Chlorine disinfection to drinking water plays an important role in preventing and controlling waterborne disease outbreaks globally. Nevertheless, little is known about why it enriches the antibiotic ...resistance genes (ARGs) in bacteria after chlorination. Here, ARGs released from killed antibiotic-resistant bacteria (ARB), and culturable chlorine-injured bacteria produced in the chlorination process as the recipient, were investigated to determine their contribution to the horizontal transfer of ARGs during disinfection treatment. We discovered Escherichia coli, Salmonella aberdeen, Pseudomonas aeruginosa and Enterococcus faecalis showed diverse resistance to sodium hypochlorite, and transferable RP4 could be released from killed sensitive donor consistently. Meanwhile, the survival of chlorine-tolerant injured bacteria with enhanced cell membrane permeabilisation and a strong oxidative stress-response demonstrated that a physiologically competent cell could be transferred by RP4 with an improved transformation frequency of up to 550 times compared with the corresponding untreated bacteria. Furthermore, the water quality factors involving chemical oxygen demand (COD
), ammonium nitrogen and metal ions (Ca
and K
) could significantly promote above transformation frequency of released RP4 into injured E. faecalis. Our findings demonstrated that the chlorination process promoted the horizontal transfer of plasmids by natural transformation, which resulted in the exchange of ARGs across bacterial genera and the emergence of new ARB, as well as the transfer of chlorine-injured opportunistic pathogen from non-ARB to ARB. Considering that the transfer elements were quite resistant to degradation through disinfection, this situation poses a potential risk to public health.
After decades of molecular phylogenetic studies, the deep phylogeny of gymnosperms has not been resolved, and the phylogenetic placement of Gnetales remains one of the most controversial issues in ...seed plant evolution. To resolve the deep phylogeny of seed plants and to address the sources of phylogenetic conflict, we conducted a phylotranscriptomic study with a sampling of all 13 families of gymnosperms and main lineages of angiosperms. Multiple datasets containing up to 1 296 042 sites across 1308 loci were analysed, using concatenation and coalescence approaches. Our study generated a consistent and well-resolved phylogeny of seed plants, which places Gnetales as sister to Pinaceae and thus supports the Gnepine hypothesis. Cycads plus
is sister to the remaining gymnosperms. We also found that Gnetales and angiosperms have similar molecular evolutionary rates, which are much higher than those of other gymnosperms. This implies that Gnetales and angiosperms might have experienced similar selective pressures in evolutionary histories. Convergent molecular evolution or homoplasy is partially responsible for the phylogenetic conflicts in seed plants. Our study provides a robustly reconstructed backbone phylogeny that is important for future molecular and morphological studies of seed plants, in particular gymnosperms, in the light of evolution.
Phylogenetic reconstruction is fundamental to study evolutionary biology and historical biogeography. However, there was not a molecular phylogeny of gymnosperms represented by extensive sampling at ...the genus level, and most published phylogenies of this group were constructed based on cytoplasmic DNA markers and/or the multi-copy nuclear ribosomal DNA. In this study, we use LFY and NLY, two single-copy nuclear genes that originated from an ancient gene duplication in the ancestor of seed plants, to reconstruct the phylogeny and estimate divergence times of gymnosperms based on a complete sampling of extant genera. The results indicate that the combined LFY and NLY coding sequences can resolve interfamilial relationships of gymnosperms and intergeneric relationships of most families. Moreover, the addition of intron sequences can improve the resolution in Podocarpaceae but not in cycads, although divergence times of the cycad genera are similar to or longer than those of the Podocarpaceae genera. Our study strongly supports cycads as the basal-most lineage of gymnosperms rather than sister to Ginkgoaceae, and a sister relationship between Podocarpaceae and Araucariaceae and between Cephalotaxaceae-Taxaceae and Cupressaceae. In addition, intergeneric relationships of some families that were controversial, and the relationships between Taxaceae and Cephalotaxaceae and between conifers and Gnetales are discussed based on the nuclear gene evidence. The molecular dating analysis suggests that drastic extinctions occurred in the early evolution of gymnosperms, and extant coniferous genera in the Northern Hemisphere are older than those in the Southern Hemisphere on average. This study provides an evolutionary framework for future studies on gymnosperms.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•We observed eARG and iARG pollution in tap water with an evident seasonal pattern.•Extracellular TetC had the highest median level in tap water.•sul1 and sul2 were the most abundant iARGs in tap ...water.•iARG classes were related to the specific physicochemical index of water quality.
Antibiotic resistance genes (ARGs) have gained global attention due to their public health threat. Extracelluar ARGs (eARGs) can result in the dissemination of antibiotic resistance via free-living ARGs in natural environments, where they promote ARB transmission in drinking water distribution systems. However, eARG pollution in tap water has not been well researched. In this study, concentrations of eARGs and intracellular ARGs (iARGs) in tap water, sampled at Tianjin, China, were investigated for one year. Fourteen eARG types were found at the highest concentration of 1.3 × 105 gene copies (GC)/L. TetC was detected in 66.7% of samples, followed by sul1, sul2, and qnrA with the same detection frequency of 41.7%. Fifteen iARGs (including tetA, tetB, tetM, tetQ, tetX, sul1, sul2, sul3, ermB, blaTEM, and qnrA) were continuously detected in all collected tap water samples with sul1 and sul2 the most abundant. Additionally, both eARG and iARG concentrations in tap water presented a seasonal pattern with most abundant prevalence in summer. The concentration of observed intracellular sulfonamide resistance genes showed a significantly positive correlation with total nitrogen concentrations. This study suggested that eARG and iARG pollution of drinking water systems pose a potential risk to human public health.
Gymnosperms represent five of the six lineages of seed plants. However, most sequenced plant mitochondrial genomes (mitogenomes) have been generated for angiosperms, whereas mitogenomic sequences ...have been generated for only six gymnosperms. In particular, complete mitogenomes are available for all major seed plant lineages except Conifer II (non-Pinaceae conifers or Cupressophyta), an important lineage including six families, which impedes a comprehensive understanding of the mitogenomic diversity and evolution in gymnosperms.
Here, we report the complete mitogenome of Taxus cuspidata in Conifer II. In comparison with previously released gymnosperm mitogenomes, we found that the mitogenomes of Taxus and Welwitschia have lost many genes individually, whereas all genes were identified in the mitogenomes of Cycas, Ginkgo and Pinaceae. Multiple tRNA genes and introns also have been lost in some lineages of gymnosperms, similar to the pattern observed in angiosperms. In general, gene clusters could be less conserved in gymnosperms than in angiosperms. Moreover, fewer RNA editing sites were identified in the Taxus and Welwitschia mitogenomes than in other mitogenomes, which could be correlated with fewer introns and frequent gene losses in these two species.
We have sequenced the Taxus cuspidata mitogenome, and compared it with mitogenomes from the other four gymnosperm lineages. The results revealed the diversity in size, structure, gene and intron contents, foreign sequences, and mutation rates of gymnosperm mitogenomes, which are different from angiosperm mitogenomes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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•Intergeneric relationships of Pinaceae are completely resolved by transcriptomic analysis.•Extant Pinaceae genera diverged earlier than the break-up of Pangea.•Two radiation events ...occurred in the evolution of Pinaceae genera.•Some important morphological characters evolved multiple times in Pinaceae.
Pinaceae comprises 11 genera, and represents the largest family of conifers with an extensive wild distribution in the Northern Hemisphere. Intergeneric relationships of Pinaceae have been investigated using many morphological characters and molecular markers, but phylogenetic positions of four genera, including Cathaya, Cedrus, Nothotsuga and Pseudolarix, remain controversial or have not been completely resolved. To completely resolve the intergeneric relationships of Pinaceae, we conducted a comparative transcriptomic study of 14 species representing all Pinaceae genera. Multiple data sets, containing up to 6,369,681 sites across 4676 loci, were analyzed using concatenation and coalescent methods. Our study generated a robust topology, which divides Pinaceae into two clades, one (pinoid) including Cathaya, Larix, Picea, Pinus, and Pseudotsuga, and the other (abietoid) including Abies, Cedrus, Keteleeria, Nothotsuga, Pseudolarix, and Tsuga. Cathaya and Pinus form a clade sister to Picea; Cedrus is sister to the remaining abietoid genera, and the two genera Nothotsuga and Tsuga form a clade sister to Pseudolarix. The discordant positions of Cathaya, Cedrus and Pseudolarix in different gene trees could be explained by ancient radiation and/or molecular homoplastic evolution. The hybrid origin hypothesis of Nothotsuga is not supported. Based on molecular dating, extant Pinaceae genera diverged since about 206 Mya, earlier than the break-up of Pangea, and the divergence among the pinoid genera occurred earlier than the split among the abietoid genera. Moreover, our study indicates that two radiation events occurred in the evolution of Pinaceae genera, and some important morphological characters evolved multiple times based on ancestral state reconstruction.
Mitochondrial gene transfer/loss is common in land plants, and therefore the fate of missing mitochondrial genes has attracted more and more attention. The gene content of gymnosperm mitochondria ...varies greatly, supplying a system for studying the evolutionary fate of missing mitochondrial genes.
Here, we studied the tempo and pattern of mitochondrial gene transfer/loss in gymnosperms represented by all 13 families, using high-throughput sequencing of both DNA and cDNA. All 41 mitochondrial protein-coding genes were found in cycads, Ginkgo and Pinaceae, whereas multiple mitochondrial genes were absent in Conifer II and Gnetales. In Conifer II, gene transfer from mitochondria to the nucleus followed by loss of the mitochondrial copy was common, but complete loss of a gene in both mitochondrial and nuclear genomes was rare. In contrast, both gene transfer and loss were commonly found in Gnetales. Notably, in Conifer II and Gnetales, the same five mitochondrial genes were transferred to the nuclear genome, and these gene transfer events occurred, respectively, in ancestors of the two lineages. A two-step transfer mechanism (retroprocessing and subsequent DNA-mediated gene transfer) may be responsible for mitochondrial gene transfer in Conifer II and Gnetales. Moreover, the mitochondrial gene content variation is correlated with gene length, GC content, hydrophobicity, and nucleotide substitution rates in land plants.
This study reveals a complete evolutionary scenario for variations of mitochondrial gene transferring in gymnosperms, and the factors responsible for mitochondrial gene content variation in land plants.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Adaption to adverse environments plays an important role in bacterial survival and is receiving increasing globe attention now. Here, cultivable chlorine-injured Pseudomonas aeruginosa, produced on ...the chlorination process, was investigated about their resistance to antibiotics. Then, global transcriptional analyses, quantitative PCR (qPCR) validation and antioxidant enzymes measurement were performed to explore the underlying mechanisms. The results showed that chlorine injury enhanced antibiotic resistance in P. aeruginosa and cultivable chlorine-injured P. aeruginosa exposed to 4 mg/L sodium hypochlorite (half of the lethal dose) improved antibiotic resistance against ceftazidime, chloramphenicol and ampicillin by 1.4–5.6 fold. This increase in antibiotic resistance was not hereditable and over expression of the MexEF-OprN efflux pump resulting from oxidative stress contributed to it. These results demonstrate temporal physiological persistence to antibiotics in cultivable chlorine-injured pathogens, suggesting their survival from adverse environments with antibiotic exposure and thereby posing lasting hazards to human health.
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•Chlorine-injury increased antibiotic resistance in P. aeruginosa.•The mechanism of resistance was overexpression of MexEF-OprN.•This process may increase survival of pathogens in the water treatment system.
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•Threatened conifers endemic to China were mainly distributed in mountainous areas.•The Western Sichuan Plateau is the most important conservation priority area.•Richness hotspots ...were predicted to shrink and move northward under climate change.•Species with different distributions required different conservation measures.•Additional field surveys and integration of reserves are needed for protection.
Climate change inevitably affects the geographical distribution of species on earth. Conifers, which are important components of forest tree species, are highly threatened and particularly sensitive to climate change. Approximately 23.6% (145/615 species) of the world’s conifers are native to China, among which 53 species are threatened. Thus, understanding the impact of climate change on the species richness and distribution of threatened conifers endemic to China (hereafter referred to as threatened conifers) is of great importance. Here, we investigated the habitat suitability under present climate conditions and predicted the impact of future climate change on these threatened conifers using species distribution modeling. Combined with the current natural reserve system, we evaluated the conservation effectiveness, determined the key conservation areas, and proposed suggestions for the future protection of these threatened conifers. Our results showed that the threatened conifers were mainly distributed in mountainous areas and climate variables played a major role in the distribution of these threatened conifers. We also found that the richness hotspots were predicted to shrink and move northward with a changing climate. The lowest elevation of threatened conifers predicted to contract their species range mainly occurred below 1000 m or above 2000 m, while most species whose lowest elevations ranged from 1000 to 2000 m were projected to expand their distribution areas under the future climate scenario. Therefore, different conservation measures should be taken for threatened conifers with different distribution patterns. The central Hengduan Mountains and the Western Sichuan Plateau were identified as “areas needing attention” and “areas worth exploring”, respectively, which should be given more attention in future field surveys and conservation efforts. This study highlighted the critical role of these threatened conifers as good indicators for measuring and proposing conservation strategies to minimize the impacts of climate change.
YL-0919 has been identified as a novel dual 5-HT1A partial agonist and serotonin reuptake inhibitor. In the current study, we demonstrated that YL-0919 produced prominent antidepressant-like and ...anxiolytic-like effects in a chronic unpredictable stress （CUS） rat model. Male SD rats were exposed to CUS for 5 weeks; YL-0919 （1.25 and 2.5 mg/kg） or a positive control fluoxetine （Fix, 10 mg/kg） was orally administered daily. YL-0919 or Fix treatment significantly increased the sucrose preference rate, the locomotor activity in an open field test （OFT）, the latency to feed in a novelty-suppressed feeding test （NSFT）, and both the percentage of time spent in the open arms and the number of entries into the open arms in an elevated plus-maze test. YL-0919 or Fix treatment significantly suppressed the serum levels of ACTH and corticosterone in CUS-exposed rats. Additionally, YL-0919 or Fix treatment significantly enhanced the levels of cAMP, the expression of phosphorylated cAMP response element-binding protein （pCREB） and brain-derived neurotrophic factor （BDNF） in the hippocampus of CUS-exposed rats. Similar to Fix, YL-0919 treatment significantly enhanced the dendritic complexity, and increased the number of dendritic nodes as well as the spine length and number of branch nodes in the hippocampal pyramidal neurons of CUS- exposed rats. Overall, our results reveal that YL-0919 suppresses the HPA axis and exerts antidepressant-like and anxiolytic-like effects in CUS-exposed rats, which are associated with the enhanced cAMP signaling and hippocampal dendritic complexity.
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