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1.
《Saudi Journal of Biological Sciences》2017,24(6):1288-1293
The antimicrobial activity of plant extract of Peganum harmala, a medicinal plant has been studied already. However, knowledge about bacterial diversity associated with different parts of host plant antagonistic to different human pathogenic bacteria is limited. In this study, bacteria were isolated from root, leaf and fruit of plant. Among 188 bacterial isolates isolated from different parts of the plant only 24 were found to be active against different pathogenic bacteria i.e. Escherichia coli, Methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecium, Enterococcus faecalis and Pseudomonas aeruginosa. These active bacterial isolates were identified on the basis of 16S rRNA gene analysis. Total population of bacteria isolated from plant was high in root, following leaf and fruit. Antagonistic bacteria were also more abundant in root as compared to leaf and fruit. Two isolates (EA5 and EA18) exhibited antagonistic activity against most of the targeted pathogenic bacteria mentioned above. Some isolates showed strong inhibition for one targeted pathogenic bacterium while weak or no inhibition for others. Most of the antagonistic isolates were active against MRSA, following E. faecium, P. aeruginosa, E. coli and E. faecalis. Taken together, our results show that medicinal plants are good source of antagonistic bacteria having inhibitory effect against clinical bacterial pathogens. 相似文献
2.
《Harmful algae》2017
In the last decades, the cyanobacterium Dolichospermum lemmermannii showed an increasing spread to Southern Europe, raising serious concerns due to its ability to produce cyanotoxins. The widening of its geographic distribution and the observation of strains showing high optimum temperature underline its ecological heterogeneity, suggesting the existence of different ecotypes. To investigate its biogeography, new isolates from different European water bodies, together with strains maintained by the Norwegian Institute for Water Research Culture Collection of Algae, were genetically characterised for the 16S rRNA gene and compared with strains obtained from public repositories. Geographic distance highly influenced the differentiation of genotypes, further suggesting the concurrent role of geographic isolation, physical barriers and environmental factors in promoting the establishment of phylogenetic lineages adapted to specific habitats. Differences among populations were also examined by morphological analysis and evaluating the toxic potential of single strains, which revealed the exclusive ability of North European strains to produce microcystins, whereas the populations in Southern Europe tested negative for a wide range of cyanotoxins. The high dispersion ability and the existence of toxic genotypes indicate the possible spread of harmful blooms in other temperate regions. 相似文献
3.
Phylogenetic relationship within Neuroptera is controversial, particularly for the various hypotheses based on both morphological and molecular evidence. In the present study, we determined the complete mitochondrial genome (mitogenome) of Gatzara jezoensis, which is the second representative of the tribe Dendroleontini. The G. jezoensis mitogenome contained the conserved set of 37 mitochondrial genes and a putative control region, with a conserved gene arrangement which was similar to that of most sequenced neuropteran mitogenomes. All transfer RNAs exhibited the canonical cloverleaf secondary structure, except for trnS(AGN). The control region contained two conserved elements (ploy-T stretch and ATGGTTCAAYAAAATAAYYCYCTC motif) and abundant microsatellite-like elements. The phylogenetic analysis of sequenced neuropteran mitogenomes using the concatenated protein-coding genes (PCGs) and ribosomal genes recovered the monophyly of Myrmeleontidae, which revealed this dataset could generate the more robust phylogeny of Neuroptera than that of 13 PCGs dataset. 相似文献
4.
Mathia Colwell Melissa Drown Kelly Showel Chelsea Drown Amanda Palowski 《Epigenetics》2018,13(1):49-60
Ultraconserved noncoding elements (UCNEs) constitute less than 1 Mb of vertebrate genomes and are impervious to accumulating mutations. About 4000 UCNEs exist in vertebrate genomes, each at least 200 nucleotides in length, sharing greater than 95% sequence identity between human and chicken. Despite extreme sequence conservation over 400 million years of vertebrate evolution, we show both ordered interspecies and within-species interindividual variation in DNA methylation in these regions. Here, we surveyed UCNEs with high CpG density in 56 species finding half to be intermediately methylated and the remaining near 0% or 100%. Intermediately methylated UCNEs displayed a greater range of methylation between mouse tissues. In a human population, most UCNEs showed greater variation than the LINE1 transposon, a frequently used epigenetic biomarker. Global methylation was found to be inversely correlated to hydroxymethylation across 60 vertebrates. Within UCNEs, DNA methylation is flexible, conserved between related species, and relaxed from the underlying sequence selection pressure, while remaining heritable through speciation. 相似文献
5.
Caio Maximino 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2008,194(11):939-944
The fast-start is an ecologically relevant behavior pattern in fishes. The present article analyses the distribution of five
continuous kinematic traits (latency for response initiation, time to maximum angular velocity, time to maximum displacement
velocity, maximum angular velocity, and maximum displacement velocity) in eight of the eleven species described in Eaton (66:65–81,
1977). Phylogenetic generalized least square estimation of ancestor states demonstrated evolutionary changes in maximum angular
velocity and maximum displacement velocity, consistent with species differences in the same variables. These changes in maximum
velocity are also correlated (phylogenetically independent contrasts) with the mean body sizes of all species, pointing to
the possibility that body size was an evolutionary constraint on maximum velocities. The conservation of the other traits
suggest that they are mainly constrained by neural control, and a trade-off between neural and body size-constraints is proposed
ex hypothesi.
An erratum to this article can be found at 相似文献
6.
David C. Nickle Gerald H. Learn Matthew W. Rain James I. Mullins John E. Mittler 《Journal of molecular evolution》2002,54(1):134-137
Studies of ancient DNA have attracted considerable attention in scientific journals and the popular press. Several of the
more extreme claims for ancient DNA have been questioned on biochemical grounds (i.e., DNA surviving longer than expected)
and evolutionary grounds (i.e., nucleotide substitution patterns not matching theoretical expectations for ancient DNA). A
recent letter to Nature from Vreeland et al. (2000), however, tops all others with respect to age and condition of the specimen. These researchers
extracted and cultured a bacterium from an inclusion body from what they claim is a 250 million-year (Myr)-old salt crystal.
If substantiated, this observation could fundamentally alter views about bacterial physiology, ecology and evolution. Here
we report on molecular evolutionary analyses of the 16S rDNA from this specimen. We find that 2-9-3 differs from a modern
halophile, Salibacillus marismortui, by just 3 unambiguous bp in 16S rDNA, versus the ∼59 bp that would be expected if these bacteria evolved at the same rate
as other bacteria. We show, using a Poisson distribution, that unless it can be shown that S. marismortui evolves 5 to 10 times more slowly than other bacteria for which 16S rDNA substitution rates have been established, Vreeland
et al.'s claim would be rejected at the 0.05 level. Also, a molecular clock test and a relative rates test fail to substantiate
Vreeland et al.'s claim that strain 2-9-3 is a 250-Myr-old bacterium. The report of Vreeland et al. thus falls into a long
series of suspect ancient DNA studies.
Received: 12 April 2001 / Accepted: 9 June 2001 相似文献
7.
Mikael Falconnet 《Mathematical biosciences》2010,228(1):90-99
We show that the Bayesian star paradox, first proved mathematically by Steel and Matsen for a specific class of prior distributions, occurs in a wider context including less regular, possibly discontinuous, prior distributions. 相似文献
8.
Summary Statistical properties of the ordinary least-squares (OLS), generalized least-squares (GLS), and minimum-evolution (ME) methods of phylogenetic inference were studied by considering the case of four DNA sequences. Analytical study has shown that all three methods are statistically consistent in the sense that as the number of nucleotides examined (m) increases they tend to choose the true tree as long as the evolutionary distances used are unbiased. When evolutionary distances (dij's) are large and sequences under study are not very long, however, the OLS criterion is often biased and may choose an incorrect tree more often than expected under random choice. It is also shown that the variance-covariance matrix of dij's becomes singular as dij's approach zero and thus the GLS may not be applicable when dij's are small. The ME method suffers from neither of these problems, and the ME criterion is statistically unbiased. Computer simulation has shown that the ME method is more efficient in obtaining the true tree than the OLS and GLS methods and that the OLS is more efficient than the GLS when dij's are small, but otherwise the GLS is more efficient.Offprint requests to: M. Nei 相似文献
9.
The parsimony and bootstrap branching pattern of major groups of land plants derived from relevant 5S rRNA sequence trees
have been discussed in the light of paleobotanical and morphological evidences. Although 5S rRNA sequence information is not
useful for dileneating angiosperm relationships, it does capture the earlier phase of land plant evolution. The consensus
branching pattern indicates an ancient split of bryophytes and vascular plants from the charophycean algal stem. Among the
bryophytes,Marchantia andLophocolea appear to be phylogenetically close and together withPlagiomnium form a monophyletic group.Lycopodium andPsilotum arose early in vascular land plant evolution, independent of fem-sphenopsid branch. Gymnosperms are polyphyletic; conifers,
Gnetales and cycads emerge in that order with ginkgo joiningCycas. Among the conifers,Metasequoia,Juniperus andTaxus emerge as a branch independent ofPinus which joins Gnetales.
The phylogeny derived from the available ss-RNA sequences shows that angiosperms are monophyletic with monocots and dicots
diverging from a common stem. The nucleotide replacements during angiosperm descent from the gymnosperm ancestor which presumably
arose around 370 my ago indicates that monocots and dicots diverged around 180 my ago, which is compatible with the reported
divergence estimate of around 200 my ago deduced from chloroplast DNA sequences.
Since deceased. 相似文献
10.