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PubMed1994

[Serological parameters for the diagnosis and follow-up of toxoplasmosis. Experimental models].

BACKGROUND: Toxoplasmosis is a disease of increasing incidence. Its laboratory diagnosis is difficult, specially in acute toxoplasmosis. The data obtained in experimental models attempting to distinguish between acute and chronic toxoplasmosis by the simultaneous study of four serological tests: IgM and IgG antibodies, circulating antigens (CA) and antigens present in immune complexes (IC) are reported. METHODS: The evolution of IgM and IgG antibodies, CA and IC was followed in 3 murine models in acute, subacute and chronic toxoplasmosis, compared with the use of the ELISA technique. RESULTS: Acute toxoplasmosis is characterized by the presence of CA and IC in 100% of the individuals at high concentrations with IgM and IgG only being detectable at low concentrations. In subacute and chronic toxoplasmosis the response to IgG antibodies (100% in animals) is prominent, with detection of IgM being variable and the detection of CA and IC being reduced to the phase considered as acute. CONCLUSIONS: The detection of IgM and IgG antibodies, circulating antigens and immune complexes may be of great usefulness in the differentiation of acute, recently acquired or chronic toxoplasmosis.

Animals↗
PubMed1996

Physical mapping of Mycobacterium bovis BCG pasteur reveals differences from the genome map of Mycobacterium tuberculosis H37Rv and from M. bovis.

A Dral restriction map of the approximately 4.35 Mb circular chromosome of the vaccine strain Mycobacterium bovis BCG Pasteur was constructed by linking all 21 Dral fragments, ranging in size from 6 to 820 kb, using specific clones that spanned the Dral recognition sites as hybridization probes. The positions of 20 known genes were also established. Comparison of the resultant genome map with that of the virulent tubercle bacillus Mycobacterium tuberculosis H37Rv revealed extensive global conservation of the genomes of these two members of the M. tuberculosis complex. Possible sites of evolutionary rearrangements were localized on the chromosome of M. bovis BCG Pasteur by comparing the Asnl restriction profile with that of M. tuberculosis H37Rv. When selected cosmids from the corresponding areas of the genome of M. tuberculosis H37Rv were used as hybridization probes to examine different BCG strains, wild-type M. bovis and M. tuberculosis H37Rv, a number of deletions up to 10 kb in size, insertions and other polymorphisms were detected. In addition to the known deletions covering the genes for the protein antigens ESAT-6 and mpt64, other genetic loci exhibiting polymorphisms or rearrangements were detected in M. bovis BCG Pasteur.

BCG Vaccine↗
PubMed2004

A phylogenomic approach to reconstructing the diversification of serine proteases in fungi.

Using a phylogenomic approach with 10 fungi of very different virulence and habitat, we determined that there was substantial diversification of subtilase-type proteases early in ascomycete history (with subsequent loss in many lineages) but with no comparable diversification of trypsins. Patterns of intron loss and the degree of divergence between paralogues demonstrated that the proliferation of proteinase K subtilases and subtilisin type subtilases seen in pathogenic ascomycetes (Metarhizium anisopliae, Magnaporthe grisea, Fusarium graminearum) occurred after the basidiomycete/ascomycete split but predated radiation of ascomycete lineages. This suggests that the early ascomycetes had a lifestyle that selected for multiple proteases, whereas the current disparity in gene numbers between ascomycete lineages results from retention of genes in at least some pathogens that have been lost in other lineages (yeasts, Aspergillus nidulans, Neurospora crassa). A similar prevailing trend towards lineage specific gene loss of trypsins in saprophytes and some pathogens suggests that their phylogenetic breadth will have been much wider in early fungi than currently.

Cluster Analysis↗
PubMed1990

Differentiation between two biologically distinct classes of group A streptococci by limited substitutions of amino acids within the shared region of M protein-like molecules.

Group A streptococci can be categorized into two classes (I and II) based on immunodeterminants contained within a surface-exposed, conserved region (C repeat domain) of the major virulence factor, M protein. Previous studies have shown that several biological properties correlate strongly with streptococcal class, and thus, there is a strong impetus to precisely define the antigenic epitopes unique to class I and II M proteins. Using synthetic peptides, the binding sites of two class I-specific mAbs were mapped to distinct epitopes within the C repeat region of type 6 M protein (class I). A class II M protein-like gene (type 2) was cloned and sequenced, and the predicted amino acid sequence was compared for homology to class I and II molecules, whose sequences were previously reported. For a given C repeat block 35 amino acid residues in length, 20 residue positions were conserved among all sequences analyzed. Of the 15 variable amino acid positions, only four were class specific, and three of the four positions were localized in the area to which the class I-specific mAbs bound. The predicted secondary structures of class I and II C repeat blocks reveals that they are alpha-helical, except for a single area of disruption. In the class I molecules, the area of disruption corresponds to the class I-specific mAb binding sites. Importantly, the predicted conformational characteristics of this disruption differs for class I and II molecules. The data suggest that only limited changes in amino acid residues differentiate between class I and II molecules in the C repeat region. Therefore, selective (biological) pressures may have contributed to the evolution of these two classes of molecules.

Amino Acid Sequence↗
PubMed2007

Fungal peptide Destruxin A plays a specific role in suppressing the innate immune response in Drosophila melanogaster.

Destruxins are a class of insecticidal, anti-viral, and phytotoxic cyclic depsipeptides that are also studied for their toxicity to cancer cells. They are produced by various fungi, and a direct relationship has been established between Destruxin production and the virulence of the entomopathogen Metarhizium anisopliae. Aside from opening calcium channels, their in vivo mode of action during pathogenesis remains largely uncharacterized. To better understand the effects of a Destruxin, we looked at changes in gene expression following injection of Destruxin A into the fruit fly Drosophila melanogaster. Microarray results revealed reduced expression of various antimicrobial peptides that play a major role in the humoral immune response of the fly. Flies co-injected with a non-lethal dose of Destruxin A and the normally innocuous Gram-negative bacteria Escherichia coli, showed increased mortality and an accompanying increase in bacterial titers. Mortality due to sepsis was rescued through ectopic activation of components in the IMD pathway, one of two signal transduction pathways that are responsible for antimicrobial peptide induction. These results demonstrate a novel role for Destruxin A in specific suppression of the humoral immune response in insects.

Animals↗
PubMed2002

A novel DNA repair enzyme containing RNA recognition, G-patch and specific splicing factor 45-like motifs in the protozoan parasite Toxoplasma gondii.

We report the cloning and functional characterization of the full-length cDNA and gene encoding a Toxoplasma gondii DNA repair enzyme designated TgDRE. The gene is composed of three exons separated by two introns of 780 and 630 bp, and encodes a protein with a predicted molecular mass of 49.6 kDa. The native TgDRE protein, with a molecular mass of 60 kDa, is only detected in the virulent tachyzoite stage of T. gondii. However, the transcript is present in both asexual parasite stages, virulent tachyzoite and avirulent encysted bradyzoite. When an Escherichia coli mutant lacking ruvC endonuclease and recG helicase was transformed with TgDRE cDNA, a significant increase in resistance to DNA-damaging agents, such as UV light and mitomycin C, was observed. Moreover, database searches revealed that TgDRE orthologues were present in the genome sequences of the related apicomplexa parasites Plasmodium falciparum and Plasmodium yoelii, as well as in those of Arabidopsis thaliana, Drosophila melanogaster, Caenorhabditis elegans and Homo sapiens. This novel family of proteins is characterized by the presence of human splicing factor SF45-like, RNA recognition (RRM) and glycine-rich (G-patch) motifs. The presence of these motifs suggests that T. gondii TgDRE might also be involved in other biological functions such as RNA metabolism in addition to DNA-repair.

Amino Acid Motifs↗
PubMedDate not supplied

Life cycle of Trypanosoma cruzi (Y strain) in mice.

Since 1958, we have studied experimental Chagas' disease (CD) by subcutaneous inoculation of 1,000 blood forms of Trypanosoma cruzi (Y strain) in Balb/C. mice. Evolution of parasitemia remained constant, beginning on the 5th and 6th day of the disease, increasing progressively, achieving a maximum on about the 30th day. After another month, only a few forms were present, and they disappeared from the circulation after the third month, as determined from direct examination of slides and the use of a Neubauer Counting Chamber. These events coincided with the appearance of amastigote nests in the tissues (especially the cardiac ones), starting the first week, and following the Gauss parasitemia curve, but they were not in parallel until the chronic stage. In 1997, we began to note the following changes: Parasites appeared in the circulation during the first week and disappeared starting on the 7th day, and there was a coincident absence of the amastigote nests in the tissues. A careful study verified that young forms in the evolutionary cycle of T. cruzi (epi + amastigotes) began to appear alongside the trypomastigotes in the circulation on the 5th and 7th post-inoculation day. At the same time, rounded, oval, and spindle shapes were seen circulating through the capillaries and sinusoids of the tissues, principally of the hematopoietic organs. Stasis occurs because the diameter of the circulating parasites is greater than the vessels, and this makes them more visible. Examination of the sternal bone marrow revealed young cells with elongated forms and others truncated in the shape of a "C" occupying the internal surface of the blood cells that had empty central portions (erythrocytes?). We hypothesize that there could be a loss of virulence or mutation of the Y strain of Trypanosoma cruzi.

Animals↗
PubMed2006

Whole-genome sequence of Listeria welshimeri reveals common steps in genome reduction with Listeria innocua as compared to Listeria monocytogenes.

We present the complete genome sequence of Listeria welshimeri, a nonpathogenic member of the genus Listeria. Listeria welshimeri harbors a circular chromosome of 2,814,130 bp with 2,780 open reading frames. Comparative genomic analysis of chromosomal regions between L. welshimeri, Listeria innocua, and Listeria monocytogenes shows strong overall conservation of synteny, with the exception of the translocation of an F(o)F(1) ATP synthase. The smaller size of the L. welshimeri genome is the result of deletions in all of the genes involved in virulence and of "fitness" genes required for intracellular survival, transcription factors, and LPXTG- and LRR-containing proteins as well as 55 genes involved in carbohydrate transport and metabolism. In total, 482 genes are absent from L. welshimeri relative to L. monocytogenes. Of these, 249 deletions are commonly absent in both L. welshimeri and L. innocua, suggesting similar genome evolutionary paths from an ancestor. We also identified 311 genes specific to L. welshimeri that are absent in the other two species, indicating gene expansion in L. welshimeri, including horizontal gene transfer. The species L. welshimeri appears to have been derived from early evolutionary events and an ancestor more compact than L. monocytogenes that led to the emergence of nonpathogenic Listeria spp.

Chromosomes, Bacterial↗
PubMed2002

Identification of a chromosomal tra-like region in Agrobacterium tumefaciens.

The virD4 gene is one of the virulence genes present on the pTiC58 plasmid of Agrobacterium tumefaciens. Unexpectedly, we found that a pTi-free A. tumefaciens strain carried a protein of similar size to the plasmid-encoded VirD4 protein which reacted with VirD4-specific antibodies. This suggested that this strain may contain a homologue of the VirD4 protein. A chromosomal fragment encoding a protein of similar sequence to VirD4 was isolated and a 7.8 kilobase region surrounding the gene encoding this putative homologue was sequenced. This region contained four open reading frames, encoding putative proteins similar to proteins of known bacterial transfer and conjugation systems, viz., orf1 encoded a putative homologue of the TraA protein of the Rhizobium symbiosis plasmid pNGR234 and the TraA protein encoded by pTiC58 from A. tumefaciens plasmid pTiC58, orf3 encoded a protein very similar to the MobC protein encoded by the IncQ plasmid RSF1010 of E. coli and to MobS encoded by pTF1 from Thiobacillus ferrooxidans, whereas the predicted product of orf4 displayed similarity to the TraG protein encoded by the IncPalpha plasmid RP4 of E. coli, TraG and VirD4 encoded by A. tumefaciens plasmid pTiC58. The product of orf2 showed no significant similarity to any known protein. Preliminary assays with two orf4 mutants suggested that the product of this orf is involved in DNA transfer. The 7.8 kb chromosomal fragment seems to be closely related to the tra region of different conjugative plasmids and appears to be confined to Agrobacterium species, raising the question of the role of a chromosomal tra-like region during evolution.

Agrobacterium tumefaciens↗
PubMed1989

Nucleotide sequence, evolutionary origin and biological role of a rearranged cytokinin gene isolated from a wide host range biotype III Agrobacterium strain.

A DNA fragment with homology to the cytokinin (ipt) gene from biotype I Agrobacterium tumefaciens strain Ach5 was cloned from the Ti plasmid of the wide host range biotype III Agrobacterium strain Tm-4 and sequenced. The fragment contains an intact ipt coding sequence. However, the 3' non-coding region of this ipt gene is rearranged due to a 0.9 kb deletion fusing it to the 3' coding region of the neighbouring gene 6a, most of which was found to be deleted. The Tm-4 ipt gene is strongly related to the partially deleted ipt gene of the limited host range biotype III strain Ag162. To test its biological activity, the Tm-4 ipt gene was inserted into a specially constructed, disarmed Ti vector lacking tzs and tested on tobacco, where the rearranged ipt gene induced shoot formation. The cloned Tm-4 ipt gene was mutated with Tn5 and the intact gene on the wild-type Tm-4 Ti plasmid was replaced by the mutated gene. The resulting strain was avirulent on tobacco but normally virulent on the natural host of the wild-type strain Tm-4, grapevine. As the biotype I 6b gene diminishes the effect of a corresponding ipt gene, a larger Tm-4 fragment carrying both the ipt gene and an adjacent 6b-like gene was also tested on tobacco and compared with the Tm-4 ipt fragment alone and with an ipt and 6b/ipt fragment derived from Ach5. The Tm-4 6b gene diminishes the effect of the Tm-4 ipt gene, showing the Tm-4 6b gene to be active as well. The Tm-4 6b/ipt combination is less effective than the Ach5 combination. These results provide further insight into the molecular basis of the host range differences between limited host range and wide host range biotype III Agrobacterium strains and show that the WHR cytokinin gene, although active, does not significantly contribute to tumour formation on the natural host of the WHR biotype III strains, grapevine.

Base Sequence↗
PubMed1991

Molecular characterization of an IgA receptor from group B streptococci: sequence of the gene, identification of a proline-rich region with unique structure and isolation of N-terminal fragments with IgA-binding capacity.

Certain strains of group B streptococci express a cell surface protein that binds IgA and acts as a virulence factor. This IgA receptor is referred to here as protein Bac. The gene for protein Bac was cloned and expressed in Escherichia coli, and the complete nucleotide sequence was determined. The deduced amino acid sequence of 1134 residues includes a signal sequence of 37 amino acids and a putative membrane anchor region at the C-terminal end. The processed form of the receptor, 1097 residues, has a calculated molecular weight of 123,786. There are no cysteines in protein Bac, suggesting a fibrillar structure. The C-terminal half of the protein includes a 90 residues long region with a novel type of periodic structure, the "XPZ motif", in which every third amino acid is proline. Unlike other bacterial immunoglobulin-binding proteins, there are no long repeats in protein Bac. Clones which express only part of the protein Bac gene were used to show that IgA-binding takes place in the N-terminal part of the molecule. Protein Bac was originally described as an antigen called beta, but N-terminal fragments that bind IgA do not react with a reference serum against the beta antigen. These and other data indicate that protein Bac can be divided into two regions with different functions: an N-terminal IgA-binding region and a C-terminal region corresponding to the beta antigen. The IgA-binding region of protein Bac does not show any homology to protein Arp, the IgA receptor from group A streptococci, although these receptors have similar binding properties. This indicates that convergent evolution has favored the appearance of these two structurally different streptococcal IgA receptors.

Amino Acid Sequence↗
PubMedDate not supplied

Sequence analysis of the VP2 hypervariable region of nine infectious bursal disease virus isolates from mainland China.

The VP2 hypervariable region of infectious bursal disease virus (IBDV) from nine Mainland Chinese strains was amplified by reverse transcriptase/nested polymerase chain reaction and cloned into pGEM-T vector. The nine isolates, which were from the center (HN3), the north (Bj-1, B2/28, HD96), the east (JS-18 and AH-2), the northeast (D11-2, C4-2), and the west (Ts) of China, were sequenced and compared with each other and with six reference IBDV sequences. Clustering analysis separated the nine isolate into two groups. The six virulent isolates, propagated in bursae, formed the first group. They revealed only one to three amino acid changes from the very virulent (vv) European and Japanese isolates, suggesting that they might have the same origin as European and Japanese vvIBDV strains. On the basis of their distinct geographic origins, extensive dissemination of vvIBDV in China was indicated. (The other three chicken embryo fibroblast cell cultured isolates with mild pathogenicity were placed in the second group.) Their sequences correlated closely with those of the culture-adapted strains (Cu-1 (4) and Cj-801). None of the nine isolates showed very close sequence relationship with the antigenic variant strains from the USA. Although antigenic variants have been reported in China, the reverse transcriptase/polymerase chain reaction-restriction endonuclease analyses of the nine viruses tested herein were not similar to any U.S.A. variant strains on the basis of computer software analysis. Our results and conclusions agree with a previous molecular study of IBDV isolates from the south of China.

Amino Acid Sequence↗
PubMed1998

Chemical phenotype matching between a plant and its insect herbivore.

Two potential outcomes of a coevolutionary interaction are an escalating arms race and stable cycling. The general expectation has been that arms races predominate in cases of polygenic inheritance of resistance traits and permanent cycling predominates in cases in which resistance is controlled by major genes. In the interaction between Depressaria pastinacella, the parsnip webworm, and Pastinaca sativa, the wild parsnip, traits for plant resistance to insect herbivory (production of defensive furanocoumarins) as well as traits for herbivore "virulence" (ability to metabolize furanocoumarins) are characterized by continuous heritable variation. Furanocoumarin production in plants and rates of metabolism in insects were compared among four midwestern populations; these traits then were classified into four clusters describing multitrait phenotypes occurring in all or most of the populations. When the frequency of plant phenotypes belonging to each of the clusters is compared with the frequency of the insect phenotypes in each of the clusters across populations, a remarkable degree of frequency matching is revealed in three of the populations. That frequencies of phenotypes vary among populations is consistent with the fact that spatial variation occurs in the temporal cycling of phenotypes; such processes contribute in generating a geographic mosaic in this coevolutionary interaction on the landscape scale. Comparisons of contemporary plant phenotype distributions with phenotypes of herbarium specimens collected 9-125 years ago from across a similar latitudinal gradient, however, suggest that for at least one resistance trait-sphondin concentration-interactions with webworms have led to escalatory change.

Animals↗
PubMed2003

[Relationship between Helicobacter pylori infection and proliferation and apoptosis of gastric epithelial dysplasia cell].

BACKGROUND & OBJECTIVE: Gastric epithelial dysplasia is the precancerous lesion of gastric cancer. However, the mechanism that dysplasia evolves to malignancy is not clear. In order to clarify the relationship between Helicobacter pylori (HP) infection and its virulence factor and changes of cell kinetics of dysplasia, the authors measured the changes of proliferation and apoptosis and the status of HP infection. METHODS: A total of 117 gastric mucosal biopsy specimens were enrolled, including 12 of chronic superficial gastritis (CSG) and 105 of dysplasia. Dysplasia samples were divided into two groups: 35 of high-grade dysplasia [carcinogenesis group (n=30), regression group (n=5)], 70 of low-grade dysplasia [carcinogenesis group (n=18), regression group (n=52)]. The expression of proliferating cell nuclear antigen (PCNA) was measured by immunohistochemical staining; cell apoptosis was determined by terminal deoxynucleotidyl transferase mediated nick end labeling(TUNEL); the status of HP infection was detected by polymerase chain reaction(PCR) with specific primers of urea A and cagA gene. RESULTS: There was no significant difference of HP infection between dysplasia and CSG(84.76% vs. 83.33%), but CagA-positive strain infection rate in dysplasia was slightly higher than that in CSG (85.39% vs. 60.00%). Proliferation indexes(PI) in the patients with HP infection and CagA(+) strain infection were higher than that in the patients without HP infection and CagA(-)strain, respectively (P< 0.05). PI was positively associated with the status of HP and CagA(+) strains infection (P< 0.05). AI/PI ratio (AI: apoptosis index) was negatively associated with CagA-positive strain infection (P< 0.05). CONCLUSION: Gastric epithelial dysplasia cells have abnormal changes in PI and AI when it evolves to malignancy, and the abnormal cell kinetics is partly correlated with HP and CagA(+) strain infection. So treatment of HP infection may produce a good result for the evolution of dysplasia.

Apoptosis↗
PubMed2006

Impact of fungal drug transporters on fungicide sensitivity, multidrug resistance and virulence.

Drug transporters are membrane proteins that provide protection for organisms against natural toxic products and fungicides. In plant pathogens, drug transporters function in baseline sensitivity to fungicides, multidrug resistance (MDR) and virulence on host plants. This paper describes drug transporters of the filamentous fungi Aspergillus nidulans (Eidam) Winter, Botrytis cinerea Pers and Mycosphaerella graminicola (Fückel) Schroter that function in fungicide sensitivity and resistance. The fungi possess ATP-binding cassette (ABC) drug transporters that mediate MDR to fungicides in laboratory mutants. Similar mutants are not pronounced in field resistance to most classes of fungicide but may play a role in resistance to azoles. MDR may also explain historical cases of resistance to aromatic hydrocarbon fungicides and dodine. In clinical situations, MDR development in Candida albicans (Robin) Berkhout mediated by ABC transporters in patients suffering from candidiasis is common after prolonged treatment with azoles. Factors that can explain this striking difference between agricultural and clinical situations are discussed. Attention is also paid to the risk of MDR development in plant pathogens in the future. Finally, the paper describes the impact of fungal drug transporters on drug discovery.

Agriculture↗
PubMed2002

Evolution of pigeon Newcastle disease virus strains.

Twenty-seven Newcastle disease virus isolates obtained during the years 1998 and 1999 from racing pigeons were shown to be antigenically indistinguishable from the pigeon paramyxovirus type 1 (PPMV-1) viruses isolated in the years 1983 and 1984. Partial sequencing of 240 base pairs of the F gene demonstrated at least 94.7% identity at the nucleotide level between isolates from 1983 and 1984, and more recent viruses isolated in 1998 and 1999. Most of the nucleotide changes observed were silent mutations as only six amino acid changes were observed. Three amino acid substitutions were observed in the F2/F1 cleavage site. The sequence of the F2/F1 cleavage site of all isolates was typical for pathogenic paramyxovirus 1 viruses. Amino acids at the F2/F1 cleavage site changed from (112)GRQKRF(117) to (112)RRQKRF(117), (112)RRKKRF(117) or (112)RRRKRF(117). The motif (112)RRQKRF(117) was present in the majority of the isolates but the intracerebral pathogenicity indexes of PPMV-1 isolates having this motif was highly variable but largely lower (mean, 0.69) than that reported for PPMV-1 viruses isolated in the years 1983 and 1984 (mean, 1.44).

Amino Acid Sequence↗
PubMed1997

[Molecular variants of human papillomaviruses types 16, 18, and 45 in tumors of the uterine cervix in Mexico].

Carcinomas of the uterine cervix still constitutes the first cause of death from cancer among Mexican women. Certain types of human papillomaviruses (HPV) have been implicated in cervical cancer development; active viral sequences are usually found in more than 90% of cervical tumors, their genome contains two oncogenes that immortalize human cells in culture. Recent worldwide studies have shown the existence of molecular variants of known HPV types, mainly 16 and 18, thus permitting the establishment of viral spread during evolution, which seems as ancient as humankind. Phylogenetic studies have identified five major branches for HPV-16 and indicated that viral diversity seems associated with ethnic characteristics of the populations. In this work we searched for the presence of viral sequences among cervical tumors from the Mexican population. The existence of variants of HPV types 16, 18, and 45 was observed. One variant was found in more than half of HPV-16 positive tumors, and seems to exhibit a more aggressive behavior. In HPV-18 positive tumors, in addition to the prototype, two variants were detected in near a fourth of the samples. Finally, all HPV-45 positive tumors showed a new variant not yet reported in the literature. Some of these variants were found associated with specific histological types of cervical cancer, suggesting the participation of these variants in its genesis or aggressivity.

Africa↗
PubMed1998

Evidence for horizontal transfer from Streptococcus to Escherichia coli of the kfiD gene encoding the K5-specific UDP-glucose dehydrogenase.

Capsular polysaccharides are important virulence factors both in Gram-positive and Gram-negative bacteria. A similar cluster organization of the genes involved in the synthesis of bacterial exopolysaccharides has been postulated in both cases, suggesting that these clusters evolved by module assembly. Horizontal gene transfer has been postulated to explain the polymorphism found in these cellular polymers. The cap1 K and cap3A genes coding for the pneumococcal type 1 and type 3 UDP-glucose dehydrogenases, respectively, have been compared with other UDP-sugar dehydrogenases. We have observed that the evolutionary distance between Cap1K and Cap3A is approximately equal to that found between Cap1K (or Cap3A) and other UDP-GlcDH of families evolutionarily distant like KfiD, the dehydrogenase from Escherichia coli K5. On the basis of comparisons of G + C content, patterns of synonymous and nonsynonymous substitutions, dinucleotide frequencies, and codon usage bias, we conclude that the kfiD gene has been introduced into E. coli from an exogenous source, probably from a streptococcal species.

Bacterial Capsules↗