Q.Lactobacillus that sets milk into curd is categorised as: (A) Cyanobacteria (B) Archaebacteria (C) Chemosynthetic bacteria (D) Heterotrophic bacteria
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Start your 14-day free trial to unlock the full solution →Lactobacillus obtains its nutrients by breaking down organic compounds like lactose from milk, classifying it as a heterotrophic bacterium.
The question asks us to categorize Lactobacillus based on its mode of nutrition. To answer this, we need to understand how Lactobacillus obtains its energy and carbon, and then match that process to the given categories of bacteria.
Concept and Intuition
Organisms are broadly classified by how they obtain their food. This is called their mode of nutrition.
- Autotrophs ("self-feeders") produce their own food from inorganic sources. They can be:
- Photoautotrophs: Use light energy (e.g., plants, cyanobacteria).
- Chemoautotrophs (Chemosynthetic bacteria): Use chemical energy from oxidizing inorganic substances (e.g., nitrifying bacteria, sulfur bacteria).
- Heterotrophs ("other-feeders") obtain their food by consuming organic compounds produced by other organisms. They cannot synthesize their own food. This includes animals, fungi, and many types of bacteria.
Lactobacillus is a well-known bacterium responsible for converting milk into curd. This process involves the fermentation of lactose (milk sugar), which is an organic compound. The key insight here is that Lactobacillus consumes this pre-existing organic compound rather than producing its own food.
Step-by-step Explanation
- Identify the organism and its function: Lactobacillus is a genus of bacteria known for its role in lactic acid fermentation, particularly in the production of curd from milk.
- Understand the process of curdling: When Lactobacillus is introduced to milk, it metabolizes lactose (a disaccharide sugar present in milk). Through fermentation, it converts lactose into lactic acid. This lactic acid causes the milk proteins (casein) to coagulate, leading to the formation of curd.
- Analyze the nutritional source: In this process, Lactobacillus is utilizing lactose, an organic compound, as its primary source of energy and carbon. It does not perform photosynthesis (like cyanobacteria) nor does it oxidize inorganic chemicals to synthesize its own food (like chemosynthetic bacteria).
- Define heterotrophic nutrition: Heterotrophic organisms are those that cannot synthesize their own food and must obtain nutrients by consuming organic compounds from their environment. Since Lactobacillus breaks down lactose (an organic compound) for its survival and growth, it fits this definition.
- Evaluate the given options:
- (A) Cyanobacteria: These are photosynthetic autotrophs. They use sunlight to produce their own food. Lactobacillus does not perform photosynthesis. …
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