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Glioblastoma (GBM), the most common malignant primary brain cancer in adults, nearly always becomes resistant to current treatments, including the chemotherapeutic temozolomide (TMZ). The long noncoding RNA (lncRNA) TMZ-associated lncRNA in GBM recurrence (lnc-TALC) promotes GBM resistance to TMZ. Exosomes can release biochemical cargo into the tumor microenvironment (TME) or transfer their contents, including lncRNAs, to other cells as a form of intercellular communication. In this study, we found that lnc-TALC could be incorporated into exosomes and transmitted to tumor-associated macrophages (TAM) and could promote M2 polarization of the microglia. This M2 polarization correlated with secretion of the complement components C5/C5a, which occurred downstream of lnc-TALC binding to ENO1 to promote the phosphorylation of p38 MAPK. In addition, C5 promoted the repair of TMZ-induced DNA damage, leading to chemotherapy resistance, and C5a-targeted immunotherapy showed improved efficacy that limited lnc-TALC–mediated TMZ resistance. Our results reveal that exosome-transmitted lnc-TALC could remodel the GBM microenvironment and reduce tumor sensitivity to TMZ chemotherapy, indicating that the lnc-TALC–mediated cross-talk between GBM cells and microglia could attenuate chemotherapy efficacy and pointing to potential combination therapy strategies to overcome TMZ resistance in GBM.See related Spotlight by Zhao and Xie, p. 1372.

Glioblastoma (GBM), the most common malignant primary brain cancer in adults, nearly always becomes resistant to current treatments, including the chemotherapeutic temozolomide (TMZ). The long noncoding RNA (lncRNA) TMZ-associated lncRNA in GBM recurrence (lnc-TALC) promotes GBM resistance to TMZ. Exosomes can release biochemical cargo into the tumor microenvironment (TME) or transfer their contents, including lncRNAs, to other cells as a form of intercellular communication. In this study, we found that lnc-TALC could be incorporated into exosomes and transmitted to tumor-associated macrophages (TAM) and could promote M2 polarization of the microglia. This M2 polarization correlated with secretion of the complement components C5/C5a, which occurred downstream of lnc-TALC binding to ENO1 to promote the phosphorylation of p38 MAPK. In addition, C5 promoted the repair of TMZ-induced DNA damage, leading to chemotherapy resistance, and C5a-targeted immunotherapy showed improved efficacy that limited lnc-TALC–mediated TMZ resistance. Our results reveal that exosome-transmitted lnc-TALC could remodel the GBM microenvironment and reduce tumor sensitivity to TMZ chemotherapy, indicating that the lnc-TALC–mediated cross-talk between GBM cells and microglia could attenuate chemotherapy efficacy and pointing to potential combination therapy strategies to overcome TMZ resistance in GBM. See related Spotlight by Zhao and Xie, p. 1372.

Two novel species of the genus Deinococcus, designated SYSU M49105T and SYSU M42101T, were isolated from freshwater samples of the Pearl River estuary in Guangdong, China. Phylogenetic analysis using 16S rRNA gene sequence indicated that strains SYSU M49105T and SYSU M42101T showed the highest sequence similarities to Deinococcus aetherius JCM 11751 T (93.6%) and Deinococcus multiflagellatus NBRC 112888 T (97.3%), respectively. Cells of both strains were Gram-staining positive, aerobic, coccus-shaped, oxidase-negative and non-motile. The cell wall contained meso-diaminopimelic acid as their diagnostic diamino acid. MK-8 was the predominant respiratory quinone for both strains. The polar lipid profile of SYSU M49105T contained two unidentified phosphoglycolipids, nine unidentified glycolipids, and five unidentified polar lipids. SYSU M42101T had one unidentified phosphoglycolipid, nine unidentified glycolipids, one unidentified aminophospholipid and four unidentified polar lipids. The major fatty acids of strains SYSU M49105T and SYSU M42101T were summed feature 3 (C16:1 ω7c and/ or C16:1 ω6c) and C16:0. The G + C contents of the novel isolates based on genomic DNAs were 69.6% and 67.4%, respectively. On the basis of phenotypic, genotypic and phylogenetic data, strains SYSU M49105T and SYSU M42101T should be considered to represent two novel species in the genus Deinococcus, for which the names Deinococcus aestuarii sp. nov. and Deinococcus aquaedulcis sp. nov. were proposed with the type strains SYSU M49105T (= KCTC 43258 T = CGMCC 1.18609 T) and SYSU M42101T (= KCTC 43257 T = CGMCC 1.18614 T), respectively.

Anthropogenic nitrogen (N) input is known to alter plant and microbial α-diversity, but how N enrichment influences β-diversity of plant and microbial communities remains poorly understood. Using a long-term multilevel N addition experiment in a temperate steppe, we show that plant, soil bacterial and fungal communities exhibited different responses in their β-diversity to N input. Plant β-diversity decreased linearly as N addition increased, as a result of increased directional environmental filtering, where soil environmental properties largely explained variation in plant β-diversity. Soil bacterial β-diversity first increased then decreased with increasing N input, which was best explained by corresponding changes in soil environmental heterogeneity. Soil fungal β-diversity, however, remained largely unchanged across the N gradient, with plant β-diversity, soil environmental properties, and heterogeneity together explaining an insignificant fraction of variation in fungal β-diversity, reflecting the importance of stochastic community assembly. Our study demonstrates the divergent effect of N enrichment on the assembly of plant, soil bacterial and fungal communities, emphasizing the need to examine closely associated fundamental components (i.e., plants and microorganisms) of ecosystems to gain a more complete understanding of ecological consequences of anthropogenic N enrichment.

Microplastics are a highly concerning pollutant that have gained attention from the scientific community and other regulatory authorities due to their potential risks to organisms and ecosystems. Microplastics are widespread in both terrestrial and aquatic ecosystems and can be found even in Antarctica and deep-sea sediments. The ability to survive for long periods in the environment and their aptitude of inter- and intra-environmental translocation can prompt poor environmental outcomes. The adsorption of heavy metals and other toxic persistent organic pollutants is a further cause for concern. Furthermore, microplastics enable the development of a distinct microbial niche within an ecosystem, which could potentially impair ecosystem function by promoting the growth of selective microbial communities. The acquisition of metal-resistant, antibiotic-resistant genes, and the enrichment of antibiotic-resistant bacteria on microplastic surfaces have recently been reported. Moreover, some studies have also reported the colonization of pathogenic bacterial strains such as Vibrio spp. on microplastic surfaces. This review aims to address the sources of microplastic pollution in the freshwater and marine environments and to discuss their potential functions in the environment.

Microbes, similar to plants and animals, exhibit biogeographic patterns. However, in contrast with the considerable knowledge on the island biogeography of higher organisms, we know little about the distribution of microorganisms within and among islands. Here, we explored insular soil bacterial and fungal biogeography and underlying mechanisms, using soil microbiota from a group of land-bridge islands as a model system. Similar to island species-area relationships observed for many macroorganisms, both island-scale bacterial and fungal diversity increased with island area; neither diversity, however, was affected by island isolation. By contrast, bacterial and fungal communities exhibited strikingly different assembly patterns within islands. The loss of bacterial diversity on smaller islands was driven primarily by the systematic decline of diversity within samples, whereas the loss of fungal diversity on smaller islands was driven primarily by the homogenization of community composition among samples. Lower soil moisture limited within-sample bacterial diversity, whereas smaller spatial distances among samples restricted among-sample fungal diversity, on smaller islands. These results indicate that among-island differences in habitat quality generate the bacterial island species-area relationship, whereas within-island dispersal limitation generates the fungal island species-area relationship. Together, our study suggests that different mechanisms underlie similar island biogeography patterns of soil bacteria and fungi.

Microbes are widespread in the sea that covers more than two-thirds of the earth's surface and most microorganisms living in the marine environment have yet to be cultured. Previous studies showed that drying treatment, a strategy of sample pre-treatment widely applied in microbial isolation and incubation, may alter the cultivable microbial diversity, such as Actinomycetota, essential for exploring novel secondary metabolites from the marine environment, isolated from drying-treated samples. However, whether drying treatments actually can change microbial community diversity and how the drying treatments of samples influence the cultivable microbial diversity of marine samples have not yet adequately been evaluated. Here, three marine sediment samples were dried and incubated at 28 ºC, 37 ºC, and 45 ºC, and the microbial diversity was assessed with high-throughput sequencing. Our results suggested that drying treatments had different effects on different genera and some potential novel species could be cultured only from drying-treated samples, including the novel members from the families Paenibacillaceae and Thermoactinomycetaceae. Non-metric multidimensional scaling analysis showed that the treated samples were clustered according to the cultivation temperatures rather than the drying conditions at high cultivation temperatures. However, at the cultivation temperatures of 28 ºC, drying treatments were the larger separation between cultivable microbial communities in the process of microbial isolation. These results showed that the drying treatments influenced the cultivated microbes in a taxon-specific pattern and extended potential novel taxa. Combining high-throughput sequencing to various drying conditions and incubation temperatures, this study provides new insight into the effects of drying treatment on the cultivable microbial diversity of marine sediments.

Microbes (e.g., bacteria and archaea) are indispensable components for the key biological processes of estuarine ecosystems and three main habitats (sediment, particle, and water) are harboring diverse estuarine microbes. However, we still know little about how the microbial community structures, potential keystone species, and network properties change among these three habitats in estuarine ecosystems. In this study, we collected size-fractioned water and sediment samples from the Pearl River Estuary to reveal their microbial diversity, community structures, network properties, and potential keystone taxa. We found that the sediment microbial community was remarkably more diverse than particle-attached (PA) and free-living (FL) communities, whereas its ecological network was less complex in terms of node distance and connectivity. TOC was determined as the main driver of sediment community, while the PA and FL communities were predominantly shaped by NO

Terahertz communication technology has attracted wide attention from academic circles and industry, and is regarded as the key wireless technology to meet the real-time traffic demand of mobile heterogeneous network system, which can alleviate the capacity bottleneck of the current wireless system and realize ultra-high-speed wireless communication. As a key content of Beam-forming Techniques, indoor channel modeling of terahertz band in NLOS (non-line-of-sight) has become an urgent task. In this paper, according to the position of the receiver and the surrounding scenes, the possible path from the transmitter to the receiver is traced back through geometric optics. The influence of diffraction on the transmission channel of 300GHz indoor communication system is evaluated. Ray tracing technology is combined with knife edge diffraction (KED) and double knife edge (DKE) to simulate the diffraction of wedge-shaped object and human body respectively. The results show that when the wedge-shaped object diffracts, the diffraction coefficient decreases with the increase of the diffraction angle. Diffraction in the wedge area can be ignored in most areas of the room's line of sight, but diffraction power is dominant in the incident boundary and reflection boundary area. Due to the shadow effect caused by human movement, the path attenuation increases significantly. The results provide a research basis for the development of indoor terahertz communication.

Terahertz (THz) communication is a research hotspot in the future communication field. However, limited by the power of the THz source and various particles in the air, indoor THz wireless communication with short distance transmission has practical research value. Due to the strong directivity of THz beam, the line of sight (LOS) path occupies most of the energy of the signal. However, when the LOS path is blocked, the not line of sight (NLOS) path can be used as a supplement to ensure the stability of the communication link. In this paper, a 3D transmission model combining LOS path, primary reflection path and secondary reflection path was established by ray tracing method for indoor laboratory scenes with high demand for communication rate. The carrier frequency range is 220-330GHz. Through the results of power delay profile (PDP) and power angle profile (PAP) at the receiver, the correlation characteristics of important channel parameters such as Rician K-factor, root mean square (RMS) delay spread with different frequency points and different paths are analyzed. The results show that all the channel parameters are strongly correlated with frequency and transmission distance. These theoretical results lay a foundation for the subsequent communication experiments in real experimental condition.

A novel actinobacterium, designated strain SYSU M44304T, was isolated from freshwater samples in the Pearl River Estuary. The isolate was Gram-stain-positive, aerobic, coccus-shaped, oxidase-positive and motile. The cell wall contained meso-diaminopimelic acid as its diagnostic diamino acid. The predominant menaquinone was MK-8. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine and seven unidentified phospholipids. The major fatty acids were C16 : 0 and C16 : 1. The G+C content based on genomic DNA was 73.2 mol %. The nearest phylogenetic neighbours to the novel strain were Mobilicoccus pelagius NBRC 104925T and Mobilicoccus caccae YIM 101593T. On the basis of chemotaxonomic and physiological characteristics and phylogenetic analysis, strain SYSU M44304T should be considered to represent a novel species of a new genus in the family Dermatophilaceae , for which we propose the name Agilicoccus flavus gen. nov., sp. nov. The type strain of Agilicoccus flavus is SYSU M44304T (=NBRC 114808T=CGMCC 1.18608T).

The fate and removal of ciprofloxacin, a class of fluoroquinolone antibiotic, during sulfur-mediated biological wastewater treatment has been recently well documented. However, little is known regarding the genetic response of microorganisms to ciprofloxacin. Here, a lab-scale anaerobic sulfate-reducing bioreactor was continuously operated over a long term for ciprofloxacin-contaminated wastewater treatment to investigate the response of the microorganisms to ciprofloxacin by adopting a metagenomics approach. It was found that total organic carbon (TOC) removal and sulfate reduction were promoted by approximately 10% under ciprofloxacin stress, along with the enrichment of functional genera (e.g., Desulfobacter, Geobacter) involved in carbon and sulfur metabolism. The metagenomic analytical results demonstrated that ciprofloxacin triggered the microbial SOS response, as demonstrated by the up-regulation of the multidrug efflux pump genes (8-125-fold higher than that of the control) and ciprofloxacin-degrading genes (4-33-fold higher than that of the control). Moreover, the contents of ATP, NADH, and cytochrome C, as well as related functional genes (including genes involved in energy generation, electron transport, carbon metabolism, and sulfur metabolism) were markedly increased under ciprofloxacin stress. This demonstrated that the carbon and sulfur metabolisms were enhanced for energy (ATP) generation and electron transport in response to ciprofloxacin-induced stress. Interestingly, the microbes tended to cooperate while being subjected exposure to exogenous ciprofloxacin according to the reconstructed metabolic network using the NetSeed model. Particularly, the species with higher complementarity indices played more pivotal roles in strengthening microbial metabolism and the SOS response under long-term ciprofloxacin stress. This study characterized the response mechanisms of microorganisms to ciprofloxacin at the genetic level in sulfur-mediated biological wastewater treatment. These new understandings will contribute the scientific basis for improving and optimizing the sulfur-mediated bioprocess for antibiotics-laden wastewater treatment.

This paper presents a fusion of optical fiber transmission with terahertz wireless communication system scheme. One of a pair of SFP optical module is used to process the digital signal generated by AWG (arbitrary waveform generator), which is transmitted by optical fiber for long distance. Another SFP optical module completes the photoelectric conversion of the signal and inputs the signal to the terahertz frequency conversion module for wireless transmission. The code rate is 1.25 Gbps, the carrier frequency is 300 GHz and the modulation mode is QPSK. The results were observed through the eye diagram of the signal received by the oscilloscope. The quality of the eye diagram is well, which indicates that the terahertz over fiber wireless communication has practical significance for indoor high-speed access and other application scenarios.

Anthropogenic environmental changes are known to affect the Earth's ecosystems. However, how these changes influence assembly trajectories of the impacted communities remains a largely open question. In this study, we investigated the effect of elevated nitrogen (N) deposition and increased precipitation on plant taxonomic and phylogenetic β‐diversity in a 9‐year field experiment in the temperate semi‐arid steppe of Inner Mongolia, China. We found that both N and water addition significantly increased taxonomic β‐diversity, whereas N, not water, addition significantly increased phylogenetic β‐diversity. After the differences in local species diversity were controlled using null models, the standard effect size of taxonomic β‐diversity still increased with both N and water addition, whereas water, not N, addition, significantly reduced the standard effect size of phylogenetic β‐diversity. The increased phylogenetic convergence observed in the water addition treatment was associated with colonizing species in each water addition plot being more closely related to species in other replicate plots of the same treatment. Species colonization in this treatment was found to be trait‐based, with leaf nitrogen concentration being the key functional trait. Synthesis. Our analyses demonstrate that anthropogenic environmental changes may affect the assembly trajectories of plant communities at both taxonomic and phylogenetic scales. Our results also suggest that while stochastic processes may cause communities to diverge in species composition, deterministic process could still drive communities to converge in phylogenetic community structure.

Estuaries are one of the most crucial areas for the transformation and burial of terrestrial organic carbon (TerrOC), playing an important role in the global carbon cycle. While the transformation and degradation of TerrOC are mainly driven by microorganisms, the specific taxa and degradation processes involved remain largely unknown in estuaries. We collected surface sediments from 14 stations along the longitudinal section of the Pearl River Estuary (PRE), P. R. China. By combining analytical chemistry, metagenomics, and bioinformatics methods, we analyzed composition, source and degradation pathways of lignin/lignin-derived aromatic fragments and their potential decomposers in these samples. A diversity of bacterial and archaeal taxa, mostly those from Proteobacteria (Deltaproteobacteria, Gammaproteobacteria etc.), including some lineages (e.g., Nitrospria, Polyangia, Tectomicrobia_uc) not previously implicated in lignin degradation, were identified as potential polymeric lignin or its aromatic fragments degraders. The abundance of lignin degradation pathways genes exhibited distinct spatial distribution patterns with the area adjacent to the outlet of Modaomen as a potential degradation hot zone and the Syringyl lignin fragments, 3,4-PDOG, and 4,5-PDOG pathways as the primary potential lignin aromatic fragments degradation processes. Notably, the abundance of ferulic acid metabolic pathway genes exhibited significant correlations with degree of lignin oxidation and demethylation/demethoxylization and vegetation source. Additionally, the abundance of 2,3-PDOG degradation pathways genes also showed a positive significant correlation with degree of lignin oxidation. Our study provides a meaningful insight into the microbial ecology of TerrOC degradation in the estuary.

We are living in a new epoch—the Anthropocene, in which human activity is reshaping global biodiversity at an unprecedented rate. Increasing efforts are being made toward a better understanding of the associations between human activity and the geographic patterns in plant and animal communities. However, similar efforts are rarely applied to microbial communities. Here, we collected 472 forest soil samples across eastern China, and the bacterial and fungal communities in those samples were determined by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer region, respectively. By compiling human impact variables as well as climate and soil variables, our goal was to elucidate the association between microbial richness and human activity when climate and soil variables are taken into account. We found that soil microbial richness was associated with human activity. Specifically, human population density was positively associated with the richness of bacteria, nitrifying bacteria and fungal plant pathogens, but it was negatively associated with the richness of cellulolytic bacteria and ectomycorrhizal fungi. Together, these results suggest that the associations between geographic variations of soil microbial richness and human activity still persist when climate and soil variables are taken into account and that these associations vary among different microbial taxonomic and functional groups.

The study of islands has made substantial contributions to the development of evolutionary and ecological theory. However, we know little about microbial community assembly on islands. Using soil microbial data collected from 29 lake islands and nearby mainland, we examined the assembly mechanisms of soil bacterial and fungal communities among and within islands. We found that deterministic processes, especially homogeneous selection, tended to be more important in shaping the assembly of soil bacterial communities among islands, while stochastic processes tended to be more important within islands. Moreover, increasing island area increased the importance of homogeneous selection, but reduced the importance of variable selection, for soil bacterial community assembly within islands. By contrast, stochastic processes tended to dominate soil fungal community assembly both among and within islands, with dispersal limitation playing a more important role within than among islands. Our results highlight the scale- and taxon-dependence of insular soil microbial community assembly, suggesting that spatial scale should be explicitly considered when evaluating the influences of habitat fragmentation on soil microbial communities.

Author(s): Wang, P; Chen, Y; Sun, Y; Tan, S; Zhang, S; Wang, Z; Zhou, J; Zhang, G; Shu, W; Luo, C; Kuang, J | Abstract: Plant pathogens are increasingly considered as important agents in promoting plant coexistence, while plant symbionts like ectomycorrhizal fungi (EMF) can facilitate plant dominance by helping conspecific individuals to defend against plant pathogens. However, we know little about their relationships with plants at large scales. Here, using soil fungal data collected from 28 forest reserves across China, we explored the latitudinal diversity gradients of overall fungi and different fungal functional guilds, including putative plant pathogens, EMF, and saprotrophic fungi. We further linked the spatial patterns of alpha diversities of putative plant pathogens and EMF to the variation of plant species richness. We found that the relationships between latitude and alpha diversities of putative plant pathogens and EMF were region-dependent with sharp diversity shifts around the mid-latitude (~35°N), which differed from the unimodal diversity distributions of the overall and saprotrophic fungi. The variations in the diversities of putative plant pathogens and EMF were largely explained by the spatial regions (south vs. north/subtropical zone vs. temperate zone). Additionally, the alpha diversities of these two fungal guilds exhibited opposing trends across latitude. EMF could alter the relationship between diversities of putative plant pathogens and plants in the south/subtropical region, but not vice versa. We also found that the ratio of their alpha diversities (EMF to putative plant pathogens) was negatively related to plant species richness across the spatial regions (north to south), and explained ~10% of the variation of plant species richness. Overall, our findings suggest that plant-microbe interactions not only shape the local plant diversity but also may have non-negligible contributions to the large-scale patterns of plant diversity in forest ecosystems.

Terrestrial organic carbon-lignin plays a crucial role in the global carbon balance. However, limited studies presented the functional and ecological traits of lignin decomposers population in natural aquatic ecosystem. In this study, we performed a multi-omics analysis by deploying amplicon, metagenomic, and metatranscriptomic approaches to identify the key potential degraders and pathways involved lignin-derived aromatic compounds in the later stage of lignin degradation. By establishing microcosms with model lignin-derived aromatic compound (vanillic acid, VAN), based on the estimated absolute abundance (EAA) and the metagenome-assembled genomes (MAGs), novel potential lignin-derived aromatic compounds degraders were identified in the aquatic ecosystem. Furthermore, members of the phyla Proteobacteria and Actinobacteria were the potential major lignin-derived aromatic compounds degraders in the studied ecosystem. Our study demonstrated that genomes of the class Betaproteobacteria (Proteobacteria) possess a complete enzymatic system for the degradation of diarylpropanes, vanillate and protocatechuate, besides having the capacity to degrade other lignin-derived aromatic compounds. This study provides strong evidence for the ability of aquatic bacteria to degrade lignin-derived aromatic compounds and suggest that different microbes might occupy different niches in the later stage of lignin degradation.

Bacterioplankton are the major driving force for biogeochemical cycles in estuarine ecosystems, but the communities that mediate these processes are largely unexplored. We sampled in the Pearl River Estuary (PRE) to examine potential differences in the taxonomic composition of resident (DNA-based) and active (RNA-based) bacterioplankton communities in free-living and particle-associated fractions. MiSeq sequencing data showed that the overall bacterial diversity in particle-associated fractions was higher than in free-living communities. Further in-depth analyses of the sequences revealed a positive correlation between resident and active bacterioplankton communities for the particle-associated fraction but not in the free-living fraction. However, a large overlapping of OTUs between free-living and particle-associated communities in PRE suggested that the two fractions may be actively exchanged. We also observed that the positive correlation between resident and active communities is more prominent among the abundant OTUs (relative abundance > 0.2%). Further, the results from the present study indicated that low-abundance bacterioplankton make an important contribution towards the metabolic activity in PRE.

Microbial community composition is essential for aquatic ecosystem functions and has been explored across diverse environments and various spatial scales. However, documented patterns are often based on samples from spatially/geographically separated locations or sites. Here, we define sampling volume as spatial scale and examine (by Illumina 16S rRNA sequencing) microbial community composition over a scale of 1 mL to 10 L in an acid mine drainage. β-Diversity analysis revealed that all samples grouped very tightly according to spatial scales and variations between every two scales were significant. Notably, mean β-diversity within each group was negatively correlated with spatial scales, indicating patchy microbial distribution. Partition of β-diversity further revealed that it was the relative abundances of some microbial taxa that largely changed among spatial scales. Phylogenetic analysis showed that microbial lineages were not randomly distributed, but displayed a tendency of more phylogenetically clustering at smaller spatial scales. Thus, we documented fine-scale spatial patterns in microbial community composition within a continuous aquatic environment, which may have practical implications for adequate sampling of aquatic systems in future studies.

Estimating the species richness of microorganisms is of great importance in predicting, maintaining and managing microbial communities. Although the roles of environmental heterogeneity and geographical distance in structuring soil microbial communities have been studied intensively, the effects of environmental and spatial variation on the species richness estimation have not been examined. To this end, we have explored their effects on estimating the belowground soil bacterial species richness within a 50 ha forest dynamic plot (FDP) using a published massive sequencing dataset with intensive sampling scheme. Our resampling analyses showed that, for a given sequencing depth, increasing the sample size could significantly enhance the detection of rare species by capturing more of the environmental and spatial variation, thus obtaining higher observed and estimated species richness. Additionally, the estimates of bacterial species richness were significantly and positively correlated with environmental variation among samples, indicating that environmental filtering was the main mechanism driving the processes of community assembly for belowground soil bacterial communities in the plot. Moreover, this effect of environmental variation could be markedly alleviated when the sample size was higher than 450, and thus we predicted that there were at least 42,866 soil bacterial species based on 8,296,878 sequences from 550 samples in the whole 50 ha FDP. Furthermore, we built a power law environmental heterogeneity equation (EHE) as a decision-tool to determine an approximate sample size for comprehensively capturing the environmental gradient within a given habitat. Collectively, this work further links the inherent environmental and spatial variation to the estimation of soil bacterial species richness within a given region, and provides a useful tool of sampling design for a better understanding of microbial biogeographic patterns and estimation of microbial biodiversity.