A genomic island present along the bacterial chromosome of the Parachlamydiaceae UWE25, an obligate amoebal endosymbiont, encodes a potentially functional F-like conjugative DNA transfer system

Table 2 The genomic island of the UWE25 endosymbiont presents seven different modules. The limit of each module was determined by residual cumulative G+C content analysis.

Modules	1^st mod.	2^nd mod.	3^rd mod.	4^th mod.	5^th mod.	6^th mod.	7^th mod.
Length	32 kb	16 kb	19 kb	10 kb	6 kb	12 kb	2 kb
Mean G+C content (%)	36.4%^a	34.1%	40.9%	33.4%	41.8%	33.3%	38.7%
Number of ORFs	28	18	21	13	1	13	6
Number of genes having an homolog	16 (57%)	5 (28%)	16 (85%)	7 (54%)	1 (100%)	5 (38%)	5 (83%)
Number of genes having no homolog	12	13	5	6	0	8	1
Best hits with homologs in:
- chlamydiae	12	0	0	0	0	0	0
- cyanobacteria	2	2	0	3	0	2	0
- plants^b	0	0	0	0	0	0	0
- α-proteobacteria	0	0	6	0	0	0	0
- β-proteobacteria	1	0	3	1	0	0	0
- γ-proteobacteria	0	1	6	2	0	0	4^c
- Bacteroidetes group	0	0	1	0	0	2	1
- others	1	2	0	1	1	1	0
Homologous^d to:
- phage-related protein	0	3	0	1	0	1	2
- putative transposase	1	1	2	0	0	2^e	2
- resolvase	0	0	0	0	0	0	1
- protein involved in DNA metabolism	0	1	0	2	0	2	0

^a the G+C content is similar to that of 36.1% of the remaining genome (calculated on 1931 ORFs);
^b 5% of the 2031 ORFs of the genome of UWE25 have products homologous to plant proteins, but no ORFs of the GI were homologous to plant counterparts;
^c two ORFs which presented best homologs encoded by a plasmid of an uncultured bacteria present in activated sludge have a second best BLAST hit encoded by a gamma-proteobacterial ORFs (Pseudomonas sp.);
^d not only the best BLAST hit is taking into consideration to determine the putative function encoded by the ORF;
^e one of them has an e-value above 0.001.

ISSN: 1471-2180