Biomedical subjects

C Schouler

Publications and source records attributed to C Schouler.

6 recordsLinked to original sources

PubMed1998

Combinational variation of restriction modification specificities in Lactococcus lactis.

Three genes coding for a type I R-M system related to the class C enzymes have been identified on the chromosome of Lactococcus lactis strain IL1403. In addition, plasmids were found that encode only the HsdS subunit that directs R-M specificity. The presence of these plasmids in IL1403 conferred a new R-M phenotype on the host, indicating that the plasmid-encoded HsdS is able to interact with the chromosomally encoded HsdR and HsdM subunits. Such combinational variation of type I R-M systems may facilitate the evolution of their specificity and thus reinforce bacterial resistance against invasive foreign unmethylated DNA.

Amino Acid Sequence↗

PubMed1998

A type IC restriction-modification system in Lactococcus lactis.

Three genes coding for the endonuclease, methylase, and specificity subunits of a type I restriction-modification (R-M) system in the Lactococcus lactis plasmid pIL2614 have been characterized. Plasmid location, sequence homologies, and inactivation studies indicated that this R-M system is most probably of type IC.

Amino Acid Sequence↗

PubMed1997

Characterization of cspB, a cold-shock-inducible gene from Lactococcus lactis, and evidence for a family of genes homologous to the Escherichia coli cspA major cold shock gene.

Upon temperature downshift, the major cold shock protein CspA is highly induced in Escherichia coli. This protein being conserved in other bacteria, we used a PCR-based approach with a pair of degenerate primers derived from highly conserved regions of the CspA-related proteins to evidence the presence of at least three related genes in Lactococcus lactis. One of them, cspB, was cloned and sequenced. It encodes a 66-residue protein which possesses 60% sequence identity with E. coli CspA. Following a cold shock from 30 to 15 degrees C, the level of the cspB mRNA transcript increased, as shown by Northern blot hybridization. In addition, induction of cspB-directed beta-galactosidase activity was observed. These results indicate that the L. lactis cspB gene is cold shock inducible.

Amino Acid Sequence↗

PubMed1994

Sequence and organization of the lactococcal prolate-headed bIL67 phage genome.

bIL67 is a broad-host-range prolate-headed phage that is active against Lactococcus cells. The complete phage genome sequence of 22195 bp was established. Thirty-seven open reading frames (ORFs) organized in two clusters were identified. Functions were assigned to the putative products of six of the ORFs on the basis of comparison of the deduced amino acid sequences to known proteins, analysis of structural features of the proteins and search for conserved motifs. These were a DNA polymerase, a protein involved in recombination, a lysin, a terminase subunit, a structural protein and a holin.

Amino Acid Sequence↗

PubMed1992

Characterization of Lactococcus lactis phage antigens.

Phage phi 197 is representative of a widespread lactococcal phage group characterized by a particular morphology (prolate head with a noncontractile tail). In order to develop an immunoenzymatic phage detection test, fusion proteins containing beta-galactosidase fused to epitopes of phage phi 197 structural proteins were constructed by cloning random DNA fragments from the phage genome upstream of a lacZ gene on a plasmid vector. Recombinant plasmids containing certain fragments encoded the synthesis of fusion proteins which react with polyclonal antibodies against the phage and confer a Lac+ phenotype on Escherichia coli. Three different epitopes were represented; phage-specific DNA fragments encoding these epitopes were mapped at three locations on the phage genome, and their nucleotide sequences were determined. Two fused phage antigens were conformational epitopes, whereas the phage epitope of protein encoded by the recombinant plasmid designated pOA17 was a denaturation-resistant epitope. This epitope was very immunogenic. Protein encoded by plasmid pOA17 was synthesized in large amounts from a strong promoter. Antibodies raised against this hybrid protein were used to identify the 46-kDa minor phage protein which provides the epitope. Antibody cross-reactivity of phages related to phi 197 showed that this epitope is well conserved in this genetic group.

Amino Acid Sequence↗

PubMedDate not supplied

Increased tracheal colonization in chickens without impairing pathogenic properties of avian pathogenic Escherichia coli MT78 with a fimH deletion.

Several studies suggest that the expression of F1 fimbriae could be involved in the virulence of Escherichia coli for chickens. F1 fimbriae display multivalent properties such as adhesion to epithelia or interaction with the immune system that imply specific interactions between the adhesin FimH and different cell receptors. We constructed a delta fimH mutant of the avian pathogenic E. coli MT78 and evaluated its in vivo colonization and pathogenicity, as compared to that of the parent strain. The generated mutant PA68 was unable to adhere in vitro to chicken epithelial pharyngeal or tracheal cells; mutant bacteria were mostly afimbriated although a minority of them displayed altered piliation phenotypes. Two inoculation routes were used to compare the ability of MT78 and PA68 to colonize the respiratory tract and to induce colibacillosis in chickens. In the first model, 2-wk-old axenic chickens were inoculated intratracheally with one or both E. coli strains, after primary infection with infectious bronchitis virus. In the second model, 3-wk-old specific-pathogen-free chickens were inoculated via the caudal thoracic air sac. After intratracheal inoculation, the delta fimH mutant was found to be a better colonizer than MT78 in the trachea of inoculated chickens. Furthermore, when both strains were inoculated simultaneously, the delta fimH mutant constituted 98% of the bacterial population in the trachea at day 7 postinoculation. Irrespective to the inoculation route, MT78 and PA68 showed similar abilities to induce macroscopic lesions in chickens, to provoke bacteremia, and to colonize the internal organs. However, 4 days after intra-air sac inoculation, bacterial counts of the mutant were lower in the spleen and liver than those of MT78. Our results show that FimH is not required for colonization of the trachea of axenic chickens by E. coli and that it is not a major determinant of bacterial pathogenicity. On the contrary, the lack of expression of FimH seems to favor the in vivo colonization of the trachea of chickens by E. coli.

Adhesins, Bacterial↗