Distinct microbial characteristics of the robust single-stage coupling system during the conversion from anammox-denitritation to anammox-denitratation patterns.

Simultaneous anammox-denitrification is effectively operated in two types, i.e., the anammox-denitritation (SAD pattern) and the anammox-denitratation (PDA pattern). The nitrate derived from inevitable nitrite oxidization likely determines the practical operational pattern of the coupling system, while little information is available regarding the microbial characteristics during the pattern conversion. Here, the single-stage bioreactor coupling anammox with denitrification was operated under conditions with a changed ratio of influent nitrite and nitrate. Results showed that the bioreactor exhibited a robust performance during the conversion from SAD to PDA patterns, corresponding with the total nitrogen removal efficiency ranging from 89.5% to 92.4%. Distinct community structures were observed in two patterns, while functional bacteria including the genera Denitratisoma, Thauera, Candidatus Brocadia, and Ca. Jettenia steadily co-existed. Meanwhile, the high transcription of hydrazine synthase genes demonstrated a stable anammox process, while the up-regulated transcription of nitrite and nitrous oxide reductase genes indicated that the complete denitrification process was enhanced for total nitrogen removal during the PDA pattern. Ecologically, stochastic processes dominantly governed the community assembly in two patterns. The PDA pattern improved the interconnectivity of communities, especially for the cooperative behaviors between dominant denitrifying bacteria and low-abundant species. These findings deepen our understanding of the microbial mechanism underlying the different patterns of the coupling system and potentially expand its engineering application.

Dynamics of bacterioplankton communities in the estuary areas of the Taihu Lake: Distinct ecological mechanisms of abundant and rare communities.

As the crucial confluences of rivers and lakes, the estuary areas with varied hydrodynamic exchanges intensively affect the bacterioplankton communities, whereas the ecological characteristics of the bacterioplankton in the areas have not been well understood. Here, the distribution patterns and assembly mechanisms of bacterioplankton communities in the estuary areas of the Taihu Lake were investigated using high-throughput sequencing and multivariate statistical analyses. Our results showed obvious seasonal variations in bacterioplankton diversity and community composition, which had significant correlations with water temperature. Neutral and null models together revealed that stochastic processes (especially dispersal limitation) were the major processes in shaping the communities across different seasons. By contrast, heterogeneous selection in deterministic processes exhibited increased impacts on community assembly during summer and autumn, which was significantly related to the comprehensive water quality index (WQI) rather than any single factor. In this study, rare communities displayed more pronounced seasonal dynamics compared to abundant communities, likely due to their sensitivity towards environmental factors. Accordingly, the heterogeneous selection of deterministic processes largely shaped the rare communities. These results enriched our understanding of the assembly mechanisms of bacterioplankton communities in estuary areas and emphasized the specific co-occurrence patterns of abundant and rare communities.

Temporal differentiation in the adaptation of functional bacteria to low-temperature stress in partial denitrification and anammox system.

Despite reliable nitrite supply through partial denitrification, the adaptation of denitrifying bacteria to low temperatures remains elusive in partial denitrification and anammox (PDA) systems. Here, temporal differentiations of the structure, activity, and relevant cold-adaptation mechanism of functional bacteria were investigated in a lab-scale PDA bioreactor at decreased temperature. Although distinct denitrifying bacteria dominated after low-temperature stress, both short- and long-term stresses exerted differential selectivity towards the species with close phylogenetic distance. Species Azonexus sp.149 showed high superiority over Azonexus sp.384 under short-term stress, and long-term stress improved the adaptation of Aquabacterium sp.93 instead of Aquabacterium sp.184. The elevated transcription of nitrite reductase genes suggested that several denitrifying bacteria (e.g., Azonexus sp.149) could compete with anammox bacteria for nitrite. Species Rivicola pingtungensis and Azonexus sp.149 could adapt through various adaptation pathways, such as the two-component system, cold shock protein (CSP), membrane alternation, and electron transport chain. By contrast, species Zoogloea sp.273 and Aquabacterium sp.93 mainly depended on the CSP and oxidative stress response. This study largely deepens our understanding of the performance deterioration in PDA systems during cold shock and provides several references for efficient adaptation to seasonal temperature fluctuation.

Shift of human pathogen community composition and their potential human health risk after supply suspension in tap water.

Water supply suspension-restoration can occur frequently due to the overhauling of civil infrastructure in developing countries and the shutdown of commercial buildings during the pandemic. For comprehensive insights into the effects of water supply suspension-restoration, this study characterized the variations of the pathogen community composition of the tap water and their infection risk under different water supply scenarios. Metagenomic sequencing revealed a significant change of the human pathogen profiles, among which the most dominant pathogen changed from Pseudomonas aeruginosa (4.91%) to Acinetobacter johnsonii (0.59%). Furthermore, absolute quantification of pathogens by propidium-monoazide-qPCR revealed that the abundance of the three typical pathogens (Pseudomonas aeruginosa, Mycobacterium avium and Salmonella sp.) showed an increase of 2.44 log to 3.60 log immediately after water supply suspension-restoration and did not return to the normal level even after 2-h supply restoration, except for Pseudomonas aeruginosa. Quantitative microbial risk assessment suggested the infection risks of the three pathogens arising from direct utilization of tap water under stable water supply, including dermal exposure and oral intake, were all above the threshold of 10-4, and evidently increased after water supply suspension-restoration. This study warns us against the risk induced by the pathogens in tap water, especially after water supply suspension-restoration.

Ten-year epidemiology of chemical burns in western Zhejiang Province, China.

BACKGROUND: Chemical burns occur frequently in western Zhejiang Province. This study documents the epidemiology of chemical burns in the region using burn data from a local specialized hospital. Results from this analysis will assist in the planning of prevention strategies for high-risk occupations and groups. METHODS: A 10-year retrospective analysis was conducted for all patients with chemical burns admitted to the Department of Burn and Plastic Surgery from January 2004 to December 2013. Information obtained for each patient included demographics (gender, age, occupation and education), location of the burn, cause of the burn, and categories of chemicals. Data regarding the season of admittance, prehospital treatment, wound site/size (area, region, and depth), accompanying injuries, operations, length of hospital stay and mortality were also assessed. RESULTS: A total of 690 patients (619 males, 71 females; average age: 30.6±12.4 years) were admitted to the department for chemical burns. Over the 10-year period, the incidence of chemical burns showed an increasing tendency. Chemical burns occurred most frequently in patients aged 20-59 years (94.79%). Most of the chemical burns were work-related, primarily in private enterprises (47.97%) and state-owned enterprises (24.93%). Operations (68.99%) and machine problems (17.26%) were the main causes of chemical burns in the workplace. With regard to burns caused by chemicals, most were caused by acids (72.01%), with hydrofluoric acid and sulphuric acid causing 51.45%. Most chemical burns occurred in the summer and autumn seasons (61.02%). The burn size was <10% of the total body surface area (TBSA) for 445 patients (64.49%), while only 26 patients (3.76%) had burns covering >40% TBSA. The most common burn sites were the upper extremities (31.57%), lower extremities (19.86%), and head and neck (28.83%). Most patients (581 (84.20%)) received water washing treatment on site immediately after exposure. The most common accompanying injuries included inhalation injury, ocular burns and digestive tract injury. The average hospital stay was 17.0±23.1 days (range 1-333 days). Surgery was performed in 146 patients (21.16%), and the overall mortality rate was 0.58%. CONCLUSIONS: Chemical burns are preventable. The high morbidity of chemical burns in western Zhejiang Province is related to the industrial structure of the area. Governmental management in the fields of production, transportation, and utilization of chemicals could be improved. Workplaces have the responsibility to provide safe work environments and equipment, as well as occupational education and safety training for high-risk work groups.

Management of a patient with thermal burns and para-chloronitrobenzene poisoning.

Para-chloronitrobenzene (p-CNB), a hazardous and toxic substance, is widely used as an intermediary in chemical industries. p-CNB can cause methaemoglobinaemia due to electron-withdrawing properties of the nitro and chlorine groups. We present a case of a 23-year-old man suffering from thermal burns and p-CNB poisoning. In this case, severe methaemoglobinaemia was caused by the absorption of p-CNB through the burn wounds. Despite active treatment, such as the antidote of methylene blue, the patient's methaemoglobinaemia progressed, with slowly increasing methaemoglobin (MetHb) level. This case highlights the complexity and difficulty of managing this type of injury. To our knowledge, this case can be the first case report describing methaemoglobinaemia induced by p-CNB in a patient with thermal burns.

A review of treatment strategies for hydrofluoric acid burns: current status and future prospects.

Hydrofluoric acid (HF), a dangerous inorganic acid, can cause severe corrosive effects and systemic toxicity. HF enters the human body via where it contacts, such as skin and mucosa, alimentary and respiratory tracts, and ocular surfaces. In the recent years, the incidence of HF burn has tended to increase over time. The injury mechanism of HF is associated primarily with the massive absorption of HF and the release of hydrogen ions. Correct diagnosis and timely treatment are especially important for HF burns. The critical procedure to treat HF burn is to prevent on-going HF absorption, and block the progressive destruction caused by fluoride ions. Due to the distinct characteristics of HF burns, the topical treatment, as well as systemic support, has been emphasised. Whereas, management of patients with HF burns remains a great challenge in some situations. To date, there has been no widely accepted protocol for the rescue of HF burns, partly due to the diversity of HF burns. This paper overviews the current status and problems of treatment strategies for HF burns, for the purpose of promoting the future researches and improvement.

[Comparison of various methods of early management of hydrofluoric acid burn in rabbits].

OBJECTIVE: To compare the effects of different kind of methods in the management of hydrofluoric acid burn in early postburn stage in rabbits. METHODS: Thirty-three rabbits were inflicted with burn by 55% of hydrofluoric acid covering 5% TBSA, and were randomly divided into 3 groups, i.e. A (n = 13, with 5 ml.kg(-1).h(-1)of isotonic saline intravenous infusion), B (n = 10, with isotonic saline and 50 g/L of calcium gluconate infusion in dose of 20 mg/kg at different time points), and C (n = 10, with the same treatment as B group, and with excision of burn wound at 0.5 post burn hour) groups. The serum levels of fluorine and calcium were determined before and after various postburn hours, and the mortality rate was statistically analyzed. RESULTS: (1) The serum level of fluorine in A (8.37 +/- 2.62 mg/L) and B (8.59 +/- 2.25 mg/L) groups reached the peak value at 1 postburn hour (PBH), which was 107 times higher than that before the burn injury. The serum level of fluorine in B group was significantly lower than that in A group at 24 PBH (P < 0.05), while that in C group declined to (6.20 +/- 0.23) mg/L, which was obviously lower than that in A and B groups (P < 0.01). (2) The serum calcium level declined after burns, reaching the lowest level at 8 to 12 PBH. and began to increase at 24 PBH. Compared with normal calcium value, the serum level of calcium in A, B and C groups declined to as much as 46%, 32% and 26%, respectively. Statistically significant difference was found between C and B groups (P < 0.01). (3) The mortality rate in the three groups within 72 PBH were 30.8%, 12.5% and 0.0%, respectively. CONCLUSION: Early removal of burn area and calcium supplementation could help quickly decrease blood fluorine, reverse the fatal hypocalcemia and the multiple systemic toxic injury in rabbits inflicted with hydrofluoric acid injury.