Which of the following is considered as an ideal bacteriological indicator as acceptability aspect of water: March 2013 (d)
**Core Concept**
Coliform bacteria are commonly used as indicators of water quality due to their presence in the environment and their ability to contaminate water sources. They are a good marker of fecal contamination, which can indicate the presence of pathogens.
**Why the Correct Answer is Right**
* The correct answer is E. coli (Escherichia coli). It is an ideal bacteriological indicator of water quality because it is a gram-negative, rod-shaped bacterium that is commonly found in the intestines of humans and animals. E. coli is a reliable indicator of fecal contamination, which can be a sign of the presence of other pathogens. The presence of E. coli in water is a strong indication that the water has been contaminated with fecal matter, which can pose a health risk to consumers.
* E. coli is a member of the coliform group of bacteria, which are typically used as indicators of water quality. However, E. coli is a more specific and sensitive indicator than other coliform bacteria.
**Why Each Wrong Option is Incorrect**
**Option A:** Coliform bacteria, while useful as indicators of water quality, are not as specific as E. coli and can include non-fecal bacteria.
**Option B:** Staphylococcus aureus is a gram-positive bacterium that can be present in water, but it is not typically used as an indicator of water quality.
**Option C:** Salmonella is a pathogenic bacterium that can be present in contaminated water, but it is not used as an indicator of water quality due to its specific pathogenicity.
**Clinical Pearl / High-Yield Fact**
The presence of E. coli in water is a strong indication of fecal contamination, which can pose a health risk to consumers. The World Health Organization (WHO) recommends that drinking water should not contain more than 0-1 most probable number (MPN) of E. coli per 100 mL of water to ensure safe drinking water.
**Correct Answer: E. E. coli**