Abstract:
:Many pathogenic bacteria translocate virulence factors into their eukaryotic hosts by means of type IV secretion systems (T4SS) spanning the inner and outer membranes. Genes encoding components of these systems have been identified within the order Rickettsiales based upon their sequence similarities to other prototypical systems. Anaplasma phagocytophilum strains are obligate intracellular, tick-borne bacteria that are members of this order. The organization of these components at the genomic level was determined in several Anaplasma phagocytophilum strains, showing overall conservation, with the exceptions of the virB2 and virB6 genes. The virB6 loci are characterized by the presence of four virB6 copies (virB6-1 through virB6-4) arranged in tandem within a gene cluster known as the sodB-virB operon. Interestingly, the virB6-4 gene varies significantly in length among different strains due to extensive tandem repeats at the 3' end. To gain an understanding of how these enigmatic virB6 genes function in A. phagocytophilum, we investigated their expression in infected human and tick cells. Our results show that these genes are expressed by A. phagocytophilum replicating in both cell types and that VirB6-3 and VirB6-4 proteins are surface exposed. Analysis of an A. phagocytophilum mutant carrying the Himar1 transposon within the virB6-4 gene demonstrated that the insertion not only disrupted its expression but also exerted a polar effect on the sodB-virB operon. Moreover, the altered expression of genes within this operon was associated with the attenuated in vitro growth of A. phagocytophilum in human and tick cells, indicating the importance of these genes in the physiology of this obligate intracellular bacterium in such different environments.IMPORTANCE Knowledge of the T4SS is derived from model systems, such as Agrobacterium tumefaciens The structure of the T4SS in Rickettsiales differs from the classical arrangement. These differences include missing and duplicated components with structural alterations. Particularly, two sequenced virB6-4 genes encode unusual C-terminal structural extensions resulting in proteins of 4,322 (GenBank accession number AGR79286.1) and 9,935 (GenBank accession number ANC34101.1) amino acids. To understand how the T4SS is used in A. phagocytophilum, we describe the expression of the virB6 paralogs and explore their role as the bacteria replicate within its host cell. Conclusions about the importance of these paralogs for colonization of human and tick cells are supported by the deficient phenotype of an A. phagocytophilum mutant isolated from a sequence-defined transposon insertion library.
journal_name
J Bacterioljournal_title
Journal of bacteriologyauthors
Crosby FL,Munderloh UG,Nelson CM,Herron MJ,Lundgren AM,Xiao YP,Allred DR,Barbet AFdoi
10.1128/JB.00301-20subject
Has Abstractpub_date
2020-11-04 00:00:00issue
23eissn
0021-9193issn
1098-5530pii
JB.00301-20journal_volume
202pub_type
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pub_type: 杂志文章
doi:10.1128/JB.139.3.917-923.1979
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abstract::Biberstein, Ernst L. (University of California, Davis) and Patricia D. Spencer. Oxidative metabolism of Haemophilus species grown at different levels of hemin supplementation. J. Bacteriol. 84:916-920. 1962.-Haemophilus strains were propagated on hemin-deficient and hemin-supplemented media and tested on various subst...
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pub_type: 杂志文章
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doi:10.1128/jb.178.3.902-905.1996
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更新日期:1982-07-01 00:00:00
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journal_title:Journal of bacteriology
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更新日期:1981-05-01 00:00:00
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更新日期:1975-01-01 00:00:00
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更新日期:2005-08-01 00:00:00
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pub_type: 杂志文章
doi:10.1128/jb.178.11.3207-3211.1996
更新日期:1996-06-01 00:00:00
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更新日期:1963-09-01 00:00:00
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更新日期:1972-10-01 00:00:00
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更新日期:1979-01-01 00:00:00
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pub_type: 杂志文章
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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更新日期:1988-12-01 00:00:00
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