The gut microbiota is emerging as a new factor in the development of obesity. Many studies have described changes in microbiota composition in response to obesity and high fat diet (HFD) at the phylum level. In this study we used 16s RNA high throughput sequencing on faecal samples from rats chronically fed HFD or control chow (n = 10 per group, 16 weeks) to investigate changes in gut microbiota composition at the species level. 53.17% dissimilarity between groups was observed at the species level. Lactobacillus intestinalis dominated the microbiota in rats under the chow diet. However this species was considerably less abundant in rats fed HFD (P<0.0001), this being compensated by an increase in abundance of propionate/acetate producing species. To further understand the influence of these species on the development of the obese phenotype, we correlated their abundance with metabolic parameters associated with obesity. Of the taxa contributing the most to dissimilarity between groups, 10 presented significant correlations with at least one of the tested parameters, three of them correlated positively with all metabolic parameters: Phascolarctobacterium, Proteus mirabilis and Veillonellaceae, all propionate/acetate producers. Lactobacillus intestinalis was the only species whose abundance was negatively correlated with change in body weight and fat mass. This species decreased drastically in response to HFD, favouring propionate/acetate producing bacterial species whose abundance was strongly correlated with adiposity and deterioration of metabolic factors. Our observations suggest that these species may play a key role in the development of obesity in response to a HFD. 相似文献
Freshwater anostracans inhabit ephemeral water bodies in which as the water level decreases due to evaporation the salt concentration increases. Thus, for most anostracans salinity becomes the major stress factor.
Results
We tested five concentrations of NaCl (0 to 8 g/l) on the life table demography of Branchipus schaefferi fed Chlorella (alga). Age-specific survivorship curves of male and female B. schaefferi showed nearly a similar pattern in that increased salt concentration resulted in decreased survivorship. The age-specific reproduction (mx) of females showed several peaks of cyst production at 0 and 1 g/l salinity while in treatments containing salt at 4 or 8 g/l, there were fewer peaks. Average lifespan, life expectancy at birth, gross and net reproductive rates, generation time and the rate of population increase were all significantly influenced by the salt concentration in the medium. The highest value of net reproductive rate (970 cysts/female) was in treatments containing 0 g/l of salt, while the lowest was 13 cysts/female at 8 g/l. The rate of population increase (r) varied from 0.52 to 0.32 per day depending on the salt concentration in the medium.
Conclusion
The low survival and offspring production of B. schaefferi at higher salinity levels suggests that this species is unlikely to colonize inland saline water bodies. Therefore, the temporary ponds in which it is found, proper conservative measures must be taken to protect this species. 相似文献
Quorum sensing is a process of bacterial cell-to-cell communication involving the production and detection of extracellular signaling molecules called autoinducers. Quorum sensing allows populations of bacteria to collectively control gene expression, and thus synchronize group behavior. Processes controlled by quorum sensing are typically ones that are unproductive unless many bacteria act together. Most autoinducers enable intraspecies communication; however, a recently discovered autoinducer AI-2 has been proposed to serve as a 'universal signal' for interspecies communication. Studies suggest that AI-2 encodes information in addition to specifics about cell number. 相似文献
Nitrogen fixation and assimilation in nodules and roots were studied in soybean (Glycine max L.) exposed to different levels of aluminium (Al) stress (0, 50, 200 and 500 μM). Al at 500 μM induced oxidative stress,
which became evident from an increase in lipid peroxidation accompanied by a concomitant decline in antioxidant enzyme activities
and leghaemoglobin breakdown. Consequently, there was also a reduction in nitrogenase activity. However, the leghaemoglobin
levels and nitrogenase activity were unexpectedly found to be higher in nodules when the plants were treated with 200 μM Al.
Of the enzymes involved in nitrogen assimilation, the activity of glutamate dehydrogenase-NADH was reduced in nodules under
Al stress, but it was significantly higher in roots at 500 μM Al as compared to that in the control. In nodules, the glutamine
synthetase/glutamate synthase-NADH pathway, assayed in terms of activity and expression of both the enzymes, was inhibited
at >50 μM Al; but in roots this inhibitory effect was apparent only at 500 μM Al. No significant changes in ammonium and protein
contents were recorded in the nodules or roots when the plants were treated with 50 μM Al. However, Al at ≥200 μM significantly
increased the ammonium levels and decreased the protein content in the nodules. But these contrasting effects on ammonium
and protein contents due to Al stress were observed in the roots only at 500 μM Al. The results suggest that the effect of
Al stress on nitrogen assimilation is more conspicuous in nodules than that in the roots of soybean plants. 相似文献
About half of people with trisomy 21 have a congenital heart defect (CHD), whereas the remainder have a structurally normal heart, demonstrating that trisomy 21 is a significant risk factor but is not causal for abnormal heart development. Atrioventricular septal defects (AVSD) are the most commonly occurring heart defects in Down syndrome (DS), and ∼65% of all AVSD is associated with DS. We used a candidate-gene approach among individuals with DS and complete AVSD (cases = 141) and DS with no CHD (controls = 141) to determine whether rare genetic variants in genes involved in atrioventricular valvuloseptal morphogenesis contribute to AVSD in this sensitized population. We found a significant excess (p < 0.0001) of variants predicted to be deleterious in cases compared to controls. At the most stringent level of filtering, we found potentially damaging variants in nearly 20% of cases but fewer than 3% of controls. The variants with the highest probability of being damaging in cases only were found in six genes: COL6A1, COL6A2, CRELD1, FBLN2, FRZB, and GATA5. Several of the case-specific variants were recurrent in unrelated individuals, occurring in 10% of cases studied. No variants with an equal probability of being damaging were found in controls, demonstrating a highly specific association with AVSD. Of note, all of these genes are in the VEGF-A pathway, even though the candidate genes analyzed in this study represented numerous biochemical and developmental pathways, suggesting that rare variants in the VEGF-A pathway might contribute to the genetic underpinnings of AVSD in humans. 相似文献
1. The praying mantis possesses a single ear located in the ventral midline of the metathorax. We have studied the mantis' auditory nervous system using both extracellular and intracellular techniques and have identified anatomically and physiologically a mirror-image pair of interneurons (MR-501-T3) in the metathoracic ganglion that mediates ultrasonic hearing. 2. MR-501-T3 is tuned broadly to ultrasound with best sensitivity (55-60 dB SPL) between 25 and 45 kHz. Its tuning matches closely that of the whole tympanal nerve. 3. The physiological responses of MR-501-T3 are characterized by: (1) a phasic-tonic firing pattern with a distinctive initial burst at 500-800 spikes/s; (2) minimum latencies of 8-12 ms; (3) no spontaneous activity; (4) sigmoid intensity response curves with a small (10 dB) dynamic range; (5) accurate coding of stimulus duration and of repetition rates up to 60 pps. 4. The ascending axon of MR-501-T3 conducts action potentials at 4 m/s, a rate comparable with some giant fiber systems. 5. MR-501-T3 shows no directional capability. Sound from right and left produce identical responses in both cells of the pair. Neither cutting one tympanal nerve nor removing one hemi-ear leads to different responses in the two cells indicating that they must receive a common input, either from the auditory afferents or from interneurons. We present evidence that the two cells are not directly connected. 6. MR-501-T3 is a large, symmetrical cell with its processes primarily in the intermediate neuropil (lateral ring tract). Its integration segment crosses the midline in the supramedian commissure, and the cell body lies dorsally near the entrance of the leg nerve. The axon travels in the dorsal lateral tract and is one of the largest (17 microns) in the connective. 7. Given the strong anatomical similarities between MR-501-T3 and the G and B cells of the locust, these cells may be homologous. 8. We present arguments based on our physiological results and existing behavioral data that MR-501-T3 is part of an ultrasonic warning/escape system in the mantis. As in moths, lacewings, and crickets, this system may provide a defense against nocturnally foraging bats. 相似文献
The genus Streptococcus includes various species, remarkably different in their behavior, applications, virulence, and safety. Taxonomically Streptococcus infantarius subsp. infantarius belonging to the Streptococcus bovis group, which includes several pathogen species, however, has been found as predominant species in some African dairy products that are widely consumed and considered to be safe. Streptococcus infantarius subsp. infantarius’ safety may be questioned due to the association of this species with clinical cases. In this study, isolates from dairy origin were selected based on their bacteriocinogenic potential and differentiated by their RAPD-PCR profiles. Two strains were identified by 16S rRNA sequencing as St. infantarius subsp. infantarius and investigated regarding their potential beneficial properties and factors related to virulence and safety. A series of in vitro tests included properties related to survival in the gastrointestinal tract and beneficial intestinal activities. Production of bacteriocin/s, detection of related genes, and partial characterization of expressed antimicrobial protein were evaluated. Genes related to folate biosynthesis were detected in both studied strains. Evaluation of physiological tests related to strains virulence, adhesion, and resistance to antibiotics and detections of virulence and biogenic amines production-related genes were also investigated. Taking in consideration all the aspects of the specific nature of St. infantarius subsp. infantarius K1–4 and K5–1 (beneficial properties and virulence characteristics), both strains cannot be considered safe for human or other animals application, even though they have been isolated from dairy products. This study is highlighting the importance of evaluation for presence of potential virulence factors in newly characterized strains in order to be confident in their safety.
Experimental and Applied Acarology - Tenuipalpid mites of the genus Brevipalpus are of significant economic and quarantine importance in agriculture. They can damage and vector phytopathogenic... 相似文献