Influence of long‐term land application of Class B biosolids on soil bacterial diversity

Aim: To evaluate the effect of long‐term annual land applications of Class B biosolids on soil bacterial diversity at University of Arizona Marana Agricultural Field Center, Tucson, Arizona. Methods and Results: Following the final of 20 consecutive years of application of Class B biosolids in March 2005, followed by cotton growth from April to November 2005 surface soil samples (0–30 cm) were collected from control (unamended) and biosolid‐amended plots. Total bacterial community DNA was extracted, amplified using 16S rRNA primers, cloned, and sequenced. All 16S rRNA sequences were identified by 16S rRNA sequence analysis and comparison to known sequences in GenBank (NCBI Blast N and Ribosomal Database Project II, RDP). Results showed that the number of known genera (identifiable > 96%) increased in the high rate biosolid plots compared to control plots. Biosolids‐amended soils had a broad phylogenetic diversity comprising more than four major phyla: Proteobacteria (32%), Acidobacteria (21%), Actinobacteria (16%), Firmicutes (7%), and Bacteroidetes (6%) which were typical to bacterial diversity found in the unamended arid southwestern soils. Conclusion: Bacterial diversity was either enhanced or was not negatively impacted following 20 years of land application of Class B biosolids. Significance and Impact of the Study: This study illustrates that long‐term land application of biosolids to arid southwestern desert soils has no deleterious effect on soil microbial diversity.     

Source tracking aerosols released from land-applied class B biosolids during high-wind events

DNA-based microbial source tracking (MST) methods were developed and used to specifically and sensitively track the unintended aerosolization of land-applied, anaerobically digested sewage sludge (biosolids) during high-wind events. Culture and phylogenetic analyses of bulk biosolids provided a basis for the development of three different MST methods. They included (i) culture- and 16S rRNA gene-based identification of Clostridium bifermentans, (ii) direct PCR amplification and sequencing of the 16S rRNA gene for an uncultured bacterium of the class Chloroflexi that is commonly present in anaerobically digested biosolids, and (iii) direct PCR amplification of a 16S rRNA gene of the phylum Euryarchaeota coupled with terminal restriction fragment length polymorphism to distinguish terminal fragments that are unique to biosolid-specific microorganisms. Each method was first validated with a broad group of bulk biosolids and soil samples to confirm the target's exclusive presence in biosolids and absence in soils. Positive responses were observed in 100% of bulk biosolid samples and in less than 11% of the bulk soils tested. Next, a sampling campaign was conducted in which all three methods were applied to aerosol samples taken upwind and downwind of fields that had recently been land applied with biosolids. When average wind speeds were greater than 5 m/s, source tracking results confirmed the presence of biosolids in 56% of the downwind samples versus 3% of the upwind samples. During these high-wind events, the biosolid concentration in downwind aerosols was between 0.1 and 2 microg/m3. The application of DNA-based source tracking to aerosol samples has confirmed that wind is a possible mechanism for the aerosolization and off-site transport of land-applied biosolids.     

The measurement of aerosolized endotoxin from land application of Class B biosolids in Southeast Arizona

The purpose of this study was to determine aerosolized endotoxin concentrations downwind of a biosolids land application site. Aerosol samples were collected from biosolids land application sites, tractor operation, and an aeration basin located within an open-air wastewater treatment plant. Aerosolized endotoxin above background concentrations was detected from all sites, at levels ranging from below detection up to 1800 EU m-3 of air. Biosolids loading operations resulted in the greatest concentrations of endotoxin (mean 344 EU m-3). As downwind (perpendicular to wind vector) distance increased from sources (2-200 m), levels of endotoxin decreased to near background (without biosolids application) concentrations. Overall, the detected levels of aerosolized endotoxin were within past proposed aerosolized endotoxin limits (250-2000 EU m-3) by other occupational exposure studies. Occasionally, peak concentrations were found to be above these limits. Sites in which soil was being aerosolized resulted in greater concentrations of endotoxin with or without biosolids, which suggested that the majority of endotoxin may in fact be of soil origin. This study evaluated the presence of aerosolized endotoxin from the land application of biosolids and showed that these levels were within ranges for concern suggested by other studies and that this area of research needs further investigation.     

Characterisation of the bacterial community associated with early stages of Great Scallop (Pecten maximus), using denaturing gradient gel electrophoresis (DGGE)

Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA was used to characterise and compare bacterial communities associated with scallop larvae (Pecten maximus), in different production units in a shellfish hatchery. Water and larvae samples were collected from three different aquaculture systems; stagnant, flow-through and a flow- through system with seawater treated with ozone. Samples were also collected from different algal cultures, inlet tanks and water pipes leading to the different aquaculture systems. Clear differences were seen between the bacterial community associated with the larvae and in the water from the different aquaculture systems. However, there were high similarities in the community composition between different water samples and between larvae samples collected at different time periods, indicating a high stability in the bacterial communities. Fifty three percent of the sequences from these samples were similar to 16S rRNA gene sequences of members of the gamma-subclass of the Proteobacteria. The different algal cultures had different bacterial communities, however 73 percent of the sequences were similar to 16S rRNA gene sequences of members of the alpha-subclass of the Proteobacteria. Differences in the DGGE profiles were also seen between the samples taken from the inlet tanks and water pipes, indicating a change in the bacterial community composition as the water passed through the pipes. To our knowledge this is the first study investigating bacterial communities associated with Great Scallop larvae in different aquaculture systems including noncultured components.     

Investigation of total bacterial and ammonia-oxidizing bacterial community composition in a full-scale aerated submerged biofilm reactor for drinking water pretreatment in China

The community composition of total bacteria and ammonia-oxidizing bacteria in a full-scale aerated submerged biofilm reactor for drinking water pretreatment was characterized by analysis of 16S rRNA gene and the functional gene amoA, respectively. Sampling was performed in February and in July. 16S rRNA gene clone libraries revealed 13 bacterial divisions. At both sampling dates, the majority of clone sequences were related to the Alpha- and Betaproteobacteria. A minor proportion belonged to the following groups: Gammaproteobacteria, Deltaproteobacteria, Nitrospira, Firmicutes, Acidobacteria, Verrucomicrobia, Actinobacteria, Planctomycetes, Chloroflexi, Gemmatimonadetes and the Cytophaga-Flavobacterium-Bacteroides group. Some sequences related to bacteria owning high potential metabolic capacities were detected in both samples, such as Rhodobacter-like rRNA gene sequences. Surveys of cloned amoA genes from the two biofilm samples revealed ammonia-oxidizing bacterial sequences affiliated with the Nitrosomonas oligotropha lineage, Nitrosomonas communis lineage. An unknown Nitrosomonas group of amoA gene sequences was also detected.     

Bacterial Diversity of the Broadbalk ‘Classical’ Winter Wheat Experiment in Relation to Long-Term Fertilizer Inputs

With more than 160 years of contrasting fertilizer regimes, the Broadbalk winter wheat experiment represents a unique experimental resource for studying the effects of long-term fertilizer application on microbial population diversity. Using DGGE and clone library analysis, we report here on eubacterial species diversity (16S rRNA gene) and diversity within two sets of gene products associated with microbial N acquisition: NifH (nitrogen fixation) and AmtB (ammonium transport). Comparisons were made within and between soils treated with mineral N fertilizer, farmyard manure or receiving no fertilizer. Analysis of 16S rRNA gene DGGE profiles showed no clear patterns to qualitatively distinguish bacterial community structure between the three different treatments (P > 0.05), with all samples containing a range of eubacterial taxa similar to those that are characteristic of soil bacteria reported elsewhere. Intra-plot heterogeneity was high and of a similar magnitude to that between treatments. This lack of qualitative between plot differences was echoed in the representative sequences of 16S rRNA, nifH, and amtB genes in the various samples. Taken together, both phylogenetic and functional gene analyses showed bacterial communities in the Broadbalk-trial soil were very stable and relatively non-responsive to long-term management of balanced fertilizer inputs.     

Assessment of microbial diversity in four southwestern United States soils by 16S rRNA gene terminal restriction fragment analysis

The ability of terminal restriction fragment (T-RFLP or TRF) profiles of 16S rRNA genes to provide useful information about the relative diversity of complex microbial communities was investigated by comparison with other methods. Four soil communities representing two pinyon rhizosphere and two between-tree (interspace) soil environments were compared by analysis of 16S rRNA gene clone libraries and culture collections (Dunbar et al., Appl. Environ. Microbiol. 65:1662-1669, 1998) and by analysis of 16S rDNA TRF profiles of community DNA. The TRF method was able to differentiate the four communities in a manner consistent with previous comparisons of the communities by analysis of 16S rDNA clone libraries. TRF profiles were not useful for calculating and comparing traditional community richness or evenness values among the four soil environments. Statistics calculated from RsaI, HhaI, HaeIII, and MspI profiles of each community were inconsistent, and the combined data were not significantly different between samples. The detection sensitivity of the method was tested. In standard PCRs, a seeded population comprising 0.1 to 1% of the total community could be detected. The combined results demonstrate that TRF analysis is an excellent method for rapidly comparing the relationships between bacterial communities in environmental samples. However, for highly complex communities, the method appears unable to provide classical measures of relative community diversity.     

Use of rpoB and 16S rRNA genes to analyse bacterial diversity of a tropical soil using PCR and DGGE

AIM: To evaluate the rpoB gene as a biomarker for PCR-DGGE microbial analyses using soil DNA from the Cerrado, Brazil. METHODS: DNA extraction from soil was followed by Polymerase Chain Reaction (PCR) amplification of rpoB and 16S rRNA genes. PCR products were compared by Denaturing Gradient Gel Electrophoresis (DGGE) to compare gene/community profiles. RESULTS: The rpoB DGGE profiles comprised fewer bands than the 16S rDNA profiles and were easier to delineate and therefore to analyse. Comparison of the community profiles revealed that the methods were complementary. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The gene for the beta subunit of the RNA polymerase, rpoB, is a single copy gene unlike 16S rDNA. Multiple copies of 16S rRNA genes in bacterial genomes complicate diversity assessments made from DGGE profiles. Using the rpoB gene offers a better alternative to the commonly used 16S rRNA gene for microbial community analyses based on DGGE.     

Bacilli community of saline–alkaline soils from the Ararat Plain (Armenia) assessed by molecular and culture-based methods

The bacterial community composition in the A horizon of a natural saline–alkaline soil located in Ararat Plain (Armenia) was studied using molecular and culture-based methods The sequence analysis of a 16S rRNA gene clone library and denaturing gradient gel electrophoresis (DGGE) profiles indicated dominance of Firmicutes populations. The majority of the sequences of the bacterial 16S rRNA gene library were close relatives of representatives belonging to the genera Halobacillus (41.2%), Piscibacillus (23.5%), Bacillus (23.5%) and Virgibacillus (11.8%). Eight novel moderately halophilic bacilli isolates were successfully obtained from the enriched cultures of the saline–alkaline soil samples. 16S rRNA gene sequence analyses of isolates revealed their affiliation (97.7–99.7% similarity) to representatives of the genera Bacillus, Piscibacillus and Halobacillus. All isolates were able to tolerate high concentrations of NaCl and highly alkaline conditions. This is the first study combining cultivation-independent and -dependent approaches to reveal the bacterial diversity of the saline–alkaline soils of Ararat Plain and it suggested an important role of bacilli as key microbes in biogeochemical cycles of these environments.     

Effect of Freeze-Thaw Cycles on Bacterial Communities of Arctic Tundra Soil

The effect of freeze-thaw (FT) cycles on Arctic tundra soil bacterial community was studied in laboratory microcosms. FT-induced changes to the bacterial community were followed over a 60-day period by terminal restriction fragment length polymorphism (T-RFLP) profiles of amplified 16S rRNA genes and reverse transcribed 16S rRNA. The main phylotypes of the active, RNA-derived bacterial community were identified using clone analysis. Non-metric multidimensional scaling ordination of the T-RFLP profiles indicated some shifts in the bacterial communities after three to five FT cycles at −2, −5, and −10°C as analyzed both from the DNA and rRNA. The dominating T-RFLP peaks remained the same, however, and only slight variation was generally detected in the relative abundance of the main T-RF sizes of either DNA or rRNA. T-RFLP analysis coupled to clone analysis of reverse transcribed 16S rRNA indicated that the initial soil was dominated by members of Bacteroidetes, Acidobacteria, Alpha-, Beta-, and Gammaproteobacteria. The most notable change in the rRNA-derived bacterial community was a decrease in the relative abundance of a Betaproteobacteria-related phylotype after the FT cycles. This phylotype decreased, however, also in the control soil incubated at constant +5°C suggesting that the decrease was not directly related to FT sensitivity. The results indicate that FT caused only minor changes in the bacterial community structure.     

Molecular analysis of bacterial communities associated with the roots of Douglas fir (Pseudotsuga menziesii) colonized by different ectomycorrhizal fungi

We studied the effect of ectomycorrhizal fungi on bacterial communities colonizing roots of Douglas fir (Pseudotsuga menziesii). Mycorrhizal tips were cleaned of soil and separated based on gross morphological characteristics. Sequencing of the internal transcribed spacers of the nuclear rRNA gene cluster indicated that the majority of the tips were colonized by fungi in the Russulaceae, with the genera Russula and Lactarius comprising 70% of the tips. Because coamplification of organellar 16S rRNA genes can interfere with bacterial community analysis of root tips, we developed and tested a new primer pair that permits amplification of bacterial 16S rRNA genes but discriminates more effectively against organellar sequences than commonly used bacterial primer sets. We then used terminal restriction fragment length polymorphism (T-RFLP) and sequence analysis of the 16S rRNA gene to examine differences in bacterial communities associated with the mycorrhizal tips. Cluster analysis of T-RFLP profiles indicated that there were different bacterial communities among the root tips; however, the communities did not seem to be affected by the taxonomic identity of the ectomycorrhizal fungi. Terminal restriction fragment profiling and sequencing of cloned partial 16S rRNA genes indicated that most bacteria on the ectomycorrhizal tips were related to the Alphaproteobacteria and the Bacteroidetes group.     

Spatial distribution of sponge-associated bacteria in the Mediterranean sponge Tethya aurantium

The local distribution of the bacterial community associated with the marine sponge Tethya aurantium Pallas 1766 was studied. Distinct bacterial communities were found to inhabit the endosome and cortex. Clear differences in the associated bacterial populations were demonstrated by denaturing gradient gel electrophoresis (DGGE) and analysis of 16S rRNA gene clone libraries. Specifically associated phylotypes were identified for both regions: a new phylotype of Flexibacteria was recovered only from the sponge cortex, while Synechococcus species were present mainly in the sponge endosome. Light conduction via radiate spicule bundles conceivably facilitates the unusual association of Cyanobacteria with the sponge endosome. Furthermore, a new monophyletic cluster of sponge-derived 16S rRNA gene sequences related to the Betaproteobacteria was identified using analysis of 16S rRNA gene clone libraries. Members of this cluster were specifically associated with both cortex and endosome of T. aurantium.     

Effect of Incubation Conditions on the Enrichment of Pyrene-degrading Bacteria Identified by Stable-isotope Probing in an Aged,PAH-contaminated Soil

To determine whether the diversity of pyrene-degrading bacteria in an aged polycyclic aromatic hydrocarbon-contaminated soil is affected by the addition of inorganic nutrients or by slurrying the soil, various incubation conditions (all including phosphate buffer) were examined by mineralization studies and stable-isotope probing (SIP). The addition of nitrogen to either continuously mixed slurry or static field-wet soil incubations increased the rate and extent of mineralization of [(14)C]pyrene, with the most rapid mineralization observed in slurried, nitrogen-amended soil. Microcosms of slurry and static field-wet soil amended with nitrogen were also examined by SIP with [U-(13)C]pyrene. Recovered (13)C-enriched deoxyribonucleic acid (DNA) was analyzed by denaturing-gradient gel electrophoresis (DGGE) and 16S ribosomal ribonucleic acid (rRNA) gene clone libraries. DGGE profiles of (13)C-enriched DNA fractions from both incubation conditions were similar, suggesting that pyrene-degrading bacterial community diversity may be independent of treatment method. The vast majority (67 of 71) of the partial sequences recovered from clone libraries were greater than or equal to 97% similar to one another, 98% similar to sequences of pyrene-degrading bacteria previously detected by SIP with pyrene in different soil, and only 89% similar to the closest cultivated genus. All of the sequences recovered from the field-wet incubation and most of the sequences recovered from the slurry incubation were in this clade. Of the four sequences from slurry incubations not within this clade, three possessed greater than 99% similarity to the 16S rRNA gene sequences of phylogenetically dissimilar Caulobacter spp.     

High-Density Universal 16S rRNA Microarray Analysis Reveals Broader Diversity than Typical Clone Library When Sampling the Environment

Molecular approaches aimed at detection of a broad-range of prokaryotes in the environment routinely rely on classifying heterogeneous 16S rRNA genes amplified by polymerase chain reaction (PCR) using primers with broad specificity. The general method of sampling and categorizing DNA has been to clone then sequence the PCR products. However, the number of clones required to adequately catalog the majority of taxa in a sample is unwieldy. Alternatively, hybridizing target sequences to a universal 16S rRNA gene microarray may provide a more rapid and comprehensive view of prokaryotic community composition. This study investigated the breadth and accuracy of a microarray in detecting diverse 16S rRNA gene sequence types compared to clone-and-sequencing using three environmental samples: urban aerosol, subsurface soil, and subsurface water. PCR products generated from universal 16S rRNA gene-targeted primers were classified by using either the clone-and-sequence method or by hybridization to a novel high-density microarray of 297,851 probes complementary to 842 prokaryotic subfamilies. The three clone libraries comprised 1391 high-quality sequences. Approximately 8% of the clones could not be placed into a known subfamily and were considered novel. The microarray results confirmed the majority of clone-detected subfamilies and additionally demonstrated greater amplicon diversity extending into phyla not observed by the cloning method. Sequences matching operational taxonomic units within the phyla Nitrospira, Planctomycetes, and TM7, which were uniquely detected by the array, were verified with specific primers and subsequent amplicon sequencing. Subfamily richness detected by the array corresponded well with nonparametric richness predictions extrapolated from clone libraries except in the water community where clone-based richness predictions were greatly exceeded. It was concluded that although the microarray is unreliable in identifying novel prokaryotic taxa, it reveals greater diversity in environmental samples than sequencing a typically sized clone library. Furthermore, the microarray allowed samples to be rapidly evaluated with replication, a significant advantage in studies of microbial ecology.     

Effect of dietary supplementation with a Saccharomyces cerevisiae mannan oligosaccharide on the bacterial community structure of broiler cecal contents

This study investigated the effects of dietary supplementation with a prebiotic mannan oligosaccharide (MOS) on broiler performance, bacterial community structure, and phylogenetic populations of cecal contents. Bird performance data were collected, and cecal samples were extracted from randomly caught poults from each treatment group every 7 days from hatching to the age of 42 days. Weight gain, feed consumption, and feed efficiency ratios did not differ significantly between groups. Automated ribosomal intergenic spacer analysis (ARISA) of the bacterial communities in birds receiving MOS-supplemented diets indicated that dietary supplementation with MOS at either of 2 levels significantly altered the bacterial community structure from that of the control group on all sample days. The phylogenetic identities of bacteria contained within the cecum were determined by constructing a 16S rRNA gene clone library. A total of 594 partial 16S rRNA gene sequences from the cecal contents were analyzed and compared for the three dietary treatments. The dominant bacteria of the cecum belonged to three phyla, Firmicutes, Bacteroidetes, and Proteobacteria; of these, Firmicutes were the most dominant in all treatment groups. Statistical analysis of the bacterial 16S rRNA gene clone libraries showed that the compositions of the clone libraries from broilers receiving MOS-supplemented diets were, in most cases, significantly different from that of the control group. It can be concluded that in this trial MOS supplementation significantly altered the cecal bacterial community structure.     

Phylogenetic analysis of partial bacterial 16S rDNA sequences of tropical grass pasture soil under Acacia tortilis subsp. raddiana in Senegal

We used direct recovery of bacterial 16S rRNA gene sequences to investigate the bacterial diversity under Acacia tortilis subsp. raddiana, a legume tree naturally growing in the dry land part of Senegal (West Africa). Microbial DNA was purified directly from soil samples and subjected to PCR with primers specific for bacterial 16S rRNA gene sequences. 16S rDNA clone libraries were constructed from two soil samples taken at two dates, i.e. June 25th 1999 (dry season) and August 28th 1999 (rainy season) at depths of 0.25-0.50 m and at 3 m distance from the stem. The 16S rDNA of 117 clones was partially sequenced. Phylogenetic analysis of these sequences revealed extensive diversity (100 phylotypes). Comparative sequence analysis of these clones identified members of the Gammaproteobacteria (35% of the phylotypes) as the most important group, followed by the Firmicutes division with 24%. Alphaproteobacteria, Betaproteobacteria, Acidobacteria and Actinobacteria were found to be less represented. Our data suggest that bacterial communities under Acacia tortilis subsp. raddiana might differ according to the season. The relative compositions of the populations is different in both samples: the Acidobacteria are present in a much higher percentage in the dry season than in the rainy season sample while the inverse effect is observed for the members of the other groups. Within the Gammaproteobacteria we found a shift between the dry season and the rainy season from pseudomonads to Acinetobacter and Escherichia related organisms.     

Recovery of novel bacterial diversity from a forested wetland impacted by reject coal

Sulphide mineral mining together with improperly contained sulphur-rich coal represents a significant environmental problem caused by leaching of toxic material. The Savannah River Site's D-area harbours a 22-year-old exposed reject coal pile (RCP) from which acidic, metal rich, saline runoff has impacted an adjacent forested wetland. In order to assess the bacterial community composition of this region, composite sediment samples were collected at three points along a contamination gradient (high, middle and no contamination) and processed for generation of bacterial and archaeal 16S rDNA clone libraries. Little sequence overlap occurred between the contaminated (RCP samples) and unimpacted sites, indicating that the majority of 16S rDNAs retrieved from the former represent organisms selected by the acidic runoff. Archaeal diversity within the RCP samples consisted mainly of sequences related to the genus Thermoplasma and to sequences of a novel type. Bacterial RCP libraries contained 16S rRNA genes related to isolates (Acidiphilium sp., Acidobacterium capsulatum, Ferromicrobium acidophilium and Leptospirillum ferrooxidans) and environmental clones previously retrieved from acidic habitats, including ones phylogenetically associated with organisms capable of sulphur and iron metabolism. These libraries also exhibited particularly novel 16S rDNA types not retrieved from other acid mine drainage habitats, indicating that significant diversity remains to be detected in acid mine drainage-type systems.     

Estimation of bioaerosol risk of infection to residents adjacent to a land applied biosolids site using an empirically derived transport model

AIM: The purpose of this study was to develop an empirically derived transport model, which could be used to predict downwind concentrations of viruses and bacteria during land application of liquid biosolids and subsequently assess microbial risk associated with this practice. METHODS AND RESULTS: To develop the model, coliphage MS-2 and Escherichia coli were aerosolized after addition to water within a biosolids spray application truck, and bioaerosols were collected at discrete downwind distances ranging from 2 to 70 m. Although coliphage were routinely detected, E. coli did not frequently survive aerosolization. Data on aerosolized coliphage was then used to generate a virus transport model. Risks of infection were calculated for various ranges of human virus concentrations that could be found in biosolids. CONCLUSIONS: A conservative estimate at 30.5 m (assumed to be nearest adjacent residences) downwind, resulted in risks of infection of 1 : 100,000, to the more realistic 1 : 10,000,000 per exposure. Conservative annual risks were calculated to be no more than 7 : 100,000 where as a more realistic risk was no greater than 7 : 10,000,000. Overall, the viral risk to residences adjacent to land application sites appears to be low, both for one time and annual probabilities of infection. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated a simple approach towards modelling viral pathogens aerosolized from land applied liquid biosolids, and offers insight into the associated viral risk.     

芒草种植对土壤细菌群落结构和功能的影响

芒草作为第二代能源植物的代表,其生长过程中根际土壤细菌群落的结构与功能尚不清楚.本研究以种植5年的芒草(湘杂芒1号)为研究对象,选取裸地作为对照,采用16S rRNA基因Miseq测序技术研究其细菌群落组成,同时采用PICRUSt功能预测分析其功能.结果表明: 芒草根际细菌由变形菌门、酸杆菌门、放线菌门、绿弯菌门、拟杆菌门和芽单胞菌门等23个门、231个属的细菌组成,表现出群落组成的丰富性.细菌群落分析表明,种植湘杂芒1号改变了根际细菌群落结构,其细菌群落多样性低于裸地对照.PICRUSt功能预测分析表明,湘杂芒1号根际细菌主要涉及氨基酸运输和代谢、细胞壁/细胞膜/膜结构的生物合成、信号转导机制等24个基因功能家族,表现出功能上的丰富性,并有22个基因功能家族预测基因相对丰度高于裸地,表明种植湘杂芒1号提高了根际细菌功能.对氮、磷循环相关基因进行分析表明,种植湘杂芒1号改变了土壤氮、磷代谢能力.