Segmented filamentous bacteria (SFB) are nonpathogenic bacteria that are commonly found attached to the intestinal walls of many animals. Until now, these bacteria have not been cultured in vitro. Recently, a 16s rRNA sequence analysis revealed that SFB isolated from mice represent a distinct subline within the Cfostridium subphylum of the gram-positive bacteria. Since SFB isolated from mice, rats, and chickens are known to be host specific, we investigated the phylogenetic relationships among SFB obtained from these three hosts.Total DNAs from the intestinal floras of chickens and rats were used as templates for PCR amplification of 16s rRNA genes. PCR products were cloned and screened by a dot blot hybridization procedure to identify homologous sequences that cross-reacted with mouse SFB-specific oligonucleotide probes. A phylogenetic analysis of these 16s ribosomal DNA sequences revealed that SFB isolated from these three hosts form a natural group, which is peripherally related to the genus Cfostridiurn sensu strict0 (group I Cfostridiurn). The SFB obtained from chickens, rats, and mice had closely related, albeit different, 16s rRNA gene sequences. The observed levels of 16s rRNA sequence divergence, ca. 1.5 to 3%, together with host specificity, suggest that SFB isolated from mice, rats, and chickens represent different species and that coevolution of the SFB and their hosts occurred. "Candidatus Arthromitus" is proposed as the provisional generic name for this group of organisms.The small intestines of many animals (e.g., mice, rats, pigs, and other mammals, as well as chickens, amphibians, and insects) are inhabited by segmented filamentous bacteria (SFB), which are also referred to as long segmented filamentous organisms (reviewed in reference 10). These bacteria cannot be cultured in vitro and do not have official taxonomic names. Until recently, SFB could be recognized only on the basis of their morphology and their ecological niches. In intestines, these gram-positive, endospore-forming organisms are attached via holdfasts to the epithelial walls. In rodents, colonization by SFB is restricted to the ileum (4). In birds, SFB are also found in the ceca (9). No pathologic effects of SFB have been found, even in immunodeficient animals. SFB found in different animal species are morphologically very similar. However, attempts to transfer bacteria from one host species to another have revealed that SFB found in mice, rats, and chickens exhibit host specificity (1, 13, 21). It is not known if SFB that inhabit different hosts are taxonomically closely related or whether they belong to different species.In a recent study, the 16s rRNA-encoding gene sequence of SFB obtained from mice was determined (19). This study was greatly facilitated by the use of a monoculture of these organisms in formerly germfree mice (12). A comparative 16s rRNA * Corresponding author. Mailing address: Central Animal Laboratory, University of Nijmegen, P.O. Box 9101, NL-6500 HB Nijmegen, 'The Netherlands. analysis revealed that th...

In the summer of 2005, the Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae) was found for the first time in the Netherlands. It was collected on the premises of several horticultural companies that import the ornamental plant Dracaena sanderiana (Sparagalus: Dracaenaceae [Agavaceae]), known as Lucky bamboo, from southern China, an area endemic for this mosquito species and for arboviruses transmitted by this vector. Here we report the results of a 1-year survey of the distribution and vector status of Ae. albopictus in Lucky bamboo nurseries in the Netherlands (July 2006-June 2007). As it had been established previously that the presence of this species was linked to the import of Lucky bamboo, the survey was conducted only on sites owned by relevant import companies. In total, 569 adult Ae. albopictus were collected with mosquito traps from 15 of the 17 (88%) glasshouses used by Lucky bamboo importers, none of which were found to be infected with dengue virus. On two occasions there was evidence that Ae. albopictus had escaped from the glasshouses, but, overall, there was no evidence that a population had become established in the greenhouses or elsewhere.

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Ecosystems, including engineered ones, are complex systems in which microorganisms occur in heterogenous communities. Their behaviour in the environment is often unknown due to the lack of proper detection and identification techniques. Molecular ecology is a new field in which microbes can be recognized and their function can be understood at the DNA/RNA level without unreliable steps of cultivation of microbes. During the last few years genetically modified microbes have been constructed by recombinant DNA techniques for putative use in the environment. The slow progress in this field is due to the lack of integration of microbial ecology and molecular biology. In the present review, examples will be given of the use of DNA probes and marker genes in our study on the ecology of genetically modified microbes and wild‐type recalcitrant microorganisms that are difficult to cultivate or even 'non‐culturable'. Emphasis is given to the development and use of oligonucleotide probes directed towards 16S rRNA, to detect microbes in various engineered ecosystems: (i) Frankia in root nodules, and (li) propionate‐oxidizing sulfate‐reducing bacteria in anaerobic granular sludge. Expression of genes is demonstrated by studies on the localization of nifH transcripts in root nodules of Coriaria and Alnus. In addition we will describe examples of the use of marker genes (gusA gene and aphV gene) to study competition and genetic stability of released engineered Rhizobium and Streptomyces strains.

A method for precise and accurate quantification of 16S rDNA has been developed that uses competitive PCR and the QPCR System 5000. The method is based on co-amplification of 16S rDNA sequences, along with an internal standard sequence, using only one set of conserved eubacterial primers. Co-amplified PCR products are rapidly identified and quantified by measuring the electrochemiluminescent signals from specific oligonucleotide reporter probes that are directed against a hypervariable 16S rDNA sequence. Because in the exponential phase of amplification the different target sequences and the internal standard sequence are amplified with the same efficiency, unknown amounts of a target sequence in a sample can be inferred by extrapolating against a standard curve that is generated for the internal standard sequence. This method provides a rapid, nonradioactive and reliable way to simultaneously quantify different specific 16S rDNA targets that are present in low numbers, and may thus be suitable for enumeration of specific target microorganisms in environmental samples.

IgG, IgA and IgM ELISA antibody titers against Aspergillus fumigatus were elevated in sera of patients with aspergilloma and allergic bronchopulmonary aspergillosis (ABPA), showing higher titers for the IgG antibodies compared with the IgA and IgM antibodies. No differences were found between titers of identical antibody classes in the two groups of sera. IgG and IgA ELISA titers were highly specific whereas IgM ELISA showed more unspecific binding of IgM antibodies. Antibodies, as measured by ELISA, studied after fractionation of the antigen into fractions of decreasing molecular weight, showed a preferential binding by the high molecular weight fractions. Precipitating antibodies studied in patient sera did not always correspond with the IgG ELISA titers. IgE antibody binding was observed in all fractions from Sephadex G-100 fractionated components; maximum binding was found with fractions of 28,000–60,000 daltons. The low molecular weight fractions (18,000–<5,000 daltons) showed less IgE binding but the quantity of this fraction was higher. The discrepancies noted between the IgG and IgA ELISA titers and the binding of IgM or IgE antibodies indicate that antigenic components may in part differ in the binding of antibody classes.

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