What is the most common form of bacterial cells?

Bacilli are indeed the most common form of bacterial cells, characterized by their rod-like shape. This morphology allows them to have a large surface area relative to volume, which can enhance nutrient absorption and facilitate growth. Bacilli can be found in various environments and are key contributors to various processes, including fermentation and the nitrogen cycle.

While the other shapes—cocci (spherical), spirilla (spiral), and vibrios (comma-shaped)—do exist and are important in different contexts, bacilli are more prevalent in general biological studies and applications. This may be due to the fact that many pathogenic and beneficial bacteria fall under this category, highlighting their significance in both microbiology and health. The prevalence of bacilli compared to the other forms underscores their role in both environmental ecosystems and human microbiomes.