Characterization of the genome of strain FS91703
The entire genome of strain FS91703 was sequenced and assembled, resulting in a final contig with 5,435,691 bp total length. The GC content was 37.78%, with 4,951 coding sequences. The coding genes was 4,754,943 bp length, with a 960 bp average length (87.48% of the total genome length). The interspersed repeats were 51 copies long, 3,208 bp (0.06% of the total genome length). Tandem repeats were 488 copies, 26,803 bp in length (0.49% of the total genome length). strain FS91703 contained 94 tRNA genes, 18 rRNA genes (including 6 each of 23S rRNA, 16S rRNA, and 5S rRNA), and 21 sRNA genes, with prophage 9, and the total length was 196 866 bp. The genome sequence and its annotation information were submitted to the NCBI database by accession number CP119767.
Table 1
Overview of genome function analysis of strain FS91703
Database
|
Gene number
|
NR
|
4 847
|
Swiss-Prot
|
2 388
|
KEGG
|
1 608
|
COG
|
3 041
|
GO
|
3 674
|
PHI
|
715
|
Pfam
|
14
|
VFDB
|
571
|
CARD
|
10
|
Secretory protein
|
658
|
T3SS
|
493
|
CAZY
|
145
|
Genome Functional Analysis Results
The FS91703 strain had 1,608, 3,674, 2,388, 3,041, and 4,847 genes in the KEGG, GO, Swiss-Prot, COG, and NR databases, respectively, the databases with the most annotated genes (see Table 1). The minimum number of annotated genes was 10.
NR of Strain FS91703
The gene sequence of strain FS91703 was converted to amino acid sequence and compared with the NR database, which showed that 4,847 genes were annotated in the NR database, of which C. artherosphaerae was the most frequently annotated, accounting for 76.48% (Fig. 1).
GO of Strain FS91703
The GO database was annotated with 3,674 genes. Cellular and metabolic processes in biological processes were the highest gene enrichment for two pathways with 1,376 and 1,393 genes, respectively. Cells and cell parts in cellular organization were the highest gene enrichment for the two pathways with 1,352 and 1,344 genes, respectively. Binding and catalytic activity in molecular function were the highest gene enrichment for the two pathways with 1,317 and 1,603 genes, respectively (Fig. 2).
A total of 1,608 orthologous protein-coding genes were matched to 39 KEGG metabolic pathways. The pathways with the greatest number of genes were amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamin, which are necessary to maintain bacterial metabolism (Fig. 3).
There were 3,041 genes annotated in the COG analysis. These were classified into 20 categories, C-V, according to function. The annotated functions mainly covered the pathways of biosynthesis of cell wall, membrane, and envelope, metabolism, amino acid transport, transcription (Fig. 4). The results were similar to those of the KEGG metabolic pathway analysis. Many genes were found to be involved in metabolic processes that sustain basic bacterial life.
PHI of FS91703 strain
The PHI database has annotated 798 genes that interact with animal hosts. Of these, 436, 90, and 49 genes were found to decrease, lose, or increase bacterial virulence after mutation. In the process of infecting the host, pathogenic bacteria secrete a series of effectors, which play an essential role in the interaction between the host and the pathogenic bacteria. The ability of effectors to effectively control the host is key to successful colony formation of pathogenic bacteria. Eight genes encoding effectors have been annotated in the PHI database, including clpV5 (3), lpdA (2), mgtC (2) and ipx10. This gene was annotated. Studies have shown that deletion of the clpV gene in pathogenic E. coli reduces the expression of type I pili, affecting the ability of the bacteria to attach and invade, and reducing the pathogenicity of the strain [10].
VFDB and CARD of FS91703 strain
Virulence factors are grouped into 14 categories according to their functions; regulation, antimicrobial activity/competitive advantage, post-translational modifications, stress survival, nutritional/metabolic factors, biofilms, immune modulation, exoenzymes, exotoxins, motility, effector delivery system, invasion, adhesion, and others. In this study, 52 virulence factors encoded by 94 genes were identified in the VFDB database. The virulence factors with the highest number of annotated genes were immune modulators, stress survival factors, and nutritional/metabolic factors, with 38, 19, and 12 genes annotated, respectively. Immune modulatory factors were mainly capsular, LPS O-antigen, LPS (lipopolysaccharide), and LOS (lipopolysaccharide). Among these factors, genes encoding capsules were the most abundant, including 9 genes such as capK/L/5H, ndk, upps, and fnlA. Stress resistance factors were mainly catalase, urease, ClpC, and MsrAB. Virulence factors associated with the effector secretory system were types III, IV, and VI. Of these, the most common virulence factors associated with the type III secretory system were T3SS, Psyringae TTSS effectors, and Mxi-Spa TTSS effectors regulated by MxiE. In the nutrient metabolism system, many factors related to iron uptake were found, including heme biosynthesis, aerobactin siderophores, and desferrioxamine. Four bacterial toxins were predicted: colibactin, β-hemolysin, the phytotoxin coronatine, and phosphatidylinositol-specific phospholipase C (PI-PLC). In addition, several drug efflux pump systems were annotated, including AdeFGH and FarAB.
The CARD database was used for the annotation of the total of 10 genes for antibiotic resistance in strain FS91703. They are sul2 (2), IND-14, catB2, catB6, catB8, tetX (2), dfrE, and streptomycetes, and are resistant to folate pathway inhibitors (sul2/dfrE), penicillin (IND-14), cephem (IND-14), carbapenems (IND-14), phenol (catB2, catB6, catB8), tetracycline (tetX), and ercomycin (streptomyces). These correspond to the following antibiotics.
Genome-wide map of strain FS91703
Based on basic genome sequence information, gene prediction results, non-coding RNA prediction results, and bioinformatics analysis results, we drew a whole genome map of this fungus (Fig. 5).
Antimicrobial activity of strain FS91703
The antimicrobial susceptibilities of strain FS91703 and MICs are shown in Table 2. Strain FS91703 was susceptible to β-lactam combination agents, cephems, monobactams, and carbapenems, and was intermediate to phenicol. It was also resistant to all antimicrobial agents tested, including folate pathway inhibitors, fluoroquinolones, tetracyclines, aminoglycosides, and penicillin.
Table 2
Concentration of minimum growth inhibitory and antimicrobial susceptibility of C. arthrosphaerae FS91703.
Antibiotics Group
|
Antibiotics
|
MIC
|
Interpretation
|
Penicillin
|
Piperacillin
|
≥ 128
|
R
|
β-lactam Combination Agents
|
Piperacillin-tazobactam
|
≤ 16/4
|
R
|
Cephems
|
Ceftazidime
|
≤ 8
|
S
|
Cefepime
|
≤ 8
|
S
|
Monobactams
|
Aztreonam
|
≤ 8
|
S
|
Carbapenems
|
Imipenem
|
≤ 4
|
S
|
Meropenem
|
≤ 4
|
S
|
Aminoglycosides
|
Gentamicin
|
≥ 16
|
R
|
Tobramycin
|
≥ 16
|
R
|
Amikacin
|
≥ 64
|
R
|
Tetracyclines
|
Tetracycline
|
≥ 16
|
R
|
Minocycline
|
≥ 16
|
R
|
Fluoroquinolones
|
Cipofloxacin
|
≥ 4
|
R
|
Levofloxacin
|
≥ 8
|
R
|
Lomefloxactn
|
≥ 8
|
R
|
Inhibitors of folate pathway
|
Trimethoprim-sulfmethoxazole
|
≥ 4/76
|
R
|
Phenicol
|
Chloramphenicol
|
16
|
I
|
Note: S-Sensitive, I-Intermediary, R-Resistant |
Phylogenetic relationships with 16S rRNA
The 16S rRNA of strain FS91703 was 1406 base pairs and was submitted to GenBank (accession number: ON573338). The 16S rRNA of strain FS91703 was compared with those of other bacteria registered in GenBank, and a phylogenetic tree was constructed by selecting species with high similarity (Fig. 6). Strain FS91703 belonged to the same branch as C. arthrosphaerae (CC-VM-7, FDAARGOS 519, and ED882-96 strains). The 16S rRNA of strain FS91703 was more than 99.85% identical to the 16S rRNA of the above three strains. These results suggest that strain FS91703 is one of the C. arthrosphaerae strains.
Average nucleotide identity (ANI) analysis
FS91703, two strains of C. arthrosphaerae, and 21 other Chryseobacterium species were analyzed by ANI. Intercomparison of FS91703 with FDAARGOS 519 and ED882-96 strains of C. arthrosphaerae showed ANI values of 96.69 and 96.13%, respectively; the ANI values between strain FS91703 and other strains of the genus Chryseobacterium were less than 85% (Fig. 7). The interspecies identification criteria with 95% ANI value confirmed that strain FS91703 is C. arthrosphaerae.