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Transcriptional and Posttranscriptional Control of Cable Pilus Gene Expression in Burkholderia cenocepacia. Mladen Tomich, 2004.Burkholderia cenocepacia is an important member of the Burkholderia cepacia complex, a group of closely related bacteria that inhabits a wide variety of environmental niches in nature and that also colonizes the lungs of compromised humans . Certain strains ofB . cenocepacia express peritrichous adherence organelles knownas cable pili, thought to be important in the colonization ofthe lower respiratory tract . The genetic locus required forcable pilus biogenesis is comprised of at least five genes,designated cblB, cblA, cblC, cblD, and cblS . In this study a transcriptional analysis of cbl gene expression was undertaken. The principal promoter, located upstream of the cbl locus, was identified and characterized . By using lacZ transcriptional fusions, the effects of multiple environmental cues on cbl gene expression were examined . High osmolarity, temperature of 37°C, acidic pH, and low iron bioavailability were found to inducecbl gene expression . Northern hybridization analysis of thecbl locus identified a single, stable transcript correspondingto cblA, encoding the major pilin subunit . Transcriptional fusionstudies combined with reverse transcription-PCR analysis indicatedthat the stable cblA transcript is the product of an mRNA processing event . This event may ensure high levels of expression of themajor pilin, relative to other components of the assembly pathway.Our findings lend further insight into the control of cablepilus biogenesis in B . cenocepacia and provide evidence for regulation of cbl gene expression on both the transcriptional and posttranscriptional levels. Genomic Sequence of C1, the First Streptococcal Phage. Daniel Nelson, 2003.C1, a lytic bacteriophage infecting group C streptococci, is one of the earliest-isolated phages, and the method of bacterial classification known as phage typing was defined by using this bacteriophage . We present for the first time a detailed analysis of this phage by use of electron microscopy, protein profiling, and complete nucleotide sequencing . This virus belongs to the Podoviridae family of phages, all of which are characterized by short, noncontractile tails . The C1 genome consists of a linear double-stranded DNA molecule of 16,687 nucleotides with 143-bp inverted terminal repeats . We have assigned functions to 9 of 20 putative open reading frames based on experimental substantiation or bioinformatic analysis . Their products include DNA polymerase, holin, lysin, major capsid, head-tail connector, neck appendage, and major tail proteins . Additionally, we found one intron belonging to the HNH endonuclease family interrupting the apparent lysin gene, suggesting a potential splicing event yielding a functional lytic enzyme . Examination of the C1 DNA polymerase suggests that this phage utilizes a protein-primed mechanism of replication, which is prominent in the  29-like
members of Podoviridae . Consistent with this evidence, we
experimentally determined that terminal proteins are covalently
attached to both 5' termini, despite the fact that no homology to
known terminal proteins could be elucidated in any of our open
reading frames . Likewise, comparative genomics revealed no close
evolutionary matches, suggesting that the C1 bacteriophage
is a unique member of the Podoviridae .
Efavirenz Therapy in Rhesus Macaques Infected with a Chimera of Simian Immunodeficiency Virus Containing Reverse Transcriptase from Human Immunodeficiency Virus Type 1. Michael J. Hofman, 2004.The specificity of nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) for the RT of human immunodeficiency virus type 1 (HIV-1) has prevented the use of simian immunodeficiency virus (SIV) in the study of NNRTIs and NNRTI-based highly active antiretroviral therapy . However, a SIV-HIV-1 chimera (RT-SHIV), in which the RT from SIVmac239 was replaced with the RT-encoding region from HIV-1, is susceptible to NNRTIs and is infectious to rhesus macaques . We have evaluated the antiviral activity of efavirenz against RT-SHIV and the emergence of efavirenz-resistant mutants in vitro and in vivo . RT-SHIV was susceptible to efavirenz with a mean effective concentration of 5.9 ± 4.5 nM, and RT-SHIV variants selected with efavirenz in cell culture displayed 600-fold-reduced susceptibility . The efavirenz-resistant mutants of RT-SHIV had mutations in RT similar to those of HIV-1 variants that were selected under similar conditions . Efavirenz monotherapy of RT-SHIV-infected macaques produced a 1.82-log-unit decrease in plasma viral-RNA levels after 1 week . The virus load rebounded within 3 weeks in one treated animal and more slowly in a second animal . Virus isolated from these two animals contained the K103N and Y188C or Y188L mutations . The RT-SHIV-rhesus macaque model may prove useful for studies of antiretroviral drug combinations that include efavirenz . Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation. Elisa Varela, 2003.
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