Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division

ABSTRACT The Lyme disease spirochete Borrelia burgdorferi migrates to distant sites in the tick vectors and mammalian hosts through robust motility and chemotaxis activities. FliH and FliI are two cytoplasmic proteins that play important roles in the type III secretion system (T3SS)-mediated export...

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Autores principales:	Tao Lin, Lihui Gao, Xiaowei Zhao, Jun Liu, Steven J. Norris
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
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spelling	oai:doaj.org-article:fbe7ffca67194440bace77fe945dbc792021-11-15T15:49:02ZMutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division10.1128/mBio.00579-152150-7511https://doaj.org/article/fbe7ffca67194440bace77fe945dbc792015-07-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00579-15https://doaj.org/toc/2150-7511ABSTRACT The Lyme disease spirochete Borrelia burgdorferi migrates to distant sites in the tick vectors and mammalian hosts through robust motility and chemotaxis activities. FliH and FliI are two cytoplasmic proteins that play important roles in the type III secretion system (T3SS)-mediated export and assembly of flagellar structural proteins. However, detailed analyses of the roles of FliH and FliI in B. burgdorferi have not been reported. In this study, fliH and fliI transposon mutants were utilized to dissect the mechanism of the Borrelia type III secretion system. The fliH and fliI mutants exhibited rod-shaped or string-like morphology, greatly reduced motility, division defects (resulting in elongated organisms with incomplete division points), and noninfectivity in mice by needle inoculation. Mutants in fliH and fliI were incapable of translational motion in 1% methylcellulose or soft agar. Inactivation of either fliH or fliI resulted in the loss of the FliH-FliI complex from otherwise intact flagellar motors, as determined by cryo-electron tomography (cryo-ET). Flagellar assemblies were still present in the mutant cells, albeit in lower numbers than in wild-type cells and with truncated flagella. Genetic complementation of fliH and fliI mutants in trans restored their wild-type morphology, motility, and flagellar motor structure; however, full-length flagella and infectivity were not recovered in these complemented mutants. Based on these results, disruption of either fliH or fliI in B. burgdorferi results in a severe defect in flagellar structure and function and cell division but does not completely block the export and assembly of flagellar hook and filament proteins. IMPORTANCE Many bacteria are able to rapidly transport themselves through their surroundings using specialized organelles called flagella. In spiral-shaped organisms called spirochetes, flagella act like inboard motors and give the bacteria the ability to bore their way through dense materials (such as human tissue) in a corkscrew manner. In this article, we studied how two proteins, called FliH and FliI, are important for the production of full-length flagella in the Lyme disease spirochete Borrelia burgdorferi. Mutants with defective production of FliH and FliI have reduced flagellar length and motility; this deficiency in turn affects many aspects of B. burgdorferi's biology, including the ability to undergo cell division and cause disease in mammals. Using a microscopic computed tomography (CT) scan approach called cryo-electron tomography, the structure that contains FliH and FliI was defined in the context of the flagellar motor, providing clues regarding how this amazing nanomachine is assembled and functions.Tao LinLihui GaoXiaowei ZhaoJun LiuSteven J. NorrisAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 3 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Tao Lin Lihui Gao Xiaowei Zhao Jun Liu Steven J. Norris Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division
description	ABSTRACT The Lyme disease spirochete Borrelia burgdorferi migrates to distant sites in the tick vectors and mammalian hosts through robust motility and chemotaxis activities. FliH and FliI are two cytoplasmic proteins that play important roles in the type III secretion system (T3SS)-mediated export and assembly of flagellar structural proteins. However, detailed analyses of the roles of FliH and FliI in B. burgdorferi have not been reported. In this study, fliH and fliI transposon mutants were utilized to dissect the mechanism of the Borrelia type III secretion system. The fliH and fliI mutants exhibited rod-shaped or string-like morphology, greatly reduced motility, division defects (resulting in elongated organisms with incomplete division points), and noninfectivity in mice by needle inoculation. Mutants in fliH and fliI were incapable of translational motion in 1% methylcellulose or soft agar. Inactivation of either fliH or fliI resulted in the loss of the FliH-FliI complex from otherwise intact flagellar motors, as determined by cryo-electron tomography (cryo-ET). Flagellar assemblies were still present in the mutant cells, albeit in lower numbers than in wild-type cells and with truncated flagella. Genetic complementation of fliH and fliI mutants in trans restored their wild-type morphology, motility, and flagellar motor structure; however, full-length flagella and infectivity were not recovered in these complemented mutants. Based on these results, disruption of either fliH or fliI in B. burgdorferi results in a severe defect in flagellar structure and function and cell division but does not completely block the export and assembly of flagellar hook and filament proteins. IMPORTANCE Many bacteria are able to rapidly transport themselves through their surroundings using specialized organelles called flagella. In spiral-shaped organisms called spirochetes, flagella act like inboard motors and give the bacteria the ability to bore their way through dense materials (such as human tissue) in a corkscrew manner. In this article, we studied how two proteins, called FliH and FliI, are important for the production of full-length flagella in the Lyme disease spirochete Borrelia burgdorferi. Mutants with defective production of FliH and FliI have reduced flagellar length and motility; this deficiency in turn affects many aspects of B. burgdorferi's biology, including the ability to undergo cell division and cause disease in mammals. Using a microscopic computed tomography (CT) scan approach called cryo-electron tomography, the structure that contains FliH and FliI was defined in the context of the flagellar motor, providing clues regarding how this amazing nanomachine is assembled and functions.
format	article
author	Tao Lin Lihui Gao Xiaowei Zhao Jun Liu Steven J. Norris
author_facet	Tao Lin Lihui Gao Xiaowei Zhao Jun Liu Steven J. Norris
author_sort	Tao Lin
title	Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division
title_short	Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division
title_full	Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division
title_fullStr	Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division
title_full_unstemmed	Mutations in the <named-content content-type="genus-species">Borrelia burgdorferi</named-content> Flagellar Type III Secretion System Genes <italic toggle="yes">fliH</italic> and <italic toggle="yes">fliI</italic> Profoundly Affect Spirochete Flagellar Assembly, Morphology, Motility, Structure, and Cell Division
title_sort	mutations in the <named-content content-type="genus-species">borrelia burgdorferi</named-content> flagellar type iii secretion system genes <italic toggle="yes">flih</italic> and <italic toggle="yes">flii</italic> profoundly affect spirochete flagellar assembly, morphology, motility, structure, and cell division
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/fbe7ffca67194440bace77fe945dbc79
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