Effect of Heavy Metals Pollution on Soil Microbial Diversity and Bermudagrass Genetic Variation

Heavy metal pollution is a serious global environmental problem as it adversely affects plant growth and genetic variation. It also alters the composition and activity of soil microbial communities. The objectives of this study were to determine the soil microbial diversity, bermudagrass genetic variation in Cd contaminated or uncontaminated soils from Hunan province of China, and to evaluate Cd-tolerance of bermudagrass at different soils. The Biolog method, hydroponic experiments and simple sequence repeat markers were used to assess the functional diversity of microorganisms, Cd-tolerance and the genetic diversity of bermudagrass, respectively. Four of the sampling sites were heavily contaminated with heavy metals. The total bioactivity, richness, and microbial diversity decreased with increasing concentration of heavy metal. The hydroponic experiment revealed that bermudagrass populations collected from polluted sites have evolved, encompassing the feature of a higher resistance to Cd toxicity. Higher genetic diversity was observed to be more in contaminated populations than in uncontaminated populations. Heavy metal pollution can result in adverse effects on plant growth, soil microbial diversity and activity, and apparently has a stronger impact on the genetic structure. The results of this study provide new insights and a background to produce a genetic description of populations in a species that is suitable for use in phytoremediation practices.

Intercropping With Turmeric or Ginger Reduce the Continuous Cropping Obstacles That Affect Pogostemon cablin (Patchouli)

Continuous cropping (CC) restricts the development of the medicinal plant cultivation industry because it alters soil properties and the soil microbial micro-ecological environment. It can also lead to reductions in the chemical contents of medicinal plants. In this study, we intercropped continuously cropped Pogostemon cablin (patchouli) with turmeric or ginger. High-throughput sequencing was used to study the soil bacteria and fungi. Community composition, diversity, colony structure, and colony differences were also analyzed. A redundancy analysis (RDA) was used to study the interactions between soil physical and chemical factors, and the bacteria and fungi. The correlations between the soil community and the soil physical and chemical properties were also investigated. The results showed that intercropping turmeric and ginger with patchouli can improve soil microbial abundance, diversity, and community structure by boosting the number of dominant bacteria, and by improving soil bacterial metabolism and the activities of soil enzymes. They also modify the soil physical and chemical properties through changes in enzyme activity, soil pH, and soil exchangeable Ca (Ca). In summary, turmeric and ginger affect the distribution of dominant bacteria, and increase the contents of the active ingredient in patchouli. The results from this study suggested that the problems associated with continuously cropping patchouli can be ameliorated by intercropping it with turmeric and ginger.

Analysis of Microorganism Diversity in Haemaphysalis longicornis From Shaanxi, China, Based on Metagenomic Sequencing

Ticks are dangerous ectoparasites of humans and animals, as they are important disease vectors and serve as hosts for various microorganisms (including a variety of pathogenic microorganisms). Diverse microbial populations coexist within the tick body. Metagenomic next-generation sequencing (mNGS) has been suggested to be useful for rapidly and accurately obtaining microorganism abundance and diversity data. In this study, we performed mNGS to analyze the microbial diversity of Haemaphysalis longicornis from Baoji, Shaanxi, China, with the Illumina HiSeq platform. We identified 189 microbial genera (and 284 species) from ticks in the region; the identified taxa included Anaplasma spp., Rickettsia spp., Ehrlichia spp., and other important tick-borne pathogens at the genus level as well as symbiotic microorganisms such as Wolbachia spp., and Candidatus Entotheonella. The results of this study provide insights into possible tick-borne diseases and reveal new tick-borne pathogens in this region. Additionally, valuable information for the biological control of ticks is provided. In conclusion, this study provides reference data for guiding the development of prevention and control strategies targeting ticks and tick-borne diseases in the region, which can improve the effectiveness of tick and tick-borne disease control.

Diversity and Co-Occurrence Patterns of Fungal and Bacterial Communities from Alkaline Sediments and Water of Julong High-Altitude Hot Springs at Tianchi Volcano, Northeast China

The Julong high-altitude volcanic hot springs in northeast China are of undeniable interest for microbiological studies due to their unique, extreme environmental conditions. The objective of this study was to provide a comprehensive analysis of the unexplored fungal and bacterial community composition, structure and networks in sediments and water from the Julong hot springs using a combination of culture-based methods and metabarcoding. A total of 65 fungal and 21 bacterial strains were isolated. Fungal genera Trichoderma and Cladosporium were dominant in sediments, while the most abundant fungi in hot spring water were Aspergillus and Alternaria. Bacterial communities in sediments and water were dominated by the genera Chryseobacterium and Pseudomonas, respectively. Metabarcoding analysis revealed significant differences in the microorganism communities from the two hot springs. Results suggested a strong influence of pH on the analyzed microbial diversity, at least when the environmental conditions became clearly alkaline. Our analyses indicated that mutualistic interactions may play an essential role in shaping stable microbial networks in the studied hot springs. The much more complicated bacterial than fungal networks described in our study may suggest that the more flexible trophic strategies of bacteria are beneficial for their survival and fitness under extreme conditions.

Gelatin-Tea Tree Essential Oil Coating Improves the Quality, Flavor, and Micromolecular Metabolites of Squid (Illex argentinus) Muscle During Cold Storage

Squid muscle is delicious and nutritious, but it is highly susceptible to spoilage, severely limiting its market development. This study comprehensively evaluated the effects of gelatin (Gel), essential oil (Ess), and Gel + Ess coating on the quality, flavor, and microorganisms of squid muscle during refrigerated storage (4 °C). The results showed that squid muscle treated with Gel + Ess exhibited higher water-holding capacity and sensory evaluation, but lower pH value, chromaticity, and texture parameters than those treated with sterile water (control) during cold storage. The total volatile basic nitrogen (TVB-N) result demonstrated that the shelf life of squid muscle treated with Gel + Ess coating was extended to 12 days at 4 °C, longer than the control group. The Gel + Ess group had the best inhibitory effect on aldehydes and ketones in refrigerated squid muscle, and it could effectively maintain the flavor quality. In addition, the Gel + Ess coating showed an additive inhibition on the growth of Cockerella and Shiwanella compared to the individual compounds. The Gel + Ess coating is a novel strategy for improving the quality, flavor, and micromolecular metabolites of squid muscle during cold storage.

Microfluidic droplets with amended culture media cultivate a greater diversity of soil microorganisms

Uncultivated but abundant soil microorganisms have untapped potential for producing broad ranges of natural products, as well as for bioremediation. However, cultivating soil microorganisms while maintaining a broad microorganism diversity to enable phenotyping and functional analysis of as diverse individual isolates as possible remains challenging. In this study, we developed and tested the ability of several culture media formulations that contain defined soil metabolites or soil extracts to maintain microorganism diversity during culture. We also assessed their performance in microfluidic droplet cultivation where single-soil microorganism isolates were encapsulated and cultivated in picoliter-volume water-in-oil emulsion droplets to enable clonal growth needed for downstream functional analyses. Our results show that droplet cultivation with media supplemented by soil extract or soil metabolites enables the recovery of soil microorganisms with higher diversity (up to 1.5-fold higher richness) compared to bulk cultivation methods. Importantly, 1.7-fold more of less abundant (<1%) phyla and 11-fold more of unique genera were recovered, demonstrating the utility of this method for interrogating highly diverse soil microorganisms for broad ranges of applications.IMPORTANCEAlthough soil microorganisms hold a significant value in bioproduction and bioremediation, only a small fraction-less than 1%-can be cultured under specific media and cultivation conditions. This indicates that there are ample opportunities in harvesting the diverse environmental microorganisms if isolating and recovering these uncultured microorganisms are possible. This paper presents a new cultivation technique composed of isolating single-soil microorganism cell from an in situ soil microorganism community in microfluidic droplets and conducting in-droplet cultivation in media supplemented by soil extract or soil metabolites. This method enables the recovery of a broader diversity of the original microorganism community, laying the groundwork for a high-throughput phenotyping of these diverse microorganisms from their natural habitats.

Insights into accumulation of active ingredients and rhizosphere microorganisms between Salvia miltiorrhiza and S. castanea

Salvia miltiorrhiza is an important traditional herbal medicine, and its extracts could be used for treating cardiovascular disease. Although these medicinal compounds are functionally similar, their wild relative, S. castanea, produces significantly different concentrations of these compounds. The reason for their differences is still unknown. In a series of soil and plant-based analyses, we explored and compared the rhizosphere microbiome of S. miltiorrhiza and S. castanea. To further investigate the geographical distribution of S. castanea, MaxEnt models were used to predict the future suitable habitat areas of S. castanea in China. Results revealed the distributions and structure of the rhizosphere microbial community of S. miltiorrhiza and S. castanea at different times. In addition, differences in altitude and soil moisture resulting from changes in climate and geographical location are also critical environmental factors in the distribution of S. castanea. The findings of this study increase our understanding of plant adaptation to their geographical environment through secondary metabolites. It also highlights the complex interplay between rhizospheric factors and plant metabolism, which provides the theoretical basis for the cultivation of S. miltiorrhiza and the use of S. castanea resources.