Table 2.
Comparison of major types of citrus canker.
| Xcc | XauB | XauC | References | ||
|---|---|---|---|---|---|
| Host range | Diverse | Less diverse | Restricted | [30] | |
| Xanthum gum production | Highest | Almost 3 times less than Xcc | Almost 2 times less than Xcc | ||
| Cellular growth | Non-fastidious, similar cellular mass values as XauC | Fastidious | Non-fastidious, similar cellular mass values as Xcc. | ||
| Comparative genetic analysis | |||||
| Genes related to flagellum synthesis | Major 3 clusters of genes (F1, F2, and F3) present. Another 4th cluster is also present, consisting of 2 genes. Unrelated genes are also present in the region between F1 and F2 (XACSR9). |
F2 gene cluster is absent. No genes are present in the region between F1 and F2. |
All four gene clusters are present. No genes are present in the region between F1 and F2. |
||
| Presence of XacPNP gene | Present | Absent | Absent | ||
| Type 1 Secretion System genes (T1SS) | hlyB and hlyD encoding genes and TolC present | hlyB and hlyD encoding genes absent, TolC present | hlyB and hlyD encoding genes and TolC present | [31] | |
| Type 4 Secretion System genes (T4SS) | Both in plasmid and chromosome | Only in plasmid, lack chromosomal copy | Only in plasmid, lack chromosomal copy | ||
| Genes involved in the regulation and synthesis of Type IV pilus (T4p) | Many genes are present including pilX, pilV, pilA, pilL, and fimT, forming atleast 4 clusters of genes. | Among different clusters of genes, pilX, pilA, pilV.pil anf fimT genes are absent | Among different clusters of genes, pilX, pilA, pilV, pil, and fimT genes are absent | ||
| Genes related to synthesis of Hemagglutinin and Hemolysin | Present in two regions of genome XAC4112-XAC4125 XAC1810-XAC1819 |
The genes present in 2nd region (XAC1810-XAC 1819) including fhaB and fhaC are absent | The genes present in 2nd region (XAC1810-XAC 1819) including fhaB and fhaC are absent | ||
| vapBC and tspO gene | Present | Absent | Absent | ||
| Effector XopS | Present (in some cases as pseudogene) | Absent | Absent | ||
| Effector XopK | Present | Found as pseudogene | Found as pseudogene | [30,31,51] | |
| Effector XopF1, xopB, xopE4, xopJ, xopAF, xopAG | Absent | Present (in some cases as pseudogene) | Present (in some cases as pseudogene) | ||
| Effectors xopE2, xopN, xopP, xopAE | Present | Present | Absent | ||
| Basic physiological, biochemical, and serological tests | [39] | ||||
| Reaction with Mab A1 (ELISA test) | Reacts | Does not react | Does not react | ||
| Phage sensitivity | Bacteriophage Cp1 | Variable response | Insensitive | Insensitive | |
| Bacteriophage Cp2 | Variable response | Insensitive | Insensitive | ||
| Bacteriophage Cp3 | Insensitive | Sensitive | Insensitive | ||
| Casein hydrolysis test | Positive | Negative | Positive | ||
| Gelatin hydrolysis test | Positive | Negative | Negative | ||
| Growth in presence of | 3% NaCl | Grows | No growth observed | No growth observed | |
| Maltose | Grows | No growth observed | No growth observed | [54] | |
| Aspartic acid | Grows | No growth observed | No growth observed | ||
| General features of genome | [15,30] | ||||
| Genome | |||||
| Size (bp) | 5,274,174 | 4,877,808 | 5,012,633 | ||
| # of contigs | 3 | 239 | 351 | ||
| %GC | 64.7 | 64.9 | 64.8 | ||
| Protein coding genes | |||||
| Total | 4427 | 3804 | 3921 | ||
| With functional assignment | 2779 | 2694 | 2728 | ||
| Hypothetical | 262 | 117 | 184 | ||
| Conserved hypothetical | 1386 | 993 | 1009 | ||
| RNAs | |||||
| rRNA operons | 2 | 2 | 2 | ||
| tRNAs | 54 | 51 | 51 | ||
XacPNP = Plant natriuretic peptide (belonging to Xcc); Mab = Monoclonal Antibodies; ELISA = Enzyme-linked immunosorbent assay; General features of genome of XauB and XauC are based on 94% and 96% of their genomes.