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H Schmieger

Publications and source records attributed to H Schmieger.

At least 19 recordsLinked to original sources
PubMed2001

Method for host-independent detection of generalized transducing bacteriophages in natural habitats.

Despite an increasing interest in horizontal gene transfer in bacteria, the role of generalized transduction in this process has not been well investigated yet. Certainly one of the reasons is that only a small fraction of general transducing bacteriophages have been characterized, because many bacterial hosts needed for propagation and identification are not culturable or are simply unknown. A method for host-independent detection of transducing bacteriophages was developed. Phage-encapsulated DNA was used as a template for PCR amplification of 16S ribosomal DNA using primers specific for the 16S rRNA genes of most eubacteria. Sequencing of the cloned amplification products permits the identification of the host bacteria. The Salmonella phage P22 was used as an example. Applying this method to a sample of the supernatant of the mixed liquor in the aeration tank of an activated sludge treatment works revealed the presence of transducing phages infecting several bacterial species for which such phages have not yet been described. This method is suitable for estimating the contribution of generalized transduction to horizontal gene transfer in different habitats.

Bacteriophages↗
PubMed1999

Molecular characterization and module composition of P22-related Salmonella phage genomes.

Genomes of newly isolated Salmonella phages were analysed by comparison of their EcoRI restriction patterns and by hybridization. Characteristic hybridization probes from reference phages P22, ES18 and E. coli phage lambda were chosen. Four probes selected from the lysis region examined the dispersal of the lambdoid lysis genes. Other probes characterized were the replication genes and part of the structural genes. The complex immunity region was investigated by means of hybridization as well as biological tests. The results showed the relationship of the isolated phages to the P22 branch of the lambdoid phages and revealed their modular genome organization consisting of different proportions of P22-related sequences. DNA restriction patterns of phages released from Salmonella strains sampled in limited geographical areas were significantly less heterogeneous than those of phages released from the worldwide sampled SARA collection. The use of prophage restriction patterns as a tool for the typing of Salmonellae to support the epidemiologic classification of pathogenic strains is discussed.

Bacteriophage P22↗
PubMed1999

Transduction of multiple drug resistance of Salmonella enterica serovar typhimurium DT104.

Epidemic strain Salmonella typhimurium DT104 is characterized by various multiresistance patterns. At least some of the resistance genes are organized as integrons. Resistance genes of DT104 isolates can be efficiently transduced by P22-like phage ES18 and by phage PDT17 which is released by all DT104 isolates so far analyzed. Cotransduction tests demonstrate that the resistance genes, although not organized in a unique integron, are tightly clustered on the Salmonella chromosome. The spread of resistance genes in this strain by generalized transduction is discussed.

Ampicillin Resistance↗
PubMed1999

Molecular survey of the Salmonella phage typing system of Anderson.

Typing phages for Salmonella and the prophages of their typical propagation strains were analyzed at the DNA level. Most of them belong to the P22 branch of the lambdoid phages. Acquisition of new plating properties of the typing phages by propagation in particular strains can be due to different host specific modifications of the DNA or to recombination events with residing prophages which are reflected by changes in the respective DNA restriction patterns. It is concluded that the actually available set of typing phages is a historically unique combination of strains.

Bacteriophage P22↗
PubMed1998

A comparative study on the frequency of prophages among natural isolates of Salmonella and Escherichia coli with emphasis on generalized transducers.

Several collections of natural isolates of the genus Salmonella and of the species Escherichia coli were studied for the release of viable temperate phages. The results indicated that functional prophage genomes may be a common constituent of all bacterial genomes of the investigated strains. About 99% of the Salmonella phages are capable of generalized transduction of chromosomal host markers and plasmids. The ratio of transducing E. coli phages is significantly lower.

Animals↗
PubMed1997

Sequence comparison of the genes for immunity, DNA replication, and cell lysis of the P22-related Salmonella phages ES18 and L.

Complementation and hybridization experiments with the generalized transducing Salmonella phages P22, ES18 and L revealed strong similarity between the phages L and P22; the genome of ES18 shows a mosaic structure. About half of its genome, including the early genes, is similar or completely homologous to P22; the other half of the morphologically different ES18 does not show any similarity to P22 nor to E. coli phage lambda. Sequence comparison of the early genes has confirmed that the C-immunity region of ES18 is identical with that of P22, whereas the same region of phage L shows poor (repressor gene) or no similarity. The 5'-terminus of the DNA replication gene 12 of ES18, however, is homologous to the same section of gene O of phage lambda. The lysis genes of ES18 again are identical to those of P22; only gene 15 is mosaic-like and has more similarity to gene Rz of phage lambda. These results will be discussed in terms of the theory of modular genome organization.

Bacteriophage P22↗
PubMed1997

Bacillus cereus may produce two or more diarrheal enterotoxins.

Bacillus cereus strains were tested for production of diarrheal enterotoxin by the reverse passive latex agglutination test and for presence of B. cereus enterotoxin gene (bceT) by polymerase chain reaction. About 50% of 56 B. cereus strains reacted positive in broth culture in the reverse passive latex agglutination test, while the bceT gene was detected in 41.1%. Sixteen percent of the strains were positive for both diarrheal enterotoxin and bceT gene. A 741 bp probe prepared from the polymerase chain reaction product detected bceT gene in all strains that were positive with the polymerase chain reaction. This study indicates a likelihood of two or more enterotoxins being produced by B. cereus which may be involved in causing diarrheal type food poisoning.

Bacillus cereus↗
PubMed1995

Frequency of generalized transducing phages in natural isolates of the Salmonella typhimurium complex.

From 85 natural isolates of the Salmonella typhimurium complex, including the Salmonella reference collection A (P. Beltran, S. A. Plock, N. H. Smith, T. S. Whittam, D. C. Old, and R. K. Selander, J. Gen. Microbiol. 137:601-606, 1991), 65 strains (76.5%) released 71 different temperate phages. Forty-three (93.5%) of 46 tested phages were able to transduce the chromosomal markers his+ and trp+ and the cloning vector pBR325.

Bacteriophage P22↗
PubMed1994

tRNA genes of Streptomyces lividans: new sequences and comparison of structure and organization with those of other bacteria.

Three closely linked Streptomyces lividans tRNA genes encoding two tRNA(Lys)s and a tRNA(Gly) were cloned and sequences. The structure of tRNA(Gly) is unusual for eubacterial tRNAs. Including those in previous reports (R. Sedlmeier and H. Schmieger, Nucleic Acids Res. 18:4027, 1990, and R. Sedlmeier, G. Linti, K. Gregor, and H. Schmieger, Gene 132:125-130, 1993), 18 S. lividans tRNA genes were physically mapped on the chromosome of the closely related strain Streptomyces coelicolor A3(2). The structure and organization of tRNA genes of S. lividans and S. coelicolor are compared with those of Escherichia coli and Bacillus subtilis.

Bacillus subtilis↗
PubMed1993

Sequences of tRNA-encoding genes and associated open reading frames of Streptomyces lividans.

A gene library of Streptomyces lividans has been screened for tRNA-encoding genes with labeled Streptomyces tRNA as a probe. By sequence analysis of hybridizing fragments, two single genes have been identified which code for tRNA(Asp) and tRNA(Gly). Associated with the tRNA(Gly) gene, there are three open reading frames (ORFs) which might code for gene products possibly involved in active transport processes through the bacterial membrane. The transcriptional organization of tRNAGly and the following ORFs was examined by high-resolution S1 mapping. A third clone carried a cluster of genes which encode two tRNA(Gln) and three tRNA(Glu). This cluster corresponds to a similar cluster previously described for Streptomyces rimosus [Plohl and Gamulin, Mol. Gen. Genet. 222 (1990) 129-134].

Amino Acid Sequence↗
PubMed1993

Bacteriophages induced by ciprofloxacin in a Borrelia burgdorferi skin isolate.

Two types of tailed bacteriophages were detected by electron microscopy in a Borrelia burgdorferi strain which had been isolated from infected human skin and exposed to the gyrase inhibitor ciprofloxacin. One of these phages displayed an isometric 30 nm head, a neck and a contractile tail 50-64 nm in length with a baseplate, according to an A-1 morphology. The other phage showing a B-1 morphology had a 30 nm isometric head as well and a long non-contractile straight tail 115-130 nm in length without neck and baseplate. Both types of phages could be found together within one plasmolysed spirochetal cell. We conclude that we are dealing with a lysogenic strain of Borrelia burgdorferi carrying at least two different prophages inducible by ciprofloxacin.

Adult↗
PubMed1993

The temperate phages RP2 and RP3 of Streptomyces rimosus.

The oxytetracycline-producing Streptomyces rimosus strains R6-65 and R7 (ATCC 10970) are lysogenic for the two narrow-host-range phages RP2 and RP3. Both phages are released at low frequency from the lysogenic strains and form plaques on 'cured' S. rimosus strains. RP2 and RP3 are of similar shape with flexible tails and contain double-stranded DNA of about 70% G+C with cohesive ends (group B1 of bacteriophage classification). The two phages also have identical, very slow, growth kinetics in S. rimosus, with a latent phase of about 6 h and a rise period of about 4 h. RP2 and RP3 are heteroimmune and they differ slightly in their size of phage particles and length of DNA (64.7 and 62.4 kb for RP2 and RP3, respectively). The restriction maps of the two phages are completely different, and hybridization experiments showed only one short region of sequence similarity (less than 430 bp); the two phages are thus essentially unrelated. Both phages lysogenize their hosts by recombination via defined attachment (att) sites. The positions of the attP sites have been localized on the restriction maps of RP2 and RP3 to restriction fragments of 800 and 300 bp, respectively. The prophages did not affect the level of oxytetracycline production or the genetic instability of this trait.

Attachment Sites, Microbiological↗
PubMed1992

Molecular genetic analysis of bacteriophage P22 gene 3 product, a protein involved in the initiation of headful DNA packaging.

Bacteriophage P22 DNA packaging events occur in processive series on concatemeric phage DNA molecules. At the point where such series initiate, the DNA is recognized at a site called pac, and most molecular left ends are generated within six short regions called end sites, which are present in a 120 base-pair region surrounding the pac site. The bacteriophage P22 genes 2 and 3 proteins are required for successful generation of these ends and DNA packaging during progeny virion assembly. Mutants lacking the 162-amino-acid gene 3 protein replicate DNA and assemble functional procapsids. In this report we describe the nucleotide changes and DNA packaging phenotypes of a number of missense mutations of gene 3, which give the phage a higher than normal frequency of generalized transduction. In cells infected by these mutants, more packaging events initiate on the host chromosome than in wild-type infections, so the mutations are thought to affect the specificity of packaging initiation. In addition to having this phenotype, these mutations affect the process of phage DNA packaging in detectable ways. They may: (1) alter the target site specificity for packaging; (2) make target site recognition more promiscuous; (3) affect end site utilization; (4) alter the pac site; and (5) cause apparent random DNA packaging series initiation on phage DNA.

Bacteriophage P22↗
PubMed1992

Sequence comparison among DNA fragments from different sources with pac site function for the packaging apparatus of Salmonella phage P22.

Two different DNA fragments, deriving from the P22-related bacteriophage LP7 and from the right IS element of transposon Tn10, have been identified which were recognized by the P22-packaging apparatus as pac-like signals. Their nucleotide sequences were compared with the known sequence of P22 gene 3 which contains the P22 pac site. Both sequences show similarity to a particular segment of P22 DNA close to a region identified earlier as part of pac.

Base Sequence↗
PubMed1991

Isolation of ribosomal RNA operons of Streptomyces lividans and sequence analysis of a 5S-rRNA gene.

Three clones containing rRNA genes have been isolated from a gene library of Streptomyces lividans. Two clones carried entire but different rRNA-operons. The third clone comprised the 3'-end of a 23S-rRNA gene, the entire 5S-rRNA gene and the spacer region between them. The nucleotide sequence starting within the 23S-rRNA gene beyond the putative transcription terminator downstream the 5S-rRNA gene has been determined (EMBL acc. no X58874).

Base Sequence↗
PubMed1991

Construction and transduction of a shuttle vector bearing the cos site of Streptomyces phage phi C31 and determination of its cohesive ends.

A plasmid has been constructed which is a bifunctional vector for Escherichia coli and for streptomycetes, containing the cos site of Streptomyces phage phi C31. It can be efficiently transduced into S. lividans 66 and into several other Streptomyces species. The nucleotide sequence of a 311-bp DNA fragment containing the cohesive ends has been determined. The cohesive ends consist of 10 bases protruding at the 3'-end of the phage genome.

Bacteriophages↗