New knowledge about the gut microbiota and its interaction with the host’s metabolic regulation has emerged during the last few decades. Several factors may affect the composition of the gut microbiota, including dietary fiber. Dietary fiber is not hydrolyzed by human digestive enzymes, but it is acted upon by gut microbes, and metabolites like short-chain fatty acids are produced. The short-chain fatty acids may be absorbed into the circulation and affect metabolic regulation in the host or be a substrate for other microbes. Some studies have shown improved insulin sensitivity, weight regulation, and reduced inflammation with increases in gut-derived short-chain fatty acids, all of which may reduce the risk of developing metabolic diseases. To what extent a dietary intervention with fiber may affect the human gut microbiota and hence metabolic regulation, is however, currently not well described. The aim of the present review is to summarize recent research on human randomized, controlled intervention studies investigating the effect of dietary fiber on gut microbiota and metabolic regulation. Metabolic regulation is discussed with respect to markers relating to glycemic regulation and lipid metabolism. Taken together, the papers on which the current review is based, suggest that dietary fiber has the potential to change the gut microbiota and alter metabolic regulation. However, due to the heterogeneity of the studies, a firm conclusion describing the causal relationship between gut microbiota and metabolic regulation remains elusive.

there is a growing awareness of the importance of indoor microbiomes for human health. Given their complexity, these microbiomes can only be adequately surveyed using high throughput sequencing techniques. oxford nanopore's Minion is the newest third generation sequencing technology on the market. With its many advantages such as portability, user friendliness, simplicity, speed of sequencing and long read length, the technology is now an actual contender to established sequencing platforms. MinION's main disadvantage is a relatively low read accuracy compared to several other platforms, although this is constantly improving. The present study, which appears to be the first of its kind, provides the results of a preliminary analysis of the microbial communities in indoor environments based on 16S rRNA gene amplicon sequencing, using both the Oxford Nanopore Technologies (ONT) MinIOn and the Illumina MiSeq DNA sequencers. At the level of family and above, there was no significant difference between the microbial compositions as revealed by the two platforms. However, at the genus, and particularly at the species level, the ONT MinION reported greater taxonomic resolution than illumina MiSeq.

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Escherichia albertii is an emerging human enteric pathogen (1). It belongs to the attaching and effacing group of bacteria, which also includes enteropathogenic and Shiga toxin-producing Escherichia coli (EPEC and STEC, respectively). Shiga toxin-producing E. albertii has been described, however, only in association with Shiga toxin (stx) subtype 2f (2). Sporadic infections as well as foodborne outbreaks caused by E. albertii have been reported, although rarely (3, 4). The prevalence, epidemiology, and clinical relevance of E. albertii are poorly understood, probably due to underestimation and misclassification of this pathogen (4). The phenotypic features distinguishing E. albertii from E. coli include a negative indole reaction and an inability to ferment lactose-, Dsorbitol, and D-xylose (1).In Norway, all presumptive enteropathogenic E. coli strains isolated from humans are submitted to the National Reference Laboratory for Enteropathogenic Bacteria for biochemical verification and for classification into well-known pathotypes according to virulence genes present (L. T. Brandal, A. L. Wester, H. Lange, I. Løbersli, B. A. Lindstedt, L. Vold, and G. Kapperud, submitted for publication). For outbreak detection purposes, all E. coli isolates are investigated with a generic multilocus variable-number tandem-repeat analysis (MLVA) (5).By these routine analyses, a nonmotile, ␤-D-glucuronidase-, lactose-, and xylose-negative isolate with eae and stx 2 was identified. This isolate had an MLVA profile often seen in E. albertii (NA-NA-NA-NA-NA-NA-5-X-X-NA, where NA designates a locus not present and X indicates different repeat numbers). A PCR specific for E. albertii was conducted (6), and 16S rRNA sequencing was performed (MicroSEC 500 16S rRNA gene bacterial sequencing kit; Life Technologies), both of which confirmed the isolate as E. albertii. stx 2 was subtyped and sequenced (7), and the expression of the stx 2a gene was verified (ImmunoCard STAT!EHEC; Meridian Bioscience Europe). All E. albertii isolates identified from 2008 to 2014 (n ϭ 39) were examined for the presence of stx 2f (8) and the cytolethal distending toxin B gene (cdtB) (9).Interestingly, the E. albertii isolate identified in the present study carried stx 2a , hitherto never reported in E. albertii. Additionally, we showed that stx 2a was expressed. This indicates that E. albertii is able to transduce not only stx 2f -carrying bacteriophages but also stx 2a -carrying bacteriophages. STEC harboring eae and stx 2a are considered highly virulent and have the ability to induce life-threatening hemolytic uremic syndrome (HUS) in infected patients (10). In contrast, STEC harboring stx 2f are associated with milder symptoms (11) and have, to our knowledge, never previously been detected in HUS patients. The patient infected with stx 2a -positive E. albertii was 48 years old, had bloody diarrhea, and was infected in Norway (Table 1). Domestically acquired E. albertii infection was commonly seen in patients included in the present study; however, the majori...

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The cold-water-fish pathogen Vibrio salmonicida expresses a functional bacterial luciferase but produces insufficient levels of its aliphatic-aldehyde substrate to be detectably luminous in culture. Our goals were to (i) better explain this cryptic bioluminescence phenotype through molecular characterization of the lux operon and (ii) test whether the bioluminescence gene cluster is associated with virulence. Cloning and sequencing of the V. salmonicida lux operon revealed that homologs of all of the genes required for luminescence are present: luxAB (luciferase) and luxCDE (aliphatic-aldehyde synthesis). The arrangement and sequence of these structural lux genes are conserved compared to those in related species of luminous bacteria. However, V. salmonicida strains have a novel arrangement and number of homologs of the luxR and luxI quorum-sensing regulatory genes. Reverse transcriptase PCR analysis suggests that this novel arrangement of quorum-sensing genes generates antisense transcripts that may be responsible for the reduced production of bioluminescence. In addition, infection with a strain in which the luxA gene was mutated resulted in a marked delay in mortality among Atlantic salmon relative to infection with the wild-type parent in single-strain challenge experiments. In mixed-strain competition between the luxA mutant and the wild type, the mutant was attenuated up to 50-fold. It remains unclear whether the attenuation results from a direct loss of luciferase or a polar disturbance elsewhere in the lux operon. Nevertheless, these findings document for the first time an association between a mutation in a structural lux gene and virulence, as well as provide a new molecular system to study Vibrio pathogenesis in a natural host.Marine bioluminescent bacteria have been the subjects of considerable interest because of the biochemistry that drives light production and their ability to initiate specific, long-term cooperative symbioses with many species of squids and fishes (20,35,45,51). Less is known about bioluminescence in species of bacteria that have the capacity to produce light yet are found in pathogenic associations with animal hosts (32,33,38). It has always been of interest to know whether luminescence plays a role in the biology of such pathogens, either to colonize the hosts or to grow in environmental niches. However, attempts to address such questions were limited because a model system in which to study the relationship between bioluminescence and pathogenesis was not available.In the five previously characterized species of luminous bacteria (Vibrio fischeri, Vibrio harveyi, Photobacterium leiognathi, Photobacterium phosphoreum, and Photorhabdus luminescens), the six structural genes for bioluminescence are contained within a locus termed the lux operon. With the exception of a duplication of luxB (designated luxF) in one species, these genes are arranged in the order luxCDABEG (1,9,16,28). luxA and luxB, respectively, encode the alpha and beta subunits of luciferase, the enzyme responsib...

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