RESUMEN
The Burkholderia cepacia complex (Bcc) consists of 17 closely related species of opportunistic bacterial pathogens, which are particularly problematic for cystic fibrosis patients and immunocompromised individuals. Bcc genomes consist of multiple replicons, and each strain sequenced to date has three chromosomes. In addition to genes thought to be essential for survival, each chromosome carries at least one rRNA operon. We isolated three mutants during a transposon mutagenesis screen that were non-pathogenic in a Caenorhabditis elegans infection model. It was demonstrated that these mutants had lost chromosome 3 (c3), and that the observed attenuation of virulence was a consequence of this. We constructed a c3 mini-replicon and used it to cure c3 from strains of several Bcc species by plasmid incompatibility, resulting in nine c3-null strains covering seven Bcc species. Phenotypic characterization of c3-null mutants revealed that they were attenuated in virulence in multiple infection hosts (rat, zebrafish, C. elegans, Galleria mellonella and Drosophila melanogaster), that they exhibited greatly diminished antifungal activity, and that c3 was required for d-xylose, fatty acid and pyrimidine utilization, as well as for exopolysaccharide production and proteolytic activity in some strains. In conclusion, we show that c3 is not an essential chromosomal element, rather a large plasmid that encodes virulence, secondary metabolism and other accessory functions in Bcc bacteria.
Asunto(s)
Complejo Burkholderia cepacia/genética , Complejo Burkholderia cepacia/patogenicidad , Cromosomas Bacterianos , Plásmidos , Factores de Virulencia/genética , Animales , Infecciones por Burkholderia/microbiología , Infecciones por Burkholderia/mortalidad , Infecciones por Burkholderia/patología , Caenorhabditis elegans , Elementos Transponibles de ADN , Modelos Animales de Enfermedad , Drosophila melanogaster , Lepidópteros , Redes y Vías Metabólicas/genética , Mutagénesis Insercional , Mutación , Ratas , Eliminación de Secuencia , Análisis de Supervivencia , Pez CebraRESUMEN
BACKGROUND: Automation of dietary assessments allows participant behaviour to be captured by video observation. It also allows clinicians to identify areas that effect reporting accuracy. The present observational study describes the differences in behaviour according to the type of foods selected by participants using a dietary assessment website encompassing diet history methodology. METHODS: Eleven free-living adults with type 2 diabetes mellitus were video recorded while using a dietary assessment website in a laboratory setting. Significant observable events were identified using TRANSANA software and matched for time of occurrence with grouped food item selections from the website. The frequency and proportion of behaviour types per food group were calculated and trends of associations between food groups and observed behaviour type were determined using weighted chi-square analyses. RESULTS: Sixteen categories of observed behaviour type were constructed from 7724 significant observable events. The food groups with the highest percentage of observed behaviour types were savoury sauces (7.66%), takeaways (6.47%), sugary foods (6.27%), fats and oils (5.93%), and alcoholic beverages (5.93%), which are all socially undesirable food groups. Self-touching of the face, head movement, postural movement and movement in the chair were observed significantly more often than other observed behaviour types across all food groups. CONCLUSIONS: Behaviours related to the reporting of foods during a dietary assessment may have significant implications for dietary practice.