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101.
102.
103.
Comparison of the evolutionary dynamics of symbiotic and housekeeping loci: a case for the genetic coherence of rhizobial lineages 总被引:6,自引:1,他引:5
In prokaryotes, lateral gene transfer across chromosomal lineages may be
mediated by plasmids, phages, transposable elements, and other accessory
DNA elements. However, the importance of such transfer and the evolutionary
forces that may restrict gene exchange remain largely unexplored in native
settings. In this study, tests of phylogenetic congruence are employed to
explore the range of horizontal transfer of symbiotic (sym) loci among
distinct chromosomal lineages of native rhizobia, the nitrogen-fixing
symbiont of legumes. Rhizobial strains isolated from nodules of several
host plant genera were sequenced at three loci: symbiotic nodulation genes
(nodB and nodC), the chromosomal housekeeping locus glutamine synthetase II
(GSII), and a portion of the 16S rRNA gene. Molecular phylogenetic analysis
shows that each locus generally subdivides strains into the same major
groups, which correspond to the genera Rhizobium, Sinorhizobium, and
Mesorhizobium. This broad phylogenetic congruence indicates a lack of
lateral transfer across major chromosomal subdivisions, and it contrasts
with previous studies of agricultural populations showing broad transfer of
sym loci across divergent chromosomal lineages. A general correspondence of
the three rhizobial genera with major legume groups suggests that host
plant associations may be important in the differentiation of rhizobial nod
and chromosomal loci and may restrict lateral transfer among strains. The
second major result is a significant incongruence of nod and GSII
phylogenies within rhizobial subdivisions, which strongly suggests
horizontal transfer of nod genes among congenerics. This combined evidence
for lateral gene transfer within, but not between, genetic subdivisions
supports the view that rhizobial genera are "reproductively isolated" and
diverge independently. Differences across rhizobial genera in the
specificity of host associations imply that the evolutionary dynamics of
the symbiosis vary considerably across lineages in native settings.
相似文献
104.
Karl Rumbold Hugo JJ van Buijsen Karin M Overkamp Johan W van Groenestijn Peter J Punt J van der Mari?t Werf 《Microbial cell factories》2009,8(1):64
Background
Increasingly lignocellulosic biomass hydrolysates are used as the feedstock for industrial fermentations. These biomass hydrolysates are complex mixtures of different fermentable sugars, but also inhibitors and salts that affect the performance of the microbial production host. The performance of six industrially relevant microorganisms, i.e. two bacteria (Escherichia coli and Corynebacterium glutamicum), two yeasts (Saccharomyces cerevisiae and Pichia stipitis) and two fungi (Aspergillus niger and Trichoderma reesei) were compared for their (i) ability to utilize monosaccharides present in lignocellulosic hydrolysates, (ii) resistance against inhibitors present in lignocellulosic hydrolysates, (iii) their ability to utilize and grow on different feedstock hydrolysates (corn stover, wheat straw, sugar cane bagasse and willow wood). The feedstock hydrolysates were generated in two manners: (i) thermal pretreatment under mild acid conditions followed by enzymatic hydrolysis and (ii) a non-enzymatic method in which the lignocellulosic biomass is pretreated and hydrolyzed by concentrated sulfuric acid. Moreover, the ability of the selected hosts to utilize waste glycerol from the biodiesel industry was evaluated. 相似文献105.
106.
107.
Elmar W Tobi Bastiaan T Heijmans Dennis Kremer Hein Putter Henriette A Delemarre-van de Waal Martijn JJ Finken Jan M Wit P Eline Slagboom 《Epigenetics》2011,6(2):171-176
Being born small for gestational age (SGA), a proxy for intrauterine growth restriction (IUGR) and prenatal famine exposure are both associated with a greater risk of metabolic disease. Both associations have been hypothesized to involve epigenetic mechanisms. We investigated whether prenatal growth restriction early in pregnancy was associated with changes in DNA methylation at loci that were previously shown to be sensitive to early gestational famine exposure. We compared 38 individuals born preterm (<32 weeks) and with a birth weight too low for their gestational age (less than −1SDS; SGA) with 75 individuals born preterm but with a birth weight appropriate for their gestational age (greater than −1SDS) and a normal postnatal growth (greater than −1SDS at three months post term; AGA). The SGA individuals were not only lighter at birth, but also had a smaller length (p = 3.3 × 10−13) and head circumference at birth (p = 4.1 × 10−13). The DNA methylation levels of IGF2, GNASAS, INSIGF and LEP were 48.5, 47.5, 79.4 and 25.7% respectively. This was not significantly different between SGA and AGA individuals. Risk factors for being born SGA, including preeclampsia and maternal smoking, were also not associated with DNA methylation at these loci. Growth restriction early in development is not associated with DNA methylation at loci shown to be affected by prenatal famine exposure. Our and previous results by others indicate that prenatal growth restriction and famine exposure may be associated with different epigenetic changes or non-epigenetic mechanisms that may lead to similar later health outcomes.Key words: SGA, DOHAD, IUGR, DNA methylation, famine, IGF2, LEP, INS, GNASAS 相似文献
108.
Jacques M Mathieu John Schloendorn Bruce E Rittmann Pedro JJ Alvarez 《Microbial cell factories》2009,8(1):21-18
Catabolic insufficiency in humans leads to the gradual accumulation of a number of pathogenic compounds associated with age-related
diseases, including atherosclerosis, Alzheimer's disease, and macular degeneration. Removal of these compounds is a widely
researched therapeutic option, but the use of antibodies and endogenous human enzymes has failed to produce effective treatments,
and may pose risks to cellular homeostasis. Another alternative is "medical bioremediation," the use of microbial enzymes
to augment missing catabolic functions. The microbial genetic diversity in most natural environments provides a resource that
can be mined for enzymes capable of degrading just about any energy-rich organic compound. This review discusses targets for
biodegradation, the identification of candidate microbial enzymes, and enzyme-delivery methods. 相似文献
109.
Quezada-Rivera JJ RE Soria-Guerra FS Pérez-Juárez L Martínez-González SE Valdés- Rodríguez NL Vasco-Méndez JF Morales-Domínguez 《Phyton》2019,88(1):25-35
The use of antimicrobial peptides (AMPs) synthesized
by bacteria (bacteriocins) is an alternative for combating multidrug
resistant bacterial strains and their production by recombinant route
is a viable option for their mass production. The bacteriocin E-760
isolated from the genus Enterococcus sp. has been shown to possess
inhibitory activity against Gram-negative and Gram-positive
bacteria. In this study, the expression of a chimeric protein coding
for E-760 in the nucleus of C. reinhardtii was evaluated, as well as,
its antibacterial activity. The synthetic gene E-760S was inserted
into the genome of C. reinhardtii using Agrobacterium tumefaciens.
A transgenic line was identified in TAP medium with hygromycin
and also by PCR. The increment in the culture medium temperature
of the transgenic strain at 35 °C for 10 minutes, increased the
production level of the recombinant protein from 0.14 (Noninduced
culture, NIC) to 0.36% (Induced culture, IC) of total soluble
proteins (TSP); this was quantified by an ELISA assay. Recombinant
E-760 possesses activity against Staphylococcus aureus in 0.34 U
log, Streptococcus agalactiae in 0.48 U log, Enterococcus faecium in
0.36 U log, Pseudomonas aeruginosa in 2 U log and for Klebsiella
pneumoniae, the activity was 0.07 U log. These results demonstrate
that the nucleus transformation of C. reinhardtii can function as
a stable expression platform for the production of the synthetic
gene E-760 and it can potentially be used as an antibacterial agent. 相似文献
110.
Tineke E Buffart Melanie Louw Nicole CT van Grieken Marianne Tijssen Beatriz Carvalho Bauke Ylstra Heike Grabsch Chris JJ Mulder Cornelis JH van de Velde Schalk W van der Merwe Gerrit A Meijer 《BMC medical genomics》2011,4(1):7