Contribution of ammonia-oxidizing archaea and bacteria to nitrification under different biogeochemical factors in acidic soils.

Nitrification in soils is an essential process that involves archaeal and bacterial ammonia-oxidizers. Despite its importance, the relative contributions of soil factors to the abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) and their nitrification performances are seldom discussed. The aim of this study was to determine the effects of AOA and AOB abundance and different environmental conditions (pH, TC, TN, moisture, and temperature) on nitrification performance. The soils of the long-term fertilized tea orchards and forests were sampled in the field, and nitrification experiments were conducted in the laboratory. The acid soils were collected from the field and used in laboratory incubation experiments to calculate the nitrification rate, including the net nitrification rate (NN rate), nitrification potential (NP), and nitrification kinetics. The basic parameters, different forms of nitrogen content, and AOA and AOB amoA gene copies were also analyzed. Compared with the forest soil, the tea orchard soil had a lower pH and higher nitrogen content (p < 0.05). The AOA and AOB abundance in the soils of the forests and tea orchards were pH-dependent. The NN rate and NP had good relationships with AOA or AOB in the forest soil; however, poor relationships were observed in the tea orchard soil. When pH < 4, the performances of AOA and AOB were restricted by pH and the environment, especially in long-term fertilized farmlands. Long-term fertilization can cause soil acidification, which regulates the abundance of AOA and AOB and their nitrifying ability. The soil environment rather than AOA or AOB could control nitrification in long-term fertilized farmlands with a pH below 4. These findings could improve fertilization efficiency and control nutrient runoff in hilly agricultural ecosystems.

Systematic review of negative pressure wound therapy for head and neck wounds with fistulas: Outcomes and complications.

Fistula formation in head and neck wounds is considered one of the most challenging complications that a head and neck reconstructive surgeon may encounter. The current mainstay of treatment is aggressive surgical debridement followed by vascularised soft tissue coverage. Negative pressure wound therapy (NPWT) has been successfully used for the closure of complicated wounds for decades. This study analysed the outcomes and complications of NPWT in the management of head and neck wounds with fistulas. A systematic search of studies published between January 1966 and September 2019 was conducted using the PubMed, MEDLINE, EMBASE, and SCOPUS databases and using the following key words: "negative pressure wound therapy," "head and neck," and "fistula." We included human studies with abstract and full text available. Analysed endpoints were rate of fistula closure, follow-up duration, and complications if present. Nine retrospective case series (Level IV evidence) that collectively included 122 head and neck wounds with orocutaneous fistulas, pharyngocutaneous fistulas, and salivary contamination were examined. The number of patients included in each study ranged from 5 to 64. The mode of NPWT varied among the included studies, with most adopting a continuous pressure of -125 mm Hg. Mean durations of NPWT ranged from 3.7 to 23 days, and the reported fistula closure rate ranged from 78% to 100%. To achieve complete wound healing, six studies used additional procedures after stopping NPWT, including conventional wound dressings and vascularised tissue transfer. Information regarding follow up was provided in only three of the nine studies, where patients were followed for 5, 10, and 18 months. No serious adverse events were reported. NPWT for head and neck wounds with fistulas may be considered a safe treatment method that yields beneficial outcomes with a low risk of complications. The current data originated mainly from studies with low levels of evidence characterised by heterogeneity. Therefore, definitive recommendations based on these data cannot be offered. Additional high-quality trials are warranted to corroborate the findings of this systematic review.