|
|
|
|
|
|
Novel Roles of the Master Transcription Factors Spo0A and  B
for Survival and Sporulation of Bacillus subtilis at Low Growth Temperature.Marcelo B. Méndez, 2004. Spore development and stress resistance in Bacillus subtilis are governed by the master transcription factors Spo0A and B,
respectively . Here we show that the coding genes for both regulatory
proteins are dramatically induced, during logarithmic growth,
after a temperature downshift from 37 to 20°C . The lossof
B
reduces the stationary-phase viability of cold-adaptedcells 10- to
50-fold . Furthermore, we show that
B
activity isrequired at a late stage of development for efficient
sporulationat a low temperature . On the other hand, Spo0A loss
dramaticallyreduces the stationary-phase viability of cold-adapted
cells10,000-fold . We show that the requirement of Spo0A for cellular
survival during the cold is independent of the activity of the
key transition state regulator AbrB and of the simple loss of
sporulation ability . Furthermore, Spo0A, and not proficiencyin
sporulation, is required for the development of completestress
resistance of cold-adapted cells to heat shock [54°C,1 h], since a
loss of Spo0A, but not a loss of the essentialsporulation
transcription factor
F,
reduced the cellular survivalin response to heat by more than
1,000-fold . The overall resultsargue for new and important roles for
Spo0A in the developmentof full stress resistance by nonsporulating
cells and for
B
in sporulation proficiency at a low temperature.Functional Subsets of the VirB Type IV Transport Complex Proteins Involved in the Capacity of Agrobacterium tumefaciens To Serve as a Recipient in virB-Mediated Conjugal Transfer of Plasmid RSF1010. Zhenying Liu, 2003.The virB-encoded type IV transport complex of Agrobacterium tumefaciens mediates the transfer of DNA and proteins into plant cells, as well as the conjugal transfer of IncQ plasmids, such as RSF1010, between Agrobacterium strains . While several studies have indicated that there are physical interactions among the 11 VirB proteins, the functional significance of the interactions has been difficult to establish since all of the proteins are required for substrate transfer . Our previous studies, however, indicated that although all of the VirB proteins are required for the capacity of a strain to serve as an RSF1010 donor, only a subset of these proteins in the recipient is necessary to increase the conjugal frequency by 3 to 4 logs . The roles of particular groups of VirB proteins in this increased recipient activity were examined in the study reported here . Examination of the expression of subgroups of virB genes revealed that translation of virB6 is necessary for expression of downstream open reading frames . Expression of limited subsets of the VirB proteins in a recipient strain lacking the Ti plasmid revealed that the VirB7 to VirB10 proteins yield a subcomplex that is functional in the recipient assay but that the VirB1 to VirB4 proteins, as a group, dramatically increase this activity in strains expressing VirB7 to VirB10 . Finally, the membrane distribution and cross-linking patterns of VirB10, but not of VirB8 or VirB9, in a strain expressing only VirB7 to VirB10 are significantly altered compared to the patterns of the wild type . These characteristics are, however, restored to the wild-type status by coexpression of VirB1 to VirB3 . Taken together, these results define subsets of type IV transport complex proteins that are critical in allowing a strain to participate as a recipient in virB-mediated conjugal RSF1010 transfer . Urease-Positive Thermophilic Campylobacter Species. Motoo Matsuda, 2004. Regulation of Expression of mas and fadD28, Two Genes Involved in Production of Dimycocerosyl Phthiocerol, a Virulence Factor of Mycobacterium tuberculosis. Tatiana D. Sirakova, 2002.Transcriptional regulation of genes involved in the biosynthesis of cell wall lipids of Mycobacterium tuberculosis is poorly understood . The gene encoding mycocerosic acid synthase (mas) and fadD28, an adjoining acyl coenzyme A synthase gene, involved in the production of a virulence factor, dimycocerosyl phthiocerol, were cloned from Mycobacterium bovis BCG, and their promoters were analyzed . The putative promoters were fused to the xylE reporter gene, and its expression was measured in Escherichia coli, Mycobacterium smegmatis, and M . bovis BCG . In E . coli, the fadD28 promoter was not functional but the mas promoter was functional . Both fadD28 and mas promoters were functional in M . smegmatis, at approximately two- and sixfold-higher levels, respectively, than the BCG hsp60 promoter . In M . bovis BCG, the fadD28 and mas promoters were functional at three- and fivefold-higher levels, respectively, than the hsp60 promoter . Primer extension analyses identified transcriptional start points 60 and 182 bp upstream of the translational start codons of fadD28 and mas, respectively . Both promoters contain sequences similar to the canonical -10 and -35 hexamers recognized by the  70 subunit of RNA polymerase . Deletions of the upstream regions of both genes indicated that 324 bp of the fadD28 and 228 bp of the mas were essential for promoter activity . Further analysis of the mas promoter showed that a 213-bp region 581 bp upstream of the mas promoter acted as a putative transcriptional enhancer, promoting high-level expression of the mas gene when present in either direction . This represents the identification of a rare example of an enhancer-like element in mycobacteria .
Morphological and Phylogenetic Characterizations of Freshwater Thioploca Species from Lake Biwa, Japan, and Lake Constance, Germany. Hisaya Kojima, 2003.Filamentous, gliding, sulfide-oxidizing bacteria of the genus Thioploca were found on sediments in profundal areas of Lake Biwa, a Japanese freshwater mesotrophic lake, and were characterized morphologically and phylogenetically . The Lake Biwa Thioploca resembled morphologically Thioploca ingrica, a brackish water species from a Danish fjord . The diameters of individual trichomes were 3 to 5.6 µm; the diameters of complete Thioploca filaments ranged from 18 to 75 µm . The cell lengths ranged from 1.2 to 3.8 µm . In transmission electron microscope specimens stained with uranyl acetate, dense intracellular particles were found, which did not show any positive signals for phosphorus and sulfur in an X-ray analysis . The 16S rRNA gene of the Thioploca from Lake Biwa was amplified by using newly designed Thioploca-specific primers (706-Thioploca, Biwa160F, and Biwa829R) in combination with general bacterial primers in order to avoid nonspecific amplification of contaminating bacterial DNA . Denaturing gradient gel electrophoresis (DGGE) analysis of the three overlapping PCR products resulted in single DGGE bands, indicating that a single 16S rRNA gene had been amplified . With the same method, the Thioploca from Lake Constance was examined . The 16S rRNA sequence was verified by performing fluorescence in situ hybridization targeted at specific motifs of the Lake Biwa Thioploca . Positive signals were obtained with the bacterial probe EUB-338, the  -proteobacterial probe GAM42a, and probe Biwa829 targeting the Lake Biwa Thioploca . Based on the nearly complete 16S rRNA sequence and on morphological similarities, the Thioploca from Lake Biwa and the Thioploca from Lake Constance are closely related to T . ingrica and to each other .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
