Effect of modeled reduced gravity conditions on bacterial morphology and physiology

BMC Microbiology

Research Article

Michael A Model¹  Laura G Leff¹  Raja Vukanti² 

[1]Department of Biological Sciences, Kent State University, P. O. Box: 5190, 44242, Kent, OH, USA

[2]Department of Biological Sciences, Kent State University, P. O. Box: 5190, 44242, Kent, OH, USA

[3]Earth Research Institute, University of California, 93106, Santa Barbara, CA, USA

关键词: Membrane Potential;    Luria Bertani;    Normal Gravity;    Bacterial Response;    Rotate Cell Culture System;   

DOI  :  10.1186/1471-2180-12-4

 received in 2011-06-22, accepted in 2012-01-12,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundBacterial phenotypes result from responses to environmental conditions under which these organisms grow; reduced gravity has been demonstrated in many studies as an environmental condition that profoundly influences microorganisms. In this study, we focused on low-shear stress, modeled reduced gravity (MRG) conditions and examined, for Escherichia coli and Staphlyococcus aureus, a suite of bacterial responses (including total protein concentrations, biovolume, membrane potential and membrane integrity) in rich and dilute media and at exponential and stationary phases for growth. The parameters selected have not been studied in E. coli and S. aureus under MRG conditions and provide critical information about bacterial viability and potential for population growth.ResultsWith the exception of S. aureus in dilute Luria Bertani (LB) broth, specific growth rates (based on optical density) of the bacteria were not significantly different between normal gravity (NG) and MRG conditions. However, significantly higher bacterial yields were observed for both bacteria under MRG than NG, irrespective of the medium with the exception of E. coli grown in LB. Also, enumeration of cells after staining with 4',6-diamidino-2-phenylindole showed that significantly higher numbers were achieved under MRG conditions during stationary phase for E. coli and S. aureus grown in M9 and dilute LB, respectively. In addition, with the exception of smaller S. aureus volume under MRG conditions at exponential phase in dilute LB, biovolume and protein concentrations per cell did not significantly differ between MRG and NG treatments. Both E. coli and S. aureus had higher average membrane potential and integrity under MRG than NG conditions; however, these responses varied with growth medium and growth phase.ConclusionsOverall, our data provides novel information about E. coli and S. aureus membrane potential and integrity and suggest that bacteria are physiologically more active and a larger percentage are viable under MRG as compared to NG conditions. In addition, these results demonstrate that bacterial physiological responses to MRG conditions vary with growth medium and growth phase demonstrating that nutrient resources are a modulator of response.

【 授权许可】

Unknown   
© Vukanti et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.