Acidithiobacillus species mediated mineral weathering promotes lead immobilization in ferric-silica microstructures at sulfidic tailings.

Immobilization and stabilization of heavy metals (HMs) in sulfidic and metallic tailings are critical to long-term pollution control and sustainable ecological rehabilitation. This study aims to unravel immobilization mechanisms of Pb (Ⅱ) in the neoformed hardpan structure resulting from Acidithiobacillus spp. accelerated bioweathering of sulfides in the presence of silicates. It was found that the bioweathered mineral composite exhibited an elevated Pb (Ⅱ) adsorption capacity compared to that of natural weathered mineral composite. A suit of microspectroscopic techniques such as synchrotron-based X-ray Absorption Spectroscopy (XAS), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Field-Emission Scanning Electron Microscope (FE-SEM) indicated that secondary Fe-bearing minerals, functional groups, and surface properties in the neoformed hardpan were key factors contributing to Pb (Ⅱ) adsorption and immobilization in ferric-silica microstructures. The underlying mechanisms might involve surface adsorption-complexation, dissolution-precipitation, electrostatic attraction, and ion exchange. Microbial communities within the muscovite groups undergoing bioweathering processes demonstrated distinctive survival strategies and community composition under the prevailing geochemical conditions. This proof of concept regarding Pb (Ⅱ) immobilization in microbial transformed mineral composite would provide the basis for scaling up trials for developing field-feasible methodology to management HMs pollution in sulfidic and metallic tailings in near future.

Removal of artificial sweeteners in wastewater treatment plants and their degradation during sewage sludge composting with micro- and nano-sized kaolin.

This study surveyed the fates of artificial sweeteners in influent, effluent, and sewage sludge (SS) in wastewater treatment plant, and investigated the effects of Micro-Kaolin (Micro-KL) and Nano-Kaolin (Nano-KL) on nitrogen transformation and sucralose (SUC) and acesulfame (ACE) degradation during SS composting. Results showed the cumulative rate of ACE and SUC in SS was ∼76 %. During SS composting, kaolin reduced NH3 emissions by 30.2-45.38 %, and N2O emissions by 38.4-38.9 %, while the Micro-KL and Nano-KL reduced nitrogen losses by 14.8 % and 12.5 %, respectively. Meanwhile, Micro-KL and Nano-KL increased ACE degradation by 76.8 % and 84.2 %, and SUC degradation by 75.3 % and 77.7 %, and significantly shifted microbial community structure. Furthermore, kaolin caused a positive association between Actinobacteria and sweetener degradation. Taken together, kaolin effectively inhibited nitrogen loss and promoted the degradation of ACE and SUC during the SS composting, which is of great significance for the removal of emerging organic pollutants in SS.

Bacterial and fungal communities regulated directly and indirectly by tobacco-rape rotation promote tobacco production.

Tobacco continuous cropping is prevalent in intensive tobacco agriculture but often leads to microbial community imbalance, soil nutrient deficiency, and decreased crop productivity. While the tobacco-rape rotation has demonstrated significant benefits in increasing tobacco yield. Microorganisms play a crucial role in soil nutrient cycling and crop productivity. However, the internal mechanism of tobacco-rape rotation affecting tobacco yield through microbe-soil interaction is still unclear. In this study, two treatments, tobacco continuous cropping (TC) and tobacco-rape rotation (TR) were used to investigate how planting systems affect soil microbial diversity and community structure, and whether these changes subsequently affect crop yields. The results showed that compared with TC, TR significantly increased the Shannon index, Chao1 index, ACE index of bacteria and fungi, indicating increased microbial α-diversity. On the one hand, TR may directly affect the bacterial and fungal community structure due to the specificity of root morphology and root exudates in rape. Compared with TC, TR significantly increased the proportion of beneficial bacterial and fungal taxa while significantly reduced soil-borne pathogens. Additionally, TR enhanced the scale and complexity of microbial co-occurrence networks, promoting potential synergies between bacterial OTUs. On the other hand, TR indirectly changed microbial community composition by improving soil chemical properties and changing microbial life history strategies. Compared with TC, TR significantly increased the relative abundance of copiotrophs while reduced oligotrophs. Notably, TR significantly increased tobacco yield by 39.6% compared with TC. The relationships among yield, microbial community and soil chemical properties indicated that planting systems had the greatest total effect on tobacco yield, and the microbial community, particularly bacteria, had the greatest direct effect on tobacco yield. Our findings highlighted the potential of tobacco-rape rotation to increase yield by both directly and indirectly optimizing microbial community structure.

Genetically modified indigenous Pseudomonas aeruginosa drove bacterial community to change positively toward microbial enhanced oil recovery applications.

AIMS: Microbial enhanced oil recovery (MEOR) is cost-effective and eco-friendly for oil exploitation. Genetically modified biosurfactants-producing high-yield strains are promising for ex-situ MEOR. However, can they survive and produce biosurfactants in petroleum reservoirs for in-situ MEOR? What is their effect on the native bacterial community? METHODS AND RESULTS: A genetically modified indigenous biosurfactants-producing strain Pseudomonas aeruginosa PrhlAB was bioaugmented in simulated reservoir environments. P. aeruginosa PrhlAB could stably colonize in simulated reservoirs. Biosurfactants (200 mg L-1) were produced in simulated reservoirs after bio-augmenting strain PrhlAB. The surface tension of fluid was reduced to 32.1 mN m-1. Crude oil was emulsified with an emulsification index of 60.1%. Bio-augmenting strain PrhlAB stimulated the MEOR-related microbial activities. Hydrocarbons-degrading bacteria and biosurfactants-producing bacteria were activated, while the hydrogen sulfide producing bacteria were inhibited. Bio-augmenting P. aeruginosa PrhlAB reduced the diversity of bacterial community, and gradually simplified the species composition. Bacteria with oil displacement potential became dominant genera, such as Shewanella, Pseudomonas and Arcobacter. CONCLUSIONS: Culture-based and sequence-based analysis reveal that genetically modified biosurfactants-producing strain P. aeruginosa PrhlAB are promising for in-situ MEOR as well.

Nano- and Microplastics Increase the Occurrence of Bacterial Wilt in Tomato (Solanum lycopersicum L.).

Concern over nano- and microplastic contamination of terrestrial ecosystems has been increasing. However, little is known about the effect of nano- and microplastics on the response of terrestrial ecosystems already under biotic stress. Here, nano- and microplastics at 150-500 mg·kg-1 were exposed to tomatoes (Solanum lycopersicum L.), and the results demonstrate that the presence of nano- and microplastics increased the occurrence of bacterial wilt caused by Ralstonia solanacearum in tomatoes as a function of contaminant concentration, surface modification, and size. Our work shows that nanoplastics (30 nm, 250 mg·kg-1) increased the disease incidence by 2.19-fold. The disease severities in amino- and carboxyl-modified nanoplastic treatments were 30.4 and 21.7% higher than that in unmodified nanoplastic treatment, respectively. The severity of disease under the influence of different-sized nano- and microplastic treatments followed the order 30 > 100 nm > 1 > 50 µm. Mechanistically, nanoplastics disrupted the structure of the tomato rhizosphere soil bacterial community and suppressed the induced systemic resistance in tomato; nanoplastics in planta decreased the salicylic acid and jasmonic acid content in tomatoes, thus inhibiting systemic acquired resistance; and microplastics increased the soil water retention, leading to increased pathogen abundance in the rhizosphere. Additionally, the leachates from nano- and microplastics had no effect on disease occurrence or the growth of tomatoes. Our findings highlight a potential risk of nano- and microplastic contamination to agriculture sustainability and food security.

The effect of different amendments on Cd availability and bacterial community after three-year consecutive application in Cd-contaminated paddy soils.

In situ immobilization is a widely used measure for passivating Cd-contaminated soils. Amendments need to be continuously applied to achieve stable remediation effects. However, few studies have evaluated the impact of consecutive application of amendments on soil health and the microecological environment. A field experiment was conducted in a Cd-contaminated paddy (available Cd concentration 0.40 mg kg-1) on the Chengdu Plain to investigate the changes in soil Cd availability and response characteristics of soil bacterial communities after consecutive application of rice straw biochar (SW), fly ash (FM) and marble powder (YH) amendments from 2018 to 2020. Compared with control treatment without amendments (CK), soil pH increased by 0.6, 0.5 and 1.5 under SW, FM and YH amendments, respectively, and the soil available Cd concentration decreased by 10.71%, 21.42% and 25.00%, respectively. The Cd concentration in rice grain was less than 0.2 mg kg-1 under YH amendment, which was within the Chinese Contaminant Limit in Food of National Food Safety Standards (GB2762-2022) in the second and third years. The three amendments had different effects on the transformation of Cd fractions in soil, which may be relevant to the specific bacterial communities shaped under different treatments. The proportion of Fe-Mn oxide-bound fraction Cd (OX-Cd) increased by 11% under YH treatment, which may be due to the promotion of Fe(III) and Cd binding by some enriched iron-oxidizing bacteria, such as Lysobacter, uncultured_Pelobacter sp. and Sulfurifusis. Candidatus_Tenderia and Sideroxydans were enriched under SW and FM amendments, respectively, and were likely beneficial for reducing Cd availability in soil through Cd immobilization. These results revealed the significance of the bacterial community in soil Cd immobilization after consecutive application of amendments and highlighted the potential of applying YH amendment to ensure the safe production of rice in Cd-contaminated soil.

Performance of Halo-Alkali-Tolerant Endophytic Bacteria on Hybrid Pennisetum and Bacterial Community under Varying Soil Conditions.

Halo-alkali soil threatens agriculture, reducing growth and crop yield worldwide. In this study, physicochemical and molecular techniques were employed to explore the potential of halo-alkali-tolerant endophytic bacteria strains Sphingomonas sp. pp01, Bacillus sp. pp02, Pantoea sp. pp04, and Enterobacter sp. pp06 to enhance the growth of hybrid Pennisetum under varying saline conditions. The strains exhibited tolerance to high salt concentrations, alkaline pH, and high temperatures. Under controlled conditions, all four strains showed significant growth-promoting effects on hybrid Pennisetum inoculated individually or in combination. However, the effects were significantly reduced in coastal saline soil. The best growth-promoting effect was achieved under greenhouse conditions, increasing shoot fresh and dry weights of hybrid Pennisetum by up to 457.7% and 374.7%, respectively, using irrigating trials. Metagenomic sequencing analysis revealed that the diversity and composition of rhizosphere microbiota underwent significant changes after inoculation with endophytic bacteria. Specifically, pp02 and co-inoculation significantly increased the Dyella and Pseudomonas population. Firmicutes, Mycobacteria, and Proteobacteria phyla were enriched in Bacillus PP02 samples. These may explain the best growth-promoting effects of pp02 and co-inoculation on hybrid Pennisetum under greenhouse conditions. Our findings reveal the performance of endophytic bacterial inoculants in enhancing beneficial microbiota, salt stress tolerance, and hybrid Pennisetum growth.

Assessing Antibiotic-Resistant Genes in University Dormitory Washing Machines.

University dormitories represent densely populated environments, and washing machines are potential sites for the spread of bacteria and microbes. However, the extent of antibiotic resistance gene (ARG) variation in washing machines within university dormitories and their potential health risks are largely unknown. To disclose the occurrence of ARGs and antibiotic-resistant bacteria from university dormitories, we collected samples from washing machines in 10 dormitories and used metagenomic sequencing technology to determine microbial and ARG abundance. Our results showed abundant microbial diversity, with Proteobacteria being the dominant microorganism that harbors many ARGs. The majority of the existing ARGs were associated with antibiotic target alteration and efflux, conferring multidrug resistance. We identified tnpA and IS91 as the most abundant mobile genetic elements (MGEs) in washing machines and found that Micavibrio aeruginosavorus, Aquincola tertiaricarbonis, and Mycolicibacterium iranicum had high levels of ARGs. Our study highlights the potential transmission of pathogens from washing machines to humans and the surrounding environment. Pollution in washing machines poses a severe threat to public health and demands attention. Therefore, it is crucial to explore effective methods for reducing the reproduction of multidrug resistance.

Comparative Analysis of Bacterial Information of Biofilms and Activated Sludge in Full-Scale MBBR-IFAS Systems.

This study extensively analyzed the bacterial information of biofilms and activated sludge in oxic reactors of full-scale moving bed biofilm reactor-integrated fixed-film activated sludge (MBBR-IFAS) systems. The bacterial communities of biofilms and activated sludge differed statistically (R = 0.624, p < 0.01). The denitrifying genera Ignavibacterium, Phaeodactylibacter, Terrimonas, and Arcobacter were more abundant in activated sludge (p < 0.05), while comammox Nitrospira was more abundant in biofilms (p < 0.05), with an average relative abundance of 8.13%. Nitrospira and Nitrosomonas had weak co-occurrence relationships with other genera in the MBBR-IFAS systems. Potential function analysis revealed no differences in pathways at levels 1 and 2 based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) between biofilms and activated sludge. However, in terms of pathways at level 3, biofilms had more potential in 26 pathways, including various organic biodegradation and membrane and signal transportation pathways. In comparison, activated sludge had more potential in only five pathways, including glycan biosynthesis and metabolism. With respect to nitrogen metabolism, biofilms had greater potential for nitrification (ammonia oxidation) (M00528), and complete nitrification (comammox) (M00804) concretely accounted for methane/ammonia monooxygenase (K10944, K10945, and K10946) and hydroxylamine dehydrogenase (K10535). This study provides a theoretical basis for MBBR-IFAS systems from the perspective of microorganisms.

Epiphytic Bacterial Community Analysis of Ulva prolifera in Garorim and Muan Bays, Republic of Korea.

The bacterial communities related to seaweed can vary considerably across different locations, and these variations influence the seaweed's nutrition, growth, and development. To study this further, we evaluated the bacteria found on the green marine seaweed Ulva prolifera from Garorim Bay and Muan Bay, two key locations on Republic of Korea's west coast. Our analysis found notable differences in the bacterial communities between the two locations. Garorim Bay hosted a more diverse bacterial population, with the highest number of ASVs (871) compared to Muan Bay's 156 ASVs. In Muan Bay, more than 50% of the bacterial community was dominated by Pseudomonadota. On the other hand, Garorim Bay had a more balanced distribution between Bacteroidota and Pseudomonadota (37% and 35.5%, respectively). Additionally, Cyanobacteria, particularly Cyanothece aeruginosa, were found in significant numbers in Garorim Bay, making up 8% of the community. Mineral analysis indicated that Garorim Bay had higher levels of S, Na, Mg, Ca, and Fe. Function-wise, both locations exhibited bacterial enrichment in amino acid production, nucleosides, and nucleotide pathways. In conclusion, this study broadens our understanding of the bacterial communities associated with Ulva prolifera in Korean waters and provides a foundation for future research on the relationships between U. prolifera and its bacteria.

Soil Parameters and Forest Structure Commonly Form the Microbiome Composition and Activity of Topsoil Layers in Planted Forests.

Soil bacterial communities play a remarkable role in nutrient cycling, significantly affecting soil organic material content, soil fertility, and, in an indirect way, plant succession processes. Conversely, vegetation type influences microbial soil life. The present study compared the bacterial microbiome composition, diversity and catabolic activity profile of topsoil samples collected under three different forest types (a twice-coppiced black locust stand, a young, naturally reforested, and a middle-aged mixed pedunculate oak stand) planted on former arable land in the early 20th century. Diversity indices determined during 16S ribosomal RNA sequencing-based metagenome analysis indicated that the black locust stand had the highest soil bacterial community diversity. At the phylum level, Acidobacteriota, Actinobacteriota, Proteobacteria, Verrucomicrobiota, Bacteroidota, and Gemmatimonadota were the most abundant taxa in the forest soils. Concerning soil parameters, redundancy analysis revealed that pH had the highest impact on bacterial community structure and pH, and soil organic carbon content on the samples' respiration patterns. As for catabolic activity, the recently clearcut oak forest showed the lowest substrate-induced respiration, and citrate was the main driver for the inter-stand variability of microbial activity. Our results confirm that soil parameters and forest type influence the composition and functioning of the soil bacterial microbiome.

Macrogenomics-Based Analysis of the Effects of Intercropped Soybean Photosynthetic Characteristics and Nitrogen-Assimilating Enzyme Activities on Yield at Different Nitrogen Levels.

Currently, China's soybean self-sufficiency rate is only 15%, highlighting the soybean crisis and the supply chain risks that pose a major threat to China's food security. Thus, it has become imperative to step up efforts to boost soybean production capacity while promoting the green and sustainable development of regional farmland ecosystems. In this context, the present study comprehensively investigated the effects of intercropping and nitrogen application rate on soybean yield, as well as the changes in gradients generated by different levels of nitrogen application. Based on six consecutive years of maize-soybean intercropping planting patterns, the inter-root soils of soybeans were collected at the flowering stage and evaluated for soil nitrogen content, nitrogen-assimilating enzyme activities, and microbial community composition of soybean, which were correlated with yield, to clarify the main pathways and modes of intercropping effects. The N2 level (80 kg·ha-1) was favourable for higher yield. In comparison to monocropping, the intercropping reduced yield by 9.65-13.01%, photosynthetic characteristics by 1.33-7.31%, and plant nitrogen-assimilating enzyme activities by 8.08-32.01% at the same level of N application. Likewise, soil urease and catalase activities were reduced by 9.22 and 1.80%, while soil nitrogen content declined by an average of 6.38%. Gemmatimonas and Bradyrhizobium enrichment significantly increased soil nitrogen content, photosynthetic characteristics, and soybean yield, while it was reduced by Candidatus_Udaeobacter and Candidatus_Solibacte enrichment. The results of this study provide a theoretical basis for further optimising maize-soybean intercropping, which is crucial for enhancing the agricultural production structure and improving the overall soybean production capacity.

Bacterial Spermosphere Inoculants Alter N. benthamiana-Plant Physiology and Host Bacterial Microbiome.

In this study, we investigated the interplay between the spermosphere inoculum, host plant physiology, and endophytic compartment (EC) microbial community. Using 16S ribosomal RNA gene sequencing of root, stem, and leaf endophytic compartment communities, we established a baseline microbiome for Nicotiana sp. Phenotypic differences were observed due to the addition of some bacterial inoculants, correlated with endogenous auxin loads using transgenic plants expressing the auxin reporter pB-GFP::P87. When applied as spermosphere inoculants, select bacteria were found to create reproducible variation within the root EC microbiome and, more systematically, the host plant physiology. Our findings support the assertion that the spermosphere of plants is a zone that can influence the EC microbiome when applied in a greenhouse setting.

Metagenomic insights into effects of carbon/nitrogen ratio on microbial community and antibiotic resistance in moving bed biofilm reactor.

This study investigated the effects of carbon/nitrogen (C/N) ratio on microbial community in moving bed biofilm reactor (MBBR) using metagenomic analysis, and the dynamic changes of relevant antibiotic resistance genes (ARGs) were also analyzed. The results showed that under low C/N ratio, MBBR exhibited average removal rates of 98.41 % for ammonia nitrogen and 75.79 % for total nitrogen. Metagenomic analysis showed low C/N ratio altered the structure of biofilm and water microbiota, resulting in the detachment of bacteria such as Actinobacteria from biofilm into water. Furthermore, sulfamethazine (SMZ)-resistant bacteria and related ARGs were released into water under low C/N ratio, which lead to the increase of SMZ resistance rate to 90%. Moreover, most dominant genera are potential hosts for both nitrogen cycle related genes and ARGs. Specifically, Nitrosomonas that carried gene sul2 might be released from biofilm into water. These findings implied the risks of antibiotic resistance dissemination in MBBR under low C/N ratio.

Impacts of multiple environmental factors on soil bacterial community assembly in heavy metal polluted paddy fields.

Soil microorganisms play pivotal roles in driving essential biogeochemical processes in terrestrial ecosystems, and they are sensitive to heavy metal pollution. However, our understanding of multiple environmental factors interaction in heavy metal polluted paddy fields to shape microbial community assembly remain limited. In the current study, we used 16S rRNA amplicon sequencing to characterize the microbial community composition in paddy soils collected from a typical industry town in Taihu region, eastern China. The results revealed that Cd and Pb were the major pollutant, and Proteobacteria, Acidobacteria and Chloroflexi were the dominate indigenous bacterial phyla. Linear regression and random forest analysis demonstrated that soil pH was the most important predictor of bacterial diversity. Mantel analysis showed that bacterial community structure was mainly driven by pH, CEC, silt, sand, AK, total Cd and DTPA-Cd. The constructed bacterial co-occurrence network, utilizing a random matrix theory-based approach, exhibited non-random with scale-free and modularity features. The major modules within the networks also showed significant correlations with soil pH. Overall, our study indicated that soil physiochemical properties made predominant contribution to bacterial community diversity, structure and their association in Cd/Pb polluted paddy fields. These findings expand our knowledge of the key environmental drivers and co-occurrence patterns of bacterial community in polluted paddy fields.

Bacterial communities varied in different Coccinella transversoguttata populations located in Tibetan plateau.

Coccinella transversoguttata is an important predatory beetle in Asia and America. Currently, few studies have investigated C. transversoguttata in China especially in the Tibetan plateau. In this study, full-length 16 s rRNA sequencing and qPCR experiment were performed on eight C. transversoguttata populations collected from Tibet to analyze their bacterial communities and bacteria abundance. In summary, our results revealed the microbial compositions, diversities and bacterial titers in the bacterial communities in C. transversoguttata populations in the Tibetan plateau. In future, there is a need to explore the differences in microbiota among various C. transversoguttata populations collected from different locations. These results add to our understanding of the complex bacterial communities of C. transversoguttata and their utilization as potential biocontrol factors.

A metagenomic assessment of bacterial community in spices sold open-air markets in Saint-Louis, Senegal.

Natural spices play an essential role in human nutrition and well-being. However, their processing on different scales can expose them to potential sources of contamination. This study aimed to describe the bacterial community genomic footprint in spices sold in Senegal. Spice samples were collected in August 2022 in Saint-Louis, Senegal. The genomic region coding bacterial 16S rRNA was then amplified and sequenced using Oxford Nanopore Technology (ONT). Sequencing was carried out on two batches of samples, one containing part of the "Local Spices or Herbs" (n = 10), and the other, a mixture of 7 spices, Curcuma, Thyme and the other part of the "Local Spices or Herbs" (n = 39). Results showed high bacterial diversity and the predominance of Escherichia coli and Salmonella enterica in samples, with total reads of 65,744 and 165,325 for the two batches, respectively. The sample category "Homemade mixture of food condiments ", which includes all "Local Spices or Herbs" samples, showed remarkable bacterial diversity. These were followed by Curcuma, a blend of 7 spices and thyme. Also, the different categories of spices studied show similarities in their bacterial composition. These results highlight the microbial community's highly diverse genomic profile, including pathogenic bacteria, in spice samples.

Fire-Induced Changes in Soil Properties and Bacterial Communities in Rotational Shifting Cultivation Fields in Northern Thailand.

Fire is a common practice in rotational shifting cultivation (RSC), but little is known about the dynamics of bacterial populations and the impact of fire disturbance in northern Thailand. To fill the research gap, this study aims to investigate the dynamics of soil bacterial communities and examine how the soil's physicochemical properties influence the bacterial communities in RSC fields over a period of one year following a fire. Surface soil samples (0-2 cm depth) were collected from sites with 6 (RSC-6Y) and 12 (RSC-12Y) years of fallow in Chiang Mai Province, northern Thailand at six different time points: before burning, 5 min after burning (summer), 3 months after burning (rainy season), 6 months after burning (rainy season), 9 months after burning (winter), and 12 months after burning (summer). The results revealed a reduction in the soil bacterial communities' diversity and an increase in soil nutrient levels immediately after the fire. The fire significantly influenced the abundance of Firmicutes, Proteobacteria, Acidobacteria, and Planctomycetes, but not that of Actinobacteria. At the genus level, Bacillus, Conexibacter, and Chthoniobacter showed increased abundance following the fire. During the rainy season, a recovery in the abundance of the soil bacterial communities was observed, although soil nutrient availability declined. Soil physicochemical properties such as pH, organic matter, organic carbon, electrical conductivity, cation exchange capacity, nitrate-nitrogen, available phosphorus, exchangeable potassium, total nitrogen, bulk density, sand, and silt contents significantly influenced the composition of bacterial communities. Alpha diversity indices indicated a decrease in diversity immediately after burning, followed by an increase from the early rainy season until the summer season, indicating that seasonal variation affected the composition of the soil bacterial communities. After one year of burning, an increase in bacterial richness was observed, while the diversity of the bacterial communities reverted to pre-burning levels.

Variations in different preceding crops on the soil environment, bacterial community richness and diversity of tobacco-planting soil.

Tobacco (Nicotiana tabacum L.) is a major cash crop, and soil quality played a significant role in the yield and quality of tobacco. Most farmers cultivate tobacco in rotation with other crops to improve the soil characteristics. However, the effects of different previous crops on the soil's nutrient status and bacterial community for tobacco cultivation still need to be determined. Three treatments were assessed in this study, i.e., tobacco-planting soil without treatment (CK), soil with barley previously cultivated (T1), and soil with rapeseed previously cultivated (T2). The soil physical and chemical properties and the 16S rRNA gene sequence diversity of the bacterial community were analyzed. The effects of different crops on the physical and chemical properties of tobacco-planting soil and the diversity and richness of the bacterial community were comprehensively discussed. The results of this study showed that different previously cultivated crops altered the nutrient status of the soil, with changes in the ratio of NH4 +-N to NO3 --N having the most significant impact on tobacco. In CK, the ratio of NH4 +-N to NO3 --N was 1:24.2, T1-1:9.59, and T2-1:11.10. The composition of the bacterial community in tobacco-planting soil varied significantly depending on the previously cultivated crops. The richness and diversity of the bacterial community with different crops were considerably higher than without prior cultivation of different crops. The dominant bacteria in different treatments were Actinobacteriota, Proteobacteria, and Chloroflexi with their relative abundance differed. In conclusion, our study revealed significant differences in nutrient status, bacterial community diversity, and the richness of tobacco-planting soil after the preceding cultivation of different crops. Suitable crops should be selected to be previously cultivated in tobacco crop rotations in near future for sustainable agriculture.

Investigation of the marine bacterial community along the coastline of the Gulf of Thailand.

The Gulf of Thailand provides many services to the Thai population, and human activities may influence the diversity of microorganisms in the seawater. Information of the microorganisms' profile which inhabit the coastline can be used to monitor the water quality. This study aimed to investigate the bacterial community in the waters along the coastline provinces, including Rayong, Chonburi, Prachuap Kiri Khan, and Nakhon Sri Thammarat. Seawater samples were collected at each site, and the conductivity, pH, salinity, temperature, and turbidity were measured. The samples were subjected to whole DNA extraction, 16S rRNA amplification, next-generation sequencing, and statistical analysis to identify the bacterial diversity and analyse the effects of water parameters on the bacterial community. The dominant bacterial phyla found were Proteobacteria, Bacteroidota, and Cyanobacteria. Spearman rank correlation analysis revealed a high correlation of Pseudoalteromonas, the NS5 marine group, Lachnospiraceae, Marinobacterium, Mariviven, and Vibrio with the seawater parameters. The predatory bacteria Peredibacter and Halobacteriovorax were reported among these bacterial communities for the first time in the Gulf of Thailand. Interestingly, Akkermansia, a novel candidate for next-generation probiotics to improve human health, was also found in the sample from Nakhon Sri Thammarat Province. Although the rich-ness and diversity of the bacterial communities differed among sampling sites, it is a possible source of many valuable bacteria for future use.