1633:
54:
1628:
31:
312:, but one study has challenged this view. In that alternative, the Holosporaceae are the sole representatives of their own order, the Holosporales, and as such not part of the Rickettsiales (see the schematic tree below). Other lineages, not clearly part of any family, have been described, as well. Examples include
858:
Rickettsiales genomes are undergoing reductive evolution and are typically small (generally < 1,5 Mbp), AT-rich (generally < 40% GC) with a low coding density (generally < 85%) and a relatively high number of pseudogenes. Reduction in genome size, % GC and coding density and genes are
829:
Early reports suggested that they represented sister clades to each other. However, later studies suggested that this relationship is false and was due to a phylogenetic artefact, which artificially groups independent AT-rich and fast-evolving lineages (Rickettsiales and
Pelagibacterales have both
845:
Another study adheres to the sister relationship between the two clades (see schematic tree). In their classification, the relation between the two orders is retained in the subclass, the
Rickettsidae, which include the Rickettsiales, the Pelagibacteriales, and the extinct
867:. Genetic drift is enhanced in Rickettsiales genomes due to low population sizes (given their endosymbiotic nature) and frequent population bottlenecks. Similarly, Muller's ratchet is activated through the lack of recombination and
1551:
1674:
1525:
1564:
1116:"New rRNA gene-based phylogenies of the Alphaproteobacteria provide perspective on major groups, mitochondrial ancestry and phylogenetic instability"
1000:"New rRNA gene-based phylogenies of the Alphaproteobacteria provide perspective on major groups, mitochondrial ancestry and phylogenetic instability"
1499:
1538:
1667:
1377:
Darby AC, Cho NH, Fuxelius HH, Westberg J, Andersson SG (2007). "Intracellular pathogens go extreme: genome evolution in the
Rickettsiales".
981:
1703:
1660:
1600:
1059:"Single-cell genomics of a rare environmental alphaproteobacterium provides unique insights into Rickettsiaceae evolution"
1543:
1698:
53:
976:
Thomas S. (2016). Rickettsiales:Biology, Molecular
Biology, Epidemiology, and Vaccine Development. pp.529. Springer•
887:
Li D, Fang J, Wen B, Wua X (2021). "Molecular identification of a novel intracellular proteobacteria from scallop
1569:
826:
The phylogenetic relationship between these two groups has yet to reach consensus in the scientific literature.
868:
288:
The
Rickettsiales are difficult to culture, as they rely on living eukaryotic host cells for their survival.
248:
1693:
1413:
830:
properties) together. Upon correcting for this artefact, the
Pelagibacterales form a sister clade to the
345:
39:
1605:
1579:
1473:
1331:
1283:(2012). "Independent genome reduction and phylogenetic reclassification of the oceanic SAR11 clade".
1235:
1127:
1070:
1011:
900:
274:
1640:
1627:
1280:
864:
522:
323:
244:
85:
1451:
959:
916:
847:
48:
934:
Werren JH, Baldo L, Clark ME (2008). "Wolbachia: master manipulators of invertebrate biology".
1587:
1460:
1394:
1359:
1300:
1261:
1204:
1155:
1096:
1039:
977:
951:
812:
808:
462:
1644:
1632:
1592:
1530:
1386:
1349:
1339:
1292:
1251:
1243:
1194:
1186:
1145:
1135:
1086:
1078:
1029:
1019:
943:
908:
831:
450:
411:
407:
401:
397:
839:
835:
674:
542:
366:
336:
301:
138:
1335:
1239:
1131:
1074:
1015:
904:
263:, which causes diseases in livestock. Another genus of well-known Rickettsiales is the
1354:
1319:
1256:
1223:
1199:
1174:
1150:
1115:
1091:
1058:
1034:
999:
697:
297:
180:
155:
75:
1320:"The SAR11 group of alpha-proteobacteria is not related to the origin of mitochondria"
912:
30:
1687:
920:
860:
558:
309:
305:
278:
269:, which infect about two-thirds of all arthropods and nearly all filarial nematodes.
128:
963:
1465:
471:
438:
381:
1344:
1224:"Phylogenomic evidence for a common ancestor of mitochondria and the SAR11 clade"
1140:
1024:
1512:
1445:
683:
1390:
731:
253:
1436:
1486:
1296:
822:
Phylogenetic relationship between
Rickettsiales and Pelagibacterales (SAR11)
626:
608:
583:
282:
265:
259:
1556:
1398:
1363:
1304:
1265:
1208:
1159:
1100:
1043:
955:
1082:
1430:
713:
65:
1190:
947:
998:
Ferla, M. P.; Thrash, J. C.; Giovannoni, S. J.; Patrick, W. M. (2013).
1517:
1247:
1407:
1504:
1491:
1057:
Martijn J, Schulz F, Zaremba-Niedzwiedzka K, et al. (2015).
270:
1411:
296:
1478:
850:(mitochondria themselves are not bacteria, but organelles).
316:
803:
1648:
1114:
Ferla MP, Thrash JC, Giovannoni SJ, Patrick WM (2013).
257:, which causes a variety of diseases in humans, and
1420:
1222:Thrash JC, Boyd A, Huggett MJ, et al. (2011).
1175:"A robust species tree for the alphaproteobacteria"
871:(the eukaryotic host cell is a natural barrier).
308:. Most studies also support the inclusion of the
487: Subgroups Ib, II, IIIa, IIIb, IV and V
1668:
1173:Williams KP, Sobral BW, Dickerman AW (2007).
8:
251:, and some are notable pathogens, including
1675:
1661:
1408:
100:Gieszczykiewicz 1939 (Approved Lists 1980)
29:
20:
1353:
1343:
1255:
1198:
1149:
1139:
1090:
1033:
1023:
993:
991:
989:
1318:Rodríguez-Ezpeleta N, Embley TM (2012).
879:
285:developed from members of this group.
43:(red dots) in the cell of a deer tick
322:Schematic ribosomal RNA phylogeny of
133:Moshkovski 1945 (Approved Lists 1980)
7:
1624:
1622:
1580:ecde0bfc-28db-4a2d-ac15-9a1ca44709d1
160:Pinkerton 1936 (Approved Lists 1980)
704:
669:
599:
574:
549:
537:
514:
457:
445:
373:
361:
331:
1647:. You can help Knowledge (XXG) by
14:
913:10.1016/j.aquaculture.2021.736565
1631:
1626:
249:obligate intracellular parasites
52:
1:
1345:10.1371/journal.pone.0030520
1141:10.1371/journal.pone.0083383
1025:10.1371/journal.pone.0083383
1720:
1621:
1704:Alphaproteobacteria stubs
1391:10.1016/j.tig.2007.08.002
815:ribosomal RNA sequences.
727:
709:
702:
679:
667:
622:
604:
597:
579:
572:
554:
547:
535:
519:
512:
485:
467:
455:
443:
394:
378:
371:
359:
341:
110:
105:
49:Scientific classification
47:
37:
28:
23:
869:horizontal gene transfer
859:generally attributed to
243:, are an order of small
807:from the comparison of
292:Rickettsiales phylogeny
1643:-related article is a
1279:Viklund J, Ettema TJ,
190:Anadelfobacter veles"
1297:10.1093/molbev/msr203
1083:10.1038/ismej.2015.46
346:Magnetococcus marinus
40:Rickettsia rickettsii
275:endosymbiotic theory
273:studies support the
239:, informally called
1699:Alphaproteobacteria
1641:Alphaproteobacteria
1336:2012PLoSO...730520R
1240:2011NatSR...1E..13T
1191:10.1128/JB.00269-07
1132:2013PLoSO...883383F
1075:2015ISMEJ...9.2373M
1016:2013PLoSO...883383F
948:10.1038/nrmicro1969
936:Nat. Rev. Microbiol
905:2021Aquac.53936565L
854:Reductive evolution
324:Alphaproteobacteria
277:according to which
245:Alphaproteobacteria
206:corrig. Prokopchuk
86:Alphaproteobacteria
848:protomitochondrion
523:Proto-mitochondria
168:Tenuibacteraceae"
1656:
1655:
1616:
1615:
1588:Open Tree of Life
1414:Taxon identifiers
1248:10.1038/srep00013
982:978-3-319-46857-0
819:
818:
797:
796:
788:
787:
779:
778:
770:
769:
761:
760:
752:
751:
743:
742:
656:
655:
647:
646:
638:
637:
496:
495:
463:Pelagibacteraceae
427:
426:
233:
232:
225:
211:
197:
175:
161:
151:
134:
124:
101:
16:Order of bacteria
1711:
1677:
1670:
1663:
1635:
1630:
1623:
1609:
1608:
1596:
1595:
1583:
1582:
1573:
1572:
1560:
1559:
1547:
1546:
1534:
1533:
1521:
1520:
1508:
1507:
1495:
1494:
1482:
1481:
1469:
1468:
1456:
1455:
1454:
1441:
1440:
1439:
1409:
1403:
1402:
1374:
1368:
1367:
1357:
1347:
1315:
1309:
1308:
1276:
1270:
1269:
1259:
1219:
1213:
1212:
1202:
1170:
1164:
1163:
1153:
1143:
1111:
1105:
1104:
1094:
1054:
1048:
1047:
1037:
1027:
995:
984:
974:
968:
967:
931:
925:
924:
884:
865:Muller's ratchet
832:Hyphomicrobiales
705:
670:
600:
575:
550:
538:
515:
458:
451:Pelagibacterales
446:
412:Sphingomonadales
408:Rhodospirillales
402:Rhodobacteraceae
398:Hyphomicrobiales
374:
362:
332:
319:
318:
219:
205:
191:
169:
159:
145:
132:
118:
117:Deianiraeaceae"
99:
57:
56:
33:
21:
1719:
1718:
1714:
1713:
1712:
1710:
1709:
1708:
1684:
1683:
1682:
1681:
1619:
1617:
1612:
1604:
1599:
1591:
1586:
1578:
1576:
1568:
1563:
1555:
1550:
1542:
1537:
1529:
1524:
1516:
1511:
1503:
1498:
1490:
1485:
1477:
1472:
1464:
1459:
1450:
1449:
1444:
1435:
1434:
1429:
1416:
1406:
1376:
1375:
1371:
1317:
1316:
1312:
1285:Mol. Biol. Evol
1278:
1277:
1273:
1221:
1220:
1216:
1185:(13): 4578–86.
1172:
1171:
1167:
1113:
1112:
1108:
1069:(11): 2373–85.
1056:
1055:
1051:
997:
996:
987:
975:
971:
933:
932:
928:
889:Chlamys farreri
886:
885:
881:
877:
856:
840:Caulobacterales
836:Rhodobacterales
824:
798:
789:
780:
771:
762:
753:
744:
675:Midichloriaceae
657:
648:
639:
543:Anaplasmataceae
497:
428:
405:
367:Caulobacteridae
337:Magnetococcidae
302:Midichloriaceae
294:
204:Repentibacter"
142:Midichloriaceae
98:
51:
17:
12:
11:
5:
1717:
1715:
1707:
1706:
1701:
1696:
1686:
1685:
1680:
1679:
1672:
1665:
1657:
1654:
1653:
1636:
1614:
1613:
1611:
1610:
1597:
1584:
1574:
1561:
1548:
1535:
1522:
1509:
1496:
1483:
1470:
1457:
1442:
1426:
1424:
1418:
1417:
1412:
1405:
1404:
1385:(10): 511–20.
1369:
1310:
1291:(2): 599–615.
1271:
1214:
1165:
1126:(12): e83383.
1106:
1049:
1010:(12): e83383.
985:
969:
942:(10): 741–51.
926:
878:
876:
873:
855:
852:
823:
820:
817:
816:
800:
799:
795:
794:
791:
790:
786:
785:
782:
781:
777:
776:
773:
772:
768:
767:
764:
763:
759:
758:
755:
754:
750:
749:
746:
745:
741:
740:
737:
736:
726:
723:
722:
719:
718:
708:
703:
701:
698:Rickettsiaceae
693:
692:
689:
688:
678:
668:
666:
663:
662:
659:
658:
654:
653:
650:
649:
645:
644:
641:
640:
636:
635:
632:
631:
621:
618:
617:
614:
613:
603:
598:
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588:
578:
573:
571:
568:
567:
564:
563:
553:
548:
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531:
530:
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466:
456:
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420:
393:
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389:
386:
385:
377:
372:
370:
360:
358:
355:
354:
351:
350:
340:
330:
327:
326:
298:Rickettsiaceae
293:
290:
231:
230:
229:
228:
227:
226:
216:Sinorickettsia
212:
198:
181:incertae sedis
176:
162:
156:Rickettsiaceae
152:
135:
125:
108:
107:
103:
102:
93:
89:
88:
83:
79:
78:
76:Pseudomonadota
73:
69:
68:
63:
59:
58:
45:
44:
35:
34:
26:
25:
24:Rickettsiales
15:
13:
10:
9:
6:
4:
3:
2:
1716:
1705:
1702:
1700:
1697:
1695:
1694:Rickettsiales
1692:
1691:
1689:
1678:
1673:
1671:
1666:
1664:
1659:
1658:
1652:
1650:
1646:
1642:
1637:
1634:
1629:
1625:
1620:
1607:
1602:
1598:
1594:
1589:
1585:
1581:
1575:
1571:
1566:
1562:
1558:
1557:rickettsiales
1553:
1549:
1545:
1540:
1536:
1532:
1527:
1523:
1519:
1514:
1510:
1506:
1501:
1497:
1493:
1488:
1484:
1480:
1475:
1471:
1467:
1462:
1458:
1453:
1452:Rickettsiales
1447:
1443:
1438:
1432:
1428:
1427:
1425:
1423:
1422:Rickettsiales
1419:
1415:
1410:
1400:
1396:
1392:
1388:
1384:
1380:
1373:
1370:
1365:
1361:
1356:
1351:
1346:
1341:
1337:
1333:
1330:(1): e30520.
1329:
1325:
1321:
1314:
1311:
1306:
1302:
1298:
1294:
1290:
1286:
1282:
1275:
1272:
1267:
1263:
1258:
1253:
1249:
1245:
1241:
1237:
1233:
1229:
1225:
1218:
1215:
1210:
1206:
1201:
1196:
1192:
1188:
1184:
1180:
1176:
1169:
1166:
1161:
1157:
1152:
1147:
1142:
1137:
1133:
1129:
1125:
1121:
1117:
1110:
1107:
1102:
1098:
1093:
1088:
1084:
1080:
1076:
1072:
1068:
1064:
1060:
1053:
1050:
1045:
1041:
1036:
1031:
1026:
1021:
1017:
1013:
1009:
1005:
1001:
994:
992:
990:
986:
983:
979:
973:
970:
965:
961:
957:
953:
949:
945:
941:
937:
930:
927:
922:
918:
914:
910:
906:
902:
898:
894:
890:
883:
880:
874:
872:
870:
866:
862:
861:genetic drift
853:
851:
849:
843:
841:
837:
833:
827:
821:
814:
810:
806:
802:
801:
793:
792:
784:
783:
775:
774:
766:
765:
757:
756:
748:
747:
739:
738:
735:
734:
733:
725:
724:
721:
720:
717:
716:
715:
707:
706:
700:
699:
695:
694:
691:
690:
687:
686:
685:
677:
676:
672:
671:
665:
664:
661:
660:
652:
651:
643:
642:
634:
633:
630:
629:
628:
620:
619:
616:
615:
612:
611:
610:
602:
601:
595:
594:
591:
590:
587:
586:
585:
577:
576:
570:
569:
566:
565:
562:
561:
560:
559:Neorickettsia
552:
551:
545:
544:
540:
539:
533:
532:
529:
528:
525:
524:
517:
516:
510:
509:
508:Rickettsiales
505:
504:
501:
500:
492:
491:
488:
483:
482:
479:
478:
475:
474:
473:
465:
464:
460:
459:
453:
452:
448:
447:
441:
440:
436:
435:
432:
431:
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422:
419:
417:
413:
409:
403:
399:
392:
391:
388:
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384:
383:
376:
375:
369:
368:
364:
363:
357:
356:
353:
352:
349:
348:
347:
339:
338:
334:
333:
329:
328:
325:
321:
320:
317:
315:
311:
310:Holosporaceae
307:
306:Ehrlichiaceae
303:
299:
291:
289:
286:
284:
280:
276:
272:
268:
267:
262:
261:
256:
255:
250:
246:
242:
238:
237:Rickettsiales
223:
217:
213:
209:
203:
199:
195:
189:
185:
184:
183:
182:
177:
173:
167:
163:
158:
157:
153:
149:
143:
141:
136:
131:
130:
129:Ehrlichiaceae
126:
122:
116:
112:
111:
109:
104:
97:
96:Rickettsiales
94:
91:
90:
87:
84:
81:
80:
77:
74:
71:
70:
67:
64:
61:
60:
55:
50:
46:
42:
41:
36:
32:
27:
22:
19:
1649:expanding it
1638:
1618:
1421:
1382:
1379:Trends Genet
1378:
1372:
1327:
1323:
1313:
1288:
1284:
1281:Andersson SG
1274:
1231:
1227:
1217:
1182:
1179:J. Bacteriol
1178:
1168:
1123:
1119:
1109:
1066:
1062:
1052:
1007:
1003:
972:
939:
935:
929:
896:
892:
888:
882:
857:
844:
828:
825:
804:
730:
728:
712:
710:
696:
682:
680:
673:
625:
623:
607:
605:
582:
580:
557:
555:
541:
520:
507:
506:
486:
472:Pelagibacter
470:
468:
461:
449:
439:Rickettsidae
437:
415:
395:
382:Holosporales
379:
365:
344:
342:
335:
313:
295:
287:
281:and related
279:mitochondria
264:
258:
252:
240:
236:
234:
221:
215:
207:
201:
193:
187:
179:
171:
165:
154:
147:
139:
127:
120:
114:
95:
38:
18:
1513:iNaturalist
1446:Wikispecies
893:Aquaculture
684:Midichloria
247:. They are
241:rickettsias
1688:Categories
899:: 736565.
875:References
732:Rickettsia
314:Candidatus
304:, and the
283:organelles
254:Rickettsia
202:Candidatus
188:Candidatus
166:Candidatus
140:Candidatus
115:Candidatus
921:233921822
842:instead.
627:Ehrlichia
609:Anaplasma
584:Wolbachia
266:Wolbachia
260:Ehrlichia
146:Montagna
119:Castelli
106:Families
1431:Wikidata
1399:17822801
1364:22291975
1324:PLOS ONE
1305:21900598
1266:22355532
1209:17483224
1160:24349502
1120:PLOS ONE
1101:25848874
1044:24349502
1004:PLOS ONE
964:12816914
956:18794912
714:Orientia
192:Vannini
72:Phylum:
66:Bacteria
62:Domain:
1437:Q136644
1355:3264578
1332:Bibcode
1257:3216501
1236:Bibcode
1228:Sci Rep
1200:1913456
1151:3859672
1128:Bibcode
1092:4497978
1071:Bibcode
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271:Genetic
178:Genera
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82:Class:
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1577:NZOR:
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1492:1RICKO
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196:. 2010
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170:Kroer
150:. 2013
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1526:IRMNG
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960:S2CID
917:S2CID
222:et al
208:et al
194:et al
172:et al
148:et al
121:et al
1645:stub
1565:NCBI
1552:LPSN
1539:ITIS
1500:GBIF
1487:EPPO
1479:3349
1395:PMID
1360:PMID
1301:PMID
1262:PMID
1205:PMID
1156:PMID
1097:PMID
1040:PMID
978:ISBN
952:PMID
863:and
838:and
235:The
1570:766
1544:599
1505:646
1474:EoL
1461:CoL
1387:doi
1350:PMC
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1293:doi
1252:PMC
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1195:PMC
1187:doi
1183:189
1146:PMC
1136:doi
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