YgdE is the 2'-O-ribose methyltransferase RlmM specific for nucleotide C2498 in bacterial 23S rRNA

The rRNAs of Escherichia coli contain four 2'- O- methylated nucleotides. Similar to other bacterial species and in contrast with Archaea and Eukaryota, the E. coli rRNA modifications are catalysed by specific methyltransferases that find their nucleotide targets without being guided by small complementary RNAs. We show here that the ygdE gene encodes the methyltransferase that catalyses 2'- O- methylation at nucleotide C2498 in the peptidyl transferase loop of E. coli 23S rRNA. Analyses of rRNAs using MALDI mass spectrometry showed that inactivation of the ygdE gene leads to loss of methylation at nucleotide C2498. The loss of ygdE function causes a slight reduction in bacterial fitness. Methylation at C2498 was restored by complementing the knock-out strain with a recombinant copy of ygdE . The recombinant YgdE methyltransferase modifies C2498 in naked 23S rRNA, but not in assembled 50S subunits or ribosomes. Nucleotide C2498 is situated within a highly conserved and heavily modified rRNA sequence, and YgdE's activity is influenced by other modification enzymes that target this region. Phylogenetically, YgdE is placed in the cluster of orthologous groups COG2933 together with S -adenosylmethionine-dependent, Rossmann-fold methyltransferases such as the archaeal and eukaryotic RNA-guided fibrillarins. The ygdE gene has been redesignated rlmM for r RNA l arge subunit m ethyltransferase M .     

Physaria fendleri and Ricinus communis lecithin:cholesterol acyltransferase-like phospholipases selectively cleave hydroxy acyl chains from phosphatidylcholine

Production of hydroxy fatty acids (HFAs) in transgenic crops represents a promising strategy to meet our demands for specialized plant oils with industrial applications. The expression of Ricinus communis (castor) OLEATE 12-HYDROXYLASE (RcFAH12) in Arabidopsis has resulted in only limited accumulation of HFAs in seeds, which probably results from inefficient transfer of HFAs from their site of synthesis (phosphatidylcholine; PC) to triacylglycerol (TAG), especially at the sn-1/3 positions of TAG. Phospholipase As (PLAs) may be directly involved in the liberation of HFAs from PC, but the functions of their over-expression in HFA accumulation and distribution at TAG in transgenic plants have not been well studied. In this work, the functions of lecithin:cholesterol acyltransferase-like PLAs (LCAT-PLAs) in HFA biosynthesis were characterized. The LCAT-PLAs were shown to exhibit homology to LCAT and mammalian lysosomal PLA₂, and to contain a conserved and functional Ser/His/Asp catalytic triad. In vitro assays revealed that LCAT-PLAs from the HFA-accumulating plant species Physaria fendleri (PfLCAT-PLA) and castor (RcLCAT-PLA) could cleave acyl chains at both the sn-1 and sn-2 positions of PC, and displayed substrate selectivity towards sn-2-ricinoleoyl-PC over sn-2-oleoyl-PC. Furthermore, co-expression of RcFAH12 with PfLCAT-PLA or RcLCAT-PLA, but not Arabidopsis AtLCAT-PLA, resulted in increased occupation of HFA at the sn-1/3 positions of TAG as well as small but insignificant increases in HFA levels in Arabidopsis seeds compared with RcFAH12 expression alone. Therefore, PfLCAT-PLA and RcLCAT-PLA may contribute to HFA turnover on PC, and represent potential candidates for engineering the production of unusual fatty acids in crops.     

A new electrogenic step in the ubiquinol: Cytochrome c2 oxidoreductase complex of Rhodopseudomonas sphaeroides

Myxothiazol, an inhibitor of the ubiquinol oxidase site of the ubiquinol: cytochrome c₂ oxidoreductase complex, has been shown in the present work to inhibit a part of the electrogenic process indicated by phase III of the carotenoid change, in addition to the part of the change inhibited by antimycin. This finding shows that there is an antimycin-insensitive, but myxothiazol-sensitive portion of the slow phase, which indicates the existence of an electrogenic event within the ubiquinol: cytochrome c₂ oxidoreductase complex, in addition to that linked to oxidation of cytochrome b-561 which has been previously characterized. Redox titrations show that the appearance of the new electrogenic step is correlated with the amount of cytochrome b-561 available in the oxidized form before the flash. The rate of the antimycin-insensitive and myxothiazol-sensitive portion of the carotenoid change correlates well with the rate of reduction of cytochrome b-561. No carotenoid change associated with reduction of cytochrome b-566 was seen. These findings suggest that the newly identified electrogenic process is linked to electron transfer between cytochrome b-566 and b-561. Calculations of the contribution of this new electrogenic step to the total electrogenic event within the complex show that electrons passing from cytochrome b-566 to cytochrome b-561 pass about 35–50% of the distance across the whole membrane.     

The structure of the lipopolysaccharide core region of Citrobacter 027

The structure of Citrobacter 027 lipopolysaccharide core has been established using sugar and methylation analyses and 1H-NMR spectroscopy, and was shown to be identical to the core described recently in PCM 1487 strain which represents a separate serotype in Citrobacter genus.     

Effect of red light on ribulose 1,5-bisphosphate carboxylase activity in pea leaves

The ribulose 1,5-bisphosphate activity and its relative content in pea (Pisum sativum L., cv. Bordi) seedlings grown either under white or red light were investigated. Plants grown under red light had a lower ribulose 1,5- bisphosphate carboxylase (RuBPCO) activity as compared to plants grown under white light, if expressed on a fresh mass. These activities were very similar under both lights, as calculated on protein basis, although the relative content of RuBPCO was higher in the red one. The activity of RuBPCO under red light corresponds to the lower rate of net photosynthesis. The results are discussed in respect to possible presence of RuBPCO inhibitor in pea plants growth under red light.     

Trace metals and micronutrients in bone tissues of the red fox <Emphasis Type="Italic">Vulpes vulpes</Emphasis> (L., 1758)

In this study we determined the levels of trace elements (zinc, copper, lead, cadmium and mercury) in three layers of bones of the hip joint (cartilage, compact bone and spongy bone) of 30 red foxes (Vulpes vulpes) from north-western Poland. Concentrations of Cu, Zn, Pb and Cd were determined by atomic absorption spectrophotometry (ICP-AES) in inductively coupled argon plasma using a Perkin-Elmer Optima 2000 DV. Determination of Hg concentration was performed by atomic absorption spectroscopy. In cartilage, compact bone and spongy bone samples from the red fox, median concentrations of the metals studied could be arranged in the following descending series: Zn > Cu > Pb > Cd > Hg, the values ranging from 142 to 0.002 mg/kg dw. There was a significant difference in Cu concentrations, among all the materials analyzed, with much more Cu found in spongy bone than in compact bone. Significant differences were also noted in the case of Hg concentrations in cartilage with compact bone and the spongy bone, and between concentrations of this metal in compact bone and spongy bone. In males, the concentration of Hg in spongy bone was greater than in females. Younger foxes had a higher concentration of this metal in cartilage than adults. The strongest synergistic relationships were observed in spongy bone between the Zn and Cu, Zn and Cd, as well as between Cu and Cd. Statistically significant antagonistic relationships were detected between zinc and lead in compact bone. In addition to monitoring studies conducted on the abiotic environment, an urgent need exists for long-term monitoring of concentrations of heavy metals with long-term effects on living organisms. An important addition is provided by biomonitoring studies on domesticated and free-living mammals, including Canidae.     

The genus Aerotegmina (Orthoptera, Tettigoniidae, Hexacentrinae): chromosomes, morphological relations, phylogeographical patterns and description of a new species

The genus Aerotegmina Hemp is common on East African mountains. Two species are known and a third, A. taitensis n. sp., is described in this paper. A. kilimandjarica Hemp is widespread while A. shengenae Hemp is endemic to the South Pare Mountains and A. taitensis n. sp. is known only from the Taita Hills. Morphologically, and from their song, A. shengenae and A. taitensis n. sp. are closely related. In chromosome number A. kilimandjarica (2n?=?33) differs clearly from A. shengenae (2n?=?27). Data presented on other flightless Orthoptera suggest that the South Pare Mountains and the Taita Hills, both belonging to the geologically old mountain chain of the Eastern Arc, show a faunistic similarity not shared by any other mountain range in the area. The mechanisms that led to this phylogeographic pattern in flightless Orthoptera in the Eastern Arc Mountains of northern Tanzania and southern Kenya and the inland volcanoes are discussed. A key to the three Aerotegmina species is presented, as well as bioacoustical data of all species compared to the phaneropterine species Euryastes jagoi.     

A comparison of interfertility and in vitro DNA-DNA reassociation as criteria for speciation in the genus Kluyveromyces

Hybridization studies based on the use of the prototrophic selection technique were undertaken to compare interfertility and DNA-DNA reassociation as criteria for speciation purposes in the yeast genus Kluyveromyces. Degrees of DNA-DNA reassociation > 70% between strains as reported in the literature, were found to correlate with high recombination frequencies. Degrees of DNA-DNA reassociation < 20% between strains did however, not invariably coincide with the absence of interfertility between strains. If interfertility is accepted as criterion for conspecificity, the hitherto reported low degrees ( < 20%) of DNA-DNA reassociation in Kluyveromyces cannot confidently be employed for speciation purposes.