Red tides are natural global phenomena that have been caused by enormous growth of plankton algae, such as dinoflagellates and diatoms, in marine environments (Anderson et al., 2002). Heretofore, many algicidal bacteria to be used as biological control agents have been isolated from various marine environment for decrease and elimination of red tide (Mayali and Azam, 2004; Meyer et al., 2017). Biologically active ingredients isolated from these bacteria have been known as alkaloids, amino acid derivatives, peptides, proteins, enzymes, polyketides, terpenes, and fatty acids (Meyer et al., 2017). In this report, we describe the complete genome sequence and annotation of a novel algicidal bacterium Flavobacteriaceae sp. BG1.

An algicidal marine bacterium against marine diatom Skeletonema costatum, designated strain BG1, was isolated from coastal seawater, East Sea (38° 18’ 41” N, 128° 32’ 33” E) of Korea. The strain BG1 was routinely cultured on marine agar 2216 (Difco) at 30°C for 3 days. Phylogenetic analyses based on 16S rRNA gene sequence indicated that strain BG1 was affiliated to the family Flavobacteriaceae and showed highest similarity to Galbibacter mesophilus Mok-17^T (95.5%).

For the sequencing of the whole genome, the cells were incubated at 30°C in marine broth 2216 (Difco) for 2 days and the genomic DNA was extracted using MagAttract^® HMW DNA kit (Qiagen) according to the manufacturer’s instructions. The sequencing of the whole genome was performed on the PacBio RS II system and Illumina Hiseq X-ten platform by Macrogen Inc.. The sequencing reads of PacBio were assembled using the RS Hierarchical Genome Assembly Process 3.0 (HGAP) (Chin et al., 2013), and the sequencing reads of Illumina were applied for accurate genome sequence using Pilon software (version 1.21) (Walker et al., 2014). Genome completeness and contamination were verified with CheckM (Version 1.0.18) (Parks et al., 2015). The genome annotation was performed using NCBI Prokaryotic Genome Annotation Pipeline (PGAP) (Tatusova et al., 2016). Additional function of the predicted genes were conducted by EggNOG 5.0 (Huerta-Cepas et al., 2019), BlastKOALA with KEGG database (Kanehisa et al., 2016) and Rapid Annotations using Subsystems Technology (RAST) server with SEED (Aziz et al., 2008).

The complete genome of strain BG1 was composed of one contig, 3,708,790 bp in length. The G + C content of the genome was 37.3%. The results of CheckM estimation indicated that genome completeness was 99.67% with 0.17% contamination and 0% strain heterogeneity. A total of 3,160 protein-coding genes, 9 rRNA genes, 44 tRNA genes, 4 non-coding RNA genes and 27 pseudo genes were predicted (Table 1).

Table 1

Genome features of strain BG1

Genome features	Value
No. of contigs	1
Depth (X)	718.2
Genome size (bp)	3,708,790
G + C content (%)	37.3
Protein-coding genes	3,160
tRNA genes	44
rRNA genes (5S, 16S, 23S)	9 (3, 3, 3)
Non-coding RNA genes	4
Pseudo genes	27

The genome sequence of strain BG1 contained carotenoid biosynthesis-related genes such as 15-cis-phytoene synthase CrtB, pytoene desaturase CrtI and β-carotene 3-hydroxylase CrtZ. It contained gliding motility-related genes; gliding motility-associated ABC transporter ATP-binding subunit GldA, gliding motility protein GldB/GldC/GldD/GldE/GldG/GldJ/GldL/GldM/GldN, gliding motility associated ABC transporter permease protein GldF, gliding motility associated lipoprotein GldH/GldK, peptidyl-prolyl cis/trans isomerase GldI. It contained also bacterial motility-related genes such as CheA/CheB/CheR/CheY (involved in chemotaix) and CpaA/CpaB/CpaC/CpaD/CpaE/CpaF/PilA/PilD (involved in pilus system). Its genome encoded bacterial secretion system-related genes such as GspA/GspC/GspD/GspE/GspF/GspG/GspH/GspI/GspJ/GspK/GspL (involved in Type II secretion system), SecA/SecB/SecD/SecE/SecF/SecG/SecY (involved in Sec system), and type IX secretion system membrane protein PorP/SprF (involved in PorSS, Type IX secretion system). It contained various biopolymer degradation-related genes; α-amylase AmyA/AmyS, cellulase CelC, β-glucosidase BglX, xylose isomerase XylA, xylose kinase XylB, N-acetylglucosamine-6-phosphatase deacetylase NagA, glucosamine-6-phosphate deaminase NagB, lipolytic enzyme LipA/LipB. It also encoded biosynthesis of terpenoids and polyketides-related genes; acetyl-CoA-C-acetyltransferase ACAT, 1-deoxy-D-xylulose-5-phosphate reductoisomerase Dxr, 4-diphosphocytidyl-2-C-methyl-D-erythritolkenase IspE, 1-deoxy-D-xylulose-5-phosphate synthase Dxs, (E)-4-hydroxy-3-methylbut-2-enyl-diphosphate synthase IspG, 4-hydroxy-3-methylbut-2-en-1-yl diphosphate reductase IspH, 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase IspDF, farnesyl diphosphate synthase IspA, dTDP-4-dehydrorhamnose reductase RmlD, glucose-1-phosphate thymidylyltransferase RmlA, dTDP-glucose 4,6-dehydratase RmlB, dTDP-4-dehydrorhamnose 3,5-epimerase RmlC. The genome also contained biosynthesis of secondary metabolites-related genes; phenylalanine ammonia-lyase PAL, acyl carrier protein AcpP, tryptophan 7-halogenase PrnA, ornithine racemase Orr. These abundant biopolymer degradation genes, protein secretion genes, and secondary metabolite production genes are thought to be useful in biological industry applications.

Nucleotide sequence accession numbers

The strain BG1 is available at KACC 16660, KCCM 43341 and JCM 33635. The whole genome sequence is accessible in GenBank under the accession number CP058364.

Flavobacteriaceae 과에 속하는 신종 살조성 세균 BG1 균주는 동해 연안 해수로부터 분리되었고, PacBio RS II system과 Illumina Hiseq X-ten platform을 사용하여 전체 유전체 염기 서열을 결정하였다. BG1 균주의 유전체는 37.3% G + C 함량을 지닌 3,708,790 bp 길이의 단일 유전체로 구성되었고, 전체 3,160개의 단백질 암호 유전자, 9개의 rRNA 유전자, 44개의 tRNA 유전자, 4개의 non-coding RNA 유전자 및 27개의 위유전자(pseudo gene)가 확인되었다. BG1 균주는 다양한 생물 고분자 물질 분해 관련 유전자와 terpenoids, polyketides 및 2차 대사산물 생합성 관련 유전자가 포함되어 있었다. 이러한 게놈 정보는 생체 고분자 분해 및 생체 활성 물질 스크리닝에 적용하는데 유용할 것으로 예상된다.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1D1 A3B04033871).