scholarly journals Population Genomics of Early Events in the Ecological Differentiation of Bacteria

Science ◽  
2012 ◽  
Vol 336 (6077) ◽  
pp. 48-51 ◽  
Author(s):  
B. Jesse Shapiro ◽  
Jonathan Friedman ◽  
Otto X. Cordero ◽  
Sarah P. Preheim ◽  
Sonia C. Timberlake ◽  
...  
Keyword(s):  
Population Genomics ◽  
Population Diversity ◽  
Fundamental Question ◽  
Gene Pools ◽  
Ecological Differentiation ◽  
Habitat Specificity ◽  
Bacterial Populations ◽  
Specific Manner ◽  
Unified Process ◽  
Selection Of

Genetic exchange is common among bacteria, but its effect on population diversity during ecological differentiation remains controversial. A fundamental question is whether advantageous mutations lead to selection of clonal genomes or, as in sexual eukaryotes, sweep through populations on their own. Here, we show that in two recently diverged populations of ocean bacteria, ecological differentiation has occurred akin to a sexual mechanism: A few genome regions have swept through subpopulations in a habitat-specific manner, accompanied by gradual separation of gene pools as evidenced by increased habitat specificity of the most recent recombinations. These findings reconcile previous, seemingly contradictory empirical observations of the genetic structure of bacterial populations and point to a more unified process of differentiation in bacteria and sexual eukaryotes than previously thought.

Current Strategies in the Management of Spinal Metastatic Disease

Swiss Surgery ◽  
2003 ◽  
Vol 9 (2) ◽  
pp. 55-62 ◽  
Author(s):  
Bartanusz ◽  
Porchet
Keyword(s):  
Spinal Cord ◽  
Surgical Techniques ◽  
Cord Compression ◽  
Treatment Modalities ◽  
Surgical Approaches ◽  
Spinal Stabilization ◽  
Management Algorithm ◽  
Specific Manner ◽  
Extensive Surgery ◽  
Selection Of

The treatment of metastatic spinal cord compression is complex. The three treatment modalities that are currently applied (in a histologically non-specific manner) are surgery, radiotherapy and the administration of steroids. The development of new spinal instrumentations and surgical approaches considerably changed the extent of therapeutic options in this field. These new surgical techniques have made it possible to resect these tumours totally, with subsequent vertebral reconstruction and spinal stabilization. In this respect, it is important to clearly identify those patients who can benefit from such an extensive surgery. We present our management algorithm to help select patients for surgery and at the same time identifying those for whom primary non-surgical therapy would be indicated. The retrospective review of surgically treated patients in our department in the last four years reveals a meagre application of conventional guidelines for the selection of the appropriate operative approach in the surgical management of these patients. The reasons for this discrepancy are discussed.

scholarly journals Population genomics and antimicrobial resistance dynamics of Escherichia coli in wastewater and river environments

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jose F. Delgado-Blas ◽  
Cristina M. Ovejero ◽  
Sophia David ◽  
Natalia Montero ◽  
William Calero-Caceres ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Population Genomics ◽  
Population Diversity ◽  
Genomic Diversity ◽  
Resistant Bacteria ◽  
Aquatic Environments ◽  
E Coli ◽  
Water Ecosystems ◽  
Sequence Types

AbstractAquatic environments are key niches for the emergence, evolution and dissemination of antimicrobial resistance. However, the population diversity and the genetic elements that drive the dynamics of resistant bacteria in different aquatic environments are still largely unknown. The aim of this study was to understand the population genomics and evolutionary events of Escherichia coli resistant to clinically important antibiotics including aminoglycosides, in anthropogenic and natural water ecosystems. Here we show that less different E. coli sequence types (STs) are identified in wastewater than in rivers, albeit more resistant to antibiotics, and with significantly more plasmids/cell (6.36 vs 3.72). However, the genomic diversity within E. coli STs in both aquatic environments is similar. Wastewater environments favor the selection of conserved chromosomal structures associated with diverse flexible plasmids, unraveling promiscuous interplasmidic resistance genes flux. On the contrary, the key driver for river E. coli adaptation is a mutable chromosome along with few plasmid types shared between diverse STs harboring a limited resistance gene content.

scholarly journals Effect of Environmental Factors and Influence of Rumen and Hindgut Biogeography on Bacterial Communities in Steers

2010 ◽  
Vol 77 (1) ◽  
pp. 258-268 ◽  
Author(s):  
Gustavo A. Romero-Pérez ◽  
Kim H. Ominski ◽  
Tim A. McAllister ◽  
Denis O. Krause
Keyword(s):  
Ambient Temperature ◽  
Bacterial Communities ◽  
Volatile Fatty Acids ◽  
Principal Component ◽  
Population Diversity ◽  
Access Time ◽  
Sample Type ◽  
Bacterial Populations ◽  
Fecal Samples ◽  
Alfalfa Silage

ABSTRACTFeces from cattle production are considered important sources of bacterial contamination of food and the environment. Little is known about the combined effects of arctic temperatures and fodder tannins on rumen and hindgut bacterial populations. Individual rumen liquor and rectal fecal samples from donor steers fed either alfalfa silage or sainfoin (Onobrychis viciifoliaScop.) silage and waterad libitumwere collected weekly on the first three sampling days and fortnightly afterwards. The daily ambient temperatures were registered and averaged to weekly mean temperatures. Steers fed sainfoin silage had lower (P< 0.05) concentrations of branched-chain volatile fatty acids (VFA) than those fed alfalfa silage. All VFA concentrations were higher (P< 0.001) in rumen liquor samples than in fecal samples. The interaction of sample type and diet showed a significant effect (P< 0.05) on the proportions of the bacterial community that were from the phylaProteobacteriaandVerrucomicrobia.Ambient temperature had an indirect effect (P< 0.05) on the phylumFirmicutes, as it affected its proportional balance. The bacterial population diversity in samples appeared to decrease concurrently with the ambient temperature. The phylumFirmicutesexplained the first principal component at 64.83 and 42.58% of the total variance in rumen liquor and fecal samples, respectively. The sample type had a larger effect on bacterial communities than diet and temperature. Certain bacterial populations seemed to be better adapted than others to environmentally adverse conditions, such as less access time to nutrients due to higher motility and rate of passage of digesta caused by extreme temperatures, or antimicrobials such as tannins, possibly due to an influence of their biogeographical location within the gut.

scholarly journals Genetic diversity and selection of genotypes to enhance Zn and Fe content in common bean

2010 ◽  
Vol 90 (1) ◽  
pp. 49-60 ◽  
Author(s):  
Z I Talukder ◽  
E Anderson ◽  
P N Miklas ◽  
M W Blair ◽  
J Osorno ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Common Bean ◽  
Allelic Variation ◽  
Gene Pools ◽  
Gene Sequences ◽  
Mineral Contents ◽  
Discriminatory Ability ◽  
Fe Content ◽  
Mapping Populations ◽  
Selection Of

Common bean (Phaseolus vulgaris L.) is an important source of dietary protein and minerals worldwide. Genes conditioning variability for mineral contents are not clearly understood. Our ultimate goal is to identify genes conditioning genetic variation for Zn and Fe content. To establish mapping populations for this objective, we tested mineral content of 29 common bean genotypes. Chemical analyses revealed significant genetic variability for seed Zn and Fe contents among the genotypes. Genetic diversity was evaluated with 49 primer pairs, of which 23 were simple sequence repeats (SSR), 16 were developed from tentative consensus (TC) sequences, and 10 were generated from common bean NBS-LRR gene sequences. The discriminatory ability of molecular markers for identifying allelic variation among genotypes was estimated by polymorphism information content (PIC) and the genetic diversity was measured from genetic similarities between genotypes. Primers developed from NBS-LRR gene sequences were highly polymorphic in both PIC values and number of alleles (0.82 and 5.3), followed by SSRs (0.56 and 3.0), and markers developed from TC (0.39 and 2.0). genetic similarity values between genotypes ranged from 14.0 (JaloEEP558 and DOR364) to 91.4 (MIB152 and MIB465). Cluster analysis clearly discriminated the genotypes into Mesoamerican and Andean gene pools. Common bean genotypes were selected to include in crossing to enhance seed Zn and Fe content based on genetic diversity and seed mineral contents of the genotypes. Key words: Common bean, genetic diversity, mineral nutrients, breeding

scholarly journals Effect of antibiotics on bacterial populations: a multi-hierarchical selection process

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 51 ◽  
Author(s):  
José Luis Martínez
Keyword(s):  
Human Body ◽  
Selection Process ◽  
Bacterial Populations ◽  
Bacterial Physiology ◽  
Population Selection ◽  
Human Therapy ◽  
Hierarchical Selection ◽  
Available Information ◽  
Different Levels ◽  
Selection Of

Antibiotics have been widely used for a number of decades for human therapy and farming production. Since a high percentage of antibiotics are discharged from the human or animal body without degradation, this means that different habitats, from the human body to river water or soils, are polluted with antibiotics. In this situation, it is expected that the variable concentration of this type of microbial inhibitor present in different ecosystems may affect the structure and the productivity of the microbiota colonizing such habitats. This effect can occur at different levels, including changes in the overall structure of the population, selection of resistant organisms, or alterations in bacterial physiology. In this review, I discuss the available information on how the presence of antibiotics may alter the microbiota and the consequences of such alterations for human health and for the activity of microbiota from different habitats.

Analysis of genetic diversity within Australian lucerne cultivars and implications for future genetic improvement

2002 ◽  
Vol 53 (6) ◽  
pp. 629 ◽  
Author(s):  
J. M. Musial ◽  
K. E. Basford ◽  
J. A. G. Irwin
Keyword(s):  
Genetic Diversity ◽  
Population Genetic ◽  
Random Amplified Polymorphic Dna ◽  
Population Diversity ◽  
Breeding Programs ◽  
Population Genetic Diversity ◽  
Medicago Sativa L ◽  
Components Analysis ◽  
High Level ◽  
Selection Of

Lucerne (Medicago sativa L.) is autotetraploid, and predominantly allogamous. This complex breeding structure maximises the genetic diversity within lucerne populations making it difficult to genetically discriminate between populations. The objective of this study was to evaluate the level of random genetic diversity within and between a selection of Australian-grown lucerne cultivars, with tetraploid M. falcata included as a possible divergent control source. This diversity was evaluated using random amplified polymorphic DNA (RAPDs). Nineteen plants from each of 10 cultivars were analysed. Using 11 RAPD primers, 96 polymorphic bands were scored as present or absent across the 190 individuals. Genetic similarity estimates (GSEs) of all pair-wise comparisons were calculated from these data. Mean GSEs within cultivars ranged from 0.43 to 0.51. Cultivar Venus (0.43) had the highest level of intra-population genetic diversity and cultivar Sequel HR (0.51) had the lowest level of intra-population genetic diversity. Mean GSEs between cultivars ranged from 0.31 to 0.49, which overlapped with values obtained for within-cultivar GSE, thus not allowing separation of the cultivars. The high level of intra- and inter-population diversity that was detected is most likely due to the breeding of synthetic cultivars using parents derived from a number of diverse sources. Cultivar-specific polymorphisms were only identified in the M. falcata source, which like M. sativa, is outcrossing and autotetraploid. From a cluster analysis and a principal components analysis, it was clear that M. falcata was distinct from the other cultivars. The results indicate that the M. falcata accession tested has not been widely used in Australian lucerne breeding programs, and offers a means of introducing new genetic diversity into the lucerne gene pool. This provides a means of maximising heterozygosity, which is essential to maximising productivity in lucerne.

scholarly journals The perception-prodution link and linguistic theory

Loquens ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. e066
Author(s):  
Mark Hale ◽  
Madelyn Kissock
Keyword(s):  
Speech Perception ◽  
Focal Point ◽  
Fundamental Question ◽  
Experimental Results ◽  
Linguistic Theory ◽  
Psychological Literature ◽  
Linguistic System ◽  
Theoretical Linguistics ◽  
Recent Trends ◽  
Selection Of

Recent trends in infant (and adult) speech perception studies, especially in the psychological literature where much of the speech perception work is being and has been done, shows a growing focus on more integrated perception-production-sensorimotor (PPS) bases for perception (Werker & Gervain 2013). We look here at whether the results of such studies are significant for theoretical linguistics – specifically for the fundamental question of how the linguistic system is acquired. We examine a selection of recent experimental results, using Bruderer, Danielson, Kandhadai & Werker (2015) as the focal point.

scholarly journals Origins of pandemic Vibrio cholerae from environmental gene pools

2016 ◽  
Author(s):  
B. Jesse Shapiro ◽  
Inès Levade ◽  
Gabriela Kovacikova ◽  
Ronald K. Taylor ◽  
Salvador Almagro-Moreno
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factors ◽  
Virulence Genes ◽  
Mammalian Host ◽  
Comparative Genomic ◽  
Gene Pools ◽  
Host Colonization ◽  
Bacterial Populations ◽  
Genomic Features ◽  
Clinical Strains

AbstractSome microbes can transition from an environmental lifestyle to a pathogenic one1–3. This ecological switch typically occurs through the acquisition of horizontally acquired virulence genes4,5. However, the genomic features that must be present in a population prior to the acquisition of virulence genes and emergence of pathogenic clones remain unknown. We hypothesized that virulence adaptive polymorphisms (VAPs) circulate in environmental populations and are required for this transition. We developed a comparative genomic framework for identifying VAPs, using Vibrio cholerae as a model. We then characterized several environmental VAP alleles to show that, while some of them reduced the ability of clinical strains to colonize a mammalian host, other alleles conferred efficient host colonization. These results show that VAPs are present in environmental bacterial populations prior to the emergence of virulent clones. We propose a scenario in which VAPs circulate in the environment, they become selected and enriched under certain ecologicalconditions, and finally a genomic background containing several VAPs acquires virulence factors that allows for its emergence as a pathogenic clone.

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