Document Detail

Macro-level and genetic-level responses of Bacillus subtilis to shear stress.
MedLine Citation:
PMID:  14656143     Owner:  NLM     Status:  MEDLINE    
Responses of bacterial (Bacillus subtilis) cells under different shear levels, from both the macro and genetic viewpoints, have been presented. The responses were studied using a novel, couette flow bioreactor (CFB), in which the entire cultivation can be performed under defined shear conditions. Oxygen supply, the normal limiting factor for entire cultivations under defined shear conditions, has been achieved by passing air through a poly(tetrafluoroethylene) (PTFE) membrane fixed on the inner cylinder of the CFB. More importantly, analyses of the oxygen transfer capabilities as well as the shear rates show that in this CFB, the effects of defined shear can be studied without interference from the effects of oxygen supply. Further, the shake flask can be used as a proper control for studying the shear effects, mainly because the shear rate in the shake flask under normal shaker operating conditions of 190 rpm has been estimated to be a negligible 0.028 s(-1) compared to a value of 445 s(-1) at the lowest rpm employed in the CFB. At the macro level the cell size decreased by almost 50% at 1482 s(-1) compared to that at 0.028 s(-1), the growth rate increased by 245%, and the maximum cell concentration increased by 190% when the shear rate was increased from 0.028 to 1482 s(-1). The specific intracellular catalase level increased by 335% and protease by 87% at 1482 s(-1) as compared to the control cultures at a shear rate 0.028 s(-1). In addition, the specific intracellular reactive oxygen species level (siROS) at the highest shear rate was 9.3-fold compared to the control conditions. At the genetic level we have established the involvement of the transcription factor, sigma(B), in the bacterial responses to shear stress, which was unknown in the literature thus far; the sigma(B) expression correlated inversely with the siROS. Further, through experiments with ROS quenchers, we showed that ROS regulated sigma(B) expression under shear.
Susmita Sahoo; Rajesh K Verma; A K Suresh; K Krishnamurthy Rao; Jayesh Bellare; G K Suraishkumar
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Publication Detail:
Type:  Comparative Study; Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biotechnology progress     Volume:  19     ISSN:  8756-7938     ISO Abbreviation:  Biotechnol. Prog.     Publication Date:    2003 Nov-Dec
Date Detail:
Created Date:  2003-12-05     Completed Date:  2004-08-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8506292     Medline TA:  Biotechnol Prog     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1689-96     Citation Subset:  IM    
Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076 India.
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MeSH Terms
Adaptation, Physiological / physiology
Bacillus subtilis / cytology*,  physiology*
Bioreactors / microbiology
Catalase / metabolism*
Cell Culture Techniques / methods
Cell Division / physiology
Cell Size / physiology
Flow Cytometry / methods
Gene Expression Regulation, Bacterial / physiology*
Homeostasis / physiology
Mechanotransduction, Cellular / physiology*
Reactive Oxygen Species / metabolism*
Shear Strength
Stress, Mechanical
Transcription Factors / metabolism*
Reg. No./Substance:
0/Reactive Oxygen Species; 0/Transcription Factors; EC

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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