Improving dryland maize productivity and water efficiency with heterotrophic ammonia-oxidizing bacteria via nitrification and cytokinin activity

A two-year field experiment conducted under dryland conditions in semi-humid and drought-prone regions of China aimed to assess the effect of ammonia-oxidizing bacterial on maize water use efficiency and yield.A heterotrophic ammonia-oxidizing bacteria(HAOB)strain S2_8_1 was used.Six treatments were applied:(1)no irrigation+HAOB strain(DI),(2)no irrigation+blank culture medium(DM),(3)no irrigation control(DCK),(4)irrigation+HAOB(WI),(5)irrigation+blank culture medium(WM),and(6)irrigation control(WCK).Results revealed that HAOB treatment increased maize growth,yield,and water use efficiency over controls,regardless of whether the year was wet or dry.This improvement was attributed to the accelerated nitrification in the rhizosphere soil due to HAOB inoculation,which subsequently led to increased levels of leaf cytokinins.Overall,these findings suggest that HAOB inoculation holds promise as a strategy to boost water use efficiency and maize productivity in dryland agriculture.

Effects of Transgenic DREB Soybean Dongnong 50 on the Diversity of Soil Ammonia-oxidizing Bacteria

ObjectiveThe aim was to understand the effects of transgenic DREB soybean on the ammonia-oxidizing bacteria. MethodThe diversity of the cto gene in pot-planted transgenic soybean and near-isogenic non-transgenic soybean under normal water condition and drought stress was analyzed by PCR-DGGE and sequence analysis. ResultRhizosphere community diversity of ammonia-oxidizing bacteria showed no difference between the treatments of transgenic soybean and its non-transgenic isolines, moreover transgenic soybean under normal water condition and drought stress improved the diversity of the ammonia-oxidizing bacteria in the harvest time. The phylogenetic analysis revealed that all the sequences of excised DGGE bands were closely related to members of the genus Nitrosovibrio and Nitrosospira of the β-subclass Proteobacteria. ConclusionTransgenic DREB soybean has no adverse impact on soil ammonia-oxidizing bacteria.

Community analysis of ammonia-oxidizing bacteria in activated sludge of eight wastewater treatment systems

We investigated the communities of ammonia-oxidizing bacteria （AOB） in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction （PCR） followed by terminal restriction fragment length polymorphism （T-RFLP）, cloning, and sequencing of the α-subunit of the ammonia monooxygenase gene （amoA）. The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities. However, there was no remarkable difference among the AOB T- RFLP profiles from different parts of the same system. The T-RFLP fingerprints showed that a full-scale wastewater treatment plant （WWTP） contained a larger number of dominant AOB species than a pilot-scale reactor. The source of influent affected the AOB community, and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater. However, the AOB community structure was little affected by the treatment process in this study. Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp. not to Nitrosospira spp. Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples, while members of Nitrosomonas europaea cluster occurred in some systems.

Impact of acetochlor on ammonia-oxidizing bacteria in microcosm soils

Acetochlor is an increasingly used herbicide on corn in North China. Currently, the effect of acetochlor on soil ammonia-oxidizing bacteria (AOB) communities is not well documented. Here, we studied the diversity and community composition of AOB in soil amended with three concentrations of acetochlor (50, 150, 250 mg/kg) and the control (0 mg acetochlor/kg soil) in a microcosm experiment by PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) and the phylogenetic analysis of excised ...

Characterization of Bacterial Community,Ammonia-Oxidizing Bacteria,and Nitrospira During the Operation of a Commercial-Scale Recirculating Aquaculture System for Culturing Pufferfish Takifugu rubripes

We investigated the changes in communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira during the operation of a pufferfish Takifugu rubripes recirculating aquaculture system by using high-throughput DNA sequencing.Differences in bacterial communities were observed at days 1-32,47-62 and 78-93 of biofilm development by using 16S rRNA gene pyrosequencing.The relative abundance of Proteobacteria(Gammaproteobacteria)increased,while that of Bacteroidetes(Flavobacteria)decreased.The proportions of Nitrosomonas and Nitrospina ranged from 0.02%to 0.30%and from 0.02%to 0.83%,respectively.Ammonia monooxygenase gene pyrosequencing revealed that the top three operational taxonomic units were related to Nitrosomonas aestuarii(17.5%-61.1%),uncultured beta proteobacterium clone B67S-54(1.9%-45.2%),and uncultured bacterium clone AZPa8(3.6%-24.7%).Nitrite oxidoreductase gene pyrosequencing revealed that the relative abundance of the dominant strain Nitrospira sp.Ecomares 2.1 increased,but that of the abundant species Nitrospira marina decreased.Our results demonstrated that the communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira were changing during the operation of the pufferfish recirculating aquaculture system.

Distribution characteristics of ammonia-oxidizing bacteria in the Typha latifolia constructed wetlands using fluorescent in situ hybridization(FISH)

A molecular biology method, fluorescent in situ hybridization（FISH）, in which the pre-treatment was improved in allusion to the media of the constructed wetlands（CW）, e.g. the soil and the grit, was used to investigate the vertical distribution characteristics of ammonia-oxidizing bacteria（AOB） quantity and the relation with oxidation-reduction potential（ORP） in the Typha latifolia constructed wetlands under three different Ioadings in summer from May to September. Results showed that the quantity of the AOB decreased in the Typha latifolia CW with the increase of vertical depth. However, the AOB quantity was 2-4 times the quantity of the control in the root area. Additionally, ORP in the rhizosphere was found to be higher than other areas, which showed that Typha latifolia CW was in an aerobic state in summer when using simulated non-point sewage at the rural area of Taihu Lake in China and small town combined sewage.

Nitrification intensity and ammonia-oxidizing bacteria and archaea in different wetland plant rhizosphere soils

In order to explore the nitrogen removal process in constructed wetlands(CW s),the moisture,ammonia nitrogen(NH4+-N),nitrate nitrogen(NO3"-N)and nitrification intensity in three wetland plant rhizosphere soils(Acorns calamus,Typha orientalis,Iris pseudacorus)were investigated at a relatively normal temperature range of15to25The relative abundance of ammonia-oxidizing bacteria(AOB)and ammonia-oxidizing archaea(AOA)were also achieved using fluorescence in situ hybridization(FISH).It is found that T.orientalis achieves the highest nitrification intensity of2.03m g(h?kg)while the second is I.pseudacorrs(1.74m g/(h?kg)),and followed by A.calamus(1.65m g/(h?kg))throughout the experiment.FISH reveals that the abundance of bacteria(1010g_1wet soil)is higher than that of archaea(109g_1wet soil),and AOBare the dominant bacteria in the ammonia oxidation process.The abundance of AOB in te rhizosphere soils from high to low T.orientalis(1.88x1010g"1),I pseudacorus(1.23x1010g1),A.calamus(5.07x109g"1)while the abundance of AOA from high to low ae I.pseudacorus(4.00x109g1),A.calamus(3.52x109g"1),T.orientalis(3.48x109g"1).The study provides valuable evidence of plant selection for nitrogen removal in CWs.

Variation of Potential Nitrification and Ammonia-Oxidizing Bacterial Community with Plant-Growing Period in Apple Orchard Soil

In this study, we investigated the potential nitrification and community structure of soil-based ammonia-oxidizing bacteria （AOB） in apple orchard soil during different growth periods and explored the effects of environmental factors on nitrification activity and AOB community composition in the soil of a Hanfu apple orchard, using a culture-dependent technique and denaturing gradient gel electrophoresis （DGGE）. We observed that nitrification activity and AOB abundance were the highest in November, lower in May, and the lowest in July. The results of statistical analysis indicated that total nitrogen （N） content, NH4＋-N content, NO3-N content, and pH showed significant correlations with AOB abundance and nitrification activity in soil. The Shannon-Winner diversity, as well as species richness and evenness indices （determined by PCR-DGGE banding patterns） in soil samples were the highest in September, but the lowest in July, when compared to additional sampled dates. The DGGE fingerprints of soil-based 16S rRNA genes in November were apparently distinct from those observed in May, July, and September, possessing the lowest species richness indices and the highest dominance indices among all four growth periods. Fourteen DGGE bands were excised for sequencing. The resulting analysis indicated that all AOB communities belonged to the 13-Proteobacteria phylum, with the dominant AOB showing high similarity to the Nitrosospira genus. Therefore, soil-based environmental factors, such as pH variation and content of NHa＋-N and NO3--N, can substantially influence the abundance of AOB communities in soil, and play a critical role in soil-based nitrification kinetics.

Isolation and characterization of facultative mixotrophic ammonia-oxidizing bacteria from constructed wetlands

Autotrophic ammonia-oxidizing bacteria （AOB） have been widely studied in constructed wetlands systems, while mixotrophic AOB have been less thoroughly examined. Heterotrophic bacteria were isolated from wastewater and rhizospheres of macrophytes of constructed wetlands, and then cultivated in a mixotrophic medium containing ammonium and acetic acid. A molecular characterization was accomplished using ITS-PCR amplification, and phylogenetic analysis based on 16S rRNA gene Sequences. Results showed the presence of 35 bacteria, among 400 initially heterotrophic isolates, that were able to remove ammonia. These 35 isolates were classified into 10 genetically different groups based on ITS pattern. Then, a collection of 10 isolates were selected because of their relatively high ammonia removal efficiencies （ARE≥ 80%） and their phylogenetic diversity. In conditions of mixotrophy, these strains were shown to be able to grow （increase of optical density OD660 during incubation with assimilation of nitrogen into cellular biomass） and to oxidize ammonia （important ammonia oxidation efficiencies, AOE between 79% and 87%）. Among these facultative mixotrophic AOB, four isolates were genetically related to Firmicutes （Bacillus and Exiguobacterium）, three isolates were affiliated to Actinobacteria （Arthrobacter） and three other isolates were associated with Proteobacteria （Pseudomonas, Ochrobactrum and Bordetella）.

Functional relationship between ammonia-oxidizing bacteria and ammonia-oxidizing archaea populations in the secondary treatment system of a full-scale municipal wastewater treatment plant

The abundance of ammonia-oxidizing bacteria and archaea and their amo A genes from the aerobic activated sludge tanks,recycled sludge and anaerobic digesters of a full-scale wastewater treatment plant(WWTP)was determined.Polymerase chain reaction and denaturing gradient gel electrophoresis were used to generate diversity profiles,which showed that each population had a consistent profile although the abundance of individual members varied.In the aerobic tanks,the ammonia-oxidizing bacterial(AOB)population was more than 350 times more abundant than the ammonia-oxidizing archaeal(AOA)population,however in the digesters,the AOA population was more than 10 times more abundant.Measuring the activity of the amo A gene expression of the two populations using RT-PCR also showed that the AOA amo A gene was more active in the digesters than in the activated sludge tanks.Using batch reactors and dd PCR,amo A activity could be measured and it was found that when the AOB amo A activity was inhibited in the anoxic reactors,the expression of the AOA amo A gene increased fourfold.This suggests that these two populations may have a cooperative relationship for the oxidation of ammonia.

Active ammonia-oxidizing bacteria and archaea in wastewater treatment systems

Ammonia-oxidizing bacteria(AOB)and archaea(AOA)are two microbial groups mediating nitrification,yet little is presently known about their abundances and community structures at the transcriptional level in wastewater treatment systems(WWTSs).This is a significant issue,as the numerical abundance of AOA or AOB at the gene level may not necessarily represent their functional role in ammonia oxidation.Using amo A genes as molecular markers,this study investigated the transcriptional abundance and community structure of active AOA and AOB in 14 WWTSs.Quantitative PCR results indicated that the transcriptional abundances of AOB amo A(averaged:1.6×10^(8)copies g^(-1)dry sludge)were higher than those of AOA(averaged:3.4×10^(7)copies g^(-1)dry sludge)in all WWTSs despite several higher abundances of AOA amo A at the gene level.Moreover,phylogenetic analysis demonstrated that Nitrosomonas europaea and unknown clusters accounted for 37.66%and 49.96%of the total AOB amo A transcripts,respectively,suggesting their dominant role in driving ammonia oxidation.Meanwhile,AOA amo A transcripts were only successfully retrieved from 3 samples,and the Nitrosospaera sister cluster dominated,accounting for 83.46%.Finally,the substrate utilization kinetics of different AOA and AOB species might play a fundamental role in shaping their niche differentiation,community composition,and functional activity.This study provides a basis for evaluating the relative contributions of ammonia-oxidizing microorganisms(AOMs)to nitrogen conversions in WWTSs.

Abundance and composition of ammonia-oxidizing bacteria and archaea in different types of soil in the Yangtze River estuary

Tidal flats are soil resources of great significance.Nitrification plays a central role in the nitrogen cycle and is often a critical first step in nitrogen removal from estuarine and coastal environments.We determined the abundance as well as composition of ammonia-oxidizing bacteria(AOB) and ammonia-oxidizing archaea(AOA) in different soils during land reclamation process.The abundance of AOA was higher than that of AOB in farm land and wild land while AOA was not detected in tidal flats using real-time polymerase chain reaction(PCR).The different abundances of AOB and AOA were negatively correlated with the salinity.The diversities of AOB and AOA were also investigated using clone libraries by amplification of amoA gene.Among AOB,nearly all sequences belonged to the Nitrosomonas lineage in the initial land reclamation process,i.e.,tidal flats,while both Nitrosomonas and Nitrosospira lineages were detected in later and transition phases of land reclamation process,farm land and wild land.The ratio of the numbers of sequences of Nitrosomonas and Nitrosospira lineages was positively correlated with the salinity and the net nitrification rate.As for AOA,there was no obvious correlation with the changes in the physicochemical properties of the soil.This study suggests that AOB may be more import than AOA with respect to influencing the different land reclamation process stages.

Distribution of ammonia-oxidizing Betaproteobacteria community in surface sediment off the Changjiang River Estuary in summer

The spatial distribution of ammonia-oxidizing Betaproteobacteria （βAOB） was investigated by FISH （fluorescence in situ hybridization） and DGGE （denaturing gradient get electrophoresis） techniques in the sediment off the Changjiang River Estuary. Sediment samples were collected from eight stations in June before the formation of hypoxia zone in 2006. The abundance of βAOB ranged from 1.87× 10^5 to 3.53×10^5 cells/g of sediment. βAOB abundance did not present a negative correlation with salinity, whereas salinity was implicated as the primary factor affecting nitrification rates. The DGGE profiles of PCR-amplified amoA gene fragments revealed that the βAOB community structure of sample S2 separated from other samples at the level of 40% similarity. The variations in composition ofβAOB were significantly correlated with the salinity, temperature, absorption ability of sediments and TOC. The statistical analysis indicates that theβAOB abundance was a main factor to influence nitrification rates with an influence ratio of 87.7% at the level of 40% biodiversity similarity. Considering the good correlation between βAOB abundance and nitrification estimates, the abundance and diversity of βAOB community could be expected as an indirect index of nitrification activity at the study sea area in summer.

Insight into the spoilage heterogeneity of meat-borne bacteria isolates with high-producing collagenase

Chilled chicken is inevitably contaminated by microorganisms during slaughtering and processing,resulting in spoilage.Cutting parts of chilled chicken,especially wings,feet,and other skin-on products,are abundant in collagen,which may be the primary target for degradation by spoilage microorganisms.In this work,a total of 17 isolates of spoilage bacteria that could secrete both collagenase and lipase were determined by raw-chicken juice agar(RJA)method,and the results showed that 7 strains of Serratia,Aeromonas,and Pseudomonas could significantly decompose the collagen ingredients.The gelatin zymography showed that Serratia liquefaciens(F5)and(G7)had apparent degradation bands around 50 kDa,and Aeromonas veronii(G8)and Aeromonas salmonicida(H8)had a band around.65 and 95 kDa,respectively.The lipase and collagenase activities were detected isolate-by-isolate,with F5 showing the highest collagenase activity.For spoilage ability on meat in situ,F5 performed strongest in spoilage ability,indicated by the total viable counts,total volatile basic nitrogen content,sensory scores,lipase,and collagenase activity.This study provides a theoretical basis for spoilage heterogeneity of strains with high-producing collagenase in meat.

Response of ammonia-oxidizing betaproteobacteria to short- term fertilization in a salt marsh in China

This study examines the impacts of short-term(6 months) fertilization on the community structure and abundance of ammonia-oxidizing betaproteobacteria(β-AOB) and the potential nitrification rate in sediment colonized by S uaeda heteroptera in a saltmarsh located in Shuangtai estuary, China. The sediment samples were collected from plots treated with different amounts of an N fertilizer(urea supplied at 0.1, 0.2, 0.4, and 0.8 g/kg(nitrogen content in dry sediment)), and with different forms of N fertilizers(urea,(NH4) 2 SO 4, and NH_4NO_3, each supplied at 0.2 g/kg). The fertilizers were applied 1–4 times during the plant-growing season in May, July, August and September of 2013. Untreated plots were included as a control. As revealed in denaturing gradient gel electrophoresis of the 16 S r RNA gene, the β-AOB community responded to both the amount and form of N. Real-time quantitative PCR indicated that both abundance and potential nitrification rate of β-AOB increased after N addition, regardless of concentration and form(except NH_4NO_3). These results provide evidence that short-term N application influences the sediment β-AOB community, β-AOB abundance and potential nitrification rate in a saltmarsh ecosystem.

The impact of ultrasonic treatment on activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in activated sludge

The ultrasonic treatment of sludge has been considered as an effective method to facilitate the partial nitritation of municipal sewage.This study aims to reveal the effects of ultrasound on ammoniaoxidizing bacteria(AOB)and nitrite-oxidizing bacteria(NOB).The impact factors including ultrasonic irradiation time and intensity,sludge concentration,thermal effect and released free radicals were studied.The maximized difference between the changes in AOB and NOB activities were obtained with 10 g mixed liquor suspended solids(MLSS)/L,using 0.9 kJ/mL ultrasonic energy density and 12 h interval time.The increased ultrasonic intensity destroyed the floc structure of activated sludge,increased the microbial death,and decreased the cellular ATP level.Further,the mechanism exploration indicated that the mechanical shearing could be a critical factor in achieving the nitritation with inhibitory effect on nitrite oxidation.

Modern approaches for detection of volatile organic compounds in metabolic studies focusing on pathogenic bacteria:Current state of the art

Pathogenic microorganisms produce numerous metabolites,including volatile organic compounds(VOCs).Monitoring these metabolites in biological matrices(e.g.,urine,blood,or breath)can reveal the presence of specific microorganisms,enabling the early diagnosis of infections and the timely implementation of tar-geted therapy.However,complex matrices only contain trace levels of VOCs,and their constituent com-ponents can hinder determination of these compounds.Therefore,modern analytical techniques enabling the non-invasive identification and precise quantification of microbial VOCs are needed.In this paper,we discuss bacterial VOC analysis under in vitro conditions,in animal models and disease diagnosis in humans,including techniques for offline and online analysis in clinical settings.We also consider the advantages and limitations of novel microextraction techniques used to prepare biological samples for VOC analysis,in addition to reviewing current clinical studies on bacterial volatilomes that address inter-species in-teractions,the kinetics of VOC metabolism,and species-and drug-resistance specificity.

Antiseptic Efficacy of A Soap Made from Biosurfactants Isolated from Bacillus and Lactobacillus against Pathogenic Bacteria

The aim of our study was to use a biosurfactant produced by Bacillus and Lactobacillus isolates as an antiseptic in the formulation of local soap. A total of 60 isolates were characterized by microbiological techniques (30 Bacillus and 30 Lactobacillus) and the ability to produce biosurfactants was demonstrated by a hydrocarbon emulsification index (E24). The emulsification indexes (E24) varied from 9% to 100% for Bacillus and from 33% to 100% for Lactobacillus as well. The antagonistic assay showed that biosurfactants were able to inhibit the formation of biofilms and growth of pathogens such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Salmonella typhirium, Shigella boydii and Proteus mirabilis. The biosurfactant consortium (BioC) from Bacillus consortium and from Lactobacillus was able to inhibit biofilm formation and the pathogens growth. The BioC was stable to alkaline pH and the temperatures stability of Biosurfactant was ranging from 50°C to 90°C. The soap was made by the cold saponification process using one biosurfactant consortium formulated. This soap has a pH of 10 and showed good cleaning power and good foam stability. Similarly, the soap showed good antiseptic power and disinfection power against all pathogens tested. Handwashing is critical to preventing disease transmission. The persistence of pathogens in waste water was evaluated. The BioS produced showed good disinfection power against all pathogens tested. The valor of reduction on the hands and in the waste water was significantly more than compared to the control soaps used. This soap could be used in the prevention, fighting, and treatment of bacterial and viral infections.

The Preliminary Study on Screening and Application of Phthalic Acid-Degrading Bacteria

Phthalic acid is a main pollutant, which is also an important reason for the continuous cropping effect of tobacco. In order to degrade the phthalic acid accumulated in the environment and relieve the obstacle effect of tobacco continuous cropping caused by the accumulation of phthalic acid in the soil. In this study, phthalate degrading bacteria B3 is screened from continuous cropping tobacco soil. The results of biochemical identification and 16sDNA comparison show that the homology between degrading bacterium B3 and Enterobacter sp. is 99%. At the same time, the growth of Enterobacter hormaechei subsp. B3 and the degradation of phthalic acid under different environmental conditions are studied. The results show that the environment with a temperature of 30˚C, PH of 7, and inoculation amount of not less than 1.2%, which is the optimal growth conditions for Enterobacter sp. B3. In an environment with a concentration of phthalic acid not exceeding 500 mg/L, Enterobacter sp. B3 has a better effect on phthalic acid degradation, and the degradation rate can reach 77% in 7 d. The results of indoor potting experiments on tobacco show that the degradation rate of phthalic acid by Enterobacter B3 in the soil is about 45%, which can reduce the inhibitory effect of phthalic acid on the growth of tobacco seedlings. This study enriches the microbial resources for degrading phthalic acid and provides a theoretical basis for alleviating tobacco continuous cropping obstacles.

Nature’s Pharmacy under Siege: Investigating Antibiotic Resistance Pattern in Endophytic Bacteria of Medicinal Plants

Antibiotic resistance poses a significant global health threat, necessitating a thorough understanding of its prevalence in various ecological contexts. Medicinal plants, renowned for their therapeutic properties, host endophytic bacteria that produce bioactive compounds. Understanding antibiotic resistance dynamics in these bacteria is vital for human health and antibiotic efficacy preservation. In this study, we investigated antibiotic resistance profiles in endophytic bacteria from five medicinal plants: Thankuni, Neem, Aparajita, Joba, and Snake plant. We isolated and characterized 113 endophytic bacteria, with varying resistance patterns observed against multiple antibiotics. Notably, 53 strains were multidrug-resistant (MDR), with 14 exhibiting extensive drug resistance (XDR). Thankuni-associated bacteria displayed 44% MDR and 11% XDR, while Neem-associated bacteria showed higher resistance (60% MDR, 13% XDR). Aparajita-associated bacteria had lower resistance (22% MDR, 6% XDR), whereas Joba-associated bacteria exhibited substantial resistance (54% MDR, 14% XDR). Snake plant-associated bacteria showed 7% MDR and 4% XDR. Genus-specific distribution revealed Bacillus (47%), Staphylococcus (21%), and Klebsiella (11%) as major contributors to MDR. Our findings highlight diverse drug resistance patterns among plant-associated bacteria and underscore the complexity of antibiotic resistance dynamics in diverse plant environments. Identification of XDR strains emphasizes the severity of the antibiotic resistance problem, warranting further investigation into contributing factors.