Potential gap in understanding cyanoHABs: Light-dependent morphological variations in colonial cyanobacterium Microcystis.

Colony formation is a crucial characteristic of Microcystis, a cyanobacterium known for causing cyanobacterial harmful algal blooms (cyanoHABs). It has been observed that as Microcystis colonies grow larger, they often become less densely packed, which correlates with a decrease in light penetration. The objective of this study was to investigate the effects of light limitation on the morphological variations in Microcystis, particularly in relation to the crowded cellular environment. The results indicated that when there was sufficient light (transmittance = 100 %) to support a growth rate of 0.11±0.01 day-1, a significant increase in colony size was found, from 466±15 µm to 1030±111 µm. However, under light limitation (transmittance = 50 % - 1 %) where the growth rate was lower than 0, there was no significant improvement in colony size. Microcystis in the light limitation groups exhibited a loose cell arrangement and even the presence of holes or pores within the colony, confirming the negative correlation between colony size and cell arrangement. This pattern is driven by regional differences in growth within the colony, as internal cells have a significantly lower frequency of division compared to peripheral cells, due to intra-colony self-shading (ICSS). The research demonstrates that Microcystis can adjust its cell arrangement to avoid excessive self-shading, which has implications for predicting and controlling cyanoHABs. These findings also contribute to the understanding of cyanobacterial variations and can potentially inform future research on the diverse phycosphere.

Phosphorus Accumulation in Extracellular Polymeric Substances (EPS) of Colony-Forming Cyanobacteria Challenges Imbalanced Nutrient Reduction Strategies in Eutrophic Lakes.

Extracellular polymeric substances (EPS) are crucial for cyanobacterial proliferation; however, certain queries, including how EPS affects cellular nutrient processes and what are the implications for nutrient management in lakes, are not well documented. Here, the dynamics of cyanobacterial EPS-associated phosphorus (EPS-P) were examined both in a shallow eutrophic lake (Lake Taihu, China) and in laboratory experiments with respect to nitrogen (N) and phosphorus (P) availability. Results indicated that 40-65% of the total cyanobacterial aggregate/particulate P presented as EPS-P (mainly labile P and Fe/Al-P). Phosphorus-starved cyanobacteria rapidly replenished their EPS-P pools after the P was resupplied, and the P concentration in this pool was stable for long afterward, although the environmental P concentration decreased dramatically. A low-N treatment enhanced the EPS production alongside two-fold EPS-P accumulation (particularly labile P) higher than the control. Such patterns occurred in the lake where EPS and EPS-P contents were high under N limitation. EPS-P enrichment increased the P content in cyanobacteria; subsequently, it could hold the total P concentration higher for longer and make bloom mitigation harder. The findings outline a new insight into EPS functions in the P process of cyanobacterial aggregates and encourage consideration of both N and P reductions in nutrient management.

Influence of wind and light on the floating and sinking process of Microcystis.

The vertical migration and accumulation of Microcystis colonies is a critical process in algal bloom formation. This work explored the effect of wind and light intensity on the vertical migration of Microcystis colonies. The wind-driven currents, light-driven changes in mass density of colonies, and the effect of colony size was coupled to simulate the vertical motion of colonies via Ansys Fluent and MATLAB. Results showed that light causes Microcystis to exhibit a 'day-sinking and night-floating' (d-n) phenomenon, however, wind weakens the phenomenon by forming a turbulent drag force that inhibits the vertical movement of Microcystis. This study proposed a kinetic ratio-based method, that there is a specific equilibrium turbulent kinetic energy and when turbulent kinetic energy of the water body is greater than the equilibrium turbulent kinetic energy, the d-n phenomenon does not occur. For Lake Taihu, the wind-driven turbulent kinetic energy is usually greater than the equilibrium turbulent kinetic energy. Therefore, Microcystis colonies may not exhibit the d-n phenomenon. Our findings provide a new theoretical basis for current process-based models in simulating algal blooms in large shallow lakes.

Study of Kinetic Freeze-Out Parameters as a Function of Rapidity in pp Collisions at CERN SPS Energies.

We used the blast wave model with the Boltzmann-Gibbs statistics and analyzed the experimental data measured by the NA61/SHINE Collaboration in inelastic (INEL) proton-proton collisions at different rapidity slices at different center-of-mass energies. The particles used in this study were π+, π-, K+, K-, and p¯. We extracted the kinetic freeze-out temperature, transverse flow velocity, and kinetic freeze-out volume from the transverse momentum spectra of the particles. We observed that the kinetic freeze-out temperature is rapidity and energy dependent, while the transverse flow velocity does not depend on them. Furthermore, we observed that the kinetic freeze-out volume is energy dependent, but it remains constant with changing the rapidity. We also observed that all three parameters are mass dependent. In addition, with the increase of mass, the kinetic freeze-out temperature increases, and the transverse flow velocity, as well as kinetic freeze-out volume decrease.

Cyanobacterial bloom expansion caused by typhoon disturbance in Lake Taihu China.

It remains unclear why the area of a cyanobacterial bloom increases in a shallow lake after a typhoon passes. In this study, the mechanisms of cyanobacterial bloom expansion were investigated by studying meteorological factors, water quality, algal biomass, and bloom area in Lake Taihu before and after typhoons (2007-2016). Our results showed that typhoon-induced sediment resuspension caused a short-term increase in nutrients, but nutrients returned to pre-typhoon levels after the typhoon passages. The short-term nutrient release during a typhoon did not result in an obvious increase in Microcystis cell density in two bays of Lake Taihu (Gonghu and Meiliang). Under strong winds, Microcystis aggregates were uniformly distributed in the water column downwind and then dispersed into different directions by wind-driven currents. In particular, Microcystis in the surface water were transported to the center of Lake Taihu. After a typhoon, dispersed Microcystis refloated and formed blooms. Thus, the bloom area was enlarged compared with before a typhoon. Several days after a typhoon, the bloom area gradually reduced as a result of a steady breeze on the horizontal accumulation of Microcystis.

Calcium promotes formation of large colonies of the cyanobacterium Microcystis by enhancing cell-adhesion.

Large Microcystis colonies can lead to the rapid formation of surface accumulations, which are a globally significant environmental issue. Laboratory studies have shown that Ca2+ can quickly promote non-classical Microcystis colony formation via cell-adhesion, but our knowledge of the changes in the morphology of these colonies during subsequent long-term culture with Ca2+ is limited. In this study, a 72-day cultivation experiment was conducted to determine the long-term effects of Ca2+ on Microcystis colony formation. Laboratory results indicate that Ca2+ causes Microcystis to rapidly aggregate and form a colony through cell adhesion, then colony formation by cell-adhesion lost dominance, owing to the decrease in Ca2+ concentrations caused by precipitation/complexation. Although the initial colony morphology by cell adhesion is sparse, the newly divided cells, without separating from the mother cells, constantly fill the gaps in the original colony at Ca2+ concentrations >40 mg L-1 for a long time, which creates colonies on day 72 with a morphology similar to that of M. ichthyoblabe in Lake Taihu. If the Ca2+ levels in Lake Taihu continue to increase, Microcystis growth rate will decrease only slightly, while the colony proportion of total biovolume and biomass will increase. Moreover, higher Ca2+ concentrations do not affect microcystin content, but promote the content of bound extracellular polysaccharides (bEPS), enabling formation of larger colonies, which may promote Microcystis surface accumulation.

Mechanism of separation and removal of water from dewatered sludge using L-DME to dissolve hydrophilic organic matter.

Difficulties in advanced dewatering of dewatered sludge hinder sludge reduction and resource utilization. L-DME (liquified dimethyl ether) has been recently used for dewatering, but the effect of organic matter dissolution using L-DME during desorption and dehydration on water removal is not clear. In this study, dewatered sludge from urban sewage treatment plants was used to conduct experiments in sequencing dissolution-separation reactors. The changes in the dehydration rate, bound water and various organic matter levels at different times, L-DME additions, and the temperature were measured. The results show that L-DME can remove 90% of water, 100% of lipids, and 8-12% of organic matter in dewatered sludge. L-DME was mixed with the semi-like colloidal sludge, and high separation of water was achieved by mixing the L-DME with water and dissolving the hydrophilic organic matter to convert the solid-like into a two-phase (solid and liquid) substance, which can be easily separated. The dissolution of hydrophilic organic matter such as polysaccharides and proteins by L-DME promotes the conversion of bound water into free water, which is key to total water removal.

Structural Variations Increase the Upper Limit of Colony Size of Microcystis: Implications from Laboratory Cultures and Field Investigations.

Wild Microcystis have highly diverse colonial structures and sizes, including variable colony geometry, cell arrangement, and diameter. These structural and dimensional variations may play an important role in continual, frequent Microcystis blooms during summer and autumn, the cause of which still remains unclear. Here, laboratory cultures and field investigations were applied to assess mechanisms that drive variation in structure and size, as well as factors that influence diversity. The results demonstrated that colonies grew to large sizes at the expense of their structure being loose and inhomogeneous. Furthermore, colonies may spontaneously change structure to relieve the constraints of size in return. Influencing factors (nutrient limits and turbulent shear) tended to promote these variations. Our work highlights that the diversity of Microcystis colonies may be a result of structural variations as survival strategies for gaining a higher upper size limit. Therefore, during seasonal successions, large colonies commonly have porous or loosely arranged structures, such as in M. aeruginosa. Additionally, this study hypothesized three possible transition routes for better understanding structural diversity and variations in Microcystis.

Attenuation of light influences the size of Microcystis colonies.

Colony formation provides excellent advantages for the dominance of Microcystis. However, studies on microenvironments during the process of colony formation are rare, especially regarding intra-colony light usage. This study analyzed the attenuation of light intensity in Microcystis colonies, where most objects followed Lambert-Beer law ( [Formula: see text] ). Intra-colony light limited the maximum thickness of the colony (BMax=4.3×105c-1) and thus affected colony size. Field data showed that the colony size for M. ichthyoblabe was small and limited to approximately 300 µm, while larger colonies were mainly formed by M. aeruginosa and M. wesenbergii respectively. These results imply that the strategies used by morphospecies to allow colonies to tolerate intra-colony light limitation might be different; M. aeruginosa benefited from a reticular growth pattern, and M. wesenbergii colonies were large (500 µm), obtaining a large thickness by lowering cell concentration. The results obtained in this work suggest that M. aeruginosa and M. wesenbergii had more advantages regarding intra-colony light usage, colony size level and bloom formation ability in summer and autumn.

Hydrothermal pretreatment of salvaged cyanobacteria and use of pretreated medium for cultivating Scenedesmus obliquus.

This work studied the hydrothermal Pretreatment of Salvaged Cyanobacteria and used the pretreated slurry as medium for cultivating Scenedesmus obliquus. The cyanobacterial slurry was pretreated by chemical oxidation, hydrothermal treatment and hydrothermal oxidation, and then the cultivation experiment of oil-producing microalgae (Scenedesmus obliquus) was carried out. The results showed that hydrothermal oxidation could transform the hard-to-treat salvaged cyanobacteria into culture medium for microalgae. The oil yield from S. obliquus cultured in that was higher than that in conventional BG11 medium.

Significance of preoperative acute kidney injury in patients with acute type A aortic dissection.

BACKGROUND/PURPOSE: Acute type A aortic dissection (AAD) is a medical emergency with high mortality even with emergency repair. We explored the risk factors for in-hospital mortality and the impact of preoperative acute kidney injury (AKI) in patients with AAD. METHODS: Our hospital database contained records for 156 consecutive patients who underwent AAD repair between March 2000 and February 2013. They were assigned to the in-hospital mortality or the survival group. All data were collected retrospectively. RESULTS: The 30-day mortality, including intraoperative deaths, was 14.1% (22/156). Total in-hospital mortality was 19.2% (30/156). Patients who required preoperative cardiopulmonary resuscitation (CPR) (16.7 vs 3.2%; P = 0.012), or who presented with preoperative cardiac tamponade (46.7 vs 19.0%; P = 0.002), shock/hypotension (56.7 vs 21.4%; P < 0.001), or coma (20.0 vs 6.3%; P = 0.019) had a higher in-hospital mortality rate. There was no difference in in-hospital mortality rate between patients with preoperative AKI or not. Mortality and major complications were significantly correlated with the severity of AKI. Multivariate analysis confirmed that preoperative shock or hypotension (odds ratio = 5.2; 95% CI = 2.2-12.3), and preoperative AKI stage 3 (odds ratio = 4.9; 95% CI = 1.3-19.3) were independent preoperative prognostic factors of in-hospital mortality. CONCLUSION: On the basis of our results, preoperative stage 3 AKI is a crucial prognostic risk factor for patients with AAD repair, Cardiac surgeons should be aware of this condition when dealing with AAD patients.

Modelling the vertical migration of different-sized Microcystis colonies: coupling turbulent mixing and buoyancy regulation.

Exceptional vertical migration ability provides the cyanobacterium Microcystis with competitive advantages in bloom formation and dominance establishment. Studies have been conducted on the vertical migration patterns of Microcystis since the 1970s; however, bloom simulations remain limited. Here, we used a simple model based on the viscous drag force of turbulence and analysed the motion characteristics of Microcystis colonies. The vertical distribution of turbulent kinetic energy (KZ), cell concentration and colony size profiles in Lake Taihu (Meiliang Bay and Gonghu Bay) and the critical vertical turbulent kinetic energy of colonies (TKZ, i.e. the anti-turbulence ability of colonies) were tested. The results showed that, under steady KZ profiles, colonies had relative rest positions (RRPs) where KZ ≈ TKZ and colonies of the same size gathered together. The vertical migration patterns were affected more by turbulence than by density (colony mass density) if the average KZ of the water column (MKZ) was not equal to TKZ. If MKZ ≈ TKZ, the colonies could exhibit a diurnal pattern of sinking at noon and floating upwards before dawn without steady RRPs. Our results suggest that studies on RRPs may offer optimizations for bloom forecast and control in the future due to easier simulation of KZ profiles than that of flow fields.

Fate of distal aorta after acute type A aortic dissection repair: Change and persistency of postoperative false lumen status.

BACKGROUND: The role of false lumen patency related to aortic growth, re-interventions, and post-discharge mortality in the chronic phase of repaired type A acute aortic dissection (TAAAD) remains controversial. We investigated the role of postoperative false lumen patency during long-term follow-up. METHODS: Based on postoperative CT images of 70 candidates, 58 eligible patients without alteration of false lumen status were assigned into three groups: complete patency, partial patency, and complete thrombosis. Aortic growth of 7 levels was analyzed. RESULTS: Persistent complete patency in post-operative TAAAD presents faster expansion of aortic diameter (95% CI, 0.35 to 11.52; P=0.038; B=5.935) and more patients with growth rate>5mm/year (P=0.029). The persistent status of false lumen does not predict post-discharge mortality (P=0.479). History of coronary artery disease (CAD) is the only independent predictor of post-discharge mortality. CONCLUSIONS: In TAAAD patients without change of postoperative false lumen status, completely patent false lumen presents faster aortic growth and more patients with growth rate>5mm/year. False lumen status does not correlate with late survival. Here we provide an insight into persistent postoperative false lumen in TAAAD patients and may help cast light on aortic dissection in this specific subgroup to improve their late outcomes.

To increase size or decrease density? Different Microcystis species has different choice to form blooms.

The buoyancy of Microcystis colonies is a principal factor determining blooms occurrence but the knowledge of seasonal variation in buoyancy is quite poor because of challenge in analysis method. In this study, a method based on the Stokes' Law after researching on the effects of shapes on settling velocity of Microcystis colonies, whose gas vesicles were collapsed, to accurately measure density was established. The method was used in Lake Taihu. From January to May, mean density of Microcystis colonies decreased from 995 kg m-3 to 978 kg m-3 and then increased to 992 kg m-3 in December. The density of colonies in different Microcystis species was in the order M. wesenbergii > M. aeruginosa > M. ichthyoblabe. For all the Microcystis species, the density of colonies with gas vasicles increased significantly along with the increase of colony size. Our results suggested that the main driving factor of Microcystis blooms formation in Lake Taihu was low density for M. ichthyoblabe from May to July but was large colony size for M. wesenbergii and M. aeruginosa from August to October.

High nutrient concentration and temperature alleviated formation of large colonies of Microcystis: Evidence from field investigations and laboratory experiments.

Correlations between Microcystis colony size and environmental factors were investigated in Meiliang Bay and Gonghu Bay of Lake Taihu (China) from 2011 to 2013. Compared with Gonghu Bay, both nutrient concentrations and Microcystis colony sizes were greater in Meiliang Bay. The median colony size (D50: 50% of the total mass of particles smaller than this size) increased from April to August and then decreased until November. In both bays, the average D50 of Microcystis colonies were <100 µm in spring, but colonies within moderate-size (100-500 µm) dominated in summer. The differences in colony size in Meiliang Bay and Gonghu Bay were probably due to horizontal drift driven by the prevailing south wind in summer. Redundancy analysis (RDA) of field data indicated that colony size was negatively related to nutrient concentrations but positively related to air temperature, suggesting that low nutrient concentrations and high air temperature promoted formation of large colonies. To validate the field survey, Microcystis colonies collected from Lake Taihu were cultured at different temperatures (15, 20, 25 and 30 °C) under high and low nutrient concentrations for 9 days. The size of Microcystis colonies significantly decreased when temperature was above 20 °C but had no significant change at 15 °C. The differences in temperature effects on colony formation shown from field and laboratory suggested that the larger colonies in summer were probably due to the longer growth period rather than the higher air temperature and light intensity. In addition, colony size decreased more significantly at high nutrient levels. Therefore, it could be concluded that high nutrient concentration and temperature may alleviate formation of large colonies of Microcystis.

Effects of linear alkylbenzene sulfonate (LAS) on the interspecific competition between Microcystis and Scenedesmus.

The widespread use of detergents increases the concentration of surfactant in lakes and reservoirs. High surfactant loads produces toxicity to algae; however, the influence of the increasing surfactant on the competition between algae is not clear. In this paper, different amounts of linear alkylbenzene sulfonate (LAS) were added to test the effects of LAS on the competition between Microcystis aeruginosa and Scenedesmus obliquus under eutrophic condition. In single culture, the growth of S. obliquus was promoted under lower LAS concentrations (1 and 20 mg L(-1)), but cell density of S. obliquus reduced when treated with higher LAS concentration (100 mg L(-1)). The growth of M. aeruginosa was inhibited markedly with 20 and 100 mg L(-1) LAS. Compared with single culture, the result was opposite in co-cultures and the cell density of S. obliquus increased significantly when treated with LAS of 1, 20, and 100 mg L(-1). The specific growth rates of S. obliquus and M. aeruginosa in both cultures were 0.4-0.5 day(-1) and 0.6-0.7 day(-1), respectively, except that the specific growth rate of M. aeruginosa in both cultures treated with 100 mg L(-1) LAS was about 0.2 day(-1). M. aeruginosa dominated over S. obliquus in the co-culture without LAS, while the competition was completely opposite with the addition of 20 mg L(-1) LAS. The growth of S. obliquus treated with 20 mg L(-1) LAS was not affected significantly in single culture but was promoted by 75 % in co-culture. Moreover, the growth of S. obliquus in co-culture treated with 100 mg L(-1) LAS was promoted by more than 97 %. These results suggested that the increasing LAS would overturn the competition of algae in freshwater ecosystems.

Pyrexia of postimplantation syndrome for patients undergoing (thoracic) endovascular aortic repair.

OBJECTIVE: While a clear definition and explanation to postimplantation syndrome are yet to be clarified, this study aims to investigate its nature by retrospectively analyzing postprocedural fever pattern with patient characteristics, procedure details, and responses to medical treatments. MATERIALS AND METHOD: Twenty-three patients undergoing (thoracic) endovascular aortic repair between January 2011 and January 2012 were studied for their postimplantation fever pattern. The demographic information, procedure specifications, and postprocedure care details were collected for statistical analysis to find associations between fever pattern and the above-mentioned parameters. RESULTS: None of the postprocedure microbial studies returned positive. Longer fever duration and higher fever frequency are statistically associated with younger age (95% confidence interval [CI] -0.82 to -0.04, p < 0.04 and 95% CI -0.74 to -0.01, p = 0.05 respectively), longer procedure duration (95% CI 0.35-0.90, p < 0.01 and 95% CI 0.02-0.75, p = 0.04 respectively), more entry sites created (95% CI 0.09-0.95 p < 0.03 and 95% CI 0.02-0.88, p < 0.04, respectively), and longer stent grafts implanted (95% CI 0.27-0.89, p < 0.01, fever duration only). Fever pattern and different postprocedure medical treatment did not convey a statistically significant association, but effective and dramatic response to steroids was observed in patients with persistent pyrexia that responded poorly to antibiotics and nonsteroidal anti-inflammatory drugs. CONCLUSION: Our findings support the view that postimplantation syndrome is caused by host immune response; none of our cases are related with infection and no benefits were observed from the prolonged use of antibiotics, thus adding to the plausibility of employing steroids as part of the postprocedure care scheme.

Serum levels of interleukin-1 beta, interleukin-6 and melatonin over summer and winter in kidney deficiency syndrome in Bizheng rats.

OBJECTIVE: To observe the seasonal changes in serum levels of interleukin-1 beta (IL-1ß), interleukin-6 (IL-6) and melatonin (MT) in Bizheng rat model, and explore the relationship between MT and the pathogenesis of rheumatoid arthritis. METHODS: One hundred and sixty Sprague-Dawley rats were randomly divided into four groups in summer (n=80) and winter (n=80) respectively: normal group, collagen-induced arthritis (CIA) model group, operation group, and sham-operation group (n=20 in each group). The CIA model group was injected with collagen emulsion at the base of the tail to induce arthritis. The rats in the operation group received pineal gland resection, and 7 days after the first operation, underwent testectomy or oophorectomy. The rats in the sham-operation group were operated to ligature the sagittal sinus, without extracting the pineal gland. After the operations, the operation group and the sham-operation group both were immunized as the CIA group was. The serum levels of IL-1ß, IL-6 and MT in different groups were measured by radioimmunoassay. RESULTS: Compared with the normal group, the serum levels of IL-1ß and IL-6 increased in the CIA model, operation, and sham-operation groups both in summer and in winter (IL-1ß in summer, P=0.008, P<0.01, P=0.012; IL-1ß in winter, P=0.019, P<0.01, P=0.027; IL-6 in summer, P=0.028, P<0.01, P=0.024; IL-6 in winter, P=0.006, P<0.01, P=0.008). In the operation group, the serum levels of IL-1ß and IL-6 in winter were higher than in summer, but with no statistically significant differences (P=0.844, 0.679). Compared with the normal group, the serum level of MT significantly increased in summer and winter in both the CIA model group (P=0.002, 0.008) and the sham-operation group (P=0.003, 0.007), while significantly decreased in the operation group (P=0.023, 0.003). There was no significant difference in MT level in the operation group between summer and winter (P=0.947). CONCLUSIONS: The increase of serum levels of IL-1ß and IL-6 may exacerbate the inflammatory reaction and cause a more severe condition in the rheumatoid arthritis. The concentrations of IL-1ß, IL-6, and MT correspond with the change of seasons, confirming that there are connections between nature and human body.