In vitro expression of a 22-kilodalton Yersinia pestis polypeptide immunologically related to the 25-kilodalton plasmid-encoded protein of the three pathogenic Yersinia species.

Antibodies raised against the 25-kilodalton (p25) plasmid-encoded polypeptide of Yersinia enterocolitica recognized the homologous protein in the three Yersinia species grown in vitro. This polypeptide was recovered from whole cells as well as from the fluid supernatant of bacteria grown at 37 degrees C in a Ca2+-deficient medium. Furthermore, a 22-kilodalton (p22) plasmid-encoded polypeptide immunologically related to p25 was found only in Y. pestis during early growth. After 30 h of culture, the Y. pestis p25 and p22 were completely degraded, whereas the intensity of the Y. enterocolitica p25 was decreased, but the protein was still detectable in the fluid supernatant. This proteolytic activity was independent of the presence of the virulence plasmid. Some disulfide bonds are probably involved in the quaternary structure of the p25 of the three pathogenic species and of the Y. pestis p22.

Ability of Yersinia enterocolitica cells to inactivate bacteriophage I at 25 degrees and 37 degrees C.

The presence of receptors to bacteriophage I of Y. enterocolitica in Y. enterocolitica cells grown at 37 degrees C was investigated. Protein extracts obtained from bacterial cells (strain 4052) grown at 25 degrees or 37 degrees C produced a diminution of free bacteriophage. Cultures of this strain inactivated phage I at 37 degrees C, and high titre suspensions of this phage showed bacteriocin-like activity. According to these results receptor sites must be present in Y. enterocolitica cells incubated at 37 degrees C.

Lack of correlation between plasmid-encoded outer membrane proteins and virulence of Yersinia enterocolitica.

When various strains of Yersinia enterocolitica belonging to serovars 0:1,3, 0:3, 0:5,27, 0:9 and 0:Tacoma harbouring 44- to 47-Md plasmids, or their spontaneously cured isogenic pairs, were inoculated (i. v., with standardized inocula) into Swiss female mice, the kinetics of bacterial survival in the spleen were followed, revealing inoculum destruction within 15 days. With both strains Ye8081 and WA (0:8, harbouring a 42-Md plasmid), the kinetics of bacterial growth ended in the death of mice. The early spleen bacterial uptake was the same with all strains studied, whether plasmid-harbouring or plasmid-less derivatives. In this study, virulent strain Ye8081 and both low-virulent IP383 and Ye9576 were shown to synthesize antigenically related outer membrane polypeptides plasmid-encoded at 37 degrees C and previously considered as virulence determinants.

Pigmented strains of Yersinia intermedia isolated from water.

Two Yersinia intermedia strains isolated from water produced a nondiffusible blue-grey pigment. Pigment production was influenced by culture conditions: it was inhibited at 37 degrees C and by growth in anaerobiosis. Dissociation into non-pigmented clones occurred spontaneously. Pigment could not be extracted by organic solvents.

Temperature-modulated immunogenicity to Yersinia pestis from Yersinia enterocolitica O3.

The ability of Yersinia enterocolitica O3, grown at 25 degrees C, to promote cross-immunity to Y. pestis was lost after repeated subcultures at 37 degrees C, which selected for bacterial populations having lower in vivo survival. Subculturing Y. enterocolitica O3 from 37 to 25 degrees C restored the cross-immunogenicity although the in vivo survival remained low.

Nucleotide sequence of the thrA gene of Escherichia coli.

The thrA gene of Escherichia coli codes for a single polypeptide chain having two enzymatic activities required for the biosynthesis of threonine, aspartokinase I and homoserine dehydrogenase I. This gene was cloned in a bacterial plasmid and its complete nucleotide sequence was established. It contains 2460 base pairs that encode for a polypeptide chain of 820 amino acids. The previously determined partial amino acid sequence of this protein is in good agreement with that predicted from the nucleotide sequence. The gene contains an internal sequence that resembles the structure of bacterial ribosome-binding sites, with an AUG preceded by four triplets, each of which can be converted to a nonsense codon by a single mutation. This suggests that the single polypeptide chain was formed by the fusion of two genes and that initiation of translation may occur inside the gene to give a protein fragment having only the homoserine dehydrogenase activity.

The primary structure of Escherichia coli K12 aspartokinase I-homoserine dehydrogenase I. Site of limited proteolytic cleavage by subtilisin.

The sequence of the first 25 residues of the homoserine dehydrogenase fragment, produced by limited proteolysis of aspartokinase I-homoserine dehydrogenase I with substilisin, has been determined. The sequence of a cyanogen bromide peptide (CB5, 59 residues), isolated from the entire protein, is also presented. Residues 1 to 18 of the subtilisin homoserine dehydrogenase fragment match the sequence 42 to 59 of peptide CB5.

The primary structure of Escherichia coli K12 aspartokinase I-homoserine dehydrogenase I-Isolation and characterisation of the peptides produced by cyanogen bromide.

The aspartokinase I-homoserine dehydrogenase I from Escherichia coli K12, composed of four identical subunits of molecular weight 86,000, was carboxy-methylated, fragmented by cyanogen bromide treatment and citraconylated. Using gel filtration, ion exchange chromatography and preparative paper electrophoresis and chromatography, 15 of 21 cyanogen bromide peptides were isolated in pure form and characterized by their composition, their N-terminal amino acid, and by their content of known cysteinyl or tryptophanyl tryptic peptides.