This study attempted at microwave mutagenesis of: (i) Lactobacillus plantarum for lactic acid overproduction, and (ii) Streptococcus mutans for reduced lactic acid production. Lactic acid is among the microbiological products with high market potential. Lactic acid is also an important virulence factor in formation of dental caries by S. mutans, as the acid produced by the bacteria leads to demineralisation of the teeth. Two of the mutants obtained (one from each organism) were able to maintain the altered lactic acid production till 10 generations. However the magnitude of alteration in lactic acid producing ability of the mutants went on decreasing over generations. The microwave effects observed in this study seem largely to be athermal in nature. Investigation of the mutants obtained at molecular level may result in identification of novel mutations responsible for altered lactic acid production. These mutations can then be introduced into a suitable organism either for better industrial production of lactic acid, or for constructing new probiotic strain(s) for possible application in maintenance of oral health.
Effect of low power (90 W) microwave (2,450 MHz) radiation on bacterial growth and pigment production was studied in three different bacteria. Microwave exposure of 2-6 min duration was able to alter growth and pigment production (prodigiosin production by Serratia marcescens, violacein production by Chormobacterium violaceum, and staphyloxanthin production by Staphylococcus aureus) in the test organisms significantly. In this study, pigment production was estimated in the cell population originated from microwave treated inoculum, and not directly in the MW treated cells. Thus the alterations in pigment production and/or secretion might have been transferred from the originally MW treated cells to their daughter cells (who did not receive direct MW exposure), indicating the mutagenic influence of microwave radiation. Heavy prodigiosin overproduction observed in one of the test tubes inoculated with microwave treated S. marcescens could not be sustained by daughter populations corresponding to that tube, indicating the reversible nature of microwave induced mutation(s). The microwave effects observed in this study largely seem to be of athermal nature, as the thermal effect was minimized by use of ice during the microwave treatment.
Table of Contents
1. Prologue
1.1. Preamble
1.2. The Importance of the Study
1.3. Statement of the Problem
1.4. Rationale of the Research Work
1.5. Objectives:
2. Literature Review
2.1 Interactions of MW with Biological Materials
2.2. Athermal (Non-thermal) Mechanisms of Interaction
2.4 Biological effects of MW radiation
2.5 Microwave Mutagenesis
2.6 MW and cell phones
2.7 Effect of MW on growth and enzyme activity
2.8 Lactic acid
2.9 Microbial pigment production
2.9.1. Pigment produced by Microorganisms
3. Microwave mutagenesis of Streptococcus mutans for reduced lactic acid production
3.1 Materials and Methods
3.1.1. Culture maintenance
3.1.2 Culture activation
3.1.3 Inoculum preparation
3.1.4 MW oven and its maintenance
3.1.5 MW treatment
3.1.6 Growth measurement:
3.1.7 Expermental condition:
3.1.8 Lactic acid estimation:
3.1.8 Experimental outline
3.2 Results and Discussion
4. Microwave mutagenesis of Lactobacillus plantarum for lactic acid overproduction
4.1 Materials and Methods
4.1.1. Culture maintenance
4.1.2 Culture activation
4.1.3 Inoculum preparation
4.1.4 MW oven and its maintenance
4.1.5 MW treatment
4.1.6 Experimental condition:
4.1.7 Lactic acid estimation:
4.1.8 Experimental outline:
4.2.6 Growth measurement:
4.2 Results and Discussion
5. Effect of low power microwave radiation on pigment production of selected bacteria
5.1 Materials and Methods
5.1.1 Culture maintenance
5.1.2. Culture activation
5.1.3. Inoculum preparation
5.1.4. MW oven and its maintenance
5.1.5. MW treatment
5.1.6. MW treatment to inoculum
5.1.7 Growth measurement:
5.1.8. Experimental condition:
5.1.9 Pigment extraction methods:
5.1.10 Calculation for pigment extraction:
5.1.11 Statistical analysis
5.1. Results and Discussion
5.2.1 Effect of low power MW on prodigiosin production
5.2.2. Effect of low power MW treatment on violacein production
5.2.3 Effect of low power MW treatment on staphyloxanthin production:
6. Microwave mutagenesis for the overproduction of prodigiosin from S. marcescens
6.1. Materials and Methods:
6.1.1 Culture maintenance
6.1.2 Culture activation
6.1.3 Inoculum preparation
6.1.4. MW oven and its maintenance
6.1.5 MW treatment
6.1.6 MW treatment to inoculum
6.1.7 Growth measurement:
6.1.8 Experimental condition and prodigiosin extraction method was using described in chapter 5 (5.1.8 and 5.1.9).
6.1.9 Experimental outline:
6.2 Results and Discussion
Research Objectives and Topics
The primary research objective of this study is to investigate the "athermal" effects of low-power microwave (MW) radiation on various microbial systems, specifically focusing on how these exposures influence cellular growth, metabolic activity, and the production of industrially relevant compounds like lactic acid and various bacterial pigments.
- Athermal effects of low-power microwave radiation on microbial physiology.
- Microwave-induced mutagenesis for strain improvement in Streptococcus mutans and Lactobacillus plantarum.
- Modulation of bacterial pigment production (prodigiosin, violacein, staphyloxanthin) under microwave influence.
- Evaluation of genetic stability in microwave-mutated microbial strains over multiple generations.
- Comparison of thermal vs. athermal mechanisms in microbial microwave interaction.
Book Excerpt
2.2. Athermal (Non-thermal) Mechanisms of Interaction
MW radiation seems to affect system in a manner, which cannot be explained by thermal effects alone [Spencer et al., 1985]. MW has ability to destroy bacterial cells at specific parameters without causing heating of the substrate [Barnabas et al., 2010]. MW plays role in dielectric saturation [Hyland, 1988], formation of oxidative stress [Sokolovic et al., 2008], protein unfolding [George et al., 2008], changing the structures by differentially partitioning the ions [Asadi et al., 2011], others chemical transformation of small molecules such as chemical bond cleavage [Oslen, 1966], vibrational resonance in DNA molecules [Edwards et al., 1985]. The oscillating EMF of MW couples energy into large biomolecules with several oscillations. When a large number of dipoles are present in one molecule (DNA, protein, RNA etc.) and kept under MW, enough energy can be transferred to the molecules, which would be able to break the bond.
Biological effects of MW radiation can be divided into two categories: thermal effects and non-thermal effects. Thermal effect is the one in which the MW energy is converted into heat energy in the living systems. These effects can be macroscopic where whole organisms or major portions of them participate in the heat transfer process or microscopic where cellular component like bound water is vaporized by the selective application of the MW heating [Richmond, 1969]. The dielectric effect of MW on polar molecules has been known for more than a century [Debye, 1922]. Polar molecules are present in the cells in the form of water, DNA, and proteins and they respond to an electromagnetic field by rotating. This rotation creates an angular momentum which results in friction with neighbouring molecules, thereby developing a linear momentum (vibrational energy) [Saifuddin et al., 2009]. In this way, radiation energy is converted into thermal energy. Effect generated from vibrational energy is thermal effect which occurs in a biosystem due to penetration of electromagnetic waves (MW) into biological materials and heating up the intra- and extra- cellular fluids by transfer of vibrational energy [Tahir et al., 2009].
Summary of Chapters
1. Prologue: Introduces the background of electromagnetic field interactions with biological systems, defining the role of microwave radiation and the research problem.
2. Literature Review: Provides an overview of known thermal and athermal interaction mechanisms of microwaves with living organisms, including specific studies on microbial effects and pigment production.
3. Microwave mutagenesis of Streptococcus mutans for reduced lactic acid production: Details the experimental approach for using low-power microwave exposure to reduce the lactic acid production capabilities of S. mutans, followed by an analysis of the genetic stability of these mutants.
4. Microwave mutagenesis of Lactobacillus plantarum for lactic acid overproduction: Investigates the use of microwave mutagenesis to enhance lactic acid yields in L. plantarum and assesses the long-term stability of the resulting high-production strains.
5. Effect of low power microwave radiation on pigment production of selected bacteria: Examines how low-power microwave exposure alters the synthesis of pigments like prodigiosin, violacein, and staphyloxanthin in specific bacteria and discusses potential industrial applications.
6. Microwave mutagenesis for the overproduction of prodigiosin from S. marcescens: Focuses on the targeted application of microwave energy to isolate high-yield prodigiosin-producing strains of Serratia marcescens and evaluates the durability of this mutation.
Keywords
Microwave radiation, Athermal effects, Microbial mutagenesis, Lactic acid, Prodigiosin, Violacein, Staphyloxanthin, Strain improvement, Genetic stability, Bio-processing, Electromagnetic fields, Streptococcus mutans, Lactobacillus plantarum, Serratia marcescens
Frequently Asked Questions
What is the core subject of this research work?
The research investigates the influence of microwave radiation on microbial systems, specifically testing the hypothesis that low-power microwaves can induce biological changes through "athermal" mechanisms, distinct from simple heat-based effects.
What are the primary fields of interest covered in this study?
The study spans microbiology, biotechnology, and bio-physics, specifically focusing on microbial mutagenesis, metabolite production, and the physiological response of bacteria to non-ionizing electromagnetic radiation.
What is the primary objective of this work?
The main goal is to explore if low-power microwaves can serve as an effective tool for microbial strain improvement—either by reducing undesirable metabolic outputs, such as lactic acid, or by overproducing valuable substances like pigments and lactic acid.
What scientific methods are utilized in this investigation?
The researchers use controlled low-power microwave exposure (2450 MHz) combined with rigorous ice-bath cooling to isolate athermal effects, followed by microbiological cultivation, spectrophotometric analysis for metabolite quantification, and generation-wise stability testing.
What content is addressed in the main part of the book?
The book details specific experimental protocols and results for three main applications: reducing lactic acid in S. mutans, overproducing lactic acid in L. plantarum, and modulating pigment production in various bacterial species, including S. marcescens.
Which keywords best characterize this research?
Key concepts include microwave-induced mutagenesis, athermal microwave effects, microbial metabolic engineering, lactic acid fermentation, and the production of bioactive bacterial pigments.
How is the "athermal" effect distinguished from thermal heating during experiments?
To distinguish between the two, the researchers utilized a specific experimental setup where vials containing inoculum were submerged in ice-filled beakers during microwave treatment to prevent temperature spikes, ensuring any observed changes were not due to heat.
What were the findings regarding the genetic stability of the mutated strains?
The study found that while microwave treatment could induce significant metabolic changes, these mutations were generally not fully stable over 10 generations, suggesting a tendency for the bacteria to revert or for the repair systems to eventually counteract the effect.
- Arbeit zitieren
- Assistant Professor Vijay Kothari (Autor:in), Haren Gosai (Autor:in), Shreya Raval (Autor:in), Vimla Chaudhary (Autor:in), 2014, Altered production of organic acid and pigments by microbes under influence of microwave radiation, München, GRIN Verlag, https://www.grin.com/document/286832
