Kangiella shandongensis sp. nov., a novel species isolated from saltern in Yantai, China

A Gram-stain-negative, wheat, rod-shaped, non-motile, non-spore forming, and facultatively anaerobic bacterium strain, designated as PI^T, was isolated from saline silt samples collected in saltern in Yantai, Shandong, China. Growth was observed within the ranges 4-45 °C (optimally at 33 °C), pH 6.0-9.0 (optimally at pH 7.0) and 1.0-11.0% NaCl (optimally at 3.0%, w/v). Strain PI^T showed highest 16S rRNA gene sequence similarity to Kangiella sediminilitoris BB-Mw22^T (98.3%) and Kangiella taiwanensis KT1^T (98.3%). The major cellular fatty acids (> 10% of the total fatty acids) were iso-C_15:0 (52.7%) and summed featured 9 (iso-C_17:1ω9c/C_16:0 10-methyl, 11.8%). The major polar lipids identified were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine and phosphatidylglycerol. The major respiratory isoprenoid quinone was Q-8. The G + C content of the genomic DNA was 45.8%. Average Nucleotide Identity values between whole genome sequences of strain PI^T and next related type strains supported the novel species status. Based on physiological, biochemical, chemotaxonomic characteristics and genomic analysis, strain PI^T is considered to represent a novel species within the genus Kangiella, for which the name Kangiella shandongensis sp. nov. is proposed. The type strain is PI^T (= KCTC 82509 ^T = MCCC 1K04352^T).

Aliikangiella coralliicola sp. nov., a bacterium isolated from coral Porites lutea, and proposal of Pleioneaceae fam. nov. to accommodate Pleionea and Aliikangiella

A novel Gram-stain-negative, non-endospore-forming, motile, and aerobic bacterial strain, M105^T, was isolated from coral Porites lutea, and was subjected to a polyphasic taxonomic study. Global alignment based on 16S rRNA gene sequences indicated that M105^T shares the highest sequence identity of 94.5 % with Aliikangiella marina GYP-15^T. The average nucleotide identity (ANI) and average amino acid identity (AAI) between M105^T and A. marina GYP-15^T was 69.8 and 71.6 %, respectively. On the basis of the results of phenotypic, chemotaxonomic, phylogenetic, phylogenomic, and comparative genomic analyses, it is concluded that M105^T should represent a novel species in the genus Aliikangiella, for which the name Aliikangiella coralliicola sp. nov. is proposed. The type strain is M105^T (=MCCC 1K03773^T= KCTC 72442^T). Furthermore, the family Kangiellaceae was classified into two families on the basis of phylogenetic, phylogenomic, polar lipid profile and motility variations. The novel family Pleioneaceae fam. nov. is proposed to accommodate the genera Aliikangiella and Pleionea.

Reclassification of the Taxonomic Framework of Orders Cellvibrionales, Oceanospirillales, Pseudomonadales, and Alteromonadales in Class Gammaproteobacteria through Phylogenomic Tree Analysis

Orders Oceanospirillales and Pseudomonadales play important roles in various ecosystems as the keystone taxa of microbiomes. However, the two orders present a close evolutionary relationship, which might have caused taxonomic misinterpretation and resulted in an incorrect understanding of their evolutionary history. In this study, first, we used the 16S rRNA gene sequences of 2,049 species of Gammaproteobacteria to build a phylogenetic tree, which demonstrated that reports regarding the evolutionary relationship of orders Cellvibrionales, Oceanospirillales, and Pseudomonadales based on a single conserved gene with a poor resolution have been conflicting; in particular, the major families Moraxellaceae and Pseudomonadaceae of order Pseudomonadales were separated from orders Cellvibrionales and Oceanospirillales Subsequently, we constructed the bac120 trees of all representative reference genomes of class Gammaproteobacteria based on 120 ubiquitous single-copy proteins from bacteria and a phylogenomic tree based on the 119 core genes of 257 reference genomes obtained from orders Cellvibrionales, Oceanospirillales, and Pseudomonadales to cross validate and infer their intrinsic evolutionary relationships. These results indicated that two novel orders, Moraxellales ord. nov. and Kangiellales ord. nov., and three novel families, Marinobacteraceae fam. nov., Perlucidibacaceae fam. nov., and Zooshikellaceae fam. nov., should be proposed. Additionally, orders Cellvibrionales and Oceanospirillales were merged into the order Pseudomonadales except for families Moraxellaceae and Kangiellaceae in class Gammaproteobacteria, which currently includes 18 families. Our work sheds some light on the evolutionary history of class Gammaproteobacteria, which could facilitate the detection and taxonomic analysis of natural communities.IMPORTANCE The orders Cellvibrionales, Oceanospirillales, and Pseudomonadales, as three major orders of the largest bacterial class, Gammaproteobacteria, play important roles in various ecosystems as the keystone taxa of microbiomes, but their evolutionary relationship is currently polyphyletic and chaotic. Here, we constructed a bac120 tree and core-genome tree and calculated the amino acid identity (AAI) value to explore their intrinsic evolutionary history. In this study, we proposed two novel orders and three novel families. This evolution study vastly reconstructed the taxonomic framework of class Gammaproteobacteria and could provide a more distinct perspective on global distribution and evolutionary patterns of these environmental microorganisms.

Trophic Specialization Results in Genomic Reduction in Free-Living Marine Idiomarina Bacteria

The streamlining hypothesis is usually used to explain the genomic reduction events in free-living bacteria like SAR11. However, we find that the genomic reduction phenomenon in the bacterial genus Idiomarina is different from that in SAR11. Therefore, we propose a new hypothesis to explain genomic reduction in this genus based on trophic specialization that could result in genomic reduction, which would be not uncommon in nature. Not only can the trophic specialization hypothesis explain the genomic reduction in the genus Idiomarina, but it also sheds new light on our understanding of the genomic reduction processes in other free-living bacterial lineages.

The streamlining hypothesis is generally used to explain the genomic reduction events related to the small genome size of free-living bacteria like marine bacteria SAR11. However, our current understanding of the correlation between bacterial genome size and environmental adaptation relies on too few species. It is still unclear whether there are other paths leading to genomic reduction in free-living bacteria. The genome size of marine free-living bacteria of the genus Idiomarina belonging to the order Alteromonadales (Gammaproteobacteria) is much smaller than the size of related genomes from bacteria in the same order. Comparative genomic and physiological analyses showed that the genomic reduction pattern in this genus is different from that of the classical SAR11 lineage. Genomic reduction reconstruction and substrate utilization profile showed that Idiomarina spp. lost a large number of genes related to carbohydrate utilization, and instead they specialized on using proteinaceous resources. Here we propose a new hypothesis to explain genomic reduction in this genus; we propose that trophic specialization increasing the metabolic efficiency for using one kind of substrate but reducing the substrate utilization spectrum could result in bacterial genomic reduction, which would be not uncommon in nature. This hypothesis was further tested in another free-living genus, Kangiella, which also shows dramatic genomic reduction. These findings highlight that trophic specialization is potentially an important path leading to genomic reduction in some marine free-living bacteria, which is distinct from the classical lineages like SAR11.

Genome Sequence of the Halophilic Bacterium Kangiella spongicola ATCC BAA-2076 T

The Gram-negative genus Kangiella contains a number of halophilic species that display high levels of iso-branched fatty acids. Kangiella spongicola was isolated from a marine sponge, Chondrilla nucula, from the Florida Keys in the United States.

The Gram-negative genus Kangiella contains a number of halophilic species that display high levels of iso-branched fatty acids. Kangiella spongicola was isolated from a marine sponge, Chondrilla nucula, from the Florida Keys in the United States. A genome assembly of 2,825,399 bp with a 44.31% G+C content was generated from strain A79^T (=ATCC BAA-2076^T).

Comparative Genomics Reveals Evidence of Genome Reduction and High Extracellular Protein Degradation Potential in Kangiella

The genus Kangiella has recently been proposed within the family Kangiellaceae, belonging to order Oceanospirillales. Here, we report the complete genome sequence of a novel strain, Kangiella profundi FT102, which is the only Kangiella species isolated from a deep sea sediment sample. Furthermore, gaps in the publicly available genome scaffold of K. aquimarina DSM 16071 (NCBI Reference Sequence: NZ_ARFE00000000.1) were also filled using polymerase chain reaction (PCR) and Sanger sequencing. A comparative genomic analysis of five Kangiella and 18 non-Kangiella strains revealed insights into their metabolic potential. It was shown that low genomic redundancy and Kangiella-lineage-specific gene loss are the key reasons behind the genome reduction in Kangiella compared to that in any other free-living Oceanospirillales strain. The occurrence of relatively diverse and more frequent extracellular protease-coding genes along with the incomplete carbohydrate metabolic pathways in the genome suggests that Kangiella has high extracellular protein degradation potential. Growth of Kangiella strains has been observed using amino acids as the only carbon and nitrogen source and tends to increase with additional tryptone. Here, we propose that extracellular protein degradation and amino acid utilization are significant and prominent features of Kangiella. Our study provides more insight into the genomic traits and proteolytic metabolic capabilities of Kangiella.

Aliikangiella marina gen. nov., sp. nov., a marine bacterium from the culture broth of Picochlorum sp. 122, and proposal of Kangiellaceae fam. nov. in the order Oceanospirillales

A Gram-stain-negative, non-motile, non-spore-forming, long rod-shaped bacterium, designated strain GYP-15T, was isolated from the culture broth of a marine microalga, Picochloruma sp. 122. Phylogenetic analyses revealed that strain GYP-15T shared 90.6 % 16S rRNA gene sequence similarity with its closest relative, Kangiella aquimarina KCTC 12183T, and represents a distinct phylogenetic lineage in a robust clade consisting of GYP-15T and members of the genera Kangiella and Pleionea in the order Oceanospirillales. Chemotaxonomic and physiological characteristics, including major cellular fatty acids, NaCl tolerance and pattern of carbon source utilization, could also readily distinguish strain GYP-15T from all established genera and species. Thus, it is concluded that strain GYP-15T represents a novel species of a new genus, for which the name Aliikangiella marina gen. nov., sp. nov. is proposed. The type strain of Aliikangiella marina is GYP-15T ( = MCCC 1K01163T = KCTC 42667T). Based on phylogenetic results, 16S rRNA gene signature nucleotide pattern and some physiological characteristics, the three genera Kangiella, Pleionea and Aliikangiella are proposed to make up a novel family, Kangiellaceae fam. nov., in the order Oceanospirillales.

Kangiella profundi sp. nov., isolated from deep-sea sediment

A taxonomic study employing a polyphasic approach was carried out on strain FT102(T), which was isolated from a deep-sea sediment sample collected in the south-west Indian Ocean at a depth of 2784 m. The strain was Gram-stain-negative, non-motile, rod-shaped and non-spore-forming. It grew optimally at 37-42 °C, pH 6.5-8.5 and in the presence of 1-4% (w/v) NaCl. Phylogenetic analysis of 16S rRNA gene sequences confirmed the separation of the novel strain from recognized members of the genus Kangiella that are available in public databases. Strain FT102(T) exhibited 95.5-98.6% 16S rRNA gene sequence similarity to the type strains of the eight recognized species of the genus Kangiella. The chemotaxonomically characteristic fatty acid iso-C15:0 and ubiquinone Q-8 were also detected. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine. The DNA G + C content of strain FT102(T) was 45.0 mol%. The mean DNA-DNA relatedness values between strain FT102(T) and the type strains of Kangiella aquimarina and Kangiella koreensis were 47.3% and 13.7%, respectively. The combined results of phylogenetic, physiological and chemotaxonomic studies indicated that strain FT102(T) was affiliated with the genus Kangiella but differed from the recognized species of the genus Kangiella. Therefore, strain FT102T represents a novel species of the genus Kangiella, for which the name Kangiella profundi sp. nov. is proposed. The type strain is FT102(T) ( = CGMCC 1.12959(T) = KCTC 42297(T) = JCM 30232(T)).

Kangiella chungangensis sp. nov. isolated from a marine sand

A Gram-negative bacterium, designated CAU 1040(T), which was isolated from marine sand obtained from Jeju Island in South Korea, was characterized as an aerobic rod-shaped organism that that was non-motile, non-spore-forming and halophilic. The bacterium grew optimally at 37 °C, at pH 8, and in the presence of 2% (w/v) NaCl. The taxonomic classification of CAU 1040(T) was investigated using a polyphasic characterization approach. While phylogenetic analysis of the 16S rRNA gene sequence revealed that CAU 1040(T) belongs to the genus Kangiella, the strain exhibited only 94.4-95.4% sequence similarity to the previously described Kangiella species. Similar to other Kangiella species, Q-8 was the predominant ubiquionone and iso-C(15:0) was the major cellular fatty acid detected in strain CAU 1040(T). The predominant polar lipids identified were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The G+C content of the CAU 1040(T) genome was 45.3 mol%. The phylogenetic, physiological, biochemical and chemotaxonomic data obtained in this study indicate that strain CAU 1040(T) represents a novel species of the genus Kangiella, for which the name Kangiella chungangensis sp. nov. is hereby proposed. The type strain is CAU 1040(T) (KCTC 42299(T), NBRC 110728(T)).

Litorivivens lipolytica gen. nov., sp. nov., a lipolytic bacterium isolated from a tidal flat

A Gram-stain-negative, flagellated, aerobic and rod-shaped or ovoid bacterial strain, designated HJTF-7(T), was isolated from a tidal flat on the South Sea of South Korea, and its taxonomic position was investigated using a polyphasic approach. Strain HJTF-7(T) grew optimally at 25 °C, at pH 7.0-8.0 and in the presence of 2.0% (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees, based on 16S rRNA gene sequences, showed that strain HJTF-7(T) joined the cluster comprising the type strains of species of the genera Spongiibacter and Zhongshania. Strain HJTF-7(T) exhibited 16S rRNA gene sequence similarities of 90.4-92.5% to the type strains of species of the genera Spongiibacter and Zhongshania and of less than 91.5% to the type strains of other recognized species. Strain HJTF-7(T) contained Q-8 as the predominant ubiquinone. The major fatty acids were iso-C17:1ω9c, iso-C15:0, iso-C17:0, iso-C11:0 3-OH and C17:1ω8c and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The fatty acid and polar lipid profiles of strain HJTF-7(T) were distinct from those of members of the genera Spongiibacter and Zhongshania. The DNA G+C content of strain HJTF-7(T) was 55.9 mol%. The phylogenetic data and differential chemotaxonomic and other phenotypic properties revealed that strain HJTF-7(T) represents a novel genus and species within the class Gammaproteobacteria, for which the name Litorivivens lipolytica gen. nov., sp. nov. is proposed. The type strain of Litorivivens lipolytica is HJTF-7(T) ( =KCTC 42157(T) =CECT 8654(T)).

Boseongicola aestuarii gen. nov., sp. nov., isolated from a tidal flat sediment

A Gram-stain-negative, aerobic, non-motile and pleomorphic (coccoid, ovoid or rod-shaped) bacterial strain, BS-W15T, isolated from a tidal flat sediment at Boseong in South Korea, was characterized taxonomically. Strain BS-W15T grew optimally at 25 °C, at pH 7.0–8.0 and in the presence of approximately 2.0 % (w/v) NaCl. Neighbour-joining and maximum-likelihood phylogenetic trees, based on 16S rRNA gene sequences, revealed that strain BS-W15T joined the cluster comprising the type strains of Profundibacterium mesophilum , Hwanghaeicola aestuarii , M. pelagius and M. salinus , showing 93.5–96.4 % sequence similarities. Strain BS-W15T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the predominant fatty acid. The polar lipid profile of strain BS-W15T contained phosphatidylcholine and phosphatidylglycerol as major components, differentiating it from those of the type strains of P. mesophilum , H. aestuarii , M. pelagius and M. salinus . The DNA G+C content of strain BS-W15T was 58.7 mol%. The differential phenotypic properties, together with the phylogenetic and chemotaxonomic data, demonstrate that strain BS-W15T is distinct from type strains of P. mesophilum , H. aestuarii , M. pelagius and M. salinus . On the basis of the data presented, strain BS-W15T is considered to represent a novel genus and species, for which the name Boseongicola aestuarii gen. nov., sp. nov. is proposed. The type strain is BS-W15T ( = KCTC 32576T = CECT 8489T).