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Functional Expression of Sinorhizobium meliloti BetS, a High-Affinity Betaine Transporter, in Bradyrhizobium japonicum USDA110. Alexandre Boscari, 2004.Among the Rhizobiaceae, Bradyrhizobium japonicum strain USDA110 appears to be extremely salt sensitive, and the presence of glycine betaine cannot restore its growth in medium with an increased osmolarity (E . Boncompagni, M . Østerås, M . C . Poggi, and D . Le Rudulier, Appl . Environ . Microbiol . 65:2072-2077, 1999) . In order to improve the salt tolerance of B . japonicum, cells were transformed with the betS gene of Sinorhizobium meliloti . This gene encodes a major glycine betaine/proline betaine transporter from the betaine choline carnitine transporter family and is required for early osmotic adjustment . Whereas betaine transport was absent in the USDA110 strain, such transformation induced glycine betaine and proline betaine uptake in an osmotically dependent manner . Salt-treated transformed cells accumulated large amounts of glycine betaine, which was not catabolized . However, the accumulation was reversed through rapid efflux during osmotic downshock . An increased tolerance of transformant cells to a moderate NaCl concentration (80 mM) was also observed in the presence of glycine betaine or proline betaine, whereas the growth of the wild-type strain was totally abolished at 80 mM NaCl . Surprisingly, the deleterious effect due to a higher salt concentration (100 mM) could not be overcome by glycine betaine, despite a significant accumulation of this compound . Cell viability was not significantly affected in the presence of 100 mM NaCl, whereas 75% cell death occurred at 150 mM NaCl . The absence of a potential gene encoding Na+/H+ antiporters in B . japonicum could explain its very high Na+ sensitivity . Escherichia coli Endoribonucleases Involved in Cleavage of Bacteriophage T4 mRNAs. Yuichi Otsuka, 2003.The dmd mutant of bacteriophage T4 has a defect in growth because of rapid degradation of late-gene mRNAs, presumably caused by mutant-specific cleavages of RNA . Some such cleavages can occur in an allele-specific manner, depending on the translatability of RNA or the presence of a termination codon . Other cleavages are independent of translation . In the present study, by introducing plasmids carrying various soc alleles, we could detect cleavages of soc RNA in uninfected cells identical to those found in dmd mutant-infected cells . We isolated five Escherichia coli mutant strains in which the dmd mutant was able to grow . One of these strains completely suppressed the dmd mutant-specific cleavages of soc RNA . The loci of the E . coli mutations and the effects of mutations in known RNase-encoding genes suggested that an RNA cleavage activity causing the dmd mutant-specific mRNA degradation is attributable to a novel RNase . In addition, we present evidence that 5'-truncated soc RNA, a stable form in T4-infected cells regardless of the presence of a dmd mutation, is generated by RNase E .
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