Evie De Brandt

Taxon K, a complex within the Burkholderia cepacia complex, comprises at least two novel species, Burkholderia contaminans sp. nov. and Burkholderia lata sp. nov.

The aim of the present study was to re-examine the taxonomic position and structure of taxon K (also known as group K) within the Burkholderia cepacia complex (Bcc). For this purpose, a representative set of strains was examined by a traditional polyphasic taxonomic approach, by multilocus sequence typing (MLST) analysis and by analysis of available whole-genome sequences. Analysis of the recA gene sequence revealed three different lineages, designated recA-I, recA-II and recA-III. DNA-DNA hybridization experiments demonstrated that recA-I and recA-II isolates each represented a single novel species. However, DNA-DNA hybridization values of recA-II strains towards recA-III strains and among recA-III strains were at the threshold level for species delineation. By MLST, recA-I isolates were clearly distinguished from the others and represented a distinct lineage referred to as MLST-I, whereas recA-II and recA-III isolates formed a second MLST lineage referred to as MLST-II. A divergence value of 3.5 % was obtained when MLST-I was compared with MLST-II. The internal level of concatenated sequence divergence within MLST-I and MLST-II was 1.4 and 2.7 %, respectively; by comparison with the level of concatenated sequence divergence in established Bcc species, these data demonstrate that the MLST-I and MLST-II lineages represent two distinct species within the Bcc. The latter conclusion was supported by comparison of the whole-genome average nucleotide identity (ANI) level of MLST-I and MLST-II strains with strains of established Bcc species and by a whole-genome-based phylogenetic analysis. We formally propose to classify taxon K bacteria from the MLST-I and MLST-II lineages as Burkholderia contaminans sp. nov. (with strain J2956T =LMG 23361T =CCUG 55526T as the type strain) and Burkholderia lata sp. nov. (with strain 383T =ATCC 17760T =LMG 22485T =CCUG 55525T as the type strain), respectively. The MLST approach was confirmed as a valuable instrument in polyphasic taxonomic studies; more importantly, the cumulative data for about 1000 Bcc isolates analysed demonstrate that the 3 % concatenated sequence divergence level correlates with the 70 % DNA-DNA hybridization or 95 % whole-genome ANI threshold levels for species delineation.

Temporal stability analysis of the microbiota in human feces by denaturing gradient gel electrophoresis using universal and group-specific 16S rRNA gene primers

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.

Burkholderia latens sp nov., Burkholderia diffusa sp nov., Burkholderia arboris sp nov., Burkholderia seminalis sp nov and Burkholderia metallica sp nov., novel species within the Burkholderia cepacia complex

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.

Molecular monitoring of the fecal microbiota of healthy human subjects during administration of lactulose and Saccharomyces boulardii.

ABSTRACT Diet is a major factor in maintaining a healthy human gastrointestinal tract, and this has triggered the development of functional foods containing a probiotic and/or prebiotic component intended to improve the hosts health via modulation of the intestinal microbiota. In this study, a long-term placebo-controlled crossover feeding study in which each subject received several treatments was performed to monitor the effect of a prebiotic substrate (i.e., lactulose), a probiotic organism (i.e., Saccharomyces boulardii), and their synbiotic combination on the fecal microbiota of three groups of 10 healthy human subjects differing in prebiotic dose and/or intake of placebo versus synbiotic. For this purpose, denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene amplicons was used to detect possible changes in the overall bacterial composition using the universal V3 primer and to detect possible changes at the subpopulation level using group-specific primers targeting the Bacteroides fragilis subgroup, the genus Bifidobacterium, the Clostridium lituseburense group (cluster XI), and the Clostridium coccoides-Eubacterium rectale group (cluster XIVa). Although these populations remained fairly stable based on DGGE profiling, one pronounced change was observed in the universal fingerprint profiles after lactulose ingestion. Band position analysis and band sequencing revealed that a band appearing or intensifying following lactulose administration could be assigned to the species Bifidobacterium adolescentis. Subsequent analysis with real-time PCR (RT-PCR) indicated a statistically significant increase (P < 0.05) in total bifidobacteria in one of the three subject groups after lactulose administration, whereas a similar but nonsignificant trend was observed in the other two groups. Combined RT-PCR results from two subject groups indicated a borderline significant increase (P = 0.074) of B. adolescentis following lactulose intake. The probiotic yeast S. boulardii did not display any detectable universal changes in the DGGE profiles, nor did it influence the bifidobacterial levels. This study highlighted the capacity of an integrated approach consisting of DGGE analysis and RT-PCR to monitor and quantify pronounced changes in the fecal microbiota of healthy subjects upon functional food administration.

Novel Campylobacter lari-like bacteria from humans and molluscs: description of Campylobacter peloridis sp. nov., Campylobacter lari subsp. concheus subsp. nov. and Campylobacter lari subsp. lari subsp. nov.

A polyphasic study was undertaken to clarify the taxonomic position of Campylobacter lari-like strains isolated from shellfish and humans. The diversity within the strain collection was initially screened by means of fluorescent amplified fragment length polymorphism analysis and whole-cell protein electrophoresis, revealing the existence of two clusters distinct from C. lari and other Campylobacter species. The divergence of these clusters was confirmed by phenotypic analysis and by 16S rRNA and hsp60 gene sequence analysis. Phylogenetic analysis identified C. lari, Campylobacter jejuni, Campylobacter coli and Campylobacter insulaenigrae as the closest phylogenetic neighbours of both taxa. DNA-DNA hybridizations revealed that one cluster, comprising 10 strains, represented a novel Campylobacter species, for which the name Campylobacter peloridis sp. nov. is proposed, with 2314BVA(T) (=LMG 23910(T) =CCUG 55787(T)) as the type strain. The second cluster, comprising six strains, represents a novel subspecies within the species C. lari, for which the name Campylobacter lari subsp. concheus subsp. nov. is proposed, with 2897R(T) (=LMG 21009(T) =CCUG 55786(T)) as the type strain. The description of C. lari subsp. concheus has the effect of automatically creating the subspecies Campylobacter lari subsp. lari subsp. nov. (type strain LMG 8846(T)=NCTC 11352(T)).

Coamplification of eukaryotic DNA with 16S rRNA gene-based PCR primers: possible consequences for population fingerprinting of complex microbial communities.

The main aim of this study was to evaluate the specificity of three commonly used 16S rRNA gene-based polymerase chain reaction (PCR) primer sets for bacterial community analysis of samples contaminated with eukaryotic DNA. The specificity of primer sets targeting the V3, V3-V5, and V6-V8 hypervariable regions of the 16S rRNA gene was investigated in silico and by community fingerprinting of human and fish intestinal samples. Both in silico and PCR-based analysis revealed cross-reactivity of the V3 and V3-V5 primers with the 18S rRNA gene of human and sturgeon. The consequences of this primer anomaly were illustrated by denaturing gradient gel electrophoresis (DGGE) profiling of microbial communities in human feces and mixed gut of Siberian sturgeon. DGGE profiling indicated that the cross-reactivity of 16S rRNA gene primers with nontarget eukaryotic DNA might lead to an overestimation of bacterial biodiversity. This study has confirmed previous sporadic indications in literature indicating that several commonly applied 16S rRNA gene primer sets lack specificity toward bacteria in the presence of eukaryotic DNA. The phenomenon of cross-reactivity is a potential source of systematic error in all biodiversity studies where no subsequent analysis of individual community amplicons by cloning and sequencing is performed.

Achromobacter animicus sp. nov., Achromobacter mucicolens sp. nov., Achromobacter pulmonis sp. nov. and Achromobacter spiritinus sp. nov., from human clinical samples

The phenotypic and genotypic characteristics of fourteen human clinical Achromobacter strains representing four genogroups which were delineated by sequence analysis of nusA, eno, rpoB, gltB, lepA, nuoL and nrdA loci, demonstrated that they represent four novel Achromobacter species. The present study also characterized and provided two additional reference strains for Achromobacter ruhlandii and Achromobacter marplatensis, species for which, thus far, only single strains are publicly available, and further validated the use of 2.1% concatenated nusA, eno, rpoB, gltB, lepA, nuoL and nrdA sequence divergence as a threshold value for species delineation in this genus. Finally, although most Achromobacter species can be distinguished by biochemical characteristics, the present study also highlighted considerable phenotypic intraspecies variability and demonstrated that the type strains may be phenotypically poor representatives of the species. We propose to classify the fourteen human clinical strains as Achromobacter mucicolens sp. nov. (with strain LMG 26685(T) [=CCUG 61961(T)] as the type strain), Achromobacter animicus sp. nov. (with strain LMG 26690(T) [=CCUG 61966(T)] as the type strain), Achromobacter spiritinus sp. nov. (with strain LMG 26692(T) [=CCUG 61968(T)] as the type strain), and Achromobacter pulmonis sp. nov. (with strain LMG 26696(T) [=CCUG 61972(T)] as the type strain).

Cupriavidus necator isolates are able to fix nitrogen in symbiosis with different legume species.

The aim of the present study was to identify a collection of 35 Cupriavidus isolates at the species level and to examine their capacity to nodulate and fix N(2). These isolates were previously obtained from the root nodules of two promiscuous trap species, Phaseolus vulgaris and Leucaena leucocephala, inoculated with soil samples collected near Sesbania virgata plants growing in Minas Gerais (Brazil) pastures. Phenotypic and genotypic methods applied for this study were SDS-PAGE of whole-cell proteins, and 16S rRNA and gyrB gene sequencing. To confirm the ability to nodulate and fix N(2), the presence of the nodC and nifH genes was also determined, and an experiment was carried out with two representative isolates in order to authenticate them as legume nodule symbionts. All 35 isolates belonged to the betaproteobacterium Cupriavidus necator, they possessed the nodC and nifH genes, and two representative isolates were able to nodulate five different promiscuous legume species: Mimosa caesalpiniaefolia, L. leucocephala, Macroptilium atropurpureum, P. vulgaris and Vigna unguiculata. This is the first study to demonstrate that C. necator can nodulate legume species.

Comparative performance of different PCR assays for the identification of Campylobacter jejuni and Campylobacter coli.

The sensitivity and specificity of 7 PCR assays described for the identification of Campylobacter jejuni and Campylobacter coli were examined using alkaline cell lysates from a collection of 100 well characterized reference strains of C. jejuni, C. coli, Campylobacter lari and related Campylobacter, Helicobacter and Arcobacter species. Based on a preliminary evaluation, one multiplex test was excluded from further evaluation. The various assays differed considerably in sensitivity and specificity towards their target species. For C. coli, 4 of the 5 assays were 100% specific and sensitive, but for C. jejuni, none of the 5 assays were found to be 100% specific or sensitive. Subsequently, a statistically valid sample (n=263) was taken from a Belgian collection of 1906 human Campylobacter field isolates. This second collection was used to further evaluate two selected multiplex PCR assays. The present study indicates that PCR-based identification using each of the two selected multiplex PCR assays was highly reliable. The R-mPCR assay, followed by species-specific PCR assays or the ceu-oxr mPCR assay if necessary, is our current strategy of choice for the molecular identification of C. jejuni and C. coli. Results presented here should aid researchers in selecting a PCR assay suitable for their specific needs.

Anaerostipes butyraticus sp. nov., an anaerobic, butyrate-producing bacterium from Clostridium cluster XIVa isolated from broiler chicken caecal content, and emended description of the genus Anaerostipes

Four butyrate-producing isolates were obtained from the caecal content of a 4-week-old broiler chicken. The 16S rRNA gene sequences were determined and confirmed the close relatedness of the four isolates, which suggested that they were derived from a single bacterial clone. Phylogenetic analysis based on 16S rRNA gene sequences showed that its closest relatives were members of cluster XIVa of the Clostridium subphylum of Gram-positive bacteria and that the closest related type strain was Anaerostipes caccae L1-92(T) (94.5 % similarity). Similarity levels of 96-98 % with sequences from uncultured bacteria from human stool samples were observed. On the basis of morphological, biochemical and phylogenetic characteristics, this strain is assigned to a novel species in the genus Anaerostipes, for which the name Anaerostipes butyraticus sp. nov. is proposed. The type strain is 35-7(T) (=LMG 24724(T) =DSM 22094(T)). An emended description of the genus Anaerostipes is also provided.