Competitive exclusion as a mode of action of a novel Bacillus cereus aquaculture biological agent

Aims:  To determine the contribution of potential modes of action of a Bacillus cereus aquaculture biological control agent in inhibition of the fish pathogen, Aeromonas hydrophila. Methods and Results:  When B. cereus was tested in plate well inhibition studies, no production of antimicrobial compo...

Full description

Saved in:
Bibliographic Details
Published in:Letters in applied microbiology Vol. 50; no. 6; pp. 563 - 570
Main Authors: Lalloo, R., Moonsamy, G., Ramchuran, S., Görgens, J., Gardiner, N.
Format: Journal Article
Language:English
Published: Oxford, UK Blackwell Publishing Ltd 01-06-2010
Blackwell
Subjects:
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Aims:  To determine the contribution of potential modes of action of a Bacillus cereus aquaculture biological control agent in inhibition of the fish pathogen, Aeromonas hydrophila. Methods and Results:  When B. cereus was tested in plate well inhibition studies, no production of antimicrobial compounds was detected. Bacillus cereus had a high growth rate (0·96 h−1), whereas Aer. hydrophila concentration decreased by c. 70% in co‐culture experiments. In nutrient limitation studies, B. cereus had a significantly higher growth rate when cultured under glucose (P < 0·05) and iron (P < 0·01) limitation in comparison with Aer. hydrophila. Bacillus cereus glucose (0·30 g l−1 h−1) and iron (0·60 mg l−1 h−1) uptake rates were also significantly higher (P < 0·01) than the Aer. hydrophila glucose (0·14 g l−1 h−1) and iron (0·43 mg l−1 h−1) uptake rates. Iron uptake was facilitated by siderophore production shown in time profile studies where relative siderophore production was c. 60% through the late exponential and sporulation phases. Conclusions:  Competitive exclusion by higher growth rate, competition for organic carbon and iron, facilitated by siderophore production, could be identified as mechanisms of pathogen growth inhibition by B. cereus. Significance and Impact of the Study:  This study is the first elucidation of the mechanism of action of our novel B. cereus biological agent in growth attenuation of pathogenic Aer. hydrophila. This study enhances the application knowledge and attractiveness for adoption of B. cereus NRRL 100132 for exploitation in aquaculture.
Bibliography:Present address: S. Ramchuran, LIFElab, PO Box 30603, Mayville 4082, South Africa.
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0266-8254
1472-765X
DOI:10.1111/j.1472-765X.2010.02829.x