Vang Quy Le

A metabolic model for members of the genus Tetrasphaera involved in enhanced biological phosphorus removal

Members of the genus Tetrasphaera are considered to be putative polyphosphate accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) from wastewater. Although abundant in Danish full-scale wastewater EBPR plants, how similar their ecophysiology is to ‘Candidatus Accumulibacter phosphatis’ is unclear, although they may occupy different ecological niches in EBPR communities. The genomes of four Tetrasphaera isolates (T. australiensis, T. japonica, T. elongata and T. jenkinsii) were sequenced and annotated, and the data used to construct metabolic models. These models incorporate central aspects of carbon and phosphorus metabolism critical to understanding their behavior under the alternating anaerobic/aerobic conditions encountered in EBPR systems. Key features of these metabolic pathways were investigated in pure cultures, although poor growth limited their analyses to T. japonica and T. elongata. Based on the models, we propose that under anaerobic conditions the Tetrasphaera-related PAOs take up glucose and ferment this to succinate and other components. They also synthesize glycogen as a storage polymer, using energy generated from the degradation of stored polyphosphate and substrate fermentation. During the aerobic phase, the stored glycogen is catabolized to provide energy for growth and to replenish the intracellular polyphosphate reserves needed for subsequent anaerobic metabolism. They are also able to denitrify. This physiology is markedly different to that displayed by ‘Candidatus Accumulibacter phosphatis’, and reveals Tetrasphaera populations to be unusual and physiologically versatile PAOs carrying out denitrification, fermentation and polyphosphate accumulation.

Nitrosospira lacus sp. nov., a psychrotolerant, ammonia-oxidizing bacterium from sandy lake sediment

A Gram-negative, spiral-shaped, chemolithotrophic, ammonia-oxidizing bacterium, designated APG3(T), was isolated into pure culture from sandy lake sediment collected from Green Lake, Seattle, WA, USA. Phylogenetic analyses based on the 16S rRNA gene sequence showed that strain APG3(T) belongs to cluster 0 of the genus Nitrosospira, which is presently not represented by described species, with Nitrosospira multiformis (cluster 3) as the closest species with a validly published name (identity of 98.6 % to the type strain). Strain APG3(T) grew at 4 °C but could not grow at 35 °C, indicating that this bacterium is psychrotolerant. Remarkably, the strain was able to grow over a wide range of pH (pH 5-9), which was greater than the pH range of any studied ammonia-oxidizing bacteria in pure culture. The DNA G+C content of the APG3(T) genome is 53.5 %, which is similar to that of Nitrosospira multiformis ATCC 25196(T) (53.9 %) but higher than that of Nitrosomonas europaea ATCC 19718 (50.7 %) and Nitrosomonas eutropha C71 (48.5 %). The average nucleotide identity (ANI) calculated for the genomes of strain APG3(T) and Nitrosospira multiformis ATCC 25196(T) was 75.45 %, significantly lower than the value of 95 % ANI that corresponds to the 70 % species-level cut-off based on DNA-DNA hybridization. Overall polyphasic taxonomy study indicated that strain APG3(T) represents a novel species in the genus Nitrosospira, for which the name Nitrosospira lacus sp. nov. is proposed (type strain APG3(T) = NCIMB 14869(T) = LMG 27536(T) = ATCC BAA-2542(T)).

ECEL1 mutation causes fetal arthrogryposis multiplex congenita

Arthrogryposis multiplex congenita (AMC) is a descriptor for the clinical finding of congenital fixation of multiple joints. We present a consanguineous healthy couple with two pregnancies described with AMC due to characteristic findings on ultrasonography of fixated knee extension and reduced fetal movement at the gestational age of 13 weeks + 2 days and 12 weeks + 4 days. Both pregnancies were terminated and postmortem examinations were performed. The postmortem examinations confirmed AMC and suggested a diagnosis of centronuclear myopathy (CNM) due to characteristic histological findings in muscle biopsies. Whole exome sequencing (WES) was performed on all four individuals and the outcome was filtered by application of multiple filtration parameters satisfying a recessive inheritance pattern. Only one gene, ECEL1, was predicted damaging and had previously been associated with neuromuscular disease or AMC. The variant found ECEL1 is a missense mutation in a highly conserved residue and was predicted pathogenic by prediction software. The finding expands the molecular basis of congenital contractures and the phenotypic spectrum of ECEL1 mutations. The histological pattern suggestive of CNM in the fetuses can expand the spectrum of genes causing CNM, as we propose that mutations in ECEL1 can cause CNM or a condition similar to this. Further investigation of this is needed and we advocate that future patients with similar clinical presentation or proven ECEL1 mutations are examined with muscle biopsy. Secondly, this study illustrates the great potential of the clinical application of WES in couples with recurrent abortions or stillborn neonates.

Draft Genome Sequence of Nitrosospira sp. Strain APG3, a Psychrotolerant Ammonia-Oxidizing Bacterium Isolated from Sandy Lake Sediment

ABSTRACT Bacteria in the genus Nitrosospira play vital roles in the nitrogen cycle. Nitrosospira sp. strain APG3 is a psychrotolerant betaproteobacterial ammonia-oxidizing bacterium isolated from freshwater lake sediment. The draft genome revealed that it represents a new species of cluster 0 Nitrosospira, which is presently not represented by described species.

In vivo gene expression in a Staphylococcus aureus prosthetic joint infection characterized by RNA sequencing and metabolomics: a pilot study.

BackgroundStaphylococcus aureus gene expression has been sparsely studied in deep-sited infections in humans. Here, we characterized the staphylococcal transcriptome in vivo and the joint fluid metabolome in a prosthetic joint infection with an acute presentation using deep RNA sequencing and nuclear magnetic resonance spectroscopy, respectively. We compared our findings with the genome, transcriptome and metabolome of the S. aureus joint fluid isolate grown in vitro.ResultFrom the transcriptome analysis we found increased expression of siderophore synthesis genes and multiple known virulence genes. The regulatory pattern of catabolic pathway genes indicated that the bacterial infection was sustained on amino acids, glycans and nucleosides. Upregulation of fermentation genes and the presence of ethanol in joint fluid indicated severe oxygen limitation in vivo.ConclusionThis single case study highlights the capacity of combined transcriptome and metabolome analyses for elucidating the pathogenesis of prosthetic infections of major clinical importance.

De novo KAT6B Mutation Identified with Whole-Exome Sequencing in a Girl with Say-Barber/Biesecker/Young-Simpson Syndrome

Say-Barber/Biesecker/Young-Simpson syndrome (SBBYSS; OMIM 603736) is a rare syndrome with multiple congenital anomalies/malformations. The clinical diagnosis is usually based on a phenotype with a mask-like face and severe blepharophimosis and ptosis as well as other distinctive facial traits. We present a girl with dysmorphic features, an atrial septal defect, and developmental delay. Previous genetic testing (array-CGH, 22q11 deletion, PTPN11 and MLL2 mutation analysis) gave normal results. We performed whole-exome sequencing (WES) and identified a heterozygous nonsense mutation in the KAT6B gene, NM_001256468.1: c.4943C>G (p.S1648*). The mutation led to a premature stop codon and occurred de novo. KAT6B sequence variants have previously been identified in patients with SBBYSS, and the phenotype of the girl is similar to other patients diagnosed with SBBYSS. This case report provides additional evidence for the correlation between the KAT6B mutation and SBBYSS. If a patient is suspected of having a blepharophimosis syndrome or SBBYSS, we recommend sequencing the KAT6B gene. This is a further example showing that WES can assist diagnosis.

The PHF6 Mutation c.1A>G; pM1V Causes Börjeson-Forsman-Lehmann Syndrome in a Family with Four Affected Young Boys

The family presented with 4 boys, 2 sets of brothers, with unexplained intellectual disability. Numerous analyses had been conducted over more than a decade, without reaching a final clinical or molecular diagnosis. According to the pedigree, an X-linked inheritance pattern was strongly suspected. Whole-exome sequencing (WES) with targeted analysis of the coding regions of the X chromosome was carried out in the 4 boys, their mothers, and their shared grandmother. A filtering process searching for nonsynonymous variants and variants in the exon-intron boundaries revealed one variant, c.1A>G; pM1V, in the first codon of the PHF6 gene. The variant was hemizygous in the 4 boys and heterozygous in the 2 mothers and the grandmother. Mutations in the PHF6 gene are known to cause Börjeson-Forsman-Lehmann syndrome (BFLS). The boys were reexamined after the finding of the mutation, and the phenotype fitted perfectly with BFLS. The mutation found in the PHF6 gene is causative for the intellectual disability in this family. We also conclude that WES of the X chromosome is a powerful tool in families where an X-linked inheritance pattern is suspected.