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Germination of Penicillium paneum Conidia Is Regulated by 1-Octen-3-ol, a Volatile Self-Inhibitor. Gilma S. Chitarra, 2004.Penicillium paneum is an important contaminant of cereal grains which is able to grow at low temperature, low pH, high levels of carbon dioxide, and under acid conditions . P . paneum produces mycotoxins, which may be harmful to animals and humans . We found that conidia in dense suspensions showed poor germination, suggesting the presence of a self-inhibitor . A volatile compound(s) produced by these high-density conditions also inhibited mycelial growth of different species of fungi belonging to a variety of genera, suggesting a broad action range . The heat-stable compound was isolated by successive centrifugation of the supernatant obtained from spore suspensions with a density of 109 conidia ml–1 . By using static headspace analyses, two major peaks were distinguished, with the highest production of these metabolites after 22 h of incubation at 25°C and shaking at 140 rpm . Gas chromatography coupled with mass spectra analysis revealed the compounds to be 3-octanone and 1-octen-3-ol . Notably, only the latter compound appeared to block the germination process at different developmental stages of the conidia (swelling and germ tube formation) . In this study, 1-octen-3-ol influenced different developmental processes during the P . paneum life cycle, including induction of microcycle conidiation and inhibition of spore germination . Therefore, the compound can be considered a fungal hormone during fungal development . Three Modifications in the D and T Arms of tRNA Influence Translation in Escherichia coli and Expression of Virulence Genes in Shigella flexneri. Jaunius Urbonavi, 2002.The modified nucleosides 2'-O-methylguanosine, present at position 18 (Gm18), 5-methyluridine, present at position 54 (m5U54), and pseudouridine, present at position 55 (  55), are located in the D and T arms of tRNAs and are close in space in the three-dimensional (3D) structure of this molecule in the bacterium Escherichia coli . The formation of these modified nucleosides is catalyzed by the products of genes trmH (Gm18), trmA (m5U54), and truB (55) . The combination of trmH, trmA, and truB mutations resulting in lack of these three modifications reduced the growth rate, especially at high temperature . Moreover, the lack of three modified nucleotides in tRNA induced defects in the translation of certain codons, sensitivity to amino acid analog 3,4-dehydro-DL-proline, and an altered oxidation of some carbon compounds . The results are consistent with the suggestion that these modified nucleosides, two of which directly interact in the 3D structure of tRNA by forming a hydrogen bond between
55 and Gm18, stabilize the structure of the tRNA . Moreover, lack of
55 in tRNA of human pathogen Shigella flexneri leads to a reduced expression of several virulence-associated genes .
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