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Displacements of Prohead Protease Genes in the Late Operons of Double-Stranded-DNA Bacteriophages. Jing Liu, 2004.Most of the known prohead maturation proteases in double-stranded-DNA bacteriophages are shown, by computational methods, to fall into two evolutionarily independent clans of serine proteases, herpesvirus assemblin-like and ClpP-like . Phylogenetic analysis suggests that these two types of phage prohead protease genes displaced each other multiple times while preserving their exact location within the late operons of the phage genomes . High Prevalence of the ermB Gene among Erythromycin-Resistant Streptococcus pneumoniae Isolates in Germany during the Winter of 2000-2001 and In Vitro Activity of Telithromycin. Michael Kresken, 2004.Of 595 isolates of Streptococcus pneumoniae from outpatients with respiratory tract infections, collected from 17 microbiology laboratories, 14.1% were resistant to erythromycin . Eighty-three erythromycin-resistant isolates were genetically analyzed, 83.1% of which harbored the ermB gene . Only four isolates (4.8%) harbored the mefA gene . Telithromycin exhibited potent activity against all isolates . Light Dependence of [3H]Leucine Incorporation in the Oligotrophic North Pacific Ocean. Matthew J. Church, 2004.The influence of irradiance on bacterial incorporation of [3H]leucine was evaluated at Station ALOHA in the oligotrophic North Pacific subtropical gyre . Six experiments were conducted on three cruises to Station ALOHA to examine how [3H]leucine incorporation varied as a function of irradiance . Two experiments were also conducted to assess the photoautotrophic response to irradiance (based on photosynthetic uptake of [14C]bicarbonate) in both the upper and lower photic zones . Rates of [3H]leucine incorporation responded to irradiance in a photosynthesis-like manner, increasing sharply at low light and then saturating and sometimes declining with increasing light intensity . The influence of irradiance on bacterial growth was evaluated in both the well-lit (5 to 25 m) and dimly lit regions of the upper ocean (75 to 100 m) to determine whether the bacterial response to irradiance differed along the depth-dependent light gradient of the photic zone . [3H]leucine incorporation rates were analyzed with a photosynthesis-irradiance model for a quantitative description of the relationships between [3H]leucine incorporation and irradiance . Maximum rates of [3H]leucine incorporation in the upper photic zone increased 48 to 92% relative to those of dark-incubated samples, with [3H]leucine incorporation saturating at light intensities between 58 and 363 µmol of quanta m–2 s–1 . Rates of [3H]leucine incorporation in the deep photic zone were photostimulated 53 to 114% and were susceptible to photoinhibition, with rates declining at light intensities of >100 µmol of quanta m–2 s–1 . The results of these experiments revealed that sunlight directly influences bacterial growth in this open-ocean ecosystem . Requirement of flhA for Swarming Differentiation, Flagellin Export, and Secretion of Virulence-Associated Proteins in Bacillus thuringiensis. Emilia Ghelardi, 2002.Bacillus thuringiensis is being used worldwide as a biopesticide, although increasing evidence suggests that it is emerging as an opportunistic human pathogen . While phospholipases, hemolysins, and enterotoxins are claimed to be responsible for B . thuringiensis virulence, there is no direct evidence to indicate that the flagellum-driven motility plays a role in parasite-host interactions . This report describes the characterization of a mini-Tn10 mutant of B . thuringiensis that is defective in flagellum filament assembly and in swimming and swarming motility as well as in the production of hemolysin BL and phosphatidylcholine-preferring phospholipase C . The mutant strain was determined to carry the transposon insertion in flhA, a flagellar class II gene encoding a protein of the flagellar type III export apparatus . Interestingly, the flhA mutant of B . thuringiensis synthesized flagellin but was impaired in flagellin export . Moreover, a protein similar to the anti-sigma factor FlgM that acts in regulating flagellar class III gene transcription was not detectable in B . thuringiensis, thus suggesting that the flagellar gene expression hierarchy of B . thuringiensis differs from that described for Bacillus subtilis . The flhA mutant of B . thuringiensis was also defective in the secretion of hemolysin BL and phosphatidylcholine-preferring phospholipase C, although both of these virulence factors were synthesized by the mutant . Since complementation of the mutant with a plasmid harboring the flhA gene restored swimming and swarming motility as well as secretion of toxins, the overall results indicate that motility and virulence in B . thuringiensis may be coordinately regulated by flhA, which appears to play a crucial role in the export of flagellar as well as nonflagellar proteins . PAV1, the First Virus-Like Particle Isolated from a Hyperthermophilic Euryarchaeote, "Pyrococcus abyssi". C. Geslin, 2003.We describe the first virus-like particle of a hyperthermophilic euryarchaeote which was discovered in a strain of "Pyrococcus abyssi" previously characterized in our laboratory . This particle, named PAV1, is lemon-shaped (120 nm x 80 nm), with a short tail terminated by fibers, and resembles the virus SSV1, the type member of the Fuselloviridae, isolated from Sulfolobus shibatae . Sensitivity of the virus-like particle to organic solvents and detergents suggested that the envelope of PAV1 may contain lipids in addition to proteins . It contains a double-stranded circular DNA of 18 kb which is also present in high copy number in a free form in the host cytoplasm . No integrated form of the PAV1 genome could be detected in the host chromosome . Under standard growth conditions, the host cells continuously release PAV1 particles into the culture supernatant without spontaneous lysis, with a maximum reached in the late stationary phase . UV, gamma irradiation, treatment with mitomycin C, and various physiological stresses had no effect on PAV1 production . Screening of a large number of Thermococcales isolates did not permit to find a sensitive host . These results suggest that PAV1 persists in the host strain in a stable carrier state rather than a prophage . Transcription of the Toxin Genes Present within the Staphylococcal Phage  Sa3ms Is Intimately Linked with the Phage's Life Cycle.Paul Sumby, 2003. Sa3ms, a lysogenic bacteriophage encoding the staphylococcal enterotoxins SEA, SEG, and SEK and the fibrinolytic enzyme staphylokinase (Sak), was identified in the unannotated genome sequence of the hypervirulent community-acquired Staphylococcus aureus strain 476 . We found that mitomycin C induction of
Sa3ms led to increased transcription of all four virulence factors . The increase in sea and sak transcription was a result of read-through transcription from upstream latent phage promoters and an increase in phage copy number . The majority of the seg2 and sek2 transcripts were shown to initiate from the upstream phage cI promoter and hence were regulated by factors influencing cI transcription . The lysogeny module of
Sa3ms was shown to have some
 -like features with divergent cI and cro genes . Band shift assays were used to identify binding sites for both CI and Cro within the region between these genes, suggesting a mechanism of control for the
Sa3ms lytic-lysogenic switch . Our findings suggest that the production of phage-encoded virulence factors in S . aureus may be regulated by processes that govern lysogeny .
Activation of the Rcs Signal Transduction System Is Responsible for the Thermosensitive Growth Defect of an Escherichia coli Mutant Lacking Phosphatidylglycerol and Cardiolipin. Yasuhiro Shiba, 2004.The lethal effect of an Escherichia coli pgsA null mutation, which causes a complete lack of the major acidic phospholipids, phosphatidylglycerol and cardiolipin, is alleviated by a lack of the major outer membrane lipoprotein encoded by the lpp gene, but an lpp pgsA strain shows a thermosensitive growth defect . Using transposon mutagenesis, we found that this thermosensitivity was suppressed by disruption of the rcsC, rcsF, and yojN genes, which code for a sensor kinase, accessory positive factor, and phosphotransmitter, respectively, of the Rcs phosphorelay signal transduction system initially identified as regulating the capsular polysaccharide synthesis (cps) genes . Disruption of the rcsB gene coding for the response regulator of the system also suppressed the thermosensitivity, whereas disruption of cpsE did not . By monitoring the expression of a cpsB'-lac fusion, we showed that the Rcs system is activated in the pgsA mutant and is reverted to a wild-type level by the rcs mutations . These results indicate that envelope stress due to an acidic phospholipid deficiency activates the Rcs phosphorelay system and thereby causes the thermosensitive growth defect independent of the activation of capsule synthesis . Phenotypic Changes Resulting from Distinct Point Mutations in the Azospirillum brasilense glnA Gene, Encoding Glutamine Synthetase. Anne Van Dommelen, 2003.Sequencing the glnA genes of two chemically induced Azospirillum brasilense glutamine synthetase mutants revealed an Arg  Cys mutation, corresponding to the glutamate binding site, in one mutant and an AspAsn mutation, corresponding to the ammonium binding site, in the second mutant . The phenotypic changes in these mutants are discussed in relation to their genotypes .
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