SinR is a mutational target for fine-tuning biofilm formation in laboratory-evolved strains of Bacillus subtilis

BMC Microbiology

Anna L McLoon⁴  Joseph S Spina³  Laura C Arboleda²  Sara A Leiman¹ 

[1] Department of Molecular and Cellular Biology, Harvard University, Cambridge 02138, MA, USA;Biology Department, Colgate University, Hamilton 13346, NY, USA;Current address: Channing Division of Network Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston 02115, MA, USA;Current address: Department of Ecophysiology, MPI for Terrestrial Microbiology, Marburg, D-35043, Germany

关键词: Selection;    Laboratory;    Domestication;    Biofilms;    Bacteria;    Adaptation;   

Others  :  1137701
DOI  :  10.1186/s12866-014-0301-8

 received in 2014-06-17, accepted in 2014-11-18,  发布年份 2014

【 摘 要 】

Background

Bacteria often form multicellular, organized communities known as biofilms, which protect cells from a variety of environmental stresses. During biofilm formation, bacteria secrete a species-specific matrix; in Bacillus subtilis biofilms, the matrix consists of protein polymers and exopolysaccharide. Many domesticated strains of B. subtilis have a reduced ability to form biofilms, and we conducted a two-month evolution experiment to test whether laboratory culturing provides selective pressure against biofilm formation in B. subtilis.

Results

Bacteria grown in two-month-long batch culture rapidly diversified their biofilm-forming characteristics, exhibiting highly diverse colony morphologies on LB plates in the initial ten days of culture. Generally, this diversity decreased over time; however, multiple types of colony morphology remained in our final two-month-old populations, both under shaking and static conditions. Notably, while our final populations featured cells that produce less biofilm matrix than did the ancestor, cells overproducing biofilm matrix were present as well. We took a candidate-gene approach to identify mutations in the strains that overproduced matrix and found point mutations in the biofilm-regulatory gene sinR. Introducing these mutations into the ancestral strain phenocopied or partially phenocopied the evolved biofilm phenotypes.

Conclusions

Our data suggest that standard laboratory culturing conditions do not rapidly select against biofilm formation. Although biofilm matrix production is often reduced in domesticated bacterial strains, we found that matrix production may still have a fitness benefit in the laboratory. We suggest that adaptive specialization of biofilm-forming species can occur through mutations that modulate biofilm formation as in B. subtilis.

【 授权许可】

   
2014 Leiman et al.; licensee BioMed Central Ltd.

【 图 表 】

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