Document Detail

Effect of oxidative stress on the growth of magnetic particles in Magnetospirillum magneticum.
MedLine Citation:
PMID:  19440983     Owner:  NLM     Status:  MEDLINE    
Individual magnetosome-containing magnetic mineral particles (MMP) from magnetotactic bacteria grow rapidly such that only a small fraction (5%) of all magnetosomes contain dwarf (< or =20 nm) MMP. Studies of the developmental stages in the growth of MMP are difficult due to the absence of techniques to separate dwarf from mature particles and because the former are sensitive to extraction procedures. Here, O2 stress was used to inhibit MMP expression in Magnetospirillum magneticum strain AMB-1. In addition, defined growth conditions not requiring chemical monitoring or manipulation of the gas composition during growth resulted in the production of cells containing high numbers of dwarf MMP. Cells exposed to different incubation treatments and cells with dwarf MMP were compared to cells with normal MMP with respect to growth, respiration, iron content, and relative magnetite load (RML). The cells were examined by electron microscopy, low temperature magnetometry, X-ray diffraction (XRD), and Mössbauer spectroscopy. In the 0-110 microM O2(aq) range, growth was positively correlated with [O2] and negatively correlated with RML. Most MMP formed during exponential growth of the cells. At 50-100 microM O2(aq) with stirring (150 rpm) and 30% O2 loss during incubation, MMP expression was strongly inhibited whereas MMP nucleation was not. Cells highly enriched (~95%) in dwarf MMP were obtained at the end of the exponential phase in stirred (150 rpm) cultures containing 45 microM O2(aq). Only one dwarf MMP formed in each MMP vesicle and the chain arrangement was largely preserved. O2-stress-induced dwarf MMP consisted of non-euhedral spheroids (~25 nm) that were similar in shape and size to immature MMP from normal cells. They consisted solely of magnetite, with a single domain signature, no superparamagnetic behavior, and magnetic signatures, Fe(II)/Fe(III) ratios, and XRD patterns very similar to those of mature MMP. These results show that O2 stress in liquid cultures amended with an inorganic redox buffer (S2O3 2-/S0) can be used to produce abundant dwarf MMP that are good proxies for studying MMP development.
Radu Popa; Wen Fang; Kenneth H Nealson; Virginia Souza-Egipsy; Thelma S Berquó; Subir K Benerjee; Lee R Penn
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  International microbiology : the official journal of the Spanish Society for Microbiology     Volume:  12     ISSN:  1618-1905     ISO Abbreviation:  Int. Microbiol.     Publication Date:  2009 Mar 
Date Detail:
Created Date:  2009-05-14     Completed Date:  2009-06-05     Revised Date:  2009-10-28    
Medline Journal Info:
Nlm Unique ID:  9816585     Medline TA:  Int Microbiol     Country:  Spain    
Other Details:
Languages:  eng     Pagination:  49-57     Citation Subset:  IM    
Portland State University, Oregon 97201, USA.
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MeSH Terms
Magnetospirillum / growth & development*,  metabolism,  ultrastructure
Organelles / metabolism*,  ultrastructure
Oxidative Stress*
Spectroscopy, Mossbauer
X-Ray Diffraction

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