Mycothiol peroxidase MPx protects Corynebacterium glutamicum against acid stress by scavenging ROS

Objectives

To investigate mycothiol peroxidase (MPx) of Corynebacterium glutamicum that is a novel CysGPx family peroxidase using both the mycoredoxin and thioredoxin reducing systems as proton donors for peroxide detoxification and may be involved in the relief of acid stress.

Results

A Δmpx mutant exhibited significantly decreased resistance to acid stress and markedly increased accumulation of reactive oxygen species (ROS) and protein carbonylation levels in vivo. Over-expression of mpx increased the resistance of C. glutamicum to acid stress by reducing ROS accumulation. The stress-responsive extracytoplasmic function-sigma (ECF-σ) factor, SigH, mediated acid-induced expression of mpx in the wild-type under acid conditions, which in turn directly contributed to tolerance to acid stress.

Conclusion

MPx is essential for combating acid stress by reducing intracellular ROS levels induced by acid stress in C. glutamicum, which adds a new dimension to the general physiological functions of CysGPx.

     

Engineering the intracellular metabolism of <Emphasis Type="Italic">Escherichia coli</Emphasis> to produce gamma-aminobutyric acid by co-localization of GABA shunt enzymes

Objectives

To direct the carbon flux from Krebs cycle into the gamma-aminobutyric acid (GABA) shunt pathway for the production of GABA by protein scaffold introduction in Escherichia coli.

Results

Escherichia coli was engineered to produce GABA from glucose by the co-localization of enzymes succinate semialdehyde dehydrogenase (GadD), GABA aminotransferase (PuuE) and GABA transporter (GadC) by protein scaffold. 0.7 g GABA l^?1 was produced from 10 g glucose l^?1 while no GABA was produced in wild type E. coli. pH 6 and 30 °C were optimum for GABA production, and GABA concentration increased to 1.12 g GABA l^?1 when 20 g glucose l^?1 was used. When competing metabolic networks were inactivated, GABA increased by 24 % (0.87 g GABA l^?1).

Conclusions

The novel GABA production system was constructed by co-localization of GABA shunt enzymes.

     

Microbial Nonlinear Response to a Precipitation Gradient in the Northeastern Tibetan Plateau

The response of soil microbes to global warming, especially their response to precipitation, remains poorly known. The Tibetan Plateau is very sensitive to climate change. In particular, the northeastern margin of the Tibetan Plateau is an interesting area to test the response of soil microbial communities to precipitation, as there is a distinct gradient in annual precipitation from east to west. We collected soil samples along a precipitation gradient in arid and semi-arid areas of the northeastern Tibetan Plateau. Phospholipid fatty acid (PLFA) technology was used to analyze the microbial community structure and total microbial biomass. With declining precipitation, bacterial biomass decreased significantly, whereas fungal biomass did not show an obvious trend; this result indicates that bacteria are more sensitive to mean annual precipitation (MAP). Overall, the biomass of Gram-negative (G^?) bacteria represented up to 82% of the total bacterial biomass. In the high (260–394 mm yr^?1) MAP areas, bacterial biomass was mainly concentrated at the surface and decreased with increasing soil depth (0–40 cm). In contrast, in the low (36–260 mm yr^?1) MAP areas, bacterial biomass was mainly concentrated in the deep soils. The mean annual precipitation was strongly correlated with soil microbial community in space, with microbial communities in the 0–10-cm soil depth most affected by precipitation. Groundwater may impact microbial communities in the 20–40-cm soil depth of this arid and semiarid region. The clustering of the microbial communities was significantly grouped according to the MAP gradient, revealing that MAP is a major driving force of microbial communities in this arid and semi-arid area. The decline in MAP led to a shift in the structure of the microbial community and an overall reduction in microbial biomass.     

Conservation of reef corals in the South China Sea based on species and evolutionary diversity

The South China Sea in the Central Indo-Pacific is a large semi-enclosed marine region that supports an extraordinary diversity of coral reef organisms (including stony corals), which varies spatially across the region. While one-third of the world’s reef corals are known to face heightened extinction risk from global climate and local impacts, prospects for the coral fauna in the South China Sea region amidst these threats remain poorly understood. In this study, we analyse coral species richness, rarity, and phylogenetic diversity among 16 reef areas in the region to estimate changes in species and evolutionary diversity during projected anthropogenic extinctions. Our results show that richness, rarity, and phylogenetic diversity differ considerably among reef areas in the region, and that their outcomes following projected extinctions cannot be predicted by species diversity alone. Although relative rarity and threat levels are high in species-rich areas such as West Malaysia and the Philippines, areas with fewer species such as northern Vietnam and Paracel Islands stand to lose disproportionately large amounts of phylogenetic diversity. Our study quantifies various biodiversity components of each reef area to inform conservation planners and better direct sparse resources to areas where they are needed most. It also provides a critical biological foundation for targeting reefs that should be included in a regional network of marine protected areas in the South China Sea.     

Geographic variation in advertisement calls of a Microhylid frog – testing the role of drift and ecology

Acoustic signals for mating are important traits that could drive population differentiation and speciation. Ecology may play a role in acoustic divergence through direct selection (e.g., local adaptation to abiotic environment), constraint of correlated traits (e.g., acoustic traits linked to another trait under selection), and/or interspecific competition (e.g., character displacement). However, genetic drift alone can also drive acoustic divergence. It is not always easy to differentiate the role of ecology versus drift in acoustic divergence. In this study, we tested the role of ecology and drift in shaping geographic variation in the advertisement calls of Microhyla fissipes. We examined three predictions based on ecological processes: (1) the correlation between temperature and call properties across M. fissipes populations; (2) the correlation between call properties and body size across M. fissipes populations; and (3) reproductive character displacement (RCD) in call properties between M. fissipes populations that are sympatric with and allopatric to a congener M. heymonsi. To test genetic drift, we examined correlations among call divergence, geographic distance, and genetic distance across M. fissipes populations. We recorded the advertisement calls from 11 populations of M. fissipes in Taiwan, five of which are sympatrically distributed with M. heymonsi. We found geographic variation in both temporal and spectral properties of the advertisement calls of M. fissipes. However, the call properties were not correlated with local temperature or the callers' body size. Furthermore, we did not detect RCD. By contrast, call divergence, geographic distance, and genetic distance between M. fissipes populations were all positively correlated. The comparisons between phenotypic Q_st (P_st) and F_st values did not show significant differences, suggesting a role of drift. We concluded that genetic drift, rather than ecological processes, is the more likely driver for the geographic variation in the advertisement calls of M. fissipes.     

Lethal and behavioral sublethal side effects of thiamethoxam on the predator Harmonia axyridis

Thiamethoxam (TMX) is one of the most effective neonicotinoid insecticides for the control of green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and various side effects can be expected in its natural enemies. The multicolored Asian lady beetle or harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is an important predator against M. persicae in greenhouses and fields. In this study, we evaluated the toxicity of TMX to H. axyridis and the effect on the functional response of this predator to M. persicae through three routes of exposure. Acute toxicity bioassays indicated that LC₅₀ values of TMX on H. axyridis through direct residual contact (‘contact’), systemic application (‘systemic’), and leaf‐dip treatment (‘leaf‐dip’) were 18.99, 21.26, and 15.39 mg a.i. l^?1, respectively. The hazard quotient indicated a potential hazard of this agrochemical regardless of the exposure routes. The mortality caused by the lowest rate, 2 mg a.i. l^?1, was not significantly different compared with the control group. For the three routes of sublethal TMX exposure, the type‐II functional response was a good fit to the prey consumption of H. axyridis. Predation was most affected by leaf‐dip treatment, followed by contact and systemic treatments, which had similar effect. For all exposure routes, the predation capacity of the predator recovered quickly after transfer to untreated cabbage leaves. Thiamethoxam applied systemically was the least toxic to H. axyridis and did not affect the functional response of the predator. However, the sublethal effects of TMX through both contact and leaf‐dip application may reduce the population growth of H. axyridis and consequently impair the biological control of M. persicae by this predator. These results illustrate that the assessment of potential effects of TMX on H. axyridis is crucial to develop effective integrated pest management programs for M. persicae in China.     

Increasing the abscisic acid level in maize grains induces precocious maturation by accelerating grain filling and dehydration

Elevated levels of abscisic acid (ABA) are closely associated with cereal grain filling under water deficit. However, grain dehydration during grain filling has received little attention. In this paper, three experiments with drought stress and exogenous ABA treatments were conducted to investigate the relationship between ABA and grain dehydration in maize (Zea mays L.) during the grain-filling period. The results indicated that exogenous ABA application and drought stress led to the same tendency of the grain ABA concentration, carbohydrate concentration and dehydration rate to increase but the moisture content to decrease. Moreover, the time to reach the maximum grain-filling rate was advanced, and the grain-filling period was shortened. In in vitro culture experiments, the sucrose-to-starch conversion was promoted, mainly influenced by sucrose synthase, ADP-glucose pyrophosphorylase (AGPase), and soluble starch synthase during the middle grain-filling stage, and the improvement in starch synthesis was possibly induced by AGPase. Correlation analysis showed that the ABA level was significantly negatively correlated with the moisture content and positively correlated with the starch level. A close and notably negative correlation was observed between the grain moisture content and starch level. In summary, adequate grain ABA promoted sucrose-to-starch conversion, shortened the duration of grain filling and accelerated grain dehydration, resulting in precocious grain maturation.     

宫颈癌中乳头瘤病毒核酸的检测

越来越多的证据表明乳头瘤病毒与人和动物的某些肿瘤有关。近年来证明人的生殖器肿瘤与人的乳头瘤病毒(HPV)有密切关系。例如,Green等人检查了31例宫颈癌和10例阴道肿瘤,其中各2例与人的HPV-10型有共同的核酸序列。Zachow报告了2例