Actinotalea lenta sp. nov., a novel actinomycete isolated from tidal flat sediment.

Two Gram-stain-positive, aerobic, oxidase- and catalase-negative, non-motile, and short rod-shaped actinomycetes, named SYSU T00b441T and SYSU T00b490, were isolated from tidal flat sediment located in Guangdong province, PR China. The 16S rRNA gene sequence similarity, average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between SYSU T00b441T and SYSU T00b490 were 99.3, 99.5 and 97.1 %, respectively. Strains SYSU T00b441T and SYSU T00b490 exhibited the highest 16S rRNA gene sequence similarities to Actinotalea ferrariae CF 5-4T (97.1 %/98.2 %), with ANI values of 74.01/73.88 % and dDDH values of 20.5/20.4 %. In the phylogenomic tree, the two isolates were affiliated with the genus Actinotalea. The genomes of strains SYSU T00b441T and SYSU T00b490 were 3.31 and 3.34 Mb, and both had DNA G+C contents of 72.8 mol%, coding 3077 and 3085 CDSs, three and three rRNA genes, and 53 and 51 tRNAs, respectively. Growth occurred at 15-40 °C (optimum, 28-30 °C), pH 4.0-10.0 (optimum, 7.0) and in the presence of 0-7 % (w/v) NaCl (optimum, 3 %). The major fatty acids (>10  %) of strains SYSU T00b441T and SYSU T00b490 were anteiso-C15 : 0 and C16 : 0. The major respiratory quinone was identified as MK-10(H4). The polar lipids of strains SYSU T00b441T and SYSU T00b490 were diphosphatidyl glycerol, phosphatidylglycerol, phosphoglycolipid, phosphatidyl ethanolamine, two phosphatidylinositol mannosides, two glycolipids and two phospholipids. Based on these data, the two strains (SYSU T00b441T and SYSU T00b490) represent a novel species of the genus Actinotalea, for which the name Actinotalea lenta sp. nov is proposed. The type strain is SYSU T00b441T (=GDMCC 1.3827T=KCTC 49943T).

Response of microbial diversity and function to the degradation of Barkol Saline Lake.

Barkol Lake, a shrinking hypersaline lake situated in the northeast of Xinjiang, China, has experienced the exposure of its riverbed and the gradual drying up of its original sediment due to climate change and human activities, resulting in the formation of alkaline soils. These changes have correspondingly altered the physicochemical characteristics of the surrounding environment. Microorganisms play a crucial role, with special functioning involved in various nutrient cycling and energy transfer in saline lake environments. However, little is known about how the microbial community dynamics and metabolic functions in this shrinking saline lake relate to the degradation process. To address this knowledge gap, a cultivation-independent method of amplicon sequencing was used to identify and analyze the microbial community and its potential ecological functions in the sediment and degraded area. The microbial community diversity was found to be significantly lower in the degraded areas than in the sediment samples. The Pseudomonadota was dominant in Barkol Saline Lake. The abundance of Desulfobacterota and Bacillota in the degraded areas was lower than in the lake sediment, while Pseudomonadota, Acidobacteriota, and Actinobacteriota showed an opposite trend. The ßNTI showed that microbial community assembly was primarily associated with deterministic processes in Barkol Saline Lake ecosystems and stochastic processes at the boundary between sediment and degraded areas. Functional predictions showed that sulfur metabolism, particularly sulfate respiration, was much higher in sediment samples than in the degraded areas. Overall, these findings provided a possible perspective for us to understand how microorganisms adapt to extreme environments and their role in saline lakes under environmental change.

Two Novel Alkaliphilic Species Isolated from Saline-Alkali Soil in China: Halalkalibacter flavus sp. nov., and Halalkalibacter lacteus sp. nov.

The degradation of farmland in China underscores the need for developing and utilizing saline-alkali soil. Soil health relies on microbial activity, which aids in the restoration of the land's ecosystem, and hence it is important to understand microbial diversity. In the present study, two Gram-stain-positive strains HR 1-10T and J-A-003T were isolated from saline-alkali soil. Preliminary analysis suggested that these strains could be a novel species. Therefore, the taxonomic positions of these strains were evaluated using polyphasic analysis. Phylogenetic and 16S rRNA gene sequence analysis indicated that these strains should be assigned to the genus Halalkalibacter. Cell wall contained meso-2,6-diaminopimelic acid. The polar lipids present in both strains were diphosphatidyl-glycerol, phosphatidylglycerol, and an unidentified phospholipid. The major fatty acids (>10%) were anteiso-C15:0, C16:0 and iso-C15:0. Average nucleotide identity and digital DNA#x2013;DNA hybridization values were below the threshold values (95% and 70%, respectively) for species delineation. Based on the above results, the strains represent two novel species of the genus Halalkalibacter, for which the names Halalkalibacter flavus sp. nov., and Halalkalibacter lacteus sp. nov., are proposed. The type strains are HR 1-10T (=GDMCC 1.2946T = MCCC 1K08312T = JCM 36285T), and J-A-003T (=GDMCC 1.2949T = MCCC 1K08417T = JCM 36286T).

Chelativorans salis sp. nov., a slightly halophilic bacterium isolated from an enrichment system with saline lake sediment.

A Gram-stain-negative, non-motile, and slightly halophilic alphaproteobacterium, designated strain EGI FJ00035T, was isolated from enrichment sediment samples of a saline lake in Xinjiang Uygur Autonomous Region, PR China. The taxonomic position of the isolate was determined using the polyphasic taxonomic and phylogenomic analyses. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain EGI FJ00035T formed a distinct clade with 'Chelativorans alearense' UJN715 and 'Chelativorans xinjiangense' lm93 with sequence similarities of 98.44 and 98.22 %, respectively, while sharing less than 96.7 % with other valid type strains. The novel isolate could be distinguished from other species of the genus Chelativorans by its distinct phenotypic, physiological, and genotypic characteristics. Optimal growth of strain EGI FJ00035T occurred on marine agar 2216 at pH 7.0 and 30 °C. The major respiratory quinone was Q-10, while the major fatty acids (>5 %) were C19 : 0 cyclo ω8c, summed feature 8 (C17 : 1 ω6c and/or C17 : 1 ω7c), C16 : 0, C18 : 0, and iso-C17 : 0. The detected polar lipids included diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, unidentified aminophospholipids, unidentified glycolipids, and an unidentified lipid. Based on its genome sequence, the G+C content of strain EGI FJ00035T was 63.2 mol%. The average nucleotide identity, average amino acid identity, and digital DNA-DNA hybridization values of strain EGI FJ00035T against related members of the genus Chelativorans were below the thresholds for delineation of a novel species. According our polyphasic taxonomic data, strain EGI FJ00035T represents a new species of the genus Chelativorans, for which the name Chelativorans salis sp. nov. is proposed. The type strain of the proposed novel isolate is EGI FJ00035T (=KCTC 92251T=CGMCC 1.19480T).

Proximity to the water surface markedly enhances the force production on underwater flapping wings.

The potential application of flapping wings in micro-aerial vehicles is gaining interest due to their ability to generate high lift even in confined spaces. Most studies in the past have investigated hovering wings as well as those flapping near solid surfaces. However, the presence of surface tension at the water-air interface and the ability of the water surface to move might differentiate its response to the proximity of wings, compared to that of solid surfaces. Motivated by underwater, amphibian robots and several underwater experimental studies on flapping wings, our study investigated the effects of the proximity of flapping wings to the water surface at low Reynolds numbers (Re = 3400). Experiments were performed on a rectangular wing in a water tank with prescribed flapping kinematics and the aerodynamic forces were measured. The effects of surface proximity on the wing in its both upright and inverted orientations were studied. Broadly, the mean lift and drag coefficients in both orientations decreased significantly (by up to 60%) as the distance from the water surface was increased. In the case of the upright orientation, the mean lift coefficient was slightly decreased very close to the water surface with its peak being observed at the normalized clearance of [Formula: see text]. Overall, the study revealed an enhancement in the aerodynamic forces closer to the water surface.

Fundicoccus culcitae sp. nov., a novel potential bacteriocin producing bacterium isolated from a spoiled eye mask.

A Gram-positive, facultatively anaerobic, oval beaded-shape, oxidase-negative, and non-motile bacterium designated DM20194951T was isolated from a spoiled eye mask obtained from Guangdong, China. Based on the 16S rRNA gene sequence, phylogenetic analysis indicated that strain DM20194951T showed the highest sequence similarity (95.8%) to Fundicoccus ignavus WS4937T. Meanwhile, strain DM20194951T could be distinguished from the type strains in the genus Fundicoccus by distinct phenotypic and genotypic traits. Strain DM20194951T grew variably with 1-2% (w/v) NaCl and tolerated pH 6.0-10.0. Growth was observed from 28 to 37 °C. The diagnostic diamino acids in the cell-wall peptidoglycan consisted of aspartic and glutamic acids as well as alanine. The predominant fatty acids were C18:1 ω9c, C16:0, and C16:1 ω9c. In the polar lipid profile, two glycolipids, three phospholipids, one phosphatidylglycerol, and one diphosphatidylglycerol were found. No respiratory quinones were detected. The DM20194951T genome is 3.2 Mb in size and contains a G + C content of 38.1%. A gene cluster for lactococcin 972 family bacteriocin production was found in the DM20194951T genome. Based on morphological, genotypic, and phylogenetic data, strain DM20194951T should be considered to represent a novel species in the genus Fundicoccus, for which the name Fundicoccus culcitae sp. nov. is proposed with the type strain DM20194951T (= KCTC 43472T = GDMCC 1.3614T).

Microbial Risks Caused by Livestock Excrement: Current Research Status and Prospects.

Livestock excrement is a major pollutant yielded from husbandry and it has been constantly imported into various related environments. Livestock excrement comprises a variety of microorganisms including certain units with health risks and these microorganisms are transferred synchronically during the management and utilization processes of livestock excrement. The livestock excrement microbiome is extensively affecting the microbiome of humans and the relevant environments and it could be altered by related environmental factors as well. The zoonotic microorganisms, extremely zoonotic pathogens, and antibiotic-resistant microorganisms are posing threats to human health and environmental safety. In this review, we highlight the main feature of the microbiome of livestock excrement and elucidate the composition and structure of the repertoire of microbes, how these microbes transfer from different spots, and they then affect the microbiomes of related habitants as a whole. Overall, the environmental problems caused by the microbiome of livestock excrement and the potential risks it may cause are summarized from the microbial perspective and the strategies for prediction, prevention, and management are discussed so as to provide a reference for further studies regarding potential microbial risks of livestock excrement microbes.

Aquiflexum gelatinilyticum sp. nov., isolated from river water.

Two Gram-stain-negative, strictly aerobic, rod-shaped, non-motile and non-gliding bacteria, designated as XJ19-10T and XJ19-11, were isolated from river water in Xinjiang Uygur Autonomous Region, PR China. Cells of these strains were catalase-, oxidase- and gelatinase-positive and contained carotenoids but no flexirubins. Growth occurred at 10-30 °C, pH 7.0-9.0 and with 0-2.5% (w/v) NaCl. On the basis of the results of 16S rRNA gene sequence and genome analyses, the two isolates represented members of the genus Aquiflexum, and the closest relative was Aquiflexum aquatile Z0201T with 16S rRNA gene sequence pairwise similarities of 97.9-98.1%. Furthermore, the average nucleotide identities and digital DNA-DNA hybridization identities between the two isolates and other relatives were all less than 82.9 and 28.2 %, respectively, all below the species delineation thresholds. The results of pan-genomic analysis indicated that the type strain XJ19-10T shared 2813 core gene clusters with other three type strains of members of the genus Aquiflexum, as well as having 623 strain-specific clusters. The major polar lipids were phosphatidylethanolamine, phosphatidylcholine, an unidentified aminolipid and unidentified lipids. The predominant fatty acids (>10% of the total contents) were iso-C15 : 0, iso-C15 : 1G, iso-C17 : 0 3-OH and summed feature 9, and MK-7 was the respiratory quinone. On the basis of the results of phenotypic, physiological, chemotaxonomic and genotypic characterization, strains XJ19-10T and XJ19-11 are considered to represent a novel species, for which the name Aquiflexum gelatinilyticum sp. nov. is proposed. The type strain is XJ19-10T (=CGMCC 1.19385T =KCTC 92266T).

Salinibacterium sedimenticola sp. nov., Isolated from Tidal Flat Sediment.

An actinobacterium, designated as SYSU T00001T, was isolated from a tidal flat sediment sample from Guangdong province, China. Cells were Gram-stain-positive, aerobic, motile and short rod-shaped. Colonies on marine agar 2216 were smooth, yellow-pigmented, and circular with low convexity. The isolate was able to grow at the temperature range 4-37 °C (optimum 30 °C), at pH 4.0-10.0 (optimum 7.0) and in the presence of 0-10% (w/v) NaCl. The major menaquinones were MK-11 and MK-10. The cell wall contained alanine, glutamic acid, lysine and ornithine. The major fatty acids were C19:0 cyclo ω8c (35.7%) and anteiso C15:0 (26.0%). The polar lipids consisted of one diphosphatidyl glycerol, one unidentified glycolipid and one unknown lipid. Whole genome sequencing of strain SYSU T00001T revealed 2,837,702 bp with a DNA G + C content of 67.8%. Phylogenetic analyses clearly demonstrated that strain SYSU T00001T belonged to the genus Salinibacterium, and the highest 16S rRNA gene similarity to Salinibacterium hongtaonis 194T (97.8%). The ANI and dDDH values of strain SYSU T00001T relative to Salinibacterium hongtaonis 194T were 74.5% and 19.5%, respectively. According to our data, strain SYSU T00001T represents a novel species of the genus Salinibacterium, for which the name Salinibacterium sedimenticola sp. nov. is proposed, the type strain is SYSU T00001T (= GDMCC 1.3283T = KCTC 49758T).

Sediment prokaryotic microbial community and potential biogeochemical cycle from saline lakes shaped by habitat.

The microbial diversity and ecological function in different saline lakes was reduced or disappeared as the influence of climate change and human activities even before they were known. However, reports about prokaryotic microbial of saline lakes from Xinjiang are very limited especially in large-scale investigations. In this study, a total of 6 saline lakes represented three different habitats, including hypersaline lake (HSL), arid saline lake (ASL), and light saltwater lake (LSL) were involved. The distribution pattern and potential functions of prokaryotes were investigated by using the cultivation-independent method of amplicon sequencing. The results showed that Proteobacteria was the predominant community and was widely distributed in all kinds of saline lakes, Desulfobacterota was the representative community in hypersaline lakes, Firmicutes and Acidobacteriota were mainly distributed in arid saline lake samples, and Chloroflexi was more abundant in light saltwater lakes. Specifically, the archaeal community was mainly distributed in the HSL and ASL samples, whereas it was very rare in the LSL lakes. The functional group showed that fermentation was the main metabolic process of microbes in all saline lakes and covered 8 phyla, including Actinobacteriota, Bacteroidota, Desulfobacterota, Firmicutes, Halanaerobiaeota, Proteobacteria, Spirochaetota, and Verrucomicrobiota. Among the 15 functional phyla, Proteobacteria was a distinctly important community in saline lakes, as it exhibited wide functions in the biogeochemical cycle. According to the correlation of environmental factors, SO42-, Na+, CO32-, and TN were significantly affected in the microbial community from saline lakes in this study. Overall, our study provided more detailed information about microbial community composition and distribution from three different habitats of saline lakes, especially the potential functions of carbon, nitrogen, and sulfur cycles, which provided new insight for understanding the complex microbiota adapt to the extreme environment and new perspectives on evaluating microbial contributions to degraded saline lakes under environmental change.

[Effects of Different Topdressing Nitrogen Rates on Soil Fungal Community Structure and Ecological Network in Wheat Field Under Crop Residue Retention].

Crop residue retention and fertilizer application are the main sources of soil nutrient input in fields. Crop residue retention combined with appropriate fertilizer application rates could provide necessary nutrients for crop production under the premise of environmentally friendly conditions. The aim of this study was to clarify the influence of different topdressing nitrogen rates on the soil fungal community in a wheat field under crop residue retention and to evaluate the rationality of nitrogen fertilizer management in winter wheat from the perspective of soil ecological function. On the basis of full straw retention and 150 kg·hm-2 basal nitrogen, treatments with five topdressing nitrogen rates (0, 37.5, 75, 112.5, and 150 kg·hm-2) were set up. The abundance, diversity, structure, and ecological network of soil fungal communities were analyzed using real-time fluorescence quantitative PCR and high-throughput sequencing, and the main soil physical and chemical factors driving the change in soil fungal communities were explored. The results showed that, compared with the no topdressing nitrogen and low topdressing nitrogen rate treatments, high topdressing nitrogen rate treatments increased soil total nitrogen and mineral nitrogen and decreased soil pH, total phosphorus, available phosphorus, and available potassium. Compared with the no topdressing nitrogen treatments, the 37.5-150 kg·hm-2 topdressing nitrogen treatments significantly increased soil fungal community abundance (P<0.05), whereas there was no significant difference among different topdressing nitrogen treatments (P>0.05). The Heip index and Shannon index of soil fungal communities decreased gradually with the increase in topdressing nitrogen rate, and the Sobs index, Heip index, and Shannon index of soil fungal communities in the treatment with 150 kg·hm-2 topdressing nitrogen were significantly lower than those of 0-75 kg·hm-2 topdressing nitrogen treatments (P<0.05). Principal component analysis and similarity analysis showed that there were significant differences in soil fungal community structure under different topdressing nitrogen rate treatments (P<0.05). With the increase in topdressing nitrogen rate, the number of network edges and average number of neighbors of soil fungal ecological network increased first and then decreased, and the network complexity of 37.5 kg·hm-2 topdressing nitrogen treatments was the highest. Compared with 0-75 kg·hm-2 topdressing nitrogen treatments, 112.5 kg·hm-2 and 150 kg·hm-2 topdressing nitrogen treatments increased the characteristic path length of the soil fungal ecological network, whereas it decreased the network density. With the increase in topdressing nitrogen rate, the relative abundance of soil saprotrophs gradually increased, and the pathotroph-saprotroph-symbiotroph relative abundance gradually decreased. Redundancy analysis showed that soil pH, total phosphorus, mineral nitrogen, available phosphorus, and available potassium were the main soil physicochemical factors affecting the soil fungal community structure in the wheat field under different topdressing nitrogen rate treatments. In conclusion, on the basis of straw retention and basal nitrogen, topdressing nitrogen at the wheat jointing stage could change the diversity, structure, and species composition of the soil fungal community, in turn affecting the soil fungal ecological network and function, and high topdressing nitrogen rates could reduce soil fungal community diversity, ecological network complexity, and network density.

Culturomics- and metagenomics-based insights into the microbial community and function of rhizosphere soils in Sinai desert farming systems.

BACKGROUND: The microbiome of the Sinai Desert farming system plays an important role in the adaptive strategy of growing crops in a harsh, poly-extreme, desert environment. However, the diversity and function of microbial communities under this unfavorable moisture and nutritional conditions have not yet been investigated. Based on culturomic and metagenomic methods, we analyzed the microbial diversity and function of a total of fourteen rhizosphere soil samples (collected from twelve plants in four farms of the Sinai desert), which may provide a valuable and meaningful guidance for the design of microbial inoculants. RESULTS: The results revealed a wide range of microbial taxa, including a high proportion of novel undescribed lineages. The composition of the rhizosphere microbial communities differed according to the sampling sites, despite similarities or differences in floristics. Whereas, the functional features of rhizosphere microbiomes were significantly similar in different sampling sites, although the microbial communities and the plant hosts themselves were different. Importantly, microorganisms involved in ecosystem functions are different between the sampling sites, for example nitrogen fixation was prevalent in all sample sites while microorganisms responsible for this process were different. CONCLUSION: Here, we provide the first characterization of microbial communities and functions of rhizosphere soil from the Sinai desert farming systems and highlight its unexpectedly high diversity. This study provides evidence that the key microorganisms involved in ecosystem functions are different between sampling sites with different environment conditions, emphasizing the importance of the functional microbiomes of rhizosphere microbial communities. Furthermore, we suggest that microbial inoculants to be used in future agricultural production should select microorganisms that can be involved in plant-microorganism interactions and are already adapted to a similar environmental setting.

Insights into the effects of drying treatments on cultivable microbial diversity of marine sediments.

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.

Cultivation strategies for prokaryotes from extreme environments.

The great majority of microorganisms are as-yet-uncultivated, mostly found in extreme environments. High-throughput sequencing provides data-rich genomes from single-cell and metagenomic techniques, which has enabled researchers to obtain a glimpse of the unexpected genetic diversity of "microbial dark matter." However, cultivating microorganisms from extreme environments remains essential for dissecting and utilizing the functions of extremophiles. Here, we provide a straightforward protocol for efficiently isolating prokaryotic microorganisms from different extreme habitats (thermal, xeric, saline, alkaline, acidic, and cryogenic environments), which was established through previous successful work and our long-term experience in extremophile resource mining. We propose common processes for extremophile isolation at first and then summarize multiple cultivation strategies for recovering prokaryotic microorganisms from extreme environments and meanwhile provide specific isolation tips that are always overlooked but important. Furthermore, we propose the use of multi-omics-guided microbial cultivation approaches for culturing these as-yet-uncultivated microorganisms and two examples are provided to introduce how these approaches work. In summary, the protocol allows researchers to significantly improve the isolation efficiency of pure cultures and novel taxa, which therefore paves the way for the protection and utilization of microbial resources from extreme environments.

Viral community-wide auxiliary metabolic genes differ by lifestyles, habitats, and hosts.

BACKGROUND: Viral-encoded auxiliary metabolic genes (AMGs) are important toolkits for modulating their hosts' metabolisms and the microbial-driven biogeochemical cycles. Although the functions of AMGs have been extensively reported in numerous environments, we still know little about the drivers that shape the viral community-wide AMG compositions in natural ecosystems. Exploring the drivers of viral community-wide AMG compositions is critical for a deeper understanding of the complex interplays among viruses, hosts, and the environments. RESULTS: Here, we investigated the impact of viral lifestyles (i.e., lytic and lysogenic), habitats (i.e., water, particle, and sediment), and prokaryotic hosts on viral AMG profiles by utilizing metagenomic and metatranscriptomic techniques. We found that viral lifestyles were the most important drivers, followed by habitats and host identities. Specifically, irrespective of what habitats viruses came from, lytic viruses exhibited greater AMG diversity and tended to encode AMGs for chaperone biosynthesis, signaling proteins, and lipid metabolism, which could boost progeny reproduction, whereas temperate viruses were apt to encode AMGs for host survivability. Moreover, the lytic and temperate viral communities tended to mediate the microbial-driven biogeochemical cycles, especially nitrogen metabolism, in different manners via AMGs. When focusing on each lifestyle, we further found clear dissimilarity in AMG compositions between water and sediment, as well the divergent AMGs encoded by viruses infecting different host orders. CONCLUSIONS: Overall, our study provides a first systematic characterization of the drivers of viral community-wide AMG compositions and further expands our knowledge of the distinct interactions of lytic and temperate viruses with their prokaryotic hosts from an AMG perspective, which is critical for understanding virus-host-environment interactions in natural conditions. Video Abstract.

Learning to school in dense configurations with multi-agent deep reinforcement learning.

Fish are observed to school in different configurations. However, how and why fish maintain a stable schooling formation still remains unclear. This work presents a numerical study of the dense schooling of two free swimmers by a hybrid method of the multi-agent deep reinforcement learning and the immersed boundary-lattice Boltzmann method. Active control policies are developed by synchronously training the leader to swim at a given speed and orientation and the follower to hold close proximity to the leader. After training, the swimmers could resist the strong hydrodynamic force to remain in stable formations and meantime swim in desired path, only by their tail-beat flapping. The tail movement of the swimmers in the stable formations are irregular and asymmetrical, indicating the swimmers are carefully adjusting their body-kinematics to balance the hydrodynamic force. In addition, a significant decrease in the mean amplitude and the cost of transport is found for the followers, indicating these swimmers could maintain the swimming speed with less efforts. The results also show that the side-by-side formation is hydrodynamically more stable but energetically less efficient than other configurations, while the full-body staggered formation is energetically more efficient as a whole.

[Soil bacterial communities of different crop rotations and yield of succeeding wheat.] / 不同轮作茬口土壤细菌群落及后茬小麦产量.

Evaluating ecological sustainability and crop productivity of different crop rotation patterns could provide theoretical support for adjusting and optimizing crop planting structure. We set seven treatments with different rotation crops and periods. We used real-time quantitative PCR to determine the abundance of soil bacterial community and 16S rRNA gene amplicon high-throughput sequencing technology to analyze diversity and taxa composition of soil bacterial community. Both soil available nutrients and succeeding wheat yield were measured. The results showed that, compared with the rotation with summer maize, the rotations with summer peanut or soybean in diffe-rent periods reduced soil organic carbon, mineral nitrogen, and available potassium, but significantly increased soil available phosphorus. The 16S rRNA gene copy numbers of soil bacteria in the treatments of rotations with summer peanut or soybean in different periods were significantly decreased, while community richness and diversity were increased. Different rotation crops significantly changed the structure and taxonomic composition of soil bacterial community. Compared with the rotation with summer maize, the rotations with summer soybean in different periods significantly increased the 1000-grain weight and grain yield of succeeding winter wheat. In conclusion, rotations with summer peanut or soybean in different periods could increase soil available phosphorus content and bacterial diversity, and significantly change soil bacterial community structure. In particular, rotation with summer soybean performed best in promoting yield formation of succeeding winter wheat.

Functional differentiation determines the molecular basis of the symbiotic lifestyle of Ca. Nanohaloarchaeota.

BACKGROUND: Candidatus Nanohaloarchaeota, an archaeal phylum within the DPANN superphylum, is characterized by limited metabolic capabilities and limited phylogenetic diversity and until recently has been considered to exclusively inhabit hypersaline environments due to an obligate association with Halobacteria. Aside from hypersaline environments, Ca. Nanohaloarchaeota can also have been discovered from deep-subsurface marine sediments. RESULTS: Three metagenome-assembled genomes (MAGs) representing a new order within the Ca. Nanohaloarchaeota were reconstructed from a stratified salt crust and proposed to represent a novel order, Nucleotidisoterales. Genomic features reveal them to be anaerobes capable of catabolizing nucleotides by coupling nucleotide salvage pathways with lower glycolysis to yield free energy. Comparative genomics demonstrated that these and other Ca. Nanohaloarchaeota inhabiting saline habitats use a "salt-in" strategy to maintain osmotic pressure based on the high proportion of acidic amino acids. In contrast, previously described Ca. Nanohaloarchaeota MAGs from geothermal environments were enriched with basic amino acids to counter heat stress. Evolutionary history reconstruction revealed that functional differentiation of energy conservation strategies drove diversification within Ca. Nanohaloarchaeota, further leading to shifts in the catabolic strategy from nucleotide degradation within deeper lineages to polysaccharide degradation within shallow lineages. CONCLUSIONS: This study provides deeper insight into the ecological functions and evolution of the expanded phylum Ca. Nanohaloarchaeota and further advances our understanding on the functional and genetic associations between potential symbionts and hosts. Video Abstract.