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Decreased soil pH weakens the positive rhizosphere effect on denitrification capacity

Pedosphere 2024年第5期34卷 905-915页

作者： Jun WANG Zongxiang ZHANG Fei LIANG Zhao CHE Yongkang WEN Manyu ZHANG Wenjun JIN Zhaorong DONG He SONG College of Agronomy Anhui Agricultural University Key Laboratory of Arable Land Quality Monitoring and Evaluation Ministry of Agriculture and Rural Affairs Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences (CAAS) College of Resources and Environmental Sciences China Agricultural University

The stimulating effect of rhizosphere on denitrification is considered to be an unavoidable loss of soil nitrogen（N） and detrimental to crop N use efficiency,which is regulated by crop growth and soil properties. Soil acidification, occurring rapidly in many intensive farming lands, affects both crop growth and soil properties, thereby altering rhizosphere effect on denitrification. However, the mechanism by which soil acidification regulates rhizosphere denitrification still remains unclear. Here, we determined the denitrification capacity（DC） and associated community compositions of nirK-and nirS-type denitrifiers in maize rhizosphere and bulk soils at four acidity gradients（pH = 6.8, 6.1, 5.2, and 4.2）. Results showed that the stimulating effect of rhizosphere on DC strongly depended on soil pH. Compared to bulk soil, rhizosphere soil had significantly higher DC at pH 5.2, but not at pH of 4.2. With increasing soil acidity, the stimulation of rhizosphere on DC（calculated as the difference in DC between rhizosphere and bulk soils） decreased from 8.01 to 0.01 mg N ***, soil acidification significantly reduced the differences in dissolved organic carbon（DOC） and abundance of key nirK-type denitrifier taxa between rhizosphere and bulk soils, both of which were positively related to the stimulation of rhizosphere on DC. These findings demonstrated that soil acidification could weaken the positive rhizosphere effect on denitrification via regulated C availability and associated nirK-type denitrifier community, potentially reducing N loss risk in rhizosphere soil. The independent role of soil p H should be fully considered when modelling N behaviour in plant-soil systems.

关键词： bacterial abundance denitrifier community dissolved organic carbon operational taxonomic unit soil acidification

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Abiotic Factors Associated with abundance Dynamics and Antibiotic Multidrug Resistance of Escherichia coli and Enterococcus faecalis Isolated from Some Ombessa Aquatic Systems (Central Cameroon Region)

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Journal of Geoscience and Environment Protection 2024年第9期12卷 335-369页

作者： Lucie Leme Banock Blandine Pulchérie Tamatcho Kweyang Fabrice Ezo’o Mengo Stephane Arthur Noah Eric Donald Mbo Zang Olive Vivien Noah Ewoti Laboratory of Hydobiology and Environment Department of Animal Biology and Physiology Faculty of Sciences University of Yaounde 1 Yaounde Cameroon Laboratory of Microbiology of Soil and Environment Department of Microbiology Faculty of Sciences University of Yaounde 1 Yaounde Cameroon

The present study conducted in the town of Ombessa aims to assess the influence of abiotic factors on the abundance dynamics and antibiotic susceptibility of Escherichia coli and Enterococcus faecalis isolated from some aquatic systems from February to July 2022, monthly samples were taken at 10 water points used by the population (8 groundwater points and 2 surface water points). Samples were analyzed for physico-chemical parameters such as temperature, pH, electrical conductivity. Bacteriological variables such as BHAM, E. coli and E. faecalis abundances were also assessed. Antibiotic susceptibility of E. coli and E. faecalis was assessed using 06 antibiotics using the Kirby-Bauer diffusion disk method. The results show that bacterial abundances were the highest in surface waters. bacterial densities were the highest in May and the lowest in February. The average densities recorded were 3845 CFU/100mL for BHAM, 380 CFU/100mL for E. coli and 14 CFU/100mL for E. faecalis in groundwater;and 8583 CFU/100mL for BHAM, 6878 CFU/100mL for E. coli and 812 CFU/100mL for E. faecalis in surface water. Antibiotic susceptibility tests showed that these bacterial species are sensitive to Gentamicin, Chloramphenicol, Azithromycin and Ciprofloxacin. They are all resistant to Trimethoprim/Sulfamethoxazole, E. coli is resistant to Doxycycline and E. faecalis has an intermediate sensitivity to Gentamicin. Overall, the Multiresistance to Antibiotics (MRA) indices obtained were above 0.2, indicating the presence of multidrug resistance in bacterial communities. The physico-chemical properties of the water varied over time and space, but on the whole remained below the threshold values of WHO guidelines. The degree of linkage between abiotic water variables and bacteriological parameters has shown that bacterial densities are more abundant in rainy seasons and increased O2 levels favor bacterial growth, while TSS, CO2 and dissolved nitrate levels affect the sensitivity of these bacteria

关键词： bacterial abundance Multiresistance Abiotic Aquatic

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abundance and spatial dynamics of bacterioplankton in the Seven Rila Lakes,Bulgaria

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Chinese Journal of Oceanology and Limnology 2010年第3期28卷 451-458页

作者： Silvena BOTEVA Ivan TRAYKOV Anelia KENAROVA Valentin BOGOEV Biology Faculty Sofia University"St. Kliment Ohridski"8 Dragan Tzankov Blvd. 1611 Sofia Bulgaria

In the high mountain oligotrophic Seven Rila Lakes (2 095–2 535 m a.s.l.) bacterial abundance was recorded in July and September 2006. In July, bacterial abundance (average (3.32±2.5)×105 cell/ml) in the lakes correlated negatively with elevation, while in September (average (26.39±7.1)×105 cell/ml) this pattern was altered and the greatest abundance of bacteria occurred at the highest ((39.05±1.5)×105 cell/ml) and the lowest ((30.63±6.0)×105 cell/ml) elevated lakes. Regression analyses suggested that the principal factor controlling bacterial abundance, in both July and September, was inorganic nitrogen (NO3-N and NH4-N; R2=0.70, Pbacterial abundance.

关键词： bacterial abundance high mountain lake Rila Mountain environmental factor bottom-up control

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Soil organic carbon and phosphorus availability regulate abundance of culturable phosphate-solubilizing bacteria in paddy fields

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Pedosphere 2020年第3期30卷 405-413页

作者： Arvind KUMAR Lal Chand RAI Molecular Biology Section Laboratory of Algal BiologyCenter of Advanced Study in BotanyBanaras Hindu UniversityVaranasi 221005India Department of Biotechnology Guru Ghasidas VishwavidyalayaBilaspur 495009India

Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the Indo-Gangetic Plain, India were isolated, and their abundance was attempted to be correlated with the physicochemical characteristics of the soils. Ninety-four PSB were isolated on Pikovskaya’s agar medium, and quantitative phosphate solubilization was evaluated using NBRIP medium. The isolates solubilized P up to a concentration of 1 006 μg mL-1 from tricalcium phosphate with the secretion of organic acids. These isolates were identified by 16 S rRNA gene sequence comparison, and they belonged to Gammaproteobacteria(56 isolates),Firmicutes(28 isolates), Actinobacteria(8 isolates), and Alphaproteobacteria(2 isolates). Phylogenetic analysis confirmed the identification by clustering the isolates in the clade of the respective reference organisms. The correlation analysis between PSB abundance and physicochemical characteristics revealed that the PSB population increased with increasing levels of soil organic carbon, insoluble P, K+, and Mg2+. The promising PSB explored in this study can be further evaluated for their biofertilizer potential in the field and for their use as potent bio-inoculants.

关键词： bacterial abundance insoluble P organic acids phosphate solubilization phylogenetic analysis 16S rRNA gene

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Five-year bio-monitoring of aquatic ecosystems near Artigas Antarctic Scientific Base, King George Island

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Advances in Polar Science 2015年第1期26卷 102-106页

作者： María A.Morel Victoria Bra?a Cecilia Martínez-Rosales Célica Cagide Susana Castro-Sowinski Microbiología Molecular Instituto de Investigaciones Biológicas Clemente Estable (IIBCE) Bioquímica y Biología Molecular Facultad de Ciencias Universidad de la República

Fildes Peninsula, in King George Island, Antarctica, has a great concentration of international facilities, and it has clearly been affected by human activities. The objective of this 5-year study was to assess the impact of anthropogenic activities on the bacterial abundance in water bodies close to Artigas Antarctic Scientific Base （BCAA, in Spanish Base Cientifica Antdrtica Artigas）. Water samples from areas under different human influence （Uruguay Lake, nearby ponds, and meltwater from Collins Glacier） were aseptically collected and refrigerated until processed. The number of heterotrophic bacteria and Pseudomonas spp. was analyzed using a culture-dependent approach. Physico-chemical properties of the water samples （temperature, pH, and conductivity） were also determined. Results showed that water from the highly affected area, Uruguay Lake, where the pump that provides water to the BCAA is located, did not suffer significant fluctuations in heterotrophie bacterial abundance （10^4- 10^5 ***^-1）; however, Pseudomonas abundance increased until becoming the predominant population. In other water samples, the number of heterotrophie bacteria and Pseudomonas gradually increased during this 5-year study, by 2014 reaching similar values to those observed for Uruguay Lake. The implications of human activities on Antarctic bacterial abundance are discussed.

关键词： anthropogenic activities water bodies bacterial abundance

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空气中微生物随亚洲沙尘的扩散的初步结果(英文)

空气中微生物随亚洲沙尘的扩散的初步结果(英文)

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第八届海峡两岸气溶胶技术研讨会暨第三届空气污染技术研讨...

作者：张代洲原和崇袁红莉张莹时妍凝柿川真纪子熊本县立大学环境共生学部中国农业大学生物学院日本金泽大学工学部

Bacteria as prominent biological particles in the atmosphere affect climate change and global hydrological cycles by acting as nuclei of ice-cloud formation,and the constant dispersal of viable bacteria is considered as a link between disjunct bacterial communities in distant areas. With a few data recently obtained,we show that concentrated bacteria including viable and non-viable bacteria are widespread with Asian dust plumes. Dust emission is likely a substantial source of bacteria as well as mineral particles in the atmosphere. In addition to the importance on climate change and ecosystem development,long-range transported dust deserves a new interdisciplinary study in respect to their potential functions weakening the geographical gradient of microorganism diversities and blurring distinctions between microbial species in global scale.

关键词： bacterial abundance dust plume long-range transport

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