The nucleotide sequence of comC, the gene encoding the 17-residue competence-stimulating peptide (CSP) of Streptococcus pneumoniae (L. S. Håvarstein, G. Coomaraswamy, and D. A. Morrison, Proc. Natl. Acad. Sci. USA 92:11140-11144, 1995) was determined with 42 encapsulated strains of different serotypes. A new allele, comC2, was found in 13 strains, including the type 3 Avery strain, A66, while all others carried a gene (now termed comC1) identical to that originally described for strain Rx1. The predicted mature product of comC2 is also a heptadecapeptide but differs from that of comC1 at eight residues. Both CSP-1 and CSP-2 synthetic peptides were used to induce competence in the 42 strains; 48% of the strains became competent after the addition of the synthetic peptide, whereas none were transformable without the added peptides.Genetic transformation not only is a valuable tool for molecular genetic analysis of Streptococcus pneumoniae (pneumococcus) but also appears to play a significant role in the evolution of this species, as in the assembly of mosaic antibiotic resistance genes containing blocks of information from other bacteria (6, 17) and in mediating a rapid mixing of alleles among natural populations (4). Yet, although transformation has long been described as a characteristic of the pneumococci, as a practical matter most studies involving this process have focused on a few laboratory strains, mainly descended from a single unencapsulated subclone (R36A) (2), for which optimal media and protocols were developed. Indeed, it has never been established just what proportion of pneumococcal isolates is transformable. This fraction has been difficult to assess, both because the pneumococcal capsule reduces or abolishes competence for genetic transformation (3,5,7,14,20,25) and because the optimal conditions for competence vary between strains.Competence for transformation in pneumococcus is not constitutive but is regulated by a quorum-sensing pheromone signal (23, 24). It was previously shown that culture supernatants from one strain, Rx1 (16), activate some other strains to competence and can induce competence in some encapsulated strains but not in others, including the type 3 strain A66 (25), even though an unencapsulated derivative of that strain is transformable (22). Following the recent identification of a small peptide from strain Rx1 with competence-stimulating activity (a competence-stimulating peptide [CSP]) (12), we reinvestigated the paradoxical behavior of A66, as a pure pheromone might be more effective than the crude culture supernatants used previously, but the results were still negative. We now trace the unresponsive character of strain A66 to the competence pheromone regulatory circuit itself and show that it reflects allelic variation of the pheromone gene in different isolates of this species.Failure of A66 to respond to the CSP of Rx1. Strain Rx1 is descended from R36A, an unencapsulated transformable derivative of D39S, a type 2 clinical isolate that was employed in early studies o...

A survey of antimicrobial resistance in Streptococcus pyogenes, performed within the framework of a national surveillance program, has revealed a dramatic increase in resistance of S. pyogenes to erythromycin in most areas of Italy. In virtually all the centers that provided data for 3 consecutive years, the incidence of erythromycin-resistant strains increased twofold to 20-fold from 1993 to 1995 and was greater than 30% in five of the 14 centers participating in the study. The clonality of erythromycin-resistant isolates was studied in 15 strains isolated from different patients at the Institute of Microbiology of Verona University (Verona). The features of the Verona isolates and the substantially different rates of erythromycin and clindamycin resistance observed in most centers suggest that the spread of different resistance genes in multiple clones might be occurring throughout the country.

The subcortical maternal complex (SCMC) is a multiprotein complex uniquely expressed in mammalian oocytes and early embryos, essential for zygote progression beyond the first embryonic cell divisions. Similiar to other factors encoded by maternal effect genes, the physiological role of SCMC remains unclear, although recent evidence has provided important molecular insights into different possible functions. Its potential involvement in human fertility is attracting increasing attention; however, the complete story is far from being told. The present mini review provides an overview of recent findings related to the SCMC and discusses its potential physiological role/s with the aim of inspiring new directions for future research.

BackgroundThe sub-cortical maternal complex (SCMC), located in the subcortex of mouse oocytes and preimplantation embryos, is composed of at least four proteins encoded by maternal effect genes: OOEP, NLRP5/MATER, TLE6 and KHDC3/FILIA. The SCMC assembles during oocyte growth and was seen to be essential for murine zygote progression beyond the first embryonic cell divisions; although roles in chromatin reprogramming and embryonic genome activation were hypothesized, the full range of functions of the complex in preimplantation development remains largely unknown.ResultsHere we report the expression of the SCMC genes in ovine oocytes and pre-implantation embryos, describing for the first time its expression in a large mammalian species.We report sheep-specific patterns of expression and a relationship with the oocyte developmental potential in terms of delayed degradation of maternal SCMC transcripts in pre-implantation embryos derived from developmentally incompetent oocytes.In addition, by determining OOEP full length cDNA by Rapid Amplification of cDNA Ends (RACE) we identified two different transcript variants (OOEP1 and OOEP2), both expressed in oocytes and early embryos, but with different somatic tissue distributions.In silico translation showed that 140 aminoacid peptide OOEP1 shares an identity with orthologous proteins ranging from 95% with the bovine to 45% with mouse. Conversely, OOEP2 contains a premature termination codon, thus representing an alternative noncoding transcript and supporting the existence of aberrant splicing during ovine oogenesis.ConclusionsThese findings confirm the existence of the SCMC in sheep and its key role for the oocyte developmental potential, deepening our understanding on the molecular differences underlying cytoplasmic vs nuclear maturation of the oocytes.Describing differences and overlaps in transcriptome composition between model organisms advance our comprehension of the diversity/uniformity between mammalian species during early embryonic development and provide information on genes that play important regulatory roles in fertility in nonmurine models, including the human.Electronic supplementary materialThe online version of this article (doi:10.1186/s12861-014-0040-y) contains supplementary material, which is available to authorized users.

BackgroundDNA methylation plays a vital role in the cell, but loss-of-function mutations of the maintenance methyltransferase DNMT1 in normal human cells are lethal, precluding target identification, and existing hypomorphic lines are tumour cells. We generated instead a hypomorphic series in normal hTERT-immortalised fibroblasts using stably integrated short hairpin RNA.ResultsApproximately two-thirds of sites showed demethylation as expected, with one-third showing hypermethylation, and targets were shared between the three independently derived lines. Enrichment analysis indicated significant losses at promoters and gene bodies with four gene classes most affected: (1) protocadherins, which are key to neural cell identity; (2) genes involved in fat homoeostasis/body mass determination; (3) olfactory receptors and (4) cancer/testis antigen (CTA) genes. Overall effects on transcription were relatively small in these fibroblasts, but CTA genes showed robust derepression. Comparison with siRNA-treated cells indicated that shRNA lines show substantial remethylation over time. Regions showing persistent hypomethylation in the shRNA lines were associated with polycomb repression and were derepressed on addition of an EZH2 inhibitor. Persistent hypermethylation in shRNA lines was, in contrast, associated with poised promoters.ConclusionsWe have assessed for the first time the effects of chronic depletion of DNMT1 in an untransformed, differentiated human cell type. Our results suggest polycomb marking blocks remethylation and indicate the sensitivity of key neural, adipose and cancer-associated genes to loss of maintenance methylation activity.Electronic supplementary materialThe online version of this article (10.1186/s13072-018-0182-4) contains supplementary material, which is available to authorized users.