Kordia periserrulae sp. nov., isolated from a marine polychaete Periserrula leucophryna, and emended description of the genus Kordia

Taxonomic identification and temperature stress tolerance mechanisms of Aequorivita marisscotiae sp. nov

The deep sea harbours microorganisms with unique life characteristics and activities due to adaptation to particular environmental conditions, but the limited sample collection and pure culture techniques available constrain the study of deep-sea microorganisms. In this study, strain Ant34-E75 was isolated from Antarctic deep-sea sediment samples and showed the highest 16 S rRNA gene sequence similarity (97.18%) with the strain Aequorivita viscosa 8-1bT. Strain Ant34-E75 is psychrotrophic and can effectively increase the cold tolerance of Chlamydomonas reinhardtii (a model organism). Subsequent transcriptome analysis revealed multiple mechanisms involved in the Ant34-E75 response to temperature stress, and weighted gene co-expression network analysis (WGCNA) showed that the peptidoglycan synthesis pathway was the key component. Overall, this study provides insights into the characteristics of a deep-sea microorganism and elucidates mechanisms of temperature adaptation at the molecular level.

Kordia aestuariivivens sp. nov. and Olleya sediminilitoris sp. nov., isolated from a tidal flat

Two Gram-stain-negative and non-flagellated bacteria, YSTF-M3^T and YSTF-M6^T, were isolated from a tidal flat from Yellow Sea, Republic of Korea, and subjected to a polyphasic taxonomic study. Neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strains YSTF-M3^T and YSTF-M6^T belong to the genera Kordia and Olleya of the family Flavobacteriaceae, respectively. The 16S rRNA gene sequence similarities between strain YSTF-M3^T and the type strains of Kordia species and between strain YSTF-M6^T and the type strains of Olleya species were 94.1-98.4 and 97.3-98.3 %, respectively. The ANI and dDDH values between genomic sequences of strain YSTF-M3^T and the type strains of five Kordia species and between those of strain YSTF-M6^T and the type strains of three Olleya species were in ranges of 77.0-83.2 and 20.7-27.1 % and 79.4-81.5 and 22.3-23.9 %, respectively. The DNA G+C contents of strain YSTF-M3^T and YSTF-M6^T from genomic sequences were 34.1 and 31.1 %, respectively. Both strains contained MK-6 as predominant menaquinone and phosphatidylethanolamine as only major phospholipid identified. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strains YSTF-M3^T and YSTF-M6^T are separated from recognized species of the genera Kordia and Olleya, respectively. On the basis of the data presented, strains YSTF-M3^T (=KACC 21639^T=NBRC 114499^T) and YSTF-M6^T (=KACC 21640^T=NBRC 114500^T) are considered to represent novel species of the genera Kordia and Olleya, respectively, for which the names Kordia aestuariivivens sp. nov. and Olleya sediminilitoris sp. nov. are proposed.

Bacterial avidins are a widely distributed protein family in Actinobacteria, Proteobacteria and Bacteroidetes

BACKGROUND

Avidins are biotin-binding proteins commonly found in the vertebrate eggs. In addition to streptavidin from Streptomyces avidinii, a growing number of avidins have been characterized from divergent bacterial species. However, a systematic research concerning their taxonomy and ecological role has never been done. We performed a search for avidin encoding genes among bacteria using available databases and classified potential avidins according to taxonomy and the ecological niches utilized by host bacteria.

RESULTS

Numerous avidin-encoding genes were found in the phyla Actinobacteria and Proteobacteria. The diversity of protein sequences was high and several new variants of genes encoding biotin-binding avidins were found. The living strategies of bacteria hosting avidin encoding genes fall mainly into two categories. Human and animal pathogens were overrepresented among the found bacteria carrying avidin genes. The other widespread category were bacteria that either fix nitrogen or live in root nodules/rhizospheres of plants hosting nitrogen-fixing bacteria.

CONCLUSIONS

Bacterial avidins are a taxonomically and ecologically diverse group mainly found in Actinobacteria, Proteobacteria and Bacteroidetes, associated often with plant invasiveness. Avidin encoding genes in plasmids hint that avidins may be horizontally transferred. The current survey may be used as a basis in attempts to understand the ecological significance of biotin-binding capacity.

Genome characteristics of Kordia antarctica IMCC3317T and comparative genome analysis of the genus Kordia

The genus Kordia is one of many genera affiliated with the family Flavobacteriaceae of the phylum Bacteroidetes, well known for its degradation of high molecular weight organic matters. The genus Kordia currently comprises eight species, type strains of which have been isolated from a diverse range of marine environments. As of this report, four genome sequences have been submitted for cultured strains of Kordia, but none are complete nor have they been analyzed comprehensively. In this study, we report the complete genome of Kordia antarctica IMCC3317^T, isolated from coastal seawater off the Antarctic Peninsula. The complete genome of IMCC3317^T consists of a single circular chromosome with 5.5 Mbp and a 33.2 mol% of G+C DNA content. The IMCC3317^T genome showed features typical of chemoheterotrophic marine bacteria and similar to other Kordia genomes, such as complete gene sets for the Embden–Meyerhof–Parnas glycolysis pathway, tricarboxylic acid cycle and oxidative phosphorylation. The genome also encoded many carbohydrate-active enzymes, some of which were clustered into approximately seven polysaccharide utilization loci, thereby demonstrating the potential for polysaccharide utilization. Finally, a nosZ gene encoding nitrous oxide reductase, an enzyme that catalyzes the reduction of N₂O to N₂ gas, was also unique to the IMCC3317^T genome.

Ecological and functional capabilities of an uncultured Kordia sp

Cultivable bacteria represent only a fraction of the diversity in microbial communities. However, the official procedures for classification and characterization of a novel prokaryotic species still rely on isolates. Nevertheless, due to single cell genomics, it is possible to retrieve genomes from environmental samples by sequencing them individually, and to assign specific genes to a specific taxon, regardless of their ability to grow in culture. In this study, a complete description was performed for uncultured Kordia sp. TARA_039_SRF, a proposed novel species within the genus Kordia, using culture-independent techniques. The type material was a high-quality draft genome (94.97% complete, 4.65% gene redundancy) co-assembled using ten nearly identical single amplified genomes (SAGs) from surface seawater in the North Indian Ocean during the Tara Oceans Expedition. The assembly process was optimized to obtain the best possible assembly metrics and a less fragmented genome. The closest relative of the species was Kordia periserrulae, which shared 97.56% similarity of the 16S rRNA gene, 75% orthologs and 89.13% average nucleotide identity. The functional potential of the proposed novel species included proteorhodopsin, the ability to incorporate nitrate, cytochrome oxidases with high affinity for oxygen, and CAZymes that were unique features within the genus. Its abundance at different depths and size fractions was also evaluated together with its functional annotation, revealing that its putative ecological niche could be particles of phytoplanktonic origin. It could putatively attach to these particles and consume them while sinking to the deeper and oxygen depleted layers of the North Indian Ocean.

Analysis of 1,000 Type-Strain Genomes Improves Taxonomic Classification of Bacteroidetes

Although considerable progress has been made in recent years regarding the classification of bacteria assigned to the phylum Bacteroidetes, there remains a need to further clarify taxonomic relationships within a diverse assemblage that includes organisms of clinical, piscicultural, and ecological importance. Bacteroidetes classification has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees and a limited number of phenotypic features. Here, draft genome sequences of a greatly enlarged collection of genomes of more than 1,000 Bacteroidetes and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa proposed long ago such as Bacteroides, Cytophaga, and Flavobacterium but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which can be considered valuable taxonomic markers. We detected many incongruities when comparing the results of the present study with existing classifications, which appear to be caused by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. The few significant incongruities found between 16S rRNA gene and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences and the impediment in using ordinary bootstrapping in phylogenomic studies, particularly when combined with too narrow gene selections. While a significant degree of phylogenetic conservation was detected in all phenotypic characters investigated, the overall fit to the tree varied considerably, which is one of the probable causes of misclassifications in the past, much like the use of plesiomorphic character states as diagnostic features.

Genome Sequence of Kordia sp. Strain SMS9 Identified in a Non-Axenic Culture of the Diatom Skeletonema marinoi

Initial efforts to sequence the genome of the marine diatom Skeletonema marinoi were hampered by the presence of genetic material from bacteria, and there was sufficient material from some of these bacteria to enable the assembly of full chromosomes. Here, we report the genome of strain SMS9, one such bacterial species identified in a non-axenic culture of S. marinoi strain ST54. Its 5,482,391 bp circular chromosome contains 4,641 CDSs, and has a G+C content of 35.6%. Based on 16S rRNA comparison, phylotaxonomic analysis, and the genome similarity metrics dDDH and OrthoANI, we place this strain in the genus Kordia, and to the best of our knowledge, this is the first Kordia species to be initially described from European waters. As attempts to culture this strain have failed, however, the specifics of its relationship with S. marinoi are still uncertain.

Architecture and Evolution of Blade Assembly in β-propeller Lectins

Lectins with a β-propeller fold bind glycans on the cell surface through multivalent binding sites and appropriate directionality. These proteins are formed by repeats of short domains, raising questions about evolutionary duplication. However, these repeats are difficult to detect in translated genomes and seldom correctly annotated in sequence databases. To address these issues, we defined the blade signature of the five types of β-propellers using 3D-structural data. With these templates, we predicted 3,887 β-propeller lectins in 1,889 species and organized this information in a searchable online database. The data reveal a widespread distribution of β-propeller lectins across species. Prediction also emphasizes multiple architectures and led to the discovery of a β-propeller assembly scenario. This was confirmed by producing and characterizing a predicted protein coded in the genome of Kordia zhangzhouensis. The crystal structure uncovers an intermediate in the evolution of β-propeller assembly and demonstrates the power of our tools.

Exploring Microdiversity in Novel Kordia sp. (Bacteroidetes) with Proteorhodopsin from the Tropical Indian Ocean via Single Amplified Genomes

Marine Bacteroidetes constitute a very abundant bacterioplankton group in the oceans that plays a key role in recycling particulate organic matter and includes several photoheterotrophic members containing proteorhodopsin. Relatively few marine Bacteroidetes species have been described and, moreover, they correspond to cultured isolates, which in most cases do not represent the actual abundant or ecologically relevant microorganisms in the natural environment. In this study, we explored the microdiversity of 98 Single Amplified Genomes (SAGs) retrieved from the surface waters of the underexplored North Indian Ocean, whose most closely related isolate is Kordia algicida OT-1. Using Multi Locus Sequencing Analysis (MLSA) we found no microdiversity in the tested conserved phylogenetic markers (16S rRNA and 23S rRNA genes), the fast-evolving Internal Transcribed Spacer and the functional markers proteorhodopsin and the beta-subunit of RNA polymerase. Furthermore, we carried out a Fragment Recruitment Analysis (FRA) with marine metagenomes to learn about the distribution and dynamics of this microorganism in different locations, depths and size fractions. This analysis indicated that this taxon belongs to the rare biosphere, showing its highest abundance after upwelling-induced phytoplankton blooms and sinking to the deep ocean with large organic matter particles. This uncultured Kordia lineage likely represents a novel Kordia species (Kordia sp. CFSAG39SUR) that contains the proteorhodopsin gene and has a widespread spatial and vertical distribution. The combination of SAGs and MLSA makes a valuable approach to infer putative ecological roles of uncultured abundant microorganisms.

Whole gut microbiome composition of damselfish and cardinalfish before and after reef settlement

The Pomacentridae (damselfish) and Apogonidae (cardinalfish) are among the most common fish families on coral reefs and in the aquarium trade. Members of both families undergo a pelagic larvae phase prior to settlement on the reef, where adults play key roles in benthic habitat structuring and trophic interactions. Fish-associated microbial communities (microbiomes) significantly influence fish health and ecology, yet little is known of how microbiomes change with life stage. We quantified the taxonomic (16S rRNA gene) composition of whole gut microbiomes from ten species of damselfish and two species of cardinalfish from Lizard Island, Australia, focusing specifically on comparisons between pelagic larvae prior to settlement on the reef versus post-settlement juvenile and adult individuals. On average, microbiome phylogenetic diversity increased from pre- to post-settlement, and was unrelated to the microbial composition in the surrounding water column. However, this trend varied among species, suggesting stochasticity in fish microbiome assembly. Pre-settlement fish were enriched with bacteria of the Endozoicomonaceae, Shewanellaceae, and Fusobacteriaceae, whereas settled fish harbored higher abundances of Vibrionaceae and Pasteurellaceae. Several individual operational taxonomic units, including ones related to Vibrio harveyi, Shewanella sp., and uncultured Endozoicomonas bacteria, were shared between both pre and post-settlement stages and may be of central importance in the intestinal niche across development. Richness of the core microbiome shared among pre-settlement fish was comparable to that of settled individuals, suggesting that changes in diversity with adulthood are due to the acquisition or loss of host-specific microbes. These results identify a key transition in microbiome structure across host life stage, suggesting changes in the functional contribution of microbiomes over development in two ecologically dominant reef fish families.

Kordia zhangzhouensis sp. nov., isolated from surface freshwater

An aerobic, Gram-stain-negative, rod-shaped and non-motile bacterium, JS14SB-1T, was isolated from the surface freshwater of the Jiulong River, PR China. Strain JS14SB-1T grew at 15–38 °C (optimum, 28–35 °C), at pH 6.0–9.0 (optimum pH 7.0) and in the presence of 1.0–7.0 % (w/v) NaCl [optimum 3.0–5.0 % (w/v)]. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that strain JS14SB-1T was affiliated to the genus Kordia, sharing low similarities (95.1–97.1 %) to all type strains of species of this genus. The digital DNA–DNA hybridization (DDH) value between strain JS14SB-1T and the closely related strain Kordia jejudonensis SSK3-3T was 20.70 ± 2.33 % and far below the 70 % DDH value taken as the gold standard for delineation of bacterial species. The major fatty acids were identified as iso-C15 : 0 and iso-C17 : 0 3-OH. The polar lipids were phosphatidylethanolamine, glycolipid, aminolipid, several unidentified phospholipids and lipids. The predominant menaquinone was MK-6. The G+C content of the genomic DNA was 33.8 mol%. Based on the phenotypic, phylogenetic and chemotaxonomic distinctiveness, strain JS14SB-1T is considered to represent a novel species of the genus Kordia, for which the name Kordia zhangzhouensis sp. nov. is proposed; the type strain is JS14SB-1T ( = MCCC 1A00726T = KCTC 42140T).

Kordia aquimaris sp. nov., a zeaxanthin-producing member of the family Flavobacteriaceae isolated from surface seawater, and emended description of the genus Kordia

A Gram-staining-negative, strictly aerobic, rod-shaped, non-flagellated, non-spore-forming and gliding marine bacterium designated strain CC-AMZ-301T was isolated from coastal surface seawater near Taichung harbour, Taiwan. Strain CC-AMZ-301T predominantly synthesized zeaxanthin and thus formed yellow colonies on marine agar. The novel strain showed high pairwise 16S rRNA gene sequence similarity to Kordia periserrulae IMCC1412T (95.0 %), K. algicida KCTC 8814PT (94.4 %) and K. antarctica IMCC3317T (94.2 %), and formed a phylogenetic lineage tightly associated with species of the genus Kordia . The polar lipid profile of strain CC-AMZ-301T consisted of three unidentified lipids, three unidentified aminolipids and one unidentified phospholipid. The major fatty acids (>5 % of total) were iso-C17 : 0 3-OH, iso-C15 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 9 (iso-C17 : 1ω9c and/or 10-methyl C16 : 0). The DNA G+C content was 36.4 mol%. Menaquinone 6 (MK-6) was the predominant respiratory quinone. The major polyamine was the triamine sym-homospermidine. Based on evidence from the present polyphasic study, strain CC-AMZ-301T is proposed to represent a novel species of the genus Kordia , for which the name Kordia aquimaris sp. nov. is proposed; the type strain is CC-AMZ-301T ( = JCM 18556T = BCRC 80464T). An emended description of the genus Kordia is also proposed.

Kordia jejudonensis sp. nov., isolated from the junction between the ocean and a freshwater spring, and emended description of the genus Kordia

A Gram-staining-negative, aerobic, non-spore-forming, non-flagellated, non-gliding and rod-shaped bacterial strain, SSK3-3(T), was isolated from the zone where the ocean and a freshwater spring meet at Jeju island, South Korea. Strain SSK3-3(T) grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 2.0% (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences revealed that strain SSK3-3(T) clustered with the type strains of species of the genus Kordia, with which it exhibited 96.5-97.2% 16S rRNA gene sequence similarity. Sequence similarities to the type strains of other recognized species were less than 92.2%. Strain SSK3-3(T) contained MK-6 as the predominant menaquinone and iso-C(15 : 0), iso-C(17 : 0) 3-OH, iso-C(15 : 0) 3-OH and summed feature 3 (C(16 : 1)ω7c and/or C(16 : 1)ω6c) as the major fatty acids. The major polar lipids of strain SSK3-3(T) were phosphatidylethanolamine, one unidentified lipid and one unidentified glycolipid. The DNA G+C content of strain SSK3-3(T) was 34.9 mol% and the mean DNA-DNA relatedness with Kordia periserrulae KACC 14311(T) was 12%. The differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain SSK3-3(T) is separate from other species of the genus Kordia. On the basis of the data presented, strain SSK3-3(T) is considered to represent a novel species of the genus Kordia, for which the name Kordia jejudonensis sp. nov. is proposed. The type strain is SSK3-3(T) ( = KCTC 32426(T) = CECT 8368(T)). An emended description of the genus Kordia is also provided.

Kordia antarctica sp. nov., isolated from Antarctic seawater

A Gram-staining-negative, chemoheterotrophic, yellow-pigmented, non-motile, flexirubin-negative, facultatively anaerobic bacterium, designated strain IMCC3317T, was isolated from a coastal seawater sample from the Antarctic Penninsula. Optimal growth of strain IMCC3317T was observed at 20 °C, pH 8.0 and in the presence of 2–3 % NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain IMCC3317T belonged to the genus Kordia and was closely related to Kordia algicida OT-1T (96.7 % sequence similarity) and Kordia periserrulae IMCC1412T (96.1 % sequence similarity). The major fatty acids were 10-methyl C16 : 0 and/or iso-C16 : 1ω9c, iso-C17 : 0 3-OH, iso-C15 : 0 and anteiso-C15 : 0. The G+C content of the genomic DNA was 35.1 mol%. The strain contained menaquinone-6 (MK-6) as the respiratory quinone. The polar lipids detected in the strain were phosphatidylethanolamine and unknown aminophospholipids, aminolipids and polar lipids. On the basis of phylogenetic distinction and differential phenotypic characteristics, it is suggested that strain IMCC3317T ( = KCTC 32292T = NBRC 109401T) be assigned to the genus Kordia as the type strain of a novel species, for which the name Kordia antarctica sp. nov. is proposed.

Genome sequence of the algicidal bacterium Kordia algicida OT-1

Kordia algicida OT-1 is an algicidal bacterium against the bloom-forming microalgae. The genome sequence of K. algicida revealed a number of interesting features, including the degradation of macromolecules, the biosynthesis of carotenoid pigment and secondary metabolites, and the capacity for gliding motility, which might facilitate the understanding of algicidal mechanisms.