The Leopoldina international symposium on parasitism, commensalism and symbiosis--common themes, different outcome.

The development of new methods, including genomics, which can even be applied to unculturable microorganisms, has significantly increased our knowledge about bacterial pathogenesis and symbiosis and, in consequence, is profoundly modifying our views on the evolution and the genetic and physiological basis of bacteria-host interactions. The presentations at this symposium revealed conceptual links between bacterial pathogenesis and symbiosis. The close co-operation of experts in both fields will result in significant synergy and new insights into basic mechanisms of bacteria-host interactions and their evolution.

Analysis of genome plasticity in pathogenic and commensal Escherichia coli isolates by use of DNA arrays.

Genomes of prokaryotes differ significantly in size and DNA composition. Escherichia coli is considered a model organism to analyze the processes involved in bacterial genome evolution, as the species comprises numerous pathogenic and commensal variants. Pathogenic and nonpathogenic E.

A novel ColV plasmid encoding type IV pili.

Many septicaemic Escherichia coli strains harbour ColV virulence plasmids. This paper describes pO78V, a conjugative ColV plasmid from an avian pathogenic E. coli strain that encodes type IV pili in addition to other virulence-related genes and tetracycline resistance.

Development of strain-specific PCR reactions for the detection of the probiotic Escherichia coli strain Nissle 1917 in fecal samples.

PCR was used to establish a specific detection system for the non-pathogenic Escherichia coli strain Nissle 1917 (DSM6601), which is used as a probiotic drug against intestinal disorders and diseases. Five PCR assays have been developed which are based on the chromosomally encoded major fimbrial subunit genes fimA (type 1 fimbriae) and focA (F1C fimbriae), and the two small cryptic plasmids pMUT1 and pMUT2. The assays were validated by testing a collection of 354 different pathogenic and non-pathogenic E.

The high-pathogenicity island is absent in human pathogens of Salmonella enterica subspecies I but present in isolates of subspecies III and VI.

In this study we tested 74 Salmonella strains of all eight Salmonella groups and were able to demonstrate the presence of two high-pathogenicity island types in strains of Salmonella groups IIIa, IIIb, and VI. Most high-pathogenicity island-positive isolates produced yersiniabactin under iron-limited conditions and were positive for the high-molecular-weight proteins HMWP1 and HMWP2.

Transcriptional analysis of the sfa determinant revealing mmRNA processing events in the biogenesis of S fimbriae in pathogenic Escherichia coli.

Among the virulence factors present in pathogenic extraintestinal Escherichia coli strains, expression of fimbrial adhesins is necessary for attachment to the host tissues and subsequent colonization. Occurrence of the sfa determinant coding for the S fimbriae is widespread among the uropathogens and meningitis isolates. The sfa operon consists of nine genes.

Quality assessment for three common conditions in primary care: validity and reliability of review criteria developed by expert panels for angina, asthma and type 2 diabetes.

Objectives: To field test the reliability, validity, and acceptability of review criteria for angina, asthma, and type 2 diabetes which had been developed by expert panels using a systematic process to combine evidence with expert opinion.

Design: Statistical analysis of data derived from a clinical audit, and postal questionnaire and semi-structured interviews with general practitioners and practice nurses in a representative sample of general practices in England.

Setting: 60 general practices in England.

New molecular methods to study gene functions in Candida infections.

Candida albicans has become a model system for human pathogenic fungi in clinical research, mainly due to the increasing number of Candida infections. Molecular techniques to study C. albicans virulence properties have been improved over the last few years, despite difficulties in genetic manipulation of this fungus.

Genetic structure and distribution of four pathogenicity islands (PAI I(536) to PAI IV(536)) of uropathogenic Escherichia coli strain 536.

For the uropathogenic Escherichia coli strain 536 (O6:K15:H31), the DNA sequences of three pathogenicity islands (PAIs) (PAI I(536) to PAI III(536)) and their flanking regions (about 270 kb) were determined to further characterize the virulence potential of this strain. PAI I(536) to PAI III(536) exhibit features typical of PAIs, such as (i) association with tRNA-encoding genes; (ii) G+C content differing from that of the host genome; (iii) flanking repeat structures; (iv) a mosaic-like structure comprising a multitude of functional, truncated, and nonfunctional putative open reading frames (ORFs) with known or unknown functions; and (v) the presence of many fragments of mobile genetic elements. PAI I(536) to PAI III(536) range between 68 and 102 kb in size.

A single nucleotide exchange in the wzy gene is responsible for the semirough O6 lipopolysaccharide phenotype and serum sensitivity of Escherichia coli strain Nissle 1917.

Structural analysis of lipopolysaccharide (LPS) isolated from semirough, serum-sensitive Escherichia coli strain Nissle 1917 (DSM 6601, serotype O6:K5:H1) revealed that this strain's LPS contains a bisphosphorylated hexaacyl lipid A and a tetradecasaccharide consisting of one E. coli O6 antigen repeating unit attached to the R1-type core. Configuration of the GlcNAc glycosidic linkage between O-antigen oligosaccharide and core (beta) differs from that interlinking the repeating units in the E.

Molecular evidence for a uniform microbial community in sponges from different oceans.

Sponges (class Porifera) are evolutionarily ancient metazoans that populate the tropical oceans in great abundances but also occur in temperate regions and even in freshwater. Sponges contain large numbers of bacteria that are embedded within the animal matrix. The phylogeny of these bacteria and the evolutionary age of the interaction are virtually unknown.

Transposase-dependent formation of circular IS256 derivatives in Staphylococcus epidermidis and Staphylococcus aureus.

IS256 is a highly active insertion sequence (IS) element of multiresistant staphylococci and enterococci. Here we show that, in a Staphylococcus epidermidis clinical isolate, as well as in recombinant Staphylococcus aureus and Escherichia coli carrying a single IS256 insertion on a plasmid, IS256 excises as an extrachromosomal circular DNA molecule. First, circles were identified that contained a complete copy of IS256.

Detection of the icaADBC gene cluster and biofilm formation in Staphylococcus epidermidis isolates from catheter-related urinary tract infections.

Biofilm production in Staphylococcus epidermidis is an important virulence factor that is mediated by the expression of the icaADBC operon. In this study 41 S. epidermidis isolates obtained from catheter-related urinary tract infections were analyzed for the presence of the icaADBC operon and biofilm formation.

Pathogenicity islands of uropathogenic E. coli and the evolution of virulence.

Uropathogenic Escherichia coli (UPEC) are the most important group of microorganisms responsible for urinary tract infection. UPEC differ from non-pathogenic E. coli and from other E.

Loss of regulatory protein RfaH attenuates virulence of uropathogenic Escherichia coli.

RfaH is a regulatory protein in Escherichia coli and Salmonella enterica serovar Typhimurium. Although it enhances expression of different factors that are proposed to play a role in bacterial virulence, a direct effect of RfaH on virulence has not been investigated so far. We report that inactivation of rfaH dramatically decreases the virulence of uropathogenic E.

Role of fibronectin in curli-mediated internalization.

Curli fibers of Escherichia coli mediate internalization of bacteria by eukaryotic cells. As curli fibers bind fibronectin with high affinity, the role of fibronectin in the uptake process was studied. The experiments presented here support the involvement of fibronectin in internalization of bacteria.

Efficient expression of the alpha-haemolysin determinant in the uropathogenic Escherichia coli strain 536 requires the leuX-encoded tRNA(5)(Leu).

The uropathogenic Escherichia coli strain 536 (O6:K15:H31) carries two alpha-haemolysin determinants which are located on different pathogenicity islands (PAI I(536) and PAI II(536)). PAI II(536) is associated with the tRNA gene leuX. The leuX-encoded tRNA(5)(Leu) is required for the efficient expression of the hly determinants in strain 536.

Legionella pneumophila: an aquatic microbe goes astray.

Legionella pneumophila is naturally found in fresh water were the bacteria parasitize within protozoa. It also survives planctonically in water or biofilms. Upon aerosol formation via man-made water systems, L.

Various bacterial pathogens and symbionts infect the amoeba Dictyostelium discoideum.

The haploid soil amoeba Dictyostelium discoideum is a suitable model organism to study host-pathogen interactions with Legionella pneumophila. In this study we show that D. discoideum AX2 is also susceptible to infection with other important human pathogens and obligate intracellular symbionts.

Influence of the leuX-encoded tRNA5(Leu) on the regulation of gene expression in pathogenic Escherichia coli.

The leuX gene encoding the minor tRNA5(Leu) is important for the expression of several virulence factors of pathogenic Escherichia coli strains. The differential usage of minor codons to control the expression of specialized genes has been proposed to be a general mechanism of bacteria to regulate gene expression at the posttranscriptional level. The minor codon usage theory foots on the biased codon usage of bacterial genes and the selective availability of tRNA isoacceptors.

Functional analysis of a vacuolar ABC transporter in wild-type Candida albicans reveals its involvement in virulence.

ATP-driven transport proteins belonging to the ATP-binding cassette (ABC) superfamily perform important functions in cell metabolism and detoxification. Compounds can be actively transported across membranes, including the plasma membrane or organellar membranes. The vacuole is an important organelle in fungal cells required for compartmentalization of metabolites as well as toxic substances.