Extracellular Polymeric Substances (EPS) influenced Poly Cyclic Aromatic Hydrocarbons (PAHs) degrading Klebsiella pneumoniae was isolated from the marine environment. To increase the EPS production by Klebsiella pneumoniae, several physicochemical parameters were tweaked such as different carbon sources (arabinose, glucose, glycerol, lactose, lactic acid, mannitol, sodium acetate, starch, and sucrose at 20 g/L), nitrogen sources (ammonium chloride, ammonium sulphate, glycine, potassium nitrate, protease peptone and urea at 2 g/L), different pH, carbon/nitrogen ratio, temperature, and salt concentration were examined. Maximum EPS growth and biodegradation of Anthracene (74.31%), Acenaphthene (67.28%), Fluorene (62.48%), Naphthalene (57.84%), and mixed PAHs (55.85%) were obtained using optimized conditions such as glucose (10 g/L) as carbon source, potassium nitrate (2 g/L) as the nitrogen source at pH 8, growth temperature of 37 °C, 3% NaCl concentration and 72 h incubation period. The Klebsiella pneumoniae biofilm architecture was studied by confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The present study demonstrates the EPS influenced PAHs degradation of Klebsiella pneumoniae.

Low pH and aluminum (Al)-toxicity often coexist in acidic soils. Citrus sinensis seedlings were treated with nutrient solution at a pH of 2.5, 3.0, 3.5 or 4.0 and an Al concentration of 0 or 1 mM for 18 weeks. Thereafter, malate, citrate, isocitrate, acid-metabolizing enzymes, and nonstructural carbohydrates in roots and leaves, and release of malate and citrate from roots were measured. Al concentration in roots and leaves increased under Al-toxicity, but it declined with elevating nutrient solution pH. Al-toxicity increased the levels of glucose, fructose, sucrose and total soluble sugars in leaves and roots at each given pH except for a similar sucrose level at pH 2.5–3.0, but it reduced or did not alter the levels of starch and total nonstructural carbohydrates (TNC) in leaves and roots with the exception that Al improved TNC level in roots at pH 4.0. Levels of nonstructural carbohydrates in roots and leaves rose with reducing pH with a few exceptions with or without Al-toxicity. A potential model for the possible role of root organic acid (OA) metabolism (anions) in C. sinensis Al-tolerance was proposed. With Al-toxicity, the elevated pH upregulated the OA metabolism, and increased the flow of carbon to OA metabolism, and the accumulation of malate and citrate in roots and subsequent release of them, thus reducing root and leaf Al and hence eliminating Al-toxicity. Without Al-toxicity, low pH stimulated the exudation of malate and citrate, an adaptive response of Citrus to low pH. The interactive effects of pH and pH on OA metabolism were different between roots and leaves.

A field study was conducted to understand the physiological responses, yield and grain quality of an old (HUW234) and a modern (HD3118) wheat cultivar exposed to elevated ozone (O₃). The cultivars were grown under ambient O₃ (NF) and ambient +20 ppb O₃ (NF+) conditions using open-top chambers (OTCs). The comparative study of an old and a modern cultivar showed variable physiological responses under elevated O₃ exposure. Elevated O₃ in old cultivar caused high reductions in Rubisco activity (Vcₘₐₓ) and electron transport rate (J) compared to modern cultivar with simultaneous reductions in the rate of photosynthesis and chlorophyll fluorescence. In modern cultivar, high stomatal density and conductance caused higher O₃ uptake thereby triggering more damage to the adjacent stomatal cells and photosynthetic pigments coupled with reductions in photosynthetic rate and photosynthetic nitrogen use efficiency (PNUE). Modern cultivar also showed relatively high reduction in grain yield compared to old one under NF + treatment. Furthermore, grain quality traits (such as starch, protein and amino acids) of modern cultivar were better than old cultivar under ambient O₃, but showed more deterioration under NF + treatment. Results thus indicated that modern cultivar is relatively more susceptible to O₃ and showed more negative impacts on plant performance, yield and quality of grains compared to old cultivar.

Rising tropospheric ozone concentrations in Asia affect the yield and quality of rice. This study investigated ozone-induced changes in rice grain quality in contrasting rice genotypes, and explored the associated physiological processes during the reproductive growth phase. The ozone sensitive variety Nipponbare and a breeding line (L81) containing two tolerance QTLs in Nipponbare background were exposed to 100 ppb ozone (8 h per day) or control conditions throughout their growth. Ozone affected grain chalkiness and protein concentration and composition. The percentage of chalky grains was significantly increased in Nipponbare but not in L81. Physiological measurements suggested that grain chalkiness was associated with a drop in foliar carbohydrate and nitrogen levels during grain filling, which was less pronounced in the tolerant L81. Grain total protein concentration was significantly increased in the ozone treatment, although the albumin fraction (water soluble protein) decreased. The increase in protein was more pronounced in L81, due to increases in the glutelin fraction in this genotype. Amino acids responded differently to the ozone treatment. Three essential amino acids (leucine, methionine and threonine) showed significant increases, while seven showed significant treatment by genotype interactions, mostly due to more positive responses in L81. The trend of increased grain protein was in contrast to foliar nitrogen levels, which were negatively affected by ozone. A negative correlation between grain protein and foliar nitrogen in ozone stress indicated that higher grain protein cannot be explained by a concentration effect in all tissues due to lower biomass production. Rather, ozone exposure affected the nitrogen distribution, as indicated by altered foliar activity of the enzymes involved in nitrogen metabolism, such as glutamine synthetase and glutamine-2-oxoglutarate aminotransferase. Our results demonstrate differential responses of grain quality to ozone due to the presence of tolerance QTL, and partly explain the underlying physiological processes.

A combination of in vitro and in vivo studies on tomato (Lycopersicon esculentum Mill. cv. Triton) revealed that environmentally-relevant levels of ozone (O3) pollution adversely affected pollen germination, germ tube growth and pollen-stigma interactions – pollen originating from plants raised in charcoal-Purafil® filtered air (CFA) exhibited reduced germ tube development on the stigma of plants exposed to environmentally-relevant levels of O3. The O3-induced decline in in vivo pollen viability was reflected in increased numbers of non-fertilized and fertilized non-viable ovules in immature fruit. Negative effects of O3 on fertilization occurred regardless of the timing of exposure, with reductions in ovule viability evident in O3 × CFA and CFA × O3 crossed plants. This suggests O3-induced reductions in fertilization were associated with reduced pollen viability and/or ovule development. Fruit born on trusses independently exposed to 100 nmol mol−1 O3 (10 h d−1) from flowering exhibited a decline in seed number and this was reflected in a marked decline in the weight and size of individual fruit – a clear demonstration of the direct consequence of the effects of the pollutant on reproductive processes. Ozone exposure also resulted in shifts in the starch and ascorbic acid (Vitamin C) content of fruit that were consistent with accelerated ripening. The findings of this study draw attention to the need for greater consideration of, and possibly the adoption of weightings for the direct impacts of O3, and potentially other gaseous pollutants, on reproductive biology during ‘risk assessment’ exercises.

Seedlings of Psidium guajava cv. Pedro Sato were distributed into four open-top chambers: two with ambient CO2 (∼390 ppm) and two with elevated CO2 (∼780 ppm). Monthly, five individuals of each chamber were collected, separated into root, stem and leaves and immediately frozen in liquid nitrogen. Chemical parameters were analyzed to investigate how guava invests the surplus carbon. For all classes of phenolic compounds analyzed only tannins showed significant increase in plants at elevated CO2 after 90 days. There was no significant difference in dry biomass, but the leaves showed high accumulation of starch under elevated CO2. Results suggest that elevated CO2 seems to be favorable to seedlings of P. guajava, due to accumulation of starch and tannins, the latter being an important anti-herbivore substance.

We synthesized the effects of ozone on wheat quality based on 42 experiments performed in Asia, Europe and North America. Data were analysed using meta-analysis and by deriving response functions between observed effects and daytime ozone concentration. There was a strong negative effect on 1000-grain weight and weaker but significant negative effects on starch concentration and volume weight. For protein and several nutritionally important minerals (K, Mg, Ca, P, Zn, Mn, Cu) concentration was significantly increased, but yields were significantly decreased by ozone. For other minerals (Fe, S, Na) effects were not significant or results inconclusive. The concentration and yield of potentially toxic Cd were negatively affected by ozone. Some baking properties (Zeleny value, Hagberg falling number) were positively influenced by ozone. Effects were similar in different exposure systems and for spring and winter wheat. Ozone effects on quality should be considered in future assessments of food security/safety.

It has been shown that starch can effectively stabilize nanoscale magnetite particles, and starch-stabilized magnetite nanoparticles (SMNP) are promising for in situ remediation of arsenic-contaminated soils. However, a molecular level understanding has been lacking. Here, we carried out XAFS studies to bridge this knowledge gap. Fe K-edge XAFS spectra indicated that the Fe–O and Fe–Fe coordination numbers of SMNP were lower than those for bare magnetite particles, and these coordination numbers decreased with increasing starch concentration. The decrease in the average coordination number at elevated stabilizer concentration was attributed to the increase in the surface-to-volume ratio. Arsenic K-edge XAFS spectra indicated that adsorbed arsenate on SMNP consisted primarily of binuclear bidentate (BB) complexes and monodentate mononuclear (MM) complexes. More BB complexes (energetically more favorable) were observed at higher starch concentrations, indicating that SMNP not only offered greater adsorption surface area, but also stronger adsorption affinity toward arsenate.

Constructed wetlands integrated with microbial fuel cells (MFC-CWs) have been recently developed and tested for removing antibiotics. However, the effects of carbon source availability, electron transfer flux and cathode conditions on antibiotics removal in MFC-CWs through co-metabolism remained unclear. In this study, four experiments were conducted in MFC-CW microcosms to investigate the influence of carbon source species and concentrations, external resistance and aeration duration on sulfamethoxazole (SMX) and tetracycline (TC) removal and bioelectricity generation performance. MFC-CWs supplied with glucose as carbon source outperformed other carbon sources, and moderate influent glucose concentration (200 mg L⁻¹) resulted in the best removal of both SMX and TC. Highest removal percentages of SMX (99.4%) and TC (97.8%) were obtained in MFC-CWs with the external resistance of 700 Ω compared to other external resistance treatments. SMX and TC removal percentages in MFC-CWs were improved by 4.98% and 4.34%, respectively, by increasing the aeration duration to 12 h compared to no aeration. For bioelectricity generation performance, glucose outperformed sodium acetate, sucrose and starch, with the highest voltages of 386 ± 20 mV, maximum power density (MPD) of 123.43 mW m⁻³, and coulombic efficiency (CE) of 0.273%. Increasing carbon source concentrations from 100 to 400 mg L⁻¹, significantly (p < 0.05) increased the voltage and MPD, but decreased the internal resistance and CE. The highest MPD was obtained when the external resistance (700 Ω) was close to the internal resistance (600.11 Ω). Aeration not only improved the voltage and MPD, but also reduced the internal resistance. This study demonstrates that carbon source species and concentrations, external resistances and aeration duration, all play vital roles in regulating SMX and TC removal in MFC-CWs.

Nitric oxide (NO) and hydrogen sulfide (H₂S) since their discovery have proven to be game changing molecules in alleviating abiotic stress. They individually play role in plant stress management while the pathways of stress regulation through their crosstalk remain elusive. The current study focuses on investigating the interplay of NO and H₂S signalling in the amelioration of arsenate As(V) toxicity in rice seedlings and managing its growth, photosynthesis, sucrose and proline metabolism. Results show that As(V) exposure declined fresh weight (biomass) due to induced cell death in root tips. Moreover, a diminished RuBisCO activity, decline in starch content with high proline dehydrogenase activity and increased total soluble sugars content was observed which further intensified in the presence of Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME, an inhibitor of nitric oxide synthase-like activity), and DL-propargylglycine (PAG, an inhibitor of cysteine desulfhydrase activity). These results correlate with lower endogenous level of NO and H₂S. Addition of L-NAME increased As(V) toxicity. Interestingly, addition of SNP reverses effect of L-NAME suggesting that endogenous NO has a role in mitigating As(V) toxicity. Similarly, exogenous H₂S also significantly alleviated As(V) stress, while PAG further stimulated As(V) toxicity. Furthermore, application of H₂S in the presence of L – NAME and NO in the presence of PAG could still mitigate As(V) toxicity, suggesting that endogenous NO and H₂S could independently mitigate As(V) stress.