title: MamX encoded by the mamXY operon is involved in control of magnetosome maturation in Magnetospirillum gryphiswaldense MSR-1.
abstract: BACKGROUND
  Magnetotactic bacteria produce membrane-enveloped magnetite crystals (magnetosomes) whose formation is controlled primarily by a gene island termed the magnetosome island (MAI). Characterization of single gene and operon function in MAI has elucidated in part the genetic basis of magnetosome formation. The mamX gene, located in the mamXY operon, is highly conserved in the MAI of all Magnetospirillum strains studied to date. Little is known regarding the function of mamX in the process of biomineralization.
  
  
  RESULTS
  A mamX deletion mutant (∆mamX) and its complemented strain (CmamX) by conjugation in M. gryphiswaldense strain MSR-1 were constructed. There were no striking differences in cell growth among ∆mamX, CmamX, and wild-type strain (WT). ∆mamX displayed a much weaker magnetic response than WT. Transmission electron microscopy revealed the presence of irregular, superparamagnetic magnetite particles in ∆mamX, in contrast to regular, single-domain particles in WT and CmamX. The phenotype of ∆mamX was similar to that of an ftsZ-like deleted mutant and mamXY operon deleted mutant reported previously. Quantitative real-time RT-PCR (qPCR) results indicated that the deletion of mamX had differential effects on the transcription levels of the other three genes in the operon.
  
  
  CONCLUSIONS
  The MamX protein plays an important role in controlling magnetosome size, maturation, and crystal form. The four MamXY proteins appear to have redundant functions involved in magnetosome formation. Our findings provide new insights into the coordinated function of MAI genes and operons in magnetosome formation.
authors.affiliation: State Key Laboratories for Agro-biotechnology and College of Biological Sciences, China Agricultural University, Beijing 100193, P, R, China. yingli528@vip.sina.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Shuqi
authors.initials: S
authors.lastname: Li
authors.forename: Xiuliang
authors.initials: X
authors.lastname: Huang
authors.forename: Jinhua
authors.initials: J
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Pan
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005816:Genetic Complementation Test; D008124:Locomotion; D055944:Magnetosomes / Q000378:metabolism* / Q000648:ultrastructure; D042201:Magnetospirillum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins
references.citation: Environ Microbiol. 2009 May;11(5):1267-77
references.pmid: 19220405
references.citation: Science. 2006 Jan 13;311(5758):242-5
references.pmid: 16373532
references.citation: Curr Opin Cell Biol. 2012 Aug;24(4):490-5
references.pmid: 22726584
references.citation: J Biol Chem. 2003 Mar 7;278(10):8745-50
references.pmid: 12496282
references.citation: Infect Immun. 2006 May;74(5):2777-86
references.pmid: 16622215
references.citation: J Mol Biol. 1983 Jun 5;166(4):557-80
references.pmid: 6345791
references.citation: Appl Environ Microbiol. 2001 Oct;67(10):4573-82
references.pmid: 11571158
references.citation: Annu Rev Microbiol. 2009;63:501-21
references.pmid: 19575557
references.citation: Biomacromolecules. 2012 Jan 9;13(1):98-105
references.pmid: 22112204
references.citation: Gene. 1988 Oct 15;70(1):191-7
references.pmid: 2853689
references.citation: Environ Microbiol Rep. 2010 Oct;2(5):646-50
references.pmid: 23766250
references.citation: Nature. 2006 Mar 2;440(7080):110-4
references.pmid: 16299495
references.citation: Nat Rev Microbiol. 2004 Mar;2(3):217-30
references.pmid: 15083157
references.citation: Biochem Soc Trans. 2012 Dec 1;40(6):1319-23
references.pmid: 23176475
references.citation: Biotechniques. 1993 Nov;15(5):831-4
references.pmid: 8267974
references.citation: Res Microbiol. 2008 Sep-Oct;159(7-8):530-6
references.pmid: 18639631
references.citation: FEMS Microbiol Rev. 2012 Jan;36(1):232-55
references.pmid: 22092030
references.citation: Mol Microbiol. 2011 May;80(4):1075-87
references.pmid: 21414040
references.citation: PLoS One. 2011;6(10):e25561
references.pmid: 22043287
references.citation: J Bacteriol. 2012 Aug;194(15):3972-6
references.pmid: 22636767
references.citation: J Bacteriol. 2007 Jul;189(13):4899-910
references.pmid: 17449609
references.citation: J Bacteriol. 2005 Nov;187(21):7176-84
references.pmid: 16237001
references.citation: PLoS One. 2012;7(5):e34189
references.pmid: 22586444
references.citation: Mol Microbiol. 2010 Apr;76(2):480-8
references.pmid: 20345667
references.citation: Mol Microbiol. 2012 Aug;85(4):684-99
references.pmid: 22716969
references.citation: J Bacteriol. 2010 Feb;192(4):1097-105
references.pmid: 20023033
references.citation: J Bacteriol. 2008 Jan;190(1):377-86
references.pmid: 17965152
references.citation: Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5593-8
references.pmid: 20212111
references.citation: Appl Microbiol Biotechnol. 2008 Jun;79(3):389-97
references.pmid: 18425510
references.citation: J Biol Chem. 2011 Feb 25;286(8):6386-92
references.pmid: 21169637