Genome Sequencing of a Historic Staphylococcus aureus Collection Reveals New Enterotoxin Genes and Sheds Light on the Evolution and Genomic Organization of This Key Virulence Gene Family.

We take advantage of a historic collection of 133 Staphylococcus aureus strains accessioned between 1924 and 2016, whose genomes have been long-read sequenced as part of a major National Collection of Type Cultures (NCTC) initiative, to conduct a gene family-wide computational analysis of enterotoxin genes. We identify two novel staphylococcal enterotoxin (pseudo)genes (sel29p and sel30), the former of which has not been observed in any contemporary strain to date. We provide further information on five additional enterotoxin genes or gene variants that either have recently entered the literature or for which the nomenclature or description is currently unclear (selz, sel26, sel27, sel28, and ses-2p). An examination of over 11,000 RefSeq genomes in search of wider support for these seven (pseudo)genes led to the identification of an additional three novel enterotoxin gene family members (sel31, sel32, and sel33) plus two new variants (seh-2p and ses-3p). We cast light on the genomic distribution of the enterotoxin genes, further defining their arrangement in gene clusters. Finally, we show that cooccurrence of enterotoxin genes is prevalent, with individual NCTC strains possessing as many as 18 enterotoxin genes and pseudogenes, and that clonal complex membership rather than time of isolation is the key factor in determining enterotoxin load.IMPORTANCEStaphylococcus aureus strains pose a significant health risk to both human and animal populations. Key among this species' virulence factors is the staphylococcal enterotoxin gene family. Certain enterotoxin forms can induce a potentially life-threatening immune response, while others are implicated in less fatal though often severe conditions such as food poisoning. Genetic characterization of staphylococcal enterotoxin gene family members has steadily accumulated over recent decades, with over 20 genes now established in the literature. Despite the current wealth of knowledge on this important gene family, questions remain about the presence of additional enterotoxin genes and the genomic composition of family members. This study further expands knowledge of the staphylococcal enterotoxins while shedding light on their evolution over the last century

How Young Mothers Rely on Kin Networks and Formal Childcare to Avoid Becoming NEET in the Netherlands

Motherhood is often cited as one of the main reasons for young women to become NEET (not in employment, education, or training). Given the potential long-term negative implications of NEET status, it is important to understand which types of resources can help young mothers to avoid becoming NEET around childbirth. In this paper we investigate how the chances of young mothers to become and stay NEET around the time of first birth are related to the availability and characteristics of members of their social support network, especially partners and grandparents, to assist in childcare. In addition, we consider the local availability of formal childcare. We use population-wide register data from the Netherlands and estimate discrete-time eventhistory models. Our results show that young mothers who are cohabitating or married are less likely to become NEETs than single mothers. We also show that economic activity and relative wage of both young mothers and their partners decreases the likelihood to become NEET and to exit NEET. With respect to the grandparents, we find that having more grandparents live in the immediate vicinity is associated with a lower likelihood to become NEET and a higher likelihood to exit NEET. Furthermore, we find that young mothers with economically inactive parents are more likely to become and less likely to exit NEET. Lastly, we find evidence for crowding-out of informal and formal childcare. Formal and informal childcare sources interact in such a way that the role of either becomes less important as more of the other is available

On the structure of eigenfunctions corresponding to embedded eigenvalues of locally perturbed periodic graph operators

The article is devoted to the following question. Consider a periodic self-adjoint difference (differential) operator on a graph (quantum graph) G with a co-compact free action of the integer lattice Z^n. It is known that a local perturbation of the operator might embed an eigenvalue into the continuous spectrum (a feature uncommon for periodic elliptic operators of second order). In all known constructions of such examples, the corresponding eigenfunction is compactly supported. One wonders whether this must always be the case. The paper answers this question affirmatively. What is more surprising, one can estimate that the eigenmode must be localized not far away from the perturbation (in a neighborhood of the perturbation's support, the width of the neighborhood determined by the unperturbed operator only). The validity of this result requires the condition of irreducibility of the Fermi (Floquet) surface of the periodic operator, which is expected to be satisfied for instance for periodic Schroedinger operators.Comment: Submitted for publicatio

Toric complexes and Artin kernels

A simplicial complex L on n vertices determines a subcomplex T_L of the n-torus, with fundamental group the right-angled Artin group G_L. Given an epimorphism \chi\colon G_L\to \Z, let T_L^\chi be the corresponding cover, with fundamental group the Artin kernel N_\chi. We compute the cohomology jumping loci of the toric complex T_L, as well as the homology groups of T_L^\chi with coefficients in a field \k, viewed as modules over the group algebra \k\Z. We give combinatorial conditions for H_{\le r}(T_L^\chi;\k) to have trivial \Z-action, allowing us to compute the truncated cohomology ring, H^{\le r}(T_L^\chi;\k). We also determine several Lie algebras associated to Artin kernels, under certain triviality assumptions on the monodromy \Z-action, and establish the 1-formality of these (not necessarily finitely presentable) groups.Comment: 34 page