Novel genes and hormones in salivary glands: from the gene for the submandibular rat 1 protein (SMR1) precursor to receptor sites for SMR1 mature peptides

Submandibular rat 1 protein (SMR1) preprohormone and its maturation peptides constitute the novel characterized submandibular gland (SMG)-specific factors of the cervical sympathetic trunk (CST)-SMG (CST-SMG) axis. As is generally observed for major polypeptide hormones of the endocrine system, SMR1 peptides, including SMR1- imdecapeptide, -hexapeptide and -pentapeptide, are selectively matured from the precursor by cleavage at pairs of basic residues, and differentially accumulated and locally as well as systemically released under multifactorial neuroendocrine control. In turn, the final SMRl mature pentapeptide, at hormonal circulating concentrations, is selectively taken up by peripheral targets through specific binding sites. Localization of the target cells suggests that the SMRl-derived pentapeptide might be involved in modulating mineral ion balance in vivo. Furthermore, associated with male rat specific behavioral characteristics, one can propose that the androgen-regulated SMR1-pentapeptide is a SMG hormonal factor, which under stressful circumstances, is acutely secreted to counterregulate the mineral homeostatic responses to stress. The gene VCSA1, which encodes SMR1, belongs to a new multigene family, essentially expressed in the salivary glands of mammals. This family, whose several members also display putative sites of processing by convertases, has an unusual evolution characterized by multiple gene duplications and an accelerated divergence of coding sequences.Biomedical Reviews 1998; 9: 17-32

Transcriptional Landscape of a blaKPC-2 Plasmid and Response to Imipenem Exposure in Escherichia coli TOP10

The diffusion of KPC-2 carbapenemase is closely related to the spread of Klebsiella pneumoniae of the clonal-group 258 and linked to IncFIIK plasmids. Little is known about the biology of multi-drug resistant plasmids and the reasons of their successful dissemination. Using E. coli TOP10 strain harboring a multi-replicon IncFIIK-IncFIB blaKPC−2-gene carrying plasmid pBIC1a from K. pneumoniae ST-258 clinical isolate BIC-1, we aimed to identify basal gene expression and the effects of imipenem exposure using whole transcriptome approach by RNA sequencing (RNA-Seq). Independently of the antibiotic pressure, most of the plasmid-backbone genes were expressed at low levels. The most expressed pBIC1a genes were involved in antibiotic resistance (blaKPC−2, blaTEM and aph(3′)-I), in plasmid replication and conjugation, or associated to mobile elements. After antibiotic exposure, 34% of E. coli (pBIC1a) genome was differentially expressed. Induction of oxidative stress response was evidenced, with numerous upregulated genes of the SoxRS/OxyR oxydative stress regulons, the Fur regulon (for iron uptake machinery), and IscR regulon (for iron sulfur cluster synthesis). Nine genes carried by pBIC1a were up-regulated, including the murein DD-endopeptidase mepM and the copper resistance operon. Despite the presence of a carbapenemase, we observed a major impact on E. coli (pBIC1a) whole transcriptome after imipenem exposure, but no effect on the level of transcription of antimicrobial resistance genes. We describe adaptive responses of E. coli to imipenem-induced stress, and identified plasmid-encoded genes that could be involved in resistance to stressful environments

Anopheles Gambiae PRS1 Modulates Plasmodium Development at Both Midgut and Salivary Gland Steps

Background: Invasion of the mosquito salivary glands by Plasmodium is a critical step for malaria transmission. From a SAGE analysis, we previously identified several genes whose expression in salivary glands was regulated coincident with sporozoite invasion of salivary glands. To get insights into the consequences of these salivary gland responses, here we have studied one of the genes, PRS1 (Plasmodium responsive salivary 1), whose expression was upregulated in infected glands, using immunolocalization and functional inactivation approaches. Methodology/Principal Findings: PRS1 belongs to a novel insect superfamily of genes encoding proteins with DM9 repeat motifs of uncharacterized function. We show that PRS1 is induced in response to Plasmodium, not only in the salivary glands but also in the midgut, the other epithelial barrier that Plasmodium has to cross to develop in the mosquito. Furthermore, this induction is observed using either the rodent parasite Plasmodium berghei or the human pathogen Plasmodium falciparum. In the midgut, PRS1 overexpression is associated with a relocalization of the protein at the periphery of invaded cells. We also find that sporozoite invasion of salivary gland cells occurs sequentially and induces intra-cellular modifications that include an increase in PRS1 expression and a relocalization of the corresponding protein into vesicle-like structures. Importantly, PRS1 knockdown during the onset of midgut and salivary gland invasion demonstrates that PRS1 acts as an agonist for the development of both parasite species in the two epithelia, highlighting shared vector/parasite interactions in both tissues. Conclusions/Significance: While providing insights into potential functions of DM9 proteins, our results reveal that PRS1 likely contributes to fundamental interactions between Plasmodium and mosquito epithelia, which do not depend on the specific Anopheles/P. falciparum coevolutionary history

Streptococcus agalactiae clones infecting humans were selected and fixed through the extensive use of tetracycline

Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal of the digestive and genitourinary tracts of humans that emerged as the leading cause of bacterial neonatal infections in Europe and North America during the 1960s. Due to the lack of epidemiological and genomic data, the reasons for this emergence are unknown. Here we show by comparative genome analysis and phylogenetic reconstruction of 229 isolates that the rise of human GBS infections corresponds to the selection and worldwide dissemination of only a few clones. The parallel expansion of the clones is preceded by the insertion of integrative and conjugative elements conferring tetracycline resistance (TcR). Thus, we propose that the use of tetracycline from 1948 onwards led in humans to the complete replacement of a diverse GBS population by only few TcR clones particularly well adapted to their host, causing the observed emergence of GBS diseases in neonates. \ua9 2014 Macmillan Publishers Limited. All rights reserved

ST38 E. coli evolution in response to the natural conjugative plasmids carrying the carbapenemase gene blaOXA 48

International audienc

Conserved and specific features of Streptococcus pyogenes and Streptococcus agalactiae transcriptional landscapes

Abstract Background The human pathogen Streptococcus pyogenes, or group A Streptococcus, is responsible for mild infections to life-threatening diseases. To facilitate the characterization of regulatory networks involved in the adaptation of this pathogen to its different environments and their evolution, we have determined the primary transcriptome of a serotype M1 S. pyogenes strain at single-nucleotide resolution and compared it with that of Streptococcus agalactiae, also from the pyogenic group of streptococci. Results By using a combination of differential RNA-sequencing and oriented RNA-sequencing we have identified 892 transcription start sites (TSS) and 885 promoters in the S. pyogenes M1 strain S119. 8.6% of S. pyogenes mRNAs were leaderless, among which 81% were also classified as leaderless in S. agalactiae. 26% of S. pyogenes transcript 5′ untranslated regions (UTRs) were longer than 60 nt. Conservation of long 5′ UTRs with S. agalactiae allowed us to predict new potential regulatory sequences. In addition, based on the mapping of 643 transcript ends in the S. pyogenes strain S119, we constructed an operon map of 401 monocistrons and 349 operons covering 81.5% of the genome. One hundred fifty-six operons and 254 monocistrons retained the same organization, despite multiple genomic reorganizations between S. pyogenes and S. agalactiae. Genomic reorganization was found to more often go along with variable promoter sequences and 5′ UTR lengths. Finally, we identified 117 putative regulatory RNAs, among which nine were regulated in response to magnesium concentration. Conclusions Our data provide insights into transcriptome evolution in pyogenic streptococci and will facilitate the analysis of genetic polymorphisms identified by comparative genomics in S. pyogenes

Evolution of ST38 E. coli following the conjugative acquisition of IncL plasmids carrying blaOXA-48

International audienceCarbapenems are last resort ß lactams used to treat multidrug resistant Gram negative bacteria. However, the increased incidence of carbapenem resistance is threatening their therapeutic efficacy. The emergence of carbapenemase producing E. coli (CPEC) and their dissemination in the community are particularly worrisome. Sequence Type (ST) 38 is the most prevalent ST among CPEC isolated in France and in other European countries, characterized by chromosomal integrations of the blaOXA 48 gene. We are aiming to characterize the benefit of chromosomal integrations and the involved mechanisms. pOXA 48 plasmids were transferred by conjugation into naïve ST38 E. coli strains. Growth curves for fitness cost assessment and 10-day passages without selective pressure for plasmid stability were performed. Transconjugants were evolved for 28 days in the presence of meropenem to look for fitness improvements and potential blaOXA-48 chromosomal integrations. Evolved strains were whole-genome-sequenced.pOXA 48 plasmids were unstable in all tested ST38 E. coli genetic backgrounds. Particularly, growth curve analyses revealed a pOXA-48 associated fitness cost in all tested strains. blaOXA 48 chromosomal integrations were observed during experimental evolution and led to fitness recovery. Alternatively, an increase in both the fitness of evolved strains and in plasmid stability was recurringly associated with mutations in an uncharacterized operon encoding a novel antiplasmid system. How the proteins encoded by this operon contribute to pOXA 48 instability is under study. Altogether our results provide new clues on the emergence of these prevalent carbapenemase producing lineages

Transcriptional Landscape of a bla KPC-2 Plasmid and Response to Imipenem Exposure in Escherichia coli TOP10

International audienceThe diffusion of KPC-2 carbapenemase is closely related to the spread of Klebsiella pneumoniae of the clonal-group 258 and linked to IncFII K plasmids. Little is known about the biology of multi-drug resistant plasmids and the reasons of their successful dissemination. Using E. coli TOP10 strain harboring a multi-replicon IncFII K-IncFIB bla KPC−2-gene carrying plasmid pBIC1a from K. pneumoniae ST-258 clinical isolate BIC-1, we aimed to identify basal gene expression and the effects of imipenem exposure using whole transcriptome approach by RNA sequencing (RNA-Seq). Independently of the antibiotic pressure, most of the plasmid-backbone genes were expressed at low levels. The most expressed pBIC1a genes were involved in antibiotic resistance (bla KPC−2 , bla TEM and aph(3 ′)-I), in plasmid replication and conjugation, or associated to mobile elements. After antibiotic exposure, 34% of E. coli (pBIC1a) genome was differentially expressed. Induction of oxidative stress response was evidenced, with numerous upregulated genes of the SoxRS/OxyR oxydative stress regulons, the Fur regulon (for iron uptake machinery), and IscR regulon (for iron sulfur cluster synthesis). Nine genes carried by pBIC1a were up-regulated, including the murein DD-endopeptidase mepM and the copper resistance operon. Despite the presence of a carbapenemase, we observed a major impact on E. coli (pBIC1a) whole transcriptome after imipenem exposure, but no effect on the level of transcription of antimicrobial resistance genes. We describe adaptive responses of E. coli to imipenem-induced stress, and identified plasmid-encoded genes that could be involved in resistance to stressful environments