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A new α‐proteobacterial clade of Bdellovibrio ‐like predators: implications for the mitochondrial endosymbiotic theory
Author(s) -
Davidov Yaacov,
Huchon Dorothee,
Koval Susan F.,
Jurkevitch Edouard
Publication year - 2006
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2006.01101.x
Subject(s) - biology , endosymbiosis , bdellovibrio , prokaryote , proteobacteria , lineage (genetic) , mutualism (biology) , predation , alphaproteobacteria , phylogenetic tree , phylogenetics , bacteria , ecology , evolutionary biology , gene , genetics , plastid , 16s ribosomal rna , chloroplast
Summary Bdellovibrio ‐and‐like organisms (BALOs) are peculiar, ubiquitous, small‐sized, highly motile Gram‐negative bacteria that are obligatory predators of other bacteria. Typically, these predators invade the periplasm of their prey where they grow and replicate. To date, BALOs constitute two highly diverse families affiliated with the δ‐ proteobacteria class. In this study, Micavibrio spp., a BALO lineage of epibiotic predators, were isolated from soil. These bacteria attach to digest and grow at the expense of other prokaryotes, much like other BALOs. Multiple phylogenetic analyses based on six genes revealed that they formed a deep branch within the α‐ proteobacteria , not affiliated with any of the α‐proteobacterial orders. The presence of BALOs deep among the α‐ proteobacteria suggests that their peculiar mode of parasitism maybe an ancestral character in this proteobacterial class. The origin of the mitochondrion from an α‐ proteobacterium endosymbiont is strongly supported by molecular phylogenies. Accumulating data suggest that the endosymbiont’s host was also a prokaryote. As prokaryotes are unable to phagocytose, the means by which the endosymbiont gained access into its host remains mysterious. We here propose a scenario based on the BALO feeding‐mode to hypothesize a mechanism at play at the origin of the mitochondrial endosymbiosis.