|
|
|
|
|
|
Ribosomal Protein S1 Specifically Binds to the 5' Untranslated Region of the Pseudomonas aeruginosa Stationary-Phase Sigma Factor rpoS mRNA in the Logarithmic Phase of Growth. Milica , 2004.The rpoS gene encodes the stationary-phase sigma factor (RpoS or  s),
which was identified in several gram-negative bacteria as a central
regulator controlling the expression of genes involved in cell
survival in response to cessation of growth (stationary phase) and
providing cross-protection against various stresses . In
Pseudomonas aeruginosa, the levels of
s
increase dramatically at the onset of the stationary phase and are
regulated at the transcriptional and posttranscriptional levels . The
P . aeruginosa rpoS gene is transcribed as a monocistronic
rpoS mRNA transcript comprised of an unusually long 373-bp 5'
untranslated region (5' UTR) . In this study, the 5' UTR and total
protein extracts from P . aeruginosa logarithmic and stationary
phases of growth were used in order to investigate the protein-RNA
interactions that may modulate the translational process . It was
observed that a 69-kDa protein, which corresponded to ribosomal
protein S1, preferentially binds the 5' UTR of the rpoS mRNA
in the logarithmic phase and not in the stationary phase . This is the
first report of a protein-rpoS mRNA 5' UTR interaction in P .
aeruginosa, and the possible involvement of protein S1 in translation
regulation of rpoS is discussed .
Potential New Anti-Human Immunodeficiency Virus Type 1 Compounds Depress Virus Replication in Cultured Human Macrophages. Gary D. Ewart, 2004.We report that the amiloride analogues 5-(N,N-hexamethylene)amiloride and 5-(N,N-dimethyl)amiloride inhibit, at micromolar concentrations, the replication of human immunodeficiency virus type 1 (HIV-1) in cultured human blood monocyte-derived macrophages . These compounds also inhibit the in vitro activities of the HIV-1 Vpu protein and might represent lead compounds for a new class of anti-HIV-1 drugs . Isolation, Characterization, and In Situ Detection of a Novel Chemolithoautotrophic Sulfur-Oxidizing Bacterium in Wastewater Biofilms Growing under Microaerophilic Conditions. Tsukasa Ito, 2004.We successfully isolated a novel aerobic chemolithotrophic sulfur-oxidizing bacterium, designated strain SO07, from wastewater biofilms growing under microaerophilic conditions . For isolation, the use of elemental sulfur (S0), which is the most abundant sulfur pool in the wastewater biofilms, as the electron donor was an effective measure to establish an enrichment culture of strain SO07 and further isolation . 16S rRNA gene sequence analysis revealed that newly isolated strain SO07 was affiliated with members of the genus Halothiobacillus, but it was only distantly related to previously isolated species (89% identity) . Strain SO07 oxidized elemental sulfur, thiosulfate, and sulfide to sulfate under oxic conditions . Strain SO07 could not grow on nitrate . Organic carbons, including acetate, propionate, and formate, could not serve as carbon and energy sources . Unlike other aerobic sulfur-oxidizing bacteria, this bacterium was sensitive to NaCl; growth in medium containing more than 150 mM was negligible . In situ hybridization combined with confocal laser scanning microscopy revealed that a number of rod-shaped cells hybridized with a probe specific for strain SO07 were mainly present in the oxic biofilm strata (ca . 0 to 100 µm) and that they often coexisted with sulfate-reducing bacteria in this zone . These results demonstrated that strain SO07 was one of the important sulfur-oxidizing populations involved in the sulfur cycle occurring in the wastewater biofilm and was primarily responsible for the oxidation of H2S and S0 to SO42– under oxic conditions . Plasmid-Encoded Autolysin in Bacillus anthracis: Modular Structure and Catalytic Properties. Stéphane Mesnage, 2002.A Bacillus anthracis virulence plasmid-encoded peptidoglycan hydrolase (AmiA) with sequence similarity to N-acetylmuramoyl-L-alanine amidases hydrolyzes peptidoglycan independently of cell wall binding . Residues H341, E355, H415, and E486 are absolutely required for catalysis . Many AmiA paralogs are fused to different sorting signals, suggesting that these modular proteins result from domain shuffling . Control of Butanol Formation in Clostridium acetobutylicum by Transcriptional Activation. Kai Thormann, 2002.The sol operon of Clostridium acetobutylicum is the essential transcription unit for formation of the solvents butanol and acetone . The recent proposal that transcriptional regulation of this operon is controlled by the repressor Orf5/SolR (R . V . Nair, E . M . Green, D . E . Watson, G . N . Bennett, and E . T . Papoutsakis, J . Bacteriol . 181:319-330, 1999) was found to be incorrect . Instead, regulation depends on activation, most probably by the multivalent transcription factor Spo0A . The operon is transcribed from a single promoter . A second signal identified in primer extension studies results from mRNA processing and can be observed only in the natural host, not in a heterologous host . The first structural gene in the operon (adhE, encoding a bifunctional butyraldehyde/butanol dehydrogenase) is translated into two different proteins, the mature AdhE enzyme and the separate butanol dehydrogenase domain . The promoter of the sol operon is preceded by three imperfect repeats and a putative Spo0A-binding motif, which partially overlaps with repeat 3 (R3) . Reporter gene analysis performed with the lacZ gene of Thermoanaerobacterium thermosulfurigenes and targeted mutations of the regulatory region revealed that the putative Spo0A-binding motif, R3, and R1 are essential for control . The data obtained also indicate that an additional activator protein is involved . Transcription of the Salmonella Invasion Gene Activator, hilA, Requires HilD Activation in the Absence of Negative Regulators. Jennifer D. Boddicker, 2003.Salmonella enterica serovar Typhimurium causes human gastroenteritis and a systemic typhoid-like infection in mice . Infection is initiated by entry of the bacteria into intestinal epithelial cells and is mediated by a type III secretion system that is encoded by genes in Salmonella pathogenicity island 1 . The expression of invasion genes is tightly regulated by environmental conditions such as oxygen and osmolarity, as well as by many bacterial factors . The hilA gene encodes an OmpR/ToxR family transcriptional regulator that activates the expression of invasion genes in response to both environmental and genetic regulatory factors . HilD is an AraC/XylS regulator that has been postulated to act as a derepressor of hilA expression that promotes transcription by interfering with repressor binding at the hilA promoter . Our research group has identified four genes (hilE, hha, pag, and ams) that negatively affect hilA transcription . Since the postulated function of HilD at the hilA promoter is to counteract the effects of repressors, we examined this model by measuring hilA::Tn5lacZY expression in strains containing negative regulator mutations in the presence or absence of functional HilD . Single negative regulator mutations caused significant derepression of hilA expression, and two or more negative regulator mutations led to very high level expression of hilA . However, in all strains tested, the absence of hilD resulted in low-level expression of hilA, suggesting that HilD is required for activation of hilA expression, whether or not negative regulators are present . We also observed that deletion of the HilD binding sites in the chromosomal hilA promoter severely decreased hilA expression . In addition, we found that a single point mutation at leucine 289 in the C-terminal domain of the  subunit of RNA polymerase leads to very low levels of hilA::Tn5lacZY expression, suggesting that HilD activates transcription of hilA by contacting and recruiting RNA polymerase to the hilA promoter .
The Streptomyces coelicolor Developmental Transcription Factor  BldN Is Synthesized as a Proprotein.Maureen J. Bibb, 2003.bldN is one of a set of genes required for the formation of specialized, spore-bearing aerial hyphae during differentiation in the mycelial bacterium Streptomyces coelicolor . Previous analysis (M . J . Bibb et al., J . Bacteriol . 182:4606-4616, 2000) showed that bldN encodes a member of the extracytoplasmic function subfamily of RNA polymerase factors and that translation from the most strongly predicted start codon (GTG1) would give rise to a
factor having an unusual N-terminal extension of ca . 86 residues . Here, by using a combination of site-directed mutagenesis and immunoblot analysis, we provide evidence that all bldN translation arises from initiation at GTG1 and that the primary translation product is a proprotein (pro-BldN) that is proteolytically processed to a mature species (BldN) by removal of most of the unusual N-terminal extension . A time course taken during differentiation of the wild type on solid medium showed early production of pro-BldN and the subsequent appearance of mature
BldN, which was concomitant with aerial mycelium formation and the disappearance of pro-BldN . Two genes encoding members of a family of metalloproteases that are involved in the regulated proteolytic processing of transcription factors in other organisms were identified in the S . coelicolor genome, but their disruption did not affect differentiation or pro-BldN processing .
PCR-Restriction Fragment Length Polymorphism Method for Detection of Cyclospora cayetanensis in Environmental Waters without Microscopic Confirmation. Joan M. Shields, 2003.We developed an alternative nested-PCR-restriction fragment length polymorphism (RFLP) protocol for the detection of Cyclospora cayetanensis in environmental samples that obviates the need for microscopic examination . The RFLP method, with the restriction enzyme AluI, differentiates the amplified target sequence from C . cayetanensis from those that may cross-react . This new protocol was used to reexamine a subset (121 of 180) of surface water samples . Samples previously positive when the CYCF3E and CYCR4B primers () and RFLP with MnlI () were used were also PCR positive with the new primers; however, they were RFLP negative . We verified, by sequencing these amplicons, that while two were most likely other Cyclospora species, they were not C . cayetanensis . We can detect as few as one oocyst seeded into an autoclaved pellet flocculated from 10 liters of surface water . This new protocol should be of great use for environmental microbiologists and public health laboratories .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
