Bacteria that are smallest in size are

Options

A. Bacilli
B. Cocci
C. Spirilla
D. Vibrios.

Answer

**Step-by-Step Solution:**

1. **Understand the Question**: The question asks for the smallest bacteria in terms of size. We need to identify which type of bacteria is the smallest.

2. **Know the Average Size of Bacteria**: The average size of bacteria typically ranges from 2 to 2.6 micrometers (µm) in length and 1.1 to 1.5 micrometers in width. This gives us a reference point for what is considered a standard size for bacteria.

3. **Identify the Smallest Bacteria**: The smallest known bacteria can be as small as 100 to 200 nanometers (nm), which converts to 0.1 to 0.2 micrometers (µm). This indicates that we are looking for a bacterium that falls within this size range.

4. **Determine the Specific Bacterium**: The bacterium known to be the smallest is *Dialister pneumosintes*, which has an approximate size of 0.15 micrometers (µm).

5. **Identify the Shape of the Bacterium**: *Dialister pneumosintes* is classified as a cocci, meaning it has a spherical shape.

6. **Evaluate the Options**: The options provided in the question likely include different shapes of bacteria (e.g., cocci, bacilli, spirilla, and vibrio). Since we have identified that the smallest bacterium is a cocci, we can conclude that this is the correct answer.

7. **Conclude the Answer**: Therefore, the bacteria that are smallest in size are classified as cocci, specifically *Dialister pneumosintes*.

**Final Answer**: The smallest bacteria are cocci, specifically *Dialister pneumosintes*.

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