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1.
A 40 kb chromosomal fragment encoding Salmonella typhimurium invasion genes is absent from the corresponding region of the Escherichia coli K-12 chromosome 总被引:23,自引:0,他引:23
Many Salmonella typhimurium genes are required for bacterial entry into host cells. P22 transduction analysis has localized several invasion loci near minute 59 on the S. typhimurium chromosome. To further characterize the 59–60 min chromosomal region, we determined the physical and genetic map of 85 kb of S. typhimurium DNA between srl and cysC. It was previously shown that some of the invasion genes from this region are not present in Escherichia coli K-12. We examined whether other S. typhimurium genes on the 85 kb of DNA were similarly absent from E. coli We found that a contiguous 40 kb fragment of the S. typhimurium chromosome which encodes invasion genes is absent from the corresponding region of the E. coli K-12 chromosome and may represent a pathogenicity island. We speculate that acquisition of the 40 kb region must have significantly advanced the evolution of Salmonella as a pathogen. 相似文献
2.
The Collins and Richmond equation was used to analyze the growth of individual bacterial cells. Birth size was derived from
the size of deeply constricted cells in the sample. The analysis was applied to normalized and pooled data from electron micrographs
of Escherichia coli showing that cellular length, surface, and volume do not grow linearly as reported before. We present evidence that bacteria
grow exponentially during the division cycle, which is consistent with previous proposals. Our results confirm previous incorporation
studies that demonstrate basically exponential growth patterns for cell mass during the division cycle.
Received: 12 November 1997 / Accepted: 29 January 1998 相似文献
3.
C H Clarke 《Journal of theoretical biology》1982,96(3):461-471
The published nucleotide sequences of the E. coli and S. typhimurium trp A and trp B genes show a high degree of similarity between homologous genes of the two organisms, and an even greater degree of similarity between the amino acid sequences of the gene products. In spite of this, analysis of the nucleotide sequences reveals that there are marked differences between E. coli and S. typhimurium genes with respect to potential frameshift mutation hot-spots and dam and mec, mutationally important, methylation sites. Such existing differences may well lead to divergent evolution of these two, presently closely related, bacteria. Codon usage patterns in the trp A and trp B genes of E. coli and S. typhimurium, and the lac I gene of E. coli, have been re-analysed in terms of AT-rich, GC-rich, neutral, or unique codons and marked preferences found. In some cases particular amino acids are most often specified by AT-rich, in others by the GC-rich, alternative codons. In still other cases the codon preference depends on the gene studied. These patterns can be interpreted in terms of enteric bacterial evolution, via hybridizations, from ancestral bacteria with AT- or GC-rich DNA. 相似文献
4.
Mitsuhiro Itaya Dorothy McKelvin Sunil K. Chatterjie Robert J. Crouch 《Molecular & general genetics : MGG》1991,227(3):438-445
Summary We have cloned genes encoding RNase H from Escherichia coli rnh mutants, Salmonella typhimurium and Saccharomyces cerevisiae. Selection was accomplished by suppression of the temperature-sensitive growth phenotype of Escherichia coli strains containing the rnh-339::cat and either recB270 (Ts) or recC271 (Ts) mutations. RNases H from E. coli and S. typhimurium contained 155 amino acid residues and differed at only 11 positions. The S. cerevisiae and E. coli RNases H were about 30% homologous. A comparison of the amino acid sequences of several RNases H from cellular and retroviral sources revealed some strongly conserved regions as well as variable regions; the carboxyl-terminus was particularly variable. The overlapping, divergent promoter gene organization found in E. coli was observed to be present in S. typhimurium. 相似文献
5.
Summary Coliphage BF23 develops in Salmonella typhimurium rough strains. The phage is neither restricted nor modified by S. typhimurium. The growth patterns of the phage were slightly different in S. typhimurium than in Escherichia coli, although phage propagated on S. typhimurium is identical to the phage propagated in E. coli by several criteria used. Mutants of S. typhimurium resistant to BF23 were isolated and found to map (by P22-and Plmediated transduction) in the same position as bfe mutants of E. coli. The order of genes was: metB-argC-bfe-rif-purD-metA.Phage BF23 does not form plaques on smooth S. typhimurium strains, since the phage fails to adsorb irreversibly to smooth cells. Nevertheless, on solid agar, the phage prevents growth of many (but not all) smooth strains. Moreover, UV-and alkali-inactivated phage BF23, although unable to form plaques on sensitive hosts, retains the ability to prevent growth of the host on solid medium. This ability is sensitive to protease and resistant to DNAse and RNase. Heat treatment of the phage causes rapid loss of the cell-growth-preventing-ability whereas the ability to form plaques is lost much more slowly. These results lead to a proposal that phage BF23 virions carry a colicin-like factor that kills sensitive cells. 相似文献
6.
W. H. Koch G. Kopsidas B. Meffle A. S. Levine R. Woodgate 《Molecular & general genetics : MGG》1996,251(2):121-129
UnlikeEscherichia coli, the closely related bacteriumSalmonella typhimurium is relatively unresponsive to the mutagenic effects of DNA-damaging agents. Previous experiments have suggested that these phenotypic differences might result from reduced activity of theS. typhimurium UmuC protein. To investigate this possibility, we have taken advantage of the high degree of homology between the UmuC proteins ofE. coli andS. typhimurium and have constructed a series of plasmid-encoded chimeric proteins. The possibility that the phenotypic differences might be due to differential expression of the respective UmuC proteins was eliminated by constructing chimeric proteins that retained the first 25 N-terminal amino acids of either of the UmuC proteins (and presumably the same translational signals), but substituting the remaining 397 C-terminal amino acids with the corresponding segments from the reciprocal operon. Constructs expressing mostlyE. coli UmuC were moderately proficient for mutagenesis whereas those expressing mostlyS. typhimurium UmuC exhibited much lower frequencies of mutation, indicating that the activity of the UmuC protein ofS. typhimurium is indeed curtailed. The regions responsible for this phenotype were more precisely localized by introducing smaller segments of theS. typhimurium UmuC protein into the UmuC protein ofE. coli. While some regions could be interchanged with few or no phenotypic effects, substitution of residues 212–395 and 396–422 ofE. coli UmuC with those fromS. typhimurium resulted in reduced mutability, while substitution of residues 26–59 caused a dramatic loss of activity. We suggest, therefore, that the primary cause for the poor mutability ofS. typhimurium can be attributed to mutations located within residues 26–59 of theS. typhimurium UmuC protein. 相似文献
7.
Flores H Lobaton E Méndez-Diez S Tlupova S Cortez R 《Bulletin of mathematical biology》2005,67(1):137-168
Certain bacteria, such as Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurium), use multiple flagella often concentrated at one end of their bodies to induce locomotion. Each flagellum is formed in a
left-handed helix and has a motor at the base that rotates the flagellum in a corkscrew motion.We present a computational
model of the flagellar motion and their hydrodynamic interaction. The model is based on the equations of Stokes flow to describe
the fluid motion. The elasticity of the flagella is modeled with a network of elastic springs while the motor is represented
by a torque at the base of each flagellum. The fluid velocity due to the forces is described by regularized Stokeslets and
the velocity due to the torques by the associated regularized rotlets. Their expressions are derived. The model is used to
analyze the swimming motion of a single flagellum and of a group of three flagella in close proximity to one another. When
all flagellar motors rotate counterclockwise, the hydrodynamic interaction can lead to bundling. We present an analysis of
the flow surrounding the flagella. When at least one of the motors changes its direction of rotation, the same initial conditions
lead to a tumbling behavior characterized by the separation of the flagella, changes in their orientation, and no net swimming
motion. The analysis of the flow provides some intuition for these processes. 相似文献
8.
Mieczyslawa Derylo Maria Glowacka Anna Skorupska Zbigniew Lorkiewicz 《Archives of microbiology》1981,130(4):322-324
Lignobacter strain K17 is able to degrade aromatic compounds and to fix atmospheric nitrogen. It was proved that capacity for nitrogen fixation by Lignobacter was plasmid mediated. Plasmid pUCS100 (17.5 Mdal) carrying nif genes was transferred from Lignobacter to Escherichia coli SK1592 and Salmonella typhimurium. The transposon Tn9 was translocated to pUCS100 to facilitate selection of Nif+ bacteria. E. coli SK1592 harboring the new plasmid (pUCS101) reduced acetylene under anaerobic conditions. Plasmids pUCS100 and pUCS101 were not stably maintained in E. coli and S. typhimurium.Abbreviations Mdal
megadalton
- CsCl-EtBr
caesium chloride ethidium bromide
- m.o.i.
multiplicity of infection 相似文献
9.
Lorenzo Chiariotti Pietro Alifano M. Stella Carlomagno Carmelo B. Bruni 《Molecular & general genetics : MGG》1986,203(3):382-388
Summary In this paper we report the nucleotide sequence of the hisD gene of Escherichia coli and of the hisIE region of both E. coli and Salmonella typhimurium. The hisD gene codes for a bifunctional enzyme, l-histidinol: NAD+ oxidoreductase, of 434 amino acids with a molecular mass of 46,199 daltons. We established that the hisIE region of both S. typhimurium and E. coli is composed of a single gene and not, as previously believed, of two separate genes. The derived amino acid sequence indicates that the hisIE gene codes for a bifunctional protein of 203 amino acids with an approximate molecular mass of 22,700 daltons. We also determined the nucleotide sequence of a deletion mutant in S. typhimurium which abolishes the hisF and hisI functions but retains the hisE function. We deduced that the mutant produces a chimeric protein fusing the aminoterminal region of the upstream hisF gene to the carboxylterminal domain of the hisIE gene which encodes for the hisE function. In view of these results the structural and functional organization of the histidine operon in enteric bacteria needs to be revised. The operon is composed of only 8 genes and the pathway leading to the biosynthesis of the amino acid requires 11 enzymatic steps. 相似文献
10.
Salmonella typhimurium LB5000 andEscherichia coli JM109 were transformed by electroporation. In accordance with the chemical transformation methods, the growth phase of these
electrocompetent bacteria had a strong impact on transformation efficiency. Survival of bacteria, after the high-voltage electrical
pulse was also influenced by the growth phase. Both bacterial species were most successfully electrotransformed when microbial
cells were harvested at the late lag phase. The second optimum for transformation reachedE. coli cells in the mid-exponential andS. typhimurium cells in the late exponential phase. Transformation efficiencies ranged from 3.4×104 to 2.7×105 transformants per μg DNA in the case ofS. typhimurium and from 2.8 × 102 to 8.8×105 transformants per μg DNA in the case ofE. coli. Survival of cells after the electrical pulse in late lag and late exponential phases was about 20% higher than during other
phases of growth. Preparing electrocompetent cells from later phases of their growth is more useful for practice, because
it provides more biomass with good yield of transformants. 相似文献
11.
12.
Acanthamoeba polyphaga feeding on Salmonella typhimurium in a simple model biofilm were observed by light microscopy and a detailed record of interactions kept by digital image capture and image analysis. A strain of S. typhimurium SL1344 carrying a fis:gfp reporter construct (pPDT105) was used to assess intracellular growth in A. polyphaga on non-nutrient agar (NNA) plates. Invasion of the contractile vacuole (CV) was observed at a frequency of 1:100–1000 acanthamoebae at 35°C. The salmonellae contained in CVs illustrated significant up-regulation of fis relative to extracellular bacteria, indicating that they were in the early stages of logarithmic growth, and reached numbers of 100–200 cells per vacuole after 4 days. This is the first report of this mode of intracellular growth. Up-regulation of fis was also observed in a proportion of S. typhimurium cells contained within food vacuoles. Filamentation of S. typhimurium and E. coli cells was frequently observed in coculture with A. polyphaga on NNA plates, with bacterial cells reaching lengths of up to 500 µm after 10 days incubation at 35°C. A. polyphaga was also seen to mediate bacterial translocation over the agar surface; egested salmonellae subsequently formed microcolonies along amoebal tracks. This illustrated intracellular survival of a fraction of the S. typhimurium population. These phenomena suggest that protozoa such as A. polyhaga may play an important role in the ecology of S. typhimurium in soil and aquatic environments. 相似文献
13.
Julie E. Croft Donald R. Love Peter L. Bergquist 《Molecular & general genetics : MGG》1987,210(3):490-497
Summary The organisation of the leucine genes in Thermus thermophilus HB8 was analysed by examining the ability of recombinant DNAs to complement Escherichia coli mutations. The arrangement of the genes is different from that in the mesophilic bacteria E. coli and Salmonella typhimurium. The promoter responsible for the expression of the leuB, leuC and leuD genes of Thermus HB8 in E. coli was identified. The sequence of Thermus DNA containing this promoter revealed structural similarities to the promoter and attenuator regions of the E. coli leucine operon. 相似文献
14.
Discontinuity of homology of Escherichia coli and Salmonella typhimurium DNA in the lac region 总被引:9,自引:0,他引:9
Summary Partial homology of Salmonella typhimurium DNA to Escherichia coli DNA was demonstrated by Southern hybridization blots to exist on either side of the lac operon of E. coli but no homology was detected between S. typhimurium DNA and about 12 kb of E. coli DNA including the lac genes as well as about 5 kb of E. coli DNA between lac and proC. Thus portions of DNA seem to have been either added to the E. coli genome or deleted from the S. typhimurium genome since their divergence from a common ancestor. Although an IS1 element was located near the lac operon of E. coli, the insertional element was shown not to be near any of the junctures of discontinuity of E. coli - S. typhimurium homology near lac. 相似文献
15.
A rapid quantitative polymerase chain reaction (QPCR) method was developed for simultaneous detection of enteric bacteria from surface waters by utilizing a pair of universal primers that targeted four bacteria strains, namely Shigella dysenteriae, Vibrio cholerae, Salmonella typhimurium, and Escherichia coli. It was estimated that the QPCR method had a 94% confidence, and a detection limit as 2.7 Escherichia coli cells per sample in undiluted DNA extracts. The QPCR method was applied for the bacteriological examination of several surface waters in the urban area of Xi'an, China, and comparison was made with the conventional bacteria indicators determined by conventional membrane filter (MF) method. As a result, the calibrator cell equivalents (CCE) determined by QPCR was 2.2 to 5 times of the total coliform CFU, and the characteristics of the bacterial quality of different waters could be well presented by the QPCR results with a higher sensitivity. The coefficient of variation (CV) of data obtained by QPCR was smaller than that by traditional MF method, indicating a more stable analysis result. The QPCR method established by this study has manifest advantages over conventional methods in its rapidness and sensibility for the detection of pathogenic bacteria from surface water. It would provide a more reliable approach for the assessment of bacteriological risk of water environment. 相似文献
16.
Qing Wang Margherita Sacco Ezio Ricca Carmine T. Lago Maurilio DeFelice Joseph M. Calvo 《Molecular microbiology》1993,7(6):883-891
Lrp, a major regulatory protein in Escherichia coli, controls the expression of numerous operons, including ilvlH. Lrp binds to six sites upstream of ilvlH, and Lrp binding is required for ilvlH expression. We show here that an Lrp-like protein is also present in Salmonella typhimurium. This protein can bind both E. coli and S. typhimurium ilvlH DNA, as can E. coli Lrp. Methidiumpropyl-EDTA footprinting studies were performed with purified E. coli Lrp and S. typhimurium ilvlH DNA. Six binding sites were defined, three of them being similar to corresponding sites in E. coli, and three being organized differently. A consensus derived from six S. typhimurium sites is compatible with that derived from a similar analysis of E. coli sequences. 相似文献
17.
Nancy S. Taylor Ifor R. Beacham 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,411(2):216-221
A strain of Salmonella typhimurium has been constructed, by transfer of F-13 from Escherichia coli, which synthesises and secretes Escherichia coli UDPglucose hydrolase. Although Salmonella typhimurium does not normally contain a secreted (periplasmic) UDPglucose hydrolase, we find that it contains, like Escherichia coli, an intracellular inhibitor of the enzyme. 相似文献
18.
Hayashi Y Ishida H Hoshiai M Hoshiai K Kirimoto T Kanno T Nakano M Tajima K Miyake H Matsuura N Nakazawa H 《Molecular and cellular biochemistry》2000,215(1-2):39-46
Intestinal pathogens are exposed to various stress conditions during their infectious cycle. Anaerobiosis, one of such hostile condition, is offered by the host within gut and intestinal lumen, where survival, multiplication and entry into intestinal epithelial cells is priority for the invading pathogen. In the present study, a virulent strain of S. typhimurium (1402/84) was grown under anaerobic conditions and its virulence characteristics such as host cell binding, penetration and intracellular survival were compared with aerobic S. typhimurium. Anaerobically grown S. typhimurium showed significantly higher binding to immobilized mice enterocytes and intestinal mucus as compared to bacteria grown aerobically. Anaerobic bacteria also showed an early penetration of mucus and subsequent binding to underlying immobilized enterocytes, in vitro. Anaerobic S. typhimurium exhibited increased intracellular survival within spleen macrophages of mice and caused significantly higher fluid accumulation in ligated rabbit ileal loops as compared to aerobic bacteria. LD50 of anaerobic S. typhimurium was also observed to be 2 fold lower when compared to aerobic bacteria. Cell surface hydrophobicity of anaerobic S. typhimurium was also found to be significantly higher than aerobic bacteria. Thus, it appears that exposure of S. typhimurium to anaerobiosis results in its enhanced virulence, adhesion and penetration of host cells. 相似文献
19.
Albrecht Ludwig Claudia Tengel Susanne Bauer Andreas Bubert Roland Benz Hans-Joachim Mollenkopf Werner Goebel 《Molecular & general genetics : MGG》1995,249(5):474-486
A chromosomal fragment from Salmonella typhimurium, when cloned in Escherichia coli, generates a haemolytic phenotype. This fragment carries two genes, termed slyA and slyB. The expression of slyA is sufficient for the haemolytic phenotype. The haemolytic activity of E. coli carrying multiple copies of slyA is found mainly in the cytoplasm, with some in the periplasm of cells grown to stationary phase, but overexpression of SlyB, a 15 kDa lipoprotein probably located in the outer membrane, may lead to enhanced, albeit unspecific, release of the haemolytic activity into the medium. Polyclonal antibodies raised against a purified SlyA-HlyA fusion protein identified the over-expressed monomeric 17 kDa SlyA protein mainly in the cytoplasm of E. coli grown to stationary phase, although smaller amounts were also found in the periplasm and even in the culture supernatant. However, the anti-SlyA antibodies reacted with the SlyA protein in a periplasmic fraction that did not contain the haemolytic activity. Conversely, the periplasmic fraction exhibiting haemolytic activity did not contain the 17 kDa SlyA protein. Furthermore, S. typhimurium transformed with multiple copies of the slyA gene did not show a haemolytic phenotype when grown in rich culture media, although the SlyA protein was expressed in amounts similar to those in the recombinant E. coli strain. These results indicate that SlyA is not itself a cytolysin but rather induces in E. coli (but not in S. typhimurium) the synthesis of an uncharacterised, haemolytically active protein which forms pores with a diameter of about 2.6 nm in an artificial lipid bilayer. The SlyA protein thus seems to represent a regulation factor in Salmonella, as is also suggested by the similarity of the SlyA protein to some other bacterial regulatory proteins. slyA- and slyB-related genes were also obtained by PCR from E. coli, Shigella sp. and Citrobacter diversus but not from several other gram-negative bacteria tested. 相似文献
20.
《Gene》1998,212(2):189-196
The last two amino acids in the nascent peptide influence translation termination in E. coli (Mottagui-Tabar et al., 1994; Björnsson et al., 1996). We have compared the effects on termination in Escherichia coli, Bacillus subtilis and Salmonella typhimurium obtained by varying the −1 and −2 codons upstream of the weak UGAA stop signal. The peptide effect from the penultimate amino acid on translation termination in B. subtilis is similar to that seen in E. coli (with 66.5% RF-2 amino acid sequence similarity), whereas the influence in S. typhimurium (with 95.3% similarity to E. coli) is weaker. The effect of changing the −1 codon (P-site) is weaker in S. typhimurium as compared to those in E. coli and B. subtilis. RF-2s from E. coli and S. typhimurium have a threonine or alanine at position 246, respectively. This amino acid exchange in RF-2 can explain the difference in efficiency and toxicity during overexpression when E. coli and S. typhimurium are compared (Uno et al., 1996). However, B. subtilis RF-2 also has an alanine at that position, yet the sensitivity to the nascent peptide is similar to that in E. coli. Thus, the amino acid difference at position 246 in the RF-2 sequences cannot explain why termination in E. coli and B. subtilis is similar in peptide sensitivity while being different from that in S. typhimurium. Sequence alignments of RF-2 from the three bacteria show other regions of the molecule that could be involved in the functional interactions with the C-terminal end of the nascent peptide. 相似文献