Lactase persistence (LP), the dominant Mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen to high frequency in central and northern Europeans in the last 20,000 years. This trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of unfermented milk. Some have argued for the ''culture-historical hypothesis,'' whereby LP alleles were rare until the advent of dairying early in the Neolithic but then rose rapidly in frequency under natural selection. Others favor the ''reverse cause hypothesis,'' whereby dairying was adopted in populations with preadaptive high LP allele frequencies. Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for LP, although it has not been possible to say whether early Neolithic European populations were lactase persistent at appreciable frequencies. We developed a stepwise strategy for obtaining reliable nuclear ancient DNA from ancient skeletons, based on (i) the selection of skeletons from archaeological sites that showed excellent biomolecular preservation, (ii) obtaining highly reproducible human mitochondrial DNA sequences, and (iii) reliable short tandem repeat (STR) genotypes from the same specimens. By applying this experimental strategy, we have obtained high-confidence LP-associated genotypes from eight Neolithic and one Mesolithic human remains, using a range of strict criteria for ancient DNA work. We did not observe the allele most commonly associated with LP in Europeans, thus providing evidence for the culture-historical hypothesis, and indicating that LP was rare in early European farmers.ancient DNA ͉ dairying ͉ selection M ost mammals lose the ability to digest the milk sugar lactose after weaning because of an irreversible reduction in expression of the intestinal enzyme lactase (i.e. lactase phlorizin hydrolase). This pattern is also seen in most humans, but some continue expressing lactase throughout adult life [lactase persistence (LP)]. This dominant Mendelian trait is common in populations of northern and central European descent and shows intermediate frequencies in southern and eastern Europe (1). Africa and the Middle East show a more complex distribution, with pastoralists often having high frequencies of LP, whereas in their nonpastoralist neighbors, it is usually much less common (2). The T allele of C/T polymorphism located 13,910 bp upstream of the lactase (LCT) gene (Ϫ13.910*T) has been shown to associate strongly with LP in Europeans (3), and recent in vitro studies have indicated that it can directly effect LCT gene promoter activity (4). However, different but closely linked polymorphisms associate with LP in most African groups, indicating either that Ϫ13.910*T is not causative of LP and/or that the trait has evolved more than once in humans (2,5,6).It has been suggested that the modern frequency of LP in Europe is the result of a relatively recent and strong selection process (7, 8). Although not...

Protection against antimicrobial peptides (AMPs) often involves the parallel production of multiple, well-characterized resistance determinants. So far, little is known about how these resistance modules interact and how they jointly protect the cell. Here, we studied the interdependence between different layers of the envelope stress response of Bacillus subtilis when challenged with the lipid II cycle-inhibiting AMP bacitracin. The underlying regulatory network orchestrates the production of the ABC transporter BceAB, the UPP phosphatase BcrC and the phage-shock proteins LiaIH. Our systems-level analysis reveals a clear hierarchy, allowing us to discriminate between primary (BceAB) and secondary (BcrC and LiaIH) layers of bacitracin resistance. Deleting the primary layer provokes an enhanced induction of the secondary layer to partially compensate for this loss. This study reveals a direct role of LiaIH in bacitracin resistance, provides novel insights into the feedback regulation of the Lia system, and demonstrates a pivotal role of BcrC in maintaining cell wall homeostasis. The compensatory regulation within the bacitracin network can also explain how gene expression noise propagates between resistance layers. We suggest that this active redundancy in the bacitracin resistance network of B. subtilis is a general principle to be found in many bacterial antibiotic resistance networks.

The field of biology has been revolutionized by the recent advancement of an adaptive bacterial immune system as a universal genome engineering tool. Bacteria and archaea use repetitive genomic elements termed clustered regularly interspaced short palindromic repeats (CRISPR) in combination with an RNA-guided nuclease (CRISPR-associated nuclease: Cas) to target and destroy invading DNA. By choosing the appropriate sequence of the guide RNA, this two-component system can be used to efficiently modify, target, and edit genomic loci of interest in plants, insects, fungi, mammalian cells, and whole organisms. This has opened up new frontiers in genome engineering, including the potential to treat or cure human genetic disorders. Now the potential risks as well as the ethical, social, and legal implications of this powerful new technique move into the limelight.

In all kingdoms of life, cellular replication relies on the presence of nucleosides and nucleotides, the building blocks of nucleic acids and the main source of energy. In bacteria, the availability of metabolites sometimes directly regulates the expression of enzymes and proteins involved in purine salvage, biosynthesis, and uptake through riboswitches. Riboswitches are located in bacterial mRNAs and can control gene expression by conformational changes in response to ligand binding. We have established an inverse reporter gene system in that allows us to monitor riboswitch-controlled gene expression. We used it to investigate the activity of five potential purine riboswitches from in response to different purines and pyrimidines. Furthermore, in vitro studies on the aptamer domains of the riboswitches reveal their variation in guanine binding affinity ranging from namomolar to micromolar. These data do not only provide insight into metabolite sensing but can also aid in engineering artificial cell regulatory systems.

The adaptive bacterial immune system CRISPR-Cas is revolutionizing all fields of life science and has opened up new frontiers toward personalised medicine. Since the elucidation of the molecular mechanism of Cas9 from Streptococcus pyogenes in 2012 and its development as a genomic engineering tool, genetic modifications in more than 40 species have been performed, over 290 patents have been filed worldwide and the first clinical trials using CRISPR-Cas-modified T-cells have recently been started in China and in the US. In this review we summarise current design developments, novel Cas systems and their antagonists, present and potential future applications as well as the ongoing debate on ethical issues, which has arisen through the CRISPR-Cas technology.

Reciprocal gene exchange between cultivated sugar beet and wild beets in seed production areas is probably the reason for the occurence of weed beets in sugar beet production fields. Therefore, when releasing transgenic sugar beet plants into the environment, gene transfer to wild beets (Beta vulgaris ssp. maritima) has to be considered. In this study the transfer of BNYVV‐ (beet necrotic yellow vein virus) resistance and herbicide‐tolerance genes from two transgenic sugar beet lines that were released in field experiments in 1993 and 1994 in Germany to different wild beet accessions was investigated. In order to evaluate the consequences of outcrossing, manual pollinations of emasculated wild beet plants with homozygous transgenic sugar beet plants were performed. In the resulting hybrids the transgenes were stably inherited according to Mendelian law. Gene expression in leaves and roots of the hybrids was in the same range as in the original transgenic sugar beet plants. Moreover, it was found that in one of the wild beet accessions, transfer and expression of the BNYVV resistance gene did considerably increase the level of virus resistance.

Riboswitches are bacterial RNA elements that regulate gene expression in response to metabolite or ion abundance and are considered as potential drug targets. In recent years a number of methods to find non-natural riboswitch ligands have been described. Here we report a high-throughput in vivo screening system that allows identifying OFF-riboswitch modulators in a 384 well bioluminescence assay format. We use a reverse reporter gene setup in Bacillus subtilis, consisting of a primary screening assay, a secondary assay as well as counter assays to detect compounds in a library of 1,280 molecules that act on the guanine-responsive xpt riboswitch from B. anthracis. With this in vivo high-throughput approach we identified several hit compounds and could validate the impact of one of them on riboswitch-mediated gene regulation, albeit this might not be due to direct binding to the riboswitch. However, our data demonstrate the capability of our screening assay for bigger high-throughput screening campaigns. Furthermore, the screening system described here can not only be generally employed to detect non-natural ligands or compounds influencing riboswitches acting as genetic OFF switches, but it can also be used to investigate natural ligands of orphan OFF-riboswitches.

Der Forschungsbereich der Biologie erfährt zurzeit eine Revolution durch die Weiterentwicklung eines bakteriellen adaptiven Immunsystems zu einem universellen Werkzeug für die Gentechnik. Bakterien und Archaeen benutzen repetitive Teile des Genoms, sogenannte “clustered regularly interspaced short palindromic repeats” (CRISPR), in Kombination mit einer RNA‐abhängigen Nuklease (CRISPR‐associated nuclease=Cas), um in Zellen eindringende DNA zu erkennen und zu zerstören. Indem man die Sequenz der Leit‐RNA (guide‐RNA) passend wählt, kann dieses Zweikomponentensystem verwendet werden, um auf effiziente Weise Genloci in Pflanzen, Insekten, Pilzen, Säugetierzellen und ganzen Organismen zu erreichen oder zu modifizieren. Dies eröffnet ungeahnte Möglichkeiten in der Gentechnik bis hin zur Behandlung oder Heilung von menschlichen Erbkrankheiten. Jetzt rücken die potentiellen Risiken und ethische, soziale und juristische Fragestellungen im Zusammenhang mit dieser mächtigen neuen Technik ins Rampenlicht.