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Updated: Jun 10, 2026
Adherence of Bacteria to Plant Surfaces Measured in the Laboratory
Published on: June 19, 2018
Gamma-polyglutamic acid (gamma-PGA) produced by Bacillus amyloliquefaciens C06 promoting its colonization on fruit
1Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Nanjing, People's Republic of China.
Abstract:
Bacillus amyloliquefaciens C06, an effective biological agent in controlling brown rot of stone fruit caused by Monilinia fructicola, was also found to produce extra-cellular mucilage and form mucoid colonies on semi-solid surfaces. This study aimed to characterize the extra-cellular mucilage produced by B. amyloliquefaciens C06 using transposon mutagenesis and biochemical and physical analyses. The mucilage production in B. amyloliquefaciens C06 was demonstrated to be associated with ywsC gene expression and characterized to be of high molecular weight, consisted of only glutamic acid and linked with non-peptide bonds, thus identified as gamma-polyglutamic acid (gamma-PGA). Compared with wild type B. amyloliquefaciens C06, its mutants deficient in producing gamma-PGA, e.g. M106 and C06DeltaywsC showed less efficiency in biofilm formation, surface adhesion and swarming ability. It was also demonstrated that gamma-PGA was not essential for C06 to form colony on semi-solid surfaces, but was able to improve its colony structure. In vivo evaluation showed that disruption of gamma-PGA production in C06DeltaywsC impaired its efficiency of colonizing apple surfaces.
Insights
Bacillus amyloliquefaciens C06 produces gamma-polyglutamic acid (gamma-PGA), a substance crucial for its biofilm formation, surface adhesion, and swarming abilities. This finding highlights gamma-PGA
Area of Science:
- Microbiology
- Biochemistry
- Plant Pathology
Background:
- Bacillus amyloliquefaciens C06 is an effective biocontrol agent against Monilinia fructicola, a pathogen causing brown rot in stone fruits.
- This bacterium produces extracellular mucilage, contributing to mucoid colony formation on semi-solid media.
Purpose of the Study:
- To characterize the extracellular mucilage produced by Bacillus amyloliquefaciens C06.
- To investigate the role of this mucilage in the bacterium's biological functions and pathogenicity.
Main Methods:
- Transposon mutagenesis was employed to identify genes involved in mucilage production.
- Biochemical and physical analyses were conducted to determine the composition and properties of the mucilage.
- Mutant strains deficient in mucilage production were compared to the wild type for various functional assays.
Main Results:
- The extracellular mucilage was identified as high-molecular-weight gamma-polyglutamic acid (gamma-PGA), synthesized via the ywsC gene.
- Mutants lacking gamma-PGA exhibited reduced biofilm formation, surface adhesion, and swarming motility.
- While not essential for colony formation, gamma-PGA enhanced colony structure and in vivo colonization efficiency on apple surfaces.
Conclusions:
- Gamma-polyglutamic acid (gamma-PGA) plays a significant role in the exopolysaccharide matrix of Bacillus amyloliquefaciens C06.
- Gamma-PGA production is vital for the bacterium's surface-associated behaviors and effective colonization.
- Understanding gamma-PGA's function provides insights into the biocontrol mechanisms of Bacillus amyloliquefaciens C06.
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