The role of protein modifications in senescence of freeze-dried Acetobacter senegalensis during storage.

BACKGROUND: Loss of viability is one of the most important problems during starter culture production. Previous research has mostly focused on the production process of bacterial starters, but there are few studies about cellular protein deterioration causing cell defectiveness during storage. In the present study, we investigated the influence of storage temperature (-21, 4, 35°C) on the cellular protein modifications which may contribute to the senescence of freeze-dried Acetobacter senegalensis. RESULTS: Heterogeneous populations composed of culturable cells, viable but non-culturable cells (VBNC) and dead cells were generated when freeze-dried cells were kept at -21 and 4°C for 12 months whereas higher storage temperature (35°C) mainly caused death of the cells. The analysis of stored cell proteome by 2D-DiGE demonstrated a modified pattern of protein profile for cell kept at 4 and 35°C due to the formation of protein spot trains and shift of Isoelectric point (pI). Quantification of carbonylated protein by ELISA showed that the cells stored at 4 and 35°C had higher carbonylated protein contents than fresh cells. 2D-DiGE followed by Western blotting also confirmed the carbonylation of cellular proteins involved in translation process and energy generation. The auto-fluorescent feature of cells kept at 35°C increased significantly which may be an indication of protein glycation during storage. In addition, the percentage of cellular unsaturated fatty acid and the solubility of cellular proteins decreased upon storage of cells at higher temperature suggesting that peroxidation of fatty acids and possibly protein lipidation and oxidation occurred. CONCLUSIONS: High storage temperature induces some deteriorative reactions such as protein oxidation, lipidation and glycation which may cause further protein modifications like pI-shift, and protein insolubility. These modifications can partly account for the changes in cell viability. It can also be deduced that even moderate carbonylation of some critical cellular proteins (like ribosomal proteins) may lead to VBNC formation or death of freeze-dried bacteria. Moreover, it seems that other mechanisms of biomolecule deterioration preceding protein carbonylation lead to VBNC formation under very low storage temperature.

Technical-economic framework for designing of water pumping system based on photovoltaic clean energy with water storage for drinking application.

In this paper, the technical-economic framework for designing of water pumping system based on photovoltaic clean energy with water tank storage is presented to supply drinking water of customers for remote areas. The objective function is to minimize the net present cost (NPC) (as economic index) including initial investment costs, maintenance, and replacement costs, and reliability constraint is defined as customer's water not supplied probability (CWNSP) as technical index. A meta-heuristic intelligent water drops algorithm (IWDA) is proposed to optimize the solar water pumping system considering NPC and CWNSP with high accuracy and speed of optimization in achieving the global solution. The simulation results show that the proposed method is capable of responding to customer's water demand by optimally sizing components and water storage tank based on IWDA which is inspired based on flowing the water drops in rivers by achieving the lowest cost with optimal reliability. The NPC of the system with CWNSP equal to 3.17 % is obtained 0.24 M$ for 6-m-high water extraction. The results showed that with increasing the water extraction height, the NPC increased, and the reliability also weakened. Moreover, the superiority of the IWDA is confirmed compared with particle swarm optimization (PSO) in designing a water pumping system with the lowest NPC.

Correcting Instrumental Variables Estimators for Systematic Measurement Error.

Instrumental variables (IV) estimators are well established to correct for measurement error on exposure in a broad range of fields. In a distinct prominent stream of research IV's are becoming increasingly popular for estimating causal effects of exposure on outcome since they allow for unmeasured confounders which are hard to avoid. Because many causal questions emerge from data which suffer severe measurement error problems, we combine both IV approaches in this article to correct IV-based causal effect estimators in linear (structural mean) models for possibly systematic measurement error on the exposure. The estimators rely on the presence of a baseline measurement which is associated with the observed exposure and known not to modify the target effect. Simulation studies and the analysis of a small blood pressure reduction trial (n = 105) with treatment noncompliance confirm the adequate performance of our estimators in finite samples. Our results also demonstrate that incorporating limited prior knowledge about a weakly identified parameter (such as the error mean) in a frequentist analysis can yield substantial improvements.

How weight during pregnancy influences the association between pre-pregnancy body mass index and types of delivery and birth: a comparison of urban and rural areas.

BACKGROUND: Women in study areas suffered from the problems of caesarean delivery (CD), low birth weight (LBW), and macrosomia. OBJECTIVE: To investigate how gestational weight gain (GWG) influences the effect of the pre-pregnancy body mass index (BMI) on the risks of CD, LBW, and macrosomia in urban and rural areas in a city of Iran. METHODS: We used 767 and 612 eligible subjects from the public health care centers in urban and rural areas respectively. RESULTS: The risk of CD increased from 74% to 2.62-fold in urban and from 62% to 2.15-fold in rural areas, and the risk of macrosomia increased from 58% to 2.35-fold in urban and from 47% to 96% in rural areas, among obese women compared to normal weight women who gained above median GWG. The risk of LBW increased from 38% to 92% in urban and from 49% to 97% in rural areas among lean women compared to normal weight women who gained below median GWG. CONCLUSION: These findings strongly support the need to reform adequate pre-pregnancy weight and GWG against the risks of CD and macrosomia among overweight and obese women, and against the risk of LBW among lean women in both areas.

Evaluation of viability and growth of Acetobacter senegalensis under different stress conditions.

Acetic acid bacteria (AAB) are used in production of vinegars. During acetic acid fermentation, AAB encounter various aggressive conditions which may lead to a variety of cellular disorders. Previous researches mainly studied the influences of different carbon sources on tolerance of AAB to ethanol and acetic acid. In this study, different techniques were used comparatively to investigate the effects of preadaptation on the ability of A. senegalensis to tolerate ethanol and acetic acid. In general, the carbon sources used for preadaptation of A. senegalensis exhibited significant effects on the tolerance of cells to stressors. Flow-cytometric assessments of preadapted cells in ethanol showed that 87.3% of the cells perform respiration after exposure to a stress medium containing 5% (v/v) ethanol and 3% (w/v) acetic acid. However, 58.4% of these preadapted cells could keep their envelope integrity under the stress condition. They could also grow rapidly (µmax=0.39/h) in the stress medium (E5A3) with a high yield (>80%). A. senegalensis grown in glucose exhibited a low tolerance to acetic acid. Analysis of their respiration capacity, membrane integrity and culturability revealed that almost all the population were dead after exposure to 5% (v/v) ethanol and 3% (w/v) acetic acid. In contrast, exposure of A. senegalensis preadapted in a mixture of glucose and acetic acid to a stress medium containing 5% (v/v) ethanol and 3% (w/v) acetic acid, exhibited an intact respiration system and cellular membrane integrity in 80.3% and 50.01% of cells, respectively. Moreover, just 24% of these cells could keep their culturability under that stress condition. In summary, cell envelope integrity, growth and culturability are more susceptible to pH and acetic acid stresses whereas respiration system is less subjected to damages under stress condition. In addition, preadaptation of A. senegalensis in a mixture of glucose and acetic acid enables it to tolerate and grow in ethanol and acetic acid.

Comparison of leaf saturation isothermal remanent magnetisation (SIRM) with anatomical, morphological and physiological tree leaf characteristics for assessing urban habitat quality.

Leaf saturation isothermal remanent magnetisation (SIRM) is known as a good proxy of atmospheric, traffic related particulate matter (PM) concentration. In this study, we compared leaf SIRM with Leaf area (LA), leaf dry weight (LDW), specific leaf area (SLA), stomatal density (SD), relative chlorophyll content (RCC), chlorophyll fluorescence parameters (Fv/Fm and PI) for three urban tree types in the city of Ghent, Belgium. A negative significant relationship of LA, LDW and Fv/Fm, and a positive significant relationship of SLA with leaf SIRM was observed. Among all considered parameters, leaf SIRM had the highest potential for discrimination between contrasting land use classes. It was concluded that urban habitat quality can be monitored with leaf SIRM, independent of the other above mentioned plant parameters. The anatomical, morphological and physiological tree leaf characteristics considered are not good indicators for atmospheric PM, but might be interesting bio-indicators of other air pollutants than PM.