Isolation and characterization of the dcw cluster from the piezophilic deep-sea bacterium Shewanella violacea

The ftsZ Gene of Mycobacterium smegmatis is expressed Through Multiple Transcripts

The principal essential bacterial cell division gene ftsZ is differentially expressed through multiple transcripts in diverse genera of bacteria in order to meet cell division requirements in compliance with the physiological niche of the organism under different environmental conditions. We initiated transcriptional analyses of ftsZ gene of the fast growing saprophytic mycobacterium, Mycobacterium smegmatis, as the first step towards understanding the requirements for FtsZ for cell division under different growth phases and stress conditions. Primer extension analyses identified four transcripts, T1, T2, T3, and T4. Transcriptional fusion studies using gfp showed that the respective putative promoter regions, P1, P2, P3, and P4, possessed promoter activity. T1, T2, and T3 were found to originate from the intergenic region between ftsZ and the upstream gene, ftsQ. T4 was initiated from the 3' portion of the open reading frame of ftsQ. RT-PCR analyses indicated co-transcription of ftsQ and ftsZ. The four transcripts were present in the cells at all growth phases and at different levels in the cells exposed to a variety of stress conditions in vitro. T2 and T3 were absent under hypoxia and nutrient-depleted stationary phase conditions, while the levels of T1 and T4 remained unaffected. These studies showed that ftsZ gene expression through multiple transcripts and differential expression of the transcripts at different growth phases and under stress conditions are conserved in M. smegmatis, like in other Actinomycetes.

Identification of genes regulated by changing salinity in the deep-sea bacterium Shewanella sp. WP3 using RNA arbitrarily primed PCR

The differential gene transcription of a deep-sea bacterium Shewanella sp. WP3 in response to changing salinity was analyzed by RNA fingerprinting using arbitrarily primed PCR (RAP-PCR). Ninety primer sets were used to scan two different RNA pools derived from cultures of 1% and 7% NaCl concentrations. Forty-three putative differential-expressed fragments were identified, cloned, and sequenced. Six out of the 43 fragments were confirmed to be truly differentially transcribed in terms of changing salinity. The deduced amino acid sequences of the six gene fragments showed highest identities (66-96%) with ribosomal protein L24, ATP binding protein, and chaperon protein HscA of Shewanella oneidensis MR-1 (Y6, Y9, and Y29); isocitrate lyase of Pseudomonas aeruginosa (Y15); peptidylprolyl cis-trans isomerase of Shewanella sp. SIB1 (Y21), glutamine synthetase of Shewanella violacea (Y25), respectively. Four genes (Y6, Y15, Y21, and Y25) were up regulated in 7% NaCl, while the other two (Y9 and Y29) contained more abundant transcripts in 1% NaCl. The data suggested that strategies involved in controlling protein synthesis, protein folding and/or trafficking, glutamate concentration, fatty acid metabolism, and substance transporting were used for salt adaptation in Shewanella sp. WP3. The expression patterns of the six genes in response to transient stress shocks including salt shock (3% NaCl shift to 12%), cold shock (15 degrees C shift to 0 degrees C), and high-hydrostatic pressure shock (0.1 MPa shift to 50 MPa) were further examined. Y29 encoding the putative HscA chaperon protein was indicated to be involved in adaptation of all the stresses tested.

Transcriptional analysis of the principal cell division gene, ftsZ, of Mycobacterium tuberculosis

Multiple promoters drive the expression of the principal cell division gene, ftsZ, in bacterial systems. Primer extension analysis of total RNA from Mycobacterium tuberculosis and a Mycobacterium smegmatis transformant containing 1.117 kb of the upstream region of M. tuberculosis ftsZ and promoter fusion studies identified six ftsZ transcripts and their promoters in the ftsQ open reading frame and ftsQ-ftsZ intergenic region. The presence of multiple promoters reflects the requirement to maintain a high basal level of, or to differentially regulate, FtsZ expression during different growth conditions of the pathogen in vivo.

Pressure-regulated biosynthesis of cytochrome bd in piezo- and psychrophilic deep-sea bacterium Shewanella violacea DSS12

The genes of cytochrome bd-encoding cydAB were identified from a deep-sea bacterium Shewanella violacea DSS12. These showed significant homologies with known cydAB gene sequences from various organisms. Additionally, highly conserved regions that are important for the enzymatic function were also conserved in cydA of S. violacea. Based on the results, transcriptional analysis of cydAB operon and cydDC operon (required for assembly of cytochrome bd) of S. violacea in microaerobic condition was performed under the growth condition of various pressures. The gene of cydA was expressed even under the condition of atmospheric pressure and its expression was enhanced with pressurization. On the other hand, the expression of cydC was strongly depressed under the condition of atmospheric pressure compared with the case under high pressure. It appeared spectrophotometrically that loss of cytochrome bd in S. violacea under atmospheric pressure shown in previous study is caused mainly by the loss of cydDC. Further, under the growth condition of atmospheric pressure, either less amount or no d-type cytochrome was expressed compared with the case of high-pressure condition even if the organism was grown under alkaline condition or in the presence of uncoupler, which are the inducible condition of d-type cytochrome in Escherichia coli. These results suggested that the significant amount of d-type cytochrome expression is specific event under the growth condition of high pressure.

Effects of high hydrostatic pressure on bacterial cytoskeleton FtsZ polymers in vivo and in vitro

Some rod-shaped bacteria, including Escherichia coli, exhibit cell filamentation without septum formation under high-hydrostatic-pressure conditions, indicating that the cell-division process is affected by hydrostatic pressure. The effects of elevated pressure on FtsZ-ring formation in E. coli cells were examined using indirect immunofluorescence microscopy. Elevated pressure of 40 MPa completely inhibited colony formation of E. coli cells under the cultivation conditions used, and the cells exhibited obviously filamentous shapes. In the elongated cells, normal cell-division processes appeared to be inhibited, because no FtsZ rings were observed by indirect immunofluorescent staining. In addition, it was observed that hydrostatic pressure dissociated the E. coli FtsZ polymers in vitro. These results suggest that high hydrostatic pressure directly affects cell survival and morphology through the dissociation of the cytoskeletal frameworks.

Effects of pressure on cell morphology and cell division of lactic acid bacteria

The effect of pressure and temperature on the growth of the mesophilic lactic acid bacteria Lactococcus lactis and Lactobacillus sanfranciscensis was studied. Both strains were piezosensitive. Lb. sanfranciscensis failed to grow at 50 MPa and the growth rate of Lc. lactis at 50 MPa was less than 30% of that at atmospheric pressure. An increase of growth temperature did not improve the piezotolerance of either organism. During growth under high-pressure conditions, the cell morphology was changed, and the cells were elongated as cell division was inhibited. At atmospheric pressure, temperatures above the optimal temperature for growth caused a similar effect on cell morphology and cell division in both bacteria as that observed under high-pressure conditions. The segregation and condensation of chromosomal DNA were observed by DAPI staining and occurred normally at high-pressure conditions independent of changes in cell morphology. Immunofluorescence microscopy of Lc. lactis cells demonstrated an inhibitory effect of high pressure on the formation of the FtsZ ring and this inhibition of the FtsZ ring formation is suggested to contribute to the altered cell morphology and growth inhibition induced by high pressure.