The endoribonucleolytic N-terminal half of Escherichia coli RNase E is evolutionarily conserved in Synechocystis sp. and other bacteria but not the C-terminal half, which is sufficient for degradosome assembly

Escherichia coli RNase E, an essential single-stranded specific endoribonuclease, is required for both ribosomal RNA processing and the rapid degradation of mRNA. The availability of the complete sequences of a number of bacterial genomes prompted us to assess the evolutionarily conservation of bacterial RNase E. We show here that the sequence of the N-terminal endoribonucleolytic domain of RNase E is evolutionarily conserved in Synechocystis sp. and other bacteria. Furthermore, we demonstrate that the Synechocystis sp. homologue binds RNase E substrates and cleaves them at the same position as the E. coli enzyme. Taken together these results suggest that RNase E-mediated mechanisms of RNA decay are not confined to E. coli and its close relatives. We also show that the C-terminal half of E. coli RNase E is both sufficient and necessary for its physical interaction with the 3'-5' exoribonuclease polynucleotide phosphorylase, the RhlB helicase, and the glycolytic enzyme enolase, which are components of a "degradosome" complex. Interestingly, however, the sequence of the C-terminal half of E. coli RNase E is not highly conserved evolutionarily, suggesting diversity of RNase E interactions with other RNA decay components in different organisms. This notion is supported by our finding that the Synechocystis sp. RNase E homologue does not function as a platform for assembly of E. coli degradosome components

The final cut: The importance of tRNA 3′-processing

To generate functional tRNA molecules, precursor RNAs must undergo several processing steps. While the enzyme that generates the mature tRNA 5′-end, RNase P, has been thoroughly investigated, the 3′-processing activity is, despite its importance, less understood. While nothing is known about tRNA 3′-processing in archaea, the phenomenon has been analysed in detail in bacteria and is known to be a multistep process involving several enzymes, including both exo- and endonucleases. tRNA 3′-end processing in the eukaryotic nucleus seems to be either exonucleolytic or endonucleolytic, depending on the organism analysed, whereas in organelles, 3′-end maturation occurs via a single endonucleolytic cut. An interesting feature of organellar tRNA 3′-processing is the occurrence of overlapping tRNA genes in metazoan mitochondria, which presents a unique challenge for the mitochondrial tRNA maturation enzymes, since it requires not only the removal but also the addition of nucleotides by an editing reaction

Alguns grupos de microrganismos em manteigas vendidas no município de São Paulo Microorganism groups found in butter sold in the City of S. Paulo, Brazil

Foram colhidas 105 amostras de manteiga de 5 marcas diferentes vendidas em supermercados da cidade de São Paulo (Brasil) com a finalidade de verificar as condições microbiológicas de manteigas e compará-las com os padrões recomendados. Semanalmente foi colhida uma amostra de cada marca, durante 21 semanas. A partir da parte aquosa de cada amostra, foram realizadas as contagens de bactérias mesófilas e psicrófilas (em ágar padrão e ágar gelisato), coliformes, proteolíticas e de bolores e leveduras e os resultados comparados com alguns parâmetros propostos por vários pesquisadores. Os valores obtidos nas contagens dos vários grupos de microrganismos estudados, em muitos casos podem ser considerados altos, os quais podem ser resultado do processamento e/ou conservação, realizados em condições não satisfatórias.<br>One hundred and five samples of five different brands of butter in the supermarkets of the City of S. Paulo, Brazil were brought in for testing every week for 21 weeks. From the aqueous phase, counts were made for mesophilic and psichrophilic (using the standard plate count, agar and gelysate agar), coliform, proteolytic, and lipolytic bacteria, as well as for yeasts and molds. Results were compared with parameters proposed by several researchers. In many cases, the count values can be considered high, but these high counts may be due to inadequate processing and/or inadequate storage