Abundance Of Nitrogen-fixing Bacteria Research Articles

Arginine and methionine increase the enzymatic activity of microbes involved in N and P cycles in arid soil from the Chihuahuan desert

Root exudates are mainly composed of sugars, organic acids, and amino acids. These are carbon sources that recruit beneficial bacterial communities in the rhizosphere. However, the composition of the root exudates is variable and mainly unknown for plants from arid lands, such as Agave lechuguilla Torr. This work studied the effect of different metabolites identified in the rhizosphere of A. lechuguilla Torr. (Maltose, lactose, oxalic and tartaric acids, arginine, and methionine), over the enzymatic activity and abundance of nitrogen-fixing bacteria and organic phosphorus mineralizing bacteria, as well as the changes in the nutrient availability in the soil. It was found that only the amino acids increased the nitrogenase and phosphatase activity, and these increments were reflected in the available nutrient concentration in the soil. Likewise, the presence of carbon and nitrogen from the amino acids may reduce the C:N ratio in the soil, enhancing the mineralization of organic matter and the concentration of ammonia, nitrite, and nitrates. This work shows the complexity of the nutrient recycling process in the soil and the essential role of bacteria in making nutrients available to plants. Understanding this process could aid in improving the establishment of plants in eroded ecosystems or under the harsh conditions of arid environments.

Responses of Nitrogen-Fixing Bacteria Communities to Elevation, Season, and Slope Aspect Variations in Subtropical Forests of Yunnan, China

Nitrogen-fixing bacteria play a significant role in tropical forest ecosystems. However, little is known about the comprehensive effects of altitude gradient (1000–2600 m), seasons (October, January, April, and July), and slope aspects (east and west) on the abundance and diversity of nitrogen-fixing bacteria in subtropical forest. Q-PCR and PCR-DGGE methods were performed to explore the abundance and diversity of nitrogen-fixing bacteria, respectively, in the Ailao Mountain subtropical forest. Our results showed that the abundance of nitrogen-fixing bacteria was highest in October and December, whereas it was lowest in April and July. Moreover, there was no difference in the total number of soil nitrogen-fixing bacteria on the eastern and western slopes. The diversity of soil nitrogen-fixing bacteria is higher at low and medium altitudes, but lower at high and medium altitudes with increasing altitude, and similar variation in the eastern and western slopes as well. Moreover, the most influential factors affecting the abundance of nitrogen-fixing bacteria was NH4+-N and herbal coverage, while those most affecting the diversity of nitrogen-fixing bacteria were NH4+-N and NO3−-N. In addition, permutational multivariate analysis demonstrated that the season had the greatest effects on the abundance of nitrogen-fixing, whereas altitude had the greatest effects on the diversity of nitrogen-fixing bacteria. These findings provide evidence that the variation in nitrogen-fixing bacteria is affected by multiple factors (altitudes, seasons and slope aspects) in the subtropical forests of Yunnan, China.

The Relationship between the Community Structure and Function of Bacterioplankton and the Environmental Response in Qingcaosha Reservoir

Phytoplankton and bacterioplankton play a vital role in the structure and function of aquatic ecosystems, and their activity is closely linked to water eutrophication. However, few researchers have considered the temporal and spatial succession of phytoplankton and bacterioplankton, and their responses to environmental factors. The temporal and spatial succession of bacterioplankton and their ecological interaction with phytoplankton and water quality were analyzed using 16S rDNA high-throughput sequencing for their identification, and the functions of bacterioplankton were predicted. The results showed that the dominant classes of bacterioplankton in the Qingcaosha Reservoir were Gammaproteobacteria, Alphaproteobacteria, Actinomycetes, Acidimicrobiia, and Cyanobacteria. In addition, the Shannon diversity indexes were compared, and the results showed significant temporal differences based on monthly averaged value, although no significant spatial difference. The community structure was found to be mainly influenced by phytoplankton density and biomass, dissolved oxygen, and electrical conductivity. The presence of Pseudomonas and Legionella was positively correlated with that of Pseudanabaena sp., and Sphingomonas and Paragonimus with Melosira granulata. On the contrary, the presence of Planctomycetes was negatively correlated with Melosira granulata, as was Deinococcus-Thermus with Cyclotella sp. The relative abundance of denitrifying bacteria decreased from April to December, while the abundance of nitrogen-fixing bacteria increased. This study provides a scientific basis for understanding the ecological interactions between bacteria, algae, and water quality in reservoir ecosystems.

The nutrient-improvement bacteria selected by Agave lechuguilla T. and their role in the rhizosphere community.

Agave lechuguilla has one of the widest distributions among other agave species in the Chihuahuan Desert. Their capacity to grow in poorly developed soils and harsh conditions has been related to their association with plant growth-promoting rhizobacteria. In this work, we explored how soil properties and plant growth stage influence the composition of the rhizobacterial communities, their interactions, and the enzymatic activity and abundance of nitrogen-fixing bacteria and organic phosphorus-mineralizing bacteria in two subregions of the Chihuahuan Desert. We found that mature plants of lechuguilla stimulated the activity and abundance of nutrient-improvement rhizobacteria, and these soil samples had a higher content of total organic carbon, ammonium (NH4) and nitrite + nitrate (NO2+NO3). Nutrient availability seems to be an essential driver of the bacterial community's structure since the genera with more connections (hubs) were those with known mechanisms related to the availability of nutrients, such as env. OPS17 (Bacteroidetes), Gemmatimonadaceae uncultured, S0134terrestrial group, BD211terrestrial group (Gemmatimonadetes), Chthoniobacteracea and Candidatus Udaeobacter (Verrucomicrobia). This work shows that the late growth stages of lechuguilla recruit beneficial bacteria that favor its establishment and tolerance to harsh conditions of the arid lands.

Coupling Between the Responses of Plants, Soil, and Microorganisms Following Grazing Exclusion in an Overgrazed Grassland.

Grazing exclusion is an effective management practice to restore grassland ecosystem functioning. However, little is known about the role of soil microbial communities in regulating grassland ecosystem functioning during long-term ecosystem restorations. We evaluated the recovery of a degraded semiarid grassland ecosystem in northern China by investigating plant and soil characteristics and the role of soil microbial communities in ecosystem functioning after 22 years of grazing exclusion. Grazing exclusion significantly increased the alpha diversity and changed the community structure of bacteria, but did not significantly affect the alpha diversity or community structure of fungi. The higher abundance of copiotrophic Proteobacteria and Bacteroidetes with grazing exclusion was due to the higher carbon and nutrient concentrations in the soil, whereas the high abundance of Acidobacteria in overgrazed soils was likely an adaptation to the poor environmental conditions. Bacteria of the Sphingomonadaceae family were associated with C cycling under grazing exclusion. Bacteria of the Nitrospiraceae family, and especially of the Nitrospira genus, played an important role in changes to the N cycle under long-term exclusion of grazing. Quantitative PCR further revealed that grazing exclusion significantly increased the abundance of nitrogen fixing bacteria (nifH), ammonia oxidizers (AOA and AOB), and denitrifying bacteria (nirK and nosZ1). Denitrifying enzyme activity (DEA) was positively correlated with abundance of denitrifying bacteria. The increase in DEA under grazing exclusion suggests that the dependence of DEA on the availability of NO3– produced is due to the combined activity of ammonia oxidizers and denitrifiers. Our findings indicate that decades-long grazing exclusion can trigger changes in the soil bacterial diversity and composition, thus modulating the restoration of grassland ecosystem functions, carbon sequestration and soil fertility.

Improvement of nitrogen and phosphorus availability by Pseudoalteromonas sp. during salt-washing in saline-alkali soil

In saline-alkali soils, the inactivation of phosphorus and loss of nitrogen resulting in soil infertility could be intensified by salt, which simultaneously leads to pollution of water sphere. However, there is no complete solution for this challenge due to the weak nutrients biological turnover caused by salt dynamic accumulation. In this study, halophilic marine bacteria strains with carriers were screened to decrease the leaching of nitrogen and phosphorus inactivation in saline-alkali soil during salt-washing. Results showed the combination of Pseudoalteromonas sp. CF8-6 and corn cob significantly increased not only soil available phosphorus by 37.03%, but also the soil bioavailable phosphorus content. Moreover, the concentration of TN, NO3−, TP and PO43− in salt washing eluents reduced by corn cob colonized with CF8-6 significantly. It was also found that the abundance of nitrogen-fixing bacteria (such as Azotobacter), and abundance of Proteobacteria and Actinobacteria in soil were all increased by this combination, which were corresponding for the turnover of nitrogen and phosphorus. We demonstrated that the combination of CF8-6 and corn cob has promising potential in improvement of bioavailability of soil nitrogen and phosphorus during the salt-washing process in saline-alkali soil.

Diversity of soil nitrogen-fixing bacteria in the rhizosphere and non-rhizophere soils of Ebinur Lake Wetland.

Ebinur Lake Wetland is an understudied desert wetland ecosystem, particularly regarding nitrogen cycling. This study aimed to ascertain the diversity and richness of nitrogen-fixing bacterial communities in the Ebinur Lake Wetland. The diversity of the nitrogen-fixing bacteria community of nifH genes from the rhizosphere and non-rhizosphere soils of four plants in different seasons were examined using Illumina HiSeq PE250 high-throughput sequencing technology. The correlation between soil environmental factors and diversity and richness of nitrogen-fixing bacteria was studied using the redundancy analysis (RDA). The results showed that the diversity of nitrogen-fixing bacteria in the rhizosphere soil of the constructive plants was higher than that in the non-rhizosphere soil; also, the diversity in July was higher than that in October and April. Geobacter, Pseudomonas and Bradyrhizobium were the dominant common bacteria in different samples of Ebinur Lake Wetland. The RDA showed that the total nitrogen, available potassium and available phosphoruswere significantly correlated with the diversity and richness of nitrogen-fixing bacteria. The diversity and community structure of nitrogen-fixing bacteria in soil samples also changed over time. The community structures of nitrogen-fixing bacteria in the rhizosphere and non-rhizosphere soils of the four plants were not the same during the same period. The correlation between soil environmental factors and the community structure and abundance of nitrogen-fixing bacteria can provide data basis and theoretical support for the degradation and restoration of Ebinur Lake Wetland.

Does the Returning Farmland to Forest Program improve the ecosystem stability of rhizosphere in winter in alpine regions?

As one of the ecological measures to control soil erosion and land degradation, the Returning Farmland to Forest Program (RFFP) has been implemented about 30 years in China. To date, the effectiveness of the RFFP is debated. Most studies have focused on the changes in landscape patterns at different scales, exploring the forest cover changes. However, few studies revealed the ecological effects especially the ecological stability, even less in alpine areas. Twelve sampling sites in the Huangshui River Basin were selected to test whether the RFFP improved the quality and stability of rhizosphere ecosystems. The sampling sites located in the RFFP zone, natural ecosystems (perennial grassland, perennial forest), and anthropogenic ecosystems (farmland, human activity zone), respectively. The results showed that the RFFP has improved the physicochemical properties of soil and plant, has increased the relevant abundance of nitrogen fixing bacteria and phosphate-solubilizing bacteria, and has high network stability than anthropogenic ecosystems, while still has certain distance with natural ecosystems. The RFFP definitely has positive impacts on improving the stability and diversity of the ecosystems in alpine areas. This study provides references for estimating the implementation effects of the RFFP from the ecological perspective, which could further guide the next round of the RFFP policy.

Soil Quality Indicators Associated With The Application Of Mycorrhizal Fungi In Coffee Plantations

Introduction: This article is the result of the research work “Evaluation of the quality of the soil associated with the use of mycorrhizae in coffee plantations in the Municipality of Sasaima, Cundinamarca” carried out duringthe years 2018 and 2019 at the Universidad Libre.
 Problem: Several investigations report the use of mycorrhizal fungi in plant development, however, there are few studies regarding the relationship between mycorrhizae and soil quality indicators.
 Methodology: Four plots were evaluated, applying: 1) Control; 2) Local native mycorrhizae isolated by the authors; 3) Commercial liquid mycorrhizae; and 4) Commercial solid mycorrhizae. The samples of the rhizosphericsoils were taken and bimonthly monitoring was applied until 5 collection cycles were obtained. The physicochemical parameters, abundance of functional groups of microorganisms, and enzymatic activities ofthe soil were determined and analyzed by means of univariate and multivariate statistical analysis.
 Conclusion: The research hypothesis was validated since the mycorrhizae inoculation significantly increased the values of the soil quality indicators, namely organic carbon (14%), moisture (19%), phosphorus (30%), abundanceof nitrogen-fixing bacteria (5.5%), phosphate-solubilizing bacteria (7.8%), cellulolytic bacteria (9.3%), and phosphate-solubilizing fungi (2.6%). In addition, the local native mycorrhizae that were isolated by theauthors showed greater benefits than those of the commercial mycorrhizae.
 Originality: This research reveals the impact of mycorrhizae on the soil quality indicators over time during thefirst year of application, especially on the microbial and enzymatic parameters.
 Limitations: Several authors have investigated the importance of the mycorrhizae on the physicochemical parameters of the plant, and not on the microbial and enzymatic parameters of the soil.

RETRACTED: Increased abundance of nitrogen fixing bacteria by higher C/N ratio reduces the total losses of N and C in cattle manure and corn stover mix composting

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. The article duplicates significant parts of a paper that had already appeared in Bioresource Technology, Volume 297, February 2020, 122410, https://doi.org/10.1016/j.biortech.2019.122410. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper has not been previously published and is not under consideration for publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a misuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Domestic Wastewater for Forage Cultivation in Cerrado Soil

Fertigation of agricultural crops that are not directly used in human food, with domestic wastewater is a viable alternative for the sustainable use of water resources. The development of agricultural practices that provide high productivity with the sustainability of agroecosystems has been a great challenge. Thus, our aims were to use of domestic wastewater in the planting of Brachiaria brizantha cv Marandu, as an alternative for animal feed production in Cerrado soils, and to study the physical-chemical and microbiological impacts of the fertigation. These impacts were evaluated, respectively, by physical-chemical indicators content and diversity of nitrogen fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) in the DGGE profile. The NPK contents of the wastewater were used to determine the five fertigation managements (M1 to M5). M1 and M2 managements had no wastewater and M3 to M5 contained 20, 40 and 60% of NPK from the wastewater. The managements in a completely randomized design with 20 plots and 4 replicates were distributed. Soil samplings prior to fertigation and at the end of the experiment were performed. Leaf biomass productivity was determined in three different grass cuts. After fertigation, changes in physical-chemical indicators and in the viable microbial cells counts were observed. The NPK of wastewater increased the abundance of NFBs and AMFs. Leaf biomass productivity per hectare was directly proportional to NPK concentration. In addition, wastewater did not alter the nutritional composition of Marandu grass. Therefore, the fertigation with domestic wastewater showed to be a viable and promising alternative for reuse of this water in Cerrado soil for animal feed production.

The Influence of biofertilizer on abundance of Nitrogen Fixing bacteria and growth of Chinchona Plants (Chinchona ledreriana.) Clone Cib. 5

The objective of this research was to eva-luate the effect of biofertilizer on the abundance of nitrogen fixing bacteria and growth of cin-chona plants (Cinchona ledgeriana Moens) clones Cib.5. The research was conducted at the Research Institute for Tea and Cinchona, Gambung, Bandung, from May 2011 until June 2011. A randomized block design was used with five treatments and five replication. Application of five concentration of biofertilizer were per-formed. Concentrations were: 0, 2, 4, 6, and 8 cc/l of water. The results indicated that the application of biofertilizer gave the higher total bacterial population compared to the treatment without biofertilizer, but showed no significant effect on growth of Cinchona plants. Concen-tration of biofertilizer 8 cc/l gave the higher total bacterial population of nitrogen fixing.

The application of amplicon length heterogeneity PCR (LH-PCR) for monitoring the dynamics of soil microbial communities associated with cadaver decomposition

The placement of cadavers in shallow, clandestine graves may alter the microbial and geochemical composition of the underlying and adjacent soils. Using amplicon length heterogeneity-PCR (LH-PCR) the microbial community changes in these soils can be assessed. In this investigation, nine different grave sites were examined over a period of 16weeks. The results indicated that measurable changes occurred in the soil bacterial community during the decomposition process. In this study, amplicons corresponding to anaerobic bacteria, not indigenous to the soil, were shown to produce differences between grave sites and control soils. Among the bacteria linked to these amplicons are those that are most often part of the commensal flora of the intestines, mouth and skin. In addition, over the 16week sampling interval, the level of indicator organisms (i.e., nitrogen fixing bacteria) dropped as the body decomposed and after four weeks of environmental exposure they began to increase again; thus differences in the abundance of nitrogen fixing bacteria were also found to contribute to the variation between controls and grave soils. These results were verified using primers that specifically targeted the nifH gene coding for nitrogenase reductase. LH-PCR provides a fast, robust and reproducible method to measure microbial changes in soil and could be used to determine potential cadaveric contact in a given area. The results obtained with this method could ultimately provide leads to investigators in criminal or missing person scenarios and allow for further analysis using human specific DNA assays to establish the identity of the buried body.