Thermotogota diversity and distribution patterns revealed in Auka and JaichMaa 'ja 'ag hydrothermal vent fields in the Pescadero Basin, Gulf of California.

Discovering new deep hydrothermal vent systems is one of the biggest challenges in ocean exploration. They are a unique window to elucidate the physical, geochemical, and biological processes that occur on the seafloor and are involved in the evolution of life on Earth. In this study, we present a molecular analysis of the microbial composition within the newly discovered hydrothermal vent field, JaichMaa 'ja 'ag, situated in the Southern Pescadero Basin within the Gulf of California. During the cruise expedition FK181031 in 2018, 33 sediment cores were collected from various sites within the Pescadero vent fields and processed for 16S rRNA amplicon sequence variants (ASVs) and geochemical analysis. Correlative analysis of the chemical composition of hydrothermal pore fluids and microbial abundances identified several sediment-associated phyla, including Thermotogota, that appear to be enriched in sediment horizons impacted by hydrothermal fluid flow. Comparative analysis of Thermotogota with the previously explored Auka hydrothermal vent field situated 2 km away displayed broad similarity between the two locations, although at finer scales (e.g., ASV level), there were notable differences that point to core-to-core and site-level factors revealing distinct patterns of distribution and abundance within these two sediment-hosted hydrothermal vent fields. These patterns are intricately linked to the specific physical and geochemical conditions defining each vent, illuminating the complexity of this unique deep ocean chemosynthetic ecosystem.

The "Dry-Lab" Side of Food Authentication: Benchmark of Bioinformatic Pipelines for the Analysis of Metabarcoding Data.

Next Generation Sequencing Technologies (NGS), particularly metabarcoding, are valuable tools for authenticating foodstuffs and detecting eventual fraudulent practices such as species substitution. This technique, mostly used for the analysis of prokaryotes in several environments (including food), is in fact increasingly applied to identify eukaryotes (e.g., fish, mammals, avian, etc.) in multispecies food products. Besides the "wet-lab" procedures (e.g., DNA extraction, PCR, amplicon purification, etc.), the metabarcoding workflow includes a final "dry-lab" phase in which sequencing data are analyzed using a bioinformatic pipeline (BP). BPs play a crucial role in the accuracy, reliability, and interpretability of the metabarcoding results. Choosing the most suitable BP for the analysis of metabarcoding data could be challenging because it might require greater informatics skills than those needed in standard molecular analysis. To date, studies comparing BPs for metabarcoding data analysis in foodstuff authentication are scarce. In this study, we compared the data obtained from two previous studies in which fish burgers and insect-based products were authenticated using a customizable, ASV-based, and command-line interface BP (BP1) by analyzing the same data with a customizable but OTU-based and graphical user interface BP (BP2). The final sample compositions were compared statistically. No significant difference in sample compositions was highlighted by applying BP1 and BP2. However, BP1 was considered as more user-friendly than BP2 with respect to data analysis streamlining, cost of analysis, and computational time consumption. This study can provide useful information for researchers approaching the bioinformatic analysis of metabarcoding data for the first time. In the field of food authentication, an effective and efficient use of BPs could be especially useful in the context of official controls performed by the Competent Authorities and companies' self-control in order to detect species substitution and counterfeit frauds.

Metagenomic analysis of endophytic bacteria in seed potato (Solanum tuberosum).

To date, the association of potato tuber microbiota is poorly understood. In this study, the endophytic bacterial flora of seed potato tubers was identified and the diversity of healthy and unhealthy tubers was compared. Metagenomic DNA extracted from healthy and unhealthy samples of seed potato tubers was used for the analysis of microbial communities. Next generation sequencing of the ∼460 bp v3-v4 region of the 16S rRNA gene was carried out using the Illumina Miseq platform. The data were analysed using the Divisive Amplicon Denoising Algorithm 2 pipeline. Sequence analysis of the potato metagenome identified amplicon sequence variants (ASVs) assigned to 745 different taxa belonging to eight Phyla: Firmicutes (46.2%), Proteobacteria (36.9%), Bacteroidetes (1.8%), Actinobacteria (0.1%), Tenericutes (0.005%), Saccharibacteria (0.003%), Verrucomicrobiota (0.003%), and Acidobacteria (0.001%). In healthy seed potato tubers, 55-99% of ASVs belonged to Firmicutes, including Bacillus, Salinibacillus, Staphylococcus, Lysinibacillus, Paenibacillus, and Brevibacillus genera within the taxonomic order Bacillales. However, in the visually unhealthy tubers, only 0.5-3.9% of ASVs belonged to Firmicutes while 84.1-97% of ASVs belonged to Proteobacteria. This study highlights that diverse bacterial communities colonize potato tubers, which contributes to the understanding of plant-microbe interactions and underscores the significance of metagenomic approaches in agricultural research.

The first ITS1 profiling of honey samples from the Southeast Asian region Lombok, Bali and Banggi Island.

Southern Asian flowers offer honeybees a diversity of nectar. Based on its geographical origin, honey quality varies. Traditional methods are less authentic than DNA-based identification. The origin of honey is determined by pollen, polyphenolic, and macro-microorganisms. In this study, amplicon sequencing targets macro-microorganisms in eDNA using the ITS1 region to explore honey's geographical location and authentication. The variety of honey samples was investigated using ITS1 with Illumina sequencing. For all four honey samples, raw sequence reads showed 979,380 raw ITS1 amplicon reads and 375 ASVs up to the phylum level. The highest total number of 202 ASVs up to phylum level identified Bali honey with 211,189 reads, followed by Banggi honey with 309,207 a total number of 111 ASVs, and Lombok represents only 63 ASVs up to phylum level with several read 458,984. Based on Shannon and Chao1, honey samples from Bali (B2) and (B3) exhibited higher diversity than honey from Lombok (B1) and green honey from Sabah (B4), while the Simpson index showed that Banggi honey (B4) had higher diversity. Honey samples had significant variance in mycobiome taxonomic composition and abundance. Zygosaccharomyces and Aspergillus were the main genera found in Lombok honey, with percentages of 68.81% and 29.76% respectively. Bali honey samples (B2 and B3) were identified as having a significant amount of the genus Aureobasidium, accounting for 40.81% and 25% of the readings, respectively. The microbiome composition of Banggi honey (B4) showed a high presence of Zygosaccharomyces 45.17% and Aureobasidium 35.24%. The ITS1 analysis effectively distinguishes between honey samples of different origins and its potential as a discriminatory tool for honey origin and authentication purposes.

Navigating spatio-temporal microbiome dynamics: Environmental factors and trace elements shape the symbiont community of an invasive marine species.

The proliferation of marine invasive species is a mounting concern. While the role of microbial communities in invasive ascidian species is recognized, the role of seasonal shifts in microbiome composition remains largely unexplored. We sampled five individuals of the invasive ascidian Styela plicata quarterly from January 2020 to October 2021 in two harbours, examining gills, tunics, and surrounding water. By analysing Amplicon Sequence Variants (ASVs) and seawater trace elements, we found that compartment (seawater, tunic, or gills) was the primary differentiating factor, followed by harbour. Clear seasonal patterns were evident in seawater bacteria, less so in gills, and absent in tunics. We identified compartment-specific bacteria, as well as seasonal indicator ASVs and ASVs correlated with trace element concentrations. Among these bacteria, we found that Endozoicomonas, Hepatoplasma and Rhodobacteraceae species had reported functions which might be necessary for overcoming seasonality and trace element shifts. This study contributes to understanding microbiome dynamics in invasive holobiont systems, and the patterns found indicate a potential role in adaptation and invasiveness.

Baseline amplicon sequencing data for the ITS2 region in the green honey of Banggi Island, Sabah.

Green honey, was discovered on Banggi Island, Sabah, showing high in essential amino acids and chlorophyll derivatives. Despite its lucrative market potential owing to its distinctive color, uncertainties persist regarding its nature. This study leverages amplicon sequencing by targeting micro- and macro-organisms present in honey environmental DNA (eDNA) using Internal Transcribed Spacer 2 (ITS2) region, enabling the identification of floral and microorganism sources that represent the honey's composition. The investigation into green honey from Banggi Island concerns the prevalence of honey adulteration and authenticity for economic gain. Adulteration methods, such as the addition of sugar syrups, compromise honey purity. Using a sequencing approach would help in determining the geographic origin and verifying the authenticity of the honey. The study aims to identify plant species or microorganisms in honey's eDNA. To authenticate honey, we utilized ITS2 with Illumina sequencing, exploring the diversity of green honey samples. Raw sequence reads obtained for the green honey sample revealed 1,438,627 raw reads, with a GC average of 49.22 %. A total of 44 amplicon sequence variances (ASVs) were identified, including three genera: Zygosaccharomyces with two species, Fraxinus with three species, and the genus Ficaria with only one species. Their respective relative abundances were 98.55%, 0.94%, and 0.51%. Zygosaccharomyces rouxii and Zygosaccharomyces mellis were identified as the pre-dominant yeast species in honey, while the Fraxinus and Ficaria genus represent common plant species in Sabah, particularly in Banggi Island. The dominance of Zygosaccharomyces species aligns with their known prevalence in honey, affirming the reliability of our findings. The presence of Fraxinus and Ficaria in the honey sample correlates with its abundance in the local environment. This amplicon sequencing approach not only contributes to our understanding of green honey composition but also serves as a valuable resource for authenticating honey origin in Malaysia, particularly for green honey from Banggi Island, Sabah. Our study pioneers the application of ITS2 amplicon sequencing for green honey amplicon sequencing, providing valuable insights into its composition and origin. This methodology, with a focus on eDNA, contributes to the authentication and quality determination of honey in Malaysia, addressing the pressing concerns of adulteration and variability in production practices.

Microbiome depiction through user-adapted bioinformatic pipelines and parameters.

Introduction. The role of the microbiome in health and disease continues to be increasingly recognized. However, there is significant variability in the bioinformatic protocols for analysing genomic data. This, in part, has impeded the potential incorporation of microbiomics into the clinical setting and has challenged interstudy reproducibility. In microbial compositional analysis, there is a growing recognition for the need to move away from a one-size-fits-all approach to data processing.Gap Statement. Few evidence-based recommendations exist for setting parameters of programs that infer microbiota community profiles despite these parameters significantly impacting the accuracy of taxonomic inference.Aim. To compare three commonly used programs (DADA2, QIIME2, and mothur) and optimize them into four user-adapted pipelines for processing paired-end amplicon reads. We aim to increase the accuracy of compositional inference and help standardize microbiomic protocol.Methods. Two key parameters were isolated across four pipelines: filtering sequence reads based on a whole-number error threshold (maxEE) and truncating read ends based on a quality score threshold (QTrim). Closeness of sample inference was then evaluated using a mock community of known composition.Results. We observed that raw genomic data lost were proportionate to how stringently parameters were set. Exactly how much data were lost varied by pipeline. Accuracy of sample inference correlated with increased sequence read retention. Falsely detected taxa and unaccounted for microbial constituents were unique to pipeline and parameter. Implementation of optimized parameter values led to better approximation of the known mock community.Conclusions. Microbial compositions generated based on the 16S rRNA marker gene should be interpreted with caution. To improve microbial community profiling, bioinformatic protocols must be user-adapted. Analysis should be performed with consideration for the select target amplicon, pipelines and parameters used, and taxa of interest.

Event-Triggered Finite-Time Formation Control of Underactuated Multiple ASVs with Prescribed Performance and Collision Avoidance.

In this paper, an event-triggered finite-time controller is proposed for solving the formation control problems of underactuated multiple autonomous surface vessels (ASVs), including asymmetric mass matrix, collision avoidance, maintaining communication distances and prescribed performance. First, to not only avoid collisions between the follower and leader but also maintain an effective communication distance, a desired tracking distance is designed to be maintained. Second, an improved barrier Lyapunov function (BLF) is proposed to implement the tracking error constraint. In addition, the relative threshold event-triggering strategy effectively solves the communication pressure problem and greatly saves communication resources. Finally, based on coordinate transformation, line of sight (LOS) and dynamic surface control (DSC), a comprehensive finite-time formation control method is proposed to avoid collisions and maintain communication distance. All the signals of the proposed control system can be stabilized in finite time (PFS). The numerical simulation results verify the effectiveness of the proposed control system.

Restoration Measures of Fencing after Tilling Guided Succession of Grassland Soil Microbial Community Structure to Natural Grassland in the Sanjiangyuan Agro-pasture Ecotone of the Qinghai-Tibetan Plateau.

In the fragile Sanjiangyuan (SJY) agro-pasture ecotone of the Qinghai-Tibetan Plateau (QTP), planting and fencing have been used to alleviate grassland degradation and to provide high-quality grass seeds for the implementation of the project of "grain for green". The soil microbe is the major driving factor in maintaining plant productivity and soil nutrient cycling. However, few studies have explored the effects of planting and fencing on soil microorganisms in the SJY agro-pasture ecotone. We explored the effects of tilling (TG) and fencing after tilling (FTG) on soil microbial communities to reveal the effects of restoration measures on soil microbes and to provide a reference in assessing and improving ecosystem structure. The results showed that restoration measures increased soil microbial species diversity and significantly changed their community structure. We found, the microbial composition was more complex under FTG, and its fungal variability was higher and more similar to that of natural grassland. Additionally, restoration measures resulted in fungal co-occurrence network was more edges, higher density, larger diameter and more positive interactions. This was due to the management of the vegetation-soil microenvironment by FTG inducing a differentiation of microbial community structure. In summary, the implementation of FTG could change the microenvironment in the SJY agro-pasture ecotone, so that variation in the structure of microbial community tended toward that of natural grassland, and increased the stability of microbial co-occurrence network, which was more obvious in the fungal community. HIGHLIGHTS: • Restoration measures have changed the vegetation characteristics and soil microenvironment. • Fencing after tilling (FTG) has brought the microenvironment closer to natural grassland. • FTG significantly increased microbial unique ASVs. The number of fungal unique ASVs was similar to that of natural grassland. • FTG resulted in changes in microbial community structure towards natural grasslands and increased the stability of the microbial co-occurrence network, which was more apparent in the fungal community.

Fungal Diversity and Community Composition across Ecosystems.

Fungi have shaped the biosphere since the development of life on Earth. Despite fungi being present in all environments, most of the available fungal research has focused on soils. As a result, the role and composition of fungal communities in aquatic (marine and freshwater) environments remain largely unexplored. The use of different primers to characterise fungal communities has additionally complicated intercomparisons among studies. Consequently, we lack a basic global assessment of fungal diversity across major ecosystems. Here, we took advantage of a recently published 18S rRNA dataset comprising samples from major ecosystems (terrestrial, freshwater, and marine) to attempt a global assessment of fungal diversity and community composition. We found the highest fungal diversities for terrestrial > freshwater > marine environments, and pronounced gradients of fungal diversity along temperature, salinity, and latitude in all ecosystems. We also identified the most abundant taxa in each of these ecosystems, mostly dominated by Ascomycota and Basidiomycota, except in freshwater rivers where Chytridiomycota dominated. Collectively, our analysis provides a global analysis of fungal diversity across all major environmental ecosystems, highlighting the most distinct order and ASVs (amplicon sequencing variants) by ecosystem, and thus filling a critical gap in the study of the Earth's mycobiome.

Dietary and Sexual Correlates of Gut Microbiota in the Japanese Gecko, Gekko japonicus (Schlegel, 1836).

Numerous studies have demonstrated that multiple intrinsic and extrinsic factors shape the structure and composition of gut microbiota in a host. The disorder of the gut microbiota may trigger various host diseases. Here, we collected fecal samples from wild-caught Japanese geckos (Gekko japonicus) and captive conspecifics fed with mealworms (mealworm-fed geckos) and fruit flies (fly-fed geckos), aiming to examine the dietary and sexual correlates of the gut microbiota. We used 16S rRNA gene sequencing technology to determine the composition of the gut microbiota. The dominant phyla with a mean relative abundance higher than 10% were Verrucomicrobiota, Bacteroidota, and Firmicutes. Gut microbial community richness and diversity were higher in mealworm-fed geckos than in wild geckos. Neither community evenness nor beta diversity of gut microbiota differed among wild, mealworm-fed, and fly-fed geckos. The beta rather than alpha diversity of gut microbiota was sex dependent. Based on the relative abundance of gut bacteria and their gene functions, we concluded that gut microbiota contributed more significantly to the host's metabolic and immune functions. A higher diversity of gut microbiota in mealworm-fed geckos could result from higher chitin content in insects of the order Coleoptera. This study not only provides basic information about the gut microbiota of G. japonicus but also shows that gut microbiota correlates with dietary habits and sex in the species.

Seasonal shift in gut microbiome diversity in wild Sichuan takin (Budorcas tibetanus) and environmental adaptation.

In this study, we investigated the change in microbiome composition of wild Sichuan takin (Budorcas tibetanus) during winter and spring and analyzed the physiological implications for such changes. Diversity analyses of the microbiome (average 15,091 high-quality reads per sample) in 24 fecal samples (15 from winter, 9 from spring) revealed that spring samples had higher species diversity and were compositionally different from winter samples (P < 0.05). Taxonomic composition analysis showed that the relative abundance increased in spring for Patescibacteria (2.7% vs. 0.9% in winter, P < 0.001) and Tenericutes (1.9% vs. 1% in winter, P < 0.05). Substantial increases in relative abundance of Ruminococcaceae and Micrococcaceae were identified in spring and winter, respectively. Mann-Whitney U and ANCOM identified seven differentially abundant genera: Enterococcus, Acetitomaculum, Blautia, Coprococcus 1, Lachnospiraceae UCG 008, Ruminococcus 2 and Ralstonia. All seven genera were significantly more abundant in spring (average 0.016-1.2%) than winter (average 0-0.16%), with the largest difference found in Ruminococcus (1.21% in spring vs. 0.16% in winter). The other six genera were undetectable in winter. Functional prediction and pathway analysis revealed that biosynthesis of cofactors (ko01240) had the highest gene count ratios in the winter, followed by the two-component system (ko02020). Seasonal variation affects the gut microbiomes in wild Sichuan takins, with winter associated with lower species diversity and spring with enrichment of cellulose-degrading genera and phytopathogens. Such changes were crucial in their adaptation to the environment, particularly the difference in food abundance.

Metagenomics and metabarcoding experimental choices and their impact on microbial community characterization in freshwater recirculating aquaculture systems.

BACKGROUND: Microbial communities in recirculating aquaculture systems (RAS) play a role in system success, nutrient cycling, and water quality. Considering the increasing socio-economic role of fish farming, e.g., regarding food security, an in-depth understanding of aquaculture microbial communities is also relevant from a management perspective, especially regarding the growth, development, and welfare of the farmed animal. However, the current data on the composition of microbial communities within RAS is patchy, which is partly attributable to diverging method choices that render comparative analyses challenging. Therefore, there is a need for accurate, standardized, and user-friendly methods to study microbial communities in aquaculture systems. RESULTS: We compared sequencing approach performances (3 types of 16S short amplicon sequencing, PacBio long-read amplicon sequencing, and amplification-free shotgun metagenomics) in the characterization of microbial communities in two commercial RAS fish farms. Results showed that 16S primer choice and amplicon length affect some values (e.g., diversity measures, number of assigned taxa or distinguishing ASVs) but have no impact on spatio-temporal patterns between sample types, farms and time points. This implies that 16S rRNA approaches are adequate for community studies. The long-read amplicons underperformed regarding the quantitative resolution of spatio-temporal patterns but were suited to identify functional services, e.g., nitrification cycling and the detection of pathogens. Finally, shotgun metagenomics extended the picture to fungi, viruses, and bacteriophages, opening avenues for exploring inter-domain interactions. All sequencing datasets agreed on major prokaryotic players, such as Actinobacteriota, Bacteroidota, Nitrospirota, and Proteobacteria. CONCLUSION: The different sequencing approaches yielded overlapping and highly complementary results, with each contributing unique data not obtainable with the other approaches. We conclude that a tiered approach constitutes a strategy for obtaining the maximum amount of information on aquaculture microbial communities and can inform basic research on community evolution dynamics. For specific and/or applied questions, single-method approaches are more practical and cost-effective and could lead to better farm management practices.

Disturbance observer-based prescribed performance super-twisting sliding mode control for autonomous surface vessels.

This paper proposes a disturbance observer-based prescribed performance super-twisting sliding mode control (DOB PPSTSMC) for trajectory tracking of the autonomous surface vessels (ASVs) subject to unknown external disturbances and modeling errors. Both unknown external disturbances and system modeling errors are approximated by the disturbance observer, thus eliminating most of the effect caused by lumped disturbances in the control performance. Based on this, a prescribed performance super-twisting sliding mode controller is explored to further suppress the residual error of disturbance compensation. Prescribed performance constraints are considered in the coming up with the super-twisting sliding mode controller, so that ASVs not only achieve effective tracking of time-varying desired trajectories, but also improve the transient performance of the control system. In addition, the controller is continuous and chatter-free, which has greater practical value. The excellence of the control project design is highlighted through the simulation and comparison results.

The microbiome of the pelagic tunicate Dolioletta gegenbauri: A potential link between the grazing and microbial food web.

Bloom-forming gelatinous zooplankton occur circumglobally and significantly influence the structure of pelagic marine food webs and biogeochemical cycling through interactions with microbial communities. During bloom conditions especially, gelatinous zooplankton are keystone taxa that help determine the fate of primary production, nutrient remineralization, and carbon export. Using the pelagic tunicate Dolioletta gegenbauri as a model system for gelatinous zooplankton, we carried out a laboratory-based feeding experiment to investigate the potential ecosystem impacts of doliolid gut microbiomes and microbial communities associated with doliolid faecal pellets and the surrounding seawater. Metabarcoding targeting Bacteria and Archaea 16S rRNA genes/Archaea) and qPCR approaches were used to characterize microbiome assemblages. Comparison between sample types revealed distinct patterns in microbial diversity and biomass that were replicable across experiments. These observations support the hypothesis that through their presence and trophic activity, doliolids influence the structure of pelagic food webs and biogeochemical cycling in subtropical continental shelf systems where tunicate blooms are common. Bacteria associated with starved doliolids (representative of the resident gut microbiome) possessed distinct low-biomass and low-diversity microbial assemblages, suggesting that the doliolid microbiome is optimized to support a detrital trophic mode. Bacterial genera Pseudoalteromomas and Shimia were the most abundant potential core microbiome taxa, similar to patterns observed in other marine invertebrates. Exploratory bioinformatic analyses of predicted functional genes suggest that doliolids, via their interactions with bacterial communities, may affect important biogeochemical processes including nitrogen, sulphur, and organic matter cycling.

Identification of changes in the microflora composition of Japanese horse mackerel (Trachurus japonicus) during storage to identify specific spoilageorganisms.

Japanese horse mackerel (Trachurus japonicus) is an important marine resource, and its loss and waste should be reduced. This study aimed to identify the changes in the microflora composition during storage and specific spoilage organisms (SSOs) in Japanese horse mackerel, for spoilage prevention. They were stored at either 20 °C or 4 °C aerobically, and the bacterial viable counts, concentration of total volatile basic nitrogen (TVB-N), and microflora composition for each group were analyzed. Samples stored at 20 °C for 48 h showed similar viable counts to those stored at 4 °C for 168 h; however, the TVB-N concentrations increased at 20 °C, but not at 4 °C. 16S rRNA metagenome analysis showed that Shewanella became dominant genus in the microflora regardless of the storage temperature. However, dominant amplicon sequence variants (ASVs), which are a more detailed classification level than the genus, differed depending on the storage temperatures; therefore, dominant ASVs at 20 °C were assumed to be potential SSOs. Shewanella sp. Strain NFH-SH190041, which was genetically closely related to the dominant ASVs at 20 °C, was isolated, and its spoilage ability was verified. The strain NFH-SH190041 may be considered a novel SSO of Japanese horse mackerel because its 16S rRNA sequence is clearly different from those of known species.

A Path-Following Controller for Marine Vehicles Using a Two-Scale Inner-Outer Loop Approach.

This article addresses the problem of path following of marine vehicles along straight lines in the presence of currents by resorting to an inner-outer control loop strategy, with due account for the presence of currents. The inner-outer loop control structures exhibit a fast-slow temporal scale separation that yields simple "rules of thumb" for controller tuning. Stated intuitively, the inner-loop dynamics should be much faster than those of the outer loop. Conceptually, the procedure described has three key advantages: (i) it decouples the design of the inner and outer control loops, (ii) the structure of the outer-loop controller does not require exact knowledge of the vehicle dynamics, and (iii) it provides practitioners a very convenient method to effectively implement path-following controllers on a wide range of vehicles. The path-following controller discussed in this article is designed at the kinematic outer loop that commands the inner loop with the desired heading angles while the vehicle moves at an approximately constant speed. The key underlying idea is to provide a seamless implementation of path-following control algorithms on heterogeneous vehicles, which are often equipped with heading autopilots. To this end, we assume that the heading control system is characterized in terms of an IOS-like relationship without detailed knowledge of vehicle dynamics parameters. This paper quantitatively evaluates the combined inner-outer loop to obtain a relationship for assessing the combined system's stability. The methods used are based on nonlinear control theory, wherein the cascade and feedback systems of interest are characterized in terms of their IOS properties. We use the IOS small-gain theorem to obtain quantitative relationships for controller tuning that are applicable to a broad range of marine vehicles. Tests with AUVs and one ASV in real-life conditions have shown the efficacy of the path-following control structure developed.

DNA Metabarcoding and Isolation by Baiting Complement Each Other in Revealing Phytophthora Diversity in Anthropized and Natural Ecosystems.

Isolation techniques supplemented by sequencing of DNA from axenic cultures have provided a robust methodology for the study of Phytophthora communities in agricultural and natural ecosystems. Recently, metabarcoding approaches have emerged as new paradigms for the detection of Phytophthora species in environmental samples. In this study, Illumina DNA metabarcoding and a conventional leaf baiting isolation technique were compared to unravel the variability of Phytophthora communities in different environments. Overall, 39 rhizosphere soil samples from a natural, a semi-natural and a horticultural small-scale ecosystem, respectively, were processed by both baiting and metabarcoding. Using both detection techniques, 28 out of 39 samples tested positive for Phytophthora. Overall, 1,406,613 Phytophthora internal transcribed spacer 1 (ITS1) sequences and 155 Phytophthora isolates were obtained, which grouped into 21 taxa, five retrieved exclusively by baiting (P. bilorbang; P. cryptogea; P. gonapodyides; P. parvispora and P. pseudocryptogea), 12 exclusively by metabarcoding (P. asparagi; P. occultans; P. psycrophila; P. syringae; P. aleatoria/P. cactorum; P. castanetorum/P. quercina; P. iranica-like; P. unknown sp. 1; P. unknown sp. 2; P. unknown sp. 3; P. unknown sp. 4; P. unknown sp. 5) and four with both techniques (P. citrophthora, P. multivora, P. nicotianae and P. plurivora). Both techniques complemented each other in describing the variability of Phytophthora communities from natural and managed ecosystems and revealing the presence of rare or undescribed Phytophthora taxa.

Exploration of the Types of Rarity in the Arctic Ocean from the Perspective of Multiple Methodologies.

The Arctic Ocean is facing rapid environmental changes with cascading effects on the entire Arctic marine ecosystem. However, we have a limited understanding of the consequences such changes have on bacteria and archaea (prokaryotes) at the base of the marine food web. In this study, we show how the prokaryotic rare biosphere behaves over a range of highly heterogeneous environmental conditions using 16S rRNA gene reads from amplicon and metagenome sequencing data from seawater samples collected during the Norwegian young sea ICE expedition between late winter and early summer. The prokaryotic rare biosphere was analyzed using different approaches: amplicon sequence variants and operational taxonomic units from the 16S rRNA gene amplicons and operational taxonomic units from the 16S rRNA genes of the metagenomes. We found that prokaryotic rare biosphere communities are specific to certain water masses, and that the majority of the rare taxa identified were always rare and disappeared in at least one sample under changing conditions, suggesting their high sensitivity to environmental heterogeneity. In addition, our methodological comparison revealed a good performance of 16S rRNA gene amplicon sequencing in describing rare biosphere patterns, while the metagenome-derived data were better to capture a significant diversity of so-far uncultivated rare taxa. Our analysis on the dynamics of the rare prokaryotic biosphere, by combining different methodological approaches, improves the description of the types of rarity predicted from Community Assembly theory in the Arctic Ocean.

Interactions between soil compositions and the wheat root microbiome under drought stress: From an in silico to in planta perspective.

As wheat (Triticum aestivum) is an important staple food across the world, preservation of stable yields and increased productivity are major objectives in breeding programs. Drought is a global concern because its adverse impact is expected to be amplified in the future due to the current climate change. Here, we analyzed the effects of edaphic, environmental, and host factors on the wheat root microbiomes collected in soils from six regions in Belgium. Amplicon sequencing analysis of unplanted soil and wheat root endosphere samples indicated that the microbial community variations can be significantly explained by soil pH, microbial biomass, wheat genotype, and soil sodium and iron levels. Under drought stress, the biodiversity in the soil decreased significantly, but increased in the root endosphere community, where specific soil parameters seemingly determine the enrichment of bacterial groups. Indeed, we identified a cluster of drought-enriched bacteria that significantly correlated with soil compositions. Interestingly, integration of a functional analysis further revealed a strong correlation between the same cluster of bacteria and ß-glucosidase and osmoprotectant proteins, two functions known to be involved in coping with drought stress. By means of this in silico analysis, we identified amplicon sequence variants (ASVs) that could potentially protect the plant from drought stress and validated them in planta. Yet, ASVs based on 16S rRNA sequencing data did not completely distinguish individual isolates because of their intrinsic short sequences. Our findings support the efforts to maintain stable crop yields under drought conditions through implementation of root microbiome analyses.