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101.
A marker rescue assay of noninfectious fragments of avian leukosis virus DNAs is describe. DNA fragments were prepared either by sonication of EcoRI-digestion of DNAs of chicken cells infected with wild-type Rous sarcoma virus, with a nontransforming avian leukosis virus, and with a mutant of Rous sarcoma virus temperature sensitive for transformation. Recipient cultures of chicken embryo fibroblasts were treated with noninfectious DNA fragments and infected with temperature-sensitive mutants of Rous sarcoma virus defective in DNA polymerase or in an internal virion structural protein. Wild-type progeny viruses which replicated at the nonpermissive temperature were isolated. Some of the wild-type progeny acquired both the wild-type DNA polymerase and the subgroup specificity of the Rous sarcona virus strain used for preparation of sonicated or EcoRI-digested DNA fragments. Therefore the genetic markers for DNA polymerase and envelope were linked and appeared to be located on the same EcoRi fragment of the DNA of Rous sarcoma virus-infected cells. 相似文献
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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
110.
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