, V(IV)-PVD, was found, both V(IV)- and V(V)-PCH were detected. V-PCH, but not V-PVD, caused strong growth reduction, resulting in a prolonged lag phase. Exposure of PAO1 cells to vanadium induced resistance to the superoxide-generating compound paraquat, and conversely, exposure to paraquat increased resistance to V(IV). Superoxide dismutase (SOD) activity of cells grown in the presence of V(IV) was augmented by a factor of two. Mutants deficient in the production of Fe-SOD (SodB) were particularly sensitive to vanadium, whilst sodA mutants deficient for Mn-SOD were only marginally affected. In conclusion, it is suggested that V-PCH catalyses a Fenton-type reaction whereby the toxic superoxide anion O(2)- is generated, and that vanadium compromises PVD utilization. (+info)
Pigment-protein architecture in the light-harvesting antenna complexes of purple bacteria: does the crystal structure reflect the native pigment-protein arrangement?
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Structural analysis of crystallized peripheral (LH2) and core antenna complexes (LH1) of purple bacteria has revealed circular aggregates of high rotational symmetry (C8, C9 and C16, respectively). Quantum-chemical calculations indicate that in particular the waterwheel-like arrangements of pigments should show characteristic structure-sensitive spectroscopic behavior in the near infrared absorption region. Laser-spectroscopic data obtained with non-crystallized, isolated LH2 of Rhodospirillum molischianum are in line with a highly symmetric (C8) circular aggregate, but deviations have been found for LH2 of Rhodobacter sphaeroides and Rhodopseudomonas acidophila. For both the latter, C-shaped incomplete circular aggregates (as seen only recently in electron micrographs of crystallized LH1-reaction center complexes) may be a suitable preliminary model. (+info)
A delta opioid receptor lacking the third cytoplasmic loop is generated by atypical mRNA processing in human malignomas.
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delta Opioid receptors were identified in human melanomas by RT-PCR and radioligand binding. In all tumors an additional PCR amplificate was detected in which 144 bp within the third exon were deleted. This fragment corresponded to the third cytoplasmic domain of the receptor protein. The short variant resulted from atypical mRNA processing. There were no common splice recognition sequences around the deleted fragment; instead its excision resembled the removal of a transposon. The deletion was not detected in normal human melanocytes nor in human or rat brain. However, it was present in a human neuroblastoma cell line (SH-SY5Y). Thus, it appears that the occurrence of the short delta opioid receptor is correlated to malignancy. (+info)
Mycobacterium kubicae sp. nov., a slowly growing, scotochromogenic Mycobacterium.
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A previously uncharacterized, slowly growing, scotochromogenic Mycobacterium species was detected by HPLC analysis of the cell-wall-bound mycolic acids. The mycolic acid pattern standard was shown to be a late-eluting, contiguous peak cluster occurring at approximately 8-9 min. The mycolic acid pattern was noted to be most similar in number of peaks and range of elution to that reported previously for Mycobacterium asiaticum. However, the relative distribution of peaks within the elution range demonstrated a pattern with prominent peaks that started to emerge later than the characteristic M. asiaticum pattern. Standard biochemical identification test results were similar to those of the photochromogenic species M. asiaticum. Comparative 16S rRNA gene sequence analysis confirmed the genetic uniqueness of the strains and demonstrated the unclassified mycobacteria to be in a unique, intermediate position between slow and rapid growers in the phylogenetic tree of Mycobacterium. The name Mycobacterium kubicae sp. nov. is proposed for this taxon. The type strain is CDC 941078T (= ATCC 700732T = CIP 106428T). (+info)
Prochlorococcus marinus Chisholm et al. 1992 subsp. pastoris subsp. nov. strain PCC 9511, the first axenic chlorophyll a2/b2-containing cyanobacterium (Oxyphotobacteria).
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The formal description of Prochlorococcus marinus Chisholm et al. 1992, 299 was based on the non-axenic nomenclatural type, strain CCMP 1375T. The purification and properties of the axenic strain PCC 9511, derived from the same primary culture (SARG) as the type species, are reported here. Prochlorococcus PCC 9511 differs from the latter in possessing horseshoe-shaped thylakoids, exhibiting a low chlorophyll b2 content and lacking phycoerythrin, but shares these phenotypic properties with Prochlorococcus strain CCMP 1378. This relationship was confirmed by 16S rRNA sequence analyses, which clearly demonstrated that the axenic isolate is not co-identic with the nomenclatural type. Strain PCC 9511 has a low mean DNA base composition (32 mol% G+C) and harbours the smallest genome of all known oxyphotobacteria (genome complexity 1.3 GDa = 2 Mbp). Urea and ammonia are the preferred sources of nitrogen for growth, whereas nitrate is not utilized. Several different organic phosphorus compounds efficiently replace phosphate in the culture medium, indicative of ecto-phosphohydrolase activity. In order to distinguish strain PCC 9511 from the nomenclatural type, a new subspecies is proposed, Prochlorococcus marinus Chisholm et al. 1992 subsp. pastoris subsp. nov. (+info)
Production of betacyanins by a cell suspension culture of table beet (Beta vulgaris L.).
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A cell suspension culture of table beet (Beta vulgaris L.) was established for efficient betacyanin production from violet callus induced from the hypocotyls of aseptic seedlings. This suspension culture produced large amounts of betacyanins. The betacyanin content increased with increasing cell growth during the log phase. Reducing the total nitrogen concentration (30 mM) and modifying the ratio of ammonium to nitrate (1:14) resulted in an increased betacyanin content. Supplementation of Fe2+ to the LS medium also promoted betacyanin production. The maximal betacyanin yield was achieved with a 2 mM Fe2+ concentration. Combining these conditions, we established a revised LS medium to improve betacyanin productivity (250 mg/l for a 14-day culture). (+info)