Daniel Wüthrich

Proteome remodelling during development from blood to insect-form Trypanosoma brucei quantified by SILAC and mass spectrometry

BackgroundTrypanosoma brucei is the causative agent of human African sleeping sickness and Nagana in cattle. In addition to being an important pathogen T. brucei has developed into a model system in cell biology.ResultsUsing Stable Isotope Labelling of Amino acids in Cell culture (SILAC) in combination with mass spectrometry we determined the abundance of >1600 proteins in the long slender (LS), short stumpy (SS) mammalian bloodstream form stages relative to the procyclic (PC) insect-form stage. In total we identified 2645 proteins, corresponding to ~30% of the total proteome and for the first time present a comprehensive overview of relative protein levels in three life stages of the parasite.ConclusionsWe can show the extent of pre-adaptation in the SS cells, especially at the level of the mitochondrial proteome. The comparison to a previously published report on monomorphic in vitro grown bloodstream and procyclic T. brucei indicates a loss of stringent regulation particularly of mitochondrial proteins in these cells when compared to the pleomorphic in vivo situation. In order to better understand the different levels of gene expression regulation in this organism we compared mRNA steady state abundance with the relative protein abundance-changes and detected moderate but significant correlation indicating that trypanosomes possess a significant repertoire of translational and posttranslational mechanisms to regulate protein abundance.

Neurotropic Astrovirus in Cattle with Nonsuppurative Encephalitis in Europe

ABSTRACT Encephalitis is a frequently diagnosed condition in cattle with neurological diseases. Many affected animals present with a nonsuppurative inflammatory reaction pattern in the brain. While this pattern supports a viral etiology, the causative pathogen remains unknown in a large proportion of cases. Using viral metagenomics, we identified an astrovirus (bovine astrovirus [BoAstV]-CH13) in the brain of a cow with nonsuppurative encephalitis. Additionally, BoAstV RNA was detected with reverse transcription-PCR and in situ hybridization in about one fourth (5/22 animals) of cattle with nonsuppurative encephalitis of unknown etiology. Viral RNA was found primarily in neurons and at the site of pathology. These findings support the notion that BoAstV infection is a common cause of encephalitis in cattle. Phylogenetically, BoAstV-CH13 was closely related to rare astrovirus isolates from encephalitis cases in animals and a human patient. Future research needs to be directed toward the pathogenic mechanisms, epidemiology, and potential cross-species transmission of these neurotropic astroviruses.

Identification of a second encephalitis-associated astrovirus in cattle

Dear Editor, Human astroviruses are of particular importance as one of the most common pathogens that cause juvenile gastroenteritis. In recent years, several astrovirus isolates were identified as potential causes of encephalitis in immunocompromised human patients. These discoveries were paralleled by the description of phylogenetically closely related bovine astrovirus isolates (BoAstV) from the nervous tissue of cattle with encephalitis of unknown etiology in the USA (BoAstV NeuroS1) and by our laboratory in Switzerland (BoAstV-CH13). BoAstV-CH13 was retrospectively found in approximately one-quarter (5/22) of the cattle with etiologically unresolved non-suppurative encephalitis in Switzerland; however, most of these cases (17/22) were unrelated to BoAstV-CH13. Here, we report the identification of yet another neuroinvasive astrovirus in this set of cattle with non-suppurative encephalitis, which has less than 65% genetic similarity to currently known astrovirus isolates. In 2006, a 4-year-old Braunvieh cow (case ID 42535) was notified as a clinical bovine spongiform encephalopathy (BSE) suspect to the Swiss authorities. Precise information about the clinical presentation was not available, but the spectrum of signs in BSE-suspect animals usually involves changes in behavior and temperament, hyper-reactivity, and incoordination. Post mortem BSE testing was negative, and histopathological examination led to the diagnosis of severe non-suppurative meningo-encephalomyelitis (Figure 1A). This inflammatory pattern strongly suggested that the animal had a viral infection, but further etiologic investigations were not undertaken. The animal was included in our research on BoAstV infection and encephalitis and was further investigated by unbiased next-generation RNA sequencing (NGS) and a bioinformatics pathogen discovery pipeline. Illumina sequencing of frozen brain tissue RNA extracts (medulla oblongata) from animal 42 535 resulted in 21 443 420 read pairs. After in-silico subtraction of reads that aligned to the bovine reference genome and de novo assembly of the remaining reads, we identified four contiguous sequences (contigs) of 792, 1010, 1103, and 3170 nucleotides that matched with the highest amino acid sequence similarity (64%–83%) to different proteins of a sheep astrovirus isolate entry (accession number NC_002469.1) of the National Center for Biotechnology Information database. Gaps between the contigs were bridged by RT-PCR followed by Sanger sequencing. The 59 and 39 ends of the RNA molecule were determined by rapid amplification of cDNA ends (Supplementary Methods, Supplementary Table S1). This resulted in a sequence of 6287 nucleotides that revealed features of an astrovirus genome with short 59 and 39 untranslated regions, three partially overlapping open reading frames (ORF1a, ORF1b, and ORF2), and a poly-A tail (Figure 1B). RT-PCR targeting a 388-bp fragment in ORF1a confirmed the presence of the viral RNA in frozen tissue samples of the medulla oblongata, cerebellar cortex, midbrain, and cerebral cortex (Supplementary Figure S1). Taken together, these data indicate the presence of a previously unknown astrovirus that we termed BoAstV-CH15 (GenBank accession number KT956903). Other pathogens were not detected using our pipeline. Full genome phylogenetic comparison placed the BoAstV-CH15 in the same cluster of previously described neurotropic astroviruses (Figure 1C, HMO clade) and distant from bovine and human isolates that were derived from feces specimens (Figure 1C, classical clades). BoAstV-CH15 rooted from the same branch as an ovine astrovirus (OvAstV), which was isolated from the feces of a sheep with diarrhea. The same topology was obtained in a maximum-likelihood tree that was based on the full-length capsid protein amino acid sequences (Supplementary Figure S2). A sliding-window, pairwise comparison plot of full genome sequences confirmed the relationship between BoAstV-CH15 and the OvAstV and showed less identity of BoAstVCH15 with BoAstV-CH13 and HuAstV-PS, a human encephalitis isolate, at most positions (Figure 1D). To assess whether other cases of cattle encephalitis are associated with the presence of the newly identified astrovirus, we tested the entire set of frozen tissue samples (n 5 22) from the retrospective study mentioned above using the BoAstV-CH15 RT-PCR protocol. Besides case 42 535, one additional encephalitis case was reactive and showed the specific 388-bp amplicon. This animal was an unrelated neurologically diseased 7-year-old cow that was diagnosed with severe non-suppurative poliomeningoencephalitis and ganglioneuritis in 2007 (ID 42799; Figure 1A). This finding was unexpected in this particular animal because it was previously classified as BoAstV-CH13positive based on RT-PCR results and ISH experiments. However, as the BoAstV-CH15 RT-PCR protocol does not detect BoAstV-CH13 (Seuberlich T, 2015, unpubl. data), these conflicting results could be explained by the presence of either a different type of astrovirus or by

Global phylogenomic analysis of nonencapsulated streptococcus pneumoniae reveals a deep-branching classic lineage that is distinct from multiple sporadic lineages

The surrounding capsule of Streptococcus pneumoniae has been identified as a major virulence factor and is targeted by pneumococcal conjugate vaccines (PCV). However, nonencapsulated S. pneumoniae (non-Ec-Sp) have also been isolated globally, mainly in carriage studies. It is unknown if non-Ec-Sp evolve sporadically, if they have high antibiotic nonsusceptiblity rates and a unique, specific gene content. Here, whole-genome sequencing of 131 non-Ec-Sp isolates sourced from 17 different locations around the world was performed. Results revealed a deep-branching classic lineage that is distinct from multiple sporadic lineages. The sporadic lineages clustered with a previously sequenced, global collection of encapsulated S. pneumoniae (Ec-Sp) isolates while the classic lineage is comprised mainly of the frequently identified multilocus sequences types (STs) ST344 (n = 39) and ST448 (n = 40). All ST344 and nine ST448 isolates had high nonsusceptiblity rates to β-lactams and other antimicrobials. Analysis of the accessory genome reveals that the classic non-Ec-Sp contained an increased number of mobile elements, than Ec-Sp and sporadic non-Ec-Sp. Performing adherence assays to human epithelial cells for selected classic and sporadic non-Ec-Sp revealed that the presence of a integrative conjugative element (ICE) results in increased adherence to human epithelial cells (P = 0.005). In contrast, sporadic non-Ec-Sp lacking the ICE had greater growth in vitro possibly resulting in improved fitness. In conclusion, non-Ec-Sp isolates from the classic lineage have evolved separately. They have spread globally, are well adapted to nasopharyngeal carriage and are able to coexist with Ec-Sp. Due to continued use of PCV, non-Ec-Sp may become more prevalent.

A point mutation in cpsE renders Streptococcus pneumoniae nonencapsulated and enhances its growth, adherence and competence

BackgroundThe polysaccharide capsule is a major virulence factor of the important human pathogen Streptococcus pneumoniae. However, S. pneumoniae strains lacking capsule do occur.ResultsHere, we report a nasopharyngeal isolate of Streptococcus pneumoniae composed of a mixture of two phenotypes; one encapsulated (serotype 18C) and the other nonencapsulated, determined by serotyping, electron microscopy and fluorescence isothiocyanate dextran exclusion assay.By whole genome sequencing, we demonstrated that the phenotypes differ by a single nucleotide base pair in capsular gene cpsE (C to G change at gene position 1135) predicted to result in amino acid change from arginine to glycine at position 379, located in the cytoplasmic, enzymatically active, region of this transmembrane protein. This SNP is responsible for loss of capsule production as the phenotype is transferred with the capsule operon. The nonencapsulated variant is superior in growth in vitro and is also 117-fold more adherent to and more invasive into Detroit 562 human epithelial cells than the encapsulated variant.Expression of six competence pathway genes and one competence-associated gene was 11 to 34-fold higher in the nonencapsulated variant than the encapsulated and transformation frequency was 3.7-fold greater.ConclusionsWe identified a new single point mutation in capsule gene cpsE of a clinical S. pneumoniae serotype 18C isolate sufficient to cause loss of capsule expression resulting in the co-existence of the encapsulated and nonencapsulated phenotype. The mutation caused phenotypic changes in growth, adherence to epithelial cells and transformability. Mutation in capsule gene cpsE may be a way for S. pneumoniae to lose its capsule and increase its colonization potential.

Exploring the virome of cattle with non-suppurative encephalitis of unknown etiology by metagenomics

Non-suppurative encephalitis is one of the most frequent pathological diagnosis in cattle with neurological disease, but there is a gap in the knowledge on disease-associated pathogens. In order to identify viruses that are associated with non-suppurative encephalitis in cattle, we used a viral metagenomics approach on a sample set of 16 neurologically-diseased cows. We detected six virus candidates: parainfluenza virus 5 (PIV-5), bovine astrovirus CH13/NeuroS1 (BoAstV-CH13/NeuroS1), bovine polyomavirus 2 (BPyV-2 SF), ovine herpesvirus 2 (OvHV-2), bovine herpesvirus 6 (BHV-6) and a novel bovine betaretrovirus termed BoRV-CH15. In a case-control study using PCR, BoAstV-CH13 (p=0.046), BoPV-2 SF (p=0.005) and BoHV-6 (p=4.3E-05) were statistically associated with the disease. These data expand our knowledge on encephalitis-associated pathogens in cattle and point to the value of NGS in resolving complex infection scenarios in a clinical disease setting.

Indication of Cross-Species Transmission of Astrovirus Associated with Encephalitis in Sheep and Cattle

We report the identification of a neurotropic astrovirus associated with encephalitis in a sheep. This virus is genetically almost identical to an astrovirus recently described in neurologically diseased cattle. The similarity indicates that astroviruses of the same genotype may cause encephalitis in different species.

Draft Genome Sequences of Clostridium tyrobutyricum Strains FAM22552 and FAM22553, Isolated from Swiss Semihard Red-Smear Cheese

ABSTRACT Clostridium tyrobutyricum is the main microorganism responsible for late blowing defect in cheeses. Here, we present the draft genome sequences of two C. tyrobutyricum strains isolated from a Swiss semihard red-smear cheese. The two draft genomes comprise 3.05 and 3.08 Mbp and contain 3,030 and 3,089 putative coding sequences, respectively.

The Histidine Decarboxylase Gene Cluster of Lactobacillus parabuchneri Was Gained by Horizontal Gene Transfer and Is Mobile within the Species

Histamine in food can cause intolerance reactions in consumers. Lactobacillus parabuchneri (L. parabuchneri) is one of the major causes of elevated histamine levels in cheese. Despite its significant economic impact and negative influence on human health, no genomic study has been published so far. We sequenced and analyzed 18 L. parabuchneri strains of which 12 were histamine positive and 6 were histamine negative. We determined the complete genome of the histamine positive strain FAM21731 with PacBio as well as Illumina and the genomes of the remaining 17 strains using the Illumina technology. We developed the synteny aware ortholog finding algorithm SynOrf to compare the genomes and we show that the histidine decarboxylase (HDC) gene cluster is located in a genomic island. It is very likely that the HDC gene cluster was transferred from other lactobacilli, as it is highly conserved within several lactobacilli species. Furthermore, we have evidence that the HDC gene cluster was transferred within the L. parabuchneri species.

Transcriptional Regulation of Cysteine and Methionine Metabolism in Lactobacillus paracasei FAM18149.

Lactobacillus paracasei is common in the non-starter lactic acid bacteria (LAB) community of raw milk cheeses. This species can significantly contribute to flavor formation through amino acid metabolism. In this study, the DNA and RNA of L. paracasei FAM18149 were sequenced using next-generation sequencing technologies to reconstruct the metabolism of the sulfur-containing amino acids cysteine and methionine. Twenty-three genes were found to be involved in cysteine biosynthesis, the conversion of cysteine to methionine and vice versa, the S-adenosylmethionine recycling pathway, and the transport of sulfur-containing amino acids. Additionally, six methionine-specific T-boxes and one cysteine-specific T-box were found. Five of these were located upstream of genes encoding transporter functions. RNA-seq analysis and reverse-transcription quantitative polymerase reaction assays showed that expression of genes located downstream of these T-boxes was affected by the absence of either cysteine or methionine. Remarkably, the cysK2-ctl1-cysE2 operon, which is associated with te methionine-to-cysteine conversion and is upregulated in the absence of cysteine, showed high read coverage in the 5′-untranslated region and an antisense-RNA in the 3′-untranslated region. This indicates that this operon is regulated by the combination of cis- and antisense-mediated regulation mechanisms. The results of this study may help in the selection of L. paracasei strains to control sulfuric flavor formation in cheese.