Functional redundancy of seasonal vitamin B12 biosynthesis pathways in coastal marine microbial communities

Vitamin B₁₂ (cobalamin) is a major cofactor required by most marine microbes, but only produced by a few prokaryotes in the ocean, which is globally B₁₂-depleted. Despite the ecological importance of B₁₂, the seasonality of B₁₂ metabolisms and the organisms involved in its synthesis in the ocean remain poorly known. Here we use metagenomics to assess the monthly dynamics of B₁₂-related pathways and the functional diversity of associated microbial communities in the coastal NW Mediterranean Sea over 7 years. We show that genes related to potential B₁₂ metabolisms were characterized by an annual succession of different organisms carrying distinct production pathways. During the most productive winter months, archaea (Nitrosopumilus and Nitrosopelagicus) were the main contributors to B₁₂ synthesis potential through the anaerobic pathway (cbi genes). In turn, Alphaproteobacteria (HIMB11, UBA8309, Puniceispirillum) contributed to B₁₂ synthesis potential in spring and summer through the aerobic pathway (cob genes). Cyanobacteria could produce pseudo-cobalamin from spring to autumn. Finally, we show that during years with environmental perturbations, the organisms usually carrying B₁₂ synthesis genes were replaced by others having the same gene, thus maintaining the potential for B₁₂ production. Such ecological insurance could contribute to the long-term functional resilience of marine microbial communities exposed to contrasting inter-annual environmental conditions.     

Phylogenetics and predictive distribution modeling provide insights into the geographic divergence of Eriosyce subgen. Neoporteria (Cactaceae)

The classification of Eriosyce subgenus Neoporteria (??subsection?? in the sense of Kattermann) and the role of allopatry/sympatry in the diversification of the group were studied by use of cladistic and predictive distribution modeling methods. We reconstructed the phylogenetic relationships of subgenus Neoporteria by analyzing 38 morphological characters and DNA sequences from two chloroplast regions of 21 taxa from the Chilean subsections of Eriosyce using a Bayesian and maximum likelihood phylogenetic framework. Also, we attempted to find out if the divergence between the sister taxa in the Neoporteria group had been caused by allopatric or sympatric mechanisms. The morphology-based analysis placed E. chilensis basal within the Neoporteria clade and suggested a further broadening of the group by including E. taltalensis var. taltalensis, formerly considered a member of subsection Horridocactus. However, the combined DNA data placed E. sociabilis and E. taltalensis var. taltalensis within the Horridocactus clade, and placed E. chilensis with E. subgibbosa var. litoralis. The broad concept of E. subgibbosa sensu Kattermann (comprising seven infraspecific taxa), was rejected by our combined molecular results. Finally, our results corroborated changes in subsection Neoporteria proposed by various authors and suggested further modifications within Neoporteria. The analyses of the degree of geographic overlap of the predicted distributions indicated null overlap between the sister taxa, and one probable hybrid origin of E. chilensis, indicating that evolutionary divergence is mainly caused by an allopatric process associated with climatic tolerance.     

Bovine somatic cell nuclear transfer using recipient oocytes recovered by ovum pick-up: effect of maternal lineage of oocyte donors.

The efficiency of bovine nuclear transfer using recipient oocytes recovered by ultrasound-guided follicle aspiration (ovum pick-up [OPU]) was investigated. Oocyte donors were selected from 2 distinct maternal lineages (A and B) differing in 11 nucleotide positions of the mitochondrial DNA control region. A total of 1342 cumulus-oocyte complexes (COCs) were recovered. The numbers of total COCs and class I/II COCs recovered from donors of lineage A were higher (P < 0.001) than those obtained from lineage B. Follicle aspiration once per week yielded a higher (P < 0.001) total number of COCs per session than aspiration twice per week, whereas the reproduction status of donors (heifer vs. cow) had no effect on OPU results. Of the 1342 oocytes recovered, 733 (55%) were successfully matured in vitro and used for nuclear transfer. Fusion was achieved in 550 (75%) karyoplast-cytoplast complexes (KCCs), resulting in 277 (50%) cleaved embryos on Day 3. On Day 7 of culture, 84 transferable embryos (15% based on fused KCCs) were obtained. After 38 transfers (10 single, 22 double, and 6 triple transfers), 9 recipients (8 double and 1 triple transfer) were diagnosed as pregnant on Day 28, corresponding to a pregnancy rate of 24%. The proportion of transferable embryos on Day 7 was significantly (P < 0.05) influenced by maternal lineage of oocyte donors and by the frequency of follicle aspiration. Our study demonstrates the feasibility of generating nuclear transfer embryos with defined cytoplasmic background. These will be valuable tools to experimentally dissect the effects of nuclear and cytoplasmic components on embryonic, fetal, and postnatal development.     

A Mutational Hotspot and Strong Selection Contribute to the Order of Mutations Selected for during Escherichia coli Adaptation to the Gut

The relative role of drift versus selection underlying the evolution of bacterial species within the gut microbiota remains poorly understood. The large sizes of bacterial populations in this environment suggest that even adaptive mutations with weak effects, thought to be the most frequently occurring, could substantially contribute to a rapid pace of evolutionary change in the gut. We followed the emergence of intra-species diversity in a commensal Escherichia coli strain that previously acquired an adaptive mutation with strong effect during one week of colonization of the mouse gut. Following this first step, which consisted of inactivating a metabolic operon, one third of the subsequent adaptive mutations were found to have a selective effect as high as the first. Nevertheless, the order of the adaptive steps was strongly affected by a mutational hotspot with an exceptionally high mutation rate of 10⁻⁵. The pattern of polymorphism emerging in the populations evolving within different hosts was characterized by periodic selection, which reduced diversity, but also frequency-dependent selection, actively maintaining genetic diversity. Furthermore, the continuous emergence of similar phenotypes due to distinct mutations, known as clonal interference, was pervasive. Evolutionary change within the gut is therefore highly repeatable within and across hosts, with adaptive mutations of selection coefficients as strong as 12% accumulating without strong constraints on genetic background. In vivo competitive assays showed that one of the second steps (focA) exhibited positive epistasis with the first, while another (dcuB) exhibited negative epistasis. The data shows that strong effect adaptive mutations continuously recur in gut commensal bacterial species.     

Gap analysis of two savanna-type ecoregions: a two-scale floristic approach applied to the Llanos de Moxos and Beni Cerrado,Bolivia

The Beni savannas (locally referred to as pampas) is composed of two clearly differentiated ecoregions, the Llanos de Moxos (or Moxos) and the Beni Cerrado. Both tropical savannas are shaped to a greater (Moxos) or lesser (Beni Cerrado) by cycles of drought and flood and the labor of generation of farmers. It contains floristic elements of four biogeographic regions (Amazonian, Chaco, Cerrado and Chiquitana). However, in spite of their biological richness, they are little represented in the National System of Protected Areas (SNAP, in Spanish). By employing an ecoregion and sub-ecoregion approach, we examined the representation of both savanna-type ecoregions in the Departmental System of Protected Areas (SDAP, in Spanish), which includes national, departmental, municipal, and private protected areas. The study also enabled us to compare Bolivia’s newest ecoregion/vegetation zones maps as applied to the both savannas and to produce a sub-ecoregion map for the Beni department (northeastern Bolivia). Our results show that the Llanos de Moxos and the Beni Cerrado are found in protected areas of departmental and municipal level. Although they are still under-represented (mainly the Beni Cerrado), they have nonetheless important extensions inside these protected areas. A better representation of these zones would guarantee improved levels of protection of these unique ecosystems. On the other hand, our study shows the importance of the conservation-representation target relationships (sensu Rodrigues et al. 2004). This is the first time that this approach is used to examine gaps of floristic representativeness of savanna-type ecoregions showing that the traditional 10% minimal conservation target should be used with caution.     

Relationship between floral traits and floral visitors in two coexisting Tecoma species (Bignoniaceae)

In this paper, we studied the floral biology of Tecoma fulva ssp. garrocha and T.?stans in Vaqueros (Salta, Argentina), where both species coexist. We tested the idea that floral traits are associated with the pollinator types that visit them. According to our results, T.?fulva ssp. garrocha presented traits common to bird flowers and were visited by two species of Trochilidae (Colibri serrirostris and Chlorostilbon lucidus). In addition, T.?stans exhibited traits common to hymenoptera flowers and were visited principally by Apis mellifera and Bombus atratus. This study showed that floral traits are predictive of animal visitors.     

America's Most Famous Human Footprints: History,Context and First Description of Mid-Holocene Tracks from the Shores of Lake Managua,Nicaragua

Human tracks discovered in 1874 at a site named El Cauce or Acahualinca near the shores of Lake Managua, Nicaragua, are the most famous and abundant human tracks in the Americas. They represent a landmark ichnological discovery during the late 19th century that generated much debate regarding their age and origins. Reported dates for the tracks range from 2,120 to 6,500 B.P. The site, which is now situated within the limits of Nicaragua's capital city of Managua, forms the basis of the Acahualinca Tracks Museum (Huellas de Acahualinca) and has been in place since 1953. However, it is still little known and has not been systematically studied, despite being an important window into Meso-American prehistory. Two exposures of a surface of volcanic ash reveal hundreds of human tracks comprising a minimum of 12 clearly defined trackways, and a trampled zone or path representing at least three more individuals, all heading in the same northwesterly direction. Tracks of deer, opossum and at least one bird are also present. Bison tracks collected from another nearby site (El Recreo) that is no longer accessible are on display at the museum. The Acahualinca tracks are noteworthy for the exceptional quality of preservation. We herein present the first maps of the two exposures, which combine to tell a story of human and animal activity along the shores of ancient Lake Managua several thousand years ago.