Characterization of biofilm formation in Bacillus subtilis isolated from radiation and non radiation-emitting hot springs
Biofilms can be defined as a bacterial communication form, in which the bacteria adhere to surfaces and to each others using slimy, glue-like substances called the extra-cellular matrixes. Production of biofilms is a critical key for the bacteria to express multiple kinds of biological processes,...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/114142/1/114142.pdf |
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| Summary: | Biofilms can be defined as a bacterial communication form, in which the bacteria adhere
to surfaces and to each others using slimy, glue-like substances called the extra-cellular
matrixes. Production of biofilms is a critical key for the bacteria to express multiple kinds
of biological processes, including resistance against sanitizers and environmental stresses.
Ramsar hot spring, is an active, radon-containing hot spring situated in north of Iran, has
the highest background of natural radiation in the world (260 mGy/year). Investigation of
the microbial biofilm formation in these environments may contribute to understand their
significance in food industries, in terms of cellular resistance to environmental stresses
and to ionizing sterilization methods commonly used for food materials and equipment.
In this work, B. subtilis (RAM-04) was isolated from water and mud samples obtained
from Ramsar hot spring, and was found to survive following exposure to 20 kGy gamma
radiation with a viable growth of 20 CFU/mL. B. subtilis (GAD-28) was isolated from
water and biofilm samples obtained from Gadek hot spring, Malaysia, where no dose of
natural radiation was reported, and was therefore used as a control. Biofilm Formation
assay was performed using Microtitre Plate technique and Scanning Electron Microscopy
(SEM). Gene expression analysis to quantify the critical genes involved in B. subtilis
biofilm formation was performed using direct sequencing method and quantitative PCR
(q-PCR). Biofilm formation under food-related stresses, including incubation time,
temperature, pH, nutrient concentration, and subsequent chlorine treatment, was also
estimated using the Microtitre Plate technique for both isolates. Results of the Microtitre
Plate technique and the Scanning Electron Microscopy showed that RAM-04 formed
stronger biofilms compared with GAD-28. In addition, the results of gene expression
analysis of RAM-04 revealed that of 13 genes in total, seven genes showed genetic
variations at multiple places in the genome sequences. The q-PCR revealed an up
regulation of yqxM-sipW-tasA operon genes in RAM-04 with the folding change of 13, 11,
and 8 respectively, and a down regulation in both ccpA and slrR genes with the folding
change of 0.2 and 0.3 respectively. There was a marked variability in the food-related
stress profiling, in which temperature, pH and media concentration showed a significant
effect on biofilm formation by both isolates, whereas, chlorine and incubation time had a
non-significant effect. As a conclusion, RAM-04 was able to produce a biofilm three times
stronger compared to that of GAD-28. In addition, assuming that RAM-04 utilizes the
operon yqxM-sipW-tasA to produce the extracellular matrix that is necessary to build such
a strong architecture of cell associations or biofilms. This in turn will be potential strategies
to survive and resist extreme ionizing environmental stress. However, the biofilm
formation under food-related-stress offers possible practical applications, like usage of
physical applications (sub-thermal temperatures and nutrient deficiency) to control the
development of biofilms in both isolates. On the other hand, the research highlighted the
possible disadvantage of chlorine usage as an active sanitizer in food industries. |
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