Microbial genomes

Microbial genome sequencing is driven by the need to understand and control pathogens and to exploit extremophiles and their enzymes in bioremediation and industry. It is hard for the traditional bacteriologist to grasp the scale and pace of the venture. Around two dozen microbial genomes have now been completed and, within a decade, genomes from every significant species of bacterial pathogen of humans, animals and plants will have been sequenced. Indeed, we will often have more than one sequence from a species or genus--for example, we already have sequences from two strains of Helicobacter pylori, from two strains of Mycobacterium tuberculosis and from three species of Pyrococcus. However, genome sequencing risks becoming expensive molecular stamp-collecting without the tools to mine the data and fuel hypothesis-driven laboratory-based research. Bioinformatics, twinned with the new experimental approaches forming functional genomics', provides some of the needed tools. Nonetheless, there will be an increasing need for us to explore the detailed implications of genomic findings. Microbial genome sequencing thus represents not a threat, but an exciting opportunity for molecular microbiologists.     

The receptor-like protein tyrosine phosphatase HPTP alpha has two active catalytic domains with distinct substrate specificities.

Cloning and expression of the homologous domains of the receptor-like tyrosine phosphatase HPTP alpha shows that both domain 1 (D1) and domain 2 (D2) are enzymatically active. The two domains display different substrate specificities with D1 preferentially dephosphorylating MBP approximately RR-src greater than PNPP while D2 favours PNPP much much greater than RR-src and is inactive towards MBP. Each domain has lower activity than an expressed protein containing both domains. Analysis of chimaeric D1/2 proteins suggests that no particular region of D2 is responsible for the low activity of D2 on RR-src and that the specificity differences of D1 and D2 reflect overall sequence dissimilarities. Activities of D1 and D2 are inhibited by zinc, vanadate and EDTA and differentially susceptible to inhibition by heparin and poly(Glu4:Tyr1). Unusually, the activity of the protein containing both domains is stimulated by these polyanions. Regions amino-terminal to each domain are important for catalysis since deletion of these sequences abolishes phosphatase activity. Activity of the double domain polypeptide was also lost upon deletion of the sequence amino-terminal to D1, indicating that inactivation of D1 may suppress D2 activity. Differences in substrate specificity and responses to effectors and the interdependence between the two domains are likely important properties in the function of this PTPase in signal transduction.     

Genome sequences of three Acinetobacter baumannii strains assigned to the multilocus sequence typing genotypes ST2, ST25, and ST78

Acinetobacter baumannii is an emerging opportunistic gram-negative pathogen responsible for hospital-acquired infections. A. baumannii epidemics described in Europe and worldwide were caused by a limited number of genotypic clusters of multidrug-resistant strains. Here, we report the availability of draft genome sequences for three multidrug-resistant A. baumannii strains assigned to multilocus sequence typing genotypes ST2, ST25, and ST78 that were more frequently isolated during outbreaks occurred in Greece, Italy, Lebanon, and Turkey.     

Receptor-like protein-tyrosine phosphatase α enhances cell surface expression of neural adhesion molecule NB-3

Neural adhesion molecule NB-3 plays an important role in the apical dendrite development of layer V pyramidal neurons in the visual cortex, and receptor-like protein-tyrosine phosphatase α (PTPα) mediates NB-3 signaling in this process. Here we investigated the role of PTPα in regulating cell surface expression of NB-3. We found that cortical neurons from PTPα knock-out mice exhibited a lower level of NB-3 at the cell surface. When expressed in COS1 cells, NB-3 was enriched in the Golgi apparatus with a low level of cell surface expression. However, co-expression of PTPα increased the cell surface distribution of NB-3. Further analysis showed that PTPα facilitated Golgi exit of NB-3 and stabilized NB-3 protein at the cell surface by preventing its release from the plasma membrane. The extracellular region of PTPα but not its catalytic activity is necessary for its effect on NB-3 expression. Thus, the PTPα-mediated increase of NB-3 level at the cell surface represents a novel function of PTPα in NB-3 signaling in neural development.     

Differences in the Faecal Microbiome in Schistosoma haematobium Infected Children vs. Uninfected Children

BackgroundSeveral infectious diseases and therapeutic interventions cause gut microbe dysbiosis and associated pathology. We characterised the gut microbiome of children exposed to the helminth Schistosoma haematobium pre- and post-treatment with the drug praziquantel (PZQ), with the aim to compare the gut microbiome structure (abundance and diversity) in schistosome infected vs. uninfected children.MethodsStool DNA from 139 children aged six months to 13 years old; with S. haematobium infection prevalence of 27.34% was extracted at baseline. 12 weeks following antihelminthic treatment with praziqunatel, stool DNA was collected from 62 of the 139 children. The 16S rRNA genes were sequenced from the baseline and post-treatment samples and the sequence data, clustered into operational taxonomic units (OTUs). The OTU data were analysed using multivariate analyses and paired T- test.ResultsPre-treatment, the most abundant phyla were Bacteroidetes, followed by Firmicutes and Proteobacteria respectively. The relative abundance of taxa among bacterial classes showed limited variation by age group or sex and the bacterial communities had similar overall compositions. Although there were no overall differences in the microbiome structure across the whole age range, the abundance of 21 OTUs varied significantly with age (FDR<0.05). Some OTUs including Veillonella, Streptococcus, Bacteroides and Helicobacter were more abundant in children ≤ 1 year old compared to older children. Furthermore, the gut microbiome differed in schistosome infected vs. uninfected children with 27 OTU occurring in infected but not uninfected children, for 5 of these all Prevotella, the difference was statistically significant (p <0.05) with FDR <0.05. PZQ treatment did not alter the microbiome structure in infected or uninfected children from that observed at baseline.ConclusionsThere are significant differences in the gut microbiome structure of infected vs. uninfected children and the differences were refractory to PZQ treatment.     

The HtrA family of serine proteases

HtrA, also known as DegP and probably identical to the Do protease, is a heat shock-induced serine protease that is active in the periplasm of Escherichia coli . Homologues of HtrA have been described in a wide range of bacteria and in eukaryotes. Its chief role is to degrade misfolded proteins in the periplasm. Substrate recognition probably involves the recently described PDZ domains in the C-terminal half of HtrA and, we suspect, has much in common with the substrate recognition system of the tail-specific protease, Prc (which also possesses a PDZ domain). The expression of htrA is regulated by a complex set of signal transduction pathways, which includes an alternative sigma factor, RpoE, an anti-sigma factor, RseA, a two-component regulatory system, CpxRA, and two phosphoprotein phosphatases, PrpA and PrpB. Mutations in the htrA genes of Salmonella , Brucella and Yersinia cause decreased survival in mice and/or macrophages, and htrA mutants can act as vaccines, as cloning hosts and as carriers of heterologous antigens.