Optimization of inhaled anesthesia for Octodon degus using electroencephalography.

Physiological responses to inhaled anesthetics vary among species. Therefore, a precise anesthetic technique is important for each individual species. In this study, we focused on the degu (Octodon degus), a small herbivorous rodent. Degus have recently begun to be used as laboratory models for brain research because of certain human-like characteristics, such as spontaneous development of Alzheimer's disease. In this study, we evaluated appropriate induction and maintenance anesthesia conditions for isoflurane and sevoflurane in degus by a stimulation test, electroencephalography (EEG), minimum alveolar concentration (MAC), and vital signs. During induction, more rapid time to loss of the righting reflex and deeper anesthesia in degus were observed in isoflurane. The MAC value for degus were 1.75 ± 0.0% in isoflurane and 2.25 ± 0.27% in sevoflurane. Whereas some degus were awake during maintenance anesthesia using both anesthetics at concentrations of ≤2%, no rats were awake when using sevoflurane at a concentration of 2%. The duration of the total flat EEG, a measure of the depth of maintenance anesthesia, was longer for isoflurane than for sevoflurane. Furthermore, higher concentrations of both anesthetics suppressed the respiratory rate in degus. These new findings regarding inhalation anesthesia in degus will contribute to future developments in the fields of laboratory animals and veterinary medicine.

Activational and organizational effects of testosterone on the number of mating partners and reproductive success in males of a social rodent.

The timing of exposure to the steroid hormone, testosterone, produces activational and organizational effects in vertebrates. These activational and organizational effects are hypothesized to relate with the number of female mating partners and reproductive success in males. We tested this hypothesis by examining 151 wild degu (Octodon degus) males across a 10-year study. We quantified the association between adult serum testosterone levels (i.e., an indirect index of adult activational effects) and anogenital distance (AGD) length (i.e., a direct index of fetal organizational effects), and their interaction on the number of female mating partners and reproductive success. We found no evidence of an association between adult male serum testosterone levels and the number of female mating partners, or between adult male serum testosterone levels and reproductive success. However, male AGD was positively associated with reproductive success, but not so with the number of female mating partners. Additionally, the positive association between male AGD and male reproductive success was mediated by the number of mates. Our findings do not support major roles of activational or organizational effects of testosterone on the number of female mating partners and its consequences on male reproductive success. Instead, our results suggest that compared with individual male attributes, the female social environment plays a more important role in driving male reproductive success.

Disseminated histiocytic sarcoma in a degu (Octodon degus).

A 7-year-and-8-month-old, male degu (Octodon degus) with anorexia, depression, and labored breathing was found to have a thoracic effusion and enlargement of the right testis on radiographic examination. Despite treatment, the animal died. At necropsy, hepatomegaly, splenomegaly, and multifocal nodules on the intestinal serosa and mesentery were observed. Histologically, the foci were densely cellular invasive neoplasms composed of sheets of round to polygonal cells, with occasional multinucleated giant cells. Immunohistochemically, the neoplastic cells were immunopositive for ionized calcium-binding adapter molecule 1, human leukocyte antigen-DR, and CD204. These findings were consistent with disseminated histiocytic sarcoma.

Regulator DegU can remarkably influence alkaline protease AprE biosynthesis in Bacillus licheniformis 2709.

Alkaline protease AprE, produced by Bacillus licheniformis 2709 is an important edible hydrolase, which has potential applications in nutrient acquisition and medicine. The expression of AprE is finely regulated by a complex transcriptional regulation system. However, there is little study on transcriptional regulation mechanism of AprE biosynthesis in Bacillus licheniformis, which limits system engineering and further enhancement of AprE. Here, the severely depressed expression of aprE in degU and degS deletion mutants illustrated that the regulator DegU and its phosphorylation played a crucial part in AprE biosynthesis. Further electrophoretic mobility shift assay (EMSA) in vitro indicated that phosphorylated DegU can directly bind to the regulatory region though the DNase I foot-printing experiments failed to observe protected region. The plasmid-mediated overexpression of degU32 (Hy) obviously improved the yield of AprE by 41.6 % compared with the control strain, which demonstrated the importance of phosphorylation state of DegU on the transcription of aprE in vivo. In this study, the putative binding sequence of aprE (5'-TAAAT……AAAAT…….AACAT…TAAAA-3') located upstream -91 to -87 bp, -101 to -97 bp, -195 to -191 bp, -215 to -211 bp of the transcription start site (TSS) in B. licheniformis was computationally identified based on the DNA-binding sites of DegU in Bacillus subtilis. Overall, we systematically investigated the influence of the interplay between phosphorylated DegU and its cognate DNA sequence on expression of aprE, which not only contributes to the further AprE high-production in a genetically modified host in the future, but also significantly increases our understanding of the aprE transcription mechanism.

How the forebrain transitions to adulthood: developmental plasticity markers in a long-lived rodent reveal region diversity and the uniqueness of adolescence.

Maturation of the forebrain involves transitions from higher to lower levels of synaptic plasticity. The timecourse of these changes likely differs between regions, with the stabilization of some networks scaffolding the development of others. To gain better insight into neuroplasticity changes associated with maturation to adulthood, we examined the distribution of two molecular markers for developmental plasticity. We conducted the examination on male and female degus (Octodon degus), a rodent species with a relatively long developmental timecourse that offers a promising model for studying both development and age-related neuropathology. Immunofluorescent staining was used to measure perineuronal nets (PNNs), an extracellular matrix structure that emerges during the closure of critical plasticity periods, as well as microglia, resident immune cells that play a crucial role in synapse remodeling during development. PNNs (putatively restricting plasticity) were found to be higher in non-juvenile (>3 month) degus, while levels of microglia (putatively mediating plasticity) decreased across ages more gradually, and with varying timecourses between regions. Degus also showed notable variation in PNN levels between cortical layers and hippocampal subdivisions that have not been previously reported in other species. These results offer a glimpse into neuroplasticity changes occurring during degu maturation and highlight adolescence as a unique phase of neuroplasticity, in which PNNs have been established but microglia remain relatively high.

First International Conference on Unconventional Animal Models of Alzheimer's Disease and Aging.

The first International Conference on Unconventional Animal Models of Alzheimer's Disease and Aging (UAMAA) took place on December 13-16, 2023, in Santiago, Chile. The Alzheimer's disease (AD) research field is currently in search for new and unconventional models that could hold greater translational potential than transgenic mouse models. Thus this UAMAA conference is timely and significant. The event consisted of 6 sessions with talks from 28 world-class scientists from all over the world. These animal models of interest include the degu (Octodon degu), the dog (Canis familiaris), and certain species of nonhuman primates that may better recapitulate neuropathology and cognitive impairments in human AD. Our conference has provided a formal forum to discuss and highlight new research directions, alternative animal models, and innovative approaches for the AD and aging research field.

Efficacy of the combination of semaglutide, insulin degludec, and metformin in the treatment of type 2 diabetes mellitus and poor glycemic control accompanied by overweight or obesity / 中国基层医药

Objective:To investigate the efficacy of the combination of semaglutide, insulin degludec, and metformin in the treatment of type 2 diabetes mellitus and poor glycemic control accompanied by overweight or obesity.Methods:A total of 160 patients with type 2 diabetes mellitus and poor glycemic control accompanied by overweight or obesity were included in this case-control study after receiving treatment at Bayannur Hospital from April 2022 to March 2023. These patients were divided into a control group and an observation group based on different treatment regimens, with 80 patients in each group. The control group was treated with degludec insulin combined with metformin, while the observation group was treated with semaglutide, degludec insulin, and metformin. The treatment lasted for 12 weeks in both groups. The changes in fasting plasma glucose, 2-hour postprandial blood glucose (2 h PG), glycosylated hemoglobin, time in range for 2 h PG, fasting insulin, Homeostatic Model Assessment for Insulin Resistance index, body mass index, and visceral fat area and adverse reactions were monitored.Results:The overall response rate in the observation group was 100% (80/80), which was significantly higher than 97.5% (78/80) in the control group (χ 2 = 11.03, P < 0.05). After treatment, the levels of 2 h PG, glycosylated hemoglobin, fasting insulin, Homeostatic Model Assessment for Insulin Resistance index, body mass index, visceral fat area in the observation group were (7.35 ± 0.17) mmol/L, (6.08 ± 0.24)%, (10.30 ± 2.58) μU/mL,(2.69 ± 0.66), (24.40 ± 0.68) kg/m 2, (80.20 ± 8.94) cm 2, respectively, which were significantly lower than (7.92 ± 0.24) mmol/L, (6.34 ± 0.27)%,(13.71 ± 3.13) μU/mL,(3.57 ± 0.83), (26.77 ± 3.49) kg/m 2, (116.12 ± 34.09) cm 2 respectively in the control group ( t = -0.73, -3.74, -4.20, -4.15, -3.35, -5.10, all P < 0.05). The time in range for 2 h PG in the observation group was (72.68 ± 4.09)%, which was significantly higher than (50.16 ± 10.00)% in the control group ( t = -10.42, P < 0.05). The incidence of adverse reactions in the observation group was 3.8% (3/80), which was slightly, but not significantly, higher than 2.5% (2/80) in the control group ( P > 0.05). Conclusion:The combination of semaglutide, degludec insulin, and metformin demonstrates an ideal clinical effect in the treatment of type 2 diabetes mellitus and poor glycemic control accompanied by overweight or obesity. This combined approach can effectively regulate fasting and postprandial blood glucose levels, markedly decrease the body mass index and visceral fat levels, and improve insulin resistance while not significantly increasing the incidence of adverse reactions.

Rodent Pediatrics.

This article reviews the development, hand-rearing, feeding, housing, and social behavior of common pet rodent species (rats, mice, hamsters, gerbils, guinea pigs, chinchillas, and degus). In addition, common gastrointestinal, respiratory, cardiovascular, dermatologic, musculoskeletal, neurologic, and ophthalmic disorders in pediatric pet rodents are reviewed. Preventative care and indications for spaying and neutering are discussed.

DegU-mediated suppression of carbohydrate uptake in Listeria monocytogenes increases adaptation to oxidative stress.

The foodborne bacterial pathogen Listeria monocytogenes exhibits remarkable survival capabilities under challenging conditions, severely threatening food safety and human health. The orphan regulator DegU is a pleiotropic regulator required for bacterial environmental adaptation. However, the specific mechanism of how DegU participates in oxidative stress tolerance remains unknown in L. monocytogenes. In this study, we demonstrate that DegU suppresses carbohydrate uptake under stress conditions by altering global transcriptional profiles, particularly by modulating the transcription of the phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS)-related genes, such as ptsH, ptsI, and hprK. Specifically, in the absence of degU, the transcripts of ptsI are significantly upregulated and those of hprK are significantly downregulated in response to copper ion-induced stress. Overexpression of ptsI significantly increases bacterial growth in vitro, while overexpression of hprK leads to a decrease in growth. We further demonstrate that DegU directly senses oxidative stress, downregulates ptsI transcription, and upregulates hprK transcription. Additionally, through an electrophoretic mobility shift assay, we demonstrate that DegU directly regulates the transcription of ptsI and hprK by binding to specific regions within their respective promoter sequences. Notably, the putative pivotal DegU binding sequence for ptsI is located from 38 to 68 base pairs upstream of the ptsH transcription start site (TSS), whereas for hprK, it is mapped from 36 to 124 base pairs upstream of the hprK TSS. In summary, we elucidate that DegU plays a significant role in suppressing carbohydrate uptake in response to oxidative stress through the direct regulation of ptsI and hprK.ImportanceUnderstanding the adaptive mechanisms employed by Listeria monocytogenes in harsh environments is of great significance. This study focuses on investigating the role of DegU in response to oxidative stress by examining global transcriptional profiles. The results highlight the noteworthy involvement of DegU in this stress response. Specifically, DegU acts as a direct sensor of oxidative stress, leading to the modulation of gene transcription. It downregulates ptsI transcription while it upregulates hprK transcription through direct binding to their promoters. Consequently, these regulatory actions impede bacterial growth, providing a defense mechanism against stress-induced damage. These findings gained from this study may have broader implications, serving as a reference for studying adaptive mechanisms in other pathogenic bacteria and aiding in the development of targeted strategies to control L. monocytogenes and ensure food safety.

A comparison of commercially available feeds for rabbits, guinea pigs, chinchillas and degus with evidence of their diet and feeding behaviour in natural habitats.

INTRODUCTION: A large variety of pet feeds is commercially available for pet herbivores; these feeds may differ in nutrient composition from the natural diet, and may trigger different feeding behaviours than observed in natural habitats. Here, we surveyed literature on the natural diet and activity budget of rabbits (Oryctolagus cuniculus), guinea pigs (Cavia porcellus), chinchilla (Chinchilla lanigera) and degus (Octodon degus), as well as 260 compound feeds commercially available for these species between 1982 and 2020. The species are classified as herbivores, with available data on natural diets suggesting a crude fibre (CF) level of approximately 250 g/kg dry matter (DM), natural feeding activity at a magnitude of 4-7 h per day, with distinctively shorter feeding when fed on compound pet feeds. Only for a minority of feeds did the first 5 listed ingredients not include a starchy ingredient, or only ingredients not considered suitable for human consumption. The percentage of feeds whose CF level was less than 150 g/kg DM was 22 % for production rabbits, 18 % for pet rabbits, 26 % for guinea pigs, 18 % for chinchillas and 14 % for degus; in other words, a majority of currently marketed products have CF levels in accord with published recommendations, even if that means a discrepancy to natural diets. Screening the producers' feeding instructions suggests they should generally not be followed uncritically. No temporal trends in the CF levels of these diets was evident. There is no consensus whether only products resembling natural diet items should be included in pet feeds, or whether vegetable byproducts not edible by humans should also be included. The observed practice of pet feed composition largely did not follow either concept, questioning the general rationale of pet feed composition. Whole forage like hay is recommended as the main diet component for these species, and 76 % of pet feed products noted that hay should be fed in the feeding instructions.

INTRODUCTION: Une grande variété d'aliments pour animaux de compagnie est disponible dans le commerce pour les herbivores de compagnie; ces aliments peuvent différer du régime naturel dans leur composition en nutriments et peuvent déclencher des comportements alimentaires différents de ceux observés dans les habitats naturels. Nous avons étudié la littérature sur le régime alimentaire naturel et le budget d'activité des lapins (Oryctolagus cuniculus), des cochons d'Inde (Cavia porcellus), des chinchillas (Chinchilla lanigera) et des dégus (Octodon degus), ainsi que 260 aliments composés disponibles dans le commerce pour ces espèces entre 1982 et 2020. Les espèces sont classées comme herbivores et les données disponibles sur leurs régimes alimentaires naturels suggèrent une teneur en fibres brutes (FB) d'environ 250 g/kg de matière sèche (MS), une activité alimentaire naturelle de l'ordre de 4 à 7 heures par jour, avec une durée d'alimentation nettement plus courte lorsque l'animal est nourri avec des aliments composés pour animaux de compagnie. Ce n'est que pour une minorité d'aliments que les cinq premiers ingrédients énumérés ne comprenaient pas d'ingrédient amylacé, ou seulement des ingrédients considérés comme impropres à la consommation humaine. Le pourcentage d'aliments dont la teneur en FB était inférieure à 150 g/kg MS était de 22 % pour les lapins de production, 18 % pour les lapins de compagnie, 26 % pour les cochons d'Inde, 18 % pour les chinchillas et 14 % pour les dégus ; en d'autres termes, la majorité des produits actuellement commercialisés ont des teneurs en FB conformes aux recommandations publiées, même si cela signifie une divergence par rapport aux régimes naturels. L'examen des instructions d'alimentation des producteurs suggère qu'elles ne doivent généralement pas être suivies sans discernement. Aucune évolution temporelle dans les teneurs en FB de ces régimes n'a été mise en évidence. Il n'y a pas de consensus sur la question de savoir si seuls les produits ressemblant à des aliments naturels doivent être inclus dans les aliments pour animaux de compagnie ou si des sous-produits végétaux non comestibles pour l'homme doivent également être inclus. La pratique observée en matière de composition des aliments pour animaux de compagnie n'a en grande partie respecté aucun de ces deux concepts, ce qui remet en question la logique générale de la composition de ces aliments. Les fourrages entiers, comme le foin, sont recommandés comme principale composante de l'alimentation de ces espèces et 76 % des produits alimentaires pour animaux de compagnie indiquent, dans les instructions d'alimentation, que du foin doit être donné.

Tuning transcription factor DegU for developing extracellular protease overproducer in Bacillus pumilus.

BACKGROUND: Global transcription machinery engineering (gTME) is an effective approach employed in strain engineering to rewire gene expression and reshape cellular metabolic fluxes at the transcriptional level. RESULTS: In this study, we utilized gTME to engineer the positive transcription factor, DegU, in the regulation network of major alkaline protease, AprE, in Bacillus pumilus. To validate its functionality when incorporated into the chromosome, we performed several experiments. First, three negative transcription factors, SinR, Hpr, and AbrB, were deleted to promote AprE synthesis. Second, several hyper-active DegU mutants, designated as DegU(hy), were selected using the fluorescence colorimetric method with the host of the Bacillus subtilis ΔdegSU mutant. Third, we integrated a screened degU(L113F) sequence into the chromosome of the Δhpr mutant of B. pumilus SCU11 to replace the original degU gene using a CRISPR/Cas9 system. Finally, based on transcriptomic and molecular dynamic analysis, we interpreted the possible mechanism of high-yielding and found that the strain produced alkaline proteases 2.7 times higher than that of the control strain (B. pumilus SCU11) in LB medium. CONCLUSION: Our findings serve as a proof-of-concept that tuning the global regulator is feasible and crucial for improving the production performance of B. pumilus. Additionally, our study established a paradigm for gene function research in strains that are difficult to handle.

Quorum sensing system effectively enhances DegU-mediated degradation of pyrethroids by Bacillus subtilis.

The contamination of the natural environment is a growing concern that threatens all life forms, including microorganisms. Bacteria protect themselves by initiating quorum sensing (QS), a bacterial cell-cell communication, to generate adaptive responses to these pollutants. Bacillus subtilis has a typical QS ComQXPA system that regulates the phosphorylation of the transcription factor DegU (DegU-P), and thus can mediate the expression of various downstream genes under different stress conditions. Herein, we found that cesB, a gene of Bacillus subtilis 168, plays a key role in pyrethroid degradation, and cesB-mediated degradation could be enhanced by coordinating with the ComX communication system. Using ß-cypermethrin (ß-CP) as a paradigm, we demonstrated that DegU-P increased upon exposure to ß-CP, thus facilitating ß-CP degradation by binding to the upstream regulatory regions of cesB, leading to the activation of the expression of cesB. Further, we showed that the expression of different levels of phosphorylated DegU in a degU deletion strain resulted in varying degrees of ß-CP degradation efficiency, with phosphorylated DegUH12L achieving 78.39% degradation efficiency on the first day, surpassing the 56.27% degradation efficiency in the wild type strain. Consequently, based on the conserved regulatory mechanism of ComQXPA system, we propose that DegU-P-dependent regulation serves as a conserved defense mechanism owing to its ability to fine-tune the expression of genes involved in the degradation of pollutants upon exposure to different pesticides.

The Small Non-coding RNA rli106 Contributes to the Environmental Adaptation and Pathogenicity of Listeria Monocytogenes.

Introduction: Listeria monocytogenes (LM) is an important food-borne pathogen, and the risk of its ingestion is a serious public health issue. The better its environmental adaptation mechanisms and pathogenicity are understood, the better the risk it poses can be countered. The regulatory role of the small non-coding RNA (sRNA) rli106 in the environmental adaptation and pathogenicity of LM is still unclear and this study investigated that role through its biological function. Material and Methods: An LM-Δrli106 gene deletion strain and an LM-Δrli106/rli106 gene complementation strain were constructed using the homologous recombination technique. Then, the adaptation of these strains to temperature, alkalinity, acidity, salinity, ethanol and oxidative stressors, their biofilm-forming ability and their pathogenicity in mice were investigated to show the regulatory roles of sRNA rli106 in LM. The target gene of rli106 was also predicted, and the interaction between it and rli106 was verified by a two-plasmid co-expressing system based on E.coli and Western blot analysis. Results: The adaptation of LM-Δrli106 to environmental stressors of pH 9, 5% NaCl and 8% NaCl, 3.8% ethanol and 5 mM H2O2 was significantly reduced when compared to the parental (LM EGD-e) and complementation strains. Also, the biofilm formation, cell adhesion, invasion, intracellular proliferation and pathogenicity of LM-Δrli106 in mice were significantly reduced. The results of two-plasmid co-expression and Western blot showed that rli106 can interact with the mRNA of the predicted DegU target gene. Conclusion: The sRNA rli106 may positively regulate the expression of the DegU gene in LM. This study sheds light on its regulatory roles in environmental adaptation and pathogenicity, providing new insights into the molecular mechanism of sRNA mediation in LM .

Rodent Dermatology.

This article reviews the most common dermatologic conditions of the pet rodent population, including the prevalence, clinical signs, diagnosis, and treatment recommendations.

Arterial branching pattern of the cranial mesenteric artery in the degu (Octodon degus).

BACKGROUND: The cranial mesenteric artery exhibits a species-specific ramification pattern that adapts to the morphology of the intestinal tract. The degu is a strictly herbivorous rodent with a well-developed large intestine with a spiral loop in the ascending colon; therefore, the cranial mesenteric artery likely demonstrates a degu-specific ramification pattern. Thus, we traced the cranial mesenteric artery to establish the detailed ramification pattern of the branches. METHODS: Eighteen male degus were injected with 0.3-0.8 ml of a latex mixture and water at a 1:1 ratio in conjunction with red acrylic paint coloring using a catheter inserted into the thoracic aorta. The cranial mesenteric artery was traced using a surgical microscope and photographed using a digital camera. RESULTS: The arteries emerging from the cranial mesenteric artery exhibited frequent variations in number, distribution area, anastomosis pattern, and branching order. In the most frequent cases (22%), the cranial mesenteric artery sequentially gave rise to caudal pancreaticoduodenal, middle colic, right colic, jejunal, and ileocolic arteries. The right and middle colic arteries exhibited four different ramification patterns. In the most common cases (67%), the middle and right colic arteries emerged independently from the cranial mesenteric artery. The former was distributed to the transverse and descending colon, whereas the latter sent branches to the spiral loop of the ascending colon. CONCLUSIONS: The complex ramification pattern of the right colic artery in the degu may be an adaptation to the characteristic running pattern of the ascending colon. Thus, we present the first comprehensive report of the arterial branching pattern of the cranial mesenteric artery in the degu.

Comparison of the retrosplenial cortex size between the degu (Octodon degus) and the Wistar rat (Rattus norvegicus).

The degu (Octodon degus) is a rodent that normally constructs burrows for nesting and rearing. To navigate inside these burrows, degus may use idiothetic and/or sensory cues more than visual information, which is less effective in burrows. Spatial information for navigation is processed in several key brain regions including the retrosplenial cortex (RS). However, the structural characteristics of the degu RS have not been previously reported. The present study measured the sizes of the RS and constituent areas 29 and 30 in the degu, and compared these to those found in the rat, which is a terrestrial rodent. The proportion of the rostrocaudal length of the entire RS relative to that of the entire cortex was significantly larger in degus versus rats. The proportion of the rostrocaudal length of the RS at levels rostral to the splenium of the corpus callosum relative to that of the entire cortex was also significantly larger in degus versus rats. Furthermore, the ratio of the estimated volume of area 29 relative to that of area 30 was significantly larger in degus versus rats. These results show that the degu has a rostrocaudally longer rostral RS with a larger area 29 compared to the rat, which suggests that these structural features may be relevant to differences in spatial information processing between the fossorial degu and terrestrial rat.

Regulating Pathways of Bacillus pumilus Adamalysin-like Metalloendopeptidase Expression.

The minor secreted proteinase of B. pumilus 3-19 MprBp classified as the unique bacillary adamalysin-like enzyme of the metzincin clan. The functional role of this metalloproteinase in the bacilli cells is not clear. Analysis of the regulatory region of the mprBp gene showed the presence of potential binding sites to the transcription regulatory factors Spo0A (sporulation) and DegU (biodegradation). The study of mprBp activity in mutant strains of B. subtilis defective in regulatory proteins of the Spo- and Deg-systems showed that the mprBp gene is partially controlled by the Deg-system of signal transduction and independent from the Spo-system.

Cognitively impaired aged Octodon degus recapitulate major neuropathological features of sporadic Alzheimer's disease.

The long-lived Chilean rodent (Octodon degus) has been reported to show spontaneous age-dependent neuropathology and cognitive impairments similar to those observed in human AD. However, the handful of published papers on degus of differing genetic backgrounds yield inconsistent findings about sporadic AD-like pathological features, with notably differing results between lab in-bred degus versus outbred degus. This motivates more extensive characterization of spontaneously occurring AD-like pathology and behavior in degus. In the present study, we show AD-like neuropathological markers in the form of amyloid deposits and tau abnormalities in a cognitively impaired subset of aged outbred degus. Compared to the aged degus that show normal burrowing behavior, the age-matched degus with burrowing behavior deficits correlatively exhibit detectable human AD-like Aß deposits and tau neuropathology, along with neuroinflammatory markers that include enhanced microglial activation and higher numbers of reactive astrocytes in the brain. This subset of cognitively impaired aged degus also exhibits cerebral amyloid angiopathy and tauopathy. We find robust neurodegenerative features in behaviorally deficient aged degus, including hippocampal neuronal loss, altered parvalbumin and perineuronal net staining in the cortex, and increased c-Fos neuronal activation in the cortex that is consistent with the neural circuit hyperactivity reported in human AD patients. By focusing on the subset of aged degus that show AD-like behavioral deficits and correlative neuropathology, our findings establish outbred degus as a natural model of sporadic AD and demonstrate the potential importance of wild-type outbred genetic backgrounds for AD pathogenesis.

Poly-γ-Glutamic Acid Production by Engineering a DegU Quorum-Sensing Circuit in Bacillus subtilis.

As a natural biological macromolecule, γ-polyglutamic acid (γ-PGA) plays a significant role in medicine, food, and cosmetic industries owing to its unique properties of biocompatibility, biodegradability, water solubility, and viscosity. Although many strategies have been adopted to increase the yield of γ-PGA in Bacillus subtilis, the effectiveness of these common approaches is not high because the strong viscosity affects cell growth. However, dynamic regulation based on quorum sensing (QS) has been extensively applied as a fundamental tool for fine-tuning gene expression in reaction to changes in cell density without adding expensive inducers. A modular PhrQ-RapQ-DegU QS system is developed based on promoter PD4, which is upregulated by phosphorylated DegU (DegU-P). In this study, first, we analyzed the DegU-based gene expression regulation system in B. subtilis 168. We constructed a promoter library of different abilities, selected suitable promoters from the library, and performed mutation screening on the selected promoters and degU region. Furthermore, we constructed a PhrQ-RapQ-DegU QS system to dynamically control the synthesis of γ-PGA in BS168. Cell growth and efficient synthesis of the target product can be dynamically balanced by the QS system. Our dynamic adjustment approach increased the yield of γ-PGA to 6.53-fold of that by static regulation in a 3 L bioreactor, which verified the effectiveness of this strategy. In summary, the PhrQ-RapQ-DegU QS system has been successfully integrated with biocatalytic functions to achieve dynamic metabolic pathway control in BS168, which can be stretched to a large number of microorganisms to fine-tune gene expression and enhance the production of metabolites.

Transcription factor DegU-mediated multi-pathway regulation on lichenysin biosynthesis in Bacillus licheniformis.

Lichenysin, producted by Bacillus licheniformis, is an important cyclic lipopeptide biosurfactant, which has potential applications in oil exploitation, drug development, biological control of agriculture and bioremediation. While studies are lacking on metabolism regulation of lichenysin biosynthesis, which limits metabolic engineering and large-scale production of lichenysin. In this study, the yield of lichenysin was improved obviously by 13.6 folds to 2.18 ± 0.03 g/L in degU deletion strain (WX02△degU) compared with the wild-type strain (WX02) and completely inhibited in degU overexpressed strain (WX02/pHY-degU). We further proved that DegU, a transcription factor plays a significant role in multicellular behavior, is a key negative regulator of lichenysin synthesis lchA operon. But interestingly, lichenysin yield was still inhibited by overexpressing DegU in the promoter-substituted strain (WX02-PP43lch), in which promoter of lchA operon cannot be controlled by DegU. Thus, through 13C-metabolic flux analysis, we found that deletion of degU also enhanced glucose uptake, branched chain amino acid synthesis, and fatty acid synthesis, while decrease acetoin synthesis, which is beneficial for the supply of lichenysin precursors. Further experiments demonstrate that DegU regulates these pathways by binding to the promoter regions of related genes. Overall, we systematically investigated the multi-pathway regulation network mediated by DegU on lichenysin biosynthesis, which not only contributes to the further metabolic engineering for lichenysin high-production, but sheds light on studies of transcription factor regulation.