Related Experiment Video
Updated: Jul 10, 2026
![Chemical-Induced Skin Carcinogenesis Model Using Dimethylbenz[a]Anthracene and 12-O-Tetradecanoyl Phorbol-13-Acetate (DMBA-TPA)](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60445.jpg&w=3840&q=50)
04:12
Chemical-Induced Skin Carcinogenesis Model Using Dimethylbenz[a]Anthracene and 12-O-Tetradecanoyl Phorbol-13-Acetate (DMBA-TPA)
Published on: December 19, 2019
Phenotypic persistence and external shielding ultraviolet radiation inactivation kinetic model
K G Pennell1, A I Aronson, E R Blatchley
1Division of Engineering, Brown University, Providence, RI, USA.
Journal of Applied Microbiology
|November 22, 2007
Summary
This study introduces a model for microbial inactivation by UV radiation, accounting for phenotypic persistence and shielding. The findings highlight the importance of these factors in UV disinfection efficacy.
Area of Science:
- Microbiology
- Environmental Engineering
- Photochemistry
Background:
- Microbial inactivation by ultraviolet (UV) radiation is crucial for disinfection.
- Observed 'tailing' in UV dose-response curves suggests complex inactivation mechanisms beyond simple exponential decay.
- Commonly cited reasons for tailing include physical shielding and microbial phenotypic persistence.
Purpose of the Study:
- To develop an inactivation kinetic model for microorganisms exhibiting UV dose-response tailing.
- To differentiate and quantify the contributions of physical shielding and phenotypic persistence to UV resistance.
- To provide a tool for accurate UV dose-response assessment in disinfection applications.
Main Methods:
- Developed and applied the Phenotypic Persistence and External Shielding (PPES) model.
- Fitted the PPES model to UV dose-response data for Escherichia coli, Mycobacterium terrae, and Bacillus subtilis spores.
- Evaluated particle shielding effects on UV sensitivity for M. terrae.
Main Results:
- The PPES model successfully described UV dose-response behavior, including tailing.
- Estimated fractions of persistent microorganisms were approximately 10(-7) for E. coli, 10(-5) for B. subtilis spores, and 10(-4) for M. terrae.
- Particle shielding further reduced UV sensitivity for M. terrae.
Conclusions:
- Phenotypic persistence is a significant factor contributing to UV resistance, even when shielding is minimized.
- The PPES model offers a mechanistically sound approach to estimate UV dose-response, including the tailing region.
- Accurate modeling of UV dose-response, particularly tailing, is essential for validating UV disinfection systems.
Related Concept Videos
01:35Mutations
Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
01:39Mutations
Overview
01:38Nucleotide Excision Repair
DNA Distortion and Damage
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
01:07Physiological Pharmacokinetic Models: Incorporating Hepatic Transporter-Mediated Clearance
Drug transporters are critical in drug absorption, distribution, and excretion processes. They should be included in physiological-based pharmacokinetic (PBPK) models, which help predict human drug disposition. However, predicting this is challenging during drug development, especially when liver transport is involved. However, with a realistic representation of body transport processes, an accurate model may be possible.
A recent model describes pravastatin's hepatobiliary excretion, mediated...
A recent model describes pravastatin's hepatobiliary excretion, mediated...
01:30Spontaneous and Induced Mutations
Spontaneous mutations arise infrequently during DNA replication due to errors in the process. A key factor behind these errors is tautomeric shifts in nitrogenous bases, where bases transition from keto to enol forms or amino to imino forms. This shift can alter base-pairing rules, leading to mutations. Additionally, reactive oxygen species (ROS) arising from aerobic metabolism can damage DNA, resulting in depurination (loss of a purine base) or depyrimidination (loss of a pyrimidine base).
01:19Pigmentation
The color of the skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. The melanin is transferred to the keratinocytes via melanosomes.
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...