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This study investigates how cover crops (CC) and different application rates of glyphosate-based herbicide (GBH) may affect soil microbial communities. Our hypothesis was that the use of CC would promote the presence of certain microbial communities in soils and mitigate the potential impact of GBH on these communities. CC can promote biodiversity by increasing plant diversity in fields, while GBH may have non-target effects on species that utilize the shikimate pathway. Crop managements in an experimental field in Southern Québec (Canada) consisted in Glyphosate-based Herbicide (GBH) applications rates at 0.84, 1.67 and 3.33 L ha−1 in corn, soybean and wheat fields cultivated with Direct Seeding along with CC (DSCC) and at 3.33 L ha−1 in similar crops cultivated with direct seeding but without CC (DS). DSCC did not significantly impact microbial richness compared to DS, but did alter specific abundance among prokaryotes and eukaryotes. A permutational multivariate analysis revealed that the type of crop (soybean, wheat, maize) significantly influenced the composition of eukaryotic communities in 2018 and 2019, but not prokaryotic communities. Importantly, the study identifies a cross-effect between CC and GBH application rates suggesting that herbicide use in soybean plots can influence Anaeromyxobacter populations. Also, higher abundance of Enoplea and Maxilopoda were observed in plots with the lower application rate of GBH. Both eukaryotes group are known to be sensitive to crop management. These findings emphasize the need for a holistic approach to agricultural practices, considering the combined effects of both CC and GBH application rates on soil microbial health. Ultimately, the study calls for sustainable agricultural practices that preserve microbial diversity, which is essential for maintaining ecosystem services and soil health. [ABSTRACT FROM AUTHOR]

This study aimed to analyse the microbial biodiversity in ceriantharian tubes through shotgun metagenomics, to enhance the understanding of ecological dynamics in these microhabitats. We sampled two tubes of Ceriantheomorphe brasiliensis in Florianópolis (SC), and two tubes of Ceriantheopsis lineata in Alcatrazes archipelago (AK), South and Southeast Brazil, respectively. The environmental DNA from the tubes was extracted, amplified, and submitted to shotgun metagenomics sequencing on the Illumina HiSeq platform, and the biodiversity analysis was run using the Kraken2 software. Our results indicate that Ceriantharia-associated microbiomes likely harbour novel microbial diversity, as roughly only 8% of metagenomic reads were classified. Microbial composition was highly similar in both locations, with the Bacteria domain predominating, particularly the phyla Pseudomonadota and Actinomycetota. Nitrososphaerota was consistently the most common archaeal phylum in all samples. The bacterial classes Betaproteobacteria and Planctomycetia, and the archaeal class Nitrososphaeria were present in all four tubes, as were the bacterial family Pseudomonodaceae and the archaeal family Nitrosopumilaceae. Roseobactereaceae dominated alphaproteobacterial families from AK tubes, while Streptomycetaceae prevailed among actinobacterial families from SC tubes. The α-diversity indicates similar values between AK and SC samples, with slight distinctions favouring SC. β-diversity results show higher similarity within the same locations (AK or SC) than between different locations, highlighting spatial influence on microbial composition. To the best of our knowledge, this study is the first to address microbial composition found in ceriantharian tubes, using shotgun metagenomics, and our findings set up the scenario for a wider comprehension of these cnidarians as key holobionts in marine ecosystems. [ABSTRACT FROM AUTHOR]

Ubiquitination is an evolutionary, ancient system of post-translational modification of proteins that occurs through a cascade involving ubiquitin activation, transfer, and conjugation. The maturation of this system has followed two main pathways. The first is the conservation of a universal structural fold of ubiquitin and ubiquitin-like proteins, which are present in both Archaea and Bacteria, as well as in multicellular Eukaryotes. The second is the rise of the complexity of the superfamily of ligases, which conjugate ubiquitin-like proteins to substrates, in terms of an increase in the number of enzyme variants, greater variation in structural organization, and the diversification of their catalytic domains. Here, we examine the diversity of the ubiquitination system among different organisms, assessing the variety and conservation of the key domains of the ubiquitination enzymes and ubiquitin itself. Our data show that E2 ubiquitin-conjugating enzymes of metazoan phyla are highly conservative, whereas the homology of E3 ubiquitin ligases with human orthologues gradually decreases depending on "molecular clock" timing and evolutionary distance. Surprisingly, Chordata and Echinodermata, which diverged over 0.5 billion years ago during the Cambrian explosion, share almost the same homology with humans in the amino acid sequences of E3 ligases but not in their adaptor proteins. These observations may suggest that, firstly, the E2 superfamily already existed in its current form in the last common metazoan ancestor and was generally not affected by purifying selection in metazoans. Secondly, it may indicate convergent evolution of the ubiquitination system and highlight E3 adaptor proteins as the "upper deck" of the ubiquitination system, which plays a crucial role in chordate evolution. [ABSTRACT FROM AUTHOR]

This study investigates how cover crops (CC) and different application rates of glyphosate-based herbicide (GBH) may affect soil microbial communities. Our hypothesis was that the use of CC would promote the presence of certain microbial communities in soils and mitigate the potential impact of GBH on these communities. CC can promote biodiversity by increasing plant diversity in fields, while GBH may have non-target effects on species that utilize the shikimate pathway. Crop managements in an experimental field in Southern Québec (Canada) consisted in Glyphosate-based Herbicide (GBH) applications rates at 0.84, 1.67 and 3.33 L ha−1 in corn, soybean and wheat fields cultivated with Direct Seeding along with CC (DSCC) and at 3.33 L ha−1 in similar crops cultivated with direct seeding but without CC (DS). DSCC did not significantly impact microbial richness compared to DS, but did alter specific abundance among prokaryotes and eukaryotes. A permutational multivariate analysis revealed that the type of crop (soybean, wheat, maize) significantly influenced the composition of eukaryotic communities in 2018 and 2019, but not prokaryotic communities. Importantly, the study identifies a cross-effect between CC and GBH application rates suggesting that herbicide use in soybean plots can influence Anaeromyxobacter populations. Also, higher abundance of Enoplea and Maxilopoda were observed in plots with the lower application rate of GBH. Both eukaryotes group are known to be sensitive to crop management. These findings emphasize the need for a holistic approach to agricultural practices, considering the combined effects of both CC and GBH application rates on soil microbial health. Ultimately, the study calls for sustainable agricultural practices that preserve microbial diversity, which is essential for maintaining ecosystem services and soil health.

ABSTRACT This paper presents two low-cost hands-on activities designed to enhance student understanding and address the pedagogical challenges faced by microbiology professors in teaching concepts related to cell structure and gene regulation. In the first activity, we used Shrinky Dinks and Jeopardy-style game questions to explore the differences between prokaryotic and eukaryotic cells. Students have to collect pieces and physically build their cell models. The second activity uses origami organelles sets from Edvotek to illustrate the regulation of gene expression in the lac and trp operons, incorporating mutation scenarios for analysis. The intended audience comprises undergraduate students in microbiology, including biology, pre-medical studies, and health profession majors. The activities were deployed in three microbiology lectures, and students were surveyed. Students’ feedback highlights the efficacy of the hands-on approach and increased class participation, as two of the recurring words in the students’ survey were “helpful” and “fun.”

Coastal sediments are a critical domain for carbon sequestration and are profoundly impacted by human activities. Therefore, it is essential to understand the structure and components of benthic autotrophs that play a crucial role in carbon sequestration processes, as well as the influence of anthropogenic activities on their communities. This study utilized an urban estuary, an industrial sea bay, a maricultural sea region, and two mangrove coastlines within the coastal areas of Guangdong Province, China. The micro-benthos in these environments, including prokaryotes and eukaryotes, were identified through high-throughput sequencing of 16S rRNA and 18S rRNA genes. The findings show that the autotrophic composition was altered by the interactions of anthropogenic heavy metals (Cd and Zn) and micro-eukaryotes (protazoa, metazoa, and parasitic organisms). Industrial pollution reduced the abundance of both prokaryotic and eukaryotic autotrophs. Mangroves induced a substantial transformation in the sediment eukaryotic and prokaryotic composition, increasing the proportion of autotrophs, notably sulfur-oxidizing and iron-oxidizing bacteria and microalgae. This alteration suggests an increase in specific sulfur and iron cycling with simultaneous carbon sequestration within mangrove sediments. These results indicate that anthropogenic activities affect sediment carbon sequestration by altering autotrophic assemblages along coastlines, thereby inducing consequential shifts in overall elemental cycling processes. [Display omitted] • Heavy metals (Cu and Zn) determined the benthic prokaryotic autotrophs. • Mangrove sediment enhanced the functional autotrophs of S/Fe-oxidizer and algae. • Industrial coastal sediment inhibited the growth of autotrophs. • The changed of functional autotrophs would finally affect the C, N, S, Fe cycling processes. [ABSTRACT FROM AUTHOR]

Marine microorganisms are involved in a variety of biogeochemical cycles and live in diverse ecological communities where they interact with each other and with other organisms to guarantee ecosystem functions. The present study focused on a shallow marine environment located in Ría de Vigo (NW, Spain), where sediment and size-fractionated plankton samples were collected from 2016 to 2018. DNA metabarcoding was used to describe the eukaryote and prokaryote composition and diversity in sediments and plankton and to depict possible associations among the most frequent and abundant organisms by co-occurrence network analysis. High eukaryote and prokaryote diversity indices were obtained in all compartments. Significant differences among eukaryote and prokaryote communities were found between sediment and plankton samples, with a high percentage of exclusive operational taxonomic units (OTUs) associated with each compartment, especially from sediment. Despite these differences, shared taxa between water and sediment were also obtained, suggesting a relatively meaningful exchange of organisms between both environmental compartments. Significant co-occurrences were mainly obtained between prokaryotes (41%), followed by eukaryotes–prokaryotes (32%) and between eukaryotes (27%). The abundant and strong positive correlations between organisms, including representatives from the sediment and the water column, suggested an essential role of biotic interactions as community-structuring factors in shallow waters where beneficial associations likely prevail. This study provides a novel approach for the detailed description of the eukaryote and prokaryote diversity and co-occurrence patterns in a shallow marine area, including both the sediment and different water-size fractions. The high diversity obtained and the detection of predominantly coexisting interactions among organisms from sediment and the overlying water column suggest a movement of species between both habitats and therefore confirm the importance of integratively studying shallow marine ecosystems.

Mangrove trees generally play important roles in protecting intertidal ecosystems. The mangrove root-associated sediments provide a repertoire of microbial communities that contribute to pivotal ecological functions in the system. In the present study, we used the high-throughput sequencing and PICRUSt-predicted functional information (based on 16S/18S rDNA profiles) to investigate the bacterial, archaeal, and fungal communities in two mangrove systems, located in the estuary of the Jiulong River (China), with different contaminated conditions and frequencies of human activity. Diverse distribution patterns for microbial communities were observed in six sediment samples collected from the two survey areas, which were found to be related mainly to the substrates in mangrove sediments. The sediments were predominated by relatively higher ratios of heterotrophic bacteria that participated in the degradation of organic matters, including phylum of Chloroflexi, Acidobacteriota, Desulfobacterota, and Proteobacteria. In addition, Crenarchaeota and Ascomycota presented the highest abundances of archaea and fungi, respectively. The relatively high concentrations of calcium, nitrogen, magnesium, and phosphorus in mangrove sediments correlated significantly with the microbial communities. In addition, although the potential functions were similar in the two sites based on COG and KEGG pathways, the abundances of enzymes involved in the degradation processes of cellulose and hemicellulose and the metabolism of nitrogen and sulfur presented distinctions. These results provide insights into the environmental conditions shaping microbial assemblies of the mangrove sediments under the impacts of human activities; for instance, a more abundant amount of calcium was found in urban areas in this study. [ABSTRACT FROM AUTHOR]

The remarkable diversity of sterol biosynthetic capacities described in living organisms is enriched at a fast pace by a growing number of sequenced genomes. Whereas analytical chemistry has produced a wealth of sterol profiles of species in diverse taxonomic groups including seed and non-seed plants, algae, phytoplanktonic species and other unicellular eukaryotes, functional assays and validation of candidate genes unveils new enzymes and new pathways besides canonical biosynthetic schemes. An overview of the current landscape of sterol pathways in the tree of life is tentatively assembled in a series of sterolotypes that encompass major groups and provides also peculiar features of sterol profiles in bacteria, fungi, plants, and algae.

The remarkable diversity of sterol biosynthetic capacities described in living organisms is enriched at a fast pace by a growing number of sequenced genomes. Whereas analytical chemistry has produced a wealth of sterol profiles of species in diverse taxonomic groups including seed and non-seed plants, algae, phytoplanktonic species and other unicellular eukaryotes, functional assays and validation of candidate genes unveils new enzymes and new pathways besides canonical biosynthetic schemes. An overview of the current landscape of sterol pathways in the tree of life is tentatively assembled in a series of sterolotypes that encompass major groups and provides also peculiar features of sterol profiles in bacteria, fungi, plants, and algae. [ABSTRACT FROM AUTHOR]

Humans have coexisted with pathogenic microorganisms throughout its history of evolution. We have never halted the exploration of pathogenic microorganisms. With the improvement of genome-sequencing technology and the continuous reduction of sequencing costs, an increasing number of complete genome sequences of pathogenic microorganisms have become available. Genome annotation of this massive sequence information has become a daunting task in biological research. This paper summarizes the approaches to the genome annotation of pathogenic microorganisms and the available popular genome annotation tools for prokaryotes, eukaryotes and viruses. Furthermore, real-world comparisons of different annotation tools using 12 genomes from prokaryotes, eukaryotes and viruses were conducted. Current challenges and problems were also discussed. [ABSTRACT FROM AUTHOR]

The present study focused on the bioaccumulation and cytotoxicities of Cd2+, CdSe quantum dots (QDs) and CdSe/ZnS QDs in Escherichia coli (E. coli , represents prokaryotic system) and Phanerochaete chrysosporium (P. chrysosporium , represents eukaryotic system), respectively. Two types of QDs were characterized by transmission electron microscopy (TEM) and dynamic light scattering. The inductively coupled plasma optical emission spectrometer results showed that the bioaccumulation amounts of CdSe QDs by E. coli and P. chrysosporium were larger than those of CdSe/ZnS QDs due to the smaller particle size and less negative surface charges of CdSe QDs. Confocal microscopy and TEM results showed that there was an interaction between QDs and cells, and QDs have entered into the cells eventually, leading to the change of cell morphology. Plasma membrane fluidities and membrane H+-ATPase activities of E. coli and P. chrysosporium decreased gradually with the increasing concentrations of Cd2+, CdSe and CdSe/ZnS QDs. Results of the cell viabilities and intracellular reactive oxygen species levels indicated that the induced cytotoxicities were decreased as follows: CdSe QDs > CdSe/ZnS QDs > Cd2+. These findings suggested that the cytotoxicity of QDs was not only attributed to their heavy metal components, but also related to their nanosize effects which could induce particle-specific toxicity. The above results offer valuable information for exploring the cytotoxicity mechanism of QDs in prokaryote and eukaryote. Image 1 • CdSe QDs were more easily absorbed by cells as compared to CdSe/ZnS QDs. • P. chrysosporium was more sensitive to Cd2+, CdSe and CdSe/ZnS QDs than E. coli. • The intracellular ROS level was dependent on the intracellular concentration of QDs. [ABSTRACT FROM AUTHOR]

In the past decade, extracellular vesicles (EVs) have been recognized as potent vehicles of intercellular communication, both in prokaryotes and eukaryotes. This is due to their capacity to transfer proteins, lipids and nucleic acids, thereby influencing various physiological and pathological functions of both recipient and parent cells. While intensive investigation has targeted the role of EVs in different pathological processes, for example, in cancer and autoimmune diseases, the EV-mediated maintenance of homeostasis and the regulation of physiological functions have remained less explored. Here, we provide a comprehensive overview of the current understanding of the physiological roles of EVs, which has been written by crowd-sourcing, drawing on the unique EV expertise of academia-based scientists, clinicians and industry based in 27 European countries, the United States and Australia. This review is intended to be of relevance to both researchers already working on EV biology and to newcomers who will encounter this universal cell biological system. Therefore, here we address the molecular contents and functions of EVs in various tissues and body fluids from cell systems to organs. We also review the physiological mechanisms of EVs in bacteria, lower eukaryotes and plants to highlight the functional uniformity of this emerging communication system.

Coral reefs are among the most biodiverse habitats on Earth, but knowledge of their associated marinemicrobiome remains limited. To increase the understanding of the coral reef ecosystem in the lower Gulf of Thailand, this study utilized 16S and 18S rRNA gene-based pyrosequencing to identify the prokaryotic and eukaryotic microbiota present in the reef water at Kham Island, Trat province, Thailand (N6.97 E100.86). The obtained result was then compared with the published microbiota from different coral reef water and marine sites. The coral reefs at Kham Island are of the fringe type. The reefs remain preserved and abundant. The community similarity indices (i.e., Lennon similarity index, Yue & Clayton similarity index) indicated that the prokaryotic composition of Kham was closely related to that of Kra, another fringing reef site in the lower Gulf of Thailand, followed by coral reef water microbiota at GS048b (Cooks Bay, Fr. Polynesia), Palmyra (Northern Line Islands, United States) and GS108b (Coccos Keeling, Australia), respectively. Additionally, the microbial eukaryotic populations at Kham was analyzed and compared with the available database at Kra. Both eukaryotic microbiota, in summer and winter seasons, were correlated. An abundance of Dinophysis acuminata was noted in the summer season, in accordance with its reported cause of diarrhoeatic shellfish outbreak in the summer season elsewhere. The slightly lower biodiversity in Kham than at Kra might reflect the partly habitat difference due to coastal anthropogenic activities and minor water circulation, as Kham locates close to the mainland and is surrounded by islands (e.g., Chang and Kut islands). The global marine microbiota comparison suggested relatively similar microbial structures among coral sites irrespective of geographical location, supporting the importance of coral-associated marine microbiomes, and Spearman’s correlation analysis between community membership and factors of shore distance and seawater temperature indicated potential correlation of these factors (p-values < 0.05) with Kham, Kra, and some other coral and coastal sites. Together, this study provided the second marine microbial database for the coral reef of the lower Gulf of Thailand, and a comparison of the coral-associated marine microbial diversity among global ocean sites.

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Biological treatment represents a key step in nutrient removal from wastewater. Until now these process has mainly been considered prokaryotic, with the interactions between prokaryotes and eukaryotes not being properly explored. We therefore investigated the co-occurrence of eukaryotes and prokaryotes in biological nitrogen removal biofilms. We found that biofilms in the nitrifying reactor contained the highest diversity and abundance of both prokaryotes and eukaryotes, with nearly three times higher prokaryote species richness than for the denitrifying reactor. The positive associations between eukaryote abundance and prokaryote diversity could potentially be explained by mutualism - and/or predator/prey interactions. Further mechanistic insight, however, is needed to determine the main diversifying mechanisms. In summary, eukaryote and prokaryote interactions seem to play a fundamental yet underexplored role in biological wastewater treatment. Significance and Impact of the Study Eukaryote and prokaryote interactions may play an important role in wastewater treatment. This study found that prokaryote species richness was nearly three times higher in the aerobe nitrification than in an anaerobe denitrification reactor, coinciding with the highest level of eukaryotes. This knowledge can be important in process control, and potentially in the development of novel approaches based on nitrate accumulating denitrifying eukaryotes. [ABSTRACT FROM AUTHOR]

Nitrogen is a critical element for algal growth and shifting its concentration above or below the optimum concentration may have a deleterious effect on algal cells. Antioxidants are one of the important factors that protect algal cells from stresses, e.g., nitrogen stress. The purpose of this study was to evaluate the biomass, pigments, antioxidant compounds and activities of two algal species, Arthrospira platensis (prokaryotic Cyanophyta) and Pseudochlorella pringsheimii (eukaryotic Chlorophyta) under hypo- and hyper-nitrogen concentrations. In general, the increase in the nitrogen concentrations of the nutrient medium (75 and 6-18 mM for A. platensis and P. pringsheimii, respectively) led to an increase in the biomass yield, pigments and other antioxidant contents. However, this increment was reversed by further N additions. The data showed that the prokaryotic alga ( A. platensis) can grow at relatively hyper-nitrogen concentrations rather than the eukaryotic one ( P. pringsheimii). The antioxidant enzyme activities for the both species were significantly stimulated with the relatively lower nitrogen concentrations, while increasing the N concentrations in the media decreased the enzyme activities. Despite the superiority of A. platensis as a potent antioxidants source, both algae showed high antioxidant levels compared to the synthetic antioxidant marker (butylated hydroxytoluene, BHT). [ABSTRACT FROM AUTHOR]

Orthologs are widely used for phylogenetic analysis of species; however, identifying genuine orthologs among distantly related species is challenging, because genes obtained through horizontal gene transfer (HGT) and out-paralogs derived from gene duplication before speciation are often present among the predicted orthologs. We developed a program, “Ortholog-Finder,” to obtain ortholog data sets for performing phylogenetic analysis by using all open-reading frame data of species. The program includes five processes forminimizing the effects of HGT and out-paralogs in phylogeny construction: 1) HGT filtering: Genes derived from HGT could be detected and deleted from the initial sequence data set by examining their base compositions. 2)Out-paralog filtering:Outparalogs aredetected anddeleted fromthe data setbasedonsequence similarity.3)Classificationof phylogenetic trees: Phylogenetic trees generated for ortholog candidates are classified as monophyletic or polyphyletic trees. 4) Tree splitting: Polyphyletic trees are bisected to obtain monophyletic trees and remove HGT genes and out-paralogs. 5) Threshold changing: Out-paralogs are further excluded from the data set based on the difference in the similarity scores of genuine orthologs and out-paralogs.Weexaminedhow out-paralogs and HGTs affected phylogenetic trees constructed for species based on ortholog data sets obtained by Ortholog-Finder with the use of simulation data, andwe determined the effects of confounding factors.Wethen used Ortholog-Finder in phylogeny construction for 12 Gram-positive bacteria from two phyla and validated each node of the constructed tree by comparison with individually constructed ortholog trees. [ABSTRACT FROM AUTHOR]

The aquatic microbiome is composed of a multi-phylotype community of microbes, ranging from the numerically dominant viruses to the phylogenetically diverse unicellular phytoplankton. They influence key biogeochemical processes and form the base of marine food webs, becoming food for secondary consumers. Due to recent advances in next-generation sequencing, this previously overlooked component of our hydrosphere is starting to reveal its true diversity and biological complexity. We report here that 250 mL of seawater is sufficient to provide a comprehensive description of the microbial diversity in an oceanic environment. We found that there was a dominance of the order Caudovirales (59%), with the family Myoviridae being the most prevalent. The families Phycodnaviridae and Mimiviridae made up the remainder of pelagic double-stranded DNA (dsDNA) virome. Consistent with this analysis, the Cyanobacteria dominate (52%) the prokaryotic diversity. While the dinoflagellates and their endosymbionts, the superphylum Alveolata dominates (92%) the microbial eukaryotic diversity. A total of 834 prokaryotic, 346 eukaryotic and 254 unique virus phylotypes were recorded in this relatively small sample of water. We also provide evidence, through a metagenomic-barcoding comparative analysis, that viruses are the likely source of microbial environmental DNA (meDNA). This study opens the door to a more integrated approach to oceanographic sampling and data analysis.

In the past decade, extracellular vesicles (EVs) have been recognized as potent vehicles of intercellular communication, both in prokaryotes and eukaryotes. This is due to their capacity to transfer proteins, lipids and nucleic acids, thereby influencing various physiological and pathological functions of both recipient and parent cells. While intensive investigation has targeted the role of EVs in different pathological processes, for example, in cancer and autoimmune diseases, the EV-mediated maintenance of homeostasis and the regulation of physiological functions have remained less explored. Here, we provide a comprehensive overview of the current understanding of the physiological roles of EVs, which has been written by crowd-sourcing, drawing on the unique EV expertise of academia-based scientists, clinicians and industry based in 27 European countries, the United States and Australia. This review is intended to be of relevance to both researchers already working on EV biology and to newcomers who will encounter this universal cell biological system. Therefore, here we address the molecular contents and functions of EVs in various tissues and body fluids from cell systems to organs. We also review the physiological mechanisms of EVs in bacteria, lower eukaryotes and plants to highlight the functional uniformity of this emerging communication system. [ABSTRACT FROM AUTHOR]

Background: Coral reefs worldwide are being harmed through anthropogenic activities. Some coral reefs in Thailand remain well-preserved, including the shallow coral reefs along Kra island, Nakhon Si Thammarat province. Interestingly, the microbial community in this environment remains unknown. The present study identified biodiversity of prokaryotes and eukaryotes of 0.22-30 μm in sizes and their metabolic potentials in this coral reef surface in summer and winter seasons, using 16S and 18S rRNA genes pyrosequencing. Results: The marine microbial profiles in summer and winter seasons comprised mainly of bacteria, in phylum, particular the Proteobacteria. Yet, different bacterial and eukaryotic structures existed between summer and winter seasons, supported by low Lennon and Yue & Clayton theta similarity indices (8.48-10.43% for 16S rRNA, 0.32-7.81% for 18S rRNA ). The topmost prokaryotic phylum for the summer was Proteobacteria (99.68%), while for the winter Proteobacteria (62.49%) and Bacteroidetes (35.88%) were the most prevalent. Uncultured bacteria in phyla Cyanobacteria, Planctomycetes, SAR406 and SBR1093 were absent in the summer. For eukaryotic profiles, species belonging to animals predominated in the summer, correlating with high animal activities in the summer, whereas dormancy and sporulation predominated in the winter. For the winter, eukaryotic plant species predominated and several diverse species were detected. Moreover, comparison of our prokaryotic databases in summer and winter of Kra reef surface against worldwide marine culture-independent prokaryotic databases indicated our databases to most resemblance those of coastal Sichang island, Chonburi province, Thailand, and the 3 tropical GOS sites close to Galapagos island (GS039, GS040 and GS045), in orderly. Conclusions: The study investigated and obtained culture-independent databases for marine prokaryotes and eukaryotes in summer and winter seasons of Kra reef surface. The data helped understand seasonal dynamics of microbial structures and metabolic potentials of this tropical ecosystem, supporting the knowledge of the world marine microbial biodiversity. [ABSTRACT FROM AUTHOR]