The secondary outbreak risk and mechanisms of Microcystis aeruginosa after H2O2 treatment

The secondary outbreak of cyanobacteria after algicide treatment has been a serious problem to water ecosystems. Hydrogen peroxide (H2O2) is an algaecide widely used in practice, but similar re-bloom problems are inevitably encountered. Our work found that Microcystis aeruginosa (M. aeruginosa) temporarily hibernates after H2O2 treatment, but there is still a risk of secondary outbreaks. Interestingly, the dormant period was as long as 20 and 28 days in 5 mg L-1 and 20 mg L-1 H2O2 treatment groups, respectively, but the photosynthetic activity was both restored much earlier (within 14 days). Subsequently, a quantitative imaging flow cytometry-based method was constructed and confirmed that the re-bloom had undergone two stages including first recovery and then re-division. The expression of ftsZ and fabZ genes showed that M. aeruginosa had active transcription processes related to cell division protein and fatty acid synthesis during the dormancy stat. Furthermore, metabolomics suggested that the recovery of M. aeruginosa was mainly by activating folate and salicylic acid synthesis pathways, which promoted environmental stress resistance, DNA synthesis, and cell membrane repair. This study reported the comprehensive mechanisms of secondary outbreak of M. aeruginosa after H2O2 treatment. The findings suggest that optimizing the dosage and frequency of H2O2, as well as exploring the potential use of salicylic acid and folic acid inhibitors, could be promising directions for future algal control strategies.

Dynamic characteristics of total and microcystin-producing Microcystis in a large deep reservoir

Microcystis, one of the common cyanobacteria, often causes blooms in reservoirs, which has seriously threatened the safety of drinking water worldwide. To identify the growth characteristic of total and microcystin-producing Microcystis in large deep reservoirs, we used Quantitative PCR (qPCR) to measure the cell density of total and microcystin-producing Microcystis and monitored water quality in the water samples collected in Dongzhang Reservoir once a month. Microcystis blooms occurred in Dongzhang Reservoir in April 2017, which was composed of microcystin-producing and non-microcystin-producing Microcystis. Water temperature, dissolved oxygen, pH, and chlorophyll-a showed significant vertical stratification during Microcystis blooms. Total and microcystin-producing Microcystis grew rapidly under the high concentration of total phosphorus and rising water temperatures. Nitrate-nitrogen had a significant linear correlation with the abundance of microcystin-producing Microcystis. Our results indicated that nutrients and water temperature could be key triggers of Microcystis blooms and nitrate-nitrogen potentially regulates the competition between microcystin-producing and non-microcystin-producing Microcystis. This study improves our understanding of the characteristics of Microcystis blooms and the competition between microcystin-producing and non-microcystin-producing Microcystis in large deep reservoirs.

Microbiological risks increased by ammonia-oxidizing bacteria under global warming: The neglected issue in chloraminated drinking water distribution system

A rising outbreak of waterborne diseases caused by global warming requires higher microbial stability in the drinking water distribution system (DWDS). Chloramine disinfection is gaining popularity in this context due to its good persistent stability and fewer disinfection byproducts. However, the microbiological risks may be significantly magnified by ammonia-oxidizing bacteria (AOB) in distribution systems during global warming, which is rarely noticed. Hence, this work mainly focuses on AOB to explore its impact on water quality biosafety in the context of global warming. Research indicates that global warming-induced high temperatures can directly or indirectly promote the growth of AOB, thus leading to nitrification. Further, its metabolites or cellular residues can be used as substrates for the growth of heterotrophic bacteria (e.g., waterborne pathogens). Thus, biofilm may be more persistent in the pipelines due to the presence of AOB. Breakpoint chlorination is usually applied to control such situations. However, switching between this strategy and chloramine disinfection would result in even more severe nitrification and other adverse effects. Based on the elevated microbiological risks in DWDS, the following aspects should be paid attention to in future research: (1) to understand the response of nitrifying bacteria to high temperatures and the possible association between AOB and pathogenic growth, (2) to reveal the mechanisms of AOB-mediated biofilm formation under high-temperature stress, and (3) to develop new technologies to prevent and control the occurrence of nitrification in drinking water distribution system.

Higher sensitivity to Cu2+ exposure of Microcystis aeruginosa in late lag phase is beneficial to its control

Cyanobacterial blooms are always treated in exponential phase, which demands high dosages of algicides (e.g., CuSO4). Actually, cyanobacterial blooms in late lag phase exhibit low cell-density and specific physiological/biochemical characteristics, implying the possibility of controlling blooms in a more efficient and economical way with CuSO4 treatment if cyanobacterial cells in late lag phase can be treated. In this study, the outbreakof a Microcystis bloom was simulated, and Microcystis samples in late lag and exponential phases were treated with CuSO4. The results showed that M. aeruginosa in late lag phase had a higher ratio of dividing-cells, Fv/Fm and intracellular total organic carbon content (TOC) than that in exponential phase, indicating that its metabolic activity was vigorous. M. aeruginosa in late lag phase could more easily be blocked, since a higher decrease in chlorophyll-a, Fv/Fm and membrane integrity occurred under the same dosages of CuSO4 exposure compared to M. aeruginosa in exponential phase. Meanwhile, microcystin release in late lag phase was less than that in exponential phase. Moreover, higher sensitivity in late lag phase was confirmed at the individual level, as the photosynthesis related genes psaB and rbcL were more down-regulated than those in exponential phase. In general, cyanobacteria in late lag phase exhibited higher sensitivity to CuSO4, indicating that CuSO4 treatments in late lag phase can achieve a higher control efficiency and fewer release of microcystin with low-dosages algicide. Hence, it is a more environmentally friendly strategy to control cyanobacterial blooms than the traditional strategy applied in exponential phase.

Recovery of microbiological quality of long-term stagnant tap water in university buildings during the COVID-19 pandemic

Stagnant water can cause water quality deterioration and, in particular, microbiological contaminations, posing potential health risks to occupants. University buildings were unoccupied with little water usage during the COVID-19 pandemic. It's an opportunity to study microbiological quality of long-term stagnant water (LTSW) in university buildings. The tap water samples were collected for three months from four types of campus buildings to monitor water quality and microbial risks after long-term stagnation. Specifically, the residual chlorine, turbidity, and iron/zinc were disqualified, and the heterotrophic plate counts (HPC) exceeded the Chinese national standard above 100 times. It took 4-54 days for these parameters to recover to the routine levels. Six species of pathogens were detected with high frequency and levels (10¹-10⁵ copies/100 mL). Remarkably, L. pneumophilia occurred in 91% of samples with turbidity > 1 NTU. The absence of the culturable cells for these bacteria possibly implied their occurrence in a viable but non-culturable (VBNC) status. The bacterial community of the stagnant tap water differed significantly and reached a steady state in more than 50 days. Furthermore, a high concentration of endotoxin (>10 EU/mL) was found in LTSW, which was in accordance with the high proportion of dead bacteria. The results suggested that the increased microbiological risks require more attention and the countermeasures before the building reopens should be taken.

The prevalence of and risk factors for prostatitis-like symptoms and its relation to erectile dysfunction in Chinese men

The aim of this study was to describe the prevalence of and risk factors for prostatitis-like symptoms and its relation to erectile dysfunction (ED) among southern Chinese men. Data were collected from 2790 men attending the Fangchenggang Area Male Healthy and Examination Survey from September 2009 to December 2009. The prostatitis-like symptoms were assessed by the NIH Chronic Prostatitis Symptom Index and ED was assessed using the 5-item International Index of Erectile Function. Lifestyle and demographic characteristics were obtained through a questionnaire. Prevalence of prostatitis-like symptoms was 12.4% among 2790 Chinese men aged 20-84 years. In smokers who smoked ≥20 cigarettes per day (age-adjusted OR = 1.29; 95% CI = 1.00-1.66; p = 0.04), physical inactivity (age-adjusted OR = 1.31; 95% CI = 1.03-1.66; p = 0.02) was a significant risk factor for prostatitis-like symptoms. Alcohol consumption (daily drinking) also was a risk factor for prostatitis-like symptoms, although the differences were not statistically significant (age-adjusted OR = 1.36; 95% CI = 0.96-1.92; p = 0.07). Those with diabetes may also be at higher risk for prostatitis-like symptoms (age-adjusted OR = 1.37; 95% CI = 0.85-2.21; p = 0.19). In addition, men with ED were more likely to have had prostatitis-like symptoms (age-adjusted OR = 1.86; 95% CI = 0.47-2.36; p < 0.0001), and the ORs increased with increasing severity of ED status (mild ED, mild to moderate ED, and moderate to severe ED were 1.57, 2.62, and 3.24, respectively. Test for trend, p = 0.0001). Our results show that prostatitis-like symptoms are prevalent in Southern China affecting men of all ages. Smoking, drinking, lack of physical activity, and elevated plasma glucose level were associated with an increased risk of prostatitis-like symptoms. In addition, our results reveal that ED accounted for a large proportion (61.5%) among men with prostatitis-like symptoms; we also confirm the magnitude of ED associated with prostatitis-like symptoms. Thus, interventions to evaluate and improve ED might help ameliorate prostatitis-like symptoms and vice versa.

Depletion-induced colloidal crystals at a wall characterised by small-angle X-ray diffraction

Silica photonic colloidal crystals on a flat glass substrate have been grown using the depletion attraction induced by nonadsorbing polymers. The dried samples have been characterised with high-resolution synchrotron small-angle X-ray diffraction and their surface topography has been studied by atomic force microscopy. The presence of long-range ordered crystals with a thickness as large as 90 planes is demonstrated. However, on some places the films are polycrystalline and contain disordered regions.

[The regulation of Lycium barbarum on apoptosis of rat spleen in vitro]

The regulation of Lycium barbarum (LB) on apoptosis of rat spleen induced by hydrocortisone (HYD) was studied in this paper. The results indicated LB could inhibit the apoptosis induced by HYD and the inhibition is dose dependent.

Fractal Dimensions of Coals and Cokes

Using adsorption data, we get formulas for the calculation of fractal dimensions: log[A CO2 (DP) /A N2 (BET) ] = -5.3984(2 - D 1 )/2 and log[A CO2 (BET) /A N2 (BET) ] = -4.9569(2 - D 2 )/2. The fractal dimensions (D ) of 27 coals and 2 cokes have been obtained. The D of coals decreased with the increase of fa and reached a maximum at H/C equal to 0.66 (or C daf about 86%). The fractal dimension is relative to ash and volatiles of coal: D = 2.2237 + 0.6249V daf + 0.8863A d . The relationship between D of coal coke and its conversions (X ) obeys the following equation: D = a exp(-bX ) + c .

Response of kidney bean to concentration and chemical form of cadmium, zinc, and lead in polluted soils

Seven soils which had been polluted with heavy metals from a zinc smelter were sequentially extracted so that Cd, Zn, and Pb could be partitioned into five operationally defined geochemical fractions: exchangeable, carbonate, Fe-Mn oxide, organic, and residual fractions. Kidney beans were planted in the soils to examine the effect of concentration and chemical form of the metals in soil on the growth and metal uptake of the plants. The growth of kidney bean was restricted in heavy metal polluted soils compared with controls. Metal concentration and metal uptake by plants were correlated. The highest relationship was found between amount of metal uptake and the metal concentration in exchangeable + carbonate forms. The uptake of metals was according to their solubility sequence, i.e. Cd > Zn > Pb. The uptake rate of exchangeable + carbonate forms was the same for the three elements.