Modeling rhamnolipids production by Pseudomonas aeruginosa from immiscible carbon source in a batch system

A mathematical model to predict the rhamnolipids production by Pseudomonas aeruginosa from oleic acid in a two phase liquid-liquid batch reaction system, was developed in this study. The model was based on two theoretical assumptions: 1) the convective oleic acid mass transfer is coupled to a bioreaction in the aqueous liquid bulk, and 2) the volume of the immiscible oleic acid drops and the saturation concentration at the interface are a function of rhamnolipids production. The model was able to accurately predict the experimental growth of the Pseudomonas aeruginosa strain, and the rhamnolipids production data with oleic acid as carbon source. This mathematical approach indicated a high correspondence between the saturation dimensionless profiles of oleic acid at the interface and the experimental profiles of surface tension difference. This modeling approach may constitute a useful tool in the design and scaling-up of bioreactors applied to the production of biosurfactants with immiscible carbon sources.     

Effect of tween 80 added to the soil on the degradation of endosulfan by Pseudomonas aeruginosa

Endosulfan, a chlorinated cyclodiene insecticide is of environmental concern because of its apparent persistence and toxicity to many non target organisms. Endosulfan is hydrophobic and persists in soil for more than a year. To overcome the problem of hydrophobic and limited availability, surfactants play a major role in soil remediation. In the present study, the effect of Tween 80 added to the soil on the degradation of endosulfan by Pseudomonas aeruginosa at different pH (7.0 and 8.5) was studied. The addition of synthetic surfactant Tween 80 enhanced the solubility and degradation of endosulfan. A significant degradation (94%) was observed in pH 8.5 and Tween 80 added soil; the bacterial population in the treatment unit T8 was 75 × 10⁹ CFU/g of soil. The unit T4 inoculated at pH 8.5 showed 86 % alpha and 60 % beta endosulfan degradation, the bacterial population was 73 × 10⁸ CFU / g of soil. The degradation of both the isomers were observed and accompanied with formation of endodiol and endosulfan sulfate.     

Plasmid profile and curing analysis of Pseudomonas aeruginosa as metal resistant

The isolate Pseudomonas aeruginosa exhibited resistance to heavy metals such as cadmium, chromium, nickel and lead. Plasmid DNA was isolated from P. aeruginosa and designated as pBC15. The size of the plasmid DNA was approximately 23 kb. Escherichia coli DH5α was transformed with plasmid pBC15 subsequired resistance to nickel and ampicillin. The same size of the plasmid was isolated from E. coli transformant and separated on 0.7 % agarose gel electrophoresis. The restriction analysis of pBC15 showed that the plasmid DNA has single site for Bam HI and Eco RI and three sites for Xho I which were compared with 1 Kb DNA and λ Hind III digest molecular markers. Therefore, the size of the plasmid DNA of pBC15 was confirmed to be 23 kb. Curing was carried out by ethidium bromide, acridine orange, novobiocin, sodium dodechyl sulphate and elevated temperature (40 °C). Transformation and curing results suggest that nickel and ampicillin resistance gene was conferred by plasmid DNA. Cadmium resistant gene was present on chromosomal DNA along with the gene for chromium resistance. Lead resistance gene was shown to be present on the chromosomal DNA rather than the plasmid DNA as the cured and uncured cultures remained similar in lead resistance. Therefore, the ability of P. aeruginosa resistant to nickel and ampicillin is plasmid mediated and transferable to other strains whereas cadmium, chromium and lead could be chromosomal encoded. The heavy metal and antibiotic resistances of P. aeruginosa can be used to exploit for clean up industrial wastewater and bioremediation of heavy metal contaminated soil.     

Response surface methodology mediated optimization of Remazol Orange decolorization in plain distilled water by Pseudomonas aeruginosa BCH

The bacterium Pseudomonas aeruginosa BCH decolorized and degraded the sulphonated azo dye Remazol Orange in plain distilled water. The effects of different parameters, i.e. pH, temperature and cell mass concentration on the biodegradation of dye in aqueous phase was evaluated using response surface methodology. Optimization was carried out using three-level Box–Behnken design. Predicted values were found to be in good agreement with experimental values (R ² 0.9997 and pred R ² 0.9984), which indicated suitability of the employed model and the success of response surface methodology. Optimum dye decolorization was maximized and the favourable conditions were pH 7.43, temperature 29.39 °C and cell mass concentration 2.88 g l^?1, which resulted in 96.01 % decolorization within 5 h. It was validated from the predicted response (97.37 %). According to the analysis of variance results, the proposed model can be used to navigate the design space. 3D plot analysis disclosed the significant interaction between all three tested factors on decolorization process. The combinations of the three variables predicted during response surface methodology were confirmed through confirmatory experiments. Observations indicated that higher cell mass accelerated the decolorization process. Degradation of the dye was verified through high performance liquid chromatography analysis. Phytotoxicity studies carried out with dye and dye metabolites using Phaseolus mungo, Triticum aestivum and Sorghum vulgare indicated the detoxification of dye.     

Sulfur isotope fractionation during growth of sulfate-reducing bacteria on various carbon sources

Stable sulfur isotope fractionation during microbial sulfate reduction is a potential tool to estimate sulfate reduction rates at field sites. However, little is known about the influence of the utilized carbon source on the magnitude of sulfur isotope fractionation. To investigate this effect, both a pure culture (strain PRTOL1) and enrichment cultures from a petroleum hydrocarbon (PHC)-contaminated aquifer were used and grown in batch cultures on various carbon sources with an initial sulfate concentration of 1 mmol/L. As sole carbon sources the PHC components naphthalene, 1,3,5-trimethylbenzene, and heating oil (enrichment culture) and the organic acids acetate, pyruvate, benzoate, and 3-phenylpropionate (enrichment culture and PRTOL1) were used. Sulfate reduction rates of all cultures ranged from 6 ± 1 nmol cm⁻³ d⁻¹ (enrichment culture grown on 1,3,5-trimethylbenzene) to 280 ± 6 nmol cm⁻³ d⁻¹ (enrichment culture grown on pyruvate). Cell-specific sulfate reduction rates ranged from 1.1 × 10⁻¹⁴ mol cell⁻¹ d⁻¹ (PRTOL1 grown on pyruvate) to 1.5 × 10⁻¹³ mol cell⁻¹ d⁻¹ (PRTOL1 grown on acetate). Sulfur isotope enrichment factors (ε) for the enrichment culture ranged from 16.1‰ (3-phenylpropionate) to 34.5‰ (1,3,5-trimethylbenzene) and for PRTOL1 from 30.0‰ (benzoate) to 36.0‰ (pyruvate). Cultures of PRTOL1 always showed higher ε values than the enrichment culture when grown on the same carbon source due to culture-specific properties. Higher ε values were obtained when the enrichment culture was grown on PHC components than on organic acids. No relationship between ε values and cell-specific sulfate reduction rate existed when all data were combined. When comparing the magnitude of ε values determined in this laboratory study with ε values measured at contaminated and uncontaminated field sites, it becomes evident that a multitude of factors influences ε values at field sites and complicates their interpretation. The results of this study help us assess some of the general parameters that govern the magnitude of ε in sulfate-reducing environments.     

Stable carbon isotopic evidence for sources of particulate organic carbon found in sea foam

Particulate organic carbon found in sea foam and water samples from North Inlet, South Carolina, were examined for their δ¹³C isotopic composition. Sea foam particulate organic carbon (POC) δ¹³C values ranged from ?20.4 to ?24.6‰ (mean=?22.3‰) and water POC δ¹³C values ranged from ?21.0 to ?28.5‰ (mean= ?24.4‰). Temporal trends in sea foam and water POC indicate that δ¹³C values for both POC components are depleted in the colder months and enriched in the warmer months. Measurement of δ¹³C from potential sources for organic matter found in sea foam, combined with data on macroalgae productivity and phytoplankton biomass, indicates that macroalgae are the principal source of POC for sea foam in the colder months. In the warmer months, phytoplankton appear to be more important contributors. The observed water POC δ¹³C values were always depleted relative to foam POC δ¹³C values. This isotopic difference may result from chemical segregation during sea foam formation or may reflect DOC δ¹³C values from terrestrial origins.     

Biosynthesis and genetics of polyhydroxyalkanoates by newly isolated <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> IFS and 30N using inexpensive carbon sources

Poly(3-hydroxyalkanoates) (PHAs) are the bioplastics that are stored in many genera of bacteria as carbon and energy storage polyester granules. PHAs have established themselves as strong competitors to conventional plastics. This study reports the isolation of PHA-accumulating bacteria from local environment and their PHA characterization. Two potential strains identified as Pseudomonas aeruginosa strain IFS (Accession no. JQ041638) and P. aeruginosa strain 30N (Accession no. JQ041639) based on 16S rRNA gene sequence identity were cultivated under nitrogen limited conditions to study their PHA biosynthesis capabilities. The strain IFS and strain 30N produced 1.36 and 1.40 gl^?1 dry biomass with percentage PHA contents of 44.85 and 45.74%, respectively, when grown on glucose as carbon source. The PHA was identified as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by fourier transform infrared spectroscopy (FTIR) and gas chromatography coupled with mass spectrometry (GC–MS). The PHA synthase genes of these strains were isolated, sequenced and analyzed using bioinformatic tools that showed they belonging to type 2 PHA synthases and presented their evolutionary relationships with PHA synthases of other Pseudomonas species. The experimental results of this study highlight the importance of these strains for future use of bacterial biopolymer production growing on simple and inexpensive carbon sugars.     

不同碳源对砷污染沉积物中砷的微生物降解的影响

在试验室通过使用多种碳源（包括醋酸盐、乳酸盐和葡萄糖），对采于朝鲜废弃金银矿地区的受砷污染的沉积物样品（339毫克／千克）中固有细菌生物激化后，就沉积物样品中固有细菌对砷物种形成和活动性的影响，进行了研究。通过连续提取分析来确定砷的形式，结果表明，沉积物中40％和47％的砷分别以铁伴生物和残留组分的形式存在。通过使用醋酸盐和乳酸盐对沉积物样品进行培育22天后，固有细菌增加了沉积物样品中铁伴生物和残留组分中溶解砷的总量。当与消过毒的沉积物样品（总溶解砷浓度低于50％）对比时发现，生物悬浮液中超过99％的溶解砷以砷（V）的形式存在，这表明，固有细菌将部分溶解的砷（III）转换成了砷（V）。在实际环境中，依据pH值的不同，微生物引起的水成砷（V）既可以通过吸附而固定不动，也可以在向地下缺氧区迁移后被还原成（III）。     

西南背景区冬、夏季黑碳稳定碳同位素组成及来源

为确定中国西南背景区不同季节细颗粒物中黑碳的浓度水平和来源特征,分别于2018年冬季(1月)和夏季(7月)在贵州普定喀斯特生态系统观测研究站采集细颗粒物样品,测定其水溶性离子成分、黑碳浓度及稳定碳同位素组成(δ¹³C_BC),结合贝叶斯模型探讨黑碳来源贡献。结果表明,采样期间黑碳冬季平均浓度为(1.2±0.6)μg/m³,夏季为(1.9±0.6)μg/m³,接近于其他区域背景点浓度水平。δ¹³C_BC平均值冬季为(-23.4±0.9)‰,夏季为(-24.3±0.8)‰,处于煤燃烧及机动车排放来源的δ¹³C值范围。贝叶斯模型结果表明,机动车尾气在冬、夏季节对黑碳贡献较高,分别为(45.1±14.2)%和(69.5±8.6)%,煤燃烧贡献分别为(41.7±9.8)%和(24.1±7.2)%。结合后向轨迹分析结果可知,西南背景区冬季黑碳来源受燃煤、机动车尾气排放及生物质燃烧共同影响;夏季黑碳污染源主要为机动车尾气和煤燃烧,生物质燃烧较少。     

Temporal variability in sources of dissolved organic carbon in the lower Mississippi river

Here we report on the temporal changes in the composition of dissolved organic carbon (DOC) collected in the tidal freshwater region of the lower Mississippi River. Lignin-phenols, bulk stable carbon isotopes, compound-specific isotope analyses (CSIA) and ¹³C nuclear magnetic resonance (NMR) spectrometry were used to examine the composition of high molecular weight dissolved organic matter (HMW DOM) at one station in the lower river over 6 different flow regimes in 1998 and 1999. It was estimated that the annual input of DOC delivered to the Gulf of Mexico from the Mississippi River was of 3.1 × 10⁻³ Pg, which represents 1.2% of the total global input of DOC from rivers to the ocean. Average DOC and HMW DOC were 489 ±163 and 115 ± 47 μM, respectively. ¹³C-NMR spectra revealed considerably more aliphatic structures than aromatic carbons in HMW DOC. Lignin phenols were significantly ¹³C-depleted with respect to bulk HMW DOM indicating that C₄ grass inputs to the HMW DOM were not significant. It is speculated that C₄ organic matter in the river is not being converted (via microbial decay) to HMW DOM as readily as C₃ organic matter is, because of the association of C₄ organic matter with finer sediments. The predominantly aliphatic ¹³C NMR signature of HMW DOM suggests that autochthonous production in the river may be more important as a source of DOC than previously thought. Increases in nutrient loading and decreases in the suspended load (because of dams) in the Mississippi River, as well as other large rivers around the world, has resulted in significant changes in the sources and overall cycling of riverine DOC.     

Induction of Calcium Carbonate by Pseudomonas Putida

The purpose of this research is to study how the bacteria Pseudomonas putida (DCB13) utilises calcium ions in a culture medium with carbon dioxide (CO2) to yield calcium carbonate (CaCO3). The bacteria strain P. putida is a dominant strain isolated from the dolomitic surfaces in areas of Karst topographies, Guizhou Province. The experimental method was as follows: a modified beef extract-peptone medium (beef extract 3.0 g, peptone 10 g, NaCl 5.0 g, CaCl2 2.0 g, glass powder 2.0 g, distilled water 1 L and a pH between 6.5 and 7.5) was inoculated with P. putida in order to attempt to induce the synthesis of CaCO3. The sample was then processed by centrifugation every 24 hours during the 7-day cultivation period. The pH, carbonic anhydrase (CA) activity, and the concentrations of both HCO3- and Ca2+ of the supernatant fluid were measured. Subsequently, precipitation in the culture medium was analyzed to confirm, or otherwise, the presence and if present, the formation of CaCO3. Methods used included X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), and Energy Dispersive Spectroscopy (EDS). Results showed that P. putida can improve its pH value in this culture medium; concentrations of HCO3- and Ca2+ showed a significant decline over the duration of the cultivation period. CA activity reached its maximum during the second day; XRD, SEM and TEM all revealed the presence of CaCO3 as a precipitate. Additionally, these results did not occur in an aseptic control group: no detectable level of CaCO3 was yielded therein. In conclusion: P. putida can metabolise active materials such as secretase by its own growth and metabolism, and can either utilise atmospheric CO2, or respire, to induce CaCO3 production.     

PseudomonasputidaMnB1氧化分解菱锰矿的实验研究

自然界中,菱锰矿氧化形成锰的氧化物矿物是非常普遍的现象,在菱锰矿被氧化分解发生物相转变的过程中,碳酸 盐溶解和锰的氧化往往同时发生,微生物可能起着催化作用。选取锰氧化模式菌株PseudomonasputidaMnB1和广西梧州菱 锰矿,通过菱锰矿在该细菌作用下发生转变的实验,利用场发射扫描电镜、扫描透射X射线显微成像等分析方法,研究了 矿石表面形貌变化以及锰元素在细胞上的分布特征。结果表明细菌显著促进的菱锰矿的溶解,在此基础上,进一步探讨了 细菌在菱锰矿氧化过程中的贡献,本实验结果丰富了次生锰矿床的微生物成因研究。     

Practical evaluation of carbon sources of forest soils in Slovenia from stable and radio-carbon isotope measurements

Carbon sources were estimated by measuring carbon isotope ratios (??¹³C and ??¹⁴C) with accelerator mass spectrometry (AMS) in forest soils of different lithology. Six locations were selected in temperate deciduous and coniferous stands in Slovenia (?irovski vrh, Idrija, Ko?evski Rog, Pohorje, Gori?nica, and Rakitna), where carbonate rocks consisting of limestone and dolomite are abundant as underlying bedrock. Carbon isotope fractionation would not have occurred in two carbonaceous soils, since the values of both ??¹³C and ??¹⁴C changed consistently in these soils after thermal (550°C, 2?h) or chemical (1?M HCl, 24?h) treatments. Organic components were found to be predominant carbon sources (70?C100%) in the uppermost portions (0?C2?cm in depth). In deeper portions at a depth of about 30?C35?cm, soil carbon may be derived completely from underlying carbonate minerals in Idria, western part of Slovenia. The Combination of heat and chemical treatments with AMS provides practical information on soil carbon sources in carbonaceous soils.     

Bacterial hopanoids as tracers of organic carbon sources and processing across the western Arctic continental shelf

Tracing the inputs of bacterial organic carbon to marine systems has been constrained by the lack of distinguishing geochemical tracers and limited contribution in sediments compared to other sources of organic matter. Bacteriohopanepolyols (BHPs) provide a direct means to identify bacterial inputs which also reflect potential bacterial groups and their activities in aquatic systems. We applied recent analytical approaches to identify and quantify bacterial derived carbon contributions to surface sediments from the western Arctic Ocean using BHPs. The abundance and distribution of BHPs resemble trends of water column primary production and suggest active heterotrophic recycling of in situ production with some component of long term preservation. BHPs proposed as terrestrial derived signatures (i.e. adenosylhopanes) were also abundant in western Arctic sediments and reflect offshore trends of other terrigenous lipid signatures with a fraction representing their degradative products. Analysis of BHPs in organic rich peat and surface sediments from two Arctic rivers showed the highest inputs of adenosylhopanes, implying active bacterial recycling of recalcitrant terrigenous material. BHPs observed in western Arctic surface sediments reveal significant contributions of bacteria associated with organic carbon from multiple sources.     

桂林潮田河溶解无机碳来源与昼夜动态变化

生物地球化学过程是地球关键带的三大过程之一。在全球变化与岩溶碳循环研究领域,了解生物地球化学过程、影响因素与机制,对解决岩溶作用时间尺度与碳汇稳定性问题具有至关重要的作用。以广西桂林漓江支流潮田河为例,通过高分辨率在线监测与高频率自动化取样分析,研究了溶解无机碳（DIC）及其同位素、电导率与其他离子含量的昼夜变化规律,并分析了其影响因素。pH、溶解氧、电导率、Ca²⁺和HCO₃^-离子含量均呈现显著的昼夜动态变化,反映水生植物和藻类光合作用及钙沉积的影响。鸟岭桥与两河沟两个监测点的电导率、Ca²⁺和HCO₃^-离子含量具有白天下降、夜间上升的变化规律,鸟岭桥白天下降幅度分别为10%、11.5%~12.5%和10%~12%。48小时监测期间鸟岭桥光合作用DIC平均转化速率为0.64×10^-5mmol/L ·s,日转化HCO₃^-的量约为1484kg/d（相当于292kg C/d）,占总DIC输入量的4%;平均钙沉积速率为0.38×10^-5mmol/L ·s,较小的速率可能与水体中较高的溶解有机碳含量产生的抑制作用有关。Ca²⁺与HCO₃^-离子含量夜间的快速上升主要是上游来自岩溶含水层的地下水直接补给造成的。在年际尺度上潮田河DIC中75%~80%来自于岩溶地下水。

     

Metal accumulation by plant species growing on a mine contaminated site in Mexico

The present work aims to assess the efficiency of heavy metal accumulation of native species growing in contaminated soils in the mining district of Taxco, Mexico. Soil and tailing sampling was conducted in three study sites: La Concha, El Fraile, and a control site. The study localities present diverse metal concentrations with significant differences in their proportion in the geochemical fractions. Results show that species Cupressus lindleyi and Juniperus deppeana accumulate Zn and Mn in anomalous concentrations at La Concha, where Zn is present in soluble fractions. Manganese, despite not being present mostly in the soluble fraction in soils and tailings, seems to have been increased in the soluble fraction after the plant growth. In contrast, samples of the same species taken at El Fraile and in the control site, where Zn and Mn are mainly contained in the residual fraction, do not show an anomalous enrichment. Other analyzed species growing under the same contamination conditions in La Concha (Jacaranda mimosifolia and Psidium guajava) do not show anomalous concentrations. These facts confirm the Zn and Mn accumulation capacity of C. lindleyi and Ju. deppeana, which depends on their accumulation ability and on the concentration of these elements in the soluble fraction.