Reclassification of Allomuricauda and Muricauda species as members of the genus Flagellimonas Bae et al. 2007 and emended description of the genus Flagellimonas

The recently proposed genus Allomuricauda Deshmukh and Oren 2023 is illegitimate because it includes the type species of the genera Flagellimonas Bae et al. 2007 and Spongiibacterium Yoon and Oh 2012, contravening Rule 51b(1) of the International Code of Nomenclature of Prokaryotes. As Flagellimonas Bae et al. 2007 is the earlier described genus, we here reclassify 36 species earlier described as belonging to the illegitimate genus Muricauda as species of Flagellimonas. We also present an emended description of the genus Flagellimonas.

Proposal of Allomuricauda gen. nov. and Allofranklinella gen. nov. as replacement names for the illegitimate prokaryotic generic names Muricauda and Franklinella, respectively

The prokaryotic generic names Muricauda Bruns et al. 2001 and Franklinella Bernard et al. 2022 are illegitimate because they are later homonyms of the genus names Muricauda Small 1903 (synonym of Arisaema; Tracheophyta - Liliopsida - Araceae) and Franklinella Stewart and Hendrix 1945 (a Devonian ostracod genus) and Franklinella Lenz 1973 (a Devonian brachiopod genus), respectively (Principle 2 and Rule 51b(4) of the International Code of Nomenclature of Prokaryotes). We therefore propose the replacement generic names Allomuricauda and Allofranklinella, with type species Allomuricauda ruestringensis and Allofrankinella schreckenbergeri, respectively.

Muricauda meishanensis sp. nov., a facultative anaerobic bacterium belonging to the family Flavobacteriaceae isolated from marine sediment in the East China Sea

A facultative anaerobic, Gram-strain-negative, rod-shaped bacterium (strain NBU2970T) was isolated by using modified ichip in situ cultivation from a marine sediment sample collected from Meishan Island in the East China Sea. Strain NBU2970T grew optimally at 37 °C, with a NaCl concentration of 2.0 % (w/v) and at pH 7.0. The 16S rRNA gene sequence analyses revealed that strain NBU2970T represents a novel species with the genus Muricauda, sharing highest sequence identities with Muricauda beolgyonensis BB-My12T (96.1 %), Muricauda alvinocaridis SCR12T (96.0 %), Muricauda taeanensis 105T (96.0 %) and Muricauda ruestringensis B1T (95.6 %). Phylogenetic analyses also indicated that strain NBU2970T clustered with the genus Muricauda and was closely related to M. beolgyonensis BB-My12T and M. ruestringensis B1T. The draft genome sequence of strain NBU2970T was composed of six contigs with a size of 3.2 Mbp, containing 3045 protein-coding genes and 38 RNA genes. The DNA G+C content was 43.8 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between strain NBU2970T and related species of the genus Muricauda were well below the threshold limit for prokaryotic species delineation. The major cellular fatty acids were iso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH. The only respiratory quinone was MK-6. The major polar lipid was phosphatidylethanolamine. Based on its phenotypic, chemotaxonomic and genotypic data, strain NBU2970T is considered to be a representative of a novel species in the genus Muricauda, for which the name Muricauda meishanensis sp. nov. is proposed. The type strain is NBU2970T (=KCTC 82915T=MCCC 1K06394T).

Muricauda abyssi sp. nov., a marine bacterium isolated from deep seawater of the Mariana Trench

A Gram-stain-negative, non-motile and rod-shaped bacterium, designated as strain W52^T, was isolated from deep seawater of the Mariana Trench and characterized phylogenetically and phenotypically. The strain could grow at 10-47 °C (optimum 32 °C), at pH 5.0-8.0 (optimum 6.0) and with 0-9% NaCl (optimum 3 %, w/v). The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that W52^T was related to members of the genus Muricauda and shared the highest identity with Muricauda oceani 501str8^T (99.0 %), followed by Muricauda aquimarina JCM 11811^T, Muricauda ruestringensis DSM 13258^T, Muricauda oceanensis 40DY170^T, Muricauda beolgyonensis KCTC 23501^T and Muricauda zhangzhouensis 12C25^T with 97.0-98.8 % sequence similarity. 16S rRNA gene sequence identities between W52^T and other members of the genus Muricauda were below 97.0 %. The major respiratory quinone was MK-6. The polar lipids were phosphatidylethanolamine (PE), one unidentified aminolipid and three unidentified lipids. The strain had iso-C_15 : 0, iso-C_17 : 0 3-OH and iso-C_15 : 1G as the major fatty acids. The G+C content of the genomic DNA was 41.7 %. The combined genotypic and phenotypic data indicated that strain W52^T represents a novel species of the genus Muricauda, for which the name Muricauda abyssi sp. nov. is proposed, with the type strain W52^T (=MCCC 1K05111^T= KCTC 82315^T).

Muricauda aurea sp. nov. and Muricauda profundi sp. nov., two marine bacteria isolated from deep sea sediment of Pacific Ocean

Two novel Gram-stain-negative, aerobic, rod-shaped, carotenoid-pigmented and non-flagellated bacteria, designated BC31-1-A7T and BC31-3-A3T, were isolated from polyethylene-terephthalate-degrading bacterial consortia enriched from deep-sea sediment collected in the Pacific Ocean. Optimal growth of both strains was observed at 28–32 °C, at pH 7.5 and in the presence of 3–4% (w/v) NaCl. The 16S rRNA gene sequence analysis revealed that strains BC31-1-A7T and BC31-3-A3T were closely related to Muricauda aquimarina JCM 11811T, Muricauda lutimaris KCTC 22173T, Muricauda ruestringensis DSM 13258T, Muricauda zhangzhouensis DSM 25030T, Muricauda oceani JCM 33902T and Muricauda oceanensis KCTC 72200T with 96.8–98.9% sequence similarity. The 16S rRNA gene sequence similarity between strains BC31-1-A7T and BC31-3-A3T was 97.5%. The genomic G+C contents of strains BC31-1-A7T and BC31-3-A3T were 42.1 and 41.6 mol%, respectively. The average nucleotide identity and digital DNA–DNA hybridization values between strain BC31-3-A3T, strain BC31-1-A7T and their six closely related type strains were 77.6–84.3% and 20.5–27.9%, respectively. Menaquinone-6 was detected as the major isoprenoid quinone in all strains. Their major fatty acids were iso-C15:0, iso-C15:1 G and iso-C17:0 3-OH. The major polar lipids of strains BC31-1-A7T and BC31-3-A3T were identified as one phosphatidylethanolamine, some unidentified polar lipids and one aminolipid. Based on their distinct taxonomic characteristics, strains BC31-1-A7T and BC31-3-A3T represent two novel species in the genus Muricauda . The names proposed to accommodate these two strains are Muricauda aurea sp. nov. and Muricauda profundi sp. nov., and the type strains are BC31-1-A7T (=MCCC M23246T=KCTC 82569T) and BC31-3-A3T (=MCCC M23216T=KCTC 82302T), respectively.

Muricauda amphidinii sp. nov., a novel marine bacterium isolated from the phycosphere of dinoflagellate Amphidinium carterae

A Gram-stain-negative, aerobic, rod-shaped and non-motile bacterium was isolated from a liquid culture of dinoflagellate Amphidinium carterae and further designated as LMIT004^T. Optimal growth was observed at 25 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. Oxidase and catalase were positive. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LMIT004^T showed high similarities to type strains Muricauda nanhaiensis SM17004^T (96.77 %) and Muricauda aquimarina JCM11811^T (95.60 %) but formed a separate branch in the genus Muricauda. The G+C content of strain LMIT004^T was 39.0 mol%. The dominant fatty acids were iso-C_15 : 0 and iso-C_15 : 1 G. The polar lipids mainly contained phosphatidylethanolamine, five unidentified phospholipids and five unidentified polar lipids. The sole respiratory quinone was menaquinone-6 (MK-6). The draft genome of the type strain was 3.88 Mbp. The average nucleotide identity values between strain LMIT004^T and the two reference strains M. nanhaiensis SM17004^T and M. aquimarina JCM11811^T were 77.47 and 73.49 %, respectively. Based on the polyphasic analysis, strain LMIT004^T is suggested to represent a novel specie in the genus of Muricauda, for which the name Muricauda amphidinii sp. nov. is proposed. The type strain is LMIT004^T (=CICC 24871^T=KCTC 72948^T).

Muricauda sediminis sp. nov., isolated from western Pacific Ocean sediment

A Gram-stain-negative bacterium, designated strain 40Bstr401^T, was isolated from a sediment sample collected from the western Pacific Ocean. Analysis of its 16S rRNA gene sequence revealed that strain 40Bstr401^T belongs to the genus Muricauda and is closely related to type strains Muricauda antarctica Ar-22^T (98.2 %), Muricauda taeanensis 105^T (98.2 %) and Muricauda beolgyonensis BB-My12^T (97.4 %). The average nucleotide identity values for 40Bstr401^T with M. antarctica Ar-22^T and M. taeanensis 105^T are 79.3 % and 78.8 %, respectively. The in silico DNA-DNA hybridization values between strain 40Bstr401^T and M. antarctica Ar-22^T and M. taeanensis 105^T are 26.7 and 26.6 %, respectively. The major isoprenoid quinone of 40Bstr401^T is MK-6, and iso-C_17 : 0 3-OH and iso-C_15 : 0 are the dominant cellular fatty acids. The major polar lipids are phosphatidylethanolamine, four unidentified amino lipids and two unidentified lipids. The G+C content of the genomic DNA is 42.9 mol%. Its phylogenetic distinctiveness and chemotaxonomic differences, together with the phenotypic properties observed in this study, indicate that strain 40Bstr401^T can be differentiated from closely related species. Therefore, we propose strain 40Bstr401^T represents a novel species in the genus Muricauda, for which the name Muricauda sediminis sp. nov. is suggested. The type strain is 40Bstr401^T (=MCCC 1K04568^T=KCTC 82139^T).

Muricauda maritima sp. nov., Muricauda aequoris sp. nov. and Muricauda oceanensis sp. nov., three marine bacteria isolated from seawater

Three Gram-stain-negative, non-motile, rod-shaped strains, designated 72T, NH166T and 40DY170T, were isolated from seawater samples of the West Pacific Ocean, South China Sea and West Pacific Ocean, respectively. The 16S rRNA gene sequence similarity results revealed that strains 72Tand NH166T were most closely related to Muricauda antarctica Ar-22T, Muricauda taeanensis JCM 17757T, Muricauda beolgyonensis KCTC 23501T, Muricauda lutimaris KCTC 22173T and Muricauda hadalis MT-229T with 97.2–98.0% sequence similarity. 16S rRNA gene sequence analysis also indicated that strain 40DY170T was most closely related to Muricauda ruestringensis DSM 13258T, Muricauda aquimarina JCM 11811T, Muricauda lutimaris KCTC 22173T and Muricauda oceani 501str8T with 97.6–98.1% sequence similarity. The 16S rRNA gene sequence similarity values among strains 72T, NH166T and 40DY170T were 96.5–99.2%. Phylogenetic analyses indicated that three new isolates represented three novel species by forming two distinctive lineages within the genus Muricauda . The DNA G+C contents of strain 72T, NH166T and 40DY170T were 43.4, 43.4 and 42.4 mol%, respectively. The average nucleotide identity and in silico DNA–DNA hybridization values between strains 72T, NH166T, 40DY170T and the reference strains were 76.5–93.5% and 19.2–53.5%, respectively. The sole respiratory quinone in all strains was menaquinone-6. Their major fatty acids were iso-C17:0 3-OH, iso-C15:0 and iso-C15 : 1 G. The major polar lipids of strains 72T and NH166T were phosphatidylethanolamine, one unidentified aminolipid and two unidentified lipids. The major polar lipids of strain 40DY170T were phosphatidylglycerol, one unidentified phospholipid, one unidentified aminolipid and two unidentified lipids. On the basis of their distinct taxonomic characteristics, the three isolates represent three novel species of the genus Muricauda , for which the names Muricauda maritima sp. nov. (type strain 72T=KCTC 62229T=MCCC 1K03350T), Muricauda aequoris sp. nov. (NH166T=KCTC 62228T=MCCC 1K03449T) and Muricauda oceanensis sp. nov. (40DY170T=KCTC 72200T=MCCC 1K03569T) are proposed.

Muricauda brasiliensis sp. nov., isolated from a mat-forming cyanobacterial culture

Strain K001 was isolated from a cyanobacterial culture derived from Abrolhos, a reef bank microbial mat (South Atlantic Ocean-Brazil). Cells of K001 are Gram stain-negative, catalase and oxidase-positive, non-motile, rod-shaped, and with or without appendages. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain K001 belongs to the genus Muricauda. The highest strain K001 16S rRNA gene identity, ANI, and dDDH, respectively, are with M. aquimarina (98.90%, 79.23, 21.60%), M. ruestringensis (98.20%, 80.82, 23.40%), and M. lutimaris (97.86%, 79.23, 22.70%). The strain grows at 15-37 °C and between 0.5 and 10% NaCl. The major fatty acids of strain K001 are iso-C_15:0, iso-C_15:1 G, iso-C_17:0 3-OH, and summed feature 3 (C_16:1 ω6c and/or C_16:1 ω7c). The polar lipids are represented by phosphatidylethanolamine, three unidentified aminolipids, and three unidentified polar lipids. The major respiratory quinone is MK-6. The G+C content of the DNA of strain K001 is 41.62 mol%. Based on polyphasic analysis of strain K001, it was identified as a novel representative of the genus Muricauda and was named Muricauda brasiliensis sp. nov. The type strain is K001 (=CBMAI 2315^T = CBAS 752^T).

Muricauda hadalis sp. nov., a novel piezophile isolated from hadopelagic water of the Mariana Trench and reclassification of Muricauda antarctica as a later heterotypic synonym of Muricauda teanensis

A novel marine Gram-stain-negative, non-motile, aerobic and rod-shaped bacterium, designated as strain MT-229T, was isolated from the deep seawater in the Mariana Trench and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 30 °C (ranging 10–40 °C), pH 6 (ranging 3–11) and with 11 % (w/v) NaCl (ranging 0–17 %). Strain MT-229T was a piezophile, growing optimally at 20 MPa (range 0.1–70 MPa). The nearest phylogenetic neighbours were Muricauda antarctica CGMCC 1.2174T and Muricauda taeanensis JCM 17757T with 16S rRNA gene similarity of 98.7 %. The sole respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine (PE), two unidentified aminolipids (AL) and ten unidentified lipids. The major fatty acids of strain MT-229T were iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G. The G+C content of the genomic DNA was 45.6 mol%. The combined genotypic and phenotypic data indicated that strain MT-229T represents a novel species of the genus Muricauda , for which the name Muricauda hadalis sp. nov. is proposed, with the type strain MT-229T (=DSM 109894T=MCCC 1K04201T). In addition, the whole-genome-based comparisons revealed that the type strains of Muricauda antarctica and Muricauda teanensis belong to a single species. It is, therefore, proposed that M. antarctica be recognized as a heterotypic synonym of M. teanensis.

Muricauda oceani sp. nov., isolated from the East Pacific Ocean

A Gram-stain-negative bacterium, designated strain 501str8T, was isolated from a sediment sample collected from the East Pacific Ocean. 16S rRNA gene sequence analysis revealed that strain 501str8T belonged to the genus Muricauda , with closely related type strains Muricauda aquimarina SW-63T (98.5 %), Muricauda lutimaris SMK-108T (98.3 %) and Muricauda ruestringensis B1T (97.9 %). Up-to-date bacterial core gene set analysis revealed that strain 501str8T represented one independent lineage with M. aquimarina SW-63T. The average nucleotide identity values of strain 501str8T with M. aquimarina SW-63T and M. lutimaris SMK-108T were 80.2 and 81.3 %, respectively. In silico DNA–DNA hybridization values between strain 501str8T and M. aquimarina SW-63T and M. lutimaris SMK-108T were 22.8 and 32.9 %, respectively. The predominant isoprenoid quinone was menaquinone-6, and iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G were the dominant cellular fatty acids. The G+C content of the genomic DNA was 42.8 mol%. Differential phylogenetic distinctiveness and chemotaxonomic differences, together with the phenotypic properties observed in this study, revealed that strain 501str8T could be differentiated from closely related species. Therefore, we propose that strain 501str8T represents a novel species of the genus Muricauda , for which the name Muricauda oceani sp. nov. is suggested. The type strain is 501str8T (=JCM 33902T=MCCC 1K04567T).

Flavobacterium sharifuzzamanii sp. nov., Isolated from the Sediments of the East China Sea

A novel bacterial strain A7.6^T was isolated from the sediments collected near the Zhairuo Island located in the East China Sea and characterized using a polyphasic approach. Cells were Gram-stain-negative, rod-shaped, non-spore forming, non-flagellated but motile by gliding. The strain was aerobic, positive for oxidase and catalase activities. The strain can grow at 4-35 °C, pH 5.5-9.0, and 0-3% (w/v) NaCl concentration. The major polar lipid was phosphatidylethanolamine, the predominant fatty acids (> 10%) were iso-C_15:0 and summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c). The genomic G+C content was 33.6 mol% and the major respiratory quinone was menaquinone 6. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain A7.6^T belonged to the genus Flavobacterium and was closely related to Flavobacterium tistrianum GB 56.1^T (98.4% similarity), F. nitrogenifigens NXU-44^T (98.4%), F. ginsenosidimutans THG 01^T (98.0%) and F. anhuiense D3^T (97.7%). Average nucleotide identities and digital DNA-DNA hybridizations values for genomes ranged from 75.9 to 91.4% and 21.4 to 43.9% between strain A7.6^T and its closest phylogenetic neighbors. The polyphasic characterization indicated that strain A7.6^T represented a novel species of the genus Flavobacterium, for which the name Flavobacterium sharifuzzamanii is proposed. The type strain is A7.6^T (= KCTC 62405^T = MCCC 1K03485^T). The NCBI GenBank accession number for the 16S rRNA gene of A7.6^T is MH396692, and for the genome sequence is QJGZ00000000. The digital protologue database (DPD) Taxon Number is TA00643.

PBN11-8, a Cytotoxic Polypeptide Purified from Marine Bacillus, Suppresses Invasion and Migration of Human Hepatocellular Carcinoma Cells by Targeting Focal Adhesion Kinase Pathways

The development of antitumor drugs has attracted cancer researchers and the identification of novel antitumor lead compounds is certainly of great interest. The fermentation broth of Bacillus sp. N11-8, which was isolated from the Antarctic waters, showed cytotoxicity towards different cells. A cytotoxic polypeptide, PBN11-8, was purified from the fermentation broth of Bacillus sp. N11-8 using ultrafiltration, ammonium sulfate precipitation, anion exchange liquid chromatography and high performance liquid chromatography (HPLC). Cloning and sequence analysis showed that PBN11-8 polypeptide (MW: ~19 kDa by the electrospray-ionization (ESI)) displayed high similarity with peptidase M84 from Bacillus pumilus. PBN11-8 possessed moderate cytotoxicity towards several cancer cell lines with IC₅₀ values of 1.56, 1.80, 1.57, and 1.73 µg/mL against human hepatocellular carcinoma cell line BEL-7402, human renal clear cell adenocarcinoma cell line 786-0, human hepatocellular carcinoma cell line HepG2, and human pancreatic cancer cell line Panc-28, respectively. Moreover, the polypeptide displayed weak cytotoxicity towards normal cell line renal tubular epithelial cell line HK2 and human normal liver cell line L02 cells. Wound healing migration and Transwell experiments demonstrate that PBN11-8 could inhibit the migration and invasion of BEL-7402. Further investigation revealed that PBN11-8 suppresses focal adhesion kinase (FAK)-mediated adhesion, migration, and invasion by disturbing FAK/extracellular regulated protein kinases (ERK) signaling and matrix metalloproteinase-2(MMP-2) and matrix metalloproteinase-9 (MMP-9) in BEL-7402 cells. Thus, PBN11-8 represents a potential novel anti-cancer lead compound.

UV-Protective Compounds in Marine Organisms from the Southern Ocean

Solar radiation represents a key abiotic factor in the evolution of life in the oceans. In general, marine, biota-particularly in euphotic and dysphotic zones-depends directly or indirectly on light, but ultraviolet radiation (UV-R) can damage vital molecular machineries. UV-R induces the formation of reactive oxygen species (ROS) and impairs intracellular structures and enzymatic reactions. It can also affect organismal physiologies and eventually alter trophic chains at the ecosystem level. In Antarctica, physical drivers, such as sunlight, sea-ice, seasonality and low temperature are particularly influencing as compared to other regions. The springtime ozone depletion over the Southern Ocean makes organisms be more vulnerable to UV-R. Nonetheless, Antarctic species seem to possess analogous UV photoprotection and repair mechanisms as those found in organisms from other latitudes. The lack of data on species-specific responses towards increased UV-B still limits the understanding about the ecological impact and the tolerance levels related to ozone depletion in this region. The photobiology of Antarctic biota is largely unknown, in spite of representing a highly promising reservoir in the discovery of novel cosmeceutical products. This review compiles the most relevant information on photoprotection and UV-repair processes described in organisms from the Southern Ocean, in the context of this unique marine polar environment.

Gracilimonas amylolytica sp. nov., isolated from deep-sea sediment

A Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated LA399^T, was isolated from deep-sea sediment collected from the Pacific Ocean. Cells of strain LA399^T grew in the medium containing 0-10.0 % of NaCl (w/v; optimum 3.0-5.0 %), pH 6.5-8.0 (optimum 7.0) and 20-40 °C (optimum 37 °C). Aesculin, gelatin, starch and Tween 80 were hydrolysed. Strain LA399^T was closely related to Gracilimonas halophila WDS2C40^T (97.0 % sequence similarity), Gracilimonas mengyeensis YIM J14^T (96.4 %), Gracilimonas rosea CL-KR2^T (96.4 %) and Gracilimonas tropica DSM 19535^T (96.0 %), and exhibited equal or less than 96.0 % sequence similarity to other type strains of species with validly published names. Phylogenetic analyses revealed that strain LA399^T clustered with the clade comprising the Gracilimonas species and formed an independent lineage. Strain LA399^T contained menaquinone 7 as the sole isoprenoid quinone and iso-C15 : 0, anteiso-C15 : 0, summed feature 3 (C16 : 1ω7c/C16 : 1ω6c) and summed feature 9 (iso-C17 : 1ω9c/10-methyl C16 : 0) as the predominant cellular fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified phospholipid and three unidentified glycolipids. The DNA G+C content was 45.3 mol%. According to the phylogenetic, chemotaxonomic and phenotypic data, it represents a novel species of the genus Gracilimonas, for which the name Gracilimonas amylolytica is proposed. The type strain is LA399^T (=CGMCC 1.16248^T=KCTC 52885^T).

Revised phylogeny of Bacteroidetes and proposal of sixteen new taxa and two new combinations including Rhodothermaeota phyl. nov

Members of the phylum Bacteroidetes, which was originally defined as a monophyletic branch encompassing the genera Cytophaga, Flavobacterium and Bacteroides (CFB), are widely studied due to their importance in environmental and gut microbiology. As a consequence, the number of species names with standing in nomenclature has doubled in the past five years. In this study, a revision of an earlier phylogeny of Bacteroidetes has been performed using the 16S rRNA gene as a backbone in combination with the 23S rRNA gene, as well as multilocus sequence analysis (MLSA) of 29 orthologous protein sequences, and indels in the sequences of the beta subunit of the F-type ATPase and the alanyl-tRNA synthetase. In addition, taxonomic data for Bacteroidetes has been updated by considering the orphan species list, signature nucleotides in the 16S rRNA sequence, the list of outlier species, and discrepancies with the current taxonomy at the genus rank level. As a result, seven new taxa are proposed within Bacteroidetes (Chitinophagia classis nov., Chitinophagales ord. nov., Crocinitomicaceae fam. nov., Odoribacteraceae fam. nov., Hymenobacteraceae fam. nov., Thermonemataceae fam. nov. and Persicobacteraceae fam. nov.), as well as one new phylum Rhodothermaeota phyl. nov. that contains two classes, two orders, four families and a new genus with two new combinations.

Xanthomarina gelatinilytica gen. nov., sp. nov., isolated from seawater

A novel Gram-stain-negative, rod-shaped, yellow-pigmented, non-sporulating, non-motile bacterium, designated strain AK20T, was isolated from seawater collected from Kochi city, Kerala state, India. Colonies on marine agar were circular, yellow, shiny, translucent, 2-3 mm in diameter, convex and with entire margin. Flexirubin-type pigment was present. The fatty acids were dominated by iso-branched units with a high abundance of iso-C15:0, iso-C15:1 G, iso-C17:0 3-OH, summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH) and iso-C15:0 3-OH. Polar lipids included phosphatidylethanolamine, two unidentified aminophospholipids, two unidentified phospholipids and four unidentified lipids. Menaquinone 6 (MK-6) was the predominant respiratory quinone. The DNA G+C content of strain AK20T was 38.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AK20T was closely related to Formosa spongicola A2T and Bizionia paragorgiae KMM 6029T (pair-wise sequence similarities of 95.9 and 95.7%, respectively), forming a distinct branch within the family Flavobacteriaceae and clustering with the clade comprising species of the genus Bizionia. Based on phenotypic and chemotaxonomic characteristics and phylogenetic analysis, strain AK20T is different from the existing genera in the family Flavobacteriaceae, and is therefore considered to represent a novel species of a new genus, for which the name Xanthomarina gelatinilytica gen. nov., sp. nov. is proposed. The type strain of Xanthomarina gelatinilytica is AK20T ( = MTCC 11705T = JCM 18821T).

Muricauda pacifica sp. nov., isolated from seawater of the South Pacific Gyre

A Gram-stain-negative, strictly aerobic, non-flagellated, non-gliding, oxidase- and catalase-positive, rod-shaped and orange-pigmented bacterium with appendages, designated strain SW027T, was isolated from a surface seawater sample collected from the South Pacific Gyre (26° 29′ S 137° 56′ W) during the Integrated Ocean Drilling Program (IODP) Expedition 329. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SW027T shared the highest sequence similarity with members of the genus Muricauda (94.3–92.7 %), exhibiting 94.3 % sequence similarity to Muricauda flavescens SW-62T. Optimal growth occurred in the presence of 3 % (w/v) NaCl, at pH 7.0 and at 37 °C. The DNA G+C content of strain SW027T was 42.7 mol%. The major fatty acids were iso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH. The major respiratory quinone was menaquinone-6. The major polar lipids were phosphatidylethanolamine and two unidentified lipids. Enzymic activity profiles, cell morphology and DNA G+C content differentiated the novel bacterium from the most closely related members of the genus Muricauda. On the basis of the polyphasic analyses, strain SW027T is considered to represent a novel species of the genus Muricauda, for which the name Muricauda pacifica sp. nov. is proposed. The type strain is SW027T ( = JCM 17861T = LMG 26637T).

Screening of microorganisms from Antarctic surface water and cytotoxicity metabolites from Antarctic microorganisms

The Antarctic is a potentially important library of microbial resources and new bioactive substances. In this study, microorganisms were isolated from surface water samples collected from different sites of the Antarctic. 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide (MTT) assay‐based cytotoxicity‐tracking method was used to identify Antarctic marine microorganism resources for antitumor lead compounds. The results showed that a total of 129 Antarctic microorganism strains were isolated. Twelve strains showed potent cytotoxic activities, among which a Gram‐negative, rod‐shaped bacterium, designated as N11‐8 was further studied. Phylogenetic analysis based on 16S rRNA gene sequence showed that N11‐8 belongs to the genus Bacillus. Fermented active products of N11‐8 with molecular weights of 1–30 kDa had higher inhibitory effects on different cancaer cells, such as BEL‐7402 human hepatocellular carcinoma cells, U251 human glioma cells, RKO human colon carcinoma cells, A549 human lung carcinoma cells, and MCF‐7 human breast carcinoma cells. However, they displayed lower cytotoxicity against HFL1 human normal fibroblast lung cells. However, they displayed lower cytotoxicity against HFL1 human normal fibroblast lung cells. Microscopic observations showed that the fermented active products have inhibitory activity on BEL‐7402 cells similar to that of mitomycin C. Further studies indicated that the fermented active products have high pH and high thermal stability. In conclusion, most strains isolated in this study may be developed as promising sources for the discovery of antitumor bioactive substances. The fermented active products of Antarctic marine Bacillus sp. N11‐ 8 are expected to be applied in the prevention and treatment of cancer.

Oceanicola antarcticus sp. nov. and Oceanicola flagellatus sp. nov., moderately halophilic bacteria isolated from seawater

Two Gram-stain-negative, aerobic, moderately halophilic, rod-shaped bacteria (strains Ar-45T and DY470T) were isolated from seawater collected from the Southern Ocean and the Pacific Ocean, respectively. Growth of strain Ar-45T was observed with between 0.5 and 10.0 % (w/v) NaCl (optimally with 0.5–3.0 %) and between pH 5.5 and 9.5. Strain DY470T grew in the presence of 0.5–7.5 % (w/v) NaCl (optimally with 2.0 %) and at pH 5.5–8.5. Chemotaxonomic analysis showed Q-10 as the respiratory quinone for both strains. The major fatty acids (>5 %) of strain Ar-45T were C16 : 0, C19 : 0 cyclo ω8c and C18 : 1ω7c, while those of strain DY470T were C18 : 1ω7c, C16 : 0 and 11-methyl C18 : 1ω7c. The DNA G+C contents of the two strains were 62.0 and 61.8 mol%, respectively. Phylogenetic analyses based on 16S rRNA gene sequences showed that strains Ar-45T and DY470T were related most closely to the genus Oceanicola , with sequence similarities of 97.4–94.0 and 97.7–94.7 %, respectively. The DNA–DNA hybridization value between strain Ar-45T and Oceanicola marinus LMG 23705T was 22.0 %. Levels of DNA–DNA relatedness between strain DY470T and Oceanicola nitratireducens LMG 24663T and Oceanicola batsensis DSM 15984T were 32.5 and 26.1 %, respectively. Based on phylogenetic, chemotaxonomic and phenotypic data, strains Ar-45T and DY470T are considered to represent two novel species of the genus Oceanicola , for which the names Oceanicola antarcticus (type strain Ar-45T = CGMCC 1.12662T = LMG 27868T) and Oceanicola flagellatus (type strain DY470T = CGMCC 1.12664T = LMG 27871T) are proposed.