Genome degeneration affects both extracellular and intracellular bacterial endosymbionts

Feldhaar, Heike; Gross, Roy

doi:10.1186/jbiol129

Journal of Biology

Table 1 Comparison of basic features of endosymbiotic and free-living bacteria (ordered by genome size)

From: Genome degeneration affects both extracellular and intracellular bacterial endosymbionts

	Carsonella ruddii	Sulcia muelleri	Buchnera spp.	Mycoplasma genitalium	Blattabacterium spp.	Baumannia cicadellinicola	Wigglesworthia glossinidius
Phylum	γ-Proteobacteria	Bacteroidetes	γ-Proteobacteria	Mollicutes	Bacteroidetes	γ-Proteobacteria	γ-Proteobacteria
Role as symbiont	Obligate, primary, mutualistic	Obligate, primary, mutualistic	Obligate, primary, mutualistic	Pathogen	Obligate, primary, mutualistic	Obligate, primary, mutualistic	Obligate, primary, mutualistic
Host	Psyllids	Sharpshooters	Aphids	Human	Cockroaches	Sharpshooters	Tsetse flies
Genome size (kbp)	160	245	422–686	580	Approximately 650	686	698
GC content (%)	16.5	22.4	20.1–26.2	31.7	Approximately 32	33.2	22.5
Biological function/disease	Nutrition	Nutrition	Nutrition	Genital infections	Nutrition	Nutrition	Nutrition
Location	Intracellular in bacteriocyte	Intracellular in bacteriocyte*	Intracellular in bacteriocyte	Cell associated	Intracellular in bacteriocyte	Intracellular in bacteriocyte*	Intracellular in bacteriocyte
Transmission	Vertical	Vertical	Vertical	Horizontal	Vertical	Vertical	Vertical
	Blochmannia spp.	Cadidatus Ishikawaella capsulata	Cadidatus Rosenkranzia clausaccus	Chlamydia trachomatis	Sodalis glossinidius	Escherichia coli K-12	Sorangium cellulosum
Phylum	γ-Proteobacteria	γ-Proteobacteria	γ-Proteobacteria	Chlamydiae	γ-Proteobacteria	γ-Proteobacteria	Myxobacteria
Role as symbiont	Obligate, primary, mutualistic	Obligate, primary, mutualistic	Obligate, primary, mutualistic	Pathogen	Facultative, secondary, commensal	Commensal	Environment
Host	Carpenter ants	Stinkbugs	Stinkbugs	Human	Tsetse flies	Mammalian intestine	Free-living
Genome size (kbp)	705–792	820–830	900–960	1,043	4,170 (972 pseudogenes)^†	4,639	13,034
GC content (%)	27.4–29.6	38.9 (groEL)^§	36–38 (groEL)^§	41.3	54	51	71.4
Biological function/disease	Nutrition	Unknown	Unknown	Ocular, lung and genital infections	Influences parasite load (Trypanosoma) of host
Location	Intracellular in bacteriocyte	Extracellular in midgut crypts	Extracellular in midgut crypts	Intracellular	Facultative intracellular	Extracellular	Extracellular
Transmission	Vertical	Vertical	Vertical	Horizontal	Horizontal/vertical	Horizontal

*S. muelleri lives with B. cicadellinicola in the same bacteriocyte. ^†The genome size of S. glossinidius is comparable to that of free-living Enterobacteriaceae, but it is in an early state of degeneration, as exemplified by the massive presence of pseudogenes and a coding capacity of only 51%. ^§The GC content of the groEL genes is presented for the stinkbug endosymbionts. In the other sequenced endosymbionts the groEL gene has the highest GC content, indicating that the overall GC content of the stinkbug endosymbionts is probably significantly lower.

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