Inhibitory effect of biofilm-forming Lactobacillus plantarum PA21 isolated from tropical plant pandanus on foodborne pathogens
Bacterial biofilms are a preferred mode of growth for many types of microorganisms in their natural environments. The ability of pathogens to integrate within a biofilm is pivotal to their survival. Alternatively, new opportunities are now arising with the rapidly expanding potential of lactic ac...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/70190/1/FBSB%202017%2017%20-%20IR.pdf |
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| Summary: | Bacterial biofilms are a preferred mode of growth for many types of microorganisms
in their natural environments. The ability of pathogens to integrate within a biofilm
is pivotal to their survival. Alternatively, new opportunities are now arising with the
rapidly expanding potential of lactic acid bacteria (LAB) biofilms as biocontrol
agents against foodborne pathogens. The present study was carried out to evaluate
the effectiveness of a new Lactobacillus plantarum PA21 against several pathogenic
and food-spoilage bacteria in the biofilm and planktonic phases. In addition, the
attention was focused on the use of this isolate as a new host to investigate
Lactobacillus key regulatory proteins in biofilm formation for further
biotechnological applications.
Towards this objective, LAB was isolated from tropical plant Pandanus
amaryllifolius. A new isolate was identified as Lactobacillus plantarum PA21 which
showed biofilm formation in either pure culture and or in combination with several
pathogenic and food-spoilage bacteria, such as Salmonella enterica, Bacillus cereus,
Pseudomonas fluorescens, and Aeromonas hydrophila. Exposure to Lb. plantarum
PA21 has significantly reduced the number of P. fluorescens, A. hydrophila and B.
cereus cells in the planktonic and biofilm forms over 2-, 4- and 6-day time periods.
However, despite the reduction in S. enterica cells, this pathogen showed the most
resistance when co-cultured with Lb. plantarum PA21 and could not be eliminated
entirely, either in the planktonic or biofilm phase.
Lb. plantarum PA21 was also found to be able to constitutively express gfp (green
fluorescent protein) gene when transformed with the expression vector pMG36e,
suggesting its capability of being a host for heterologous protein production. Moreover, the gene expression ability of PA21 has allowed the identification the
EAL containing protein for the first time in Lactobacillus spp, which inversely
regulates biofilm formation and acts as a key regulatory protein in biofilm dispersal.
By reading the optical density and viable cell count results, EAL21 overexpression in
PA21 showed decreased adhesion compared to the wild type strain and significantly
lowered the mean of cell counting results by 4.7 log. |
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