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The taxonomic position of five recA gene clusters of Burkholderia cepacia complex (Bcc) isolates was determined using a polyphasic taxonomic approach, The levels of 16S rRNA and recA gene sequence similarity, multilocus sequence typing (MLST) data and the intermediate DNA-DNA binding values demonstrated that these five clusters represented five novel species within the Bcc. Biochemical identification of these species is difficult, as is the case for most Bcc species. However, identification of these novel species can be accomplished through recA gene sequence analysis, MLST and BOX-PCR profiling and by recA RFLP analysis. For diagnostic laboratories, recA gene sequence analysis offers the best combination of accuracy and simplicity. Based on these results, we propose five novel Bcc species, Burkholderia latens sp. nov. (type strain FIRENZE 3(T) =LMG 24064(T) =CCUG 54555(T)), Burkholderia diffusa sp. nov. (type strain AU1075(T) =LMG 24065(T) =CCUG 54558(T)), Burkholderia arboris sp. nov. (type strain ES0263A(T) =LMG 24066(T) =CCUG 54561(T)), Burkholderia seminalis sp. nov. (type strain AU0475(T) =LMG 24067(T) =CCUG 54564 (T)) and Burkholderia metallica sp. nov. (type strain AU0553(T) =LMG 24068(T) =CCUG 54567(T)). In the present study, we also demonstrate that Burkholderia ubonensis should be considered a member of the Bcc

BackgroundThe gut microbiota is critical for intestinal homeostasis. Recent studies have revealed the links between different types of dysbiosis and diseases inside and outside the intestine. Environmental exposure to pollutants (such as heavy metals) can also impair various physiological functions for good health. Here, we studied the impact of up to 8 weeks of oral lead and cadmium ingestion on the composition of the murine intestinal microbiome.ResultsPyrosequencing of 16S RNA sequences revealed minor but specific changes in bacterial commensal communities (at both family and genus levels) following oral exposure to the heavy metals, with notably low numbers of Lachnospiraceae and high numbers levels of Lactobacillaceae and Erysipelotrichaceacae (mainly due to changes in Turicibacter spp), relative to control animals.ConclusionsNon-absorbed heavy metals have a direct impact on the gut microbiota. In turn, this may impact the alimentary tract and overall gut homeostasis. Our results may enable more accurate assessment of the risk of intestinal disease associated with heavy metal ingestion.

According to the current insights, the predominant bacterial community in human feces is considered to be stable and unique for each individual over a prolonged period of time. In this study, the temporal stability of both the predominant population and a number of specific subpopulations of the fecal microbiota of four healthy volunteers was monitored for 6-12 weeks. For this purpose, a combination of different universal (V(3) and V(6)-V(8)) and genus- or group-specific (targeting the Bacteroides fragilis subgroup, the genera Bifidobacterium and Enterococcus and the Lactobacillus group, which also comprises the genera Leuconostoc, Pediococcus and Weisella) 16S rRNA gene primers was used. Denaturing gradient gel electrophoresis (DGGE) was used to analyze the 16S rRNA gene amplicons generating population fingerprints which were compared visually and by numerical analysis. DGGE profiles generated by universal primers were relatively stable over a three-month period and these profiles were grouped by numerical analysis in subject-specific clusters. In contrast, the genus- and group-specific primers yielded profiles with varying degrees of temporal stability. The Bacteroides fragilis subgroup and Bifidobacterium populations remained relatively stable which was also reflected by subject-specific profile clustering. The Lactobacillus group showed considerable variation even within a two-week period and resulted in complete loss of subject-grouping. The Enterococcus population was detectable by DGGE analysis in only half of the samples. In conclusion, numerical analysis of 16S rRNA gene-DGGE profiles clearly indicates that the predominant fecal microbiota is host-specific and relatively stable over a prolonged time period. However, some subpopulations tended to show temporal variations (e.g., the Lactobacillus group) whereas other autochthonous groups (e.g., the bifidobacteria and the Bacteroides fragilis subgroup) did not undergo major population shifts in time.