Phenol Coefficient: Standard Test Organism
The phenol coefficient is a measure used to compare the effectiveness of an antiseptic or disinfectant against a specific microorganism relative to phenol.
This coefficient is determined using a standardized laboratory test, often referred to as the phenol coefficient test.
Selecting the Test Organism
Historically, the standard organism designated for determining the phenol coefficient of disinfectants is Salmonella typhi (now often classified as *Salmonella enterica* serovar Typhi). This bacterium was chosen due to its relevance to public health (causing typhoid fever) and its consistent response to phenolic compounds.
- Salmonella typhi: The established standard organism for the phenol coefficient test. Its challenge allows for the comparison of disinfectant potency against phenol.
- Escherichia coli: While a common indicator organism, it is not the primary standard for the phenol coefficient.
- Candida albicans: This is a yeast, not a bacterium, and is typically used in antifungal testing, not for determining the phenol coefficient.
- Bacillus psychrophilus: This bacterium is known for its ability to grow at low temperatures and is not the standard for phenol coefficient testing.
Therefore, Salmonella typhi is the correct organism used for this determination.
Important Questions from Methods in Microbiology
To determine the viable cell count of a bacterial culture, you have plated $50 \mu \text{L}$ of a 100-fold diluted sample of the culture on a nutrient agar plate and obtained 20 colonies after overnight incubation. The viable cell count of the culture is ______ $\text{CFU mL}^{-1}$. (answer in integer)
- Correctly match the following Bioinformatic tool/Database with its respective Utility.
Bioinformatic tool/Database Utility P. BLAST 1. Database for 3D protein structures Q. Bowtie 2. Tool to identify similarity of a query sequence to existing sequences available in databanks R. AlphaFold 3. Tool to align short read DNA sequences obtained from Next-generation sequencing to a reference genome S. PDB 4. AI tool to predict protein structures - Which one of the following programs is used for finding distantly related (or remote) protein homologs?
- Which one of the following is used for global alignment of two protein sequences?
- Which one of the following BLAST search programs is used to identify homologs of a genomic DNA query in a protein sequence database?
