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PubMed1991

Molecular cloning and expression in Escherichia coli K-12 of the rfb gene cluster determining the O antigen of an E. coli O111 strain.

The O antigen of Escherichia coli O111 is identical in structure to that of Salmonella enterica serovar adelaide. Another O-antigen structure, similar to that of E. coli O111 and S. enterica serovar adelaide is found in both E. coli O55 and S. enterica serovar greenside. Both O-antigen structures contain colitose, a 3,6 dideoxyhexose found only rarely in the Enterobacteriaceae. The O-antigen structure is determined by genes generally located in the rfb gene cluster. We cloned the rfb gene cluster from an E. coli O111 strain (M92), and the clone expressed O antigen in both E. coli K-12 and a K-12 strain deleted for rfb. Lipopolysaccharide analysis showed that the O antigen produced by strains containing the cloned DNA is polymerized. The chain length of O antigen was affected by a region outside of rfb but linked to it and present on some of the plasmids containing rfb. The rfb region of M92 was analysed and compared, by DNA hybridization, with that of strains with related O antigens. The possible evolution of the rfb genes in these O antigen groups is discussed.

Antigens, Bacterial↗
PubMed2006

Experimental evolution of resistance in Paramecium caudatum against the bacterial parasite Holospora undulata.

Host-parasite coevolution is often described as a process of reciprocal adaptation and counter adaptation, driven by frequency-dependent selection. This requires that different parasite genotypes perform differently on different host genotypes. Such genotype-by-genotype interactions arise if adaptation to one host (or parasite) genotype reduces performance on others. These direct costs of adaptation can maintain genetic polymorphism and generate geographic patterns of local host or parasite adaptation. Fixation of all-resistant (or all-infective) genotypes is further prevented if adaptation trades off with other host (or parasite) life-history traits. For the host, such indirect costs of resistance refer to reduced fitness of resistant genotypes in the absence of parasites. We studied (co)evolution in experimental microcosms of several clones of the freshwater protozoan Paramecium caudatum, infected with the bacterial parasite Holospora undulata. After two and a half years of culture, inoculation of evolved and naive (never exposed to the parasite) hosts with evolved and founder parasites revealed an increase in host resistance, but not in parasite infectivity. A cross-infection experiment showed significant host clone-by-parasite isolate interactions, and evolved hosts tended to be more resistant to their own (local) parasites than to parasites from other hosts. Compared to naive clones, evolved host clones had lower division rates in the absence of the parasite. Thus, our study indicates de novo evolution of host resistance, associated with both direct and indirect costs. This illustrates how interactions with parasites can lead to the genetic divergence of initially identical populations.

Animals↗
PubMed2002

When phage, plasmids, and transposons collide: genomic islands, and conjugative- and mobilizable-transposons as a mosaic continuum.

Plasmids and bacteriophage represent the classical vectors for gene transfer within the horizontal gene pool. However, the more recent discovery of an increasing array of other mobile genetic elements (MGE) including genomic islands (GIs), conjugative transposons (CTns), and mobilizable transposons (MTns) which each integrate within the chromosome, offer an increasingly diverse assemblage contributing to bacterial adaptation and evolution. Molecular characterisation of these elements has revealed that they are comprised of functional modules derived from phage, plasmids, and transposons, and further that these modules are combined to generate a continuum of mosaic MGE. In particular, they are comprised of any one of three distinct types of recombinase, together with plasmid-derived transfer and mobilisation gene functions. This review highlights both the similarities and distinctions between these integrating transferable elements resulting from combination of the MGE toolbox.

Bacteriophages↗
PubMedDate not supplied

[Scleroma and rhinoscleroma].

Scleroma is a specific granulomatous disease of bacterial origin, chronic evolution, with election in respiratory tracts; nose lesion is practically constant and so justifies the term Rhinoscleroma. Although they are many endemic foci throughout the world and in particular in Africa, it is an uncommon disease, often not recognized for polymorphic. The cases recorded out of already known foci concerned generally migrants; autochtonous cases in France are really infrequent. Within the evolutive lesions diagnosis is made out of the isolation of the responsible germ (Klebsiella rhinoscleromatis) and the presence of the specific Mikulicz' cell. To find out localizations in the same patient, we utilize X Rays and endoscopy. Antibiotic therapy is of long duration but treats the affection and prepares the way of surgery intervention to eliminate cicatricial deformities. Relapses are caused by shortness of therapy and some difficulty to monitor patients. Mortel in the past, scleroma should nowadays, be better recognized to be better treated and cured.

Adult↗
PubMed2003

[Antibiotic resistance of the most frequently isolated germs at the Fann University Teaching Hospital between January 1999 and December 2000].

Bacterial infections take up an important place in tropical pathology and have an increased death-rate. Among the causes of this strong mortality, the resistance of bacteria to antibiotics keeps a dominant part. We carried out, between January 1999 and December 2000 a study aiming to establish the distribution of the most frequently isolated germs at the Laboratory of Bacteriology of Fann Hospital, their sensibility to antibiotics and the different phenotypes of resistance. We noticed a predominance of enterobacteria (69.30%), notably Escherichia coli (56.76%) and Klebsiella pneumoniae (47.69%), but also Staphylococcus aureus (13.91%). Enterobacteria present 39.7% of resistant phenotypes to beta-lactams (E. coli: 61.75% and K. pneumoniae: 47.69%). Only the third generation cephalosporins and fluoroquinolons are constantly actives on enterobacteria, and 69% of S. aureus strains are resistant to methicillin, and so to all beta-lactams. Pseudomonas aeruginosa become difficult to overcome: 51.13% of the strains produce beta-lactamase. The quinolons are the most active antibiotics on this germ. It is very important to settle network that will be in charge to survey the evolution of these bacterial resistances.

Bacteria↗
PubMed1998

[Bacterial resistance to antibiotics, an exemplary model of directed molecular evolution].

The simplest conceivable event that can occur at the gene level can result in the development of efficacious resistance tot antibiotics. The bacterial world behaves as an enormous organism whose cells can exchange their genes very easily. Accordingly, opportunities for the exchange of genetic material in nature are probably unlimited. This knowledge cannot be ignored. It leads to the important conclusion that the antibiotics are societal drugs. A resistance gene which has appeared somewhere in the world can travel far and fast.

Anti-Bacterial Agents↗
PubMed2004

[Antibiotic Use at German University Hospitals (Project INTERUNI-II). Results for Medical Intensive Care, Hematology-Oncology, and Other Medical Service Areas].

BACKGROUND: Excessive antibiotic use increases the risk of development and dissemination of bacterial resistance. A comparative analysis of the correlation between hospital antibiotic consumption and rates of bacterial resistance is needed for a better understanding of the complex relationship between antibiotic use and resistance. Apart from economic and market research studies, estimates of antibiotic consumption in German hospitals, however, are not available. METHODS: In a pilot project (INTERUNI-II), retrospective data from eight university hospital pharmacies covering the period 1998, 1999, and 2000 were collected to obtain estimates for the antibiotic use densities in the medical services of teaching hospitals. Antibiotic use densities were expressed as prescribed daily doses per 100 occupied bed days (PDD/100). The definition of prescribed daily doses was according to guidelines for antimicrobial therapy in adults with normal renal and hepatic function used in the participant hospitals. Means and ranges of antibiotic use densities were separately assessed for medical intensive care units (MICU), hematology-oncology services (HEMONC), and other medical services (OTHER MED). RESULTS: Mean antibiotic use density in internal medicine was 55.2 PDD/100 overall, ranging between 39.4 and 75.8 PDD/100 in the eight participant hospitals. In seven hospitals antibiotic use density increased during the years of observation. Antibiotic use was higher in MICU areas (3-year average, 122.3; range, 98-167 PDD/100) than in HEMONC (3-year average, 86.9; range, 67.8-129.4 PDD/100) and OTHER MED areas (3-year average, 42.8; range, 31.7-50.6 PDD/100). There was an increasing use of oral antibiotics resulting in a substantial proportion of oral agents among all antibacterial drugs outside MICU areas (year 2000, HEMONC, range, 36-74% of all PDD; OTHER MED, range, 43-59% of all PDD). beta-lactam antibiotics were the most frequently prescribed drugs (3-year average, 22.6 PDD/100). 56% of beta-lactam PDD belonged to the class of broad-spectrum beta-lactams (ranges, MICU, 49-82%; HEMONC, 61-89%; OTHER MED, 24-58%). Fluoroquinolones were the second most prescribed drug class (3-year average, 13 PDD/100). They were most frequently used in HEMONC (3-year average, MICU, 14.5; HEMONC 26.5; and OTHER MED 8.6 PDD/100, respectively). There was considerable variation between participant hospitals in the use of specific drug classes in given patient care areas. CONCLUSION: This retrospective study showed significant variation in overall and specific antibacterial drug class use between German teaching hospital medical services and defined patient care areas. Given the variation in the obtained estimates, targeted prospective hospital antibiotic use surveillance with fast data acquisition and analysis might offer an excellent opportunity to evaluate the impact of differences in antibiotic use and of revised therapy guidelines on the evolution of nosocomial bacterial resistance.

Administration, Oral↗
PubMed1985

Nucleotide sequence, secondary structure and evolution of the 5S ribosomal RNA from five bacterial species.

The nucleotide sequences of the 5S ribosomal RNAs of the bacteria Agrobacterium tumefaciens, Alcaligenes faecalis, Pseudomonas cepacia, Aquaspirillum serpens and Acinetobacter calcoaceticus have been determined. The sequences fit in a generally accepted model for 5S RNA secondary structure. However, a closer comparative examination of these and other bacterial 5S RNA primary structures reveals the potential of additional base pairing and of multiple equilibria between a set of slightly different alternative secondary structures in one area of the molecule. The phylogenetic position of the examined bacteria is derived from a 5S RNA sequence alignment by a clustering method and compared with the position derived on the basis of 16S ribosomal RNA oligonucleotide catalogs.

Bacteria↗
PubMed2004

Role of interleukin-18 in experimental group B streptococcal arthritis.

OBJECTIVE: To assess the role of interleukin-18 (IL-18) in the evolution of septic arthritis induced by group B streptococci (GBS) in mice. METHODS: CD1 mice were inoculated intravenously with 8 x 10(6) colony-forming units (CFU) of type IV GBS (strain 1/82), and administered intraperitoneally 1 hour before infection with anti-IL-18 monoclonal antibodies (0.25 mg/mouse). In a subsequent set of experiments, mice infected with a suboptimal arthritogenic dose of GBS (4 x 10(6) CFU/mouse) were administered different doses of recombinant IL-18 for 4 days, starting 1 hour after infection. Mortality, evolution of arthritis, bacterial clearance, joint histopathology, and cytokine production were examined in infected mice that did or did not receive treatment with anti-IL-18 antibodies or IL-18. RESULTS: IL-18 was produced during GBS infection. Neutralization of IL-18 resulted in a decrease in mortality rates, and in the incidence and severity of arthritis. Amelioration of arthritis was accompanied by a dramatic reduction in local IL-1 beta, IL-6, macrophage inflammatory protein 1 alpha (MIP-1 alpha) and MIP-2 production, and reduced bacterial burden. Administration of exogenous IL-18 resulted in increased mortality rates and increased incidence and severity of GBS arthritis, concomitant with a higher number of GBS and increased levels of IL-6, IL-1 beta, MIP-1 beta, and MIP-2 production in the joints. CONCLUSION: The present study indicated some involvement of IL-18 in the pathogenesis of GBS-induced arthritis. The role of IL-18 in joint pathology is shown by a regulatory effect on inflammatory mediator levels and local cell influx. Thus, IL-18 should be regarded as a potential therapeutic target in GBS infection and arthritis.

Animals↗
PubMed2000

Escherichia coli genome is composed of two distinct types of nucleotide sequences.

We calculated correlations of the nucleotide distributions along the E. coli genome. Subsequent cluster analysis of the correlation distributions showed that the genome was composed of two qualitatively different types of nucleotide sequences. The first type exhibited strong correlations of the genomic distributions of A with T and G with C, and high anticorrelations of A with C and G with T. In contrast, the second type was characterized by weak or negligible correlations typical of randomized sequences. Both types of sequences were almost equally abundant in the E. coli genome and their length varied from several hundred nucleotides to about 70 kilobases. They were not disjunct with respect to their (G + C) content but the high correlations and anticorrelations were rather characteristic for (A + T)-rich genomic segments. We offer possible explanations of the mosaic structure of the E. coli genome.

Base Composition↗
PubMed1997

Amelioration of bacterial genomes: rates of change and exchange.

Although bacterial species display wide variation in their overall GC contents, the genes within a particular species' genome are relatively similar in base composition. As a result, sequences that are novel to a bacterial genome-i.e., DNA introduced through recent horizontal transfer-often bear unusual sequence characteristics and can be distinguished from ancestral DNA. At the time of introgression, horizontally transferred genes reflect the base composition of the donor genome; but, over time, these sequences will ameliorate to reflect the DNA composition of the new genome because the introgressed genes are subject to the same mutational processes affecting all genes in the recipient genome. This process of amelioration is evident in a large group of genes involved in host-cell invasion by enteric bacteria and can be modeled to predict the amount of time required after transfer for foreign DNA to resemble native DNA. Furthermore, models of amelioration can be used to estimate the time of introgression of foreign genes in a chromosome. Applying this approach to a 1.43-megabase continuous sequence, we have calculated that the entire Escherichia coli chromosome contains more than 600 kb of horizontally transferred, protein-coding DNA. Estimates of amelioration times indicate that this DNA has accumulated at a rate of 31 kb per million years, which is on the order of the amount of variant DNA introduced by point mutations. This rate predicts that the E. coli and Salmonella enterica lineages have each gained and lost more than 3 megabases of novel DNA since their divergence.

Bacteria↗
PubMed2002

Evolutionary implications of phylogenetic analyses of the gene transfer agent (GTA) of Rhodobacter capsulatus.

The gene transfer agent (GTA) of the a-proteobacterium Rhodobacter capsulatus is a cell-controlled genetic exchange vector. Genes that encode the GTA structure are clustered in a 15-kb region of the R. capsulatus chromosome, and some of these genes show sequence similarity to known bacteriophage head and tail genes. However, the production of GTA is controlled at the level of transcription by a cellular two-component signal transduction system. This paper describes homologues of both the GTA structural gene cluster and the GTA regulatory genes in the a-proteobacteria Rhodopseudomonas palustris, Rhodobacter sphaeroides, Caulobacter crescentus, Agrobacterium tumefaciens and Brucella melitensis. These sequences were used in a phylogenetic tree approach to examine the evolutionary relationships of selected GTA proteins to these homologues and (pro)phage proteins, which was compared to a 16S rRNA tree. The data indicate that a GTA-like element was present in a single progenitor of the extant species that contain both GTA structural cluster and regulatory gene homologues. The evolutionary relationships of GTA structural proteins to (pro)phage proteins indicated by the phylogenetic tree patterns suggest a predominantly vertical descent of GTA-like sequences in the a-proteobacteria and little past gene exchange with (pro)phages.

Alphaproteobacteria↗
PubMed2006

Revisiting the molecular evolutionary history of Shigella spp.

The theory that Shigella is derived from multiple independent origins of Escherichia coli (Pupo et al. 2000) has been challenged by recent findings that the virulence plasmids (VPs) and the chromosomes share a similar evolutionary history (Escobar-Paramo et al. 2003), which suggests that an ancestral VP entered an E. coli strain only once, which gave rise to Shigella spp. In an attempt to resolve these conflicting theories, we constructed three phylogenetic trees in this study: a robust chromosomal tree using 23 housekeeping genes from 46 strains of Shigella and enteroinvasive E. coli (EIEC), a chromosomal tree using 4 housekeeping genes from 19 EcoR strains and 46 Shigella/EIEC strains, and a VP tree using 5 genes outside of the VP cell-entry region from 38 Shigella/EIEC strains. Both chromosomal trees group Shigella into three main clusters and five outliers, and strongly suggest that Shigella has multiple origins within E. coli. Most strikingly, the VP tree shows that the VPs from two main Shigella clusters, C1 and C2, are more closely related, which contradicts the chromosomal trees that place C2 and C3 next to each other but C1 at a distance. Additionally, we have identified a complete tra operon of the F-plasmid in the genome sequence of an EIEC strain and found that two other EIEC strains are also likely to possess a complete tra operon. All lines of evidence support an alternative multiorigin theory that transferable diverse ancestral VPs entered diverse origins of E. coli multiple times during a prolonged period of time, resulting in Shigella species with diverse genomes but similar pathogenic properties.

Chromosomes, Bacterial↗
PubMed1988

Kinetics of the interaction of the cytochrome c oxidase of Paracoccus denitrificans with its own and bovine cytochrome c.

We have devised a relatively simple method for the purification of cytochrome aa3 of Paracoccus denitrificans with three major subunits similar to those of the larger subunits of the mitochondrial cytochrome oxidase. This preparation has no c-type cytochrome. Studies were made of the oxidation of soluble cytochromes c from bovine heart and Paracoccus. The cytochrome-c oxidase activity was stimulated by low concentrations of either cytochrome c, providing an explanation for the multiphasic nature of plots of v/S versus v. Kinetics of the oxidation of bovine cytochrome c by the Paracoccus oxidase resembled those of bovine oxidase with bovine cytochrome c in every way; the Paracoccus oxidase with bovine cytochrome c can serve as an appropriate model for the mitochondrial system. The kinetics of the oxidation of the soluble Paracoccus cytochrome c by the Paracoccus oxidase were different from those seen with bovine cytochrome c, but resembled the latter if poly(L-lysine) was added to the assays. The important difference between the two species of cytochrome c is the more highly negative hemisphere on the side of the molecule way from the heme crevice in the Paracoccus cytochrome. Thus, the data emphasize the importance of all of the charged groups on cytochrome c in influencing the binding or electron transfer reactions of this oxidation-reduction system. The data also permit some interesting connotations about the possible evolution from the bacterial to the mitochondrial electron transport system.

Animals↗
PubMed1980

Persistence and spread of a chloramphenicol resistance-mediating plasmid in antigenic types of Escherichia coli, pathogenic for piglets.

All chloramphenicol-resistant Escherichia coli strains isolated from piglets in the State veterinary Serum Laboratory, Copenhagen, in 1974-1975 harbored plasmids of IncFII group with largely the same resistance markers. Two strains from 1978 carried plasmids with similar characters. Restriction enzyme analysis of DNA from these plasmids with restriction endonucleases EcoRI, BglII, and PstI shows that the Cm plasmids are extremely closely related; but the patterns obtained (particularly from PstI digests) enable the classification of the plasmids into groups. These bear a strong relation to time and place of isolation so that plasmids isolated on the same farm belong to the same group even when their host strains are of different antigenic types. It is concluded that these plasmids have evolved from a single plasmid.

Animals↗
PubMed1996

Bacterial host specificity of Lucinacea endosymbionts: interspecific variation in 16S rRNA sequences.

Three tropical lucinid clams (Codakia orbiculata, Codakia pectinella and Lucina nassula) from a shallow coastal environment have been studied regarding to their thioautotrophic bacterial endosymbionts. The 16S rRNA genes (rDNA) from these three endosymbionts were amplified using PCR. Phylogenetic analysis by distance matrix and parsimony methods always placed the newly examined symbionts within the monophyletic group composed of symbionts of the bivalve superfamily Lucinacea. A same single 16S rRNA sequence was found in C. orbiculata and C. pectinella and was identical to that found in C. orbicularis and Linga pensylvanica, two other lucinids living in the same type of environment. These data indicate that a same symbiont species may be associated with different host species. Lucina nassula host a symbiont with a distinct 16S rDNA sequence, but very closely related to the former.

Animals↗
PubMed1988

Monoclonal antibodies against bacteria.

Highlights are presented of most recent work in which monoclonal antibodies have been instrumental in the study of bacteria and their products. Topics summarized pertain to human and veterinary medicines, dentistry, phytopathology, ichthyology, and bacterial ecophysiology, differentiation, evolution and methanogenic biotechnology.

Journal Article↗