Search results for "selection pressure"
showing 4 items of 4 documents
Study of aerobic granular sludge stability in a continuous-flow membrane bioreactor.
2015
A granular continuous-flow membrane bioreactor with a novel hydrodynamic configuration was developed to evaluate the stability of aerobic granular sludge (AGS). Under continuous-flow operation (Period I), AGS rapidly lost their structural integrity resulting in loose and fluffy microbial aggregates in which filamentous bacteria were dominant. The intermittent feeding (Period II) allowed obtaining the succession of feast and famine conditions that favored the increase in AGS stability. Although no further breakage occurred, the formation of new granules was very limited, owing to the absence of the hydraulic selection pressure. These results noted the necessity to ensure, on the one hand the…
Molecular evolutionary analysis of type-1 human astroviruses identifies putative sites under selection pressure on the capsid protein
2017
Human astroviruses (HAstV) are important enteric pathogens that can be classified into eight sero/genotypes (HAstV-1 to -8). Although the various HAstV types show global spread, type-1 strains tend to be predominant. Molecular analysis of the genomic region encoding the capsid protein (ORF2) has revealed discrete sequence variation, with different lineages within each HAstV type and at least three major lineages have been identified within HAstV-1. Longitudinal epidemiological surveillance has revealed temporal shift of the various HAstV-1 lineages. Metadata analysis of HAstV-1 sequences available in the databases also revealed temporal shifts of the circulation of HAstV-1 lineages, suggest…
Genetic plasticity of atrazine-degrader: evidence for the deletion of atzABC genes in pseudomonas sp. adp in response to cyanuric acid selection pres…
2010
International audience; Several bacterial strains are known to metabolize s-triazines herbicides among which atrazine reported worldwidel to contaminate soil and water resources. The complete mineralization of atrazine to carbon dioxide and ammonium is catalyzed by 6 hydrolytic enzymes encoded by atzABCDEF genes located on the plasmid pADP1 in Pseudomonas ADP. The atzABC genes code for the upper pathway transforming atrazine to cyanuric acid, while the atzDEF genes code for the lower pathway transforming cyanuric acid to simple compounds. In order to study the genetic plasticity of the atrazine catabolic pathway, we performed an in vitro evolution study consisting in applying a continuous s…
Data from: How do cuticular hydrocarbons evolve? Physiological constraints and climatic and biotic selection pressures act on a complex functional tr…
2016
Cuticular hydrocarbons (CHCs) cover the cuticles of virtually all insects, serving as a waterproofing agent and as a communication signal. The causes for the high CHC variation between species, and the factors influencing CHC profiles, are scarcely understood. Here, we compare CHC profiles of ant species from seven biogeographic regions, searching for physiological constraints and for climatic and biotic selection pressures. Molecule length constrained CHC composition: long-chain profiles contained fewer linear alkanes, but more hydrocarbons with disruptive features in the molecule. This is probably owing to selection on the physiology to build a semi-fluid cuticular layer, which is necessa…